Losing Communication

[Tim Summerer]

Hey,
I know this is a common problem, and I apologize for adding one more post about this, but I need a hand figuring out a lost communication issue.

I have two ShopBot machines. We're using them in a production (16/hr day) environment.

Machine 1 is a PRT Standard 144x60 with RBK box. Wood Frame. 4hp Spindle. Newish Levano PC with 8 GB RAM

Machine 2 is a PRT Standard 96x48 with original box. Steel Frame. PC Router. Old Dell PC.

Both machines have been running at this pace for well over a year. They give me trouble from time to time, but on the whole, perform OK. Lately Machine 1 has been pretty much useless because it keeps losing communication. I've talked with ShopBot and they are having me run a bunch of tests to try to narrow down the problem (they've gone home for the day, so I'll see if anyone here has some ideas).

Attached are the tests I've run and the results. To me, it looks like a grounding issue. It's cool and dry here right now, and nothing else has really changed except the weather.

I've done what I think of as a pretty good job grounding everything. I've got copper wires in my DC tubing, metal tape on the outside of the tubing, all the axis connected with grounding wire, etc. I know there are a lot of theories and opinions regarding grounding so I need some advice from ShopBot users regarding what changes/improvements I may need to make.

It's extremely confusing to me that it seems like Machine 2 is causing the problems in Machine 1. I've attempted to keep them pretty well separated electrically, but they both definitely share the dust collector.

Here is a diagram of my setup. I'll also attach the pdf. What do you think and what would you recommend?

https://www.lucidchart.com/documents...a-7b750af069f2

Red lines = 3 wire cable - black, white, ground
Green lines = 1 wire copper ground

Machine 2 has a metal frame and I haven't worked on attaching it's frame to electrical ground. Should I do this?

Is the wire in the DC tubing supposed to connect to the frame of the machine? Or does that make a (mysterious and elusive) ground loop?

Thanks for your help

[dana_swift]

Hello Tim!

In your test grid "tests.pdf" how reliable is the green Succeed case? Is it always? If so the noise in your shop is exceeding the amount USB can withstand.

First be sure the computers are set up according to the black viper minimum configuration. No unnecessary background activity starving the usb port. (a possible culprit).

Two possible electrical remedy's. First is buy a usb isolator for the machine that is hanging up. Then ground issues between the computer and the shopbot cease to be a factor. USB isolators are not common, then neither are shopbots that freeze, you may have to order one off the internet, I dont know of any place in town here that carries them. A USB isolator can break a ground loop through the USB cable also.

If I read your diagram "shopbots" correctly, you are using flex conduit for part of the ground to shopbot 1. Run a real wire. Around 16 gage or bigger. The red connections in your diagram are a possible source of trouble if there is a neutral that is connected to that green connection shown coming from the box. Ground loops are a huge noise generator. (The most likely culprit).

Ground loops can usually be found with a clamp-on ammeter. Its common to find several AMPS of current flowing in circles in a ground loop. Plenty of current to cause a voltage shift adequate to interfere with an LVDS signal (the electrical method USB uses).

The ground loop issue would be made worse with different combinations of machinery running. My nickle is betting on that issue.

Hope that gives you a couple things to check, and probably remedy the trouble.

Keep us posted.

D

[Tim Summerer]

Thanks for taking a look Dana,

First a few notes on the Tests. Woodcut is opposed to Aircut.
We're trying to totally cease production so we didn't run each test exhaustively. The succeed in Test 4 may be somewhat unreliable - this test was machine 1 cutting by itself with the DC on. I believe my guys tried this this am and it didn't work (but that was before we had our fancy Test Grid). I think if a failure due to Grounding is going to happen in a machine, it's likely to happen no matter which machine is cutting.

I've done everything I know to make sure the computers are set up appropriately. I'll double check that against Black Viper.

I'll look into a USB isolator - I had researched it at a previous time.

Regarding the diagram:
The flex conduit is what runs the power to the Outlet Box which provides power (and ground) to Machine 2.

Currently to ground Machine 1, I have a wire running from the frame to the grounding strip inside the RBK box. It is my understanding (possibly totally wrong) that this ground is then carried out with the red cable (which includes black, white, and green wires) to the surge protector, then breaker box, then rod.
Should I instead be running Machine frame to rod, RBK box to rod, etc?

[Tim Summerer]

Brady,
Thank you as well for your thoughts.

I've got one question right off the bat.

Here's a simple layout of our facility This is looking at the machines from eye level. (kinda). You can see that the wire to carry away Machine 2 static has to travel past/over Machine 1. I've definitely always wondered if it's quicker and easier for the static to just travel down and into Machine 1.

https://www.lucidchart.com/documents...2-3b600a7c4e7c

So... What can I do to avoid this. Obviously the first step is to not let the DustCollector grounding be connected to the bot. It's easy to keep the internal copper wire from touching the SB frame, but what about the spiral of stiff wire in the DustCollection flex tubing. Will/Can static jump from that to the machine frame?

Would there be an advantage to jumping to ground faster and at intervals along the Dust Collection path? (The orange parts in my diagram)

[Brady Watson]

Tim,
The spiral steel wire in the dust hose is there for structural support ONLY - It should not be relied upon for grounding, because it is insulated from the inside of the tube - completely encapsulated in plastic. Therefore, this is why a bare copper wire inside the tube is the preferred method. I would not worry about static jumping from this spiral wire to the machine. Remember - path of least resistance - the static will gravitate towards the bare copper wire instead of the spiral encapsulated in the hose.

-B

[Joe Porter]

Brady, thanks for the "antenna" description of the ground wire in the DC hose. This finally clears up what you all have always talked about as far as grounding the DC hose. You know, it pays to always read these technical type posts even if you are not having that particular problem and not really able to follow the conversation. What you might not understand now maybe will clear up down the road. Especially when you and Dana get to talking, waaay down the road for me....joe

[Brady Watson]

1) Machine 2 has a metal frame and I haven't worked on attaching it's frame to electrical ground. Should I do this?

2) Is the wire in the DC tubing supposed to connect to the frame of the machine?

3) Or does that make a (mysterious and elusive) ground loop?

1) No. Electricity follows the path of least resistance. You want a straight shot to electrical ground on your system. If the ground cable from the dust foot to the dust collector is 25 feet long, and there is a wire/cable from the dust foot to the frame of the machine...which has a ground cable attached to the control box and it is only say 10 feet, guess where the electricity is going to go? A 10' wire has less resistance than a 25' one. Then the electricity has to go somewhere - which could very well be your control board and processor, or the USB cable itself.

2) No. See #1.

3) Yes. You just want a straight run of light BARE copper wire inside the dust collection tubing. It should ONLY be terminated at the DC and nowhere else. Think of it as an antenna for static - only one end gets connected. Non-flux core MIG wire works well for this application.

There are 3 possible reasons for communication to **** out. The first is the computer itself and it's USB hardware. If in doubt, a $30 PCI to USB card is cheap insurance. Pop it in the computer and plug the 2.0 hub, then the Bot into it. Second, static electricity generated from cutting and dust collection - which is usually cured with a single terminated bare wire through the hose. Third, and not often considered, is environment electrical noise. Sometimes 'dirty' power, electrical and magnetic fields in the working area can cause communication problems. Remember, the tether between the Bot and the computer runs on 5v (USB is a 5v device) - so any electrical signal (including static and EMF) can 'stand on' that 5v signal and mess it up. Isolating and curing this type of situation can be tricky and complicated, depending on the source of the noise.

-B

[CantologyLLC]

First post - been lurking for too long. Seems a good place to pipe in. Been running my Desktop hard for over a year with intermittent comm problems. Followed all the usual advice and problems have become much less frequent. But last Saturday morning I had three nasty glitches - all the same: caused bot to lose track of X axis, shut off the router, but kept driving! Tore the material off my vac table pulling 24"hg! Not pretty. Couldn't think of anything else to do to combat this ambush of my day. So I installed the latest beta, which I had heard has more robust comm. No problems since. And I love the new interface. But I don't see the beta discussed anywhere on the forum. Am I missing something?
-Will

[Bob Eustace]

Thanks for the excellent explanation Dana. Does going optical reduce the speed at all do you know? If isolated USB only has one port what do you do with the spindle USB? Sorry for all the questions! Cant wait for you to perfect your static measuring gadget.

[dana_swift]

Bob- the speed of opto-electronices "can" be extremely fast. There is nothing inherently speed limiting about the optical isolation technique.

The person designing the isolator must choose appropriate parts to avoid speed issues, and to achieve efficient power transmission, etc. Nothing is automatic. As consumers, all we can do is buy something and hope the designer did their homework.

Fiber-optic communication is just a long distance form of optical isolation. The speeds they achieve with fiber optic data are just amazing. USB does not run anywhere near that fast, so the presence of the isolator "should" be transparent. I dont recommend blindly putting them in the system, but its worth a try if a problem shows up. They just plug in, so its real easy to unplug and remove them.

For what its worth, I am presuming the hub is next to the computer, and the isolator would be inserted in the cable from the shopbot that plugs into the hub.

If several people try isolators, it will be interesting to post some info on how it is affecting their USB speed test, and any other results they may be noticing. Any takers?

D