New Plasma build question

More
21 Jun 2019 08:13 #137463 by Clive S
Replied by Clive S on topic New Plasma build question

Scratch start will be a challenge, but I think firing the torch before probing could just make it work, but only with floating head and switch. This will also have the inheritable problem of short circuiting the output of the plasma cutter while probing and while that is required to make it start, doing that very often and for prolonged time might end up in burning the plasma if it does not have provisions for limiting the output current, that can be checked easily by opening the plasma and looking for a choke


Thanks for the info Tommy, Could you elaborate a little more on the above. Are you saying scratch start will be a problem with the part under water. I just have a very old cut40 type machine pic here: forum.linuxcnc.org/38-general-linuxcnc-q...727-about-thc#135714 I am getting conflicting views on which THC 10 or 300 does the pic help to identify this.

Thank for all your input in the past.

Please Log in or Create an account to join the conversation.

More
21 Jun 2019 09:15 #137471 by rodw
Replied by rodw on topic New Plasma build question
Clive, I think you will be fine. I think you will find when you get our torch that it is a HF pilot arc start and will fire in the air.

Please Log in or Create an account to join the conversation.

More
21 Jun 2019 09:32 #137474 by Clive S
Replied by Clive S on topic New Plasma build question

rodw wrote: Clive, I think you will be fine. I think you will find when you get our torch that it is a HF pilot arc start and will fire in the air.


Rod I got one of these to test the cut40 www.ebay.co.uk/itm/PT31-New-Red-LG-40-Ai...0afa9&frcectupt=true

It does not seem to fire in the air, only scratch start. The good news is the cut40 works so not bad for a freebe.

Please Log in or Create an account to join the conversation.

More
21 Jun 2019 09:44 #137477 by rodw
Replied by rodw on topic New Plasma build question
You don't have the right torch. The torch for the one I destroyed had a second wire that connected to the extra connector on the front of the machine. from memory it was a Cebora. Probably like this (which you can see has some extra wires)
www.ebay.com.au/i/221839481593?chn=ps&no...paqtjFUaAlcMEALw_wcB
The following user(s) said Thank You: Clive S

Please Log in or Create an account to join the conversation.

More
21 Jun 2019 10:14 #137479 by Clive S
Replied by Clive S on topic New Plasma build question

rodw wrote: You don't have the right torch. The torch for the one I destroyed had a second wire that connected to the extra connector on the front of the machine. from memory it was a Cebora. Probably like this (which you can see has some extra wires)
www.ebay.com.au/i/221839481593?chn=ps&no...paqtjFUaAlcMEALw_wcB


The torch I got was exactly the same as the original, it just had two wires going the the switch on the handle . On the machine there is only a two pin socket on the front.

Please Log in or Create an account to join the conversation.

More
22 Jun 2019 00:34 #137530 by tommylight

Clive s wrote:
The torch I got was exactly the same as the original, it just had two wires going the the switch on the handle . On the machine there is only a two pin socket on the front.


Yeah that should be a scratch start, two thin wires for the switch and the main air tube/wire for the torch.
Pilot start must have another thicker wire, usually red colored in 99% of them, some have 2 red wires as per Trafimet spec. That wire is always wired to the torch shield.
As for underwater scratch start I have never tested that, but I do think it will work, but not reliably.
Child the machine have a working Z axis even without a THC, then you can do some tests and check what works and what not, then we can do some HAL-FU to make it start more reliably.
I do not have a scratch start so I can not test, hell I need to build a floating head and something that moves, I have nothing ready except the THCAD mounted to the plasma, and plenty of Mesa cards waiting to be put to good use.
The following user(s) said Thank You: Clive S

Please Log in or Create an account to join the conversation.

More
22 Jun 2019 08:07 #137566 by Clive S
Replied by Clive S on topic New Plasma build question
So THC 10 or 300 ? What is the main difference?

Please Log in or Create an account to join the conversation.

More
22 Jun 2019 08:34 #137570 by rodw
Replied by rodw on topic New Plasma build question

Clive s wrote: So THC 10 or 300 ? What is the main difference?


About 45 cents worth of resistors.

Please Log in or Create an account to join the conversation.

More
22 Jun 2019 14:04 #137588 by AgentWD40
Replied by AgentWD40 on topic New Plasma build question

Clive s wrote: So THC 10 or 300 ? What is the main difference?

The 10 reads input voltages from 0 to 10 volts. The 300 reads from 0 to 300.

To get the best resolution on your voltage reading you want to use as much of that range as possible.

When you're using the 300 you're probably messing with much higher and dangerous voltages.

If your using the 300 it's recommended to mount it in your plasma machine itself if there is room or put it in its own enclosure and mount it on the machine. If you use the 10 you can just put it in your enclosure with the rest of your electronics.

That's the way I understand it at least ;)
The following user(s) said Thank You: Clive S

Please Log in or Create an account to join the conversation.

More
22 Jun 2019 15:19 #137592 by Clive S
Replied by Clive S on topic New Plasma build question
I agree completely with the below. But I this point I am not sure where to get the voltage from in the machine ie is it straight from the torch output terminals on the machine ie +ve and -ve and route those to a metal box with the THC in it and fitted to the case of the plasma machine.

Or do I take the cables via two resistors one in each leg to minimise the current to a few mA something like 15k-20K

Please Log in or Create an account to join the conversation.

Time to create page: 0.128 seconds
Powered by Kunena Forum