Extruder Barrel Borescoping                                      Submitted by                                   Timothy W....
brass shim stock may need to be installed in the proper locations to improve the barrelbore alignment. (HINT #2)In conclus...
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Extruder Barrel Borescoping

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One of the most important maintenance processes in an extrusion facility is the bore measurement and alignment of the extruder barrel. This is typically done by means of borescoping, either optically or with lasers. Most Original Equipment Manufacturers (OEM) either use alignment bars or borescoping during the assembly of the new extruder.

Typically, small extruders from 1.5” to 3.5” diameter, the alignment bar method is used. In most cases, any extruder that is larger than 2.5” in diameter, when a new barrel is installed or if for some reason the existing barrel is removed and re-installed, the extruder should be aligned. If an existing barrel is being aligned, then the bore should be measured to determine if there is any wear to the bore and where the wear is located so that this information can be used to during the alignment process.

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Extruder Barrel Borescoping

  1. 1. Extruder Barrel Borescoping Submitted by Timothy W. Womer VP of Manufacturing and Engineering New Castle Industries, Inc.One of the most important maintenance processes in an extrusion facility is the boremeasurement and alignment of the extruder barrel. This is typically done by means ofborescoping, either optically or with lasers. Most Original Equipment Manufacturers(OEM) either use alignment bars or borescoping during the assembly of the new extruder.Typically, small extruders from 1.5” to 3.5” diameter, the alignment bar method is used.In most cases, any extruder that is larger than 2.5” in diameter, when a new barrel isinstalled or if for some reason the existing barrel is removed and re-installed, the extrudershould be aligned. If an existing barrel is being aligned, then the bore should bemeasured to determine if there is any wear to the bore and where the wear is located sothat this information can be used to during the alignment process.One of the most important parts of barrel aligning that most people do not consider is thatthe thrust bearing in the extruder gearbox must be pre-loaded before a proper alignmentcan be done. If the thrust bearing is not pre-loaded then the drive quill can possibly sagor droop downward on the thrust bowl end of the gearbox. Therefore, some sort ofsupport or pre-load mechanism must be used to insure that the drive quill is properlycentered to the gearbox assembly. (HINT #1)Once the drive quill has been centered, then the alignment process can begin. The mostprefer method of borescoping is the used of an independent tripod to hold the opticalscope or laser equipment. Some individuals use the method of directly mounting thescope or laser to the backside of the drive quill. This method does have the advance thatif the extruder is out of level, the scope is in-line with the bore of the drive quill. Butwith the scope or laser attached directly to the extruder gearbox it has the disadvantage ofbeing influenced by the extruder. Therefore having the scope or laser mounted on anindependent tripod arrangement and away from the extruder, any influence from theextruder can be neglected.Once the scope or laser has be zeroed into reference of the drive quill bore, now the feedthroat and barrel can be measured for alignment to the drive quill of the gearbox. Amoveable target should be used which can be transported easily from end to end of theextruder barrel bore. In doing so, the barrel may need to adjusted to that the barrel iswithin .002”/foot over the length of the barrel in both the “X” and “Y” axis.For example, a 3.5” x 30:1L/D extruder will have a barrel that is approximately 96” long,therefore, at .002” / foot of barrel length, the barrel should be aligned to within .016” inboth the “X” and “Y” axis. If for some chance the barrel is out of tolerance more that thedesignated amount, then either the front barrel support screws may need to be adjusted or
  2. 2. brass shim stock may need to be installed in the proper locations to improve the barrelbore alignment. (HINT #2)In conclusion, a properly aligned barrel will help reduce screw and barrel wear,possibility decrease un-explainable elevated melt temperature or zone over-ride, or evenpossibly screw shank to drive quill mis-engagement. All of which will improve theoverall life expectance of the extrusion equipment and reduced maintenancerequirements. (HINT #3)

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