Spiral pattern - for what?

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Giulio Buccini
Posts: 123
Joined: Fri Aug 26, 2016 9:07 pm

Spiral pattern - for what?

Postby Giulio Buccini » Fri Feb 14, 2020 2:00 pm

Hi folks,

I appreciate the various patterns available when milling a pocket; just a question: what is the intended use of the "spiral" pattern?
When I apply it on a small pocket I get two things:

- an "external" outline milled
- an "internal" outline milled

As I understand, the internal zone of the selected pocket is not cleared, it stay untouched... so? I'm missing something? :oops:
Selection_929.jpg
Selection_929.jpg (67.06 KiB) Viewed 206 times
chrisb
Posts: 22322
Joined: Tue Mar 17, 2015 9:14 am

Re: Spiral pattern - for what?

Postby chrisb » Fri Feb 14, 2020 3:48 pm

Looks to me like a bug. Perhaps the opposite of the far too narrow inner paths when using "offset"? These come from the third party library libarea, as far as I know.
m0n5t3r
Posts: 97
Joined: Fri Feb 03, 2017 2:55 pm

Re: Spiral pattern - for what?

Postby m0n5t3r » Fri Feb 14, 2020 4:23 pm

in theory it should do a spiral path like https://www.forum.linuxcnc.org/media/ku ... pirals.jpg; in practice, it's been like this since I can remember :-/
herbk
Posts: 1731
Joined: Mon Nov 03, 2014 3:45 pm
Location: Windsbach, Bavarya (Germany)

Re: Spiral pattern - for what?

Postby herbk » Fri Feb 14, 2020 4:42 pm

Looks to me like a bug.
Yes... But it seams not to be at round pockets (i cut a few last week, using spiral pattern), where it works like expected.

Both pathes are made with the same step over.
spiral.jpg
spiral.jpg (74.55 KiB) Viewed 179 times

Edit:

But also Offset has a problem with rectangular pockets...Pic is at 100% step over, is it less then 100%, the distance between the pathes are some kind of randomly.
offset.jpg
offset.jpg (92.27 KiB) Viewed 174 times
Last edited by herbk on Fri Feb 14, 2020 4:56 pm, edited 2 times in total.
Gruß Herbert
RatonLaveur
Posts: 464
Joined: Wed Mar 27, 2019 10:45 am

Re: Spiral pattern - for what?

Postby RatonLaveur » Fri Feb 14, 2020 4:43 pm

Same experience. Been that way since i started with path at V0.17.
Herbert that circular path is not a spiral. Check transitions.
herbk
Posts: 1731
Joined: Mon Nov 03, 2014 3:45 pm
Location: Windsbach, Bavarya (Germany)

Re: Spiral pattern - for what?

Postby herbk » Fri Feb 14, 2020 4:59 pm

RatonLaveur wrote:
Fri Feb 14, 2020 4:43 pm
Same experience. Been that way since i started with path at V0.17.
Herbert that circular path is not a spiral. Check transitions.
Yes you are right... Its like Offset without Up and down...
Gruß Herbert
Giulio Buccini
Posts: 123
Joined: Fri Aug 26, 2016 9:07 pm

Re: Spiral pattern - for what?

Postby Giulio Buccini » Fri Feb 14, 2020 5:17 pm

Uh!
So is not a feature... it is a bug! :lol:

I attach the cad file. I get the same result with FreeCAD 0.18 and 0.19 both.
Attachments
mill-patterns-test.FCStd
(39.37 KiB) Downloaded 3 times
Giulio Buccini
Posts: 123
Joined: Fri Aug 26, 2016 9:07 pm

Re: Spiral pattern - for what?

Postby Giulio Buccini » Fri Feb 14, 2020 5:19 pm

P.S.
I just moved the milling origin to the corner of the block by using the "Setup" tab after double-clicking on the "Job" item.
m0n5t3r
Posts: 97
Joined: Fri Feb 03, 2017 2:55 pm

Re: Spiral pattern - for what?

Postby m0n5t3r » Fri Feb 14, 2020 7:14 pm

Heh, so while checking various shapes I learned something new: found the "keep tool down" option for pocket / 3d pocket, and figured that it only works up to a certain step over percent (70 or 75%, depending on the shape), then it starts retracting; it's not a spiral, but it seems better than zigzag / zigzagoffset anyway.
RatonLaveur
Posts: 464
Joined: Wed Mar 27, 2019 10:45 am

Re: Spiral pattern - for what?

Postby RatonLaveur » Fri Feb 14, 2020 10:23 pm

Hehe the more you know... Still, and I'm being annoyingly pedantic here...not a spiral path. You almost don't see the difference with a standard mill, except maybe a little cycle time and tool wear which most hobbyist won't ever notice...but with an industrial laser you do see it. A lot.