CNC update: Skipped steps fixed, ballscrews in

Fixed Stepper missed/skipped steps

With my fixed 2500+ AMD desktop I was able to hook up and test the control board again. A drivertest of the parallel port showed that the computer could provide a steady 25 khz waveform. In fact is was around 26 khz for the test, not really sure why, but it was consistent and as such yielded a solid line with very minor blips in the waveform. I did have the system tuned in the services and applications down to a measily 14 processes in windows XP. So basically, the system was running bare bones.

With the breakout board hooked up, along with the steppers, I was able to move them around smoothly with mach3. Compare the video with the older video where you can visibly see the steppers doing wierd things.

http://www.youtube.com/watch?v=ywBT3VNERIg

Ballscrews in!

I also went to pick up a package from USPS, because they needed a signature and no one was at the door when they arrived at my house. I picked them up and was surprised to see the packaging a bit damaged. I was also concerned that something might have fallen out.

Frankly, I was hoping the ballscrews would have been protected a little better. Oh well, to get those three complete ballscrews with bearings for 375$ shipped is a downright steal. The value well makes up for it.

The condition of all the components was agreeable. The threads on the ballscrew were a little rough, which looked like my first attempts at threading something in my machining class. I'm sure they will do the job of securing the ballscrew though. Surprisingly, some of the bearings were NSK! High quality stuff! Unfortunately, I don't think the angular contact bearings are though - they were some other unknown brand. I'll have to look into that later.

The end machining is the feature i'm most concerned with. The NSK bearings simply wouldn't go on the shaft. They were too tight. I measured them to be something like 9.91 +/-0.01mm and the end machining came in at about 9.99 +/-0.01mm. I think I may have to chuck them up in a lathe and use some emery cloth, or sandpaper to bring them down to an acceptable size. I don't feel like bashing the bearings on with a hammer. Something just doesn't feel right for an interference fit. The stepper couplers are interesting... They look like they will work great with set screws. The interesting bit is that they expand/contract vertically, but they do not twist at all to lose precision. Clever.

With the prospect of machining the ballscrews further, I was concerned about leaving the ballnuts on the ballscrews. From a quick search of cnczone I found this:

http://www.cnczone.com/forums/showthread.php?t=86614

From this thread I've learned that you can remove ballnuts by using a mandrel to hold the balls in place. I also learned that i probably don't need to remove the ballnuts from the ballscrew to machine them. Yay, I like it when things follow the KISS principle. I am contemplating how I will stabilize the ballscrew in a lathe. I'm thinking a live center should do the trick, I just don't want to have to drill the end of the ballscrew for that purpose. I do know they have those brass triple finger support type things (forgot the name) which may do the trick, I just don't want to risk damaging the screw. Perhaps more research is in order about chuking up a ballscrew for machining.