Sanding elipses using a fixed tool

[Woodboss]

I want to use the robot to sand the periphery of a bunch of elipses which the robot will hold centrally with a gripper, and using a belt sander.

The sander has belt pulley axes that are vertical, so that the belt is vertical and travels horizontally. Photo attached.
 
The elipses were cut by the robot so I know the dimensions but the path the centre needs to follow to keep the point of contact tangental is not the original elipse (another photo). Also they need to be rotated through 360 degrees as they follow the path so that the point of contact with the belt is always tangental?

Rather more complex a problem than I thought when I started this. I've a feeling that there may be feed speed issues on the long and short radius curves to deal with as well.

Any help here would be much appreciated!

Perhaps I should just make a vertical drum sander - but then I only just made the belt one - and it works really well...

[Johannes @ Robots in Architecture]

Hello,

Here's a quick example that should help you get started polishing the wood ellipses.
You see that A6 is running into its limitation, so you may need to set A6 on your robot to infinite rotation, which of course complicated the air supply for the gripper.
Maybe make sure that the robot starts close to the negative limit and then only turns in the positive direction.

Best,
Johannes

[Woodboss]

Hi Johannes,

Many thanks for your help. As usual I was trying to do this in an over complicated way with rotations and moves etc. I'd forgotten about the 'orient' component.

I'm still on Rhino 5 however and it refuses to open your files. I can replicate the Grasshopper part and see how it should work but not the Rhino file, it doesn't seem to be backward compatible. Could you perhaps export using a different format?

On another subject: Did you get to China to try some KPRC plasma cutting? It's still on my list of things to try when I get organised to hire a plasma machine (and clear up my shed!). 

[Johannes @ Robots in Architecture]

Hello,

Here's the file in Rhino 5 format. The GH file will complain about a version mismatch but should work as intended!
I actually didn't make it to China, here's a video what the colleagues from IP did: https://vimeo.com/287454509

Best,
Johannes

[Woodboss]

Hi Johannes,

That's exactly what I was trying to do. I just had three times as many components and it didn't work!

I've been working with mild and stainless steel recently but have been having the parts cut by CNC laser. Sometimes they come out a bit rough and linishing is really time consuming. If I get set up to use the robot and a plasma cutter they will probably be rougher again...

Best regards,

Charles.