Tramming With Taut Wires

[Kitwn]

This has been a day of measurements, fitting shims, making measurements, adjusting shims, making measurements... repeat and repeat!

I've never done a job like this before and it's been very interesting to go round and round slowly, but very surely, getting closer and closer to optimum each time. The measurement process using the Z axis and it's DRO as the measuring device is not as accurate as a dial gauge but has proved very effective and easy to use. Repeatability has been better than 0.05mm which is hardly world class engineering but is entirely adequate for this job and probably matches the accuracy available from the usual YouTube tramming methods involving leveling a piece of glass on the machine base or simply skimming the base and testing for ridges. We will see when I skim the base of this machine and see how smooth it is.

Having got the gantry rails as accurately aligned as I can it is possible to adjust the spindle bracket vertical. There is significant play in the mounting bolts but by positioning the gantry so that the spindle axis is directly above one of the wires it is possible to adjust the exact position of the bracket so that the probe just touches the wire on each side, indicating the spindle is vertical in this plane to within about .05mm in 600mm (twice the length of the probe). The wiggle room provided by the mounting and it's bolts allows a variation of approximately +- 10mm in the height of the probe relative to the taut wire.

The next job is to skim the machine base so that I can confirm the movement of the Z axis is accurately vertical.
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