Microrouter ver 3 USA

[Kholden]

Description of problem:
Over time, it seems as though the bearings or something similar that hold the XYZ motion components have either worn or loosened. There is no visible damage, but the router machine seems to have a bit of “play” in it which is resulting in a degree of error in precision. Two manifestations of this have been evident for several months now.

1 – when the Z-axis moves down to the point of cutting, when the tool tip touches the material as it starts to cut, the entire z-axis assembly rotates/shifts clockwise upward in the XZ plane (around the Y axis). The shift is small and subtle, but visible. Again, it is as though something has simply loosened.
2 – Motion in the X and Y axes is sometimes a bit choppy – kind of skipping along as though there is something hindering its movement. This is often visible while watching the upper rail of the Y-axis motion for instance, where one can see the lower rails moving steadily along as the upper rail catches (the whole thing twists slightly as the lower motion continues) then the upper rail motion hops to catch up, then hinders again, hops again, etc. Increased lubrication will help this, but not solve it. When the machine is under cutting load in XY, this hindrance will sometimes cause the machine to simply not move to where it should, and because these are stepper motors, not servo motors, the machine doesn’t know that it has lost its position. Continued movements are then shifted in XY relative to the lost move. Obviously this is problematic for part manufacture. We haven’t seen this extreme behavior a lot, and I wouldn’t call it a severe problem, but it is enough to be concerned.

Again, both manifestations seem to act as though something in the machine is either worn or loosened. I have tightened the thrust bearings, (being careful to not over tighten them), and cleaned the machine as best I can short of disassembly, including using compressed air to blow out around and through the bearings, and lubricating of course. This kind of maintenance helps, but the problems haven’t completely gone away, and I presume will only get worse. I’d like to catch them now before they become serious, but I don’t know what else to do… Is there something else to tighten, clean or lubricate? Do the bearings need to be replaced? If so, how?

[Steve]

There are several things here to look at.

First ensure the whole machine is cleaned properly then lubricate with a dry silicone spray especially the rails. Leave to dry then wipe off any excess.

The bearings on the rails are of a dry liner style that can wear but it is not usual to replace them. Where they are fitted into the carriage they are secured with silver coloured Cheese head screws. It is possible to tighten these slightly and this will improve matters. What you described by saying the carriage moves then on another rail it jumps or skips is due to play in the bearings this is called crabbing and can cause loss of position.

TRY AND CLEAN THE MACHINE THEN ADJUST THE BEARING RETAINING SCREWS.

Hopefully this will resolve the problem

[bradders]

The plastic anti backlash inserts that fit around the screw thread that move the axes (The external part been identified on the carriages as a rectangular piece of plastic secured by 3 Allen screws) can also get clogged with debris.

These can be CAREFULLY removed and cleaned but they have to be replaced in the same orientation as which they were removed or "Crabbing" may occur