stops cutting randomly

[acourtjester]

does your Plasma torch cable run with your motor and switch wires????

[kbenz]

nope

[Mtw fdu]

I am having the same thing happen to me and taking note to some of the reasons and solutions to the problem.

To explain a bit of my setup first...I have a Camcutcnc machine which has been designed in the past to use Windows XP but I am using Windows 7 with a USB and THC (proma brand). Hypertherm 45 with machine torch, UC 100 motion controller, Bobcad software and Mach 3 software. I am also using a laptop computer.

The pic below shows some letters I am trying to cut (3mm stainless) and this is the only time it happens. When I cut 6mm mild steel it runs perfectly. I was trying to cut the letters DIV-7. However, when I cut the previous pattern (the circle on the plate) it cut that really good but I need to do more work on the pattern itself (checkout 2nd pic below).

At the moment my power supply to my shed needs to be up-graded to a heavier cable supply to be able to take on my plasma machine. Here down under I am using a 15 amp power socket with a 16 amp circuit breaker. My plasma gets hot and trips the overload to my shed power box and then I need to flick the switch back. When my power has been up-graded I will have a 15 amp power socket with a 20 amp circuit breaker. The overload light on the plasma comes on just before the air compressor cuts in and fills it up.

Is there reason that it only happens when I use stainless?

Thanks in advance.

Mtw fdu.

[steel 35]

does your Plasma torch cable run with your motor and switch wires????

Jumping in here I am stringing the wiring on a new system and have all the wiring and machine torch cable run through the loom on the x/y axis but separated by the center divide is this a bad thing? I was planning to put Computer, bladerunner and Hypotherm 65 under 36" wide table today, Wanted that brand new never plugged in Plasma covered, would this be strike two?

[acourtjester]

I have always had the plasma cable separate from the other wiring I use a overhead boom. one reason is I also attach a router and a scribe to my table and I can run the electric for the router and the air for the scribe the same way it make is easy to swap. Plus I don't have the big fat plasma cable in the cable chain this keeps it more flexible.

[tcaudle]

I am having the same thing happen to me and taking note to some of the reasons and solutions to the problem.

To explain a bit of my setup first...I have a Camcutcnc machine which has been designed in the past to use Windows XP but I am using Windows 7 with a USB and THC (proma brand). Hypertherm 45 with machine torch, UC 100 motion controller, Bobcad software and Mach 3 software. I am also using a laptop computer.

One of the reasons we discourage use of USB motion control is because it does not have the noise immunity of Ethernet . Additionally USB is a polled protocol, meaning devices on the USB Bus have to wait until the Master (PC) asks each device if it has traffic (you can raise your hand but the teacher has to ask each student if they have something to say and ignores your hand up) and sets up a communication pipe that is one way. its just the nature of the beast. Works really good for one way traffic and things that communicate in short bursts like keyboards, mice and even memory sticks. Plasma being a much more noise filled process can cause problems with systems that are susceptible to it .

Stainless and aluminum both behave differently with noise. Mild steel is a better conductor of low frequency waves whereas aluminum will let it pass with little attenuation. Technically the higher the iron content the better it conducts magnetic waves of low frequency. (or takes them to ground if there is a viable path) Simply put the SS is a better transmitter antenna than the mild steel.
The more important thing is to understand the workclamp from the plasma is NOT ground. It is actually at positive potential volts. It is only ground if you clip it to a grounded conductive object
You should have a ground rod tied to your table frame
You should always clip the Workclamo DIRECTLY to the material you are cutting. Get as good a current path as you can.
You should try and keep the plasma cutter and the torch leads as far away from the USB cable and PC as possible

[steel 35]

Noted and defiantly changed. Thank you both.

[Mtw fdu]

You should try and keep the plasma cutter and the torch leads as far away from the USB cable and PC as possible

@tcaudle

Thank you for that info...it makes sense. I have got a 2 x 2 table but I have got everything on the bottom of the table itself. I also have the table on casters so I can move it from 1 place to another conveniently. The plasma machine is in VERY close proximity of the laptop. I can understand where you are coming from. However, my table only has a single ground clamp to the work piece itself...there is no ground clamp connected to a rod to the ground.

Mtw fdu.

[tcaudle]

The clamp to the material (WORKCLAMP) IS NOT GROUND. On rollers your table is insulated . The workclamp on a plasma has all kinds of noise on it if it is not grounded to e real earth ground (plus it it dangerous)

If your PC chassis is in contact with the table metal then you have a direct condution point for noise and with the table ungrounded it has no place to go but over to the safety ground the chassis is tied to but through small wires.

[Mtw fdu]

@tcaudle

My laptop is on a foldable shelf on my plasma table. It is made of wood. Will this make any difference or should I just connect a wire from my table (from a bolt with a crimp connection) to another bolt which is already in the shed floor or should I just drill another hole in the floor and put a threaded rod which has been chem-set in and connect it to that with another crimp connection?

If so what size wire should I use?

Mtw fdu.

UPDATE...Just read a disk I received from my cnc guy about grounding my machine. I will follow those directions and see how it goes. We are in the middle of a heat wave of temperatures in the mid 40 degrees C with also extreme bush fire season. Will not attempt this or "any" cutting until the temperature drops to a reasonable level.

[Mtw fdu]

UPDATE...Had my electrician come and install an earth cable to my table. The earth cable is connected to the table through a bolt and the earth cable runs up the plasma cable and connects to the shed by my power supply. Did a run with some stainless and every cut worked well, there were no failed pierces at all. Thanks for the help guys.

Here are the pics.

Mtw fdu.

[Jhart]

KBENZ,

FWIW, I bought a couple of Dell GX620 computers off of Ebay ($60 ea.) and did a fresh download of Mach and CandCNC software. Haven't had a problem with the torch shutting off since. For the money, it may be worth a try.

[kbenz]

KBENZ,

FWIW, I bought a couple of Dell GX620 computers off of Ebay ($60 ea.) and did a fresh download of Mach and CandCNC software. Haven't had a problem with the torch shutting off since. For the money, it may be worth a try.

I got one(gx620) from a local guy here for bout that price. haven't had any issues since either

[Jhart]

Excellent! Nothing worse than chasing problems.