Z axis problems

[fitz943]

Today, after drilling about 200 #67 holes out of 300+, my z-axis started making a terrible noise. It sounds like a bad vibration with an occasional pop on the z-up moves. After 30 or so more plunges with the z-axis getting lower, the chuck finally hit the face of my material. The chuck had originally been .375" from the surface at the end of the down stroke. I'm drilling into .3125 bendable plywood. I could see the z-axis stall momentarily on the final z-up move before it hit. I checked the rack & pinion for debris, & the bearings for a failure but couldn't find anything. If anyone has any ideas before I take the whole z-axis apart, I would appreciate it. It just seems strange that suddenly the noise changes and I start to get an error in the z height.

[bjwat@comcast.net]

Tom,
Do you have a 'constant force' spring on the Z-axis? It looks like a spring akin to a roll of postage stamps. It may be broken or may have lost it's spring. I'm pretty sure ShopBot sells a replacement & if you have a Colombo, they sell a coil spring replacement as well.

-Brady

[magickeith]

Tom,

First you need to isolate the cause. Do you get this noise when you manually move it up and down with keyboard controls? If no, try jogging it with manual control (hold down CNTRL & PG UP). If yes could you have your jog speed set so high that you are stalling the stepper and loosing steps? Could also be a similar problem if your ramps settings are too fast or too short. Also running in Windows has been known to cause problems similar to this. Try running in MS DOS.

If speed and ramp settings don't seem to be the cause, unplug your z stepper and manually run it up and down. It should move relatively smooth. If not you have a mechanical problem of some sort. If you move the axis up and down you will see a set of holes that line up with the socket screws that adjust the rack and pinion backlash. Have they come loose? Put a wrench on them and check. They are usually locktighted in and so tight you will almost break a wrench to crack them loose. If loose consult tech support on resetting this clearance. If not further dissassembly/ inspection will be required. Contact tech support before attempting further dissassembly/ inspection there's no charge and you are probably going to need their help from this point on. You can call and leave a message or Email 24/7 and someone will get back with you as soon as possible.

Good luck,
Keith

[Mayo]

There's a "constant force" spring ?
I have two of the "screen door" variety on my Z axis. Is one kind considered better than the other?

Everything seems to be working so maybe I better not fix it!

[fitz943]

Just to let you guys know, it ended up being a bad driver. We disassembled the whole z-axis only to find nothing wrong with the mechanicals. We had that figured out by the time Shopbot opened. When I described the noises, they knew exactly what to check. Within 10 minutes, we were back in business drilling the other 200 holes.

[gerald_d]

It is a pity that none of those clever chaps at ShopBot answered your Wednesday post at the beginning of this thread. You would have had a peaceful weekend.