1General Extruder Audit InformationByTimothy W. WomerFrom time to time it is necessary to do a complete an audit on the co...
2NOTE: The radial lift check shall be done with the reducer and its components atroom temperature. Otherwise, if the readi...
3adjustments to the machinery are being made. Alignments like this are crucialfor preventing damage to a gear box, screw f...
4Two-point Alignment MethodWhen performing a two-point barrel alignment, there would be no referencetarget in the front of...
5tolerances of .0002" (0.005 mm) can be achieved. The bore adapters arecustomized for each barrel diameter, but can handle...
6Figure 4- NORMAN MethodNOTE:This Extruder Audit is in general terms. Each ExtruderManufacturer has their own recommend Pr...
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General Extruder Audit Information

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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.

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General Extruder Audit Information

  1. 1. 1General Extruder Audit InformationByTimothy W. WomerFrom time to time it is necessary to do a complete an audit on the condition of anextruder to make sure that it is operating in top condition for maximumeffectiveness and efficiency. The following some general information that shouldbe considered to accomplish a good Extruder Audit.General Inspection Information1. Evaluate the condition of the gearbox output shaft bearings with lift check.a. Check and record the front quill I.D. for wear and proper fit with theshank of the screw.b. Inspect and replace any shaft seals that may show leakagec. Drain Gear box lubricant and wash any residue and metal shavings inthe bottom of the gearboxd. Change lubricant oil filtere. Check out gear box cooling system, primarily the heat exchanger if theextruder is fitted with one.2. Check the front barrel support for proper thermal expansion, lubricate slidepoints with high temperature silicone grease.3. Evaluate the effects of overhung loads which are produces forscreenchangers, melt pumps and dies.4. Measure and record the Feed Throat bore dimensions and inspect forexcessive wear or water leakage from the cooling cavity of the cast housing.5. Measure the barrel and screw for wear, envelope or complete profile.6. Check extruder base to floor stability.7. Evaluate heating and cooling system if required.a. Flow test cooling tubesb. Using a clamp-type ammeter or a multi-meter test check the resistanceof the heatersGear Box Radial Lift Check for Thrust Shaft BearingIt is necessary to check for bearing wear by conducting a radial lift check on thefeed section end of the thrust shaft if excess noise or heat is detected at thatlocation.
  2. 2. 2NOTE: The radial lift check shall be done with the reducer and its components atroom temperature. Otherwise, if the readings are taken above room temperature,thermal expansion of components may be factored into the measurements. Thiscould result in recording inaccurate values used in evaluating bearing wear andreplacement requirements.Procedure for Lift Check of Gear Box Bearing1. Lockout and tag-out the disconnect for the extruder drive before startinginspection of the gear reducer.2. Place a magnetic base dial indicator on the upper part of the face of thefeed section flange connected to the gear reducer.3. Place the indicator needle onto the top part (12 O’clock Position) of thethrust shaft end. Set the dial indicator to zero.4. Use a hydraulic jacking tool with hand pump to move the bottom part (6O’clock) position. Move the thrust shaft flange upward with enoughpressure to measure any movement and to obtain and accurate liftreading.IMPORTANT NOTE: Extreme care must be taken not to damage the thrustshaft flange when obtaining shaft movement.5. Record the reading for historical analysis of bearing wear.Extruder alignmentAn Alignment Telescope is also great for measuring the alignment of an extruderbarrel relative to a gear box drive quill. To accomplish this, targets are mountedin the gear box drive quill so that the Alignment Telescope can be positionedexactly on the gear boxs critical line.Once the telescope has been positioned, it optically represents the gear boxsdrive quill centerline. Then measurements can be taken on work targets (or onework target which is moved to several different positions) in the extruder barrel todetermine if the barrel is in alignment with the gear box drive quill.Deviations from the centerline can be quantified and technicians can be toldexactly how much to move machine components to bring everything back intoalignment. In fact, an instrument operator can observe the progress while
  3. 3. 3adjustments to the machinery are being made. Alignments like this are crucialfor preventing damage to a gear box, screw flight diameter and barrel insidediameter.Fig. 1 – Three point Barrel AlignmentNormally, only one work target is used and it is traverse it thru the barrel boreend to end. The three most critical points of alignment with the gearbox drivequill is the position where the barrel mounts are as follow:• The mounting location of the barrel to the extruder feed housing• The barrel position located directly over the front barrel support• The very end of the discharge of the barrelThese three locations are critical in cases, no matter what form of barrelalignment is used.In some cases, when there is a very heavy overhung load (large die, screenchanger, etc.) is mounted on the end of the barrel, a fourth critical location mayneed to be checked, which would be located between the barrel mounting flangeand front barrel support. If at the mid-point between these two locations ishigher, it may be necessary to have a second mid-barrel support which willactually hold the barrel “down” to insure perfect alignment.Barrel
  4. 4. 4Two-point Alignment MethodWhen performing a two-point barrel alignment, there would be no referencetarget in the front of the drive shaft.In this case, the barrel target would be used as a reference target to position thescope in the true location of the drive quill as shown in the figure below.The primary reason that this method is not preferred is that it ignores anymounting error that may be present from the gearbox face to the start of thebarrel mounting interface.Fig. 2 - Two-Position Barrel AlignmentSingle-Barrel Extruder ApplicationsWhen laser alignment equipment is used, it is mounted into the gearbox through-hole (counter bore) by using a self-centering chuck, as in the two-point method.The chuck has a specially adapted plate with a 0.750" (19.05 mm) hole that iscentered to the feet to within .0005" (0.01 mm). The laser projects the axis ofrotation of the extruder gearbox using a method we call the NORMIN (NORmaland INverted) procedure.The 2-Axis Bore Target and Bore Adapter are designed to find the center of thebore, without any moving parts, to a tolerance of .0005" (0.01 mm); with care,Barrel
  5. 5. 5tolerances of .0002" (0.005 mm) can be achieved. The bore adapters arecustomized for each barrel diameter, but can handle +/- .060" (1.52 mm) ofdiameter variance.The target and adapter are designed so that the laser is centered axially betweenthe four feet of the adapter, 2 of which are offset axially from the other two points.This, in effect, puts the laser on the pivot point of the adapter and allows theangle of incidence to the laser beam to vary by up to 45º. The target takesadvantage of this property by making the adapter slightly larger than the bore. Toinsert the target into the barrel, a spring-loaded pole is attached to the target andthe target cord is pulled. This tips the target forward, allowing it to easily slide intothe bore. When the cord is released, the target and adapter "jam" into the bore,finding the center automatically. The weight of the pole keeps the target centeredin the bore.Fig. 3 – Laser and Target SetupTo perform an alignment, the target is placed into the free end of the barrel. Theuser then performs Hamar Lasers NORMIN procedure which puts the laserbeam on the axis of rotation of the gearbox. That axis of rotation is projecteddown the barrel to the target. The reading produced from the NORMIN procedureis then a measure of the misalignment of the free end of the barrel to the gearboxaxis of rotation. Leaving the laser and target in the barrel, it can then be shimmedor moved until the readout displays .000" in both axes. If there is more than oneadjustment point for the barrel the target can be inserted into that point and it canbe shimmed or moved until the readout reads .000".LaserExtruderTargetLaser Beam
  6. 6. 6Figure 4- NORMAN MethodNOTE:This Extruder Audit is in general terms. Each ExtruderManufacturer has their own recommend PreventativeMaintenance Procedure which should be followed in allcases. But the most important aspect of any maintenancepractice is that at all times SAFETY must come first and allprecautions need to be taken by everyone involved in therepair of the equipment.

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