3 axis digital readout (DRO)

[baseball43v3r]

hey guys, browsing the internet and came across this handy gadget floating around the internet, its called a DRO (digital readout). It appears to be a DIY kinda of deal (always up my alley), and price seems to be around 300 I would think, guess it depends on your sourcing. Thinking about adding one to my current build, and I figured I'd pass it along to everyone here.

link here: http://www.shumatech.com/web/products/dro-550

picture here
http://www.shumatech.com/web/sites/default/files/images/DRO-550.medium.jpg

[bradm]

John, what were you planning to use as scales to drive it?

[baseball43v3r]

hadn't quite figured out that far, just thought the concept was interesting and I'm always one for opensource projects, so I figured I'd share.

[smreish]

Thinking out loud...
If I was to and an absolute reference device like this DRO display to a MM, I would most likely have dual shaft steppers on my machine and add encoders to the second shaft.
Of course, this is NOT really an absolute reference because it's on the drive train and not the actual physical part that's moving....but as close as your going to get without purchasing really long scales like Brad mentioned.

The other thing you could do is add a YO-YO absolute resolver to your moving parts. (yep, looks like a kids yo-yo, is spring loaded, and spools out a single string) This would give you a very affordable absolute, non-volatile reference device. But resolvers are typically analog, thus limiting your DRO choices. But, since it's analog, you could easily get a digital readout to scale and display the analog reference sent out by the potentiometer in the yo-yo. (Brad, think moving battens or pit elevator)

Good luck.

[Gerald D]

Your Mach screen already gives you DRO's . . . . why would you want a duplicate set?

[KenC]

Exactly.
I understand the need to cross check on human operator but a CNC???
Or you can hack the components & turn your MM into servomotor drive :)

[smreish]

I 100% agree with Gerald and Ken, Mach supplies a DRO and is very accurate.
If, for some reason you wanted an outside the CNC envelope verification, then the previous post applies.

I do know, that I have automated both a mill and lathe with only 1 or 2 axis out of the 3 available. Thus relied on a manual DRO to reference one (setup axis - like the z on mill) then automate the x and y. NOT the best choice, but the requirement of it has come up. Or, my 4th axis on my Mechmate had a manual rotation with DRO feedback (because I had it in the shop) until I hooked it up with a stepper and Mach3.

If it was to come up again, I would definitely spend the money to automate my z on the bridgeport. It's actually cheaper than adding a reference scale and DRO.

[Allegheny]

I was actually going to buy a ShumaTech DRO for one of my milling machines, only to find that Scott (the guy who runs the show) stopped producing new kits nearly a year ago. If you are determined to go this route, there is a YahooGroup dedicated to the things and unused/brand new kits are sometimes offered for sale.

On the ShumaTech website are multiple articles about using ChiCom scales (available virtually everywhere) and interfacing them with the DRO. I've never seen a single scale over 48", however. Don't know how, or even if it's possible, to gang some together to give the 8' plus a MechMate would need on the x-axis.

Brian