Messages

51

General Mach Discussion / mach 3 plasma troubles

« on: January 29, 2010, 03:01:32 PM »

Hi,

Im currently upgrading my cnc plasma cutter to try to make it better. Ive added a G100 instead of the old breakout board, ive bought a new machine torch and upgraded to sheetcam TNG.

Ive got as far as trying to cut a part and have two problems, im using a touch off switch on the z axis and when the torch comes down and touches the switch and resets the z height to zero for some reason mach is adding or subtracting seemingly random numbers from both the x and y position at the same time, so the machine then thinks it is in the wrong place so cuts to the side of the shape and then cuts the shape. Any ideas? The G code is exactly the sae as i used to use in the old version, it has nothing in it about the x or y axis?

I am also finding my torch on off is unreliable, when i click the button on the screen in mach its perfect but when a program runs it will only work if i ahve recently cycled it on and off manually, if i havent the light comes on in mach but the relay doesnt close?

If it makes any difference i am running under vista and as i mentioned with a g100

Any help would be greatly appreciated

Matt

52

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

« on: January 29, 2010, 02:49:37 PM »

Gents,

I am now back with my machine which makes me very happy! Im interested in how you are all getting on with your projects versions etc, does anyone else have a working version of the dthc in mach? What about the version using the spindle speed input? I would als be interested in hearing more from the guys who were talking about signal filtering as i plan to try to make my version of the dthc work better.

Thanks

Matt

53

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

« on: September 27, 2009, 07:56:33 PM »

Jp,

i think if you cant see the dro changing its probably to do wit no having the thc enabled properly, personally i ecomend downloading the candcnc plugin, ensuring you have the thc on and a brain to make the keys emulate the signals.

I too enjoy peoples input on this, mkes for intesting reading

matt 

54

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

« on: August 17, 2009, 03:57:21 PM »

Thankyou for your kind words

I think the way you are talking about will work just fine, im not really sure if having more than one input is useful or not, i will be very interested to hear how you get on with that

matt

55

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

« on: May 02, 2009, 02:56:34 PM »

Dave,

im gettin tot he internet somewhere between once a week and once every 2 so thats why ive been quiet, im working with a custom harvester in CA so we are busy at the moment and will be for the next few weeks then ill get to it more often, we will hvae to pick it up again then since ive forgotten most of what we talked about, i wont be back to my machine until christmas!!!

matt

56

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

« on: April 12, 2009, 09:56:06 PM »

Hi Dave,

Sorry its been so long, since we last spoke ive moved to California for work, i think the reason you are getting that will be to do with having thc mode turned on and off, since you must have this on to allow the axis to be jogged up and down whilst g code is running, the ability to do that is unique to thc mode since it could potentially be very dangerous if you could just jog an axis whilst the code is running, i hadthe same when i was testimng at one time and i cant truthfull remember what i did to get it to work but its in that area, unfortunately i cant take a look either since im over 5000 miles from my machine which makes me sad!!

i should be able to get online more again now so let me know how far youve got

matt

57

General Mach Discussion / Re: Plasma cnc

« on: March 21, 2009, 01:22:59 AM »

thats exactly it, its usually set in the post processor under pierce limit, not all posts have them but the one i use (mp3000 thc pierce count) does

matt

58

General Mach Discussion / Re: Plasma cnc

« on: March 20, 2009, 03:33:43 PM »

Marshall,

im sure this is a sheetcam issue not a mach issue, the only thing i have encountered in mach is the M1 optional stop button which requires you to press cycle start after every cut, perhaps you should join the sheetcam yahoo group and ask les, he could talk you through the g code you are using and work out if it is a problem with sheetcam or mach.

matt

59

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

« on: March 19, 2009, 09:21:29 AM »

dave,

with respect to the signals, i have connected the analogue signal from the voltage divider to pins 44,45,46, so that i can get more readings to average the reading from, these are read into the brain using modbus addresses 124,125 and 126 i think, these will give values between 0 and 1035 depending on the voltage of the signal from the voltage divider, 3.3v being 1035 and 0v being 0.

as far as the height sensing goes yes you could use that system, i think some comercial systems use it and its known as ohmic initial height sensing, do a search for it, i know some people slag it off and say it doesnt work if you plate is even a little dirty, i have no experience so i cant comment, also consider if having a wire connected to the plate to sense with is a good idea when you let it have tens of amps and hundreds of volts when you are cutting, sure there is a way round that with a bit of thought.

matt

60

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

« on: March 19, 2009, 03:06:44 AM »

second question first,

yes it can, what cam program do you use? i have sheetcam, it has the probing for the material built into the post processor i use so at the start of each cut the z xis moves down until it trips a switch on the floating part of the z axis (the torch holder is in a slot so it can slide upward when it touches the metal and is pushed back down by a spring) then it moves back up a distance you specify in the post before it pierces then down to cut height after the peirce delay. It works absolutely perfect and i really wouldnt be without it, i make no changes to the setup for material thickness, if i have a slightly warped plate and nedd to pierce on top of a hump it doesnt matter. All you have to do for hardware is construct the floating torch holder with a switch on it and connect it to the z home input to mach and dial in your required offset in mach.

first question second,

ive just looked at the brains here and i get the same trouble, it reduces them so small you cant see what they are doing, i dont think its you i had someone else pm about it and they said they couldnt read them either so ill explain the functionality.

the first brain (dthc1 i think) reads the values from pins 44,45,46 (The analogue inputs which work) and has a no operation block to connect them to an oem dro which doesnt have a designation, so this reads a raw value from each pin and puts it into a dro number where the next brain can read it from. Easy, the reson the brain is so big is because it does it 8 times for each input, so 24 times in total, this is slow and boring to make, is there a copy and paste function? The idea of this is that you can average all of these values to get a better reading.

the next brain (dthc2 i think) has inputs which are all the oem dros written to in the previous brain, now we are gonna do something with the data. Each of these dros inputs is connected to a block which adds them together, beware you can only have 8 inputs to a operation block so you have to add the first eight together, then the secons, then the third and then add all three of them together to get a total, once you have a total put it through another operation block where it divided by 24 ( to average it) and then terminate with writing it to another unused oem dro.

the third brain (dthc i think) Has an input of the oem dro you wrote the average value to in the last brain which is then put through a formula block to turn it into arc voltage (did i explain how i did that?) and written to oem dro 1036 (i think but check in the screenset) which should write it to the screen in the tip volts dro.

the next line has an oem dro 1036 input and an oem dro 1035 (i think but the one for target volts) input and then a compare operation, if 1036 is higher than 1035, voltage is too high so its then terminated with a thc down block

the next line is identical but the inverse, comopare oem dro 1036 to 1035, if 1036 is lower, volatge is too low so terminate with thc up block.

i have added a couple of extras in to mine so that there is no move if the torch voltage is less than 0.8 or mare than 1.2 times the target volatge but i think it is important for you to get this far before making it more complicated, you could also put in a deadband so that if the readings were close there was no move, mine doesnt have that, i havent tried it since unfortunately time for tinkering with the plasma cutter has dried up recently adn the odd post here is all im managing at the moment.

dont hesitate to shout back if i ve confused you with my spelling!

matt