Torch diving problem

[Complete_Loser]

Howdy ya'll.

This weekend has been a fiasco! Got a big business wanting a small sign (and if they like it, will want more). They need it asap ofcourse. So ive drawn the file up, and its all ready to cut. I take it out to the shop, and the shop computer took a shit. More specifically, the only program that wont run on it, (wont even open) is Plasmacam (the only program I NEED!)

So I then set out to build a computer quickly to get this sign cut out. Spent all night last night, and called in several favors and got one hell of a digital frankenstein goin. Installed Plasmacam, and since all our old settings are lost (since the laptop if fubar) we are having to setup plasmacam from scratch.

I would say we are 90% there. The latest problem I cant get past is the torch diving into the metal and dragging. The setup is DHC2, The newest Plasmacam software update, and an ohmic sensor ring on the torch head. This is the same setup we've been using for a year with no problems. So I know this problem is just a setting, or arc voltage value or something. ?

When its cutting on a fresh area of metal (no other cuts), it seems to do fine. Hovers nicely. But when it gets into an area where there is alot of other cuts around (highly detailed area) it wants to push into the metal. No matter if i raise or lower the ohmic sensor (in relation to the nozzle), raise or lower the cut height or even clean the metal, 1 of 2 things happens. Either it still dives into the metal, or it hovers an inch or 2 above the metal, essentially cutting nothing.

Anyone have any thoughts?

[Pricer52]

Can you override the height control and operate the torch manually to get you through it? I am not familiar with Plasma CAM at all. I know on my table I can override the ohmic control and hover the torch manually.

[Complete_Loser]

Thanks. A sign that would have normally taken 30min took about 2hrs. I got through it. Everytime it started to dive, or go up and cut nothing but air, I would go into settings and click 'auto calibrate Zshifts on next cut". That would get me through a few more cuts. Then I would just click it again.

[Complete_Loser]

This sounds as though your machine may be decelerating too much for the sharp direction changes in the detailed areas. This deceleration will cause the torch travel slower in these areas so more material is removed and the arcs grows in length as it reachs for groud (material to cut). Your height control will recognize this change in arc length and lower the torch thinking it needs to go down causing it to drag the torch on the plate. I am not sure what the setting to change is called in PlasmaCam but it sounds like this may be your problem.

Thanks. I will look into that and give it a try.

[BrianMick]

on plasmacam, go to settings, height controll and in upper right corner un check torch height control....
you can do this on the fly if you wish by pausing the machine while its cutting and going into setting and doing this
this will allow you to keep switching back and forth between height controll....
Brian

[Complete_Loser]

under "Machine Control" there is "Corner acceleration (G)" ____
And under that is "Slower on circles under (inch)" ____

If thats it, I dont recall my previous values for those areas. So I will just have to stab at it i reckon.

[elkriverfab]

Complete_loser,

I feel your pain.......
Had the same thing happen to me a couple of weeks ago right in the middle of a job .

Had to put another computer on the table and of course, the settings I had been using for the last few years were now gone!
I now see that writing all settings down in a note book would have saved me a lot of time.

I now do this.

I also always back up all my drawings and designs to disc every day (if new).

It was like setting up a new table....hell, I forgot how until I had to do it again.


The rule here, save... save... save everything on paper and disc.
It will be used again.

My computer is in the shop and it gets abused even when I try to keep it clean and dry.
But, it does suck in the environment, can't avoid it.

To all of you people new to this business listen good, back everything up and save your favorite settings.
It will save your butt not if but when it crashes.

It will crash. I am on my third computer now.
I bought several used computers from craigslist and pawn shops and wiped all programs from them and they are waiting for there turn to cut metal.

Dust has not been my problem, it's everything else. Last time I opened the computer to clean it I found a large amount of black widows, mice and everything else.

As a mater of fact, yesterday I was welding and smelled something cooking in my mig welder.
Yep, a mouse was frying on the terminals as I was welding.

Cooked mice and rats don't smell so good

I now have five cats in my shop to help get rid of the critters but a few still find there way in at times.
Unfortunately the cats don't want anything to do with the rattle snakes.

[Complete_Loser]

lol. I agree.
And yup, it wasnt dust that killed this computer. The only program on the computer that wouldnt open was Plasmacam. It would not open, kept saying it was already opened. Once I reinstalled pcam, i could then open it, but it would not communicate with the robot. Would say (port not recognized) or something like that. Bottom line, it fried the port or something upstream of it. ?

You know that someone up there is having a good laugh when the ONLY program I need to get a job done.... IS TOAST!

[geo4932]

You did not mention which release of the Plasmacam software you have and which version of Windows.
Anyway, the problem you had was not in the Plasmacam software but in the computer BIOS. Without knowing what brand of computer you have, it would be difficult to help you. Normally the parallel port mode will be EPP or Bi-directional and the I/O address is 278.

[apcnc]

Your problem sounds like THD Torch Height Disable parameter. Sounds like your torch is diving when it comes to a corner or slows in the corner. I dont know or use plasma cam but you should be looking for something like THD or Corner signal. You may find a distance to and from corner to lock out the THC until the machine reaches programmed speed. If the THC is very responsive it will dive until reaching programmed arc voltage when slowing down any amount. The control will need to correct this in some way. Usually by the disabling the lifter.

[Complete_Loser]

You did not mention which release of the Plasmacam software you have and which version of Windows.
Anyway, the problem you had was not in the Plasmacam software but in the computer BIOS. Without knowing what brand of computer you have, it would be difficult to help you. Normally the parallel port mode will be EPP or Bi-directional and the I/O address is 278.

We tried all that. Epp, ps/2, 278, 378, etc etc. The thing is, the laptop worked fine, then one day, plasmacam didnt work at all. I dont recall the error but was somthing like "Port2 Not Detected". Having changed nothing previously, thats bad news.

We went into bios and still no change. Same error code. Port is fried.

Thanks apcnc. I will look into that. I havent even fired the torch back up yet. Im building the new computer right now. I figure while im down, might as well do it right. Got a new case and 8in filtered fan to put in side of the case. 110cfm should pressurize that tower to keep dust out.

[apcnc]

You did not mention which release of the Plasmacam software you have and which version of Windows.
Anyway, the problem you had was not in the Plasmacam software but in the computer BIOS. Without knowing what brand of computer you have, it would be difficult to help you. Normally the parallel port mode will be EPP or Bi-directional and the I/O address is 278.

Just noticed that you were a mfg rep. So what parameter is used for THD in Plasma Cam? Or how does plasma cam compensate for accel/decel?

Also on LPT, If the port is blown on both PCs I think there will be bigger problems than dust. Check for damaged cables. Does the machine use shielded cables? How is the ground? Do you have welders close by? Any plasma cam machines use plasma with High Frequency ignition?

[MQUICK]

I just went through the same problem on the parallel port on my computer. Even replacing the parallel card did not help. I bought a used xp computer for $50 and was up and running in no time. Yep, it's like setting up a new table. The odd thing is my height control has not worked this good since I installed the machine.

The computer shop told me about problems on the mother board. They find that a capacitor printed on the mother fails from age, feed back, or being cheep.

[Complete_Loser]

Finally got a chance to go out and try the machine again.
Even though this is the Plasmacam DHC2 (with software v3.11), I went ahead and used Georges directions on setting Zshift and Arc voltage. Still, the torch head dragged the metal.
So, I went back to the method that always worked before. In the past, I would set my ohmic ring 1/16th of an inch or so below the torch tip. Then cut height at .02, and pierce at .02 (this varied depending on material and thickness). I would check "Calibrate Zaxis on next cut". And the machine would cut wonderfully. The only time it would climb would be if dross would get stuck to ohmic ring. Very rarely would it dive and drag into the metal.

So I set up these same parameters tonight, and used the 'Calibrate Zaxis on next cut' setting. Still the same thing. It would eventually dive and drag on the very first cut after an inch or two. I would stop it, and recalibrate Z, and the next 2 cuts would be correct height (visually), then it would start to diving and dragging again. At one point, it started to climb nearly an inch. The tip was already trash, so i let it go ahead. And it appeared to maintain a specific height of about 1in above the metal.

Really, im starting to suspect we have an encoder going bad, or we are doing something wrong. When I would use my router to do wood, it was always hell to get a consistent cut height. If my cut height was .42, and I initialized, that same location would then be .78 or something way different. If I had 1inch of material on the table, and I zeroed it, my cut values for Z would be in the negative range (ofcoure not letting me cut in the negative range). So I would have to lie to the machine and tell it there was 1/4inch of material on the bed.

[geo4932]

OK, now I see what your problem is. You have the cutting height set at .02" and you made a homemade ohmic sensing tab that is .06 below your cutting tip. Do the math, that is not going to work. The ohmic tab is .04 LOWER than your cutting height so it is going to drag when the torch is at .02.
You really should get the Thermal Dynamics factory ohmic consumables or in the mean time set the cutting height to .100

george

[geo4932]

You did not mention which release of the Plasmacam software you have and which version of Windows.
Anyway, the problem you had was not in the Plasmacam software but in the computer BIOS. Without knowing what brand of computer you have, it would be difficult to help you. Normally the parallel port mode will be EPP or Bi-directional and the I/O address is 278.

Just noticed that you were a mfg rep. So what parameter is used for THD in Plasma Cam? Or how does plasma cam compensate for accel/decel?"

apcnc,
The Plasmacam height control uses ohmic feedback to set the pierce height. After it pierces it uses arc voltage feedback to monitor the cutting height. The dhc settings have a compensation to match the cut height to the torch, since arc voltage is different with different amperage nozzles. The software also has settings for corner deceleration and hole deceleration obviously to automatically slow the cut speed to reduce the effects of arc lag.
You do not have to know any gcode to run the machine.

george

[apcnc]

Sorry, I was asking what setup paramter does the system use for THD everytime the machine enters a corner. Not a disable from the code. Or is it setable?