Can't find the right toolpath

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TransJenna
Posts: 9
Joined: Fri Jan 27, 2023 11:59 pm

Can't find the right toolpath

Post by TransJenna »

Hi there, I am new to FreeCad, and it has been a fun adventure learning what I have learned so far - but I can't figure this out for the life of me.

Code: Select all

OS: Windows 10 Version 2009
Word size of FreeCAD: 64-bit
Version: 0.20.2.29177 +426 (Git)
Build type: Release
Branch: (HEAD detached from 0.20.2)
Hash: 930dd9a76203a3260b1e6256c70c1c3cad8c5cb8
Python 3.8.10, Qt 5.15.2, Coin 4.0.1, Vtk 8.2.0, OCC 7.6.3
Locale: English/United States (en_US)
I'm trying to mill the highlighted face, without milling away the little posts, but I can't figure out the right toolpath. Please help a newb out.


On a sidenote, how come the Mach3 post processor doesn't include feed speeds when generating g-code? I am using Mach3, but the linuxcnc post processor until I figure out what I am missing.

Thanks a lot,
-Jenna
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chrisb
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Re: Can't find the right toolpath

Post by chrisb »

Make a union of the posts and the block below and use the Path Pocket operation.
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GeneFC
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Re: Can't find the right toolpath

Post by GeneFC »

TransJenna wrote: Sat Jan 28, 2023 12:06 am
The basic problem is that your model is not made in a manner that works well for the Path WB.

Combine all the elements, Body, Cylinder, Cylinder001, etc. using the Part WB Boolean Union operation. Then direct the Job to the resulting Fusion object. Now all the components are joined into one cohesive unit.

Then you can select the Pocket Shape operation in the Path WB and process the flat surface without chopping off the cylinders.

This model would be best if made completely in one WB, such as Part Design. Then all the components would be automatically joined.

If this does not make sense keep asking questions.

[Chrisb was 3 minutes faster. :lol: ]

Gene
TransJenna
Posts: 9
Joined: Fri Jan 27, 2023 11:59 pm

Re: Can't find the right toolpath

Post by TransJenna »

Awesome! I'll do that and see if I can get it right this time. Thanks a lot for your responses!
TransJenna
Posts: 9
Joined: Fri Jan 27, 2023 11:59 pm

Re: Can't find the right toolpath

Post by TransJenna »

I was able to union the part and generate the g-code, but when I ran it (on a rather new g0704 conversion) I was left with a lip all the way around the part measuring upwards of .075".

I can't figure out where the inaccuracy is coming from, but I thought I would see if anyone has any idea.
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spanner888
Posts: 326
Joined: Tue May 28, 2019 10:51 am

Re: Can't find the right toolpath

Post by spanner888 »

Awesome cutting even if not want you want.

We need your updated design file to give you updated advice on the paths.

With regard to
doesn't include feed speeds when generating g-code
Have a look at rapids and feeds in https://wiki.freecadweb.org/Path_SetupSheet and https://wiki.freecadweb.org/Path_ToolController

The original file you posted does have feeds set, but not rapids. Look in the setup sheet, Tools tab, Defaults.

Also to be give more precise advice on the feeds query, once again, your updated file will help.
spanner888
Posts: 326
Joined: Tue May 28, 2019 10:51 am

Re: Can't find the right toolpath

Post by spanner888 »

...and forgot to ask above, if you simulated your gcode, either in FreeCAD, or an external tool, such, as CAMotics.
GeneFC
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Re: Can't find the right toolpath

Post by GeneFC »

TransJenna wrote: Sun Jan 29, 2023 3:11 am I was left with a lip all the way around the part measuring upwards of .075".
By default FreeCAD usually keeps the tool completely inside the edges of the model. That means that some edges and corners are not processed.

In the case of Pocket Shape the way to overcome that restriction is to check the "Extensions" box in the task panel. Then you can clear the edges.

The wording is not consistent throughout the Path WB. In some cases the correct solution is "Clear Edges", and in others it is called "Boundary Enforcement".

Make sure you check carefully when you use one of these options. It is possible that other areas of the model can be affected as well.

Gene
TransJenna
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Joined: Fri Jan 27, 2023 11:59 pm

Re: Can't find the right toolpath

Post by TransJenna »

Ok, here is the updated file. I see now in the simulation that a little lip would be left around the edges if Extension is not allowed.

1) If I allow extensions, will that cut into the cylinders as well, or just the boundary edge of the part?

2) Most importantly, The cylinders which should have been 1.125" diameter are actually machined at 1.082" diameter. I can't figure out why this is happening. I have my steps per inch set correctly in Mach3, I don't have any significant backlash in my machine - and yet it is undercutting. Instead of leaving a small lip of a few thousandths from not running extensions, it is leaving a nearly .075" lip on the top and right sides due to not cutting enough.

Could this be caused by the switch from imperial units to metric units by the post processor? I am loving my new machine, but if it moving .95" instead of 1.0" when I tell it to move 1.0" then I have a big problem. lol.
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GeneFC
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Re: Can't find the right toolpath

Post by GeneFC »

TransJenna wrote: Sun Jan 29, 2023 10:05 pm 1) If I allow extensions, will that cut into the cylinders as well, or just the boundary edge of the part?
I do not think so, but that is why I suggested that you check carefully. The extensions should show in a purple color in the task panel when enabled.
2) Most importantly, The cylinders which should have been 1.125" diameter are actually machined at 1.082" diameter.
The original cylinders are not 1.125, but rather some smaller number, 1.102. Better check your model. You can also examine the g-code to determine exactly what is being commanded. If the command does not match the final size then there is a problem with your machine or with Mach 3. Also, if the tool is not actually the quoted size that will affect the outcome.
Could this be caused by the switch from imperial units to metric units by the post processor?
No.

Gene
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