New DRO vs Scale for exsiting one

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New DRO vs Scale for exsiting one

This topic has 7 replies, 6 voices, and was last updated 10 December 2021 at 13:13 by Clive Foster.

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30 November 2021 at 19:24 #20516
Dave S
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@daves59043
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30 November 2021 at 19:24 #573726
Dave S
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@daves59043
My lathe (CVA) has an Anilam DRO fitted.

The cross silde scale is fine, but the bed scale has packed up.

It seems cheaper to buy a complete DRO than a single Anilam scale!

Is it likely that an amazon (for want of a better reference) scale will just work with my exisitng DRO unit? I think I should probably think about replacing the cross slide scale at the same time as they are the same age, so sods law says it will die soon.

The scales are 5 micron resolution I think.

Dave
30 November 2021 at 19:36 #573731
old mart
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@oldmart
I think that you might as well just renew the lot, and possibly sell the existing parts on ebay to somebody who needs bits. It is unlikely that another make would work with yours, the exact dimensions and type would be needed. There is a firm which specialises in DRO's and possibly Mitutoyo, but the name escapes me.
30 November 2021 at 19:57 #573737
Chris Evans 6
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@chrisevans6
I found that a lot of scales will not work with older readouts. I have had a Newall on my lathe break and a Heidenhien on the Bridgeport mill break. In both cases I found second hand parts, if I had not found them it would have been a cheaper option to replace completely.
30 November 2021 at 20:23 #573742
Clive Foster
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@clivefoster55965
Ordinary TTL quadrature output scales, both optical and magnetic, are pretty standard internally whatever the makers label. Big difference is usually the connector and pin assignments. Machine-DRO have adapter leads to allow their scales to be used with various makes of DRO box. Some can also be used to interchange between some makes.

**LINK**

https://www.machine-dro.co.uk/dro-interfaces-cables-and-spares/cable/adaptor-cables

Not sure about replacing scales with internal reference marks. I suspect that the DRO box can cope with non referenced scales by ingnoring that output.

Newall and many Heidenhain scales are different in having sinusoidal outputs so the DRO head must match the scale. Newall use a completely different reading system for their "column of balls" scales so no interchanges are possible.

Clive
30 November 2021 at 20:28 #573744
Ex contributor
Participant
@mgnbuk
It seems cheaper to buy a complete DRO than a single Anilam scale!

When an Anilam scale failed on the Harrison at work it was cheaper to fit a complete M-Dro system than replace the faulty Anilam scale.

IIRC the Anliam scales output complemented signals (A, /A, B. /B, A, /Z) & the inexpensive Chinese scales just have the high going signals (A,B,Z) – I have not tried connecting a Chinese scale to an Anilam counter, though.

A Heidenhain or similar TTL output scale with the correct grating pitch should work, but a Newall designed for a Newall counter won't, as they are an analogue interface. Newall did do a version of their scales with a TTL interface built into the read head, but they were very pricey many years ago. I had a quote from Newall for a replacement system for the Harrison before going M-Dro & it was 3 x the M-Dro quote.

Nigel B.
10 December 2021 at 11:15 #574887
Barry Smith 4
Participant
@barrysmith4
Hi, I had some old anilam scales and I am pretty sure they were differential square wave. If so you can just connect one of each pair to a cheaper Chinese style dro box.

However, you can't connect single ended Chinese type scale to a dro box which has a differential input without adding electronics.

Do you know why the scale failed? Sometimes it's the blub/led in the read head which can be replaced, or the alignment of the read head which can be adjusted. To do either you really need a scope and some degree of electronics knowhow. If your really tight on budget I would be willing to have a look but you would need to get the read head and scale to me (NG4 3DB)

There are a lot of cheap scales and dros around on ebay at the moment. A guy also based in Nottingham cbr electronics sells good cheap kit and will also fit it. My only word of caution is that 5 micron scales on the cross slide might not give you the resolution you want in comparison to the Newall you have been used to. I have a Chinese 5 micron system fitted to my mill and lathe and on the mill they are fine but not 100% convinced on the lathe cross slide.

Cheers Barry
10 December 2021 at 13:13 #574896
Clive Foster
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@clivefoster55965
For all practical purposes 5 microns is 2 tenths of a thou.

Given the inherent ± least significant digit of any digital system the reality is that 5 micron scales let you confidently work to "better than a thou". Which may not be good enough.

Carefully splitting graduations on a dial can get things repeatably rather better but the absolute accuracy will almost certainly be worse.

But generally we don't care if 2 tenths clearance in a 1 1/2 inch hole guesstimate reads 1.5012" on our dial rather than the 1.4998" that an accurately calibrated DRO with 1 micron scales would. All we care about is the actual clearance and that machine / operator combination is repeatable enough to get that size and that reading close enough the next few times. Which may need a machine and / or operator tune up.

Accurate digital scales are easier than dials but showing too many digits can drive you nuts. Fortunately most DRO boxes let you adjust the number of digits shown after the decimal place.

Clive
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