Using ball-end tools in FreeCAD

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freman
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Re: Using ball-end tools in FreeCAD

Post by freman »

[Edit] this discussion led to some development issues which I raised in Path forum as a separate issue, since much of this thread is "help".
https://forum.freecadweb.org/viewtopic. ... ead#unread

I found I had to increase cyl radius to 80.5mm in the model. This may be due to residual metal left by piecewise approximation to the curve.

The result was adequate for the clamp I need but not that pretty as a finished part. It seems that the ball-end cutter does not like having its arse dragged backwards across the workpiece.

The problem is that every other pass is "conventional" and the result is not clean. The only path tool which consistently cuts in the same direction is spiral and sadly this seems to be the most buggy.

Since 3D surface only does linear cuts ,it would presumably be pretty simple to add an option to only work in one direction for consistent results.

I'm happy that ball-end tools are supported on 3D, using a straight mill was really a bit rough unless you did microscopic cuts, in which case you end up with literally hours of machining for a relatively simple form. If ball-end could be persuaded to alway cut in climb, I think it would give a really nice result.

BTW, the groove at the bottom was done by hand when I had the 6mm endmill mounted. I wanted to ensure that there was not a residual flat at the trough of the curve due to tool width.
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Last edited by freman on Mon Sep 02, 2019 7:02 am, edited 2 times in total.
RatonLaveur
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Re: Using ball-end tools in FreeCAD

Post by RatonLaveur »

Cool!

Don't forget, most people who want surfacing actually perform cross hatching for nicer results. So drop-cutter in X followed by in Y.
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freman
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Re: Using ball-end tools in FreeCAD

Post by freman »

thanks, do you mean machining pros face twice in opposing directions or is that a tip for getting better results from 3D-surface?

The planar surfaces came out perfectly with a single pass ( I used my awk script with if ( d>0 ) to isolate the top cuts ).

Climb vs conventional is not some pedantic tweak, it is basic machining, I think these path tools need to at least offer the possibility of a consistent cutting direction. Shame spiral is so flaky.
RatonLaveur
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Re: Using ball-end tools in FreeCAD

Post by RatonLaveur »

Yeah i mean machine once with X then machine a second time with Y.

You're right about Climb vs. Conventional: this should go to the PathWB development section.

You're right about spiral: same comment.

Keep chipping!
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freman
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Re: Using ball-end tools in FreeCAD

Post by freman »

Thanks I have posted a resume of this issue in PathWB.

I understood the cut you were recommending, my question was whether you meant this is stand practice in machining in general or just a tip which "most people" use on FreeCAD 3Dsurface.
chrisb
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Re: Using ball-end tools in FreeCAD

Post by chrisb »

It had escaped me, that this was in Help forum. Moved to Path.
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freman
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Re: Using ball-end tools in FreeCAD

Post by freman »

Thanks. Since there was a lot of "help" content here, I'd started a new topic in Path already to save devs having to trawl through 3 pages of comments to get to the relevant bits.

https://forum.freecadweb.org/viewtopic. ... ead#unread

Maybe best to continue the development aspects of this there.
RatonLaveur
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Re: Using ball-end tools in FreeCAD

Post by RatonLaveur »

hey freman,

Dropcutter in X then in Y is actually quite standard practice. To homogenize a surface texture.

Fancy CNC machinists actually would then kiss the surface with a more complex path if they want to achieve an artistic finish. But i've only seen these done on face milling and flat pockets, I have yet to see a 3D surface OP more complex than Waterline or Dropcutter.
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freman
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Re: Using ball-end tools in FreeCAD

Post by freman »

Many thanks for the clarification. I'll bear that technique in mind.

Had I done with the current direction switching I would have got a nice checker board finish ;)
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