Hi all I need help ,I’ve just finished build a Cnc plasma table and using sheetcam and mach3 ,everything is goin fine except when I try firing the plasma torch via a relay, it causes a “emergency mode active” and status as “ external estop” and everything stops working,I’m using shielded cables on all 3 motors. My plasma cutter is a Promax cut 40, I have a threaded rod hammered 800mm into the ground at 1 corner of the table for my ground witch is connected,what could be the cause of this?
Feedback will be highly appreciate.
Thanx.
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Mactec54
Only my motors have shielded cable ... and my relay cables from my driver box to my plasma machine are not shielded cables .. everything else is securely grounded, will this problem go away if I use shielded cable for my relay?
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Mactec54
The driver box is grounded from the table witch is grounded to the threaded rod and all motors are grounded from the screws to the driver box
I will look into the debounce setting mach3 and see if it makes any difference
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I have been running my CNC plasma table for over 10 years now..I had these problems when I first got it going..XP computer..CNC4PC G-11 BOB..Gecko drives..
What was happening is the ground was back feeding to the computer through it's ground..Isolation of the computer is important..The BOB isolates the computer from the all the heavy arc voltages..Except for one..The ground!!
The power cord to the computer..I removed the ground male prong..That completed the total Isolation of the computer..All problems went away..I replaced the power cord with a 3 prong plug and the problems came back..went back to the 2 prong..It has never had a problem since..
I am not even using shielded anything..My cables to my motors are 4 wire 16 gauge that I found at Home depot..It has a nice plastic covering on them..The table has a ground to it..My control box is a wooden cabinet that has the computer setting on the top and a sliding shelf with all the BOB and drives and power supply for the motors..No physical contact of the computer to the machine..
I am a newbie to this so I’m not exactly sure what you mean by ground loop? To my understanding I must ground all electrical components as best as I can .... what would u have done in this case?
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You can only have ( 1 ) source for Ground, the input Main Power supply has a Ground and all Grounds have to connect at this one point, this is called a Star Point Ground, you have 2 Grounding points which you don't want to have this is forming a Ground Loop so you can't do this and expect things to work correct, your other wiring is also problematic as well, but start with fixing up all the Grounds
Mactec54
Ok I will ground all my components to the steel rod at the table.
Thank you for your input
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Please excuse my directness but it seems you don't understand the life saving purpose of that ground prong you cut off.
Normally current runs from the active/live wire, through the appliance, and returns on the neutral wire. Under normal conditions, the earth wire has no current flowing in it.
However, if you have an appliance with an external conductive surface (like metal), and a circuit develops from the active/live wire to that conductive surface, the current should flow in the ground wire (which is connected to the metal case). Because the ground wire SHOULD be at ground potential, then the theory is that anyone touching the exterior surface will not get electrocuted if they touch the external case. Often, enough current flows from active/live to ground, to blow the fuse or trip the circuit breaker, or even trip an earth leakage circuit breaker if used.
If you remove the ground prong, you've just allowed any conductive exterior case to become LIVE if a fault circuit develops to it from the live/active wire. Then when a person touches that case, the electric circuit is completed from the case, through the persons body to ground (i.e. where they are standing), and they get electrocuted. They may get very lucky if they are standing on a highly insulating surface, but it does not take that many milliamps to stop a heart beating.
Just thought I'd better warn people about this. My advice - leave that ground prong as it is.
You'll often find appliances with only the active and neutral prongs, and no earth prong. They are often termed "double insulated" and have no exterior surface that conducts electricity, and thus cannot prevent a live exterior surface to the user.
Are you saying I’ll have to take the grounds of all the electrical either to the ground of the wall plug socket or to the grounded rod that I hammered into the floor?
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They all have to go to the one main Ground source the Electrical Ground Bus in the electrical Panel, so yes your Grounds can only go through what ever you are plugged into, not the hammered in rod in the floor this is a bad idea, if you don't understand consult with a qualified electrician
Mactec54
Ok thanx I’ll try that
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This is really pretty simple: The e-stop input into MACH is getting a noise spike when the torch fires. All it takes is one short glitch to trip it. If the inputs on your BoB were isolated with an isolated power source it would not do that. Also if your your Estop input was active low (norammaly closed) and the input polarity were reversed it would only trigger when the input goes OPEN which is more noise immune that it just hanging out in the air. Of course if you are using any other inputs you will have false triggering on them as well. You need to shield against INCOMING noise on logic level circuits (that trigger on small voltages and low currents. Shielding motor wires will have little or no effect on your problem. If it were motor noise it would do it as soon as you powered up the motors. So seek out an opto isolated BoB . If you don't have any external Estop switches take the estop input to its common (ow) and set the input so that is the OFF condition (un-triggered) . Most noise is CONDUCTED meaning it travels across a conductor (wire/connection) Some HF start plasmas give out a burst of RADIATED (thought the air (RFI) but most of it is still conducted. Optos couple with light and break the conduction path. Having too much grounding can be as bad as not enough. A ground loop is where the noise or current has more than one path to travel so it loops around . The answer is not always to ground everything to one spot (star ground) because the ground return on all of the circuits may not be accessible. A 2 ft ground wire does not have the same impedence at higher frequencies as does a 20ft run or one that loops though a few sub circuits first.
there is grounding for safety and then there is grounding for EMI/RFI (noise) . They are not the same. Sometimes its better to block the return path (common connections) than to try and shunt everything to one ground. .
Well there was nothing else I could do to get it going..The machine would jog over..do the touch off dance and then fire the torch..This is a hypertherm 1250..A good machine..But then it was frozen at the fire of the torch..The computer would lock up..It was getting some sort of jolt through the ground wire..
I even got an 100 foot extension cord from house power and plug in the computer with it..Same thing..Fire the torch..frozen computer..A dell XP computer..
I removed that prong..10 years later I am still here..Everything else is grounded..the table, torch everything but the computer..The BOB is a Opti isolated board..
Some of you might think that I am idiot for this part also..But I don't run safety switches..those switches that stop movement at the far end of the machine when they are activated..I am just very careful when I jog my machine..I don't run it into the ends..
So is it working correctly now?
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There are hundreds of plasma machines that run in the home shops and in businesses, if the wiring is done correctly no such thing needs to be done to any computer plug a simple power filter most likely would of taken care of your computer problem
So is it a problem what you did only for the computer if the power supply decided to go bad ( which they do ) and you touched the case is when it would be a problem for anyone around who just happened to touch the computer case at the wrong time
Mactec54
Yes it is..it has been working for nearly 10 years this way..
The power cord that feeds everything that my computer is hooked up to..I have a separate computer type of power supply that runs fans, the BOB need 2 separate power supplies because it is opti issolated..
Everything that the computer needs for power and accessories is supplied with this un grounded cord..
Everything else has it's ground..Plasma cutter, table..all are grounded with a grounding rod driven into the ground..
I am just telling you what was happening to me..And I verified that it was the ground coming back to the computer that was freezing the computer..I took the ground off..it worked great..I put it back on ..freezed up again..
I tried that 3-4 times ground off..ground on...worked..didn't work..
If you are concerned about being killed by a computer power supply going bad and you touching the case of the computer..Then throw my advise away and keep digging for a solution..
I found the problem for me..it fixed it and that is it..