Glass optical scale not working

Hello,

The Y axis glass optical scale, on my lathe, has suddenly stopped working.

While turning the cross slide wheel, the readout doesn't move.

I have dismantled it and given it a good careful clean, but to no avail.

Does anyone have any ideas ?

All the best,

Daniel

Hi Daniel first check the read head is set with correct clearances then swap the cables, making sure that they are marked up, from another axis and see if the problem moves to the other axis or the scale is stiĺl not working. Is it still under warranty what make is it.

David

Thank's David,

I have swapped the cables over and, indeed, it is the Y axis scale at fault.

It was fitted, by Warco, when purchased, which was around five years ago; so no warranty left. It has worked fine until yesterday when it just gave up.

That's it, in situ.

Next one is of it off & on the bench.

Edited By Daniel on 20/08/2018 09:02:56

Edited By Daniel on 20/08/2018 09:03:29

Daniel,

This previous discussion may be of some help: **LINK**

https://www.model-engineer.co.uk/forums/postings.asp?th=115030

MichaelG.

.

[note: I am still working with mechanical scales, so have no practical experience to share]

Hi Michael,

Thank's for that link.

I didn't realise they should be cleaned so often.

I did, however, strip it down and gave it, what I considered to be, a good clean. But, upon reassembly it still doesn't work.

ATB,

Daniel

Did you closely inspect the grating pattern on the glass to see if it had been damaged due to the read head rubbing against it or by swarf trapped between the glass and the read head ? Looking at your pictures it looks like the scale on the cross slide. (I call this the X axis on my DRO). If it is the cross slide then the cable to the scale will be flexed a lot so it is possible that a wire has broken in the cable. If you have an oscilloscope then look at the A & B signals where the cable plugs into the DRO. You will have to remove the cover on the connector. When the slide is moved you should see square waves (Or possibly sine waves depending on the design.) that are 90 degrees out of phase with each other. If the signals are square waves they should have a duty cycle of close to 50%. The amplitude of the A and the B channels should be about the same. (Probably about 5 volts peak to peak.

Les.

Theres usually a large gap from top of read head to the 45 degree angle glass.
End caps off and slide out the glass and clean, dont force it.
Never had any problem on lathe in 8 years on X, Z01 and Z02 for tail stock, there again its done right. Vertical scale on mill proves unreliable about every 8 months, i get a grey residue spread over the glass. Vibration will set it off as well into a continual count up but never have cleaned X and Y in 12 years.

X axis is length of the bed, cross slide is Z or Z10 on a lathe, Y on a mill.

If it is Z axis theres serious potential problems with the quick and easy wham bam install at the expense of usability - lost at least 2" there. Also quite possible heavier debris has been forced through the seal and or tail stock knocking read head.
While i think of it have you got full travel? Looks very close at extremes of the seal, will feel slightly spongy then solid.

Hi Daniel have you cleaned the head by disembling the end caps and sliding out of the end the reader head. I use a solvent cleaner to flush through and use a can of air to blow it though and also on the reader head. Return the head to scale if you are sure it is clean looking through scale. You have to set the reader head up with the correct clearances using packing pieces and check that the head is in the correct sideways location. If it fails to work M-DRO have a helpful person and they also sell reader heads separate if it is not fixable.

David

I would also check the wires in the connector and between the connector and read head

Daniel let us know how you get on not only are we interested but it helps others with similar problems. Also if you need any further help please ask.

David

Edited By David George 1 on 22/08/2018 16:06:54

I had to get a replacement reader head to fix one of these that died.

Martin C

Hello Everyone,

I will certainly post an update, if only, as David says, for someone's future reference. To be honest, I haven't had the time to look at it over the last couple of days. Life suddenly got in the way . The scale is "resting" on the bench, not having moved since having it's photo taken.

Thank's for your interest so far ....

ATB,

Daniel