Author Topic: Physical buttons for plasma  (Read 83044 times)

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Offline beefy

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Re: Physical buttons for plasma
« Reply #80 on: January 26, 2016, 06:41:51 AM »
So Rob,

what did you ask HT and what response did they give.

I'm curious about the reaction time of their current control. I wonder if they publish figures like that. So from gcode to HT current adjustment via their ASCII modbus interface there will be some delay. Some of that is under our control but once the HT receives the ASCII value I wonder how long it takes for the cut current to adjust.

Keith.

Offline BR549

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Re: Physical buttons for plasma
« Reply #81 on: January 26, 2016, 08:20:02 AM »
iF you are talking about on the fly amp reduction I am not a big fan with low end air plasma as you do not gain anything from it without having all teh high end features of plasma. It is more of a sales gimic than anything at this level.

You will gain a LOT more by working on the mechanics of your machine rather than the gimics of your machine.

NOW HIgh end mixed gas variable flow machines are a different story BUT that is NOT what we are dealing with.

NOW why Modbus Ascii ?? I do not have a clue only a guess.  Ascii uses a CRC check of teh code to insue it is what it is. I GUESS they wanted that type of secure mode to talk to a high end machine and it just trickled down in technology. IT DOES make it a PAIN to work with for low end stuf.

Why make it even more complicated just program your COntroller to talk Ascii.  HT shows you how to use teh CRC check.

WHY would you want more than 1 com board for teh plasma ??? 


(;-) TP
« Last Edit: January 26, 2016, 08:24:08 AM by BR549 »

Offline stirling

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Re: Physical buttons for plasma
« Reply #82 on: January 26, 2016, 08:26:48 AM »
NOW why Modbus Ascii ?? I do not have a clue only a guess.  Ascii uses a CRC check of teh code to insue it is what it is. I GUESS they wanted that type of secure mode to talk to a high end machine and it just trickled down in technology. IT DOES make it a PAIN to work with for low end stuf.

Hi Terry - we've discussed this before - I guess you've forgotten - check our email conversations.

Modbus ASCII actually uses an LRC whereas Modbus RTU uses a CRC. Moreover the LRC is only 8 bit whereas the CRC is 16 bit. The end result is that as far as error detection is concerned RTU is the WAY more robust than ASCII.

Offline robertspark

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Re: Physical buttons for plasma
« Reply #83 on: January 26, 2016, 10:36:16 AM »
Gents,

To be fair, I whole heartedly understand their position... but it would have been nice to get a bit more info.

Judge for yourselves

Question:
Quote
Hello, Looking for some technical advice or guidance, regarding Hypertherm Part number 228539 (PMX 65 / 85 RS485 communication interface). I was wondering if there was any way to change the modbus communication protocol from ASCII to RTU, or if you were developing or able to provide a MODBUS RTU protocol board? The reason being is RTU is way more common than MODBUS ASCII, hence I have cnc software which is able to directly commuicate via MODBUS RTU and I would like to employ that than using a communication interface bridge. The 228539 board obviously interfaces with J7 on the PMX65/85, is there any way I can find out what protocol or what interface takes place between the 228539 and the DSP board (141073), so I may be able to build an interface directly which could be MODBUS RTU or even MODBUS TCP/IP to gain access to the registers? Happy to sign an NDA

Response:
Quote
We only offer serial communication protocol as per the attachment, we would also not provide any other internal information on board to board protocol.

For those interested (sorry Hood, not trying to side track your topic... keep meaning to have a look at your photos on a big screen [pc])

The interface infomation is here:
http://www.cnc.info.pl/files/serial_communication_protocol_807220rev1_124.pdf


Terry, yup it's probably a "gimic" but I thought it may be handy to have if there was very little to do to incorperate it into your system.

I know that CandCNC do an interface, and compliant sheetcam postprocessor etc for this and its well documented on youtube https://www.youtube.com/watch?v=QKipXFIIg0k plus their website.

I'm over the pond, and was more curious than wanting to reinvent the wheel and I just didnt want to go to CandCNC thanks because of cost (shipping import duty etc etc etc.)

Key word.... Curiosity....

not having a go at any manufacturer
Rob

Albert Einstein ― “If you can't explain it to a six year old, you don't understand it yourself.”

Offline Hood

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Re: Physical buttons for plasma
« Reply #84 on: January 26, 2016, 02:04:51 PM »
Rob, no problem, nothing in my book is a hijack if it is talking about the subject even if it goes way off at a tangent.

I emailed TecArc yesterday and got a reply back, not really the info I was seeking but I suppose I never really asked a direct enough question.
Basically they said they do it as an option and they could supply parts to convert but said it would need to be done by a qualified Electrical Engineer. I asked what the parts would be and how to do but they came back saying they could supply a kind of add on which would be easier to do. What they would supply is a current sensing board  and a voltage divider board. I already have them (got with the THC) so do not see the point in purchasing more just to wire up in exactly the same manner.

I still think the divider , Arc Ok and trigger terminals are there and it would just require hooking them up but I am not going to bother trying to trace them, will just shove in the boards I have.

The THC I got has modbus on it but when I asked the guy said it really wasn't that great (too slow)  and on future revisions he will be removing it.

Hood

Offline robertspark

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Re: Physical buttons for plasma
« Reply #85 on: January 26, 2016, 02:14:46 PM »
Well the torch on and off will be easy to find.... Trace the hand torch leads obviously.

Normally the voltage sense just goes across the ground clamp (which is positive dc polarity) and the torch (negative polarity with respect to the clamp).

Only the HF off or torch cutting current signal initialised signal to find

That THC (nearly bought one) has something called "caxis protocol".... I'm curious.... What is it?.... Apparently it's a way to send settings back from the controller to Mach....or that is what I gleened from the manual

Rob

Albert Einstein ― “If you can't explain it to a six year old, you don't understand it yourself.”

Offline Hood

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Re: Physical buttons for plasma
« Reply #86 on: January 26, 2016, 02:15:30 PM »
Ah Ok just looked at the vid, the modbus connection you were talking about is totally different than I was thinking, it is for controlling the actual plasma current etc.
Hood

Offline Hood

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Re: Physical buttons for plasma
« Reply #87 on: January 26, 2016, 02:22:12 PM »
Yep, the connections I have to make are simple and easily accessible. The Arc signal board you c get can be cable tied to the work clamp but I will install it inside the machine and tie it to the wire that comes from the cap to the work  clamp socket. Can also get the arc voltage no probs inside and the torch trigger wires have connections I can hook into as well.
Just thought it would have been nice not to install these boards if the circuit board in the plasma already had the divider etc in it. I think it does, or at least the trigger and likely the arc signal as there are a couple of relays there.
Anyway not going to bother getting the addons from TecArc as they are exactly what I have already from the THC kit.


The Modbus in the THC is just a way of getting the Up/Down. Arc Ok etc to/from Mach instead of going via the parallel port or  motion controllers I/O.

As said I asked about it as it would have been an easy hook up but the guy said it wasn't that fast and not really suitable for thin material, so I never investigated it further.
Hood

Offline BR549

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Re: Physical buttons for plasma
« Reply #88 on: January 26, 2016, 04:42:39 PM »
Hi Ian I agree with you (;-), the explaination I gave as a guess came about from a conversation I had with HT many years ago about their choice of Modbus.

Hiya Robert, Ok I see where you were heading GOOD idea.  Who you need to talk to is Jim Colt at HT USA. I will see what I can find out from him. I agree that an RTU version would be a BIG help or even a simple Serial version would be just fine as you are NOT accessing vary mANY variables inside of teh Plasma unit. Basically cut Amps and Air pressure.

A simple serial version may  save a LOT of overhead  over using Modbus  ?????? AND it may be that the unit actaully talks a form of serial  and they only use the Modbus board as a dependable noise free communication in a shop enviroment.

It may be that Mach3 could talk to teh unit directly across RS485.

(;-) TP


Offline beefy

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Re: Physical buttons for plasma
« Reply #89 on: January 26, 2016, 04:53:48 PM »
Terry,

I remember you posted some time ago about having an "automated potentiometer" on your plasma cutter and you had it reducing the current at corners, etc. You said about 95% of the time it made no difference to the cut. I've often had problem on outside corners on thicker steel, and also where a lead out crosses over a lead in. I get tabs left. When the lead out crosses the lead in the arc "jumps" over to the steel on the other side of the lead in, leaving an uncut tab. Outside right angle corners have had it too, but it's more weird because the arc "RE-PIERCES" around the corner, again leaving a tab.

I was wondering if slowing down at corners may help this and by reducing the current a little bit it won't blow the kerf out noticeably wider.

Rob,

thanks for that info. I've downloaded from that link plus downloaded the other two pdfs on the protocol.

Keith.