I have also not given up!
Summers are very busy for me, im a farmer! Add in that just after i last posted i got offered an old esab magic eye machine for cheap, which i bought and then sold my home made contraption and you understand my absence, its a weak excuse i know! The stuff still goes round in my head buut i just dont get to note it down.
Heres where i am with it.
Im trying to build a new machine to improve cut quality, speed, accuracy etc etc, i have bought a larger transformer type plasma and everything i read tells me my results will only be as good as my thc. As you may have read ive always been of the opinion that using your pc for the processing seems obvious to me, the trouble is you have to get the signal there and get it back again, im sure its quite possible and could be very fast and accurate but we have to be able to integrate it with mach and make it quick and easy and cheap. Invarialy if you want to get it into mach you appear to have to use modbus, this gets accused of being slow which personally i dont buy but for me i think where it falls down is the modbus devices availabe with analogue inputs lack flexibility, fo instance we ended up on much debate about if the voltage signal from the plasma needed to be inverted, if you were able to use a different device with more flexible analogue inputs then maybe it wouldnt. The other thing that worries me with any mach based system is that the only ability we have to adjust the z on the go is simple up or down with no adjustable speed, thats ok but for best results surely a servo responce is required?? My new z axis also has a straihtforward dc window wiper motor on it as it was only ever meant for gas cutting, but this is what the big boys use, so im thinking that in order to make the system as cheap and simple and effective as i can im going to have to sell my soul a little, im thinking i will use a pic or plc connected to the dc motor with a motor controller, much like a servo drive and with an encoder so speed will be infinately variable using a pwn about from the processor allowinf a servo response,. this will integrate with mach as if there were no z in mach, mach has the x and y co ordinates correct and wishes to start the cut it will send a signal tot he plc and the plc will control the z axis move down to the metal, touch off, fire the torch and when the plasma gives the ok to move signal it wil move, the plc then monitors voltage and thc.
It may sound complex but i think it might work and be easier and cheaper!
matt