Do scales need an index? << answered >>

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tblough
Posts: 115
Joined: Tue Mar 22, 2016 10:03 am
Acorn CNC Controller: No
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Oak CNC controller: Yes
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Do scales need an index? << answered >>

Post by tblough » Mon Jan 01, 2018 2:27 pm

I have an extra 1micron glass scale hanging around and I was considering adding it to my lathe while I was still in the conversion process with hopes of one day using it for Z-axis positioning. Right now on my OAK, I have encoders 1&2 as feedback from my motors, encoders 3&4 as X&Z handwheels, encoder 5 is a glass scale on X for future use as positioning feedback, and encoder 6 is my spindle.

That leaves me with encoder 12, the MPG input, unused, and hence my question if I can use a scale for feedback without the index channel connected. I believe these Acu-Rite scales have a index count every 50mm but I don't believe the Centroid control uses them. I'd like to verify this before I go through the trouble of making an adapter cable. If not, it looks like I'll probably end up moving one of the handwheel inputs to the MPG encoder, and then putting the scale on encoder 3 or 4.
Cheers,

Tom
Confidence is the feeling you have before you fully understand the situation.

cncsnw
Posts: 342
Joined: Wed Mar 24, 2010 5:48 pm

Re: Do scales need an index?

Post by cncsnw » Tue Jan 02, 2018 6:02 pm

I think the MPG encoder input is number 15 (not 12).

No, the scale does not need an index pulse.

The control will home using the motor encoder and its index pulse. Only after it is done homing will it enable the scale feedback.

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