Standardized test shapes

Here's the place for discussion related to CAM/CNC and the development of the Path module.
freman
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Re: Standardized test shapes

Postby freman » Tue May 28, 2019 10:21 am

If anyone has not heard of NIST, it would take less time to google it than to type that question.

National Institute of Standards and Technology
https://www.nist.gov

BTW NIST is where GCODE standards comes from. ;)

I have a machine to build and finish before I have too much free time for processing any of that to FreeCAD files. I would also wait for the discussion to develop to see whether there is already a resource for such shapes. What I provided was some initial work into that quest which OP seems to lack. I thought that would be helpful so see where this goes. I did spend quite some time searching but don't intend to go rushing off until we've seen what already exists and what can usefully be converted to FreeCAD format.

Since I am long way from being proficient and mastering FreeCAD, I may not be the most qualified person to convert any of that to FreeCAD files ( as you probably realise from your kind help in other threads. ) When I come to do that level of testing on my hardware, I will contribute any files I make of test patterns. Hopefully there will be some useful discussion and contributions in the meantime.

Some folk will probably have their own files to contribute already. Hopefully we can find other standardised resources, like the two patterns above, which could be converted to FreeCAD files. Probably best to see what is out there and prioritise work, rather than spending days on stuff which already exists or turns out not be of much interest.

It will be interesting to see what sliptonic and others turn up.

PS here is another interesting document with a couple of test shapes.

Institute for Machine Tools and Manufacturing (IWF), Swiss Federal Institute of
Technology (ETH), Zurich, Switzerland

https://www.iwf.mavt.ethz.ch/specials/m ... mepage.pdf

again shapes appear to be ISO standards:
ISO/CD 10791-7: 2010-10-06
chrisb
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Re: Standardized test shapes

Postby chrisb » Tue May 28, 2019 9:19 pm

freman wrote:
Tue May 28, 2019 10:21 am
If anyone has not heard of NIST, it would take less time to google it than to type that question.
Please note that the forum members are spread all over the world and that google may sort its results differently in different countries, but posting here should not be a google challenge anyway.
freman
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Re: Standardized test shapes

Postby freman » Thu May 30, 2019 9:48 pm

Well, I warned you I may not be the best qualified person but here is first attempt at diamond-circle-square type test piece.

I wanted to put a stepped hole in the middle too, but I can't get it do a negative extrusion ( pocket ). I can extrude 30mm in front but if I edit that to negative it gives some weird "predator" kind of rendition and no hole.

I'm pretty sure I had no problem with this sort of thing on 0.18. :?
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sliptonic
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Re: Standardized test shapes

Postby sliptonic » Thu May 30, 2019 10:11 pm

freman wrote:
Thu May 30, 2019 9:48 pm
Well, I warned you I may not be the best qualified person but here is first attempt at diamond-circle-square type test piece.

I wanted to put a stepped hole in the middle too, but I can't get it do a negative extrusion ( pocket ). I can extrude 30mm in front but if I edit that to negative it gives some weird "predator" kind of rendition and no hole.

I'm pretty sure I had no problem with this sort of thing on 0.18. :?
Awesome! I looked at the link you sent before but didn't quite understand it from the 2D. Your 3D model made it much clearer. Here's my attempt with the stepped pocket. Is this right?

What kinds of operations and uses would this be used to test?

Love it. Thanks!
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GeneFC
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Re: Standardized test shapes

Postby GeneFC » Thu May 30, 2019 10:18 pm

freman wrote:
Thu May 30, 2019 9:48 pm
here is first attempt at diamond-circle-square type test piece.
It appears you are using the Part workbench operations with a Part Design mentality. Moving fully to Part Design, as Sliptonic did, will help preserve sanity.

Also, the various references you gave appear to be directed at checking precision, accuracy, repeatability, etc. for machine tools. The theme of this topic is generating structures to test CAM g-code generation. Some overlap, of course, but not the same thing.

Gene
freman
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Re: Standardized test shapes

Postby freman » Thu May 30, 2019 11:04 pm

GeneFC wrote:
Thu May 30, 2019 10:18 pm
The theme of this topic is generating structures to test CAM g-code generation.
That is not the impression I got from the introductory video.

Awesome! I looked at the link you sent before but didn't quite understand it from the 2D. Your 3D model made it much clearer. Here's my attempt with the stepped pocket. Is this right?

What kinds of operations and uses would this be used to test?

Love it. Thanks!
Yes, I seem to have got confused into using extrusion when I need to use pocket and pad. That is what I was doing on 0.18, must be getting saturated with the number of things I need to learn here. Thanks for the fix.

I started out trying to reproduce the ISO standard but oddly it seems that they do not provide enough dimensions on their drawing to define all the features. Maybe you need to pay for the complete drawing.

The aim of such a part is to test machine accuracy:

is the circle round or elliptic : x,y perpendicularity.
are the squares square: perpendicularity, linear accuracy and backlash.
are the steps at the four corners the same thickness: z accuracy and table levelling.
Do the three figures all align at the midpoints or are there steps: general machine accuracy and repeatability.
Checking the entry point of the internal holes gives a check of Z axis perpendicularity and alignment of spindle axis to Z movement.

The base should probably be deeper to allow better z,y and z,x perpendicularity check, though you need to stay within the depth of available end-mills.

I may add in 3 degree rotated square too as in the ISO object. that give a check on how well the machine steps on acute angles. This is a factor of the interpolation algorithm as well as mechanics.

I did the first test cut on my new machine today so I'll be needing such a file shortly.
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sliptonic
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Re: Standardized test shapes

Postby sliptonic » Fri May 31, 2019 9:25 pm

freman wrote:
Thu May 30, 2019 11:04 pm
GeneFC wrote:
Thu May 30, 2019 10:18 pm
The theme of this topic is generating structures to test CAM g-code generation.
That is not the impression I got from the introductory video.
I had CAM in mind when I kicked this thing off but there's no reason to limit the shapes to that specific application. Including shapes that can be used to test machine accuracy seems like fair game. :-)
freman
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Re: Standardized test shapes

Postby freman » Sun Jun 02, 2019 2:18 pm

well this may turn out to be a good test for CAD software too. In the simulation I see a few oddities. More on that when it cuts and I see if there is really any artefacts.

For the moment I have some zombie paths which I can not get rid of. I've move them to one side but if I delete them I get an error and though they disappear from the rendition, next time I open they spring back to life. Apart from being messy, it seems this may be blocking code generation.

I ran view Gcode and it scanned OK and when I run post processor all seems fine but I don't get the file on disk :?

I also have some edge clean up problems on the paths I have named base-segment* . How do I get a path which actually cleans up the corners?

I'm running 0.18 asm3 here since 0.19 is causing serious problems crashing and scewing up the system. (Thread elsewhere on that.)

Code: Select all

OS: Linux
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.18.16268 (Git) AppImage
Build type: None
Branch: (HEAD detached at FETCH_HEAD)
Hash: 9a4632f4384c8f7496baf75aa38a46be74649d83
Python version: 2.7.6
Qt version: 4.8.6
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: English/UnitedKingdom (en_GB)
So in summary, the questions:

1. How to get rid of the zombies.
2. How to clean up edges.
3. Why no output file?
4. How to get the through-hole cut?

Thanks for any help. It looks like I'm near to cutting a test block.
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diamond-circ-sqr-paths.FCStd
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freman
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Re: Standardized test shapes

Postby freman » Sun Jun 02, 2019 3:27 pm

PS.

I managed to get rid of the zombies by using 0.19.

Having stripped this down to just one path, I still don't get any output. ;?

Code: Select all

grbl_post gcode postprocessor loaded.
Show editor = 1
postprocessing...
No machine found in this project
done postprocessing.
"No machine" is in black , so I'm guessing it's info rather than an error.

Can anyone see what I'm over looking?

thx
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zombie--.FCStd
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herbk
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Re: Standardized test shapes

Postby herbk » Sun Jun 02, 2019 3:58 pm

Hi freman,
i don't know how you get the Operations tree like it is at yor file...

freman wrote:
Sun Jun 02, 2019 2:18 pm
So in summary, the questions:

1. How to get rid of the zombies.
I don't get zombies, not on 0.18 and not on 0.19
2. How to clean up edges.
use the dogbone dressup
3. Why no output file?
Use only the "Export" Icon to export to g-code, the way File -> export don't work
4. How to get the through-hole cut?
Select the wall of the hole and use the Pocket OP
testpart.jpg
testpart.jpg (87.49 KiB) Viewed 504 times
Attachments
diamond-circ-sqr-paths_herbk.ngc.txt
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diamond-circ-sqr-paths_herbk.FCStd
(76.52 KiB) Downloaded 11 times
Gruß Herbert