Z-Zero Losing Position

[zeke]

My machine PRSstandard 96x48 - 2009 model is losing Z-Zero position. It is OK most of the time, once in a while it gets off by between a 1/4" to 1/2" mostly on the x, yet I have seen the y affected as well sometimes by about 1/16". This is a real challenge not to being able to trust my new machine and not knowing when this is going to happen. Has anyone else experienced this? Thanks for any tips you can provide.

[tkovacs]

Zeke,
You start by saying that z-zero is changing and continue by indicating that x and y change as well.
I assume that you mean that when you "jog home" you are not returning to the expected place.
If all three axis are losing position then it is symptomatic of a more general problem - possibly a grounding or power issue. What speeds are you running at?
Terry

[zeke]

Terry, I am actually losing the x and y during the cutting operation. Guess I need to go back and check the grounding again. Do you know of a way to identify if or where the machine is not properly grounded?

[zeke]

Assuming this is a grounding issue (most likely), I think I am part of the problem. After inspecting my machine, I noticed some grounding wires were not connected. I'm in a garage that is starving for more space and somewhere along the line this must have happened. I think I've got it grounded well per the grounding your shopbot article from Gary. I'm still curious if anyone knows a technique, meter etc., to check for proper grounding or how to correlate a problem such as this to a grounding issue.

[seana]

Zeke,
What are you cutting and your feeds and speeds and jog speeds.
As far as grounding;
The dust collection ground should be in the hose and not touch any metal on the shopbot but run all the way to the dust collector and then to ground.
Next the first place to start is the frame to ground.

My guess is that is feeds and speeds, the reason is you said that it is mostly on the x which is usually the longer cuts or the longer jogs which has better chance of missing a couple of steps.

Hope this might help.
Sean

[tkovacs]

Zeke,
I don't have any magic to check for proper ground. A visual inspection should be good enough. Be sure you have metal to metal connections. As Sean says driving the motors too fast is certainly a common issue that results in lost position. Try an air cut with the router turned off - sometimes you can hear a chatter that may indicate that you are running too fast and the motors are losing steps.

[wberminio]

Zeke
All the above advice is correct.
After you make all you ground connections,
Check your feed speeds.You may need to slow down
some.

Erminio

[zeke]

Thanks for the feedback.

[zeke]

I wonder if I have something wrong with my grounding or a different problem. I went back and checked all my grounding connections to ensure they were tight and I'm still losing position. Now it is really starting to get costly, 2 broken o-flutes and wrong cuts on type1 pvc because of losing position. I hope I can get beyond this soon. Each time I think I may have fixed an issue this same problem comes back. It is very challenging in that it appears the only way to determine if a problem is fixed is to use the machine until this happens again and in the mean time I’ve been thinking the problem is resolved. I’m very anxious to produce some products and realize the wonder of this machine in all it’s glory!!!

Tonight when I was cutting some type1 pvc the x lost it’s place by over 50 inches after about 10 minutes of cutting. I was running at 0.7 ips on both feeds, a comfortable pace, nothing difficult just straight lines before it lost position. I was only taking out 1/16th of material so I wasn’t taxing the machine at all. I then zeroed out again, turned off my dust collection to take that out of the equation and at the onset of starting the cut, the SB3 software quit and paused, I’m perplexed, probably need to call TS. I also looked at the Control box and no apparent problems persist, loose wires, etc..

It would be great if you could review the steps I took to ground my system and provide feedback, I’m not an electrician. I am going to create another post with the pictures to support the steps below that may help to paint the picture. I hope I’m not cancelling out the ground somewhere and over engineered this configuration.

1) A #6 ground wire run from the main service panel (I don’t have any sub panels) grounding lug (on the same lug as the main ground wire) to a junction box affixed to the bot frame.
2) Inside the junction box, there is another lug to distribute the #6 wire to #12.
3) Separate #12 wire from the junction box lug to xrail
4) Separate #12 wire from the junction box lug to other xrail
5) Separate #12 wire from the junction box lug threaded through middle of ‘x’ echain to ycar and attached there, continue from this connection through middle of ‘y’ echain and attach to zcar, then attach to z.
6) Separate #12 wire from the junction box lug to the control box ground, then attach from there onto frame, I scraped the paint off the frame at the connection point.
7) Separate #12 wire from junction box lug through x and y echains to the dust foot. The #12 wire is then connected to both the end of the vac hose internal wire and the external ground wire wrapped around the hose. I purchased the ground wire that is wrapped around the hose from Woodcraft several months ago in a grounding kit.
8) Separate #12 wire from the junction box lug to another lug on my vac stand bare steel upright that is attached to the same aluminum base as the dust collection vacuum and is used to support my vac hose boom arm.
9) Dust collection vacuum system grounded using ground wire (kit wire used) attached to same lug on vac stand as noted in previous step.
10) The dust collection vacuum hose that is attached at the dust collector has it’s internal hose grounding wire attached to the dust collection system grounding bolt using the same grounding kit wire.

[gerryv]

Sounds very frustrating. Maybe you should also post this on the general discussion board to catch the attention of a wider group?

[gerryv]

Hi Zeke, The first topic area in the section above - Shopbot Message Board. It's the one that has the most user traffic.

[loriny]

For what it's worth I was having trouble with Z height and very erratic but it seems good now. I was running 3.6.1 or what ever the software from June was and upgraded it to the latest .
Lorin