Z Axis takes dive while cutting

[nick]

I am having the problem where I am trying to rough in some 3D work and while in my rough pass, the Z axis takes a plunge deeper than called for in the program.

I am using 3D raster for rough in. This error is not in the program, I have checked.

I will happen with the same program...but at different times...some at the beginning, at the end...and in the middle...it's driving me crazy.

A few helpful hints...

I had a slight studder which I found to be that an adjustment to the roller bearing would correct.

When powered, there is no play in the Z Axis...tight.

Powered down, you can apply finger pressure and the Z will fall gradually.

Collet in good shape.
Operator going nuts...

[nick]

PRS Standard
2.2 HSD Spindle

[dana_swift]

have you had this problem occur when you were watching it? That will give you the best clue as to where to start looking for the solution.

Does it only happen during roughing, or can the problem occur anytime?

[steve4460]

How fast where you running when this happend , and what version of USB pot do you have ?.
bot on

[artisan]

Nick, I used to experience this years ago....and while you say it's not in the software.....I'd bet you it is. Install the absolute latest version of the Shopbot operating software. Make note of the plunge and check your model in the software....I'll bet there's a whole in your mesh or some anomaly there. Raindrop Geomagic is the best software I've found for editing pointclouds and meshes. Good Luck....D

[Brady Watson]

Not for nothing...but Geomagic starts at $20k and goes up from there...

I would pin it on either running too fast (MS) or your control software is out of date. There is an outside chance that you have a 'tired' stepper driver on the Z.

-B

[ljdm]

Any way to wake up the tired driver? Wondering if my Z problems are the result of a tired/weak driver? Which is more likely - tired driver, or tired stepper motor? I'll go for the 4G, new parts all around, but wish I could tell if that would solve things before I buy, just in case it's something else I need to buy first.

[ljdm]

Brady - not being a wise as*, I like the description "tired". Not knowing enough about the electronic end of the 'Bot, truly wondering if a weak/tired driver or stepper could cause my Z problems.

[GlenP]

Nick. I have a PRS Standard which is only a few months old and my Z will fall slowly after the power is off as well. I beleive they just have too weak of springs on the axis to keep it up when not under power. I only had this happen after installing the dust boot to the machine. I had a similar thing happen to my machine on Thursday afternoon when cutting the 3d sample that came in the Get carving quickly samples that came with the machine. You can see my post in the troubleshooting area. I am going to try a new usb card in my computer as I am running a dell. My communications is at around 73% and nothing else running in the background. I have cut it before with no issues. Am going to try it again tomorrow.

[Brady Watson]

Lou,
I've seen the PRT 1/4 stepping drivers get weak...meaning that they seem OK when speeds are kept at 1 IPS or lower, but above that they lose position. I think your issue is related to some backlash in the Z pinion (probably worn pinion) and the 1/4 stepping drivers can't move in steps small enough - thus showing some deviation in Z in your parts.

-B

[mountie1808]

I've been having this same problem. While roughing some wood for a 3D carve, the Z axis just decides to dive into the material a good inch or more than it should. I've looked at the toolpaths and there is no abberation there. Most recently it happened with a 1/2" bit moving 1.5 ips, latest software all around, new gecko board.

I'll be watching this thread to see what other possibilities it could be.

Mike

[nick]

We'll after careful review it was a combination of two things:

A: Less than .375" of shank in collet on a 2" OAL ballnose 1/4".
B: Dirt inside the collet.

You can figure out the rest.

Lets mark this up as learning by doing.

Nick