Linear scale caput

[petro1headParticipant @petro1head]

My mill is fitted with their dro kit.

one of the scales has stopped working. Dismantle, cleaned, checked for dry joints but nothing

i thought I had found a great value one on eBay but the guy sent the pin out and it’s different.  Their scale only has four wires whereas the Warco (Sino) has 5

looking around googles the price seems to be £105, anywhere I should try, I need a 250mm one

[bernard towersParticipant @bernardtowers37738]

Have you tried Allendale/Machine DRO?

[petro1headParticipant @petro1head]

Yeh, same price as Warco

[owenhartleyParticipant @owenhartley]

Before spending £105, it’s worth confirming it really is the scale. Swap the dead scale’s plug with a working one at the DRO head. If the fault follows the scale, the scale is dead. If it stays on the same axis input, it’s the head or that input.

 

On the 4 vs 5 wire question: the basic signals are just +5 V, 0 V, A and B. The fifth wire on the Sino scales is normally the reference or index mark, and the shield sometimes counts as a wire too. Plenty of DRO heads never use the reference mark unless you use the “find ref” function. So a 4-wire scale isn’t necessarily useless, as long as it’s 5 V TTL with the same resolution as yours (most likely 5 µm). You’d need to rewire it to match the Sino plug pinout, and you’d lose the reference-mark function on that axis.

 

If you want plug-and-play, used Sino scales from scrapped mills come up fairly often. Check the length, the resolution and the connector type before buying. A slightly longer scale is fine too, as long as the body fits where the old one mounted.

[cedricvaleParticipant @cedricvale]

I’d check the scale itself before spending £105 on a replacement. Swapping the suspect scale onto a known-working input seems like a quick way to confirm whether the fault follows the scale.

The 4-wire vs 5-wire difference would make me cautious too. I’d want to match the voltage, resolution and connector/pinout before trying to adapt one, rather than assuming the extra wire is unused.

[not done it yetParticipant @notdoneityet]

Agreed.  Proper diagnosis is nearly always better (and often cheaper) than willy-nilly substitution of parts, if they have to be purchased!

[Martin Johnson 1Participant @martinjohnson1]

Try Colin Robinson at [email protected] .  His company is CBR electronics and he supplies, installs and repairs digital scales.  I have had his gear for many years and it works well.  He helped me out with a Sino scale which had failed.  By telephone conversation he diagnosed that I needed just a new read head which was a lot cheaper than a complete scale.

Martin

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