Machsupport Forum

Mach Discussion => General Mach Discussion => Topic started by: Spartan117 on March 06, 2011, 08:09:02 AM

Title: Auto-height-compensation possible?
Post by: Spartan117 on March 06, 2011, 08:09:02 AM
Hey there...

I am searching for this for years now but can't find anything like that.

Please take a look at this video
http://www.youtube.com/watch?v=PKO--ubR86o

Here you can see the auto-height-compensation, datron offers. The machine can scan the surface z-height in a defineable raster.
Then the machine is able to compensate the different z-heights with the z-values of the GCode and it achieves a nearly perfect gravure.

Is there ANY possibility to do this with Mach? Or with a combination of probing and CAM?

Thank you very much and best regards,

Marc
Title: Re: Auto-height-compensation possible?
Post by: Tweakie.CNC on March 06, 2011, 08:25:03 AM
Hi Marc,

I have never seen anything like this before although if a panel was that distorted I would not want to engrave or fit it onto my equipment anyway.  ;)

The facilities exist within Mach to probe the surface but you would need other CAD/CAM software to read the data in order to create the GCode with varying depth according to the position data.
I am sure it can be done, not automatically as shown in the video, but would it really be worth all the effort ?

Tweakie.

btw. Thanks for posting this video, every day I learn something new and this is just amazing.
Title: Re: Auto-height-compensation possible?
Post by: Spartan117 on March 06, 2011, 08:48:08 AM
Nice cat btw :D

The panel in the video is just an example for the ability and possibilities it offers.
Imagine you have a knife handle, a rounded lighter, a convex medal or something like that and you need to engrave it. Only one try and the need for a perfect finish
So i think such an option would be very nice to have?

For example, I had to engrave two exhausts yesterday and the welded outside was very bumpy and uneven. So, that option would have been VERY useful.

You don't accidentally know a good link for me to get closer into that probing-thing? I did a search for probing and, wew, that's a lot^^
Engraving on a 3d-surface is not a problem, but the probing itself and the translation into the 3d-surface is a new arena for me ;-)

Title: Re: Auto-height-compensation possible?
Post by: Tweakie.CNC on March 06, 2011, 09:05:45 AM
Sorry buddy, like you I have just read about the probing it is not something I have actually had the  need to do. There are a number of members here who do surface probing and I am sure one of them can help.

Tweakie.
Title: Re: Auto-height-compensation possible?
Post by: BR549 on March 06, 2011, 09:37:22 AM
The only way I know that it will work is to prescan the surface then import that surface into your cam then overlay your object over the surface then merge the two together to create a new object 3d file that accounts for the material surface irregularities.

Not an easy task.

Now that said somone here WAS working on a software sytem to do what you want. I'll see if I can find it.

(;-) TP
Title: Re: Auto-height-compensation possible?
Post by: ger21 on March 06, 2011, 09:55:28 AM
You could write an app to load both the g-code and scanned surface an output corrected g-code. To me, that would be the easiest way to do it.
Title: Re: Auto-height-compensation possible?
Post by: Spartan117 on March 06, 2011, 10:20:33 AM
Hehe, maybe for you that would be an easy way. But i don't have ANY programming-skills^^
You don't accidentally want to program such an app? :D I'd pay for it if you would.


But as i said, projecting the gcode on a 3d-surface shouldn't be a problem, too. Afaik, my CAM knows how to do that. ;)


@BR549
Thank you very much, i hope you can find it :)



I read some threads about probing now, but no useful hints yet. Maybe i will have to read the left 500, too :D
Title: Re: Auto-height-compensation possible?
Post by: BR549 on March 06, 2011, 10:42:21 AM
The person working on it planned to do a scan probe of the surface then take those points and interpolate his Gcode file to compensate for the irregularities via software and create a new gcode file to do the cutting.

(;-) TP
Title: Re: Auto-height-compensation possible?
Post by: alenz on March 06, 2011, 07:23:49 PM
Here is a fellow who did just that.

http://phk.freebsd.dk/CncPcb/

He even posts the code with a beer license.
Al
Title: Re: Auto-height-compensation possible?
Post by: RICH on March 07, 2011, 06:27:09 AM
There is laser scanning and then you need to mesh the point clouds from it and the software is like $500 to do that. Accuracy of the scan is around .005". Still need to be able to add the engraving you want onto the surface via CAM. All not a trivial task.

---------------------------------------
 ???
Just a brainstorm idea.......if you had the engraving pattern on the piece one could use CopyCat and touch off all along the engraved line and get the
the points into Gcode directly. Something to try on a rainy day.........lets call it poor mans scanning! ;)

RICH
Title: Re: Auto-height-compensation possible?
Post by: Spartan117 on March 07, 2011, 12:23:24 PM
Adding the engraving-paths on the solid is not the problem, resp. my CAM will do this ;)

Doing the scan and meshing the cloud is still my problem. Or even how the origin is defined and recalled when engraving and things like that

And Laser scanning is not what i'm looking for. I'd like to use a probe with a precision-sensor (under 2┬Ám accuracy). So i hope to get around 0,001" at the end.
Do you know points2cloud? It's free and i'd try with this first.

@al:
Thank you, but i'm not sure how this could help me? Maybe my english is too bad after all, but i don't see how i could use this for this purpose

@BR549
Still no idea who tried that too?
Title: Re: Auto-height-compensation possible?
Post by: Userli on July 05, 2011, 05:58:33 AM
Hi,

when Marc told me about this I thought that would be easy to do in Mach and so I told him, that I would look into it.

My first try was to simply change the reference system (G54 etc.) according to the height profile. This apparently is not looked at during a move.
My 2nd try was to directly modify the trajectory buffer's Z position. This somehow works but this way I redo some work, which the engine does anyhow:
The engine must keep somewhere what the destination coordinates are and fill the trajectory buffer accordingly.
Changing those coordinates' Z part as a function of XY position seems to me the easiest way to achieve the height compensation.
However, looking through the headers I couldn't figure out, where this would be stored.
Does anybody know if this is accessible from within a plugin?

Cheers, Frank.