DRO Scale Compatibility

Hi,

We have a sink EDM with z axis scale reliability issues. It appears the rubber sealing material in the ends of the scale has degraded, and is flaking off into the path of the reading head. After we clean the flakes out it works ok, then eventually we start losing position again. We don't get error codes, just the displayed position drifting from the actual position.

The scale connects to the machine control (Creator CR-5) rather than a normal DRO display.

The offending scale is a mitutoyo 529-433 AT11-N200

We are told this scale has been superseded with 539-203-30 AT113. There is one available new for $560 + $100 shipping. (only one in the world right now we are told, if someone else buys it we are in for a long wait) I don't begrudge the supplier or Mitutoyo this pricing, we use mostly Mitutoyo DRO's and are usually happy to pay what it costs. Trouble is we are not 100% sure the scale is all that is wrong, and this machine is at the end of it's life and scheduled for replacement. The new machine is still months away so we want a stop gap repair. Are there lesser (cheaper) brands of scale that can be adapted to this model? If we have to pay the $660 then so be it but I have often wondered how compatible the different brands and models are for someone who does not mind swapping some wires around.

Thanks in advance

Andrew

I believe the lip seals in the AT11 scale are still replaceable. We have repaired many of these scales over the years. I will check with our service department tomorrow and get back to you.


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Using only basic common sense knowledge I can give you this. A device like your scale is going to have voltage requirements and certain output characteristics like data type, wave form, all that blah-blah-blah electronic stuff. I doubt the control will have any clue, at least not one that matters, that there is a Mitutoyo logo on the scale. If you want to save money, but likely not time, set someone down with the technical literature of the existing scale and those of possible replacements. If you can find one with most or all of the specs lining up then give it a shot. Many industry sectors have standardization in one form or another. Whether scales and readouts fall into that category is unknown to me. Part of me thinks maybe not, but digging into them even a little will likely tell you soon enough if you're on to a possible solution. Who knows, the worst thing you may run into is having to change or rewire the connector,

Dave

Thanks ATA91710.

Given your answer, my post is misleading. The lip seals are less of a problem than the sealing (caulking?) in the end caps. It is a rubbery material which kind of glues the scale element into the aluminium body. We have carefully trimmed off the excess but the problem prevails.

Ah yes, the glass was siliconed into the scale body on those units. If you’re in a pinch, the glass can be removed and reattached.

A quick look at eBay shows a number of units of the 100mm, 150mm, etc. but nothing matching your length of 200mm. I recommend setting up an eBay notification in case anyone lists a 200mm scale. You might want to buy the cheapest unit on eBay and use the head out of it to give yourself a little more life.

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ATA91710 said:

Ah yes, the glass was siliconed into the scale body on those units. If you’re in a pinch, the glass can be removed and reattached.

A quick look at eBay shows a number of units of the 100mm, 150mm, etc. but nothing matching your length of 200mm. I recommend setting up an eBay notification in case anyone lists a 200mm scale. You might want to buy the cheapest unit on eBay and use the head out of it to give yourself a little more life.

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Click to expand...

Thanks, yes, we have been considering rebuilding the scale. It looks like a tricky job to get the glass out without breaking it. Any suggestions? If the adhesive is silicone then as far as I know there is no solvent that can help?

I'm still holding out hope that a cheaper scale can be adapted, but nobody can confirm or deny it is possible.

ADFToolmaker said:

.....
I'm still holding out hope that a cheaper scale can be adapted, but nobody can confirm or deny it is possible.

Click to expand...

I think you can kiss that idea goodbye.
It seems that this is a sine wave scale with a 20 micron pitch. Interpolation done on the reading end. Not only will you need right sine wave spacing but the correct peak to peak voltage for the reading side to work right.
Some top end scale makers may have a match in signals but the cost will be just as high or more and you will have to fit mounting.
RSF, Heidenhain, and even Acu-Rite made scales similar but finding a match would be hard.
Not a made in China DRO type part.
Bob

CarbideBob said:

I think you can kiss that idea goodbye.
It seems that this is a sine wave scale with a 20 micron pitch. Interpolation done on the reading end. Not only will you need right sine wave spacing but the correct peak to peak voltage for the reading side to work right.
Some top end scale makers may have a match in signals but the cost will be just as high or more and you will have to fit mounting.
RSF, Heidenhain, and even Acu-Rite made scales similar but finding a match would be hard.
Not a made in China DRO type part.
Bob

Click to expand...

Thanks Bob, that's the definitive answer I needed.

Actually Bob is partially correct. The AT11N scales are TTL not analog. It was the AT11FN scales which were sin wave. All 6 pin Mitutoyo scales were TTL and all 7 pin Mitutoyo scales were analog. The earlier sin wave scales were 4vpp riding on 5v DC then Mitutoyo changed to 2vpp riding on 2.5v DC.

You are correct that the glass signal period is 20um and that the signal interpolation occurred inside the head. However the signal interpolation is 1x multiplication which results in a 5um TTL edge to edge separation. 5um scales are readily available from common manufacturers such as Acu-Rite and RSF. However, they will require physical adaptation and the reference mark might not be in the same place. So, if you are considering a scale replacement you should just replace it with another Mitutoyo for continuity.

If the glass is still secure enough that you are concerned about breaking it then you shouldn’t try to remove it. Are you absolutely sure it’s the silicone which holds the glass that you are finding inside the scale? It’s very rare for that to happen. If it is then consider cleaning out what you can and then apply a small beed of new silicon to stop the pealing.

Most of the time, scale miscounting is caused by contamination, age or misalignment. Given the age of your scale I bet your issue is simply due to week LEDs on the reader head. Back to my original recommendation to purchase one of the new AT11N scales off eBay and use the head. You might want to consider purchasing one longer than yours so that you can use the lip seals also (if yours are worn).

Good luck!


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