How selection planes work ?

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gdo35
Posts: 167
Joined: Wed Jan 25, 2012 7:25 pm

How selection planes work ?

Postby gdo35 » Fri Feb 24, 2017 9:46 am

Hi,

I want to be able to mill an XZ piece in freecad on XY in linuxcnc.

I tried to add a plane with Path->Partial Commands->Selection Plane thinking it could do the job.
But despite the plan I select, the path is still the same.

Could you give me help on how to use this Selection Plane feature ?

Thanks,
gdo

OS: Ubuntu 16.04.2 LTS
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.17.10236 (Git)
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chrisb
Posts: 1630
Joined: Tue Mar 17, 2015 9:14 am

Re: How selection planes work ?

Postby chrisb » Fri Feb 24, 2017 10:11 am

Perhaps it is not implemented yet. mlampert recommended to make a clone and turn it into the right plane. A pragmatic solution in the current state of development.
gdo35
Posts: 167
Joined: Wed Jan 25, 2012 7:25 pm

Re: How selection planes work ?

Postby gdo35 » Fri Feb 24, 2017 3:29 pm

Ok thank you.

Hard to find what is under development and what is not... :? Maybe it could be disable while.
sliptonic
Posts: 583
Joined: Tue Oct 25, 2011 10:46 pm

Re: How selection planes work ?

Postby sliptonic » Fri Feb 24, 2017 4:26 pm

Selection planes are nowhere near as useful as they sound :D

This is seriously old-school gcode stuff and hardly used anywhere anymore. A selection plane (G17/G18/G19) sets the modal mode for how the following arcs will be calculated. G17 is the default and causes all G2/G3 arcs to be calculated on the XY plane. A G18 move makes the arcs calculate on the XZ plane. This, I think, is the default for CNC lathe operations.

Selection plane ops in FreeCAD do only two things 1) confuse users 2) stick a G17/18/19 command into the output. It does NOTHING related to the orientation of the part.
gdo35
Posts: 167
Joined: Wed Jan 25, 2012 7:25 pm

Re: How selection planes work ?

Postby gdo35 » Sat Feb 25, 2017 1:02 am

Thank you sliptonic for these details.

Does it mean such a feature is not planed to be implemented ?
mlampert
Posts: 279
Joined: Fri Sep 16, 2016 9:28 pm

Re: How selection planes work ?

Postby mlampert » Sat Feb 25, 2017 1:57 am

gdo35 wrote:Thank you sliptonic for these details.

Does it mean such a feature is not planed to be implemented ?

What would you expect it to do?
chrisb
Posts: 1630
Joined: Tue Mar 17, 2015 9:14 am

Re: How selection planes work ?

Postby chrisb » Sat Feb 25, 2017 10:33 am

mlampert wrote:What would you expect it to do?
It could be sensible to allow XY, XZ, YZ or even an arbitrary datum plane as reference. It would belong to the job and all Path operations would operate on that plane instead of XY.
sliptonic
Posts: 583
Joined: Tue Oct 25, 2011 10:46 pm

Re: How selection planes work ?

Postby sliptonic » Sat Feb 25, 2017 3:21 pm

chrisb wrote:
mlampert wrote:What would you expect it to do?
It could be sensible to allow XY, XZ, YZ or even an arbitrary datum plane as reference. It would belong to the job and all Path operations would operate on that plane instead of XY.


This still doesn't make sense to me. Do you REALLY want operations operating on the YZ plane or do you want to rotate the part so the YZ plane maps to the XY plane? We absolutely need to build a rotation/translation tool to establish a 'work coordinate system' for the job but the operations will still operate in the XY plane with Z+ as 'up'.

The only exception I can see right now is a future lathe turning operation where arcs are normally calculated in the XZ plane and the Z axis runs through the spindle and tailstock.
GeneFC
Posts: 61
Joined: Sat Mar 19, 2016 3:36 pm
Location: Punta Gorda, FL

Re: How selection planes work ?

Postby GeneFC » Sat Feb 25, 2017 3:52 pm

I would love to have operations operating on the YZ plane. Unfortunately I do not have the money or space for a mega-K dollar machining center.

I suspect that most FreeCAD Path users have simple three-axis mills or two-axis lathes, with a single rotating tool axis. Some may also have a fourth-axis mill, but the tool rotation axis is still fixed.

In that case it seems there is little benefit to "selecting planes" in preference to making clones and positioning them as wanted. I use clones a lot. It takes a very short time to create and position a clone, probably no more than selecting a plane and positioning it correctly.

As discussed in this forum previously it is important to keep close track of the part origin and path origin to avoid unpleasant surprises when using the G-code on a machine tool. Simply selecting a working plane without adjusting the coordinates, or at least checking, would be a recipe for crashes.

I am not suggesting "closing the patent office," but this plane selection business seems like a pretty low priority, since it would not appear to add much value to what already exists.

Gene
chrisb
Posts: 1630
Joined: Tue Mar 17, 2015 9:14 am

Re: How selection planes work ?

Postby chrisb » Sat Feb 25, 2017 9:47 pm

sliptonic wrote:Do you REALLY want operations operating on the YZ plane

Definitely not!
or do you want to rotate the part so the YZ plane maps to the XY plane?
Yes, that's what makes sense to me, but see GeneFC's comment below
GeneFC wrote:In that case it seems there is little benefit to "selecting planes" in preference to making clones and positioning them as wanted. I use clones a lot. It takes a very short time to create and position a clone, probably no more than selecting a plane and positioning it correctly.
<snip>
... but this plane selection business seems like a pretty low priority, since it would not appear to add much value to what already exists.
I agree and I still have the opinion that we have a pragmatic solution and that there are other things to do. Sliptonic has mentioned some of them in another thread https://forum.freecadweb.org/viewtopic. ... 20#p161814.