Tramming With Taut Wires

[Kitwn]

Here's a quick video showing how the measurements are made...




Any difference between measurements on the two wires means the gantry is leaning forward or backwards and shims are required on both the front or back mounting bolts of the gantry.

If the difference is different at each end of the Y axis (the rails mounted on the gantry) travel then the Y rails are not parallel and shims are neeeded under one of the rails themselves.

An average of each pair of measurements relates to the height of the spindle above the wires. If this average is different at the two ends of the gantry then the gantry is tilted to the left or right and shims are needed on both mounting bolts at one or other end of the gantry.

The DRO on LinuxCNC displays to the nearest micron. Somewhat optimistic since 800 steps/rev on a 16/10 ballscrew equals 12.5 microns per step, but I think the readings are going to be useful enough to get the machine rather better aligned than it is now.