All pockets have max depth=0 - help please!

[falviani]

Hi,

My setup is as follows (built from Git):
OS: Windows 10 Version 2009
Word size of FreeCAD: 64-bit
Version: 0.20.25025 (Git)
Build type: Release
Branch: master
Hash: fb8b21ec43dca706a4aa2d63d59a4fb79f050369
Python version: 3.8.6+
Qt version: 5.15.2
Coin version: 4.0.1
OCC version: 7.5.0
Locale: English/United States (en_US)

I have a design for a clamp to be used on a CNC Router, to be cut out of 3/4" wood. I created the side profile on the XZ plane, then extruded it on the Y plane. Checking all of the sketches involved with the sketch validator shows no errors, although the object-tree icons for the 2 sketches shows an 'X' which I take to mean there's a problem, although nothing is reported in the report view. (Does that just mean the sketch isn't completely constrained?)

The design looks like this:

ClampShot.png (21.78 KiB) Viewed 1596 times

The project file is attached, as is the generated gCode.
I ran the path validator operation, and it returned the attached text file (extension has been changed). It shows that the maximum depth for all operations is 0, except for the profile operation/dressuptag.
Examining the definitions for each operation in the GUI shows values that are exactly what I expected.

Running the post processor returned the following error:

Code: Select all

12:18:05  Running the Python command 'Path_Post' failed:
Traceback (most recent call last):
  File "E:\Dev\FreeCAD19_Output\Mod\Path\PathScripts\PathPost.py", line 262, in Activated
    PathLog.debug("about to postprocess job: {}".format(job.Name))

'NoneType' object has no attribute 'Name'post: grbl(E:/3D CNC Projects/FreeCAD Projects/CNC Clamp/ClampParametric_v5_gCode/ClampParametric_v5.nc, --translate_drill --postamble "G0 Z10;G0 X0 Y0;M5 G17 G90;M2;")
12:18:19  Post Processor: grbl_post postprocessing...
12:19:10  Done postprocessing.

I've spent several hours trying to track down what's going on. Can anybody show me what I did wrong?

Thanks in advance,
Frank Alviani

[chrisb]

I can postprocess here with a slightly outdated version.

The X in the tree view means indeed that the sketch is not fully constrained, see Tree View for the different overl symbols.

OS: macOS 10.16
Word size of FreeCAD: 64-bit
Version: 0.20.24825 (Git)
Build type: Release
Branch: master
Hash: ccc4151b3020969450325466e385850783795325
Python version: 3.9.2
Qt version: 5.12.9
Coin version: 4.0.0
OCC version: 7.5.1
Locale: C/Default (C)

[GeneFC]

There are two easily-fixed problems.

* The selected tool has a diameter of 1/8 inch and the steps are drawn at 1/8 inch. In many cases that will not work because the tool does not fit in the area to be processed. Change the tool size to 0.124 inch and the steps will work.

* For a lot of one-sided pockets, including those in your file, it is necessary to select "Use Outline" at the bottom of the task panel.

Your sketches are worse than simply "not fully constrained". There are several missing important dimensions, and the tangency constraints are completely bonkers. I had no problem in dragging the sketch to an unworkable mess.

Gene

[falviani]

Gene,

Thanks for the advice. After a bit of fiddling to replace the end mill with one slightly smaller, and using the 'outline' checkbox, I was able to generate the toolpaths I was expecting.

I'd like to avoid mistakes I made in doing this one. Could you point out what you consider missing dimensions (I found that it was terribly easy to get the sketcher to complain about redundant constraints, so I became cautious about adding dimensions). I believe almost all of the tangency constraints were inserted by the sketcher, probably as a result of my mechanics in building the sketch.

Again, thanks,
Frank Alviani

[GeneFC]

I believe almost all of the tangency constraints were inserted by the sketcher, probably as a result of my mechanics in building the sketch.

I normally leave "Auto Constraints" unchecked. Sometimes they work and sometimes they don't. In this case the automatic connections appear to be only coincidences, not tangents.

Tangent problem.jpg (62.27 KiB) Viewed 1518 times

I merely grabbed one of the lines and dragged it to create that image. I did not change any constraints or any elements.

The connections between the arcs and the lines should be end-to-end tangents. Then the sketch will be stable.

I am always very cautious about underconstrained sketches. Sometimes it is as simple as a construction line with an undefined length, but often it means the sketch remains in an unstable state.

Gene

[falviani]

Thanks for the info - I"ll remember that in my next design!!

Frank