Z erratic

[ljdm]

Revisiting same Z problem. Doing 3D files, Z will randomly cut some passes deeper, but return to proper depth on other passes. any thoughts?
32747.gif

[myxpykalix]

It looks to me like a "purposeful cut". What i mean by that is that rather than there be something wrong with the physical aspects of the Z axis, there is something in the file telling it to do that. Maybe if you post the whole pic there might be other clues.

What is the origin of the file? Did it start off as a 2d file or 3d? Have other files done the same thing? How was it created? Does this only happen with 3d files?

[ljdm]

Nope, not purposeful - 3D files, even some purchased from Vector 3D. Artcam simulation looks fine. V-carving seems ok, hard to notice this effect on a flat surface with just text. Homemade and purchased 3D files do the same thing. Checked all physical aspects of Z, adjusted rollers, etc.....ordered new pinion, even though this one looks ok, going to change it as a precautionary thing, trying to eliminate any possibilities. Could always send Z to Shopbot, let them go over it. I guess nobody has had this type of problem?

[coach]

I had a v bit go almost through material on some letters and be perfect on the rest of the word.
I was told to e mail the file to shopbot but never did.
But that problem has happened a couple times to me.

[cnc_works]

I would say something is loose in the Z. I know sometimes we take things for granted, like nothing has changed, but I would check the V rollers and the rack and pinion. Use a 2 x 4 as a lever and see if you can find any vertical play.

Donn

[harryball]

I would remove the Z and inspect/suspect everything. I had a similar issue early on and discovered my pinion set screw was not tight. It introduced about 1/8" of randomness to the Z depth. On light cutting (foam, mdf etc...) I had little to no problem, but in wood it was awful.

/RB

[ljdm]

I checked the pinion screw, adjusted v rollers, etc....... It's random, but only seems to be random as far as some passes are deeper, not higher. Too bad I can't afford it right now, perfect excuse for a new 'Bot, huh?

[myxpykalix]

Well mine was just a guess based on the lines because they look consistent all the way across instead of like something is being dragged. I have never experienced this myself. Those that have experienced it would know!

I don't use mine as much as someone like Harry but i'm thankful i've not had problems like some have described here.
although recently when testing some new procedures i have seen my Z change position (can't explain it in detail to replicate it so i'm just watching it in the meantime)

[waynec]

Lou, I've dealt with the same problem with my older PR shopbot. I checked all the usual suspects- the wheels, the springs, the ballscrew, etc.

I found what I thought was the problem with dust getting into the ballscrew bearing. That seemed to fix it at first, but then the problem appeared again.

It ended up being static electricity. I ran a copper ground wire from the dust collector foot, thru the gantry wiring and finally to ground on the back of the controller box. I also grounded the Z axis to the gantry and the gantry to the steel table.

The whole fix took less than an hour. After I did this I never had any more problem with diving Z unless I made an error programming.

Funny thing is that I never noticed any static anywhere. Never had any static shocks, or anything. But it must have been there somewhere.

Install a ground wire and see what happens.

Wayne from White Salmon