Creating a toolpath to machine a series of round pegs to the same height

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ITmaze
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Creating a toolpath to machine a series of round pegs to the same height

Post by ITmaze »

I'm posting this in the Development -> Path/CAM area, since it appears to be the only Path specific area on the forum, forgive me if this is the wrong place to ask.

I'm attempting to create a tool path to machine the mounting points on a CNC table. There are 22 "cylindrical pegs" that need to be machined to the same height. I've created a model to represent these surfaces. They are dotted throughout a rectangular area.

The requirements for my tool path are:
  • There can be no Z-travel during the operation, that is, the pegs are all above the underlying surface and to improve flatness I want to leave the Z-height static throughout the whole operation.
  • It doesn't spend 99% of the time cutting air.
  • It needs to climb cut for all material removal.
I have attempted a great many things and I'm no closer to success:
  • I've modelled a single circular cylinder and I can create a spiral path across that. If I attempt to do that across all 22 surfaces, it takes over an hour to generate and the Z-axis on the tool path lifts and descends between each cylinder.
  • I can create a cylinder that encloses the entire area and generate a spiral, but it exceeds the working area of my machine.
  • I've modelled the enclosing box, but I cannot generate a surfacing or pocketing operation using a spiral across a square surface, it only draws the two outside paths. I came across another user reporting that behaviour in 2019, but there were no responses to their post.
  • If I use any other surfacing method, the Z-travel changes between steps, the CNC spends most of its time cutting air or the cut isn't a climb cut for all material removal.
I've attempted to find documentation on creating surfacing paths but my Google-fu seems to be failing me in this regard.

I'm currently using AppImage of FreeCAD v20, Revision 26651 (git).

Is there any documentation that I might read to understand this; should I be using a different version; or is this currently unsupported?
GeneFC
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Re: Creating a toolpath to machine a series of round pegs to the same height

Post by GeneFC »

ITmaze wrote: Wed Jul 06, 2022 3:20 am [*] It doesn't spend 99% of the time cutting air.
If this is a one-time operation just do it. It will take a lot less effort than trying to come up with the best model.

If you need to repeat, then add some more detail, including a file showing the model.

It is possible that something as simple as an array would help.

Gene
ITmaze
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Re: Creating a toolpath to machine a series of round pegs to the same height

Post by ITmaze »

This will need to be done in several steps and taking two hours per step seems just a little excessive.

As for a model, I've attached the OpenSCAD model. When you import it into FreeCAD, the "difference" is the holes, the "union" is the pegs.
Attachments
platform.scad
SnapMaker A350 build platform model
(3.79 KiB) Downloaded 20 times
Russ4262
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Re: Creating a toolpath to machine a series of round pegs to the same height

Post by Russ4262 »

Evening.
I downloaded your SCAD file above and imported it into FreeCAD. I am not sure about what your goal is. Is it something similar to the attached screenshot - face each of the pegs?

Russell

Code: Select all

OS: Windows 10 Version 2009
Word size of FreeCAD: 64-bit
Version: 0.21.29434 +11 (Git)
Build type: Release
Branch: master_prs
Hash: 7007fc82c3e7a53608d47fd9c2f65d22fb23b5e3
Python 3.8.10, Qt 5.15.2, Coin 4.0.1, Vtk 8.2.0, OCC 7.6.2
Locale: English/United States (en_US)
Installed mods: 
  * FC_SU
  * PathPlus
  * Z_MacroStartup
Attachments
platform_imported.FCStd
(54.77 KiB) Downloaded 17 times
Snip macro screenshot-b05f56.png
Snip macro screenshot-b05f56.png (109.67 KiB) Viewed 1088 times
ITmaze
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Joined: Fri Dec 17, 2021 11:50 pm

Re: Creating a toolpath to machine a series of round pegs to the same height

Post by ITmaze »

The operation you show has Z-travel between each face. This is what I need to avoid.
chrisb
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Re: Creating a toolpath to machine a series of round pegs to the same height

Post by chrisb »

If it is just these holes, you can create one op for each hole. That could take less time than waiting for the mill - and it is a good exercise :) .
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GeneFC
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Re: Creating a toolpath to machine a series of round pegs to the same height

Post by GeneFC »

ITmaze wrote: Thu Jul 07, 2022 7:42 am The operation you show has Z-travel between each face. This is what I need to avoid.
You can set the Start Depth, Final Depth, Safe Height, and Clearance Height to zero, or at least all the same value. Check the resulting code to make sure the Z-travel makes sense to you. The actual machine cutting height needs to be checked, of course, but it is no problem to generate G-code with no Z-travel.

Gene
ITmaze
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Re: Creating a toolpath to machine a series of round pegs to the same height

Post by ITmaze »

GeneFC wrote:You can set the Start Depth, Final Depth, Safe Height, and Clearance Height to zero, or at least all the same value
Thank you for that suggestion. I've spend a little while investigating how to do that, but discovered that the values I'd like to set are greyed out and not editable. No doubt I'm missing some salient point in how to achieve that.
GeneFC
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Re: Creating a toolpath to machine a series of round pegs to the same height

Post by GeneFC »

ITmaze wrote: Sat Jul 09, 2022 2:16 am but discovered that the values I'd like to set are greyed out and not editable.
They should editable either in the task panel or in the property panel shown below the model tree.

You probably need to select the fx icon at the right side of the data box and then select "Clear". I don't know why the numbers often appear gray, but they still can be edited.

You can also set the default values in the Job setup or in the setup sheet.

Gene
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sliptonic
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Re: Creating a toolpath to machine a series of round pegs to the same height

Post by sliptonic »

GeneFC wrote: Sat Jul 09, 2022 3:16 am
ITmaze wrote: Sat Jul 09, 2022 2:16 am but discovered that the values I'd like to set are greyed out and not editable.
I don't know why the numbers often appear gray, but they still can be edited.
If the numbers are grey and the expression icon is blue, it means there's an expression generating the currently shown value. As GeneFC said, you need to clear the expression before you can enter simple values.
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