MeshCAM Pro Finish Pass Gouges Part - All Platforms

Software MeshCAM
1

I’m using the latest version of Mac MeshCAM Pro/Art.

I’m machining parts for my Nomad 883 Pro dust head. Two of the parts are (identical) brackets. The CAD and STL files were generated with BobCAD-CAM.

I could use the BobCAD-CAM CAM module to machine the part (there is a Nomad 883 Pro “post” available) but I wanted to make sure it could be machined with MeshCAM.

Here is the STL:

Spindle Bracket.stl (495.6 KB)

Here is the MeshCAM view of the part:

Overall.jpg1761×1035 700 KB

I set up the part, emitted the G Code, and started machining the part. When it finished, I found a gouge.

IMG_0296.JPG2448×3264 2.18 MB

The BobCAD-CAM CAM module machines this part correctly.

I went back to MeshCAM - I use MeshCAM Pro/Art - and ran the simulator. Sure enough, the gouge was there. Because the part is symmetric I never did a full 360; the front was fine and I assumed the back would be the same…

Weird that both sides are identical but a gouge is only on one side…

I ran 'topeScope on the STL and it didn’t find any errors and the part sure looks symmetrical and correct…

I’ve played with MeshCAM for quite some time and cannot find a set of parameters that removes the gouge.

Here is the simulation (the gouge is very obvious):

MeshCAM Pro Simulation.jpg1761×1035 550 KB

Here are the MeshCAM parameters (everything is at 10K RPM; stock is HDPE), I turned off waterline in this test… it still gouges:

MeshCAM Parameters.jpg770×677 319 KB

Here are the tool paths:

Tool Paths.jpg1761×1035 1.97 MB

Here is the simulation showing that the parallel finish is causing the gouge:

Parallel Finish.jpg1761×1035 1.11 MB

Does anyone know why MeshCAM is doing this? Is there a way to prevent this?

mark

2

@mark, I confirm the gouging. I can move the gouges around by playing with the stepover (.0121 vs .0120, for example) and the gouges occur in different places when I substitute Y parallel with various stepovers. I started to say I am suspecting the STL itself, but then I recreated your bracket from scratch and generated my own STL. Still gouges. There is something about this geometry that is confounding MeshCAM. I think this is a test case to send to Rob…

FWIW here is my reverse-engineered STL

spindle bracket randy.STL (589.2 KB)

For grins I also tried putting a small fillet (.001") around the top edge of the horizontal projection, that didn’t help.

Randy

2 Likes
3

There is something about this geometry that is confounding MeshCAM. I think this is a test case to send to Rob…

@Randy, thank you for restoring my sanity! :+1:

I also tried many parameter changes and nothing helped. Yes, some changes did move the gouge around.

I started to say I am suspecting the STL itself, but then I recreated your bracket from scratch and generated my own STL.

Thanks so much for the effort! 'topeScope is software to validate STLs and it said my STL was fine. Generating it from another CAD package proves it’s not BobCAD-CAM.

Off to Rob we go!

mark

4

It’s even worse than I realized. I reran MeshCAM Art/Pro, playing around and this happened:

YOW!.jpg1178×743 407 KB

Talk about gouging the part! There are now two on the bad side and it is now clear that the problem also happened on the other side, just not as severely.

Here were the parameters I used:

YOW! Parameters.jpg770×677 320 KB

mark

5

Yes, this alarms me, Mark. I always say that MeshCAM’s “job 1” is to never gouge the workpiece. Robert has always been good at this. And this is a pretty simple geometry. Something has apparently happened just recently that is letting this happen.

I’ll point out that when you add waterline, you can back off the parallel finishing itself. I usually use a parallel limit of 47 degrees and a waterline limit of 43 degrees, just to give a little overlap between the two processes. I did try this on your workpiece (and my reverse-engineered copy) but the parallel still glitched. And it is not an edge effect–the glitching is all along the fillet at the base of the vertical section.

The glitching is literally spikes. Down and right back up to the true surface. When you zoom in on the toolpath it is clear.

This is not good. And (in spite of the thread title) it is not just a Mac problem–I’m running build 27 under Win7.

Randy

6

I’ve been experimenting with various prototypes for the bracket and MeshCAM fails at the all - if a ball end end mill is used.

I gave up and switched to a substandard bracket - not as nice I would like but acceptable for the job. With no horizontal fillets, there is no need for a ball end end mill… and so things mill properly.

Besides this posting, I’ve send email to support at C3D and MeshCAM to notify them of the problem.

mark

P.S.

Here is another example a gouge using a design much simpler than I originally posted:

Gouge - Alternate Layout.jpg1593×1010 519 KB

7

mmmmm Not good, won’t upgrade my Mesh cam any time soon, wounder if the old version does the same thing?

8

@Randy showed that the problem is not specific to a platform - Mac and PC.

I have no knowledge of what older of MeshCAM versions do.

mark

9

@mbellon, since I loaded MeshCAM 5 to show the origin triad “fat” arrows, I decided to see what it does with your model. Thank you for sending it to me. Sure enough, MC 5 (build 45–the last one) still gouges at the base of the vertical wall.

I am flabbergasted. I have machined for years using MeshCAM, and can’t remember the last time I had a gouge that was not user error.

Mark, you seem to have found a simple geometry that stumps MeshCAM’s toolpath generation.

Finding and fixing the cause for this (since it could theoretically happen to anyone) should really be a top priority…

Randy

10

@mbellon, since I loaded MeshCAM 5 to show the origin triad “fat” arrows, I decided to see what it does with your model.

Great thing to try!

Sure enough, MC 5 (build 45–the last one) still gouges at the base of the vertical wall.

Ah… YOW! This has been a latent defect for a very long time!

I am flabbergasted. I have machined for years using MeshCAM, and can’t remember the last time I had a gouge that was not user error.

Me too! I’ve spent a large amount time (wasted) trying to work around it.

It looks like such a simple object, especially compared to the heavily filleted versions I made the initial discovery with.

Finding and fixing the cause for this (since it could theoretically happen to anyone) should really be a top priority…

Besides this posting, I sent email to C3D and MeshCAM support with the details and STL file.

@Randy, thanks for all your efforts. Now we wait…

mark

1 Like
11

watching this thread with baited breath

12

This has just come up on the MeshCAM forum also:: http://grzforum.com/viewtopic.php?f=11&t=15637

Randy

13

Robert, any news on this issue? An ETA on a fix?

mark

14

I have also experienced odd and unpredictable plunges on similar geometry where there’s a fillet between a horizontal and vertical or near vertical surface. I figured it was because I’m a neophyte who doesn’t have full mastery of machining domain. The plunge on this particular part was a separate move from the rest of the smooth 3d-contouring actions. In my case, the plunge did not ruin the part, but I have burned other parts because of this odd, unpredictable g-code artifact, that can usually be massaged away with different stepover settings. I’m certain that it occurs within g-code generated during “roughing” cycles. I can’t be much more specific than that, however.

IMG_2601.JPG3264×2448 1.78 MB

IMG_2781.JPG3264×2448 2.34 MB

1 Like
15

This is something I have never encountered, I just machined a tiny part that your gauge alone would have broke the part in two. Surely a solution exists and Rob will implement it.
Side note, looking at your settings, .04" stock to leave, that seems larger than necessary to me. What was the finishing pass like with that much material left to deal with?

16

This is something I have never encountered, I just machined a tiny part that your gauge alone would have broke the part in two. Surely a solution exists and Rob will implement it.

@Randy and I both see it and it clearly reproducible. @robgrz knows about the issue… we’re hope for a fix soon.

Side note, looking at your settings, .04" stock to leave, that seems larger than necessary to me. What was the finishing pass like with that much material left to deal with?

The part came out beautiful except for the gouges. Yeah, it should probably much smaller.

The point was that it gouged the part; I was playing with lots of parameters and that did it every time. :frowning:

mark

17

Here’s the part I was talking about Mark…

The emblem is cut along a spherical surface. You can see where some of the edges meet it gouges deeper than the adjacent areas. These gouges are not in the model.

20160225_131929.jpg1920×1080 136 KB
20160225_132117.jpg1920×1080 170 KB

The forum will not allow me to upload the .nc file so I tried to upload one of them with a .jpg extension but it doesn’t allow that either.

18

Could you please post the STL file? Recently, Robert made a change that allows a ZIP file to be posted - one can now bundle up things and add them all as one.

mark