Loosing Z

[Tim Lucas]

Really got a struggle going on here

When I run a file through the eCab link my Z is loosing track of where it should be.

It started Friday when I was cutting out some parts and I noticed it was not cutting deep enough - rezeroed Z and started over, still not going as deep as it should. The readout shows its going at the correct depth but its not.

I can Zero Z and move or jog Z up and down and it seems fine but when I run the file (have not tried a V Carve file) it is loosing its mind.

Things I have tried - replacing cable, swapped driver, another collet and bit, replaced stepper, uninstalled the link and reinstalled.

Strange thing is while the file is running I watch the feed speeds XY & Z change the same. In other words I have the tool set to XY 3.0 ips Z 1.5 ips but the readout on the screen shows both of them at 3.0 ips

Anybody else having problems with the link??

I have an older PRT upgraded with the new style Z and an RBK box with 20 tooth Z and 25 tooth XY - What should the value be and where do I check it?

I must have something corrupt in my system ??

Anyway i am open to ideas

Thanks
Tim

[bluesky123]

I have been experiencing similar problems with ShopBot Desktop D2418, which is losing position once every hour or two: I'm surfacing at constant Z, when, all of a sudden, the spindle drops several millimeters down ruining the part (this happened many times and I always verified that the bit didn't move in the collet). While Z-axis drifts down by up to 5 mm, X and Y axes can lose 10...100 mm. One can hear a short and barely noticeable change in the sound, while the spindle jogs or moves, after which one of the coordinates is off.
If I am lucky and I mill a whole part in an hour, all is good. But, for complex jobs, successful outcomes are rare...

Apparently, the position loss is a known problem with ShopBot, a quick search in these forums returns multiple results, e.g.:
http://www.talkshopbot.com/forum/showthread.php?17341-USB-Communications-Dropout

I have just sent a tech support request to ShopBot, but I am not holding my breath that there's an easy fix for that...

[jerry_stanek]

I have been experiencing similar problems with ShopBot Desktop D2418, which is losing position once every hour or two: I'm surfacing at constant Z, when, all of a sudden, the spindle drops several millimeters down ruining the part (this happened many times and I always verified that the bit didn't move in the collet). While Z-axis drifts down by up to 5 mm, X and Y axes can lose 10...100 mm. One can hear a short and barely noticeable change in the sound, while the spindle jogs or moves, after which one of the coordinates is off.
If I am lucky and I mill a whole part in an hour, all is good. But, for complex jobs, successful outcomes are rare...

Apparently, the position loss is a known problem with ShopBot, a quick search in these forums returns multiple results, e.g.:
http://www.talkshopbot.com/forum/showthread.php?17341-USB-Communications-Dropout

I have just sent a tech support request to ShopBot, but I am not holding my breath that there's an easy fix for that...

You know that thread was from 2013 and the problem seems to have been solved. What version software are you using. Have you tried reinstalling the firmware.

[Brady Watson]

Machines can lose position in 2017 too if they are asked to use more power than they are able to deliver. :rolleyes:

What diameter tool are you using? What RPM? Depth of cut? What move speed (MS) ?

-B

[bluesky123]

Apparently, the problem hasn't been solved: Tim's post is dated this December.

I have been using all recent versions of ShopBot software and firmware, updating to the latest as soon as they are published (currently, 3.8.44). The position loss problem has always been present, it happens occasionally and, the longer the job is, the higher is the probability that it would be ruined.

[Brady Watson]

What RPM range & Move Speed (MS) is this happening?

Forget the software for now. You're either pushing the machine too hard or you have a weak stepper driver on the Z.

-B

[scottp55]

Brady,
You don't think static season has anything to do with it...maybe a non-wired DC hose touching the chassis?
Static and making WAY too aggressive passes were the only reason our 2 Desktops ever lost position, besides dirty/loose usb connections.
My shop is down to 30% humidity, and Colorado is probably worse.
Just thinking.
scott

[Brady Watson]

Yes - of course. Static can also cause this...So could a bearing on the Z binding up because people never maintain their machine (replaced several of these on the road) - and probably a few more things.

-B

[Tim Lucas]

Sorry I FAILED to update this post.
It looks like the fix was to adjust the power to the steppers. I upgraded my machine with the new style Z and a RBK box.
When upgrading a PRS the instructions show to turn down the to power from 9 to 6, and this seemed to solve the problem.
I did try other things in the process and was leaning toward static but when it started it was a mild humid day and my collection hose
is grounded good and it would lose position even without dust collection.