Solving Extrudate Problems Related to Cut Length, Cut Quality, Hang Ups and Jams
 

NOT GETTING UNIFORM CUT LENGTHS

 
Things to Check

Possible Solutions

Slippage in puller. 1- Check to ensure that the extrudate can not be pulled, with hand pressure, through stationary puller belts. If it can, the nip pressure should be increased. 2- If the nip pressure to hold the part starts to distort the part shape, check the condition of the belts to make sure they are not worn. If they are, replace them. 3- Make sure the extrudate is not wet or slippery. If it is, eliminate the source.
 
Puller belt speed variation. 1- Make sure voltage to motor is uniform.2- Do not make unnecessary changes to nip pressure as that may affect belt speed.
 
Is the extrudate stretching? 1- The puller belts must run at a constant speed and need to be set to exert the minimum pressure required to keep the extrudate moving or stretching may result, especially with softer materials or extrudate with very thin cross-sections.
 
Extrudate may be too tight or too loose in bushing. 1- The interior of the bushing should fit the profile snugly but not so tight as to cause the material to bunch up. The bushing may have to be relieved to allow smooth movement.2- If the bushing is too loose, the material is typically not supported properly during the cut cycle and this generally affects the cut quality, such as (squareness, tolerance, etc.).3- Make sure the knife blade brushes the face of the bushing as cuts are being
 
Extrudate not freely exiting the bushing after being cut which causes compression of incoming material. 1- Typical solution is to force cut pieces to exit with a blast of air after each cut or by putting an internal cone in the bushing.2- A take-away conveyor may also help.
 

POOR CUT QUALITY

 
Things to Check

Possible Solutions

Check & adjust blade gap 1- Turn the flywheel by hand to make sure the bushing is as tight to the cutter blade as possible so the blade brushes the bushing during each cut.
 
Is the blade sharp? 1- The double-beveled blade should be uniformly sharp. If not, replace it.
 
Are the bushIng edges sharp? 1- Make sure the bushing edges clean, sharp and are not rounded.2- The faces of the bushing should be at a 90° angle to the extrudate bore.
 
Extrudate/blade friction may be too high. 1- Lubricate the blade by adding distilled water (with or without a few drops of dishwashing liquid) or isopropyl alcohol to the lubrication reservoir. Some cutters include a blade wipe to ensure that excess liquid is removed from the blade.
All rights reserved. Copyright © Gardner Business Media, Inc. 2014 Cincinnati, Ohio 45244