| While waiting for the new stepper drivers to come, I decided to do a little work on cleaning up the ORAC. I noticed that turning the long-axis pulley by hand was quite hard - but expected that this was because the stepper motor was attached. However, when I removed the stepper motor from the lathe - it was still gritty, and very hard to turn! Oh ho!
Pulling back the telescopic ballscrew-covers I could see the ballscrew was still shiny and non-rusted.. so what's causing all the friction then? The ways were mostly clean - but there was grime and gunk on them, so I cleaned them up and relubed them. The telescopic covers were actually very-hard to move by hand and were actually sticking - they had just enough corrosion on them to cause them to bind rather than telescoping as they should. So I cleaned them up too (I was tempted to use Cola after watching an episode of MythBusters). |
However, even with the covers clean, and even with pulling them back by hand so they were putting no force on the carriage, the ballscrew still did not turn easily. I was beginning to get the fear. I was afraid of removing the ballscrew as I suspected the moment I loosed the bearing/mounting blocks they would spring-off and be under preload, thus preventing me ever putting the ORAC back together again. Fortunately, this was not the case - it seems that the end-bearing block with the pulley on has the preload, and the other block (towards the tailstock) just idly supports the ballscrew end. Looking at the ballscrew assembly made me realize how high quality this machine actually is - this thing looks expensive.
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With the ballscrew off, the carriage slides beautifully back and forth by hand with very little friction. Another relief. The ballscrew however, as feared, does not turn very easily. In addition, even the preload bearing block is quite tight to turn with a gritty feeling. I clamped back the front telescopic ways and began cleaning up the ballscrew - there was some nasty oil/grease on it the color of liverjuices. Drinking, smoking, crack-addled mans liverjuices. It smelt about the same, too. Standing it vertically (both ways), I've been squirting WD-40 into it and winding it up and down.. so far to some little effect, though some sharp prickly magnetic splinters have now lodged in my fingers. |
My next thought is to post to the CNC group, get some advice, as I'm getting dangerously close to the conclusion that I shall need to Open the Ballnut. I have some thoughts on this:
1) It's preloaded, maybe preloaded ballscrews are hard to turn?
2) You'll never put it back together!
3) Maybe there's some gunk in there...
4) You'll never put it back together!
So naturally, I'm hesitant to let all those little balls out..
Think I'll disassemble the bearing block though, relube and retighten so it's moving smoothly. Considering the risk in opening the ballnut, it's well-worth my time to squirt WD40 in there for at least 3 hours, before coming to dangerous ball-nut busting conclusions... |
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