Z Axis Shifts — A LOT

[waynelocke]

When cutting about a 350 line file for shutters about 60 inches long my PRT began cutting progressively deeper. I redid the Vector file and made a new toolpath. After aircutting the path it is over 3/8" too deep. I was hopeful of getting this done today.
Wayne Locke

[r39791@aol.com]

I havent been here in quite a while,I took notice of your name...mine is robert lock. I have had one of these things for about...3-4 years, Email me at r39791@aol.com (mailto:r39791@aol.com)

[rgbrown@itexas.net]

Wayne,

Could you be "Loosing steps" on your "Z"? Causes might be dirty rails, binding bearing or broken lift spring.

Stepper Motor would try to lift router, stall and loose steps. Possibly lower Jog speed on Z might help.


Ron Brown

[gerald_d]

This question gets asked frequently and I would like to be able to point somebody to the Frequently Asked Questions (FAQ) page - do we have one?

Mayo must be tired of telling everyone to check their ramp settings (and the rule of thumb that works for him), I know that I am starting to avoid replying to FAQ's. . . . .


And another thing . . . . .

Could somebody design a "Stress Test" for a ShopBot so that one could find 90% of the problems before that critical Sunday overtime job comes along?

[gkling]

A similar Z axis problem with mine was caused by a loose set screw, which only slipped when lifting the z axis but not when lowering, thus incrementally increasing the depth as file progressed.

[john]

We had this problem and i think we figure that our Vaccume was not grounded well enough.
we move the ground closer to the pickup point and havent had the problem since

John

[Eric Lamoray]

I have just been through a whole pile of z-axis trouble on my new PRT equipped with a Columbo spindle. You need to check your bearings on the Z-axis and make sure they are moving freely. You have to turn off the control box and disconnect the wire connections first. It turned out mine had the wrong washers behind the bearings and they were acting as disc brakes. The larger z axis motor for the Columbo then had the power to warp the bolts! This caused the z axis to hang up in places, miss steps and keep cutting deeper. We also then had more troubles ( but smaller )and had to run a grounding wire in our dust pickup. We also run two y axis motors and had to have Shopbot modify the driver board to remove some interference that was causing a z axis problem as well. I've got to admit that the folks at Shopbot did do their best to get everything solved as quickly as they could.

Eric

[sheldon@dingwallguitars.com]

Wayne,

Are you trying to cut any arcs in 3D?

If they are not broken into line segments, the Z axis will do funny things similar to what you're experiencing.

[waynelocke]

I'm sorry. I should have responded sooner. ShopBot said that there is a capacitor problem on some of the controll boards. Apparently the capacitor blows and the z axis keeps going deeper. The day after my post SB sent me a new board which solved the problem. Thanks for the responses and thanks Shopbot.
Sincerely,
Wayne Locke

[waynelocke]

Sheldon,
I am cutting arcs with the new board with no problem and have never had a problem with arcs before but thanks for the advice. It's something to look at next time something like this happens.
Wayne locke