Electronic Noise

[qleapp]

Let me start off by saying I do not own a Shopbot yet but plan on buying one next year. I have been reading the posts here for quite some time and have seen a lot of these 'electronic noise' issues occurring, maybe even getting worse not better. The question I have is if Shopbot is aware of this (well documented) issue why haven’t they built grounding into their harnesses or use some type of shielding on their equipment / cabling? Why are owners required to engineer a fix through trial and error, wasting time and possibly materials?

[harryball]

I don't think the problem is that wide spread first of it and grounding your machine is not something Sbot and make you do. I've not heard of anyone with a properly grounded machine having issue. I grounded my machine when I installed it and I've never had a problem.

Robert

[richards]

Many of the 'electrical noise' problems are self-inflicted. Depending on how you run the cables from the control box to the motors, how and where you mount the control box, whether you use a router or a spindle, whether you connect the computer to the same power line as the controller, etc. all affect the amount of noise that your system has to deal with. In addition, in an industrial area, much of the electrical noise can be generated by other companies that get power from the same transformer as you. Not everyone needs line and load reactors and EFI filters on their spindles, so adding those components would be a waste of $750 for those who receive clean power and for those who don't run any other 'sensitive' equipment in their shop. Every shop that I've ever visited has a different way of connecting a dust collector to their machine. Also, those of us who have shops in the deseret might have a much greater problem than those who live where the air is always humid. In other words, it would be nearly impossible for Shopbot to have a single generic fix for everyone.

[knight_toolworks]

is it an issue to have your computer on the sale line as the controller?

[myxpykalix]

As mike says some of the electronic noise is self induced like static electricity. Many times its the root of problems as it was for me. I kept getting file stoppages and was told to ground my dust control system with copper wire and i have not had any problems since.

[richards]

Steve,
Having the computer on an entirely different circuit can cause ground loops. I run my equipment from my garage shop that is attached to my house. The computer is on the circuit that feeds some of the lights inside the house and the overhead garage lights. It originates at the main panel. The Shopbot and all shop equipment are fed from a sub-panel that I installed in the garage. There is a slight ground loop between the Shopbot ground and the computer ground (meaning that I can measure 2V when I probe just the two ground lines). That can be a problem.

I should have installed the computer on the same line that feeds the Shopbot's control box; however, after I grounded the computer's case to the same common ground point on the controller that everything else is grounded to, I've had no problems.

[knight_toolworks]

My desktop had connection issues till I ran a ground from the box to the computer. but the laptop has been good. but I plan on getting a outlet install on the cnc wiring for the computer anyway. glad it is a good idea.

[byoc]

As someone who owns a business that sells a product that requires user assembly, I too have my own forum that is primarily used for tech support for the products I sell. While there is a lot of discussion between the "regulars", the majority of the posts are tech support. So if you are taking your "sample population" from a source where most of what you see & read are people who are having problems, you are going to assume that the product has a flaw. I see it all the time...4 or 5 people have a similar issue and they think there should be a recall. But they don't realize that there are 100's, even 1000's of other customers that had no problems at all.

Having said that, as someone who is also going through "electric noise" issues, I think SB's owner's manual is grossly lacking in the wiring dept. As far as I can tell, the Control box only takes a 3 conductor power cable, unlike the old PRT which took a 4 conductor. I think this is why the PRS has more grounding problems. Also, the PRT power cable was wired at the shop. We have to wire the PRS power cable ourselves.

[richards]

Keith,
Let's consider power going to the Shopbot controller for just a minute. In the United States, if we are only using 120VAC power, only one conductor needs to be switched - the HOT line. The NEUTRAL line can be hard-wired (always connected) or can be switched in unison with the HOT line. The GROUND line MUST always be connected.

If we use 240VAC power, then both HOT lines need to be switched (in unison). The NEUTRAL line can be hard-wired or switched in unison with the HOT lines and the GROUND line MUST always be connected.

If we use 3-phase power, then all three HOT lines need to be switched (in unison). There is normally no NEUTRAL line and the GROUND line MUST always be connected.

So, for 120VAC operation, a three-wire configuration meets all requirements. For 240VAC operation, a four-wire configuration meets all requirements. For three-phase operation, a four-wire configuration meets all requirements.

As a side note, if the NEUTRAL line is switched, it must be switched in unison with all HOT lines. It cannot be switched independently of the HOT lines. (I'll admit that there is a lot of debate on whether a NEUTRAL line is even allowed to be switched. I'm neutral (sorry, but I couldn't resist) on that issue. I hard-wire all NEUTRAL lines and only switch HOT lines.)

If the GROUND line is properly wired, the machine is grounded and any stray voltage will be shunted to ground. If the GROUND line is allowed to float, then anything can happen. If the NEUTRAL line is switched independently of the HOT line(s), then someone is going to die (sooner or later) because electricity will be allowed to pass through a human being on its way to ground (or for the electrical puriests - from it's way from GROUND to HOT).

If a disconnect switch is used, it must disconnect all HOT lines entering the controller. If contactors are used, the primary contactor must disable all HOT lines entering the controller. If both 120VAC and 240VAC power are used, and if both 120VAC and 240VAC are being supplied from the same sub-panel, then all three HOT lines must be switched. If either 120VAC OR 240VAC AND 3-phase power is being supplied to the controller, then you'd better consult an electrician (unless you're very foolish) - life is too short to waste on wiring errors.

[Gary Campbell]

Keith..
Even though the SB manual is lacking in some areas, as far as the electricl hookups go, the few items that were not covered, were shown on the schematics. If one is able to read the schematic, then the hookup is fairly straightforward, if not, then refer back to the manual where it says to call a qualified electrician.
From my seat on the bench, there seems to be a rash of lost position, stop hits, and other faults that are not repeatable. These are not very likely to be line voltage or control box grounding issues. Having gone thru most of them myself in the last 6 months, and having most of them solved, by SB tech. supt., rereading the manual, and some common sense, I have a machine that is reliable 95% of the time. I think the input sensitivity/prox switches/ground loop issue that has surfaced in the PRSa tools needs some documentation on the SB Home page, Dr. ShopBot or the Wiki. I also think there is a tie in to the 3.5.* software too. Even after extensive grounding, including the usb/rs*** adapter, output relays etc inside the control box, we will still have a stop hit or 2, usually first time the machine is moved, almost always when doing the days first Zzero, and most of the time doing a JH from the 90,30 position where it was parked and cooled down the day before.
These "events" are much easier to deal with now with a few hundred "Bot" hours under my belt than they were in the beginning, as one does not know if the problem was operator error or machine problem. Of course 1 or 2 a day is easier to deal with than 10 an hour also.
Gary