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z-axis motor small gear very close to body

#302 (closed) noted issues with the z-axis small gear binding on the body. The comments on that ended with a modification to the instructions to make it clear that the screws should be flush with the top of the small gear, !396 (merged).

I have been looking at the z-axis, and happened to put the motor on without the z-axis gear. The design gives very little space between the small gear on the z-axis motor and the base of the cut-out in the z-axis casing. It is probably ~0.5mm. It is not very clear in a static image of the render, but it is very close both on the render and on a real microscope.
image

Clearly this is not a significant practical problem, many microscopes have been built successfully and I have never seen an actual problem with any of mine. However it might be useful to give a little more space here.

  • The small gears are taller than they need to be to mesh with the large gears. Making the gear shorter would be the simplest change, but the size of the screws is a limiting factor. I thought that the screw heads sat flush on top of the motor spindle, but there does seem to be 0.5-1mm free space that could be removed (in the render and in the real mounted gear).
    image
    edit: The apparent gap in the render is from a rendering bug #434 (closed). However it is the case that there is a small gap in reality in my gears mounted on motors, with the gears pushed fully home. This may be a variation in shaft length of different motors.
    I don't know whether the spindle length is well defined in the motors that we use.
  • #302 (closed) suggested making the cut-out in the z-axis casing deeper. There is probably just enough space to make it deeper without cutting through at the front by the z-axis upper flexure.
  • As the gears are long and extend past the bottom of the toothed part of the large gears, the motor could be mounted higher up function motor_lug_h() = 11; defines this height, and seems to be used for all of the other parts of the design, so that the cable tidies etc behave if it is changed to 11.5mm or 12mm. There are some parts of the z-axis cut-out where the hight is more hard-wired and would need adjusting to make this change. The lugs could be made higher for only the z-axis, not for x and y where it is not needed.
Edited by William Wadsworth