More Related Content
Viewers also liked
Viewers also liked (19)
Similar to Powder to Profile
Similar to Powder to Profile (20)
Recently uploaded
Recently uploaded (20)
Powder to Profile
- 1. Powder to Profile JELD-WEN Extruder Technology
- 2. Objectives At the end of this module, you will be able to: Break the profile equipment into sections and define the function of each piece as the PVC Compound is transformed into a profile. Describe the status of the PVC Compound as it becomes a profile throughout the extrusion process.
- 3. Overview Powder to Profile Back Extruder Phase One PVC Melt Phase Two Rheology Die Calibrator Front Phase Three End Product Trouble Shooting Haul-off Visual Check Point – Trouble Shooting A B C D E
- 4. Phase One: Extruder & PVC Melt PVC Compound Converted Into Fused MassPVC Compound Converted Into Fused Mass Feeding Melting/ Degassing Metering/ Partial Fusing Final Fusing Feeding Melting/ Degassing Metering/ Partial Fusing Final Fusing CompressionCompression
- 5. Material Handling From Rail Car to Storage Silo From Storage Silo to Day Bin From Day Bin to Vacuum Receiver Hopper From the Vacuum Receiver Hopper, the compound filters into the Surge Hopper From the Surge Hopper, the compound is metered into the Extruder by the Gravimetrics hopper 11 22 33 44 55
- 6. Gravimetrics Gravimetric unit measures, records, and controls the consumption of material into the extruder process.
- 7. Gravimetrics Hopper Levels Shut-off Device Load Cell Stop Receiver Fork Weight Hopper Collector Funnel Impact Cone
- 8. Gravimetrics Reasons for Throughput Variation - High Bulk Weight - Good Flow properties - Low Bulk Weight - Poor Flow Properties
- 9. Gravimetrics Hopper Feeding the Screws Compound Constant material flow in the feeding area of the extruder Impact Cone
- 10. Gravimetrics Effect of Throughput Variation Weight Per Foot Weight Per Foot Haul-Off Speed Haul-Off Speed Wall Thickness Wall Thickness Throughput (Outlet) Throughput (Outlet) Screw Speed Screw Speed Throughput (Inlet) Throughput (Inlet) lb/ft ft/min in. lb/h RPM lb/h
- 11. Gravimetrics If Hopper Levels Drop lb/ft Ft/min In. Lb/h RPM Lb/h Weight Per Foot Weight Per Foot Haul-Off Speed Haul-Off Speed Wall Thickness Wall Thickness Throughput (Outlet) Throughput (Outlet) Screw Speed Screw Speed Throughput (Inlet) Throughput (Inlet)
- 12. Gravimetrics The compound is measured Released on top of the screws Heat & pressure push it through the extruder barrel. Doser in Feed ThroatDoser in Feed Throat
- 13. Review Question True or False Gravimetrics measures, records, and controls the consumption of material throughputs in the extruder process. True
- 14. Extruder: Barrel and Screws Through the Feed Throat, the compound falls onto a set of screws that turn inside a barrel. The compound is converted into a molten state with the addition of heat & pressure. Extruder Size: Barrel, Screws Dimensions, Number of Zones Our conical extruder of 63mm has 4 zones Our parallel extruder of 72 mm & 93mm have 5 zones
- 15. Phase One: Extruder & PVC Melt Barrel & Screw Zones Feeding Melting/ Degassing Metering/ Partial Fusing Final Fusing Feeding Melting/ Degassing Metering/ Partial Fusing Final Fusing Compression
- 16. Phase One: Extruder & PVC Melt Barrels and Heater Bands Barrel, Heater Bands, & Cooling Fans The barrel is divided into sections called zones Heater bands encircling the barrels define the zones Cooling fans
- 17. Review Questions Answer the following question. What is displayed in the picture below? Answer The picture displays an air cooled barrel system.
- 18. Extruder: Barrel & Screws Compression Feeding Melting/ Degassing Metering/ Partial Fusing Final Fusion
- 19. Barrel & Screws Parallel and Conical Parallel ScrewsParallel Screws Conical ScrewsConical Screws Barrel & Screws take the powder compound, heats and mixes it into a homogeneous melt, and pushes it through the die. Barrel & Screws take the powder compound, heats and mixes it into a homogeneous melt, and pushes it through the die.
- 20. Barrel and Screws Parallel Screws Molybdeum Coated ScrewsMolybdeum Coated Screws
- 21. Extruder: Barrel & Screws Conical Two Screws Nitrated steel-very hard Outlasts Screws’ Barrel May be Chromed
- 22. Phase One: Extruder & PVC Melt Cooling the Screw and Fused PVC It is important to cool the tip and body of the screws to prevent sticking of the fused PVC Compound
- 23. Phase One: Extruder & PVC Melt Barrel & Screw Zones Feeding Melting/ Degassing Metering/ Partial Fusing Final Fusing Feeding Melting/ Degassing Metering/ Partial Fusing Final Fusing CompressionCompression
- 24. Testing the Compound Rheology: Fusion Time & Torque for JW FormulationRheology: Fusion Time & Torque for JW Formulation
- 25. Phase One: Extruder & PVC Melt Feeding Zone & Powder PVC on the Screws Melting/ Degassing Metering/ Partial Fusing Final Fusing Melting/ Degassing Metering/ Partial Fusing Final Fusing FeedingFeeding Compression Compression
- 26. Phase One: Extruder & PVC Melts Gravimetrics, Feed Throat & Doser Remember The PVC Compound is vacuumed from the Daybin into the vacuum receiving hoppers The compound is gravity fed from the vacuum receiving hoppers into the gravimetric The gravimetric meters the virgin PVC, regrind & color concentrate into the Dosing Unit
- 27. Phase One: Extruder & PVC Melts Melting/ Partial Fusing Zone Feeding Feeding Degassing Metering/ Final Fusing Degassing Metering/ Final Fusing Compression Compression Melting/ Partial Fusing Melting/ Partial Fusing
- 28. Phase One: Extruder & PVC Melts In-between Zone 1 & 2 Melting/ Fusion Mechanisms Barrel Screw Solid Bed InterfacePushing Flight Melt Pool Melt FilmTrailing Edge Dissipative Melting of Solid Bed
- 29. Phase One: Extruder & PVC Melts In-between Zone 1 & 2 Melting/Fusion Mechanisms Barrel Screw Conductive Melting After Solid Bed Breakup
- 30. Phase One: Extruder & PVC Melt Compression Zone Feeding Melting/ Degassing Metering/ Partial Fusing Final Fusing Feeding Melting/ Degassing Metering/ Partial Fusing Final Fusing Compression
- 31. Phase One: Extruder & Raw Material Degassing Zone Feeding Melting/ Metering/ Partial Fusing Final Fusing Feeding Melting/ Metering/ Partial Fusing Final Fusing CompressionCompression DegassingDegassing
- 32. Phase One: Extruder & PVC Melt Vacuum Port or Visual Check Point Vacuum Port or Visual Check Point An area to view the compound as it is being pushed through the barrel by the screw
- 33. Phase One: Extruder & PVC Melt Metering/ Final Fusing Feeding Melting/ Degassing Partial Fusing Feeding Melting/ Degassing Partial Fusing Compression Compression Metering/ Final Fusing Metering/ Final Fusing
- 34. Phase One: Extruder & PVC Melt Summary BackBack Feeding Melting/ Degassing Metering/ Partial Fusing Final Fusing Feeding Melting/ Degassing Metering/ Partial Fusing Final Fusing CompressionCompression FrontFront
- 35. Review Question True or False The extruder combines PVC Compound with heat and pressure to fuse the material into a unified mass. TRUE
- 36. Phase Two: Rheology Die Calibrator Back Extruder Phase One PVC Melt Phase Two Rheology Phase Two Rheology Die Calibrator Front Phase Three End Product Trouble Shooting Haul-off Visual Check Point-Trouble Shooting A B C D E
- 37. Review Question Fill-in-the-Blank. Use 4 of the following words. Die, Shape, Calibrator, Water Tanks, Extruder The purpose the Rheology Phase is to ______ the molten mass from the _______ with the hot ___ and to cool and shape the profile with the ________. The purpose the Rheology Phase is to shape the molten mass from the extruder with the hot die and to cool and shape the profile with the calibrator.
- 38. Phase Two: Rheology The Adaptor & Y Block The Y-Block is attached to the extruder with an adaptor The die box is mounted either to the Y-Block or directly to the adaptor for single strand. Adaptor Y-Block End of Barrel Extruder Adaptor
- 39. Phase Two: Rheology The Adaptor & Y-Block The adaptor funnels the melt into the die or the Y-Block A Ring or Breaker Plate are used to align the Die Box or Y-Block to the adaptor & they also provide a sealing surface. The breaker plate provides a resistance of the flow from the extruder.
- 40. Phase Two: Rheology The Die The die box is attached to the extruder adaptor or directly to the Y-block. The die is made to slide into the die box. There is a clamping ring which holds the die into the die box.
- 41. Review Question Fill-in-the-Blank The die box or “Y” block is attached to the extruder with an ____________. The die box or “Y” block is attached to the extruder with an adaptor.
- 42. Phase Two: Rheology The Die The die shapes the PVC melt from the extruder into the desired shape
- 43. Review Question Fill-in-the Blank The purpose of the die is to _______ the _______ or extrudate from the extruder into the desired shape. The purpose of the die is to shape the PVC Melt or extrudate from the extruder into the desired shape.
- 44. Phase Two: JELD-WEN Die Parts Distance Distribution Mandrel Plate Entry Side Torpedo Mandrel Plate Exit Side Mandrel Compression #2 Outlet #1 Outlet Mandrel Top
- 45. Review Question Fill-in-the Blank The die contains the following plates: Distance Distribution Torpedo and __________ ______________ #2 and #1 Outlet and Mandrel Top The die contains the following plates: • Distance • Distribution • Torpedo and Mandrel • Compression • #2 and #1 Outlet and Mandrel Top
- 46. Phase Two: Rheology Melt Rheology The extruder fuses the material into a unified mass, called PVC melt and is exerting pressure to move it forward Flow is how the PVC melt moves forward from the extruder through the die
- 47. Review Question Fill-in-the Blank The extruder fuses the PVC Compound into a unified mass called _______ and exerts pressure to move it forward. The extruder fuses the PVC Compound into a unified mass called PVC Melt and exerts pressure to move it forward.
- 48. Phase Two: Rheology Science of Flow Basic Measurements Shear Stress Shear Rate Melt Temperature Melt Viscosity Is this a good melt?
- 49. Phase Two: Rheology Stress, Rate, Temperature & Viscosity Shear Stress = Melt Pressure Viscosity Temperature 380º F Temperature 360º F Shear Rate = Screw RPM Higher Stress + Shear Rate = More Melt Flow, Plasticity, or Viscosity
- 50. Review Question Fill-in-the Blank Higher Shear Stress plus Shear Rate = More Melt Flow, Plasticity or ______________ Higher Shear Stress plus Shear Rate = More Melt Flow, Plasticity or Viscosity
- 51. Phase Two: Rheology Laminar Flow: Static Wormy Polymer Chains O PSI Melt Temperature 385º F Polymer chains are in static form-worm like 0 Flow Die Opening
- 52. Review Question Fill-in-the Blank Shear stress is another word for melt _____.Shear stress is another word for melt pressure.
- 53. Phase Two: Rheology Laminar Flow: Activation Energy Low to Medium PSI Activation Energy Melt Temperature 385º F Polymer Chains Stretching to Form Layers 0 Flow Die Opening
- 54. Review Question Fill-in-the Blank Shear _____ refers to Screw RPM.Shear Rate refers to Screw RPM.
- 55. Phase Two: Rheology Laminar Flow Achievement Medium to High PSI Melt Temperature 385º F Exceed activation energy polymer layers slide by each other Flow
- 56. Review Question Fill-in-the Blank Melt viscosity refers to the ________ of the PVC Melt exiting the die. Melt viscosity refers to the stiffness of the PVC Melt exiting the die.
- 57. Review Question Fill-in-the Blank The molten plastic mass that has no Shear Stress or Shear Rate will not ______. The molten plastic mass that has no Shear Stress or Shear Rate will not flow.
- 58. Phase Two: Rheology Laminar Flow: Melt Fracture Increase in shear rate and/or shear stress beyond quality limits adversely effects the melt and the end product
- 59. Review Question True or False By decreasing shear stress and the raising of shear rate, the higher your viscosity of melt through the die. FALSE The higher the pressure (Shear Stress) and the higher the screw RPM (Shear Rate), the higher your viscosity or flow of your melt.
- 60. Phase Two: Rheology Die Swell Die Extruder
- 61. Review Question Fill-in-the Blank Shear Stress is the amount of energy that is being applied to the melt. Shear Stress refers to the __________ behind the die. This pressure is being generated by the __________. Shear Stress is the amount of energy that is being applied to the melt. Shear Stress refers to the melt pressure behind the die. This pressure is being generated by the extruder.
- 62. Phase Two: Rheology Correct Flow Properties Flow Challenges Poor Surface, too dull or too shiny Pock marks Lumps Internal walls separating Wavy edges Loss of definition on edges Erratic flow may cause jam ups Excessive die or calibration fouling Wall Thickness
- 63. Review Question Fill-in-the Blank Examples of flow challenges are: Poor surface-too dull or too shiny _____________ Lumps Internal walls separating ______________ Loss of definition on edges Erratic flow and jam ups Examples of flow challenges are: • Poor surface-too dull or too shiny • Pock Marks • Lumps • Internal walls separating • Wavy Edges • Loss of definition on edges • Erratic flow and jam ups
- 64. Phase Two: Rheology Calibration & Water Cooling First Calibrator Die Blue Hoses Cool Water Red Hoses Warm Water White Hoses Vacuum
- 65. Phase Two: Rheology #1 Calibrator Cooling Die Swell Cool Water In Vacuum Vacuum Slots & Hoses Warm Water Out Dark Area Cooler: 125 F – 135 F Light Area Hotter: 250º F – 350º F Calibrator
- 66. Review Question Fill-in-the Blank When flow occurs in the die, it will flow the fastest in the ______ of the flow and the ________ at the wall of the flow. When flow occurs in the die, it will flow the fastest in the center of the flow and s l o w e s t at the wall of the flow.
- 67. Phase Two: Rheology Water Tank Calibrators Water Tank Calibrators Series of water tanks Sizing elements Vacuum Long Numerous elements
- 68. Review Questions Work in teams and answer the following questions. The instructor will assign questions for you to answer. Use your books to find the answers. Review as a group.
- 69. Review Question Fill-in-the Blank The die takes the PVC Melt and refines the shape into a _______ using pressure. The calibrator continues to refine the profile by _____ it using water and a vacuum. The die takes the PVC Melt and refines the shape into a profile using pressure. The calibrator continues to refine the profile by cooling it using water and a vacuum.
- 70. Review Question Fill-in-the Blank Shear Rate is the _____ at which Shear Stress (or energy) is being applied behind the die. To measure Shear Rate, use RPM of the extruder screw. Shear Rate is the speed at which Shear Stress (or energy) is being applied behind the die. To measure Shear Rate, use RPM of the extruder screw.
- 71. Review Question True or False The molecules in a molten plastic mass that have flow, will have no organization and look like a cluttered mess of strings. FALSE Molecules in a molten plastic mass with NO FLOW will have no organization and look like a cluttered mess of strings. Molecules WITH FLOW have organization and are stretched to form layers.
- 72. Review Question True or False As the melt is forced to flow through the die, the polymer strings do not stretch and remain disorganized. When the melt exits the die, the pressure is released and the polymer strings will recoil back. This is known as die swell. This is a know % for each type of compound, for PVC window profiles it is 2 – 8%. False As the melt is forced to flow through the die, the polymer strings do stretch.
- 73. Review Question Fill-in-the Blank When Shear Stress and Shear Rate are applied, the unorganized polymer molecules begin to shift into organized layers and are stretched. The amount of energy to make this happen is called, ___________ ___________. When Shear Stress and Shear Rate are applied to a PVC Melt, the unorganized polymer molecules begin to shift into organized layers and are stretched. The amount of energy to make this happen is called, Activation Energy.
- 74. Review Question Fill-in-the Blank Flow is achieve by exceeding ______ Energy, forcing the polymer molecules to slide by each other. The polymer layers slide the slowest at the ____ of the die and the fastest in the _________ of the flow. Flow is achieve by exceeding Activation Energy, forcing the polymer molecules to slide by each other. The polymer layers slide the slowest at the wall of the die and the fastest in the middle of the flow.
- 75. Review Question True or False If the Shear Rate and/or Shear Stress is increased beyond certain limits, the PVC Melt exiting the die can be adversely affected. Initially, one may see irregularities like pock marks and tear drop shaped lumps in the surface. TRUE
- 76. Review Question True or False If the limits of Shear Rate and/or Shear Stress are increased too far, the strings of material that are stretched may break and melt fracture may occur. True
- 77. Review Question True or False To get the correct flow properties there must be a balance of Shear Rate, Shear Stress, and Melt Temperature. If these are not correct, flow problems will occur. True
- 78. Review Question True or False The temperature of the PVC Compound exiting the adaptor is melt temperature. This is monitored through the Operator’s Panel. TRUE
- 79. Phase Three: End Product & Haul-off Station Back Extruder Phase One PVC Melt Phase Two Rheology Die Calibrator Front Phase Three Haul-Off End Product Haul-Off Visual Check Points- Trouble Shooting A B C D E Visual Check Points- Trouble Shooting A B C D E
- 80. Downstream Ancillary Equipment Air Showers Blow excess moisture off the profile as it moves out of the water tanks Bow Heaters Heaters positioned on any side of a profile to correct bow created during the cooling process Weather Strip Inserts the pile weather strip Nail Fin Pinch Punches holes in nail fin of frames
- 81. Downstream Haul-Off Station The Haul-Off Station pulls the profile through the calibrator, cuts the cooled profile to size, and releases it to a tilt table for packaging.
- 82. Downstream Haul-Off Haul-Off Pulls the profile through the calibration system at a precise rate of speed. Pads
- 83. Downstream Haul-off Station - Guillotine Guillotine Cuts the profile to length
- 84. Phase Three: End Product Pulled by the Haul-off Haul – Off Station Pulls profile through the calibration process Guillotine cuts profile to length Moves the profile to a tilt table for storage collection Final Visual Check Point for Quality & Trouble Shooting
- 85. Trouble Shooting 5 Visual Check Points On-the-Floor Back Extruder Phase One PVC Melt Phase Two Rheology Die Calibrator Front Phase Three End Product Haul-off Visual Check Points- Trouble Shooting A B C D E Visual Check Points- Trouble Shooting A B C D E
- 86. Trouble Shooting Visual Check Point: Feed Port & Control Panel Back Extruder Phase One PVC Melt Visual Check Point A Feed Port & Control Panel
- 87. Trouble Shooting Visual Check Point: Vacuum Port Visual Check Point B Vacuum Port Visual Check Point B Vacuum Port Look for Crumbly Belt or Strip with broken edges Back Extruder Phase One PVC Melt
- 88. Trouble Shooting Visual Check Point: Melt Exiting Die to Calibrator Phase Two Rheology Phase Two Rheology Die Calibrator Visual Check Point C Melt Exiting Die Entering the Calibrator Visual Check Point C Melt Exiting Die Entering the Calibrator Melt, Die & Calibrator
- 89. Trouble Shooting Visual Check Point: Extrusion Exiting Water Tanks Phase Two Rheology Phase Two Rheology Die Calibrator Visual Check Point D Extrusion Exiting Water Tanks Visual Check Point D Extrusion Exiting Water Tanks
- 90. Trouble Shooting Visual Check Point: Haul-Off Table Front Phase Three End Product Haul-off Station Visual Check Point E Haul-Off Table Visual Check Point E Haul-Off Table
- 91. Trouble Shooting Visual Check Point: Guillotine Front Phase Three Haul-Off End Product Haul-off Visual Check Point E Haul-Off Table Visual Check Point E Haul-Off Table
Editor's Notes
- Instructor Notes Review Version: March 5, 2008 Lynn’s > Vinyl > Current > VNL_PWDR_PRFL_IG
- Instructor Note Make sure to conduct a review of the Extruder Equipment and The Science of Plastic using the Review module. Then begin this session.
- Overview: Powder to Profile There are three basic phases with several visual check points. Phase One: Extruder & PVC Melt Phase One focuses on the PVC powdered compound being sent to the extruder from the day bin and being converted into a melt. The extruder utilizes heat and compression (pressure) to convert the PVC Compound into a melt. This melt is forced through a die to create a profile. Phase Two: Die, Calibrator, & RheologyPhase Two focuses on taking the melt and shaping it into a specific profile through the die and calibrator. During this phase the melt from the extruder is forced through a hot die to shape a profile. It is then pulled through cooling calibrators to complete the shaping requirements of the profile. Phase Three: Haul-Off & End Product Phase Three focuses on pulling the profile, cutting the profile to length, and moving the finished profile into a storage area for shipping. All Phases: Trouble Shooting Trouble Shooting is an on-going process. There are Visual Check Points throughout the Powder to Profile process that assist in maintaining the quality of the PVC Compound as it is turned into a profile. A fundamental description of what to look for at each check point will support your efforts to create a quality profile. Instructor Note The slide will not be highlighted as you overview the processes. When you are ready to start Phase One, press the arrow button to highlight Phase One and to start the explanation of Phase One …which starts on the next page.
- Overview of Phase One: PVC Melt into Fused Mass The extrusion process actually starts with the PVC Compound being sent from the day bin to the hopper and then being measured and dropped on the screws in the extruder. Once the PVC Compound is on the screws, the beginning of the conversion of powder PVC into a fused mass begins. Once the PVC Melt is prepared in the extruder, it is forced through a die to obtain the desired shape. The powder to melt conversion process happens inside the extruder barrel. The mechanical actions of the screw, combined with the external heat and cooling from the barrel, provides the energy for the process. Measuring and controlling how the PVC Compound is released on the screws is gravimetrics. Instructor Note Let’s take a look at the material handling of the PVC Compound.
- The PVC Compound Starts in the Rail Car and Ends up in the Gravimentrics Hopper From the Rail Car the compound is vacuumed into an outdoor Storage Silo. From the Storage Silo it is vacuumed into an indoor storage silo, a Day Bin. From the Day Bin it is sent to the Vacuum Receiver Hopper. The vacuum receiver hopper is located above the mezzanine. Any hopper above the mezzanine level is a vacuum receiver hopper. From the Vacuum Receiver Hopper it goes to the Surge Hopper, which is a hopper below the mezzanine. Any hopper below the mezzanine level is a surge hopper. From the Surge Hopper, the compound is metered and dropped into the extruder through a Gravimetric Hopper. Instructor Note Transition to Gravimetrics Explanation
- Gravimetrics Measures and records the consumption of raw material throughputs in the extrusion process. Controls the feeder speed (doser) to provide a constant weight per hour, depending on the profile specification. Provides the highest level of control of the PVC compound, regrind, and pigment fed to the extruder Why Gravimetrics? Stabilizes the extrusion process by helping to reduce: Line surges Line jamb ups Scrap Documents production data like: Weight/Hour Operation Statistics
- Gravimetrics - Hopper Levels A special designed scoop valve opens to allow material to fill the hopper and then closes. The hopper is suspended from a special designed load cell fork, which allows the funnel to pivot for accurate measurement. The control is calibrated to know the empty weight and volume of the hopper funnel, and is able to compute the bulk density.
- Gravimetrics The above diagram displays variance in the bulk density of the compound in the hopper. Bulk density effects the melt flow. Gravimetrics Uses a continuous weight process that measures and controls materials ranging from ½ lbs. to 4500 lbs. per hour. Is capable of dosing multiple side components depending on the specific application. Suitable for virgin, regrind, and pellets. As the bulk density changes within the incoming PVC Compound, the Gravimetrics will compensate for this variance (in bulk density) to help produce a quality melt in the extruder as well as in the finished product.
- Hopper Levels A specialty mounted sensor counts the exact screw RPM and the position of the screw, so the material being weighed is measured at the same screw position. The control displays this feed rate and RPM. Additional encoders record and enable the display of the line speed. Special components interface with existing equipment to control RPM of the doser feeder. If the hopper level drops to a point below 20% or if the control cannot maintain set point, an alarm will indicate a problem to the operator. The weigh hopper refills to the full limit and process repeats.
- Gravimetrics-Effect of Throughput Variation With variations in the bulk density and no compensation, there will be variations in the throughput of the extruder resulting in variations within the final extrusion. This will produce a lower quality product.
- Hopper Levels With the weigh hopper constantly calculating throughput of the compound, variations in the bulk density will be compensated in the doser feeder. This will make for very consistent throughput of the extruder creating a very stable product.
- Gravimetrics Gravimetrics make it possible to measure and control the compound, regrind, and pigment being released on top of the screws from the hopper. The weighing and dosing of the compound to the screws is monitored and controlled from the Extruder Control Panel, which interfaces with the gravimetric technology.
- Barrel and Screws At this point, the doser moves the material into the feed throat and onto the screws. In the barrel and screws, the PVC Compound is converted into a molten state through the addition of heat and pressure. This entire process is monitored through the Operator Control Panel. The screws push the powder compound through the barrel. The barrel is divided into areas known as zones. For each zone there is a thermocouple, heater band, and some have cooling fans. The size of the extruder is expressed as the inside diameter of the barrel in mm. The diameters for the conical or parallel extruders will range from 25mm to 140mm. The conical design is usually limited to about 75mm. Instructor Note Transition: Now that the PVC Compound has been received at the plant and has been piped from the storage bin into the extruder, the compound is pushed through the barrel with screws. Explain the barrel zones and the relationship to the screws.
- Phase One: Barrel and Screw Zones From an operational point of view, the Barrel Zones are the most recognized as they are visible and are used to set the temperatures for the extrusion process. The bulk density of PVC powder is used to calculate the design of the feed section of the screws and only PVC Melts of similar bulk densities will process well. It is possible to add a percentage of flake regrind to the PVC powder if the percentage does not exceed 20%.
- Phase One: Barrel and Heater Bands The barrel and screws are a set and function as a unit. The external part is the barrel with the screws located within. The barrel is divided into sections called “zones” which are defined by the encircling heater bands. Also located in association with the heater bands is a thermal couple and cooling fans- (Not found on the first zone, and in some cases cooling is not found in the second zone.). The number of zones is dependent on the length of the extruder’s barrel. The 63mm CET Extruder has 4 barrel zones. The 72mm and 93mm Extruders have 5 barrel zones. Instructor Note JELD-WEN will have all of these extruders in Yakima, WA in 2008. This may change in the future.
- Barrel and Screws The size of the screw also plays a part in the size of an extruder. The L/D ratio for screws is the length of the screws divided by the diameters; usually expressed as 28:1. This means the screw is 28 diameters long. The L/D ratios are as low as 12 and as high as 42. The typical L/D ratios are 20, 24 for conical and 26 to 32 for parallels. Flow of Melt through the Barrel and Screws Notice the shape of the screws and the sections of the barrel. In general, from left to right,consider the following flow: PVC Compound falls on the screws from the doser and feed throat Notice how the screws change shape. This changes the pressure added to the powder compound. Heat is added as it is pushed through the barrel. The compound is partially melted, compressed, degassed, metered, and finally fused by the various screw sections. At the end of the barrel and screw section, the fused compound is ready to be pushed through the die that shapes the window profile. The status of the compound being pushed through the barrel by the screws can be checked on through vacuum ports. All pressure, heating/cooling, melting, metering of compound, melt pressure, melt temperature is monitored through the Operator Control Panel.
- Barrel and Screws: Parallel and Conical There are two kinds of extruder screws: Parallel and Conical. Parallel Screws Parallel screws are 2 screws that work together to produce molten compound. Conical Screws Conical screws are cone shaped and work together to produce molten compound. This slide displays parallel barrel and screws which have a sealed internal coolant. JELD-WEN has the 72mm and 93mm machines which have both of these features. Instructor Note Transition: Now that the PVC Compound has been received at the plant and has been piped from the storage bin into the extruder, the compound is pushed through the barrel with screws. Explain the barrel zones and the relationship to the screws. The alternate to this system is EXTERNAL SCREW COOLANT. The external screw coolant has an external pump and reservoir located under the barrel and plumbing that circulates heat transfer liquid internally to the tips of the screws. The temperature of the circulating liquid is controlled at the control panel. This is considered to be a better system by many but it also requires a lot more maintenance attention. Point out what JELD-WEN has.
- Parallel Screws The screws of all twin screw extruders by CET are coated with molybdenum (Mo) on the running surfaces. They are very resistant to the operational stress during extrusion. This coating is particularly resistant to abrasion and has excellent gliding characteristics thus enhancing substantially the screw and barrel lifetime. The molybdenum is applied at CET according to a special flame-spray method which provides the optimum Mo-oxide content for best gliding characteristics. The Mo-coating remains slightly brittle. Therefore, it subsequently has to be ”sealed” once the screws are finished. The pores are closed with an artificial resin of very low viscosity and of high creeping quality, which then hardens. The coating thus becomes on the one side more impact-resistant and on the other hand no corrosive steams in the melt attack the screw base material with the effect of removing the coating. Advantages Larger cylinder surface for input of hearting energy Gentle plasticizing supported by long processing units and enough surface for preheating Constant screw speed for each zone High output rates at low screw speed Cost advantage at high output rates
- Extruder Barrel and Screws: Conical and Parallel Conical The barrel for the CONICAL extruders are made of a special steel that is NITRATED. It produces very hard surfaces. The barrel is usually much harder than the screws. This is done so only one component will wear faster. The barrel, if not damaged, could out last the screws 2 to 1. Advantages Wide processing window (high flexibility) Cost advantage at small frame sizes Large center distance of gear shafts Torque not limited by screw shafts High intake volume Disproportionate energy input between intake and compression zone due to higher circumferential speed Low screw speed due to low circumferential speed at the output zone Easy going screw change Smallest foot-print
- Phase One: Cooling the Screws and Fused PVC It is important that the screws to be cooler than the barrel and not allow the PVC to stick during the extrusion process. This is accomplished by internally cooled the screws. Distilled water is sealed inside the screws along with a spiral spring device. As the screws rotate the cooler water in the back of the screws (as shown in BLUE in the picture above) is propelled forward in the screws by the spring device. As the water moves toward the front sections of the screws (as shown in RED in the above picture), it removes heat from the screws. When the water reaches the tips of the screws, it will have acquired enough heat from the screws to turn into steam. This action cools the front sections of the screws. The steam is propelled toward the back of the screws and in doing so will lose some of its heat approximately mid way of the screws. The lose of this heat will heat the back sections so the screws condensing the steam back into water. This cycle will keep repeating as long as the screws keep rotating. This results the heating of the back screw areas and the cooling of the front areas of the screws, including the screw tips. This is a very efficient method to cool the screw while being almost maintenance free.
- Phase One: Barrel & Screw Zones The screws are located inside the barrel. And like the barrel, the screws have zones. The exact location of the zones may vary but the fundamental sections are: Feeding Melting/ Partial Fusing Compression Degassing Metering/ Final Fusing The above diagram displays a 5 zone extruder. The diagram below displays a 4 zone extruder.
- Phase One: Extruder & PVC Melts Overview: Screw Zones Term Definition Feed Zone The Feed Zone conveys the raw PVC powder from the feed section into the barrels where it is heated via heater bands of the barrels and compressed via the flights of the screws. As a result of the heat on the raw PVC, it begins to swell, increasing the pressure. The heat and the increased pressure cause the powder to start to stick together and to become less of a powder. Corresponds to Barrel Zone 1. Melting/ Partial Fusing Zone The Fusing Zone is a transition zone where the PVC raw material is moved further into the barrels and heat is applied. This zone is often called the Melting/ Partial Fusing Zone but the PVC does not truly melt. This zone is where the PVC gains most of the external heat. The screw flights are designed to expose the PVC to the barrel’s internal surface to absorb the heat and to mix the PVC to assure uniform hearing. This prepares the PVC for the Compression Zone. There is no clear definition between these zones but a transition of blending. It is often difficult to tell when one ends and another begins. Corresponds to Barrel Zones 1 & 2. Compression Zone The Compression Zone is where most of the fusion occurs. The screw flights are altered in the their design to provide the amount of compression to the PVC so it is touching the surface of the barrel where it is heated. At this spot the actual fusion occurs. The trailing flight of the screws scrapes the fused PVC and is pooled down toward the root diameter of the screws. This process is repeated throughout the entire section of the Compression Zone. By controlling the amount of external heat that is applied, the degree of fusion can be controlled. This is very important as the condition of fused PVC needs to have the correct degree of fusion for the next zone so the degassing can occur. Corresponds to Barrel Zone 3. Degassing The Degassing Zone is the section of the screw where the flights are altered so the pressure from the Compression Zone is eliminated. This allows the fused PVC to relax. At this point, a vacuum is applied that will draw off any moisture or volatile materials. These materials if not removed can result in poor impact properties of the finished profile. Metering Zone/ Final Fusing The Metering Zone conveys the fused and degassed PVC from the Degassing Zone to the exit of the extruder. Heat is also applied. The screw flights are designed to provide mixing of fused PVC. This results in a homogeneous fused PVC to be pumped to the exit of the extruder. At this point, it is forced through a die. Depending on the Extruder, corresponds to Barrel Zones 4 for the 63mm and Barrel Zone 5 for the 72mm & 93mm.
- Page 24a Insert Instructor Guide This slide is also displayed in the Science of Plastic when explaining tests. Explain Here is demonstrates the flow of material through the extrusion process. Above Example: Torque Rheometer Test This is not in the Participant Guide in this module, Powder to Profile. Page 59 in the Instructor Guide for the Science of Plastics includes the explanation below: The Torque Rheometer Test is used by JELD-WEN to screen incoming lots of material. Precisely measured samples of compound are run through the Rheometer, at a set temperature and RPM Rate. The test generates the curve shown in the above diagram, where key outputs can be identified: Fusion Torque The torque required to turn the Rheometer screws, as the compound fuses (the top of the curve in the “Adapter and Y-block” sections. Fusion TimeThe time at which fusion torque is reached. Melt Torque The torque level, after fusion torque, then the compound is in a molten state and the curve is flat. Stability Time The time on the graph, after melt torque is achieved, where the torque curve begins to bend upwards as torque increases. These key outputs will help to identify whether a batch of compound has all key ingredients mixed correctly. It also helps to measure whether the compound has settled during transit.
- Phase One: Feeding Zone and Powder PVC on the Screws Powder PVC is conveyed into the Barrel Zone 1 where external heat is applied from the heater band. This is a heat only zone. There are no cooling fans. The primary function of the Feed Zone section of the screw is to convey the PVC powder into the barrel and initiate heat and low compression. The compression is needed to expose the PVC to the internal surface of the barrel so it can be heated and to provide friction to assure smooth conveying.
- Phase One: Processing Feed Throat and Doser Let’s explain the changes of the PVC powder through the extruder by following the screw flight. Powder to Melt The control of the feeding of the powder PVC into the feed section of the extruder is done by a doser feeder. The doser feeder meters the PVC Melt into the feed port of the extruder. In the feed port section, the powder PVC falls onto the feed section of the screws. Given the new design of the extruders, it is necessary to have the screws covered by about 4 – 6 inches of powder. The screw flights at this zone are designed to accept the powder PVC and convey it into the barrel of the extruder. The bulk density of the PVC powder is used to calculate the design of the feed section of the screws. It is possible to add a percentage of flake regrind to the PVC powder if the percentage does not exceed 20%. The feed throat of the extruder is not heated and has a water jacket around the feed throat if cooling is required.
- Phase One: From Feeding to Melting/Fusion The PVC is conveyed into the Melting or Partial Fusion Zone. Here, the PVC is exposed to additional heat, mixed, and compression applied. The first signs of fusion or melt are displayed in the Melting/ Partial Fusing Zone. Barrel Zone 2 correlates to this screw zone. It provides the heat required but also cooling fans if the process over heats. (Zone 2 for the 63mm. Zone 3 for the 72mm & 93mm.)
- Phase One: Melting/Fusion Mechanism This process is evident at the end of Zone 1 & the beginning of Zone 2. PVC is pressed to the internal surface of the barrel where it is heated. A film of fused PVC is created. The trailing edge of the next flight now scrapes this film and moves it toward the root diameter of the screw. As this process continues, a pool of fused material forms at the trailing flight. Continue explanation to diagram on next page Instructor Notes Define: Solid Bed Interface
- Melting/Fusion Mechanism The previous page shows how the compound is fused at the barrel and then scraped by the trailing screw flights. This creates a melt pool and a solid bed interface. The flights from the opposite screw will divide these into halves and as the screws rotate, the process is on- going. The above diagram displays the effect of the fusing, halving a fusing cycle. This is the condition of the melt at the vacuum port. The condition of the melt exiting the barrel will be almost 100% melt. Notes
- Phase One: Compression Zone This mass now enters the Compression Zone where higher level of pressure is generated by the design of the screw. Although this is a short area of the screw, the amount of processing at this point is at it’s highest. The PVC Melt is continuously exposed to the internal surface of the barrel, heated, and scraped by the trailing screw flight. The result of all the accumulated heating and shearing will be a fused PVC Melt to the degree needed for the next section of the screw. The Barrel Zone 3 corresponds to the Compression Zone of the screw.
- Phase One: Degassing Zone The partially fused PVC now exits the Compression Zone and enters the Degassing Zone where there is low pressure. Low pressure allows the PVC Melt to relax or swell. At this time a vacuum is applied to remove any moisture and/or volatile materials. It is important for the PVC to be processed to the correct condition, i.e. crumbly belt. The correct condition should look like a dry belt that will break or crumble as the screws turns. If the material is under processed, the volatiles cannot be removed. If the material is over processed, the volatiles can be sealed inside the material and cannot be removed.
- Phase One: Barrel and Screw Visual Check Point The barrel has a vacuum port. It is located ¾ down the barrel from the feed input section. Through the feed input area, an operator can view the status of the compound being pushed through the barrels by the screw.
- Phase One: Metering/ Final Fusing The next zone of the screws is the Metering Zone. The Metering Zone is designed to heat and cool in order to maintain a constant temperature of the melt. Barrel Zones for Extruders Barrel Zone 4: 63 mm Extruder Barrel Zone 5: 72mm and 93mm Extruders The PVC in the Metering Zone is heated again and mixed for consistency. There is a mid-level of compression to assure the proper surface contact with the internal surface of the barrel. Mid-level compression also provides for a constant flow of material so a reservoir of material is built behind the die.
- Phase One: Extruder Summary The extruder is broken down in zones. These zones correspond to the screw function within each barrel zone. The zones of the extruder include the following: Feeding Melting/ Partial Fusing Compression Degassing Metering/ Final Fusing The back of the extruder is the Feed Zone. Each section of the extruder prepares the PVC Compound for the next extruder zone. Note It is often analogized that the extruder is two extruders in one. The first being from the Feed Port to the vacuum port, where the PVC compound is fused and degassed. The second from the vacuum port to the extruder exit, where the fused PVC is heated uniformly and metered to the reservoir behind the die at a constant volume and pressure.
- Summary of Phase One: Extruder and PVC Melt 1. True or False? The current technology uses screw tips that are cooled with distilled water inside the screw. It is important to cool the screw tip and body to prevent the sticking of the fused PVC. This is accomplished with the use of distilled water and a spring like coil located inside the screw. True 2. Describe the process to cool the tip and body of the screw. As the tip of the screw turns, it is cooled by the cool water. The water turns into steam as it cools the tip of the screw. A coil inside the screw, conveys the steam toward the back of the screw. The steam condenses back into water. The same coil conveys it to the tips of the screws again and starts the process all over. 3. True or False The control of the feeding of the PVC Compound into the feed section of the extruder is through the doser feeder. True 4. Describe the process of the PVC Compound being feed into the doser feeder. What does the doser feeder do? The control of the feeding of the powder PVC into the feed section of the extruder is done by a doser feeder. The doser feeder meters the PVC Melt into the feed port of the extruder. In the feed port section, the powder PVC falls onto the feed section of the screws. Given the new design of the extruders, it is necessary to have the screws covered by about 4 – 6 inches of powder. The screw flights at this zone are designed to accept the powder PVC and convey it into the barrel of the extruder. The feed throat of the extruder is not heated and has a water jacket around the feed throat if cooling is required. 5. Describe the function of each screw zone and associated barrel(s) zone. Feed Zone Melting/ Partial Fusing Zone Compression Zone Degassing Zone Metering Zone/ Final Fusing Answers on next page
- Phase One: Extruder & PVC Melts PVC Compound into a Fused Mass Screw Zones Term Definition Feed Zone The Feed Zone conveys the raw PVC powder from the feed section into the barrels where it is heated via heater bands of the barrels and compressed via the flights of the screws. As a result of the heat on the raw PVC, it begins to swell, increasing the pressure. The heat and the increased pressure cause the powder to start to stick together and to become less of a powder. Corresponds to Bareel Zone 1. Melting/ Partial Fusing Zone The Fusing Zone is a transition zone where the PVC raw material is moved further into the barrels and heat is applied. This zone is often called the Melting/ Partial Fusing Zone but the PVC does not truly melt. This zone is where the PVC gains most of the external heat. The screw flights are designed to expose the PVC to the barrel’s internal surface to absorb the heat and to mix the PVC to assure uniform hearing. This prepares the PVC for the Compression Zone. There is no clear definition between these zones but a transition of blending. It is often difficult to tell when one ends and another begins. Corresponds to Barrel Zone 3. Compression Zone The Compression Zone is where most of the fusion occurs. The screw flights are altered in the their design to provide the amount of compression to the PVC so it is touching the surface of the barrel where it is heated. At this spot the actual fusion occurs. The trailing flight of the screws scrapes the fused PVC and is pooled down toward the root diameter of the screws. This process is repeated throughout the entire section of the Compression Zone. By controlling the amount of external heat that is applied, the degree of fusion can be controlled. This is very important as the condition of fused PVC needs to have the correct degree of fusion for the next zone so the degassing can occur. Corresponds to Barrel Zone 3. Degassing The Degassing Zone is the section of the screw where the flights are altered so the pressure from the Compression Zone is eliminated. This allows the fused PVC to relax. At this point, a vacuum is applied that will draw off any moisture or volatile materials. These materials if not removed can result in poor impact properties of the finished profile. Metering Zone/ Final Fusing The Metering Zone conveys the fused and degassed PVC from the Degassing Zone to the exit of the extruder. Heat is also applied. The screw flights are designed to provide mixing of fused PVC. This results in a homogeneous fused PVC to be pumped to the exit of the extruder. At this point, it is forced through a die. Depending on the Extruder, this phase corresponds to Barrel Zones 4 for the 63 mm and Barrel Zone 5 for the 72mm & 932mm.
- Phase Two: Rheology Die to Calibrator The purpose of the Rheology Phase is to shape the molten mass from the extruder with the hot die and to cool and size the molten shape with the calibrator.
- Notes
- Phase Two: Adaptor & Y-Block The Y-Block is attached to the extruder with an adaptor. The Die Box is mounted either to the Y-Block for running dual strand or directly to the extruder adaptor for running single strand. The Adaptor funnels the melt from the binocular shaped end of the extruder to a round rod which matches the back of the die.
- Phase Two: Die There is an orifice ring or a breaker plate between the Y-Block or Die Box and the orifice ring provides a seal between the die and the adaptor. The breaker does the similar function as the orifice ring but breaks the PVC melt from the extruder which looks like a solid rope into smaller strands. This is useful when more back pressure is required. The addition of a screen pack to the breaker plate can increase the back pressure even more if required. The addition of 1 – 3 can be added. They are added to the extruder side of the breaker plate. The screens can also filter out contaminants from the melt. Instructor Note Define the following terms: Die Box , Y-Block
- Phase Two: Die and Calibrator The die box is attached to the extruder adaptor or mounted directly to the Y-Block. The dies are made slightly smaller then the hole in the die box to allow for a slip fit. It is important the dies are cared for to prevent dings which would not allow them to slide freely into the die box. Depending on the size of the die there may or may not be a retaining ring which clamps the die into the die box. If there is not a ring then the bolts go directly through the die into the die box.
- Notes
- Phase Two: Die and Calibrator The die shapes the PVC melt or extrudate from the extruder into the desired shape. Depending on the complexity of the shape, desired output rate and tolerances, the design of the die will follow profile requirements. The die contains the following plates: Distance Plate Distribution Plate Torpedo & Mandrel Plate Compression Plate #2 & #1 Outlet Plates and Mandrel Top The above diagram displays a square die. Although JELD-WEN uses round dies, the order of the plates is the same. The diagram provides an overview of how the die is bolted together. It can give you a perspective on how each part provides a detail of the profile that is being shaped as the PVC Melt is being pushed through it. The next slide displays a round die.
- Phase Two: Die Die structures vary from machine to machine. For JELD-WEN, consider the following die structure. Match the die part and function below to the picture above. JELD-WEN Die Structure Die Part Function Distance Plate The distance plate is a filler plate to make all tools the same length so they all fit correctly into the die box. Distribution Plate The distribution plate begins to shape the solid PVC melt from the extruder into a specific profile. It streamlines the flow of the PVC melt from the extruder into the die shape. Torpedo & Mandrel Plate The torpedo and mandrel plate divides the melt into individual strands that make up the exterior and internal walls of the profile with other distinct features. This can vary from 2 to 8 or more strands. Compression Plate The compression plate is tapered to compress and weld the rough strands back together eliminating possible weak areas due to the webs in the mandrel pate. The compression plate is also used to transition from the mandrel plate to the final die exit opening. #2 & #1 Outlet Plates and Mandrel Top The stands are pushed into the profile shape so that when the extrudate leaves the die, it can be formed into the exact profile in the calibrator.
- Phase Two: Melt Rheology The extruder has combined the PVC Powder with heat and pressure to fuse the material into a unified mass. The unified mass is a term known as PVC melt. The extruder is exerting pressure on the PVC melt which moves it forward. The PVC melt moving forward is called flow. Note The Greek work for flow is rheo. The study of flow is rheology. The hot PVC melt is forced through the die using pressure from the extruder and refines the shape of the profile. The calibrator continues to size the profile by using water and a vacuum. In the pictures above, you can see: Top Picture The PVC melt coming from the extruder Middle Picture The PVC melt coming from the die and being “strung up” into the calibrator Bottom The PVC melt in-between the die (left) and the calibrator (right). The blue tubes on the calibrator send cooling water around the PVC melt/profile held in a vacuum. The red tubes take the used water away from the cooling profile. The white tubes provide the vacuum.
- Phase Two: The Science of Flow Flow is very important as it determines the quality of the profile that is produced. It must be monitored throughout the line. Through experience you will learn how to read the flow in the Visual Check Points. There are many mathematical formulas used to calculate and describe flow. Let’s begin by understanding the following: Shear Stress Shear Rate Melt Temperature Melt Viscosity. Instructor Note Discuss the above picture. Ask: Is this a good melt? Explain why or why not.
- Phase Two: Stress, Rate, Temperature & Viscosity Let’s look at how to measure flow. By understanding flow, you will be able to think about how to determine quality problems with your profiles. Conclusion You control the barrel temperatures and the speed of the screws. The higher the melt pressure (shear stress) and the screw RPM (shear rate), the higher your viscosity or the flow of your melt through the die. NoteTemperature does effect viscosity as seen above. Shear Stress The amount of energy that is being applied. This relates to melt pressure behind the die. This pressure is being generated by the extruder. Shear Rate The speed at which the shear stress is being applied. To measure shear rate, use the RPM of the extruder screws. Melt Temperature The temperature of the material exiting the die. This is monitored through the Operator’s Panel. Melt Viscosity The stiffness of the material exiting the die.
- Phase Two: Laminar Flow and Static Wormy Polymer Chains Shear stress, shear rate, melt temperature and melt viscosity impacts the quality of the molten plastic used to produce the profile. When any of these factors are not functioning at a quality level it effects the laminar flow. The molten plastic mass that has no shear stress or shear rate will not flow. The molecules in this state are like a bowl of worms. There is no organization and cluttered mess of strings. In the above diagram, the polymer chains are in static form and look worm-like.
- Phase Two: Laminar Flow and Stretching to Form Layers When shear stress and shear rate are applied, the can of worms are aligned into organized layers and stretched. The amount of energy to make this happen is called, Activation Energy. When this energy is surpassed, flow will occur. This is called Laminar Flow. In the above diagram, the polymer chains are stretching to form layers. The energy to do this called, activation energy.
- Phase Two: Laminar Flow Achievement When flow occurs in the die, it will flow the fastest in the center and the slowest at the walls. The strength of the attraction between the layers of polymer during the Laminar Flow is the Melt Viscosity. The stronger the bond, the stiffer the melt, and the slower moving. Internal lubricants used in the PVC Powder Compound will help reduce this bond so that higher flow and lower viscosities are achieved. As a result, the leading edge of the PVC Melt exiting the die will be rounded. When the shear rate or shear stress is increased the flow will also increase. However, it will not be in a straight line. In the above diagram, flow is achieved by the exceeding the activation energy, casing the polymer layers to slide by each other. The polymer layers slide the slowest at the wall of the die and the fastest in the middle of the die.
- Phase Two: Laminar Flow and Melt Fracture If the shear rate and/or shear stress is increased beyond certain limits the material exiting the die can be adversely effected. Initially, one may see irregularities like pock marks and tear drop shaped lumps in the surface. If the limits of shear rate and/or shear stress are increased too far, the strings of material that are stretched will actually break and Melt Fracture will occur. During normal operating ranges of the extruder, melt fracture is not normally seen. Instructor Note Provide samples of profiles with pock marks, and tear shaped lumps in the surface, and melt fracture.
- Phase Two: Die Swell As the melt is forced to flow through the die, the polymer strings stretch. When the melt exits the die, the pressure is released and the polymer strings will recoil back. This is known as Die Swell. This is a know % for each type of compound, for PVC window profiles it is 2 to 8%. The above diagram indicates: Melt temperature 385º F Medium to High PSI Polymer chain inside die stretched with laminar flow Exit of die polymer chain relaxes and gets shorter and thicker 0 PSI is no flow or die swell
- Phase Two: Flow Challenges To get the correct flow properties there must be a balance of shear rate, shear stress, and melt temperature. If these are not correct, flow problems will occur. The flow challenges are: Poor surface, too dull or too shiny Pock marks Lumps Internal walls separating Wavy edges Loss of definition on edges Erratic flow could cause jam ups Excessive die or calibration fouling
- Phase Two: Calibration & Cooling In the calibrators, the melt is cooled and sized to desired profile dimensions. The die swell is off set by the draw down of the pulling action of the calibrator. The hot melt/profile from the die (380º F to 395º F) is pulled through the calibrations system by the Haul Off machine further down the line. The first calibrator is designed where cold water (50º F to 54º F) is circulated through internal water channels which results in maintaining the temperature of the calibrator. Vacuum slots are machined into the surface of the calibrator where the vacuum holds the melt close to the metal surface which allows for the cooling to take place. The vacuum that is created through these vacuum slots also prevents the profile from collapsing The temperature drop in the first calibrator can be from approximately 50º F to 120º F on the surface of the profile. The surface temperature of the profile in the first calibrator can be reduced by as much as 250º F. In the above picture, the blue hoses supply the cold water to the calibrator to cool the melt. The red hoses take the used, now warm water, away from the cooling area within the calibrator. The white hoses provide vacuum to the calibrator.
- Phase Two: Calibration & Cooling After the melt is pushed through the die and exhibits the normal die swell, it is pulled through the calibrators in preparation for the next step. After the melt is shaped by the heated die, it is cooled and further shape in the calibrator. As the melt is pulled, it is still hot and will stretch into a tear drop draw down form. If the melt is not cooled with water during this process, it could become so thin that it will jamb in the calibrator and break. The internal surfaces and walls of the profile can withstand higher temperatures. There is a temperature that above which the profile will still be pliable and malleable but below which it is rigid enough to be set. This temperature is called the Glass Transition or Tg. The Second Dry Calibrators maintain the sizing while removing more residual heat from the profile.
- Phase Two: Water Tank Calibrators Newer calibration systems incorporate wet calibration in the form of a series of water tanks with sizing elements mounted on the inside Cold water is pumped through the tanks and a slight vacuum is pulled to insure that the profile does not collapse inward The tanks can be very long and contain numerous elements If the profile leaving the dry calibrator is not cooled properly, chattering or humming will occur in the water tanks.
- Phase Three: Haul-Off End Product The purpose of the Haul-off & End Product Phase is to pull the profile through the calibration process, take the finished profile and cut it to size, and move the finished profile to the tilt table to be collected for storage. This is where the finished extruded profile will be checked for defects. Although Visual Check Points exist in each phase, this is the last opportunity to check for quality before the product is packaged. Samples are also taken to QC (Quality Check) Lab where the AAMA tests are performed.
- Calibration System: Ancillary Equipment Once the profile completes the cooling process in the water tanks, the vinyl is ready to receive finishing touches. The profile may still have moisture on it from the water tanks, bowed a little from the calibration process, or need a weather strip. To complete the job, equipment employed may include an air shower, bow heaters, and weather strip insertion. Mounted at the end of the calibration system platform are: Air Showers Blow excess moisture off the profile as it moves out of the calibration water tanks. Bow HeatersNormally attached to the end of the calibration table. They are radiant heaters that can be positioned to any side of the profile to correct any slight bow that might be generated during the calibration process. Weather Strip Insertion A device that inserts the pile weather strip into the profiles. Nail Fin PunchUsually located between the calibration table and the haul-off. Used to punch the holes in the nail fin of frames. The Calibration System Control Panels monitors downstream activities which includes: Speed of the puller taking the profile out of the die and moving it along the calibration system Water temperature Water cooling and vacuum control switches
- Haul-Off Station This is part of the downstream area. Pulls the finished and cooled profile from the calibrator, cuts it to size, and pushes the profile into an area for packaging. Haul Off or Puller Area that pulls the finished manufactured part from the calibration system. Guillotine The machine that cuts the extrusion to length. Tilt Table Receives the cut profile and moves it into an area for packaging.
- Haul Off or Puller The Haul Off or Puller is designed to pull the profile through the calibration system at a precise rate of speed. The unit consists of two tracks or belts that form a nip joint. The nip joint is created by air cylinders on each track that exert a closing force. This force is adjustable. The tracks are powered by two synchronized motors. These motors are controlled from the panel located at the front of the calibration table. The UP and DOWN movement is also controlled here. The tracks can and are often equipped with special contoured pads that fit to the profile so that the correct force can be applied for pulling through the calibration system. These are often of a quick disconnect design so that changeovers are done quickly. The pressure on the closing cylinders should be adjusted low enough so that there is no slippage of the profile but not so high that the profile is being deformed. Maintenance of the track and the pads are critical. Any slack or looseness in the track could result in erratic motion. The pads should be examined for wear and damage routinely. The pads will become hard on the surface over time and become slick. This could result in requiring a higher closing pressure on the tracks which could lead to deformation of the part. The pads should be clean when they become slick.
- Guillotine The guillotine is often attached directly to the Haul-off Station. This is done to allow the blade to be as close as possible to the exit of the pulling tracks. The blade is located over the travel table. When the blade is activated a servo motor moves the blade down to create the cutting motion. The travel table will clamp onto the profile and move forward during the cutting action. The cutter is activated when a pulse generator senses the movement of the profile or a preset distance is reached. The pulse generator sensor is a digital device that is mounted on the puller. Instructor Note Someday other saws may be added to the extrusion line. These are designed to precut the profiles to an exact size with the miter cuts on each end. This is a value added step can save the window plants significant time and space.
- Phase Two: Pulled by the Haul-Off After completing cooling in the calibration water tanks, the profile is now cooled and sized correctly. It continues through the Haul – Off Station. The profile may exhibit a bow or bend in the longer lengths. This is caused by differences in calibrator drag and more often, differences in the rate of cooling. Some of this is unavoidable. Between the last water tank and the Haul-Off Station, a series of heaters are mounted so the Bow can be corrected, if needed.
- On-going Phase: Trouble Shooting Trouble Shooting is an on-going process. There have been many terms used to address the concept of trouble shooting. These names include but are not limited to terms like problem solving, root cause analysis, critical thinking, or process optimization. As you experience development of the profiles on the line, you will be go beyond the concepts presented in training as you apply this knowledge to your work at JELD-WEN. You will be able to identify what is happening and why. Whenever there is a defect in the end product, you need to systematically figure out what is happening and why. Then corrective action can be pursued. The following pages describe the Visual Check points you will be working with as PVC compound is turned into a profile extrusion. A fundamental description of what to look for at each check point will support your efforts to create a quality profile. The diagram above displays the Visual Check Points in the Vinyl Extruder Powder to Profile process. Let’s take a closer look.
- Trouble Shooting at the Extruder Feed Port & Control Panel When a problem happens, one must walk through a process and determine the cause. Start at the Back of the line phase one of the process. The beginning of all extrusion is the Feed Port of the extruder. This is the first opportunity you have to check on the quality of the PVC compound. If the doser feeders are used, you must ensure that the correct amount of PVC compound is on the screws. There needs to be a minimum of 4 to 6 inches of PVC compound above the screws. Check Extruder Conditions at the Control Panel. Control Panel Monitors Temperature Settings of the Barrel Doser Feed Settings Extruder RPM Vacuum Pump On Motor Load or AMPs for Abnormal Variations Melt Pressure Temperature Settings of Adaptor and Die Zones Melt Temperature of the Adaptor NOTEEvery machine is different. To access exact settings on the Control Panel, check the set-up directions for each profile.
- Visual Check Point B –Vacuum Port The vacuum port is located 2/3 of the way from the feed port, toward the die. To view the condition of the PVC powder, it is best to look through the glass with a flashlight. If the vacuum port must be opened the vacuum must be turned off and the vacuum released in order to open the lid. The condition of the PVC powder at the vacuum port should look like a dull, crumbly belt or strip with broken edges. The PVC powder should NOT be a fused ribbon at this point. If the PVC melt does not meet this dull, crumbly, breakable belt condition, consider the following: Change the temperature in barrel zones 1, 2, and/or 3 ( depending on extruder size) - Zones 1 & 2 for Extruders 63mm - Zones 1, 2 & 3 for Extruder 93mm and 72mm When you close the vacuum port, make sure the o ring is attached correctly as it affects the vacuum being applied CAUTION All material run during the time the vacuum is turned off must be thrown out as it will not pass impact testing. NoteThe temperature and vacuum requirements will depend upon the equipment being used, the profile being produced, and the PVC compound. Check set-up requirements for the profile and the Operator’s Manual for standard requirements.
- Visual Check Point C – Melt Exiting the Die The next Visual Check Point is in Phase Two where the melt exits the die and enters the first calibrator. At this point, there should not be excessive vapors rising from the melt or build up on the lips of the die. Excessive vapors or build up on the lips of the die could indicate the melt temperature is too high. If the PVC melt has vapors or build up on the lips of the die, check the following: Check the thermocouples and the heaters are wired in proper sequence Check the melt temperature on the control panel Check the flow of the melt entering the first calibrator. It should be centered in all directions. Check the distance between the die and the first calibrator. It normally will be between ¼” to 1 inch. The surface appearance of the melt can be checked here also. Additional Checks on the Control Panel & On-the-Equipment Inspect calibrator’s water in & out connections plus the vacuum connections Mounting of the calibrators for proper sequence: alignment to each other & the tank elements Assure the bolts & fasteners are tight Proper water pressure Proper water temperature Proper vacuum source
- Visual Check Point D – Melt Exiting the Water Tanks As the extrusion exits the water tanks it is possible to make visual checks, looking for: Scratches on exposed surfaces Weaves on the free legs and corners Sink lines Weather-strip opening variations It is also possible to make some physical measurements here. This will save time and scrap during the startup process.
- Visual Check Point E – Haul-Off The last Visual Check Point is at the Haul-Off table. After checking the vacuum port, die, adaptor, and calibrators, check for the following in the Haul-Off Station. Scratches on the profiles, rough cut edges, uneven profile cuts, or an uneven surface can be caused by problems in this area. Haul - Off Check Points The condition of the track or belt Missing or loose contour pads Belt or pad slippage High belt closing pressure Variances in belt speeds Clean contour pads
- Visual Check Point – Guillotine Besides the belts, pads, and speed in the Haul-Off Station, the guillotine is another key area to check. Guillotine blade heater Up and down function of the Guillotine Dull Blade Proper Clamping Clearance in clamping area Rough cut edges Uneven profile cuts
- Summary These Visual Check Points are but a few areas to consider when a problem happens. It is important to be systematic and to check all possibilities when defining the cause. Start in the Back of the extruder first and work your way forward. Eliminate possibilities as you go. Let’s review this last section. Instructor NotesReview the following questions with the class. The participants will have the summary but not the questions. Then go to the Extruder Game to review the entire module. Review Questions 1. What is the purpose of Phase Three? The purpose of Phase Three is to pull the profile through the calibration process, take the finished profile and cut it to length, move the finished profile to the tilt table to be collected for storage, and to check for product quality. 2. How many Visual Check Points exist in the Powder to Profile process? There are 5. 3. Where are the Visual Check Points in each phase?A. Feed Port and Control PanelB. Vacuum PortC. Melt Exiting Die and Entering the Calibrator D. Extrusion Exiting the Water Tanks E. Haul-Off Table
- Review Questions 4. What does the Control Panel monitor for extruder conditions? Check Extruder Conditions at the Control Panel Temperature Settings of the Barrel Doser Feed Settings Extruder RPM Vacuum Pump On Motor Load or AMPs for Abnormal Variations Melt Pressure Temperature Settings of Adaptor and Die Zones Melt Temperature of the Adaptor 5. What do you look for at the Vacuum Port? Using a flash light, look through the glass. If you open the vacuum port, make sure to turn turn it off and release it before completely opening the lid. The condition of the PVC powder at the vacuum port should look like a dull, crumbly belt or strip with broken edges. The PVC powder should not be a fused ribbon at this point. To correct the situation, change the temperature in the barrel zones 1,2, and/or 3, depending on the extruder size. Before closing the vacuum port, make sure the o ring is attached correctly as it affects the vacuum being applied. 6. When the melt exiting the die and enters the calibrator, there should not be excessive vapors rising from the melt or build up on the lips of the die. If this happens, this could indicate the melt temperature is too high. If the PVC melt has vapors or build up on the lips of the die, what do you check for? Check the following: Check the thermocouples and the heaters are wired in proper sequence Check the melt temperature on the control panel Check the flow of the melt entering the first calibrator. It should be centered in all directions. Check the distance between the die and the first calibrator. It normally will be between ¼” to 1 inch. The surface appearance of the melt can be checked here also. What additional checks should be made using the Control Panel? Additional Checks on the Control Panel & On-the-Equipment Inspect calibrator’s water in & out connections plus the vacuum connections Mounting of the calibrators for proper sequence: alignment to each other & the tank elements Assure the bolts & fasteners are tight Proper water pressure Proper water temperature Proper vacuum source
- Review 7, What do you look for at Visual Check Point D, Melt Exiting the Water Tanks? As the extrusion exits the water tanks it is possible to make visual checks, looking for: Scratches on exposed surfaces Weaves on the free legs and corners Sink lines Weather-strip openings variations It is also possible to make some physical measurements here. This will save time and scrap during the startup process. 8. What do you look for at the Haul-Off Visual Check Point? The last Visual Check Point is at the Haul-Off table. After checking the vacuum port, die, adaptor, and calibrators, check for the following in the Haul-Off area. Scratches on the profiles, rough cut edges, uneven profile cuts, or an uneven surface can be caused by problems in this area. Haul - Off Check Points The condition of the track or belt Missing or loose contour pads Belt or pad slippage High belt closing pressure Variances in belt speeds Besides the belts, pads, and speed in the Haul-Off area, the guillotine is another key area to check. Guillotine blade heater Up and down function of the Guillotine Dull Blade Proper Clamping Clearance in clamping area Rough cut edges Uneven profile cuts TransitionSummarize the whole section on Rheology. Do the Extruder Game to review key points and to see how much participants are remembering. Advise participants not to worry if they do not remember everything. Key points will be reinforced and remembered as you work the process. You may take the participants to the floor again and reinforce the details of each section of the extruder equipment & process. Reinforcing the new information learned in this module.