Testing and tuning OF for accuracy

Machines (Original/PRO)
15

I promised I would write the procedure I used to test and adjust the accuracy of the OF, so here it is. Decided to add it to this thread rather than create a new one.

Things you will need:

  1. OF Woodworker (same process for machinist, but adjust sizes)
  2. an accurate 36" ruler (a mm rule would be easier, but I didn’t have one)
  3. 1/4" shank, 1/4" 45 degree v-bit (larger bits will work, but makes it more difficult to see)
  4. Blue tape or masking tape
  5. Optional - fine grained 12" machinist ruler

Process:

  1. Put the v-bit into the router collet and tighten down
  2. Home the machine
  3. Jog the machine back (Y-) 100mm, and right 100mm (X+).
  4. Tape the 36" ruler to the waste board in the X direction.
    ** Ensure the ruler is parallel to the Y axis, or collinear with the X axis (your choice ;))
    ** Place the ruler near the front of the waste board, but not so far forward the bit won’t reach the ruler
  5. Jog the machine so the v-bit is centered over the 1" mark on the ruler. This is your starting point.
  6. Zero the X and Y coordinates
  7. In the MDI section of the OF controller, type the following commands, pressing play after each one.
  • G91
  • G20
  • G1 X30 F100
    ** G91 sets the machine to relative positioning mode
    ** G20 sets the machine to imperial (inch) mode
    ** G1 X30 moves the machine right, 30", feed rate of 100 in/min
  1. Check if the v-bit is completely centered on the 30" mark of the ruler.
    ** If it is, congratulations, the machine is well calibrated in the X direction. Jump to step 18
    ** Assuming the machine needs some correction, continue on in the process
  2. Using the machinist ruler, measure the distance from the v-bit to the 30" mark. This is your error or offset. Let’s assume the error is +0.125".
  3. In the MDI section of the OF controller, type the following command and press play
  • G1 X-30
    ** this jogs the machine back to the zero position we set in step 6.
  1. Calculate the offset for the error discovered in Step 9.
  • Adjustment Factor = Fa = (Distance Traveled/Distance Commanded)
  • Example, Fa = 30.125/30 = 1.004166666666667 = 1.004167 (distance traveled = 30" + 0.125")
  1. In the OF controller SW, click the menu expansion icon in the top left and click on ‘Motor 0’
  2. Scroll down to the option “travel-per-rev” under the “Motion” section. You need to adjust this value to compensate for the error.
  3. The default value for the travel-per-rev is 10mm. Multiply the value times the offset (Fa).
  • 10*1.004167 = 10.04167.
  1. Enter the new value (ex, 10.04167) into the text box and click Save in the top left.
  2. In the MDI section of the OF controller, type the following commands, pressing play after each one.
  • G1 X30
    ** G1 X30 moves the machine right, 30"
  1. Remeasure the offset, if any. If there is still an offset, restart the process at step 10.
  2. If no offset, then repeat the process for the Y direction with the following changes:
  • G1 Y30 instead of G1 X30 for step 7 & 16
  • G1 Y-30 instead of G1 X-30 for Step 10
  • Motor 1 instead of Motor 0 for Step 16

I hope this is helpful for folks and if anyone has questions, let me know.

-Tom

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