Today we are disucssing about roll forming machine troubleshooting: Cut Length Tolerance! It is a very common question that many users may have during their operation of a roll forming machine. To well understand this question, we must be aware of the difference between two cut methods of roll forming machines.

As we know a roll former usually cuts the roll formed profiles automatically according to required lengths and quantities through PLC control system. However, some roll formers measure the length via a counter or an encoder, and some other roll forming machines require manual measurement of cut length instead of an encoder. After the required cut length is measured and the position switch is set up manually at the right spot, roll forming production starts.

Fixed-Length Cut

This cut method is named as fixed-length cut. It’s not as automatic as multi-lengths cut or encoder-cut, but it rarely cuts in any tolerance, which is why there are still many operators or plant managers prefer such cut method, even though each shift of production can only produce one cut length. To cut a different length every time, the roll forming machine needs to be powered off, and the operator remeasures the length and sets up position switch at a different place.

Encoder Cut

Encoder-cut works in another way. It’s fully automatic and all the operators need to do is just input the required lengths and quantities through the HMI, the counting and measuring jobs are left to the machine itself. Each shift of production, it can cut up to 20 different lengths fully automatic with no need to stop the machine.

An ecoder-cut machine measures length via the counter, i.e. ENCODER. An encoder is pushed tight on the roll fromed sheet, and rotates as the roll formered sheets moves forward. During this roll forming process, the control system records how many circles the encoder rotates, calculates out how many meters the roll formed sheets move forward (easy math job), stops the machine and cut the sheet when the required length of the roll formed sheet is reached. This is exactly how an enoder-cut machine works.

Roll Forming Machine Troubleshooting

Back to the question at very begining, why is there cutting length tolerance after a roll forming machine is correctly set up? We need to do a roll forming machine troubleshooting and find as a matter of fact, this issue-cut tolerance, comes from an encoder-cut roll forming machine.

• On one hand, as production goes on day by day, the encoder is pulled loose and may slip on the roll formed sheet, instead of rotating. Sliping causes error on the result of length calculation (the perimeter of encoder cannot be calculated correctly). As a result, there will be cut tolerance for the roll formed sheets.
• On the other hand, a roll forming machine usually roll forms different thickness materials, and change of that may also cause encoder not rotate normally and to the end cut tolerance occurs.

Whenver cut tolerance takes place, do the below quick check.

• If no materials have ever been replaced, check whether or not the encoder works functionally.
• If different materials have been replaces, check carefully the surface of the sheet and whether or not the encoder slip on the sheet.
• Check PLC control system, if any default numbers about cut tolerance adjustment have ever been changed.

SOLUTION

• Try to adjust the numbers about cut tolerance according to the manual provided by roll forming machine.
• Adjust the postion of encoder.
• Change a new encoder and reset the numbers.
• Try to order a roll former with an innovated encoder, laser encoder for example

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