Digitizing arm options

[Graham S]

I think if your encoder calibration is changing between uses then there is something a bit wrong. Plus the wrist rotation has no limit and probably the same for the base?

"and move the arm back again to know the repeatablility. This data captured allows you to know what angle corresponds to what data measurement"

With optical encoders we don't need to worry about angle to measurement relationships.

I do like the idea of the limit being used as a mechanical reference point.

It will depend on the specifics of the machine as to what sort of mechanical reference is best. Some arms may be easiest to align straight using a surface plate or straight edge. Some may allow easy adjustment of the encoder so no need for the software calibration. Lots of ways to do it.

Graham

[Graham S]

Nice work Gary

You can be testing your arm in days with the DRO software, even if you have to write the numbers on the screen down

Graham

[Graham S]

p.s. Is there an easy way to make such nice line drawings from Rhino models?

Graham

[jtedmonds]

Gary - Very Nice model.

[Graham S]

Well I have had a go:

http://www.indoor.flyer.co.uk/digiarm.htm

This shows some of the ideas and has some of the links needed. It is on my domain but I have made it clear it is not my project etc and have tried to reference links put forward by others etc.

It also has a few diagrams showing software options etc which may be helpful.

Graham

[duluthboat]

Graham,

Excellent that brings it all up to date, for those who don’t wish to read this whole thread. Hopefully it will pull a few more people in. I’m eager to try the DRO, if I get that working I’ll surely have learned something.

The drawing is done by a render plug in for Rhino, called Penguin. Sometime simple lines show more detail.

Gary

[jtedmonds]

That's great Graham. Reading all 13 pages might be tough for some new readers trying to catch up. Even though I've decided to focus on building my router table right now, I still want to keep up with this project and help out if needed. This is a project I plan on doing in the near future!

[Graham S]

Thanks Gary, I had just found Penguin after a google search, just looking into getting it in the UK, hopefully at the educational price, the demo produces nice results anyway.

Jason, I think you do right to concentrate on the router, after all most people want to digitize something so they can then cut it. Plus a router would be dead handy for making the parts when you do make the digitizer.

Graham

[duluthboat]

Another cool thing you can do with a CNC router if it’s large enough is to mount your arm to the bridge and use it as a controlled offset. Life just keeps getting better.

Gary

[bgriggs]

Here are some links to sights with info on 3D digitizing. Some of them are
not particularly useful, however there are a few which tell how to make
simple 3D laser scanners for small $$. Also it seem the majority of free
software for this type of thing uses a laser digitizer.

Bill

http://www.emdsceptre.com/upgrade.htm

http://www.engr.uky.edu/~lgh/3dDA/hb2003.htm

http://www.muellerr.ch/engineering/scanner/

http://www.muellerr.ch/engineering/default.htm

http://perso.club-internet.fr/dpo/nu...n3d/#hardware1

http://vfxworld.com/?sa=adv&code=319...id=2150&page=5

http://www.imsrv.com/deskcnc/probe.htm

http://remtek.com/remtek/ourBEAT.htm

[Cliff_J]

Wow, lots of activity. I think I need a summary. LOL

Nice job Graham. Later I'll see if I can edit my first post and reference it. I could mirror it on my site if you want and/or we could share the updates.

The specifics of the indexing and machine setup could become very complex. I guess I had visioned something simple so even a person (like me) without much precision gear could build it. But as with anything open in design, a simple mod here or there with compensation factors would be easy enough.

I'd say this is almost ready to be declared an open source project. Weekend after next or on some weeknight I'd like to play around with the parallel port and get used to capturing pulses with the DRO software and in windows. I figure a 555 would be the cheapest and easiest way to find the speed limit and simulate the encoder output.

This is pretty awesome. Once I'm comfortable with the parallel port an encoder & chip would be the next thing I'd like to test with an 4' MDF arm to check the pulse-counting reliability to index-mark. Maybe even a test with a stepper moving the encoder. Then going with emachineshop.com or a member to make some parts to assemble an actual arm. If someone wants to work faster than me, I'll happily work with your data.

Cliff

[duluthboat]

Having read and reread the info on DRO’s I’m sure the electronics for this thing will be beyond my capabilities. So is there an off the shelf solution for the electronics?

Gary