Dro Not Reading In Spots

[Baithog]

I thought that I would get the opinion of the more experienced machinists before I call Grizzly. I have a 10 month old G0759. This morning I was going to do some work close to the table. When I got most of the way down the DRO Z axis numbers stopped declining. Almost to the table they again start to read. I usually work off a vice, so I have no idea how long this has been going on. I ran the head up and down several times with no effect. There are no chips around the scale. Do scales go bad? Do they get oxidized or something if you dont travers them once in a while?

 

[RJSakowski]

I thought that I would get the opinion of the more experienced machinists before I call Grizzly. I have a 10 month old G0759. This morning I was going to do some work close to the table. When I got most of the way down the DRO Z axis numbers stopped declining. Almost to the table they again start to read. I usually work off a vice, so I have no idea how long this has been going on. I ran the head up and down several times with no effect. There are no chips around the scale. Do scales go bad? Do they get oxidized or something if you dont travers them once in a while?

It looks like your DRO is their H6091 class DRO of which I have installed on two mills. These use glass scales which are non-contact so there is no issue with corrosion. It sounds like an alignment issue within the scale or possibly a bad cable. You could try flexing the cable to see if it causes the problem. Another thing that you could try would be to interchange the x and z cables. If the problem goes with the cable, it is scale or cable related. If the problem remains on the z axis readout, there is an internal problem withing the readout.

Considering the age of your mill, I would call Grizzly. It is a warranty issue. If it were me, I would expect a replacement scale.


Good luck!

Bob

 

[Holescreek]

Glass scales get dead spots where light oil film builds up on the glass. Try an alcohol soaked Q-tip on the glass to clean it first.

 

[Baithog]

I swapped cables and the problem is not in the cables or the head. It does not look like the scales are meant to be taken apart for cleaning. The scales are fully assembled when received from the factory and the DRO manual shows them assembled in the installation instructions. The DRO manual says nothing about maintenance. It is probably too late to call tonight. Technical is closed already and I doubt the customer service rep has any idea how to maintain machine tools. It may be Monday before I can make much headway.

 

[RJSakowski]

I swapped cables and the problem is not in the cables or the head. It does not look like the scales are meant to be taken apart for cleaning. The scales are fully assembled when received from the factory and the DRO manual shows them assembled in the installation instructions. The DRO manual says nothing about maintenance. It is probably too late to call tonight. Technical is closed already and I doubt the customer service rep has any idea how to maintain machine tools. It may be Monday before I can make much headway.

There are a number of posts, U-Tube videos, etc. on taking the scales apart BUT I WOULDN'T. There is no maintenance for the scales that I am aware off other than keeping the exterior clean. Taking it apart may void your warranty.

I had suggested switching the cables around to confirm that the problem is in the scale. Now that you have confirmed the scale is not functioning, you are ready to talk to Grizzly customer service. They should agree to send you a replacement scale.

Bob

 

[rick9345]

Alignment, string and or dial indicator check, end to end must be parallel with no twist full length for true readings.
Then a phone call to tech.

In my case, machine problems are usually operator error induced

 

[RJSakowski]

Question: When was the last time you checked the readout over the full scale range?

 

[Baithog]

I contacted Grizzly Tech. first thing this morning. They agreed that it was the scale and also agreed that it was not user repairable. I should have the new scale by next Monday. They do not want the old scale back, but recommended that I leave the partially defective one on the machine until the new one arrived. Once I get the old one off, I will look into cleaning it. It may just be as simple as squirting clean ISO into the scale with a lab bottle. It might be useful to have a procedure for cleaning since my warranty expires in a couple of months.

 

[RJSakowski]

Once the new scale is installed and operational, if it was me, I would pull it apart and do an autopsy. But that is me; I like to see what makes things tick or stop ticking.

 

[Baithog]

The new scale fixed the read problem. Installation was not as easy as I expected. I should have been able to mount the new scale to the old base, run an indicator across it and been done. The new scale did not fit the old base. Common problem with off-shore machining. I should have expected it. It took most of the afternoon to get everything aligned. It would have been quicker if I had a few hundred dollars more of indicator holders. The control box kept getting in the way. I took the old scale apart and cleaned the glass with lense cleaner, followed by denatured alcohol, and finally blown dry with reasonably dry air. It still has a section that fails to read. Maybe, if I still had access to a clean room, LSI grade chemicals and dry nitrogen, maybe it would have worked better. I doubt it. I ended up with a working DRO, a couple of nice chunks of aluminum and some metric hardware. I am happy with Griz and their tech department.