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View Full Version : Hi all, dro needed



mite5255
10-08-2011, 06:04 PM
Hi everyone, I have just joined your forum and my hobby is metal-casting, mainly with aluminium. At the moment I'm making a few motorbike parts that need surface milling, so I have brought a 2nd hand rf30 mill and would like to put on a dro, now with me not know much about machining, but I'm learning I'll need some advice on what needs to be done and what's available
Thanks
Mike

loose nut
10-08-2011, 07:14 PM
The cheapest way to do it would be to use digital scales, inexpensive, relatively easy to mount, don't get them wet. The cost of "real" DRO's would probably be worth more then the mill, the SINO or no-name Chinese are the next step up, people seem to like them.

isaac338
10-08-2011, 07:22 PM
You could probably put three iGaging scales on there for an instant DRO for under $150 (maybe under $100 depending).

Join the Yahoo Shumatech group, there's a place called Quint Measuring which has really good prices on those scales for group members (the price list is in the Files section).

SGW
10-08-2011, 08:25 PM
You may do better to save your money for the day when you can buy a better milling machine to put a DRO on. Learning how to read the dials, deal with backlash, etc. isn't particularly difficult and it will give you a better appreciation of how to attain accurate results.

If you're hell-bent on a DRO for your RF30 though, the "printed circuit" DROs that operate like the readout of a digital caliper will give it to you for not much money...relatively speaking. Their major problem as I see it is lack of accuracy. I'm not sure what their stated error limit is, but if you need work to a thousandth or less, they won't be up to it. What kind of accuracy do you need? If you can live with, say, a +/- 0.002" error in hole placement, those digital caliper-style DROs will be fine.

mite5255
10-08-2011, 09:38 PM
Thanks for the prompt reply's, the accuracy that I need is not all that great + - 0.002 would be fine I would think, I had a look on eBay and have purchased
this http://www.ebay.com.au/itm/6-Digital-Readout-DRO-w-remote-LCD-fits-router-lift-/140590141198?pt=LH_DefaultDomain_0&hash=item20bbd34f0e hope it the right way to go

Mike

hareng
10-09-2011, 01:05 PM
Nothing wrong with the RF30 if its in good nick, far better than most weak dovetail column miller/drillers.
Some of best work has been with an smaller RF25 used up to 7 year ago with the cheap option of scales.

uncle pete
10-09-2011, 01:22 PM
One thing people keep forgetting is the old school method jig borers and jig grinders used before DROs were invented. If you've already got them a accurate set of micrometer setting rods with a good 1" travel dial indicater will also work. Yeah it's slower but it does work and a lot closer than + - .002 with decent equipment.

Pete

Bob Fisher
10-09-2011, 10:00 PM
I installed a Mitutoyu DRO on my RF30 some time ago. Got a good price(free) on it from a surplus machine. I had to shorten the X scale and mounting the Y scale challenged my skills, but it works great. Mounted a Z scale , also Mitutoyu and also free,and the machine is capable of accurate work if you do not push too hard. Again, it's a matter of what you can afford and what you can manage to haul into your basement in my case. bob.

tyrone shewlaces
10-09-2011, 10:12 PM
That one you bought is cheaper than even a Shumatech, so if that works you've probably done fine. Is 6" enough for the table travel even on an RF?

I like the Shumatech idea for a nice inexpensive DRO, but it's as if they have a nice design, good documentation and web site, good community support and good deal overall, but everything you'd actually want is ALWAYS out of stock. You can check every month for a couple years and I think you'll find that they never have anything available to buy except for plastic overlays and odds & ends, but never the meat & potatoes. Maybe they need a wealthy feller with some capital to get it off the ground.

Anyway, besides Shumatech and the thing you bought, the only other possibility I can think of is shadowing eBay and trying to find a good deal that way, but that's kind of hard to do on eBay anymore. I long for the days of yore, except that I'm kind of done buying stuff now.

Hope that thing works out for you.

EVguru
10-10-2011, 05:29 AM
I recently bought DROs for the Bridgeport clone and Harrison L5.

I ordered from http://thedrostore.com/

The service was very helpful and the shipping fast. The units are Sinpo (not Sino) from Singapore and made by Chfoic. The paper manual supplied was much better than the ones you can find online.

There is a blog with a lot of purchaser installations shown.

mite5255
10-10-2011, 07:12 AM
That one you bought is cheaper than even a Shumatech, so if that works you've probably done fine. Is 6" enough for the table travel even on an RF?

.

Yep 6 inch is plenty the rf30 only has a 5 inch z travel

Mike

KEJR
10-10-2011, 07:40 AM
I like the Shumatech idea for a nice inexpensive DRO, but it's as if they have a nice design, good documentation and web site, good community support and good deal overall, but everything you'd actually want is ALWAYS out of stock.

I've found this to be true as well. I thought the old DRO (DRO350 ??) from them was overkill (I just want something that zeros out!!) and they now have an ARM processor equipped monstrosity that is probably soon to start playing video games or something but nobody can even buy one. What crap is that?

Anyhow, I have thought of making my own minimal PCB but it would only be worth it if I could sell a few to other folks. Then at the end of the day you still have a caliper DRO. I'm not sure if it would be worth it, but any feedback is welcome.

KEJR

lbhsbz
10-10-2011, 03:13 PM
I bought one of the M-Tech 3 axis units from theDROstore on ebay...it is very inconsistant, to the point of being absolutely worthless. Checked against a dial indicator, when both are zero'd, and the table is moved away from the zero then back until the indicator reads zero, I've got about a .013" variation on the DRO...when it should be zero. I'm awaiting some support from the seller, but for now, I'd say stick with known brands.

hareng
10-10-2011, 03:21 PM
Any movement in the setup?
Usually a common mistake on quill mounted dro.

tyrone shewlaces
10-10-2011, 05:50 PM
I've found this to be true as well. I thought the old DRO (DRO350 ??) from them was overkill (I just want something that zeros out!!) and they now have an ARM processor equipped monstrosity that is probably soon to start playing video games or something but nobody can even buy one. What crap is that?

Anyhow, I have thought of making my own minimal PCB but it would only be worth it if I could sell a few to other folks. Then at the end of the day you still have a caliper DRO. I'm not sure if it would be worth it, but any feedback is welcome.

KEJR

I felt that the original DRO was pretty nice for the money and I even put one together and it's on my mill. It works fine. The strange thing about it though is that since it was originally designed to interpret chinese scale protocol, they came up with a dongle to take simple quadrature signal and convert it so the DRO could use standard glass scales. That is nice since the glass scale thing is likely to be more accurate and reliable, but the interpreter dongle was a klunky idea I thought. It apparently worked OK. Of course the new one takes quadrature data natively.

There are a couple features on the new ARM thing that are handy things that I wished were on mine, but the rest of the features fill up an awfully long list so there's probably a lot of stuff on the new one I wouldn't be using. But it's better to have more and not use it than struggle with less I guess. As you say though, if you can never buy it anyway, then it's all academic. I'm sure if you post on the site that you want one they will respond and talk about a group buy and getting on a list and all that, but I'm sorry, that mucks up the works. I'm sure it would be much more popular if they existed and you could just order one.

Your idea of a scale reader sounds cool and I'm sure there would be folks interested in it. I think LED digits would be the good way to go so you can read the thing - seems like it's never bright enough in a shop for me. Of course if it could do either LCD or LED display the end users could decide for themselves. And if it would do three axes on the one display, that would about cover it wouldn't it. Yea just one to read motion and zero out would cover most anything a guy needs.

The chinese scale protocol thing is published on the web a few places, so if you wanted to dig into it it might not take too long to work that out, and it seems to me that would be the hard part. You can get nice PCBs made for probably $5 or less these days via the web and credit card. Seems like if you wanted to make something like Shumatech (kits and instructional website) but much simpler and cheaper, there would be a bit of a market for them. I don't think you could retire from it, but it might bring some beer money for a while. I'd almost bet money that the OP would have at least strongly considered one if it was out there.

KEJR
10-11-2011, 11:58 AM
Thanks for responding Tyrone. Using the 7 segment LEDs adds quite a bit of complexity, believe it or not. With 7-8 digits by 3 axes you have to multiplex 24 digits with decent current in order to see the things, or use alot of latch chips. This adds alot of soldering of more components, higher component counts, etc. Its one reason why the DRO350 has alot of components on it (although its a solid design).

I was toying with a large character backlit LCD screen. Its not as nice as a 7 seg or Vacuum flourescent but the interface to the CPU is much simpler. It'd probably cost the same or slightly more than the 7 seg LEDs, but it assembles with one connector, some standoffs, and you are done.

Is there a good economical source of glass scales? I looked at the chinese scales from Sino and by the time you bought two axes you were only a hundred dollars away from buying the 2 axis DRO "kit" with the readout head included. I don't know how good these are, but if thats the competition its hard to beat.

I don't think it would be that hard to make a unit that takes both quadrature and the chinese scale protocols. The trick might be doing x4 quadrature in software with an 8 bit micro on three axes and very high frequencies (due to high count encoders). I'd hate to limit it to x1 or x2 quad. The faster the max feedrate the worse this gets of course. I could pump it through a CPLD, but that adds alot of complexity as these aren't really hobbyist friendly in terms of power supplies and soldering. Thanks for the feedback it is good to know that there might still be a "market" for the tinkerers out there.

KEJR

tyrone shewlaces
10-11-2011, 05:45 PM
Yea it seems like if you're shooting for the budget DRO market (most logical) then just going with a backlit LDC display makes the most sense.

As for scales, I picked up some inexpensive longer ones new off eBay for pretty cheap (less than $30) back in the day, but eBay isn't what it once was anymore so I don't know if they can be found anymore. I had to shadow it for a week or so but a recurring auction finally came up that suited my needs. For 12" or less there are some pretty inexpensive chinese calipers out there. Dirt cheap.

For truly home-grown, US Digital sells mylar encoder strips and readers so you can roll your own quadrature scale with whatever configuration you want, but it looks like it would be at least $50 for just a reader and encoder strip. Some labor involved after that. Maybe there's something similar for less money out there. Here's a link to US Digital:
http://www.usdigital.com/products
One thing about these is the first $50 is the bite up to 7", then adding length increases the cost in small $ increments (about $2) per inch.

KEJR
10-12-2011, 08:34 AM
I checked out the US digital stuff before. Its only 500CPI, or 0.002" resolution. Me and another guy on here were looking into magnetic encoders, but the magnet stock needed to be bought in large quantities to get the price down and someone would still need to assemble the intricate reader heads to get the price down cheap. Then you would have to align the things well at assembly or you would have added error (I suspect there is *some* of this with glass scales too). I didn't want to invest in it because it was going to cost real money just to buy the magnet strips!

KEJR