Messages

31

General Mach Discussion / Re: Plasma Application, Mach3 torch height control.

« on: March 28, 2010, 02:28:08 PM »

Scott,

I figure from what you say the ONLY way to get an anaolgue value into mach is via the modbus?? No chance of it via the pp or serial port at the moment?? Obviously if it could be done by either the pp or sp that would make it much easier.

I agree i call bs on 10hz not being fast enough for the z axis, the system was accused of hunting because it was too slow, i think if it hunts its not because its too slow, its because the idea of a simple threshold and no proportional response in terms of a control system is junk, its bound to hunt really. So if you can do us for a pid loop that would be first class.

Personally im very interested in what jp is doing and i do realise trying to do everything in mach has its own limitations but to me its the whole beauty of it so id be keen to keep the processing element in mach, especially if we could improve the quality of the control loop. Im sure a plc could do a better job but for the money i could buy a thc system out of the box, its probably what i should do but a combination of stubborness and interest keeps me at this.

I could sort you out with a screen set, it would probably be a simple mach screenset with an additional tab or two, before i got right down to it id need to spend some time thinking about exactly what i want it to do for me....


I will have a think about itand let you know what i come up with, this would be a great time for anybody else to give some input as to what they want.

Matt

32

General Mach Discussion / Re: Plasma Application, Mach3 torch height control.

« on: March 28, 2010, 11:21:03 AM »

I cant remember what the numbers are, the ones i found were from the candcnc screenset, to be honest i have been using my own numbers, we should set a standard if scott is going to write us a plugin.

I cant tell you what numbers i used, i got a new plasma with hf start a few days ago, needless to say it blew the **** out of the motherboard!!

Matt

33

General Mach Discussion / Re: Plasma Application, Mach3 torch height control.

« on: March 28, 2010, 03:02:12 AM »

The short answer is no....

i think there may be a serial out command that is supported by mach in vb, its either serial out or in because i remember looking at it to see if i could get the plasma volatge in that way but i couldnt get 2 way communication.

In some ways i doo like the idea of referencing the voltage fromt he start of the cut too, saves a lot of messing, you just leave it to do its thing, set the feedrate to what gives you best results and it does the rest, i think it would be very interesting to be able to see what that was doing until you learned to trust it, for instance if i make 5 pierces and start cutting do i get pretty well the same voltage preset each time?? how close is it to what is in the book?? etc etc...

keep up the good work jp

34

General Mach Discussion / Re: Plasma Application, Mach3 torch height control.

« on: March 27, 2010, 04:59:37 PM »

Jp,

Personally id like to be able to set the voltage from mach for each cut, you could communicate it to the pic either using an analogue output if you have a modbus device or by using binary over 5 or 6 inputs, just a thought, be sure to let us know how you get on

Matt

35

General Mach Discussion / Re: Plasma Application, Mach3 torch height control.

« on: March 27, 2010, 04:16:11 PM »

JP,
I like it, i like it alot....

You tie the bridge to power supply negative to make them common, i had wondered about it but never imagined you could do it without having problems like drawing loads of current or destroying the pic when you fire the plasma, youve just solved a wholeload of problems!!!

The killer partnow really is in the filtering of the voltage from the torch to take out any spikes or component destroying hf.

I presume you are planning on using the pic for ad conversion then feeding the frequency output to mach through the pp??

Id love to see how that works

Matt

36

General Mach Discussion / Re: Plasma Application, Mach3 torch height control.

« on: March 27, 2010, 08:21:07 AM »

Scott, Long time, no speak, too long!

Im interested in if you can come up with a way for mach to use a pid loop or some kind of proportional response to an analogue voltage input, maybe instead of just using a straight forward threshold for up or down you could adjust thc rate as well in order to make a proportional response, seems crazy that the torch is going to move up and down at the same rate if the voltage is a long way off as it would if it was nearly correct. Any thoughts??

The other thing im wondering is do you know of another way to get a straight forward analogue voltage into mach other than through the modbus?? People have criticised the system for being too slow because of the rate at which the modbus and or brains work, if maybe we could get the signal into mach using the pp or the serial port we could do better??

Just thinking as i type im wondering if we could come up with a screenset with all the required coding behind it to allow users to tailor their own solution, i made myself a normal mach screenset with an extra thc tab where i can see all thats going on, in addition perhaps we could have a thc setup tab where you specify where your input is coming from, you can adjust the proportional response to suit your system, you can set target voltage and use the look up table like others use, and then all the coding is behind it so that someone can simply download the plugin, instal it, provide an analogue or frequency input, tune the proportional response and they will have a working system, which is made for them and them only, they supply any hardware required to interface to their plasma etc maybe with some pointers as to how to do it and all thats needed is the plugin. Maybe an option for those who wish to use a plc to just use thc up and down and then use the screenset to give an on screen display of the arc voltage in mach.


What does anybody think??

Matt

37

General Mach Discussion / Re: Plasma Application, Mach3 torch height control.

« on: March 26, 2010, 03:42:01 PM »

We may not be agreeing but we are provoking interesting discussion!!

The reason i always test with respect to ground ground is because the meter measures potential difference, put it between you plasma + and - and you get 1?? volts, meausre one with respect to ground and you get approx 0v, the other gives - 1??. When you feed it into an ic unless it has a voltgae comparator and uses 2 wires for each analogue input, it will compare it to the -ve side of its supply voltage, which probably is on or near ground, so unless you want to float your whole power supply ground at the same as one side of the plasma thats what it will be compared to.

Sorry if i cant explain what i mean very effectively, i know what i mean i just cant get it out!

Matt

38

General Mach Discussion / Re: Plasma Application, Mach3 torch height control.

« on: March 26, 2010, 01:27:03 AM »

I agree with you 100%, i thought htat would work too, but it didnt for me.

My polarity is definately negative, when measure with true ground as a reference i get approximately 0v from one lead and - 1?? from the other, the bridge makesno difference to this, tried and tried, all it does is ensure that all the positive elements of both signals go one way and all the negatives go the other, if there is no positve element to either signal, ever, you cant get a positive reading.

I dont entirely understand it and im not saying you are wrong at all but all i know is for my system it made no difference to the polarity but is a good idea to protect against the wrong polarity.

Matt

39

General Mach Discussion / Re: Plasma Application, Mach3 torch height control.

« on: March 25, 2010, 01:34:07 AM »

Jp - i like it, the only thing im wondering about is the polarity of your plasma voltage, my cutter is negative polarity, if yours is you need to connect your voltage divider to vdd not vss, so the arc will pull the voltage down.

Steve- I replied to your post a while back but it doesnt seem to have got there, i will write it again when i have a moment.

40

General Mach Discussion / Re: Mach 3 and Burny 3

« on: March 07, 2010, 08:43:33 AM »

Thanks hood, you always get straight to the point and seem to know everything!

I presume if the box has input and output cards in it i can just control them from a breakout board using 0-5v signals?

Thanks again

Matt