Re: [CAD_CAM_EDM_DRO] Linear Scales

Paul wrote:

> Hi Jon & Sven Peter
>
> The scale is tucked up under the bed (where a rack would normally be on a
> manual machine) with the read head sitting below it. The end caps are sealed
> from the last time I had the thing apart - Just can't see how the oils could
> get past the sealing lips and up onto the glass scale.

I suspect it is a wick phenomenon. So, by lips, you mean it has the plastic
strips that are supposed to close up when the arm is not at that spot. (Not like the
Teledyne/Gurley design with the recirculating steel band.) Yes, it is pretty hard to see
how oil could drip up, but if the machine is left without moving for a long time, a
film of oil can work down the arm and then back up inside the scale's housing.
Especially if a pool of oil can accumulate on the arm close to the lips, it can slowly
work its way in. When enough oil has gotten inside, then a sudden movement of
the read head may cause the drop to break up and splash onto the scale. Anyway, this
is about the only way I can figure out that oil got inside. A combination of really
high surface tension and capillary action, and sitting in one place for a long time.

>
> The compressed air feed might help - I would need to make a nipple up to hook
> up to the compressor.

Before you do this, you should make sure that the air you put into the scale
will be extremely clean, or you could make the problem much worse. Also, if the
problem is caused by sitting for long periods, then the air might only be helpful
if it is turned on all the time. This air purging may be of more use in machines where
they use massive coolant sprays that get inside everything, rather than the
situation of capillary creeping over time.

Jon