Why didn't anyone warn me about mag scales on the DRO?

[JimDawson]

An interesting thread. I have been using mag scales on machines for years and have never experienced problems with stray magnetic fields affecting the readings. I do not use the aluminum mounting rails, but rather I stick the mag tape directly to the machine surfaces where possible. The exceptions to this are my mill quill axis and knee axis which are stuck to aluminum mounts. But both of those are well away from any magnetic sources.

I suspect sticking the the tape to a large chunk of iron and thus the read head is also in very close proximity to that chunk of iron has a tendency to shield the read heads from stray magnetic fields, basically 'grounding' the magnetic circuit.

 

[higgite]

An interesting thread. I have been using mag scales on machines for years and have never experienced problems with stray magnetic fields affecting the readings. I do not use the aluminum mounting rails, but rather I stick the mag tape directly to the machine surfaces where possible. The exceptions to this are my mill quill axis and knee axis which are stuck to aluminum mounts. But both of those are well away from any magnetic sources.

I suspect sticking the the tape to a large chunk of iron and thus the read head is also in very close proximity to that chunk of iron has a tendency to shield the read heads from stray magnetic fields, basically 'grounding' the magnetic circuit.

Details, Jim. We need details.
Where did you get the magnetic tape. Peel it off of mounting rails that came in a kit, purchase it separately or what?
How did you stick them to the machine so they wouldn’t peel off when exposed to dirt, oil, grime, flying chips, etc.? Special adhesive? Any special surface prep?

Tom

 

[JimDawson]

Details, Jim. We need details.
Where did you get the magnetic tape. Peel it off of mounting rails that came in a kit, purchase it separately or what?
How did you stick them to the machine so they wouldn’t peel off when exposed to dirt, oil, grime, flying chips, etc.? Special adhesive? Any special surface prep?

Tom

I have never bought a kit, I just buy the individual pieces for what I need. I buy the tape by the meter directly from Ditron, about $25/M. The sticky back is pretty much impervious to all lubricants and cutting fluid. Acetone, MEK, and some other solvents will loosen the tape. Surface prep is clean with acetone, wipe dry, then an alcohol wipe and let dry.

Here is the X axis on my mill


And the Y axis

 

[rwm]

That is amazing that the mag strip tolerates that environment!

 

[JimDawson]

That is amazing that the mag strip tolerates that environment!

Been on there for 10 years. I did replace the X axis strip after I spilled acetone on it and the sticky came loose.

 

[rwm]

FYI you can get Mag tape (among other places) here:

Magnetic Tape and support profiles | M-DRO | CNC - Machine DRO UK

Our full range of Magnetic Tape and support profiles

www.machine-dro.co.uk

 

[rwm]

From the EMS installation guide:

 

[pontiac428]

From the EMS installation guide:

View attachment 459536

What does "close" mean? If the read tape were a floppy disk, it would be fine, I didn't set the magnet on top of the tape, I was 12-24" above the table with it.

 

[MyLilMule]

Who made your scales/DRO? That seems OVERLY sensitive. I have magnetic scales on my BP. The one for the table is on the back of the table, covered by an aluminum shield. I've had mag bases right next to the back edge of the table and haven't had any issues at all.

Maybe the read head is defective? Does this happen on all axis? Try swapping some read heads around? Could the display be defective? Unless you have an MRI machine sitting next to your shop, I fail to see how these could possibly interfere.

 

[WobblyHand]

Can't say why your mag scale is so sensitive, something must be out of whack. Mag scales shouldn't react to a mag holder any appreciable distance away. Think the read head has an issue.

I recall seeing mag tape setups with all sorts of chips being functional. I'd recommend trying a new read head. Can you swap X with Y read heads and see if the behavior is the same? If there's no change then I'd either replace the head or dump everything for glass scales. How long do you want to be without a working DRO? Sometimes you have to be pragmatic just to get stuff done. Else you can stay stuck... Unless you enjoy whacking your head against the wall solving a tough problem! I've been known to do that, far more often than I should have.