[otrotabi]

Hello everyone. Once upon a time -not so long ago- we had a CNC supplier who insisted on leaving 50 mm free space on the sheet border so that the clamps would not interfere with the punch itself. Since I did not operate a machine I took that as a truth, although I had a faint idea about repositioning.

Now that we operate our own machine, we want to minimize our scrap and maximize sheet metal use. We found the repositioning process relatively simple to implement and pretty safe, so basically I have two questions:

1) Was our supplier taking advantage of the fact that they did not pay for the sheet metal parts (they were only paid for the punching process) to make their job easier ?

2) Are there any drawbacks, potential issues, etc, regarding the use of repositioning ?

[Jimmy49548]

What is the table size?

[otrotabi]

2500x1270 mm (98.43 x 50") is the "logical" size, while the maximum sheet size is 5000x1270 mm (196.85"x50").

[Jimmy49548]

Typically, we don't use the reposition unless the parts are longer than table size. 50mm border does seem to be a waste of material, unless it is the clamp edge. The other 3 borders can be 25mm or less.

[otrotabi]

Yes, that´s what I meant. The 50 mm "free zone" are reserved for the clamps.

Being realistic, it is hard to make a sheet metal give more than 70 to 80% yield, most of the time we find ourselves using half a sheet or so, to put an example. And we also make plasma cut so scrap is not our main concern either, we can use small pieces there if we need to.

However there are quite a few of the parts we need to manufacture that would eventually need reposition, in case we decide to use the punch press instead of plasma. So actually my question is: should we try to avoid repositioning ? Or is it perfectly safe to use it when needed ?

[Jimmy49548]

If you have table extensions for material support when using the reposition, it's not a big deal. I try to avoid it unless the parts are longer than the table size due to handling of the scrap. It can be unmanageable and unsafe at times. The yield is not always the best but that is the nature of the process.

[otrotabi]

I understand. We will implement the table extensions for safety when using repositioning. I also noticed our program uses G25 instead of G27 to reposition by default. I will need to check that too once I get used to the process.

One last question: our software allows to program a rotation transformation, to allow using sheet sizes which extend further than the machine´s table size, which in our case would be a sheet size larger than 1270 mm. When you use that tool, a Stop Machine M00 is inserted, you need to rotate the sheet, and then process the rest of the sheet. Is that a tool that is used sometimes ?

[Jimmy49548]

When a program has a reposition, I set the program to do the reposition first with a G25 which will retract the clamps 1.27mm. When it repos back I use a G27. G27 does not have the retract.
The M00 is a useful tool when running a program as you described. Be careful when processing sheets larger than the table size. The sheet may crash into the frame of the press if not properly programed.

[otrotabi]

Once again you have been very helpful. I appreciate it.

Regards