Tool path on wrong height

[CADetInTraining]

Heya,

I wanted to try using CNC milling with help of FreeCAD. Heard it's quite powerful.
So I got this very simple "test" model, little coaster.

On the CNC I got 6mm board.

Coaster is 4mm thick.

In Job Setup, I setup a "cylinder" that's 6mm thick and 58.625mm radius.

I setup Mill Face Operation as the first thing, to mill it down to 4mm. But trying to run it on CNC (and looking at Gcode):
G0 Z11.000
G0 X0.062 Y97.893
G0 Z9.000

So it's skipping around at 11mm, then going down to 9mm to start milling operation.
That's not going to work...

Where did I go wrong please ?

[legros]

hello, 11 is your Clearance Height and 9 is your Safe Height
so far everything is fine, then never trust freecad and always check your quotes
13800mm/min nice machine that you have it must have good fixation to the ground

[CADetInTraining]

thanks Legros, I noticed issue with feedrate too - but I still don't think that solves my problem

[legros]

Hello,
you have a stock of 6 mm, a Clearance Height of 5 mm and a Safe Height of 3 mm (6+5=11 6+3=9) (I have always been good at calculations)
you made your Z0 on the machine table so the heights are correct
personally I make my 0 piece in its center and Z0 on the upper part, 3d probe, but that is according to that machine

[CADetInTraining]

Thanks Legros,

Those calculations make sense - but I presume FreeCAD doesn't use right terminology or just doesn't let me know that I got this wrong.
I only have a Z probe.
I'd love to have 0 in the middle of the piece too, but I don't know how to force FreeCAD to do it. In other programs it's just a setting change in one place, little button to press. That's it.

I've been looking at the diffs of Document.xml in the project bundle, I see following changes (skipping some):
- your build is 0.21R33694 , vs mine 0.21R33668 . Who knows why I am just using whatever is downloadable on the main site, cos dev builds crash too much
- Pocket_Shape and Pocket_Shape003 operations were removed
- you removed two constraints from one of the sketches and thus changed geometry a little bit
- HorizRapid and VertRapid were reduced (good stuff, I did it in my version later on too)

Milface :
- Property Active was changed to true
- property AreaParams was changed too, AngleShift changed
- you've changed ZigZagAngle to 90 from 45

Pocket_Shape001 :
- PocketMode changed from 2 to 4
- Angle changed from 45 to 0
- KeepToolDown changed to true
- MinTravel changed to true
- OffsetPattern changed to 2 from 1
- PathParams threshold added with value 4.002
- StartDepth changed to 6
- ZigZagAngle changed to 0
-

Profile:
- FinalDepth changed to 0 from OpFinalDepth


I think that's all of them.

I still don't understand why these changes were needed in the first place, and how can I make this more automated in the future - so I don't have to make random changes in numbers.
You'd think that defaults were sensible, but for instance I find that the depth-per-pass is the size of the tool. This might be true for big-boy CNC machines, but not for a little 3020 I got .

[legros]

Hello,
as I said previously, do not trust freecad and always check the quotes,
I'm not trying to tell you how to do it but how I would have done it
Rule in freecad always constrain your sketches (sorry if this moved one side the goal was to constrain the sketch)
angle at 0 or 90° personal habit
GRBL does not accept tool changes so there is no need to take steps with different tools
in the job look but when I retrieved your file all the coordinate system was checked from 54 to 59.9
- KeepToolDown changed to true (we really save time)
for the change of dimensions if freecad tells you the correct ones then you are right no need to modify them manually
for your 0 piece in job -->setup select the upper side and click on "Set Origin"

[sliptonic]

GRBL does not accept tool changes so there is no need to take steps with different tools
in the job

FYI, you can set up a job with multiple operations with different tools.
In the output tab, set 'order by' to 'operation' and enable the split output.
This will split the gcode into multiple files so you can do the manual tool changes.

[legros]

Hello,
Thank you for the information, I didn't know about this option, when I need to separate the operations I use the Path_Op active toggle, very practical for that.

[GeneFC]

I'd love to have 0 in the middle of the piece too, but I don't know how to force FreeCAD to do it. In other programs it's just a setting change in one place, little button to press. That's it.

FreeCAD has a very complete and flexible facility to control the orientation and position any way you like.

Open the Job and select the "Setup" tab. Lots of options there.

It may not work like "the other software", but it works well. I do not believe there is any industry standard for such things.

You just need to learn the details.

Gene

[CADetInTraining]

Can someone record or write a larger/broader tutorial please?

I've tested few things Today - and my god this is not safe software to use sometimes!

First of all, it seems like I have to tell the UGS (or other software sending things to CNC) - what thickness the stock is. Didn't know that. I've only been using Easel so far - but that software is limiting - even tho it's convenient.

So far paths generated by FreeCAD:
- went too deep on few occasions, into spoil board - literally just plunging in in one spot.
- Half way through the job - decided to reset the zero point and just starts drilling in the air, or going deep into random part of the part (see image). This is Gcode generated from Legros's project, that he fixed for me.


I'm sure this software is powerful, I've been using FreeCAD a lot to generate parts for 3D printing for the past couple of years. But Path generation is just not intuitive or easy to use, compared to the rest of the app, especially Part Design.