Random Machining Grooves

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Random Machining Grooves

Postby chenryga » Mon Feb 18, 2019 9:21 am

Hello Everyone,

See the attached file.

Machining grooves.jpg


I have had this issue on several projects. There are random z-depth machining grooves. I have a HD4 machine and use V-carve Desktop. All software versions and controller firmware are up to date.

The issue occurs when using the Vcarve engraving tool path with the flat area clearance option. I am using a .125 EM and the CNC Shark-USB Contour Inch post processor. I have varied the raster angle and sometimes see improvements but other times not. The tool path preview always looks perfect in V-Carve.

The HD4 is less than a year old. I have confirmed the Z axis is "tight" and the ground wire is secure.

Any thoughts would be appreciated.

Chuck
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Re: Random Machining Grooves

Postby SteveM » Mon Feb 18, 2019 2:09 pm

If I am not mistaken, the proper post processor is Arch inches and not contour.
I would try that on a piece of scrap to see if that is the problem.
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Re: Random Machining Grooves

Postby OCEdesigns » Tue Feb 19, 2019 9:31 am

I am a newbie to this but so far the only post processor I have used is CNC Shark-USB Arch Inches and I have not had these grooves you show.
Shark HD4 Extended Bed, Water Cooled Spindle. VCarve Pro 9.5
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Re: Random Machining Grooves

Postby Bob » Tue Feb 19, 2019 12:01 pm

Chuck,
How closely were you watching when these grooves appeared?
Were you anywhere near the machine?

I have had grooves appear on material I was machining during a demo. In that case it was an easy catch. A customer was resting his hand on the gantry. This pressed the bit just a tiny bit further into the surface. When he looked closer the groove got deeper... The solution was to be sure that no one was within reach of the machine during setup and operation. No more grooves.

It's kind of nice when there is a simple solution.

Bob
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Re: Random Machining Grooves

Postby Bob » Tue Feb 19, 2019 12:07 pm

Chuck,
Also, if you're using the flat area clearance option there are sometimes grooves formed if the Z is not set accurately enough after a tool change.
Be sure to also check your bit clearance. If it's too low the bit may drag across the surface.
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Re: Random Machining Grooves

Postby chenryga » Wed Mar 13, 2019 1:52 pm

Thanks for the feedback everyone.

- The most likely cause is the post processor. I do a lot of 3D carvings and use the "Contour"post processor. I will try using the "arc" post processor and let you know how it worked.

Things that are not causing the issue include:
- Z height as I can wath the bit cutting and then drop down .020" or so for 2-3 passes and then return to the correct pocket height.
- leaning on the machine as it has happened with no one in the room

I am still wondering about static as it is happening more frequently in the winter months when humidity is low....

I'll post again after the PP trial...

Thanks again all.

Chuck
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Re: Random Machining Grooves

Postby chenryga » Wed Mar 13, 2019 2:56 pm

So.... The Arc PP is giving the same results with the Z axis dropping. The attached picture is from the first pass of the pocketing program. The results are identical with either post processor.

I attached the current results. I uploaded the tap file as well.

Still looking for root cause of this frustrating issue.

Any help is always appreciated.

Chuck

1 .125EM V-Carve 1 [Pocket].tap
(1.4 MiB) Downloaded 8 times
Attachments
Arc PP Results.jpg
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Re: Random Machining Grooves

Postby gwoodworks » Sat Mar 16, 2019 1:23 pm

I'm having the same problem, any help yet
Attachments
20190316_111141.jpg
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Re: Random Machining Grooves

Postby chenryga » Wed Mar 27, 2019 3:10 pm

gwoodworks,

I think I may have solved the issue. I discovered that the marks were being formed by the EM chattering. I decreased the cut depth/pass and slowed down the pass speed using the percentage slide on the control panel. I ran it at 25-30% and the results were very good. More machine time but far less sanding required. I think I'll let the machine worked overtime instead of me. 8-)

I hope that helps.....

Chuck
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