The Shop > CNC
Accurate low cost method of home/zero Axis setting
mc:
As much as I like to disagree with Hanermo, his figures are probably not far off, given my experience of slot sensors.
Looking at the datasheet for the current version of the slot sensor I used (Panasonic PM-45 series), it lists hysteresis as 0.05mm or better, and repeatability as 0.01mm or better.
Given I never noticed any variance on a DTI gauge with 0.01mm intervals, I'd put repeatability at better than 0.005mm. However due to the stepping nature of stepper motors, the stepping probably contributes to the repeatability.
awemawson:
Would those 2 microns possibly be the travel of the ball screw when located by the sensor. So linear travel of screw related to angular travel of opto sensor :scratch:
cnc-it:
--- Quote from: awemawson on March 30, 2019, 11:11:45 AM ---Heidenhain encoders do a similar thing as implemented on Bridgeport Interacts and indeed also on my Beaver Partsmaster.
They drive to the limit switch then look for a 'once per rev' index on the encoder.
--- End quote ---
Yes I found this out the hard way on my Partsmaster. After removing the Z axis encoder for repair I pranged the tool change carousel as the Z axis tool change position had changed by around 3mm! Luckily I got away without any damage :doh:
BillTodd:
Typically, the linear sensor acts as a trigger for locating a rotation sensor , either a motor encoder pulse or a separate lead screw sensor.
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