Dead spots in DRO scale....

LVLAaron

LVLAaron

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Was having a hell of a time with some parts and noticed my Z axis scale has a dead spot in it. It was late so I've done no investigation.. What should I do? Take it apart, clean it? Any risk of further damage?
 
Take it apart and clean it. Had this happen to my X axis. Although, first swap the connection to the display, to confirm the dead zone follows the read head. Use isopropyl alcohol or something that will dry to a non oily finish.

I cleaned my read head, and it was better, but it still had a (smaller) dead zone. I contacted PM and they sent me a new read head, which fixed the problem.
 
Took it apart... cleaned the read head... but it's still kinda bananas. It's not really a dead spot, it just reads wrong depending how fast or how much you move it. :/
 
Some displays can't or won't update quickly. Thought I saw some complaining about that. It's hard to tell what is wrong from viewing the video. If you connect this axis to a different one on the display, does the display follow the input? (Sway Z & Y cables on the display, which display is wrong now, Z or Y?)

If you got the DRO from PM, I'd shoot them an email about the issue and see what happens. I know they treated me quite well for my DRO issue. Maybe they have another diagnostic test to try, or maybe they will simply send you a new read head.
 
I sent the tech address a note and link to the video.
I'm moving the read head to the end (left) each time... So you can see the different numbers it lands on each time I bring it back to what should be zero. If I move it fast, it will be off several inches.
 
LVLAaron said:
I sent the tech address a note and link to the video.
I'm moving the read head to the end (left) each time... So you can see the different numbers it lands on each time I bring it back to what should be zero. If I move it fast, it will be off several inches.
Click to expand...
That's exactly what would happen on mine. Got a little better after cleaning the head and the glass scale itself, but never went away. Only thing that I could think of that might work (or break things entirely) would be to dip the head into an ultrasonic cleaner. But that's if you are desperate!

I called it the non return to zero problem. Botched a couple of parts before I realized it wasn't me, but the DRO was off.
 
Yeah. I crashed an internal threading tool in a blind hole... :| Lesson learned.
They already have a part coming my way.
 
You cannot move a glass scale like that and get it to read correctly, the alignment of the reader head to the scale must be of very tight specification tolerances otherwise you will get the reading errors like you show. Typically you sweep the the scale mounting position and alignment, there is also a fixed distance between the reader head and the scale. The cheaper scales are more prone to contamination due to poor lip seals, but I have used lots of glass scales in the past and have not seen a specific dead spot, as opposed to random position errors if poorly aligned or contaminated.
 
LVLAaron said:
Yeah. I crashed an internal threading tool in a blind hole... :| Lesson learned.
They already have a part coming my way.
Click to expand...
Ouch.

Good on PM coming through so quickly!
 
mksj said:
You cannot move a glass scale like that and get it to read correctly, the alignment of the reader head to the scale must be of very tight specification tolerances otherwise you will get the reading errors like you show. Typically you sweep the the scale mounting position and alignment, there is also a fixed distance between the reader head and the scale. The cheaper scales are more prone to contamination due to poor lip seals, but I have used lots of glass scales in the past and have not seen a specific dead spot, as opposed to random position errors if poorly aligned or contaminated.
Click to expand...

Understood. It had the same wonkyness on the machine before I touched it.
 
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