dro

[georgewright]

I am just new to this BB but I and a friend have been assembling Art Axteins and Lindsays DRO using a computer as a readout.
It has gone together real well. The big problem we have is ENCODERS. Surplus encoders are not easy to find and new ones cost to much for me. Has anyone andy info on encodes and avaiability of used or suplus units. I am also intoersted in Asinaj and his mention of JTS Machinery (800)321-3566 and DRO . We would appreciate any help, Thanks. George

[Thrud]

George

Watch eBay - I have seen lots of them for very little.

[mikem]

Where can I read more about Axstein and Lindsays DRO using a computer? What type of encoder does it use? Thanks--Mike.

[Metal hack]

well George i was looking into bilding that dro,i have not had time to start but i would be very interisted in what you find out for encoders.

Jason

[brunneng]

I've been working on a dro as well. I just can't pay $700+ for something that can be built for $100 in surplus parts.
I purchased 3 pittman dc servo motors with encoders for $59 each from http://www.resunltd4u.com to be used in a cnc mill. I decided to use cheaper steppers for now and use the encoders for the dro. Search for 'encoder' and at the bottom of the list you should see the motors. The encoders are 1000ppr (4000ppr decoded quad) and cost at least $280 new for the 100ppr model from BEI new.
I also just picked up a pair of industrial BEI encoders on ebay for $99. These babies are 3600ppr! (that's 14,400ppr quad decoded). I have no idea what they cost new but the base models are $450 new. That comes out to .000003472" per pulse on a 20tpi leadscrew.
I'm working on the circuit for a small stand alone dro readout so a computer and monitor won't be needed. I'm also finishing the circuit for a tiny digital tach display for mills/lathes. I'll put up some information for hooking up the bei encoders on my website http://www.version5design.com for those interested.

[Rotate]

I don't want to discourage anyone from building their own DRO, but in order to get 0.0005" accuracy which is minimum that you want for a DRO, you have use a direct linear transducer. It's easy to get 0.0005" or better resolution using shaft encoder linked to a precision rack and pinion assembly (worst if you use the existing leadscrew), but if they are not repeatable then they are worthless resolution. The two competing technology for linear transdcucer are optical and capacitive and unfortunately they are both difficult and not cost effective to build yourself. I've been looking at building my own optical DRO using a slightly different technology, but by the time I've figured the cost of optics, sensors, and the display unit, it's cheaper to by a Mitutoyo DRO when they go on sale I'm still tinkering with the idea though.

Albert

[brunneng]

Albert-

You're quite right on the concerns about accuracy and repeatabilty in a home brew dro using rotatry encoders.

I'm talking with a company that produces linear strips at a reasonable cost but their stock resolutions are not high enough. I have suggested some ways around it to them and am presently waiting to hear back.
Depending on their answer I could sense a single axis for $50-$100 a sensor at .0005"

We'll see. If the prototype works well and accuratly, I might look at getting the backing to do a production run for the hobbyist sized machines. It might be possible to sell a 3-axis DRO for $300-$500.

Kevin

[jcc3inc]

Dear Sir:
You will find rotary encoders as well as linear strips at U S Digital Corporation,
www.usdigital.com. They are economical and have a good range of products. As others have mentioned, EBay may have some encoders as well.
Regards,
Jack C.

[wmgeorge]

What about those DRO from Shooting Star? I really don't see how they work... unless it is some sort of worm gear setup?

I have a HF Mill-Drill, the 2 HP Made in Taiwan model which is surprising good for the money. I've got it set up with now with a 1 1/2 HP 3 phase motor and VFD. DRO would be the next addition. Any suggestions? Thanks. B.G.

[dperkins]

<font face="Verdana, Arial" size="2">Originally posted by wmgeorge:
What about those DRO from Shooting Star? I really don't see how they work... unless it is some sort of worm gear setup?

I have a HF Mill-Drill, the 2 HP Made in Taiwan model which is surprising good for the money. I've got it set up with now with a 1 1/2 HP 3 phase motor and VFD. DRO would be the next addition. Any suggestions? Thanks. B.G.</font>

[dperkins]

I have been using a shooting star DRO for 6 years on my Enco Mill/Drill. It uses a rack and encoder. Accuracy is within .0005 and it is repeatable. It is a pain to install but it's worth the trouble considering the cost of other brands.