Forged parts belt-grinding

[Xylotica]

Hi !

A friend of mine wants help to set up a robotic grinding cell for forged hand tools.
The main problem that I see here, since the forged raw parts are somewhat rough, there is a need for some kind of geometric inspection to determine the time it will take to grind.
Any suggestions for optical measurement devices I could hook-up to my controller to make adjustments during the execution of the program ?

Cheers,

[Johannes @ Robots in Architecture]

Hello,

Hmmm... Not really my area - it does not sound like an easy to solve problem, as e.g. shiny metal surfaces can be complicated for some optical inspection systems.
Maybe it would be possible to go the other way by implementing a system that measures the reflectivity of the part (I guess the forged part is matte and then gets shinier with polishing) and the robot performs the grinding, checks the piece, and then repeats it if the finish is not there yet. I guess that could be easier than determining the time to polish beforehand.

Best,
Johannes

[Xylotica]

Hi Johannes,

It's not only the shinyness that matters, but also evaluate how far the part is from it's nominal dimensions.
Forged parts can be quite rough.
Thinking of it, it could be a contact caliper : the robot would bring the part in contact with it at a nominal point, and by the amount of movement, one would know exactly how far away the un-finished part is from that nominal point.

Maybe this can even be made very easily with a rheostat and an arduino...
Of course, an off-the shelf product would save me some time.

Cheers,

[Johannes @ Robots in Architecture]

Hello,

Do you have any photos of how the parts would look like?
I don't believe that any off-the-shelf solution would be particularly affordable, so you may have to hack something together, or combine the robot with other machines.

Best,
Johannes

[Xylotica]

The parts look like this :
https://goo.gl/photos/NurQg4ubAaVGNFGb8

Maybe something like this could do the job if I manage to connect it to an arduino :
http://www.directindustry.com/prod/elbo-eredi-bassi-araldo-sas/product-53966-1082195.html

Cheers,

[Johannes @ Robots in Architecture]

Hmmm... The robot already knows where it is in space at all times, so maybe you don't need the live feedback, but could just program the toolpaths based on a finished piece, which then grind it down to the desired shape?

Best,
Johannes

[Xylotica]

I see what you mean, but no, this doesn't really work.
That's because the grinding is done on a part of the sanding belt which is not supported which allows to sand the curved survace much more smoothly.
Therefor, it is not easy to grind "down to a certain desired shape" because the sanding belt is not a fixed reference.

My idea would be to make a first pass, then measure the deltas between strategic points on the current shape and theoretical points, and then do the finishing pass at a re-calibrated speed depending on how much material still needs to be grinded.

Cheers,

[Xylotica]

I found this guy : http://www.instructables.com/id/Interfacing-a-Digital-Micrometer-to-a-Microcontrol/
He made an interface for Mitutoyo measuring devices with an Arduino.
I suppose that it could be used as an input for the robot and affect process speed accordingly.