[Bryan Turner]

So I posted a "max cut" video in the Tormach forum to help me select the right feeds/speeds for a new part.

Then I go into SprutCAM (v9) to program my shiny knew knowledge and discover that the HSM paths have errors!

Attachment 270640

- Waterline Roughing with 3/8" endmill
- Stepover set to 0.09" (24%)
- Corner smoothing 0.4"
- HSM: Reduce on cleanup

Notice the difference in the orange boxes - on the left the paths are closer together (the correct stepover), but on the right they are farther apart (almost 50% stepover). I know my machine can't make that cut, and it is clearly an error in the path since it violates the 0.09" stepover.

I've tried several variations:
- Different corner smoothing, and no corner smoothing.
- Different stepover.
- Other HSM types: "island removing" and "with pocket step"

All of these show the same problem.
Any ideas?
--Bryan

[mountaindew]

Your machine can make a 50% step over cut! It depends on material and depth of cut, feed and speed.
My understanding is to avoid 50% step over and go 45 %- or 55%.+. when setting up step over in operations.
Back to question on hsm and sprut. Neither side looks correct to me and Im confused as to the view or what im viewing
Is there a hole for lead in or is there a plunge ramp in ? Also looks like a 2d feature and not a solid model
The pocket has a 3/8 radius at the points? and those paths also look way off on both sides. I need better pictures and more info to help.
md

[tmallard450]

Ive noticed Sprut will make depth and step over lower if it can not calculate a nice even number to get to the target surface. The HS tool path is all about constant tool engagement. Ive noticed it does alter how it cuts depending on where the cutter entered the work zone. But your picture does look odd maybe its a graphics card display issue. Post the program to a code back plotter to see if the same issue show up.


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[Bryan Turner]

Apologies if the context was confusing! This is definitely not model related, nor a graphics error, it is a path generation error.

I'm programming an HSM tool path (3/8" cutter, 0.5" DOC, 0.09" WOC) using SprutCAM's Strategy->High speed cuts->reduce on the cleanup. I was expecting to see it engage the cutter at a regular step over (0.09" in my case). Luckily noticed it has decided to engage the cutter at close to 50% stepover, which would snap my endmill at this depth!

I then went about trying to discover why it was generating a toolpath incorrectly. Re-jiggering the parameters does not seem to affect the error.

I went back to Adobe and exported only the shape to verify that it is actually something about the path, not the model or parameters. To verify that fully, I then drew a copy of the shape using only straight lines in SprutCAM's 2D mode and ran both shapes with the same parameters. This was the result:

Attachment 270878

Top: Shape drawn with straight lines, no error (left and right sides both have nice, even stopover).
Bottom: Shape drawn with curves imported from Adobe. Left side is correct (almost exactly the same as the top shape), but the right half is obviously taking heavier cuts.

I also recreated the straight-line version of the shape in Adobe and it works correctly, so it's not the export/import that is causing it either.
Must be something to do with the curves..
--Bryan

[tmallard450]

Bryan did you or your customer draw this shape using splines in Adobe? Ive experienced many strange things when using splines instead of arcs when exporting from cad to cam. The splines get chopped up into a billion little segments and sometimes throws messes with the computer.


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[Bryan Turner]

Good to know about the splines!

I'm guessing it's made of splines - I used the pen, circle, and rectangle tools to draw shapes and combine them with "union" and "minus front" pathfinders. If my reading is correct, these are exported as bezier curves (splines) and you're saying these may be causing issues with the CAM?

Is there a way to export as arcs only?
--Bryan

[tmallard450]

The cam programs get all hung up because in reality your controller can only make straight line and arc movements. When you are saving the file to iges formatt see if there are options to define he minimum segment length or to force it to make arcs. Thats at least how it works in solidworks. But if your drawing using just circles or 3point arcs you should be good.


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[danh818]

Don't forget the 'Sew Faces' and 'Join Curves' functions they can sometimes help fix import errors.

[mountaindew]

I was thinking its a model or iges file export error / anomaly when looking at your picture of model and tool paths. I went and looked at some similar parts I have done and hsm function had no problem creating all kinds of tool paths. Very symmetrical in how it sorts and determines entry and exit and each change of depth. These were pretty complex parts with different pockets at different depths and faces and I was even surprised at its strategy. Lots of tool movement to warm x,y, axis motors. I spend a great deal of time in sprutcam and must admit I don't use those functions much because they are pretty new.
Picture of test example




In short you will find all kinds of little things when moving graphics files like this. There is a section in sprutcam help on iges standards it follows. Reading this can help set other programs to provide better data that it can follow. "maybe" I find all sorts of problems with spherical objects, open end slots on certain planes and inside swept radius curves also import with anomalies. I see this in other peoples work so I know its not just my cad system and I expect some problems because I use older vintage cad with questionable export igs standards.

md