Skip to main content

MachPro M31 Configuring a Master Slave Axis Gantry

This only applies to master and slave axes on a gantry. If you are trying to align the tables on a dual table router, use the home offsets in MachPro. Pull down Configure -> Control ->  Homing / Soft Limits tab.

Square the gantry mechanically 

The gantry and table need to be mechanically squared to each other so that the gantry remains square to the table over the full length of its travel. This is also a good time to check all axes for backlash and do any needed maintenance to remove the backlash. 

Configure the master and slave axes.

  • Pull down Configure -> Control -> and select Axis Mapping
  • On the axis that will be slaved, pull down the motor selector and select the top blank entry
  • On the axis that will be the master, pull down the Slave 1 motor selector and select the motor that you just removed from your slaved axis. 

  • image.png

  • Close this window

When the gantry homes, the slave axis can be set to move a small offset to square the gantry to the table. There are two home sensor configurations that will work. 

Pull down Configure -> Plugins -> M31

Both the master and slave motors need to be configured to home to a sensor. The specific sensor mapping for each configuration is shown below.  

image.png

Home sensors on both axes

  • If you have homing sensors on both the master and slave axis, then select the Independent Master-Slave Home box on both the master and slave motors. This tells the M31 that each motor will home to its own home sensor.
  • Close the M31 Config window.

    image.png

  • Configure each motor with its own input home sensor.
  • Pull down Configure -> Control -> and select Input Signals

  • image.png

  • In this example Motor 0 is homing to the sensor wired to M31 1D1.01.09. Motor 1 is homing to the sensor wired to to M31 1D1.01.13
  • Verify that each home sensor triggers correctly so that the gantry will home correctly. 
  • Move down to the Align the gantry section

Home sensor only on the master axis

Pull down Configure -> Plugins -> M31

  • If you only have one home sensor, on the master axis, then deselect the Independent Master-Slave Home box on both the master and slave motors. This tells the M31 that both axes will use the same home sensor.
  • Close the M31 Config window.

    image.png

  • Map the home sensors for both axes. 
  • Pull down Configure -> Control -> and select Input Signals

  • image.png

  • In this example, both motors are mapped to use the same physical home sensor, which is wired to M31 1D1.01.09
  • Verify that the single home sensor triggers properly and the gantry homes correctly. 

Align the gantry

This is one method among many and you are welcome to use other methods.

  • Square the gantry mechanically first. The software method below will use motor torque to maintain squareness beyond what can be accomplished mechanically. There are limits to how much the motors can do.
  • The wear on the racks or ball screws is not even across the whole unit. Typically there will be more wear in the middle. On an older machine, do the squaring process with the head in the central area of the table to achieve the most useful results.
  • Typically one type of material is used when you need the most accuracy. Use scrap of that material type for your testing.  The materials need to be hard enough that you can accurately measure them with a set of calipers.
  • If you have not used your calipers recently, review the instructions for your calipers to obtain the most accurate measurements.
  • Expect this job to take several hours

Measure the width of the table. That will typically be a whole number of feet. If you're squaring an imperial manufactured machine in a metric shop, continue to use metric measurements.

  1. Cut a square and measure corner-to-corner diagonally. Or, drill a 4-hole square pattern and measure corner-to-corner on that pattern. 
    • The long diagonal line will point to the home sensor of the axis that needs to have be corrected.
    • Larger squares yield better results, but the squares need to be small enough to measure corner-to-corner diagonally with your calipers.
    • Cut the squares away from the edge so that the material is held in place during the entire cut.
    • Cut the lead-in and lead-out along one of the edges rather than at a corner
  2. Your square is likely a parallelogram - even slightly. The image below shows exaggerated parallelograms to clarify the problem to be solved.  

    image.png

  3. Pull down Configure -> Plugins -> M31

image.png

image.png
The master motor Slave Misalignment value will always be set to 0.

The slave motor Homing block is where all of the adjustments will be made. 

The units are your machine's calibration units - either inches or millimeters.

  • Ensure that the speeds for Back Off and Squaring are appropriate for gantry squaring movements. 
  • Set the Squaring Limit to the maximum distance you want the slave side of the gantry to move to square the gantry.
  1. Multiply the amount the square is off by the width of the machine and enter that value into the Slave Misalignment field.
    • If your machine has an 8 foot wide table, and you cut a 1 foot square, and it was off by -0.005
    • 8 * -0.005 = -0.040
    • table width * amount of offset needed = Slave Misalignment offset
  2. Move to a clear spot on the work piece and cut another square
  3. Measure the new square, multiply the error amount by your table width and add it to your existing offset. Part of your first value was likely taken up by backlash. Your next square should be very close.
  4. Cut another square and repeat the process. Measure the new square, multiply the error amount by your table width and add it to your existing offset
  5. Repeat the process until you have the quality you need

Back to top