How I mill a concave zone?

Here's the place for discussion related to CAM/CNC and the development of the Path module.
Giulio Buccini
Posts: 441
Joined: Fri Aug 26, 2016 9:07 pm
Location: Munich - Gemany

How I mill a concave zone?

Post by Giulio Buccini »

I'm thinking at the best strategy to mill many pipe collars that allows me to reduce the amount of manual operations and accurate position settings.

Here the question: there is any chance to use the Path WB to obtain a path trajectory like the one depicted from the yellow arrow in the image below?
Selection_7811.jpg
Selection_7811.jpg (18.63 KiB) Viewed 1049 times
My idea would be to get multiple pass (similar to the one above) to get a rough semi-circular shape, and then refine it with a ball-nose bit.
This approach would be ideal for me because I could use the two holes to screw the object down the fixture plate (provided with corresponding insert nuts).

Other approaches would force me to mill the collar from the side, and then move any collar to a vise for further machining of the holes. In such case, positioning should be very accurate in order to mill the holes at the center of the surfaces. Also the verticality of the piece should be checked with great attention.
I do not trust myself at all in such "high-accuracy" operations, and this stuff seems to me like a big PITA... :D

Any idea?
Attachments
mill_test.FCStd
(44.28 KiB) Downloaded 19 times
Samu
Posts: 34
Joined: Fri Jan 29, 2021 2:16 pm

Re: How I mill a concave zone?

Post by Samu »

The slot operation could be what you are looking for. Get a 12.1 mm ball end bit and you are good to go.
Attachments
mill_test_slotOP.FCStd
(56.88 KiB) Downloaded 13 times
Giulio Buccini
Posts: 441
Joined: Fri Aug 26, 2016 9:07 pm
Location: Munich - Gemany

Re: How I mill a concave zone?

Post by Giulio Buccini »

Slot operation doesn't fit my needs because it makes moves in only one direction until a certain deep. It doesn't produce a rough semi-circular shape with steps, but just a long and unidirectional slot.

My idea is to get a rough semicircle with an end-mill, and then refine it with a ball nose.
In other words, I would like to obtain something like the image below as first roughing pass:
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Selection_7813.jpg
Selection_7813.jpg (8.32 KiB) Viewed 900 times
Until now, what get more closer to my idea is the 3Dpocket operation, with Pattern = Line:
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Selection_7812.jpg
Selection_7812.jpg (37.89 KiB) Viewed 900 times
Unfortunately I didn't find a way to make the cuts longer in the Y-axis direction. If I increase the Pass extension the machined area grows in X and Y directions both... :(
Giulio Buccini
Posts: 441
Joined: Fri Aug 26, 2016 9:07 pm
Location: Munich - Gemany

Re: How I mill a concave zone?

Post by Giulio Buccini »

Also Pattern = ZigZag would be not so bad. But, again, it doesn't make a good work near the edges...
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Selection_7814.jpg
Selection_7814.jpg (40.3 KiB) Viewed 890 times
bmsaus4ax
Posts: 157
Joined: Sat Nov 14, 2020 9:16 pm
Location: Bargara, Queensland, Australia UTC+10

Re: How I mill a concave zone?

Post by bmsaus4ax »

Giulio Buccini wrote: Tue May 10, 2022 9:29 pm I'm thinking at the best strategy to mill many pipe collars that allows me to reduce the amount of manual operations and accurate position settings.

Here the question: there is any chance to use the Path WB to obtain a path trajectory like the one depicted from the yellow arrow in the image below?

Selection_7811.jpg

My idea would be to get multiple pass (similar to the one above) to get a rough semi-circular shape, and then refine it with a ball-nose bit.
This approach would be ideal for me because I could use the two holes to screw the object down the fixture plate (provided with corresponding insert nuts).

Any idea?
With a couple of minor tweaks the operation you have in your uploaded file can do it all in one pass.

Change to a ball endmill, the bigger the better that still fits into the groove. ( smaller is fine too but just means more step overs to get a fine finish )

Select Single Pass, ( multi pass will also work but is not needed ) The cuts will only be small, so very little load on the tool. A bit like adaptive clearing in 3D

Set Step Over small enough to almost eliminate the "peaks" in the overlapping cuts. (10 to 20% or more as a starting point, hence advantage of bigger cutter)

If you set the Sample Interval lower the path is calculated on a finer scale surface, may take longer to calculate, but not excessive for the benefit.

Select Boundary Enforcement = "true"

Set Boundary Adjustment = half the ball end mill diameter. (can be more, but half will cut right up to all the edges)

You can also set Zig-Zag pattern to minimise the number of moves, but this will alternate climb/conventional cuts. Not really an issue unless in hard materials where finish may vary. The Cut Pattern Angle is "0" for X-axis travel and "90" for Y-axis. ( Both settings in Show All in Data Tab Properties)

Also Note that the Simulator only correctly displays the material removal for the leading edge of the tool. A look at the path will show that it is correct to produce the required result.
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Code: Select all

OS: Ubuntu 20.04.4 LTS (ubuntu:GNOME/ubuntu)
Word size of FreeCAD: 64-bit
Version: 0.20.28810 (Git) AppImage
Build type: Release
Branch: (HEAD detached at 6f5a5a2)
Hash: 6f5a5a2019c586db63650713de860d3e810739d4
Python 3.9.12, Qt 5.12.9, Coin 4.0.0, OCC 7.5.3
Locale: English/Australia (en_AU)
Installed mods: 
  * Curves 0.4.2
  * CurvedShapes 1.0.3
Russ4262
Posts: 858
Joined: Sat Jun 30, 2018 3:22 pm

Re: How I mill a concave zone?

Post by Russ4262 »

Afternoon,
I recommend the 3D Surface with Multi-pass, 90 degree, line-based (Line, ZigZag, etc) pattern, 0.1mm Depth Offset so as not to disturb finish on top face of part as roughing pass, and disable Boundary Enforcement, with Boundary Adjustment set to -1% of tool diameter.

File and screenshot attached.

Cheers,
Russell

PS: I see bmsaus4ax has just posted with what looks like similar suggestion.

Code: Select all

OS: Windows 10 Version 2009
Word size of FreeCAD: 64-bit
Version: 0.20.28793 (Git)
Build type: Release
Branch: master
Hash: 72e91dbbca9094d9bd56b1d47a1eeaaeb7266849
Python 3.8.6+, Qt 5.15.2, Coin 4.0.1, OCC 7.5.0
Locale: English/United States (en_US)
Installed mods: 
  * FC_SU
  * Z_MacroStartup
Attachments
mill_test - Copy.FCStd
Copy of source file with 3D Surface operation example.
(53.64 KiB) Downloaded 15 times
Screenshot of 3D Surface op used
Screenshot of 3D Surface op used
Snip macro screenshot-24e85e.png (143.93 KiB) Viewed 857 times
Giulio Buccini
Posts: 441
Joined: Fri Aug 26, 2016 9:07 pm
Location: Munich - Gemany

Re: How I mill a concave zone?

Post by Giulio Buccini »

Thanks for the replies.
Tonight is very late and I'm almost exhausted, I will review your solutions tomorrow.

Again thanks!
Samu
Posts: 34
Joined: Fri Jan 29, 2021 2:16 pm

Re: How I mill a concave zone?

Post by Samu »

Giulio Buccini wrote: Wed May 11, 2022 9:42 pm Slot operation doesn't fit my needs because it makes moves in only one direction until a certain deep. It doesn't produce a rough semi-circular shape with steps, but just a long and unidirectional slot.
I am aware of that. With the slot operation, however, you can avoid the roughing cycle altogether if you use a ball end bit corresponding to the diameter of your half-circle. In my opinion it makes sense to reduce milling time in most cases and since you are planning to have a tool change for the finishing cycle anyway, why not use the largest possible toolbit right away? But that is a rather general discussion and not really related to the path workbench in particcular...
Giulio Buccini
Posts: 441
Joined: Fri Aug 26, 2016 9:07 pm
Location: Munich - Gemany

Re: How I mill a concave zone?

Post by Giulio Buccini »

Ok, I understand.
Neverthelees, I think my router is not rigid enough to drive a 12mm-dia ball-nose through the aluminum in "one shot"... :( :( :(
Samu
Posts: 34
Joined: Fri Jan 29, 2021 2:16 pm

Re: How I mill a concave zone?

Post by Samu »

Giulio Buccini wrote: Fri May 13, 2022 12:24 pm Ok, I understand.
Neverthelees, I think my router is not rigid enough to drive a 12mm-dia ball-nose through the aluminum in "one shot"... :( :( :(
You do not have to do it in one pass. You can set the depth of each pass to whichever depth you want. Say e.g. 0.5mm per pass (See file attached).

Code: Select all

OS: Ubuntu 20.04.4 LTS (ubuntu:GNOME/ubuntu)
Word size of FreeCAD: 64-bit
Version: 0.20.
Build type: Release
Branch: unknown
Hash: 1ca00446af87d31653a42174c74fc2c0a9ef3b79
Python 3.8.10, Qt 5.12.8, Coin 4.0.0, OCC 7.5.2
Locale: English/United States (en_US)
Installed mods: 
  * Render 2022.1.0
  * A2plus
  * CurvedShapes
  * FeedsAndSpeeds 0.4.0
Attachments
mill_test_slotOP.FCStd
(40.06 KiB) Downloaded 8 times
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