How selection planes work ?

[gdo35]

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)
Build type: None
Branch: master
Hash: dd20ba3d068c4a0903417d93144f8ac7fed068e9
Python version: 2.7.12
Qt version: 4.8.7
Coin version: 4.0.0a
OCC version: 6.8.0.oce-0.17

[chrisb]

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]

Ok thank you.

Hard to find what is under development and what is not... Maybe it could be disable while.

[sliptonic]

Selection planes are nowhere near as useful as they sound

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]

Thank you sliptonic for these details.

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

[mlampert]

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]

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]

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]

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]

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

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.