Issue in CAM dropping simple tool paths.

[infoWN88M]

Hi everyone,

I've been using Fusion for a few years now to create designs to cut on my CNC plasma.

Occasionally I get the old "Warning: One or more passes were discarded due to linking constraints." error code, but I can usually fix it by finding some fault in the file or my CAM setup.

There is a design that I have never been able to get to work though. It is a super simple design compared to some of the stuff I cut. I have tried everything, redraw from scratch, create a new plane above it then project the body and re extrude checking continuity in all lines, change all CAM settings, create an SVG from it in Illustrator then extrude the SVG.... I just can't seem to come up with a solution for this one. Ironically it will always cut the intricate paths, but it drops out two huge sections where there is no issues with lead in/out space. I can usually only get it to work by modifying the lead in/outs, kerf compensations etc... but it seems random, may work on one number but not another. But then I end up with three or more cut files to make the one part (one 'Main' cut file cutting all the parts at the settings I want, and then multiple other individual cut files to cut the parts that didn't work - usually with less than ideal machine settings to get it to work).

Any help would be appreciated to see where I am going wrong.

I'm sure it is something simple I've overlooked, but it would be good to learn what I have done wrong.

[engineguy · Accepted solution]

@infoWN88M 

Your issue seems to be with your Model, there are some very small/sharp corners around the large Italic "B" in the middle that are causing problems.

I put some small Fillets in those areas and it now will toolpath but I also had to select each small area one at a time, the "select all" by selecting the surface doesn`t seem to work on this file, maybe it needs some other work on the Model. I did notice that some of the lettering does not properly join both the outer and inner rings, maybe something there that requires attention ? 🙂

Anyway, have a look at the attached file, might work OK for you for now 🙂 🙂

[infoWN88M]

Hi engineguy,

Thanks for your help. I think why I was confused is that whenever I do a design with sharp internal corners, Fusion automatically generates a toolpath that it can successfully cut given the kerf width I have assigned for my tool. So if I were to have a very deep sharp corner, the tool just doesn't enter there and basically creates its own fillet when generating the toolpath losing some detail and smoothing it out.

I am specifically talking about cut paths, not pierces (it will just drop features that it cannot pierce inside of), due to the large size of this area I figured it would pierce no problems and then just smooth those corners out.

Just had me stumped because it has behaved like that (smoothing out its own paths) with several hundred files I've created of very complex nature scenes with sharp leaves etc.... but then this super simple one doesn't want to work.

As you say - some of the outer letters don't even contact the ring, or only just contact it (I only quickly redrew this file to post an example here) however it will successfully just smooth out that pocket and not drop the whole feature. Arguably some of the features in the outer ring that did create successful cut paths were significantly more difficult to enter than the cut paths around the 'B' that it dumped. Seems like two different behaviours in the same file.

Thanks for your help - if I have similar issues in the future I will have to be more specific with tidying details up. I appreciate your time.

[MattWynn]

@infoWN88M I don't know what is going on but there are many people recently having trouble using 2D profile for signs with inside circles!  And @engineguy a second time today finds a solution by tweaking the geometry.

Bad news is that this is a known issue with arcs like this.  Good news is that @luke.wielgus put in a bunch of time and has a fix that should be out in first major release next year.  

See Re: One or more passes were discarded due to linking constraints. CNC plasma. - Autodesk Community -...