Ganging Parts?

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Ganging Parts?

Postby tcgliderguy » Sat Apr 29, 2017 2:54 pm

I need to cut a lot of identical parts.... basically a 7-1/2 x 2-1/2 inch rectangle, with some 1" diameter holes, and 1/4" diameter holes in the middle. I drew up the part in ViaCad Shark, duplicated the shape in an array that is ten parts wide by three parts tall (for a total of 30), and exported a DXF file. I imported this file into Cut2D, generated a cutting file for Mach3 .... and the result was two or three different sized parts among the 30. Everything "appeared" to be fine in the previews of the parts. At first, I thought I was having a problem with my CNC router, but it cuts other, older files just fine. Is there something about "ganging" parts like this that I don't know about? Thanks for any suggestions....
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Re: Ganging Parts?

Postby ger21 » Sat Apr 29, 2017 2:56 pm

Make sure that the gap between all of the parts is the same. I'll occasionally place parts too close together, and the toolpaths for one part will cut into another.
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Re: Ganging Parts?

Postby tcgliderguy » Sat Apr 29, 2017 3:12 pm

Thanks Gerry.... I'm attaching a JPEF image of the parts in question. They're laid out to fit a 24" square sheet of PVC plastic. Some of the 7 1/4" long rectangles came out a full 1/4" short on length. I'm completely puzzled. I'm plunging the cut depth 1/8" per pass. It seems that if the machine was having a problem, it would not cut matching passes as the depth increases. ???
Attachments
GANGED 4 Hole AR Main Plate.jpg
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Re: Ganging Parts?

Postby kyeakel » Sat Apr 29, 2017 3:54 pm

When you say some of the rectangles come out .25 short, are the short ones all on the same row? Do others on that row come out correct? Do they show up short in the mach3 preview mode window? If they are intermixed on the same row, I'd look at the G-code and see if there is a difference in the position of the effected end vs the good one.

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Re: Ganging Parts?

Postby tcgliderguy » Sat Apr 29, 2017 4:01 pm

Thanks Kipp..... The loose parts are jumbled up, but I still have the outer sheet. I'll check it out and see if I can identify any kind of pattern to the anomaly...
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Re: Ganging Parts?

Postby ger21 » Sat Apr 29, 2017 4:53 pm

My guess is that the toolpaths are different on those parts for some reason.
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Re: Ganging Parts?

Postby tcgliderguy » Sat Apr 29, 2017 5:28 pm

I just measured the "pockets" that are left in the original 24" x 24" sheet..... They range in length from 7.5" to 7.125". What is strange is that there is no "stagger" in the cuts (both passes around each part are identical). There does not appear to be any pattern in the wide range of part size deviation.


So, philosophically, does it matter WHERE I duplicate the original part? In this case, I started with one drawing, and then used the "Duplicate" function in my CAD program (ViaCad Shark LT 9) to lay them out in a 3 x 10 grid.

Do you suppose it would make any difference if I imported one part into Cut2D, and cut and pasted my way to the same 3 x 10 layout there?

Thanks for the help with this weird science....

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Re: Ganging Parts?

Postby FixitMike » Sat Apr 29, 2017 6:16 pm

The part outlines must each be a single closed vector. If the outlines are unjoined multiple vectors, the outsides (and which side is cut) of subsequent vectors may switch sides. If the difference in size is one or two times the cutter diameter, that is likely to be what happened.

Use the Edit menu to select all open vectors and verify that the profiles are not selected to check.

Do a select all (control A) and use the join vectors tool to fix.
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Re: Ganging Parts?

Postby tcgliderguy » Sat Apr 29, 2017 6:21 pm

Fixit Mike..... Thanks! Yes, I have been using the "Join Open Vectors" tool in Cut2D to do what you described.... I don't think that is the problem. I just rebuilt the cutting files, this time doing the "Step and Repeat" multiplication of the part within Cut2D. I'm on my way out to the shop to try it out. I hope this works..... At this point, I am guessing that there is a bug in the "Step and Repeat" function within ViaCad Shark. I'll let you know how it goes...
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Re: Ganging Parts?

Postby Adrian » Sat Apr 29, 2017 6:24 pm

Why not just draw the whole thing in Cut2D and save the issues of having to join vectors etc. That's a very simple shape to draw in Cut2D and you remove all of the steps were problems can creep in.
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Re: Ganging Parts?

Postby tcgliderguy » Sat Apr 29, 2017 7:41 pm

It turns out that duplicating the part in Cut2D solved the problem. By selecting, and "control dragging" the part multiple times, I was able to get accurate results (on cutting a test piece from MDF). For whatever reason, doing the duplicate array in ViaCad turned into a mess. Because I have to share the drawings of these parts with my client, in a specified title block, etc., it isn't really practical to start the drawing in Cut2D. But Thanks, Adrian, for the suggestion.... Thanks to everyone who responded to this. It was a strange one....
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