Positon errors in new PRS Alpha

[ernie_balch]

The system comes up with proximity switch errors for no apparent reason. I can resume without ill effects.

Just today in the middle of a 3D file it loses position by a quarter inch in X&Y then it starts slamming to a stop every time it changes direction as if it lost the ramping values.

I'm on my 3rd different computer trying to make this system reliable. I'm currently using a 3GHz IBM desktop with 1 gig of ram. There is no network connection, anti virus, automatic update or software that looks for dongles on the system.

The speed test completes in under 10sec and gives a 73% efficiency rating.

The dust collector has a wire running through that is grounded at both ends to minimize static.

I double checked ramping values and everything is at the default values except threshold is 135, and the min distance is 0.15 the XY&Z move speeds are all 4.0 inches per sec.

any ideas?

[GlenP]

Ernie, I am not an electrician but spent some years putting together and servicing electrical control panels for factory automation (plcs, drives etc.). We NEVER grounded both ends of a wire that had the sole purpose of a drain or shield for static electricity. We only grounded one end. Electricity will take the path of least resistance and a wire grounded at both ends would be a complete circuit with very to little to no resistance (no devices in circuit). I was taught that the static electricity would in fact loop in the circuit and not drain properly. As I said I am not an electrician so you might want to ask a industrial electrician about it. You could try disconnecting one end and see if this makes any changes. I only have one end grounded on my machine as well as my dust collector. I ran a seperate oversized wire to the machine and the dust collector and grounded it at my panel.

[Gary Campbell]

Ernie...
I am not an industrial elctrician, but I did stay at a Holiday Inn Express last night. (sorry) We had the same problems. I did a quick search, plus a little cut and paste. Here is the body of an earlier post:

I experienced many of the same problems you explained. The main difference was that my loss of table coordinates were not confined to the Y axis. X and Z were affected also. After many hours to the patient crew at SB Tech Support, here is what solved the problem, or at least cut it down to less than 1 event per week of cutting.

Ground the machine as follows:
1) Install a ground lug that is attached to the ground of your electrical panel. (my electrician did mine) (not to an earth ground or rod)
2) Using #12 or larger stranded wire go from the lug to the aluminum rails (both) of the machine.
3) Using the same attach to the X car extrusion.
4) Using the same Attach to the Y Car (scrape to bare)
5) Using the same Attach to the Z Extrusion
6) While you are there, it wouldn't hurt to attach to the ground wire of the dust foot.
7) Using the same, Attach to the other end of the dust collection hose wire.
8) Using the same, Attach to the control box chassis and VFD Chassis (if using spindle)
Using the same, attach to chassis of SB computer and ground lug of UPS if using.
9) Use a dedicated line for computer with isolated ground.
10) inside the control box, slide a small stranded wire into the serial to usb connector and run this to the ground bus inside the control box
You are now officially grounded.
Use a many strand, high quality, low impedance wire. Use Crimp connectors on the ends and star washers for good contact.
I am not sure if separate home runs or a daisy chain is better, but I daisy chained my setup. I also dipped all the connections in the tinning pot to try and delay the effects that our salt air has on open connections.

Ernie.. as an update.. we had been experiencing a few erroneous stop hits until we installed SB ver3.5.4. none since the install
Gary

[Gary Campbell]

Ernie..
Did some research...
Eliminate 6) above Glen is right...it makes a loop with 7).
Gary

[fleinbach]

I am not an electrician but have been in the electronics business off and on for more than 45 years. I totally agree with the statement about only grounding one end to prevent ground loops. But the statement (not to an earth ground or rod) is wrong. For best results make sure you use your own ground rod properly installed. If you ever measured an electric panel ground you will find it may not have proper ground potential, it may even have quite a bit of voltage on it. A ground rod 8' in legnth should be sufficiant but sometimes if the soil is dry you may need 2 or more spaced a minimum of 5' apart.

[ernie_balch]

Thanks for the help.

I removed the dust collector ground from the shopbot side, and had the same proximity switch error at about the same point in my 3D job.

Next I put in a powered hub and got the speed test up from 73 to 85% effeciency. When air cutting the part I had no failure. Of course the vac hold down and dust collector were off.

Next I will get some wire and ground the system as recommended above. I will also ground the fein Bradyvac system hoses.

I'm holding off the software upgrade to last.

ernie

[GlenP]

ernie, to try and isolate your problem further. try running the file with one item running, either the brady vac or the dust collector and see how that works, do it as an air test again.
It should let you know if one of those are creating the problem or if they are both giving you the problem. I guess I would also run the test with both vacs running and see if your powered hub fixed the issue. Good luck and keep updating your results.

[ed_lang]

Ernie,
While testing, remember if you don't have dust/chips being made, you are not testing your vacuum pickup in the same way as when you are cutting material.

I don't recall what material you are cutting, but if it is not nasty stuff like MDF, you could not run your dust collector for a test run and see if that is where the problem is.

This time of the year I take Bounce dryer sheets and rub one on the chair I sit in to do my design work. The humidity in the shop right now is 58% and when I get up, the next thing I touch gets a static shock. Time for me to bring a Bounce sheet to the shop and rub on my chairs.

Good luck.

[ernie_balch]

Ok another update. Now even While air cutting a 3D file I get limit switch errors. The errors occur at line 4 or line 1500 or line 26000 with no apparent pattern.


Turning off both the Fein vac and dust collector did not solve the problem. leaving these off I ran all the remaining tests.

Unbundling the proximity switch wires made no difference.

Grounding the control box to both side rails and the gantry in a daisy chain made no difference.

Upgrading to 3.5.5 software made no difference.

Turning off limit checking seems to work.

ernie

[Gary Campbell]

Ernie..
Try to figure out which switch it is. You can usually see by the indicator light on the SB3 control panel. If one switch seems to be the culprit, use the VN command to make its value (0)(standard switch) then retest. You may have a bad switch. SB tech supt has a capacitor/resistor work around that seemed to help on my system. It drives up the neg voltage slightly to help eliminate false triggers. Newer boards than mine may not have this problem. After changing a prox switch and grounding (all the way to the Z extrusion) we were able to pull the cap/resis and work witout the constant switch hit message boxes.
Gary

[Gary Campbell]

Ernie..
I forgot.. did you update the firmware with the install of 3.5.5?
Gary

[ernie_balch]

Gary,

The new software reminded me to update the firmware which I did after a few tries. I had to read the screen! (it does not pay to rush) and turn off the control box wait 30 sec then the turn it back on so the firmware updated.

ernie

[Gary Campbell]

Ernie.. I got caught on that one on 3.5.4
Gary

[ernie_balch]

Gary,
Running your test, I find that the Y prox switch is giving all the errors.

For now I can turn the limit checking on to home the stage then turn it off to run parts.

ernie

[Gary Campbell]

Ernie..
Try one last thing. Continue your ground wire to the Y car. Due to lubrication in the bearings the prox ground may be the only ground there. Rather than turining all limit checking off, use the [VN] command and do one at a time. Static can be formed by objects moving thru air. DC and vac are not the only things that create static.
Here is a pic showing the wire coming in from the X extrusion, going out to the Z extrusion


6546
Then the Z


6547
Good Luck!, Gary

[rob_jones]

I was having this problem when I first got started with my shopbot. I thought it was just normal to have the proximity switch error because I had never seen a part file run. When I deleted all Shopbot programs from my computer and re-installed everything again I noticed that he indicaor lights were different on the red screen, and then I noticed I didn't get those errors anymore. It worked for me anyway.