Path 3D pocket removing too much material

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fencian
Posts: 3
Joined: Sun Jan 16, 2022 1:59 pm

Path 3D pocket removing too much material

Post by fencian »

sloped_edge.FCStd
(33.79 KiB) Downloaded 27 times
Hi

I have a complicated part that will require CNC machining on one face and then flipping over to complete the opposite face. The path 3D pocket tool is creating an internal path as expected but also a path on the opposite face. The simplified attached file shows a sloped surface with material that needs to be removed from above and below. However when I use 3D pocket for the top face it generates a tool path for the top and bottom faces. Is there a way of stopping 3D pocket from generating a tool path on the opposite face?

OS: Windows 10 Version 2009
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.24291 (Git)
Build type: Release
Branch: releases/FreeCAD-0-19
Hash: 7b5e18a0759de778b74d3a5c17eba9cb815035ac
Python version: 3.8.6+
Qt version: 5.15.2
Coin version: 4.0.1
OCC version: 7.5.0
Locale: English/United Kingdom (en_GB)

Thanks
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GeneFC
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Re: Path 3D pocket removing too much material

Post by GeneFC »

fencian wrote: Tue Jan 18, 2022 9:13 am Is there a way of stopping 3D pocket from generating a tool path on the opposite face?
The simplest thing would be to switch to the 3D Surface operation. You shape is not really a "pocket". The Pocket operation can be made to work, but the Surface is made for this type of shape.

Gene
fencian
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Re: Path 3D pocket removing too much material

Post by fencian »

Thank you for the help. I've applied it to my design and it has solved the problem. It does however result in rough edges which I've struggled to clean using other operations. This was the main reason I previously tried 3D surface but gave up on it hoping that 3D pocket would work, which it did until I added the internal sloping edge, which it failed with.


Bottom cover.png
Bottom cover.png (35.62 KiB) Viewed 1803 times
Bottom cover 3D surface.png
Bottom cover 3D surface.png (70.07 KiB) Viewed 1803 times
Bottom cover cut material.png
Bottom cover cut material.png (46.31 KiB) Viewed 1803 times


What operations would you recommend to clean the internal edges after the 3D surface operation, particularly around the three curved faces at the front?
GeneFC
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Re: Path 3D pocket removing too much material

Post by GeneFC »

First, I do not fully trust the simulator for complex operations like 3D Surface. It is probably correct in this case that the ends of the pockets are not fully cleared out.

You will need to play with options like Boundary Enforcement and Stock size. I do not believe that extensions are included in the 3D Surface at this time. Also, go into the Property panel below the model tree. Then right click and select Show All. A number of additional parameters will be shown. Most will not be relevant in this case, but you can experiment.

If you can attach a sample file I am sure someone here will take a crack at it.

Gene
chrisb
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Re: Path 3D pocket removing too much material

Post by chrisb »

Coming back to OP: Even if I make it a real pocket, 3DPocket does it wrong. Regression or mistake?
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fencian
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Joined: Sun Jan 16, 2022 1:59 pm

Re: Path 3D pocket removing too much material

Post by fencian »

There definitely appears to be a problem/limitation with 3D pocket, which is beyond my capabilities at the moment. I've spent too much time trying to resolve this problem and I can't get 3D surface to do what I want either.

I've gone back to using the 3D pocket operation but removing the bottom sloping face, which is what it struggles with. It's a bit long winded but does produce results close to what I was hoping for.

I start with the design as before but without the bottom sloping face, so that the bottom face is completely flat over the whole area of the design. I then use several 3D pocket operations to generate the gcode for the top side milling.
Bottom cover top CNC paths.png
Bottom cover top CNC paths.png (58.19 KiB) Viewed 1633 times
I then flip the design over, make it solid, add the bottom sloping face and then use a single 3D pocket operation to generate the bottom side gcode.
Bottom cover bottom CNC paths.png
Bottom cover bottom CNC paths.png (32.33 KiB) Viewed 1633 times
Although not ideal because I have to change the design between generating the top side gcode and bottom side gcode, it does appear to work and that is the most important thing and I can get on with making things.
Russ4262
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Re: Path 3D pocket removing too much material

Post by Russ4262 »

Evening,
Fix in the mix as PR #5424, Path: Fixes 3D Pocket overcut on underside of selected faces.
Similar report in 3D pocket anomaly thread a while back.

Russell
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