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View Full Version : NESTED PLASMA CUT - CANNOT COMPLETE ONE PART AT A TIME



Beefy
10-17-2014, 06:26 PM
There's a Sheetcam JOB file in the attached zip folder. It's a very simple cut for illustrating this problem.

I drew a disc with a small hole in the middle. Import into Sheetcam. In Sheetcam I put the small hole on a separate layer and use a drill operation on this layer to mark the hole centre with the plasma torch, all good.

The outer circle is on the other layer and I apply a normal cutting operation.

With just the one part, the hole centres are marked and then the outer cut is done, all good.

Here's the problem: when I want to cut multiples of this part, whether I use copy, duplicate, multiple duplicate, or array, I cannot get the parts to complete one at a time, i.e. mark hole centre & cut outline on part 1, then move to part 2 and repeat. Instead Sheetcam wants to do all hole marking on every part before starting ANY outside cuts.

Can Sheetcam not do this. Tried selecting "Keep Parts Together" in the cutting operation, but obviously this won't help seeing as the hole marking is in drill operation.

Keith

LeeWay
10-17-2014, 08:33 PM
I'm not sure how that would be done, but there are benefits to cutting all the circles and then the outers. The parts have a chance to cool slightly between the inner and outer cuts. I always do all mu holes and inside profiles first on the nest. Then outer profiles. Probably why I haven't researched how to do that.
You can send Les a direct email.
He is excellent about giving quick answers.

Beefy
10-18-2014, 01:57 AM
Hi Lee,

thanks for the reply. I often do what you mentioned when it comes to nesting. When all internals are done first then all the outlines can be cut at once and I often employ chain cutting as much as possible, even adding odd shaped open link lines between parts, especially good on thicker steel where you want to minimise pierces. I've even done bridge cutting of groups of parts by modifying the file in Coreldraw first.

However for larger quantities of smaller parts, I forsee the potential of thermal expansion moving the plate then the internal cuts / hole marks would not be accurate with outer perimeter cuts, especially by the time the cut gets to the opposite end of a sheet. This is the very reason for "Keep Parts Together" selections in Sheetcam.

Anyway I figured out what was the cause of the issue:

Seems the "problem" (Sheetcam was actually doing the right thing) was to do with minimizing tool changes. The drill operation and the plasma operation were using different plasma TOOLS.

Went to OPTIONS menu / JOB OPTIONS / NESTING tab / OPTIMISATION box, and the selection was MINIMISE TOOL CHANGES. Guess this setting makes the first tool go through all of its tasks before allowing the 2nd tool to start. So changed the selection to MANUAL OPTIMISATION (KEEP PARTS TOGETHER) and now each part would complete before moving on to the next one.

So seems that is sort of a global "keep parts together" for the job, whereas the "keep parts together" selection in the operation box only applies to that operation.

Keith.