Quite an Unusual one

[Boyan Silyavski]

Brings back memories...

that creation of yours is exactly what inspired me for my Z

Anyway. How have you ensured alignment of the Z-rails - both their spacing (parallel to Y) and parallelism? I can't see any features for alignment, so either you milled reference edges in after assembly, spent time with a DTI and straight edge, or (I doubt) didn't do it? It almost looks like the spindle is just clamped by the plates with the arc-section cutout? If so I'd be a bit concerned about maintaining the accuracy of the rail alignment.

First of all all steel there was laser cut and holes laser drilled, which helped a lot /0.01-0.03mm accuracy of all cut pieces/. Then the aluminum pieces were machined <0.01mm

So knowing that the aluminum pieces were precise, i mounted first the rails on the separate side pieces, checking them to be tight corner fit against another piece of aluminum and straight edge. Later i mounted the 3 sides of the box using , straight edge, precise squares and digital caliper. So now i knew they were parallel to each other in all planes, /same distance/. Then i checked if the spindle enters and it was tight fit just easy enough to slide.

That told me till here everything is perfect/ cause the spindle was machined before 99.8mm OD. We were at the point of machining it and checked it against DTI and it seemed it was not necessary. That is the "good" original spindle with the 4 bearings.

Then knowing that the spindle box is mounted together under 0.01mm i just screwed to the side bearing blocks the side steel plates checking them flat and square against flat surface. Then i used some small clamps to not let them move back and forth.

So as all was mounted together maintaining that precision i laid it down carefully on top of the back Z plate. Now as you can guess the Z plate was not perfectly flat. So i spot welded the side plates/together with the aluminum assembly/ to the Z plate, but only at one side that so the previous assembly is square left right. See pictures above. I used also some clamps not to let it twist left right. Then i force clamped all down to the steel back Z plate , so now it was square and flat / cause the steel side plates wer cut by laser 0.01mm , remember? and i have mounted them perfectly flat against flat plate/ .


So now all was 0.01mm mounted together. I just carefully soldered spot by spot, careful not to heat the bearing blocks.


Later i took out all the aluminum assembly together with the bearing blocks and painted the steel assembly , masking the sides where the bearing blocks were meant to enter later So at certain places there is no paint, to ensure tight fit and not spoil the accuracy.

Same must be done for the back at the place where the ball screw nut housing on the gantry will be fixed to the back Z plate. I just left 1mm space in the drawing, to be shimmed, but due to 1mm less epoxy height, it was tight fit.

What i would say that a sincere judging helps here, one should not lie to himself and want to speed things, cause these are the moments where accuracy may be lost and accumulated.

So I fit the steel Z assembly to the gantry and squared it using the vertical Z bearing block surfaces to a straight edge across the long rails. Then i resquared the gantry ball screw, loosening it, going one end, tighten, going another end tighten and repeat. This to have the Exact same travel as the rails

So when i fit the aluminum assembly i had only to square it front back/ again using the long straight edge across long rails. See photo above. Then tightened the bearing blocks to the . That simple.

Something should be clear though. everything was designed to fit together using only 2 precision squares and 1m and 2m straight edges. No dial indicator was necessary at any moment. Everything was judged by the tight fit of the squares to surfaces and straight edges. I did so with the first machine i build and achieved 0.01mm precision.

So basically i will not use DTI until the moment i have the machine running. from experience it seems i can notice with naked eyes 0.05mm gaps without problem against the straight edge/ the epoxy story/ so i am happy that everything is tight fit.

When all ready i will check with dti and straight edge and report. But for now it seems i maintain the same precision as the first build and on that size of machine, well ... i am happy