My ballscrew z-axis started dropping when I turned off the power to the motors. I took it apart and noticed that the set screws that hold the ballscrew to the bearing in the brake (at bottom) were loose. This allowed the ballscrew to spin even though the brake was working resulting in power off drop.
I tightened the two set screws (Couldn’t tell if there were any flats on the end of the ballscrew. Didn’t seem like there were.) Before I put everything back together, can anyone think of a reason why those set screws should not be tightened? Picture below.
Ed
Hmm, I would contact the factory and verify. When those things go bad it will always losing steps in the positive direction (aka the spindle will dive into the table).
Mine was making a little noise after significant time in use. Avid said to check and tighten those set screws if they had loosened, so I did. Haven’t heard it again in over 6 months.
No lost steps or anything, surely when powered-on the Z motor can support the spindle. I think it’s only there for when there’s no power.
Thanks for the replies. Avid support confirmed tightening the set screws was correct. They also sent me a pdf documenting use of various type of loctite for securing the drag brake if it ever loosens in it’s mounting to the end plate. My brake was securely fastened to the end plate so I didn’t have to worry about that. I’m attaching the PDF in case it might be useful to someone in the future.
Ed
Avid CNC - Drag Brake.pdf (121.2 KB)
If I have a separate counterbalance, do I need the drag brake? Would there be any advantage to removing it?
In my opinion (as a hobbyist not running a production shop), if it hasn’t come loose from the end plate and you aren’t losing steps on downward moves, I wouldn’t remove it.
Ed
From what little time I spent with it, I recall thinking the ballscrew was not full length so you would have to engineer a spacer block and bearing if you removed the drag brake. Looking at the top picture I see the ballscrew end is necked down to fit in the collar so I’m thinking my initial recollection is correct.
