I'm having constant snags & jam-ups. Why?
There could be a number of reasons why you are having this problem:
The distance between the belt exit & the inlet guide bush is too long:
For very flexible material, make sure that the distance between the end of the caterpillar belt nip and the inlet guide bush lead-in is kept to a minimum.
It may be necessary to turn the end of the inlet guide bush into a cone. It can then fit snuggly into the gap between the infeed caterpillar belts.
This coned bush suggestion is recommended for flexible tubing, such as medical tubing, under 10 mm outer diameter.
In extreme cases, use a small tube to fit right into the belt nip point to guide the material into the inlet bush.
The exit guide bush is too long:
When cutting short lengths or very flexible materials, make sure that the exit guide bush is not over long.
If too long, material will have to be pushed an excessive distance through the bush. This will cause drag & product hold-up.
It may be necessary to machine an internal cone into the exit guide bush to allow very short cut lengths to exit with impediment.
Please take care to ensure that any shortening of the exit bush doesn't compromise its role as an exit guard to the knife blade!
In the case of very short cut lengths it may be necessary to fit a custom exit guard.
The guide bush bore is not smooth:
Make sure that the internal guide bush bore is smooth and free from machining rings and other potential drag points.
If possible, polish the bore or use a very low friction material (e.g. PTFE) as an insert in the guide bush.
Alternatively, use low pressure compressed air, blown down the bush, to create an air cushion around the extrudate to minimise drag.
This method is particularly recommended for very sticky materials such as uncured silicone rubber.
The extruded material isn’t straight as it enters the caterpillar belts:
Check that the extrudate is straight as it enters the caterpillar. Adjust the inlet guide rollers until it is.
If the material has been coiled before it is cut, it may have a tendency to try to twist or curve as it passes through the inlet guide rollers. This will cause problems, as the material may not line-up correctly with the bore through the inlet guide bush
If this is a problem, add additional guide-in rollers at the entry point into the caterpillar.
In very bad cases, use a tube guide to direct the extrudate right up to the caterpillar infeeder inlet belt nip.
The cutter bush <> blade gap is too wide:
The inlet & outlet faces of the cutter bushes need to be touching the knife blade. If there is too much of a gap, the material being cut can be forced down into the gap. This will almost certainly cause a jam or snag.
For more details please see our FAQ on cut quality & guide bush setting:
The knife blade is not the correct shape:
Because the extrudate is trying to move forward continuously during the cutting action, a large curved blade may cause excessive product hold-up. This may cause a jam or snag.
Check that you are using the narrowest blade possible. If necessary, grind away the back of the blade to reduce product hold-up.
Please see our FAQ on blade types & cutting actions here:
The knife blade is fitted incorrectly:
With our older cutting machines it is possible to fit the blade incorrectly into the blade holder. The blade can be 180o out of position. If this was so, then it would be stopping between the guide bushes & blocking, or partially blocking, the passage of the extrusion through the bushes.
There is a reference notch on the blade holder to assist blade location. The blade must be set in the correct position relative to this notch. Please refer to the downloads section below for drawing showings this position.
For more advice please email our Tech Team: firstname.lastname@example.org