Is there a setting to determine when arcs are converted to lines segments? I thought I changed something like that yesterday. Seems it was set to .05 and I changed it to .02. I can’t find it today.
Thanks
Try Options->application options->drawing import.
Turn up the detail reduction error. If you go too high you may get faceting on curves.
Also try turning up the arc fitting tolerance. If you go too high you may find it starts creating arcs in unexpected places.
Note for both of these options to take effect you need to reload the drawing.
I’ll try that. I did find what I changed the other day. It was the min acr size variable in the post. I had changed it to .02. I increased it to .06 and most of the arcs are cutting OK now. Some of the small ones are still cutting in exact stop mode though.
Interestingly, when I changed the min arc size and most of the arcs smoothed out, the torch stopping issue also seems to have gone away. Still not comfortable putting $200 worth of plate on the table until I know why it did that though.
It could be the shutting down was due to Mach hesitating. While hesitating maybe the plasma power source detected the torch wasn’t cutting and shut down to save the nozzle.
Increasing the min arc size in posts will help a lot. This controls when small arcs are converted to lines. For plasma cutting you can go as high as 0.1 or possibly even 0.2 without any problems.
Thanks Les…
What is “Minimum Segments for Arc Fitting”? My goal is to have Sheetcam only generate G02/03 code on circles or arcs with a consistent radius (like a rounded corner). What I’m trying to avoid are series of G01’s followed by G02/03’s. See the following code. Mach chokes on this code. It goes into exact stop mode and shakes the machine to death (and yesterday caused the torch to shut down).
N0390 G01 X4.9800 Y2.9950 F75
N0400 G02 X4.9821 Y2.9923 I-0.0223 J-0.0201 F75.0
N0410 G01 X4.9940 Y2.9757 F75
N0420 G02 X4.9954 Y2.9736 I-0.0244 J-0.0175 F75.0
N0430 G01 X5.0062 Y2.9555 F75
N0440 G02 X5.0073 Y2.9534 I-0.0258 J-0.0154 F75.0
N0450 G01 X5.0170 Y2.9338 F75
N0460 G02 X5.0181 Y2.9313 I-0.0269 J-0.0133 F75.0
N0470 G01 X5.0306 Y2.8990 F75
N0480 G02 X5.0314 Y2.8967 I-0.0280 J-0.0108 F75.0
N0490 G01 X5.0384 Y2.8733 F75
N0500 G02 X5.0390 Y2.8709 I-0.0288 J-0.0085 F75.0
N0510 G01 X5.0448 Y2.8432 F75
N0520 G02 X5.0451 Y2.8412 I-0.0294 J-0.0061 F75.0
N0530 G01 X5.0483 Y2.8181 F75
N0540 G02 X5.0485 Y2.8167 I-0.0297 J-0.0041 F75.0
N0550 G01 X5.0523 Y2.7751 F75
N0560 G02 X5.0523 Y2.7738 I-0.0299 J-0.0027 F75.0
This behavior is something new since upgrading Sheetcam. Previously, arcs had always cut smoothly regardless of their size. Was there a change in how Sheetcam interpolates arcs? I don’t really know enough about what each setting does to be able to make it do what I want.
Thanks
Minimum segments for arc fitting sets the minimum number of lines to check when arc fitting. Reducing the number may increase the aggressiveness of arc fitting but it may also make it less accurate.
Did you try taking min arc size in the post up to 0.1 or 0.2? That will probably solve your problem.
SheetCam doesn’t break arcs up. There are two possible reasons why the arcs are broken. Either your CAD package is breaking the arcs or the arcs are elliptical. G-code can only handle pure circular arcs so anything else has to be broken into lots of line segments.
Whenever you cut round a corner, SheetCam adds an arc around the corner. It is these little arcs that are causing your problems. Taking min arc size up will turn these little arcs into straight lines.
I did try increasing min_arc and that did help the problem. I had to go all the way to .2 which I’m afraid is going to effect accuracy.
I did notice one thing. Look at the two photos. One is of a recent job. Notice the number of points in the curve. Very high point density as compared to the other photo, which is from a job about a month ago.
Would this cause the problem I’m seeing? Is this a Sheetcam import thing or a DXF export thing. When I export from Rhino I have option. I’ve also attached a screen shot of that dialog.
Thanks
The problem is that you are using curves, not arcs. As I mentioned before, curves get broken up. In the export options there is an option to use CAM metric and CAM inch. Use one of those. The CAM modes in Rhino generally work very well.
I get the same results. See screen shot. I did notice in the DXF I used last month there seems to be arcs between the points where in the recent DXF’s there appear to be many straight lines between the points.
Is there a setting in Sheetcam that fixes this?
Have you got a dxf that produces arcs in the old version but lots of lines in the new version? If so, please post it or send it to me.
SheetCam does try to convert a series of lines into arcs where possible but on curves like yours it is difficult. Normally Rhino does a very good job of breaking curves into arcs. If you give me one of your drawings I’ll run it through Rhino and see if I can find the optimum settings.
All of my files are now importing into Sheetcam as curves or line segments. That’s not necessarily a bad thing. As long as Sheetcam outputs those as line segments and does not try to interpolate them as arcs and post G02/03 command, Mach just processes each G01 move and smooths them all out using CV.
The problem arises when we have a bunch of small arcs and lines strung together. That’s what happened on this last project.
See the attached files. One is a DXF that I generated a month ago. It cut smoothly with no jerking. The other is the DXF from the most recent project and also the Rhino file from that project. I’m beginning to think that maybe it’s the font that I used of something odd about this particular file.
Your input is greatly appreciated. I can’t seem to get anything now to export and import into Sheetcam that looks like that first photo.
I can’t seem to add more than one file, so I’ll email them.
Thanks