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A mixing study of various single screw mixing elements using inline melt analysis
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The material handling of the feedstock is a very critical part of the extrusion process. If the feedstock is not introduced to the feedsection of screw in a smooth and uniform matter, then the likelihood of a stable and consistent output is unlikely. This is the reason why it is very important that if regrind is added to the virgin feedstock, it must be done very consistently and uniformly. It should also be mentioned here that a very important part of the extrusion equipment is the hopper and feedthroat section. If the hopper and feedthroat sections are not designed properly, inconsistent material flow to the screw can take place. For example, if the conical section of the hopper (see figure) does not have the proper transition, the resin will not flow smoothly into the feedthroat of the extruder.
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There are basically three Coefficients of Friction (Figure 1) that take place in the feed section of the screw, (1) between the barrel and the pellet, (2) between pellet to pellet, and (3) between the root of the screw and the plastic pellet.
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Screw and barrel wear is critical in all plasticating applications whether it is extrusion, injection molding, and blow molding, plus twin screw extrusion. Excessive screw and barrel wear can cause instable throughput or recovery on reciprocating screws, increased melt temperature and reduced plasticating rates.
Screw and barrel wear
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Almost all processes, extrusion, injection and blow molding require that regrind be used in the process. Depending on the process greatly determines the amount of regrind that is generated. Some processes produce very minimal amounts of regrind, such as an injection molding process using a hot runner system versus a flat sheet extrusion process producing thermoformed sheet and the entire skeleton has to be fed back into the process or a blow molding process which always generates large amounts of regrind.
Regrind particle size
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I have written in the past about screw/barrel wear and also screw rebuilding, but there are some screw and barrel shops that offer an alternative for excessive barrel wear and that is honing the barrel oversize and then rebuilding the screw oversize also to fit.
Oversize Screw and Barrel
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Recently a processor installed a new screw into their 6” x 32:1 L/D extruder. Within a few weeks the hard facing that had been welded on the flight OD started to pop off. (As shown in the attached photo) The flight failure was in an isolated area, so it was then assumed that the failure was due to a poor weld bond. The screw was ultra-sonically inspected and the remaining flights showed good bore, but the entire screw was rebuilt and returned to the customer.
Over-hung Loads
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Many companies have their own procedure for starting up and shutting down an extruder or injection molding machine and, depending on the process, there may be reasons for the specific method. But from the point of view on the effect of the screw itself, the following procedure will produce the best overall results.
Extruder or Injection Molding Machine Startup and Shutdown Article
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Recommended
Introduction to final accounts
Introduction to final accounts
ry_moore
The material handling of the feedstock is a very critical part of the extrusion process. If the feedstock is not introduced to the feedsection of screw in a smooth and uniform matter, then the likelihood of a stable and consistent output is unlikely. This is the reason why it is very important that if regrind is added to the virgin feedstock, it must be done very consistently and uniformly. It should also be mentioned here that a very important part of the extrusion equipment is the hopper and feedthroat section. If the hopper and feedthroat sections are not designed properly, inconsistent material flow to the screw can take place. For example, if the conical section of the hopper (see figure) does not have the proper transition, the resin will not flow smoothly into the feedthroat of the extruder.
Solids conveying consistency
Solids conveying consistency
R&B Plastics Machinery
There are basically three Coefficients of Friction (Figure 1) that take place in the feed section of the screw, (1) between the barrel and the pellet, (2) between pellet to pellet, and (3) between the root of the screw and the plastic pellet.
Extruder Screw Cooling
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R&B Plastics Machinery
Screw and barrel wear is critical in all plasticating applications whether it is extrusion, injection molding, and blow molding, plus twin screw extrusion. Excessive screw and barrel wear can cause instable throughput or recovery on reciprocating screws, increased melt temperature and reduced plasticating rates.
Screw and barrel wear
Screw and barrel wear
R&B Plastics Machinery
Almost all processes, extrusion, injection and blow molding require that regrind be used in the process. Depending on the process greatly determines the amount of regrind that is generated. Some processes produce very minimal amounts of regrind, such as an injection molding process using a hot runner system versus a flat sheet extrusion process producing thermoformed sheet and the entire skeleton has to be fed back into the process or a blow molding process which always generates large amounts of regrind.
Regrind particle size
Regrind particle size
R&B Plastics Machinery
I have written in the past about screw/barrel wear and also screw rebuilding, but there are some screw and barrel shops that offer an alternative for excessive barrel wear and that is honing the barrel oversize and then rebuilding the screw oversize also to fit.
Oversize Screw and Barrel
Oversize Screw and Barrel
R&B Plastics Machinery
Recently a processor installed a new screw into their 6” x 32:1 L/D extruder. Within a few weeks the hard facing that had been welded on the flight OD started to pop off. (As shown in the attached photo) The flight failure was in an isolated area, so it was then assumed that the failure was due to a poor weld bond. The screw was ultra-sonically inspected and the remaining flights showed good bore, but the entire screw was rebuilt and returned to the customer.
Over-hung Loads
Over-hung Loads
R&B Plastics Machinery
Many companies have their own procedure for starting up and shutting down an extruder or injection molding machine and, depending on the process, there may be reasons for the specific method. But from the point of view on the effect of the screw itself, the following procedure will produce the best overall results.
Extruder or Injection Molding Machine Startup and Shutdown Article
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I was recently asked to visit a facility that was a flat sheet producer to determine the cause of a major screw design problem. So, as always, I have to start at the beginning to gather all of the technical information to determine the root cause. This facility had 5 large extrusion sheet lines and they were issues with all 5 extruders...
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Since the early 1990’s INGEO™ resins have made enormous improvements in the process ability of their bio-polymer resins. In the early days, when the resin was first being manufactured at pilot plant levels, extrusion processing of INGEO™ was very difficult. Today, natural additives are being used to improve the process ability of these resins. Several new lubricant additive packages were tested to determine which package produced the best overall performance and process improvements. The process data was used to quantify the process ability of the various additive packages. The data was then compared to the internal pressure data that was collected to analyze and determine the best overall additive package.
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When a new extruder is installed, or a new screw mounted in an existing machine, do you know what the expected throughput rate is going to be? You should. If you don’t baseline your extruder, then how are you going to set realistic expectations for its performance? If extrusion screws are designed properly, they typically will be able to withstand the maximum torque available from the extruder and the resin being processed. The extruder should operate at approximately 90% of its full available torque, based on 100% pellet feedstock, which typically will be the worst-case scenario. By using today’s barrier screw technology, higher throughput rates, lower melt temperatures, and better power efficiencies can be obtained. This article will provide some basic insight to help processors to determine if they are obtaining the maximum production rates from their extruders, providing that they have adequate downstream cooling and handling equipment in the extrusion system.
Base Lining Your Extruder
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This paper will compare the total power consumption of two different means of heating/cooling systems: air and water. For a single 90mm extruder, the total power consumption, output rate, and thermal control will be used to compare the two cooling means. Four different resins will be used.
Comparison of two different cooling methods for extrusion
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R&B Plastics Machinery
Screw and barrel inspection plays a very important part in achieving exceptional production performance. The screw and barrel are major components of extrusion, injection molding and blow molding processes, and should be measured for wear at least once a year (preferably twice a year). Many U.S. companies schedule preventive maintenance (PM) during the week of Independence Day and again during the week of Christmas.
Screw and Barrel Inspection
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R&B Plastics Machinery
Plasticization rates can be greatly increased with the use of grooved feed extrusion. Grooved feed extruders can be used in a wide range of extrusion processes for higher output rates. This technology has doubled plasticization rates for some resins and processes as compared to smooth bore extruders. This paper will compare the performance of three different screw geometries while processing fractional melt HDPE. One of the main methods of evaluation will be the comparison of internal pressure profiles over the entire length of the screw at eleven different locations down the length of the barrel at two L/D apart.
Empirical evaluation of different groove feed screw geometries
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Differences in solids conveying, screw pressure profile generation, output, motor energy required, will vary between resins, barrel temperature profiles, and resin preheat temperatures, on a single stage low compression barrier screw design.
The effects of running different barrel temperature profiles for various resins
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An experimental investigation into melt pump performance
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There are two different areas of screw design for thermoplastic composites: the screw design which is being used to make the thermoplastic compound and the screw design which is used to process the compounded thermoplastic. This paper mainly discusses the latter of the two types, but many of the issues are pertinent to both.
Extrusion Screws for Thermoplastic Composites
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R&B Plastics Machinery
The paper presents a fundamental study of the polymer flow within a “wave” type screw channel. The analysis is performed on an “unwrapped” form of a conventional screw channel and a “wave” type channel of similar size. A 3D Finite Element Method (FEM) simulation was used to simulate the flow field and flow characteristics of the wave channel are compared relative to the plain channel.
3D FEM Analysis of a Wave Type Screw Channel
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I was recently asked to visit a facility that was a flat sheet producer to determine the cause of a major screw design problem. So, as always, I have to start at the beginning to gather all of the technical information to determine the root cause. This facility had 5 large extrusion sheet lines and they were issues with all 5 extruders...
Instrument Calibration
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Several years ago, a customer had ordered a new screw for their thin sheet process. They requested a throughput rate of 1600 lb/hr...
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Be careful when buying a used extruder because you might be buying a “pig in a poke”.
Buying a used extruder
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R&B Plastics Machinery
Since the early 1990’s INGEO™ resins have made enormous improvements in the process ability of their bio-polymer resins. In the early days, when the resin was first being manufactured at pilot plant levels, extrusion processing of INGEO™ was very difficult. Today, natural additives are being used to improve the process ability of these resins. Several new lubricant additive packages were tested to determine which package produced the best overall performance and process improvements. The process data was used to quantify the process ability of the various additive packages. The data was then compared to the internal pressure data that was collected to analyze and determine the best overall additive package.
New and Improved Screw Technology for Processing INGEO™ PLA
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R&B Plastics Machinery
When a new extruder is installed, or a new screw mounted in an existing machine, do you know what the expected throughput rate is going to be? You should. If you don’t baseline your extruder, then how are you going to set realistic expectations for its performance? If extrusion screws are designed properly, they typically will be able to withstand the maximum torque available from the extruder and the resin being processed. The extruder should operate at approximately 90% of its full available torque, based on 100% pellet feedstock, which typically will be the worst-case scenario. By using today’s barrier screw technology, higher throughput rates, lower melt temperatures, and better power efficiencies can be obtained. This article will provide some basic insight to help processors to determine if they are obtaining the maximum production rates from their extruders, providing that they have adequate downstream cooling and handling equipment in the extrusion system.
Base Lining Your Extruder
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R&B Plastics Machinery
This paper will compare the total power consumption of two different means of heating/cooling systems: air and water. For a single 90mm extruder, the total power consumption, output rate, and thermal control will be used to compare the two cooling means. Four different resins will be used.
Comparison of two different cooling methods for extrusion
Comparison of two different cooling methods for extrusion
R&B Plastics Machinery
Screw and barrel inspection plays a very important part in achieving exceptional production performance. The screw and barrel are major components of extrusion, injection molding and blow molding processes, and should be measured for wear at least once a year (preferably twice a year). Many U.S. companies schedule preventive maintenance (PM) during the week of Independence Day and again during the week of Christmas.
Screw and Barrel Inspection
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R&B Plastics Machinery
Plasticization rates can be greatly increased with the use of grooved feed extrusion. Grooved feed extruders can be used in a wide range of extrusion processes for higher output rates. This technology has doubled plasticization rates for some resins and processes as compared to smooth bore extruders. This paper will compare the performance of three different screw geometries while processing fractional melt HDPE. One of the main methods of evaluation will be the comparison of internal pressure profiles over the entire length of the screw at eleven different locations down the length of the barrel at two L/D apart.
Empirical evaluation of different groove feed screw geometries
Empirical evaluation of different groove feed screw geometries
R&B Plastics Machinery
Differences in solids conveying, screw pressure profile generation, output, motor energy required, will vary between resins, barrel temperature profiles, and resin preheat temperatures, on a single stage low compression barrier screw design.
The effects of running different barrel temperature profiles for various resins
The effects of running different barrel temperature profiles for various resins
R&B Plastics Machinery
Melt pump performance and efficiencies will vary according to the viscosity of the resin being pumped, and the discharge pressure that the melt pump will need to overcome. Resin melt temperature differences and power requirements of the pump, will vary according to the resin, and conditions that the pump will operate under. This paper will explore the processing differences in resins on gear pump performance at different pump speeds, at three different discharge pressures. Discharge pressures on the pump will be varied keeping the suction pressure constant, thus increasing the change in pressure across the pump. Melt temperature, and pump efficiency. melt pump motor amperage, and total output, (kg/hr) will then be measured and recorded.
An experimental investigation into melt pump performance
An experimental investigation into melt pump performance
R&B Plastics Machinery
From time to time it is necessary to do a complete an audit on the condition of an extruder to make sure that it is operating in top condition for maximum effectiveness and efficiency. The following some general information that should be considered to accomplish a good Extruder Audit.
General Extruder Audit Information
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R&B Plastics Machinery
6. nanocomposites a single screw mixing study of nanoclay filled polypropylene
6. nanocomposites a single screw mixing study of nanoclay filled polypropylene
R&B Plastics Machinery
An experimental investigation into solids conveying
An experimental investigation into solids conveying
R&B Plastics Machinery
Barrel temperature profiles for barrier type screw
Barrel temperature profiles for barrier type screw
R&B Plastics Machinery
There are two different areas of screw design for thermoplastic composites: the screw design which is being used to make the thermoplastic compound and the screw design which is used to process the compounded thermoplastic. This paper mainly discusses the latter of the two types, but many of the issues are pertinent to both.
Extrusion Screws for Thermoplastic Composites
Extrusion Screws for Thermoplastic Composites
R&B Plastics Machinery
The paper presents a fundamental study of the polymer flow within a “wave” type screw channel. The analysis is performed on an “unwrapped” form of a conventional screw channel and a “wave” type channel of similar size. A 3D Finite Element Method (FEM) simulation was used to simulate the flow field and flow characteristics of the wave channel are compared relative to the plain channel.
3D FEM Analysis of a Wave Type Screw Channel
3D FEM Analysis of a Wave Type Screw Channel
R&B Plastics Machinery
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(20)
Instrument Calibration
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Gross Versus Net
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Buying a used extruder
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New and Improved Screw Technology for Processing INGEO™ PLA
New and Improved Screw Technology for Processing INGEO™ PLA
Base Lining Your Extruder
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Comparison of two different cooling methods for extrusion
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Screw and Barrel Inspection
Screw and Barrel Inspection
Empirical evaluation of different groove feed screw geometries
Empirical evaluation of different groove feed screw geometries
The effects of running different barrel temperature profiles for various resins
The effects of running different barrel temperature profiles for various resins
An experimental investigation into melt pump performance
An experimental investigation into melt pump performance
General Extruder Audit Information
General Extruder Audit Information
6. nanocomposites a single screw mixing study of nanoclay filled polypropylene
6. nanocomposites a single screw mixing study of nanoclay filled polypropylene
An experimental investigation into solids conveying
An experimental investigation into solids conveying
Barrel temperature profiles for barrier type screw
Barrel temperature profiles for barrier type screw
Extrusion Screws for Thermoplastic Composites
Extrusion Screws for Thermoplastic Composites
3D FEM Analysis of a Wave Type Screw Channel
3D FEM Analysis of a Wave Type Screw Channel
A mixing study of various single screw mixinng elements using inline melt ana...
A mixing study of various single screw mixinng elements using inline melt ana...
A method for purging and cleaning a screw and barrel
A method for purging and cleaning a screw and barrel
A Method for Purging and Cleaning an Extruder Screw and Barrel
A Method for Purging and Cleaning an Extruder Screw and Barrel
An Empirical Study on Barrier Flight
An Empirical Study on Barrier Flight
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