What went wrong?

[BodaciousBrian]

Well, until today I have been screwing up. I think I can finally blame the mill!
I was making a hollowed out cylinder from a larger round piece when i noticed these stairs forming on the left side of the work piece, along the x axis. They formed with every step down. On the inside of the cylinder, only 1 stair formed halfway down on the right side of the x axis. It's supposed to be a nice smooth finish. What could have caused this?

[Jeff-Birt]

Your X-axis is loosing steps or your spindle is not trammed (square to bed) properly. I would first tram the spindle and then look at why you were missing steps.

Missed steps can come from a poor quality pulse stream from the PC, trying to feed too fast into the work, etc.

[awetmore]

Those steps look pretty big for a Taig too. What is your depth of cut and feed rate?

[BodaciousBrian]

.1 depth, 30% cut on a 1/2" bit, at 4ipm, at the second lowest spindle speed setting.

I don't think its a tramming issue becasue the other side of the work piece ended up perfect.

I can actually move the table along the x axis with my hands, just jerking it to the side. it moves as much as those steps are deep.

The day before it was running fine. But the first thing i did to start my day was was manage to knock the work piece loose, and jam the bit. I turned the spindle off before i turned mach off, so the X axis did try to move before i hit the estop. I must have knocked something loose, or broken something.

Later today I think i will follow the guide for a complete tune up, and hopefully i wont find any damage and adjusting the backlash nuts and gibs will fix it. I've never done anything like that before though! I'll check back here before i do it, just in case that is a bad idea =).

[awetmore]

The other side is "perfect" because you can't get inverted steps with a normal end mill. It is probably still stepping over too much and when it is supposed to just be milling the bottom step it is doing all four steps worth.

.1 DOC is very deep for these mills in aluminum. 1/2" cutter is also pretty big. It would be interesting to hear others experiences with them, but I run 1/4" or 3/16" cutters at a high RPM, low DOC, and a fairly high feed rate. That puts a lot less stress on everything.

It does sound like checking the nut and adjusting backlash and gib tightness is the next useful step.

[BodaciousBrian]

I took it apart and adjusted the backlash nut, and cleaned a MASSIVE amount of oil out. Ive been oiling it every day, apparently that is to much. I just ran a test in a block of wood and all is well now. I really dont know what happend but my best guess is that the x axis plate that connects the screw and stepper to the table was loose.

Thanks for the help!

[themedulla]

That plate that connects the x-axis is definitely capable of giving you those headaches.

You might be losing steps, though. Just because it didn't happen in your test block doesn't mean the problem is gone necessarily.

I have recently begun to suspect my machine was losing steps in the x axis. I believe the problem has been that my pc was not sending out a quality pulse stream. This is probably due to windows xp and running too much other stuff with mach3.

If it happens again, you might think about cleaning up your install or getting a smooth stepper.