[SOLVED] Cannot modify the step-over of the helix

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bmsaus4ax
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Re: Cannot modify the stepover of the helix

Post by bmsaus4ax »

Giulio Buccini wrote: Wed Apr 20, 2022 11:04 pm
From where you know such secrets???
I've found with FreeCAD as it is developing you have be that annoying kid who pushes every button to see what it does. The documentation does not keep up with the progress.
A question: what is the difference between "start side" = Inside or Outside for cylindrical pockets? I see no difference in the resulting toolpaths in my example (you find the attached file some posts above).
If you slow down the simulation with the Speed bar to near zero you should see the paths start near the centre and progress outward for Start Inside, and hole edge to centre for Start Outside.
Last edited by bmsaus4ax on Wed Apr 20, 2022 11:25 pm, edited 1 time in total.
bmsaus4ax
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Re: Cannot modify the stepover of the helix

Post by bmsaus4ax »

chrisb wrote: Wed Apr 20, 2022 11:20 pm
bmsaus4ax wrote: Wed Apr 20, 2022 10:45 pm The start radius parameter is a bit odd in that is seems to be the radius of the remaining centre rather than the cutter path radius. Start Radius =1 will leave an island in the middle of the hole!
A start radius of 0 or even less than 0 should be possible.
Agreed, that could possibly be called a bug
tigermm
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Re: Cannot modify the stepover of the helix

Post by tigermm »

chrisb wrote: Wed Apr 20, 2022 11:20 pm
bmsaus4ax wrote: Wed Apr 20, 2022 10:45 pm The start radius parameter is a bit odd in that is seems to be the radius of the remaining centre rather than the cutter path radius. Start Radius =1 will leave an island in the middle of the hole!
A start radius of 0 or even less than 0 should be possible.
In my build at least, 0mm is the minimum and leaving it set there shows a bit of a bug.

I'm doing 13.6mm holes helix'd with a 6mm bit, but at start radius=0mm I get only one path and the centre is not cleared.
Setting it to 0.01mm gives me the second path that I expected.
File attached, would be interesting to see if this happens with other builds.

Code: Select all

OS: Windows 10 (10.0)
Word size of FreeCAD: 64-bit
Version: 0.20.28567 (Git)
Build type: Release
Python 3.8.13, Qt 5.12.9, Coin 4.0.0, OCC 7.5.3
Locale: English/New Zealand (en_NZ)
Installed mods: 
  * A2plus
  * CurvedShapes
  * Curves 0.4.2
  * sheetmetal 0.2.49
Attachments
Kawi front bearing plate with elec mount V2.FCStd
(561.05 KiB) Downloaded 18 times
tigermm
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Re: Cannot modify the stepover of the helix

Post by tigermm »

Giulio Buccini wrote: Wed Apr 20, 2022 11:11 pm
Giulio Buccini wrote: Wed Apr 20, 2022 11:04 pm A question: what is the difference between "start side" = Inside or Outside for cylindrical pockets? I see no difference in the resulting toolpaths in my example (you find the attached file some posts above).
Got it! :D
Changes the milling order of the helixes, i.e. start side = Outside starts milling the helix more far away from the center first, and then the other ones more close to the center.
So unless you're doing blind holes, the inner paths are useless in a "start outside" operation as the outer paths will cut right through and leave nothing supporting the pillar in the middle :shock:
tigermm
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Re: [SOLVED] Cannot modify the step-over of the helix

Post by tigermm »

I suddenly though "I wonder how an adaptive path would look for these holes" and I think the answer is "better" due to more radial cutting rather than plunge like cuts.
Gonna try it on 2 of these holes and see what the difference in finish is vs pure Helix.
Attachments
Kawi front bearing plate with elec mount V2.FCStd
(113.45 KiB) Downloaded 18 times
tigermm
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Re: Cannot modify the stepover of the helix

Post by tigermm »

tigermm wrote: Mon May 02, 2022 12:42 am So unless you're doing blind holes, the inner paths are useless in a "start outside" operation as the outer paths will cut right through and leave nothing supporting the pillar in the middle :shock:
OK I feel like I'm spamming this thread now :oops: but this may be useful to someone in the future.

A fix to the above for larger circles is to use a normal internal profile operation, then give it a ramp entry dressup with the helix method.
This allows you to add tags to hold the centre portion which would otherwise be flopping about. Tags can't be added with the normal Helix operation.
I've done this with the 70mm central hole in the attached file as I don't want to spend the machine time to clear the whole thing.

The step down value of the original profile operation will give you the Z feed per turn of the helix.
Attachments
Kawi front bearing plate with elec mount V2.FCStd
(103.82 KiB) Downloaded 25 times
chrisb
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Re: Cannot modify the stepover of the helix

Post by chrisb »

tigermm wrote: Mon May 02, 2022 12:38 am In my build at least, 0mm is the minimum and leaving it set there shows a bit of a bug.
That's exactly the bug I was talking about. Would you mind creating a bug report? The profile operation is suitable for your special issue but doesn't serve as a general solution.
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sliptonic
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Re: [SOLVED] Cannot modify the step-over of the helix

Post by sliptonic »

Need some eyeball on this.

This is a revised helix generator. You can just overwrite the version in your /Mod/Path/Generators folder with this one and restart FreeCAD. It will fail the Path unit tests but works for testing in the application.

This simplifies the logic for calculating the offsets.
1) If the tool is less than the hole diameter but more than the half the radius, a single helix is generated.
2) Otherwise, it generates stepover from the inner radius to the outer.

My concern is that with this approach, the tool NEVER crosses the center point. It can (probably will) leave a small bump in a blind hole.
The old way didn't do this but created more stepovers than necessary.

I'll prepare a pull request and modify the unit tests if everything looks good.
Attachments
helix_generator.py
(8.7 KiB) Downloaded 18 times
Giulio Buccini
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Re: [SOLVED] Cannot modify the step-over of the helix

Post by Giulio Buccini »

Hi,
thanks for the new code!

I'm overload at my job, so minimal free time. This is a stressed period.
I will test it when it will be possible.
bmsaus4ax
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Re: [SOLVED] Cannot modify the step-over of the helix

Post by bmsaus4ax »

sliptonic wrote: Sun May 15, 2022 6:22 pm Need some eyeball on this.

My concern is that with this approach, the tool NEVER crosses the center point. It can (probably will) leave a small bump in a blind hole.
The old way didn't do this but created more stepovers than necessary.
Looks good when I tested.

May need to modify the .ui file when integrated.
@ Default of Outside overwrites Def: of Inside in generator.
@ Percentage step over to 100% as default ? , 1% as at present too fine. Units mismatch?
@ CCW to default if Inside becomes default ?

Can a first pass of the method be append() 'ed with a small offset, based in first Index of list (radii) before calling the extend() ?
I have not been able to but low time Python.

For the bump: square corner tools will only suffer from corner wear or lack of rigidity, shaped edge tools easily corrected with plunge to depth on centre.
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