Lathe DRO recommendation

All discussion about lathes including but not limited to: South Bend, Hardinge, Logan, Monarch, Clausing and other HSM lathes, including imports

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Re: Lathe DRO recommendation

Post by WJH » Wed Feb 28, 2018 11:38 pm

I used a logic analyzer to figure out the pinout of one glass scale to work with another reader head. Generally they are all 5v ttl logic, quadrature output. Easy to figure out what is +5, gnd, A, B from the display head.

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Re: Lathe DRO recommendation

Post by f350ca » Thu Mar 01, 2018 9:22 am

The magnetic scales sold by DRO Pros seam to use a magnetic tape with an adhesive back that you bond to an aluminum extrusion. Aluminum has a high coefficient of thermal expansion, about 3 to 4 times glass depending on the material. On a 12 inch scale with a 10 deg f change, the length of the magnetic scale will change .0028 inches vs the glass at .0008. Not to mention are you stretching the magnetic tape as your sticking it to the aluminum extrusion.
Something to consider if you expecting the .0002 resolution they advertise.


John Hasler
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Re: Lathe DRO recommendation

Post by John Hasler » Thu Mar 01, 2018 9:31 am

You'll still get the resolution. What you may lose is accuracy and repeatability. I don't see why you couldn't bond to stainless steel (or glass) instead, though. Another possibility is to solidly secure the aluminum extrusion to steel.

Their electronics probably don't support this, but it is possible to map an installed scale to improve accuracy. You could even attach thermistors to the scale to monitor temperature and do dynamic compensation. Better to just bolt the aluminum to steel, though.

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Re: Lathe DRO recommendation

Post by NP317 » Thu Mar 01, 2018 10:51 am

The thermal expansion coefficients will depend on the alloy used. The family of Silicon-Aluminum alloys has some with very low expansion rates.
This make me curious as to which alloys are used to support the magnetic scales.

I mounted the DROPros mag scales to steel foundations on my mill. Accuracy has exceeded my requirements so far, and I see a maximum temperature swing of 25*F in my shop during winter. Not a problem so far.

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Re: Lathe DRO recommendation

Post by pete » Thu Mar 01, 2018 11:49 pm

DRO Pros sells Chinese built DRO's as well as sold some Newall models. They didn't sell my Newall model when I was buying mine, unless I missed it while checking there website it doesn't look like there still selling anything made by Newall right now. Those magnetic scales and reader heads for the Newall displays would have been the Newall Sperosyn or Microsyn scales. From what others have said in this thread the non Newall magnetic type from them doesn't sound all that impressive for how there made, but maybe they work well enough. My DP 900 has a mapping funtion, but other than using my set of gage blocks it would take a lot more specialised equipment than I have available to properly map the scales and do it accurately enough over long distances. A surface grinder might make it worthwhile, but I doubt my scales are out over any distance enough to matter on a milling machine.

Newall seems to get pretty high marks from the pros over on PM. I've not owned nor used anything other than Newall so can't confirm what some others have mentioned there. But fwiw Heidenhain followed by Acu-urite are "supposed" to be even better. Prices to match of course. Almost all on PM say the Newall scales are the easiest to mount though. Heidenhain made what I think was called an active system that was used on a lot of the Deckel mills some years ago and it was sort of an early and almost but not quite CNC system. It could drive the tables power feeds to preset starting and stopping points and chosen feed rates. I know a guy in the UK who has used it and he really liked it.

You asked about interchangeability between magnetic and glass scales Ron. Like Bill said, yes and no. Probably yes if the display and scales are by the same manufactuer but I can't say that's 100% for them all either. My computer / electronics knowledge is pretty much nil. It's my understanding that there's 3 or more different systems in common use with dros for the display unit to recieve the signals and process the data. Some dros can use adapter plugs to use a different companys scales and adapt there plug type to the display units plug type. Mitutoyo did or still does have adapters to run Newall scales with there displays but there's likely many that can that I don't know of. Checking with the manufacturer of the display about what scales can be made to work might be the only way to be sure it can be done if your electrical abilitys match mine. Mitutoyo now make glass and magnetic scales for example and afaik either can be used with any of there displays. Heidenhain apparently uses something a bit different than most others and I don't think many other manufacturers scales can be used with there system.

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Bill Shields
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Re: Lathe DRO recommendation

Post by Bill Shields » Thu May 10, 2018 5:33 pm

just a heads up about DRO PROS

The ELECTRONICA kits they sell are from India (I have a friend that works for them) ->

Don't know about EASSON
Too many things going on to bother listing them.

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