pass depth and 3d finishing toolpath

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pass depth and 3d finishing toolpath

Postby petergmartin » Wed Jul 10, 2019 6:53 am

Hi

I'm having a problem with a steep sided 16mm triangular bowl shape that I'm trying to get cut on my cnc router.
My 6mm ball endmill only has a pass depth of 12mm.
The 2D toolpaths seem to understand pass depth but the 3D finishing toolpath just plain ignores it, so the preview looks great, I save the toolpath as gcode and put it on the CNC and it makes a right royal mess because it tries to move 12mm of teeth at a depth of 16mm and it can't because there's no teeth higher up to move material out of the way, and instead it moves the entire workpiece and pulls it from underneath the clamps, losing its X Y position and everything goes south.

Unsure what to do, other than redesign so the shape's sides are only 11-12mm deep.

I assumed the tool database entries related to pass depth were actually used by all the software that generates the toolpaths and I wouldn't have to worry about details like that at the design stage.

There really should be a warning or something.

Am I expecting too much of the VCarve Desptop version? Does this problem happen in the more expensive version or even in Aspire, or is it just the low-end version? Please no replies that say I should upgrade - that isn't going to happen as I suspect its all the same code-base.



Please help

thanks
Attachments
1.jpg
the preview
2.jpg
tool database entry for 6mm ball
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Re: pass depth and 3d finishing toolpath

Postby Adrian » Wed Jul 10, 2019 8:39 am

The finishing pass always cuts in one pass. It's important to use a tool in the roughing toolpath that is capable of removing as much material as possible. It's the same in Aspire.

There is a warning in the Help section for the finishing toolpath that covers it.

Note: The finishing toolpath is always a single pass, and it does not use the tool's pass depth. Please ensure that your Roughing Toolpath's Machining Allowance is set appropriately for the tool used in Finishing to avoid damaging the bit.
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Re: pass depth and 3d finishing toolpath

Postby petergmartin » Wed Jul 10, 2019 10:07 am

Ok thanks I must have missed that somehow in my angst. Looks like I need to buy a longer bit :wink:
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Re: pass depth and 3d finishing toolpath

Postby Leo » Wed Jul 10, 2019 12:43 pm

You should have TWO toolpaths available to you.

1) a ROUGHING 3D toolpath. This toolpath WILL use the pass depth set in the tool database and is used to do all the roughing out, and will leave a small amount for the finishing cut.

2) a FINISHING 3D toolpath. This is the one you are using. It assumes that you have already made the roughing cuts with the above ROUGHING toolpath and it ignores the path depth set in tool database.

There are times where you don't need a roughing toolpath and it is OK to use the finishing toolpath only, but in your case you may need to use both toolpaths.
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