[Firebass]

I have a Thermo Dynamics Cut-master 75, I bought it new in 2005. It's a good working manual machine. I called the factory to see if it could be used on my new cnc table and they tell me it is not set up for machine use and it is a High Frequency Start...Not very good news for me... So my question is: Has anyone successfully used a similar high frequency machine on they're cnc cutting table. Any input or help would be appreciated. I have a dynatorch THC.

Firebass

[hts_thai_bk]

We used a 100 Amp Hi Freq on a CNC table and yes it can be done. But How vauable is your time? We spent weeks, no maybe months before all of the intermitent faults and glitches disappeared. Plus the torch technology keeps improving so a new unit may pay for itself quickly in regards to tips and electrodes. Thermal Dynamics has a new line out called "TRUE" you may want to look at.

BK

[jimcolt]

There are over 100,000 cnc cutting machines operating in N. America with high frequency start plasma systems...with arc voltage feedback torch height controls. Ten years ago....virtually all plasma systems were of the high frequency start variety...including entry level hand cutting systems.

Today...most high end industrial plasma's use high frequency start...as this technology allows for better cut part accuracy and longer consumable life....by allowing the design engineers to develop consumable parts that are held in near perfect alignment. All Hypertherm systems over 100 Amps (Max200, HT2000, HSD130, HPR130, HPR260,HT4400, HT4001) use high frequency start...and these machines all end up on cnc machines with arc voltage height control.

Air plasma systems today...for the most part...use a moving electrode or moving nozzle (also known as "solenoid start") to ionize the plasma gas. The main reason for this technique is to make these systems smaller, lighter and less expensive as compared to their industrial strength cousins....and the advantage is that there is no "high frequency" electrical noise generated that can affect sensitive computer and electronic controls. Because of this relatively new torch starting technology...a whole new line of entry level...or hobbyist grade cnc cutting machines has emerged with lower cost electronics and cnc controls.....many of which cannot handle the electrical noise emmitted from a high freq. start plasma...but work quite well with the newer start technology.

To answer the question about whether your THC or CNC can handle high frequency start...you must go back to the manufacturer of your equipment to determine compatibility. Many of the lower cost cutting machine companies, including Dynatorch and PlasmCam, have improved their newer systems to be compatible with high frequency start.

Jim Colt

[Torchhead]

If you can keep it from resetting the PC itself, our MP1000C series will work since it has total analog isolation from the Plasma Tip Volts. With proper grounding our older units would work, but grounding in high noise conditions is as much art as science.

Our THC is not compatable with the DYNATorch Controller/motors so you will have to look to them and their particular THC as to what they will support.

We have several hundred units in the field working and a lot of them are on older HF start machines. The only ones we have found that just would not work were the MAX100 Hypertherm and the StacPak XL series from TD. We resolved that with the new C series design. Some of the older machines are not HF start...they are CD start (Capacitive Discharge) and were burning out our older sensor cards. We had to redesign and put in added suppression on the Sensor Cards.

TOM CAUDLE
www.CandCNC.com

[Firebass]

I was hoping it would be as simple as purchasing the new Dynatorch SL100 machine torch which supposedly starts the arc with air pressure instead of HF. Then dis-able the High Frequency in my unit. Then make some type of voltage sensing device which runs of the field of the leads.

Thanks for the responces
Firebass

[jimcolt]

The SL100 torch is manufactured by Thermal Dynamics, not Dynatorch. You would have to check with Thermal to see if the torch was compatible with your plasma system. I don't think it is.

Jim

[Firebass]

The SL100 torch is manufactured by Thermal Dynamics, not Dynatorch. You would have to check with Thermal to see if the torch was compatible with your plasma system. I don't think it is.

Jim

Thanks Jim for the input.

Whoops, I meant to say my plasma is a Thermal Dynamics cutmaster 75. I was hoping it would be as simple as purchasing the new Thermal Dynamics (SL100 1 series) machine torch which supposedly starts the arc with air pressure instead of HF. Then dis-able the High Frequency in my unit.

I called the factory earlier but they basically told me what I already knew, that my unit is not cnc ready.

So, if I attempt to use my cnc system with my high frequency plasma does anyone have some good methods of converting older plasma machines to get the following circuits
*ON-Off Relay*. (No Problem basically the start switch)
*OK to Move*. (I guess this is "torch is stable and ready for movement)
*Adjustable Divided Voltage Signal*. (THC) some talk about using the field of the torch lead.??

Also, with all the talk of interference to computer systems when using HF. Is there a damage risk to using HF to the servo motors on the table. Or is the biggest problem just the glitches caused by RF. Dynatorch suggested fiber optics between my duel x drive slave servos if I decided to use my HF plasma system.

I really am not to excited about buying a new plasma machine when mine works fine. But then again if it wont work I guess I'll have to.

Thanks
Firebass

[jimcolt]

There is a little trick you can do that will give the "ok to move" signal to the THC and the cutting machine with any plasma system. This signal is simply a contact closure that indicates that the arc has transferred to the plate and there is current (Amps) flowing through the work cable (ground clamp). This signal is properly called "arc transfer"....although it is also known as "arc good", "machine motion"....and probably has a few other names.

Her is the trick: Go to an electronics supply store and find a magnetic reed switch...these are usually in the form of a small (maybe 1/4" dia.) glass tube with a couple of wires coming out of one end. These switches activate when a magnetic field is near.... Next, find about a 4" long piece of iron or steel pipe that the reed switch slides snugly inside...with the wires sticking out one end. Epoxy the switch inside the pipe. Wrap about 2 to 4 turns of your work ground cable tightly around this steel or iron pipe and tye wrap the cable in place. When the plasma arc transfers to the plate...the magnetic field created between the iron or steel pipe and the electrical current from the ground cable will activate the reed switch.....and you will have a nice arc transfer signal.

I have used this quite a few times over the last 30 ur so years...it works very well!

The "adjustable" divided arc signal: This is an input required for all arc voltage based THC systems. It is a divided ratio of the actual arc voltage as measured between the electrode and the plate you are cutting. (of course this voltage can be found inside the plasma power source..it is the negative and positive DC output). The simplest THC systems use a simple voltage divider circuit which has a fixed voltage division of 25:1,
50;1 or 100;1...or some other ratio that provides feedback voltage to the THC electronics...as the raw arc voltage is too high (typically between 70 and 200 volts DC depending on the thickness and type of material). These simple dividers generally work with newer style air plasmas with non high frequency start.

With high frequency start systems....there is a high voltage (as much as 15,000 volts AC) spike that is directly coupled between the nozzle and the electrode at the beginning of every cut. This high voltage (high frequency) will blow the resistors right off the circuit board in a simple voltage divider circuit. For these types of systems...specially filtered voltage dividers are used that filter out high voltage AC...and only allow DC. Some of the more sophisticated circuits also incorporate a high voltage isolation relay that does not allow monitoring of voltage during the brief high frequency start signal....saving the voltage divider and the THC electronics from early failure. You can compare the high frequency to a lightning strike on a power line that feeds your house...something will probably get damaged.....and this happens every time the arc fires.

High end industrial THC systems (Hypertherm, Kaliburn are two manufacturers) are designed to work with high frequency...many of the lower cost THC systems are designed to work with non high frequency start systems. I would rely on the THC manufacturers recommendations! For similar reasons...rely on recommendations from cutting machine manufacturers regarding the use of high frequency start plasma...in this case the high frequency is not directly coupled (as it is in the THC)...but can couple inductively between the plasma system cables (torch leads especially) and the drive and encoder signal wires that often run in the same cable trac.

Hopes this sheds some light on the subject. Sometimes it is cheaper to find another plasma system that does not use high frequency start! Hypertherm was the leader with non high frequency start with its Powermax systems...but uses high frequency exclusively on its large industrial systems.

Jim Colt

[Firebass]

Jim,

Thank you so much for the reply. Your expertise is over the top and it's people like you that are not afraid to share information that I trust the most. Again thanks. I'm going to take your advise and find a new plasma machine. Makes much more sense now.

Firebass

[Firebass]

Well the bean counters say "no new plasma unit" for now and my machine is just sitting collecting dust. So back to the the Dreaded HIGH FREQ....
Been talking to Dynatorch the manufacture of my retro fit for my home built CNC Plasma table and they claim that they're system if I can give the 3 circuits. "OK to Move" "Start Switch" and "Arc Voltage" they're system will work. IF PROPERLY GROUNDED. PROCEED WITH CAUTION...
So we've found the proper circuit for arc voltage in my unit. Which we will be using Raw voltage. I am seeing voltages from 90v to 230v depending on arc length. And were pretty sure were before the capacitor start circuit. Anyway the meter acts good w/no spikes or erratic jumps during start-up or running. Supposedly the dynatorch system is analog and has been used with HF.

Next is the "OK to Move Circuit" Although I thought I understood this I have a few questions.
I need to make a Reed Switch work. One thing I did'nt catch about that process was, Can you use the work line to make the winding around the iron pipe that the reed switch is in or do you need to use the torch line? And will any common reed switch work or do I need a special sized one?

Wish me luck...
Again any info is greatly appreciated.
Firebass

[jimcolt]

Just get a reed switch that is rated for the current and voltage input for the Dynatorch .....its probably something like 15 volts DC at 100 milliamps....but that's just a guess...you need to check with Dynatorch. Epoxy the switch inside a piece of black iron or steel pipe...the pipe id should be close to the od of the reed switch. I would wrap maybe 3 turns of the WORK cable (the cable that goes from power supply to the plate)....and tye wrap it securely. When the arc transfers to the plate you should see the reed switch contacts lose....they will remain closed until the arc shuts off. More turns will make it more sensitive.

Jim

[Firebass]

Well I finally got my "Arc Transfer" circuit working thanks Jim for the tip. Now I have all 3 circuits I need to make my table work. Whooo Hoo... All I need to do now is mount my gear racks and make a torch holder.. This took a bit longer than I expected. But hey what a education. I've been a manual machinist/fab guy for over 30 years this CNC stuff is fascinating. I'm no slouch as a manual machinist, twenty years ago I dabbled in the cnc concept but it was so damn expensive it did'nt pay.. Now it's affordable and I actually think I can make a profit from it. I guess one of my mill's is next for a upgrade.

Firebass

[Firebass]

I got my machine up an running great without THC. Everything works fine and I can cut parts. But when I hook up the Arc voltage lines I get Communication Errors Is this because of the HF? In the picture there are 2 wires which I have hooked up red and black they were backwards when I took this photo but they are now opposite (positive ground. I get a voltage reading with the meter hooked up and cutting 1/4" mat it reads 109 volts What the Thermodynamics book calls for) and varies depending on torch height. My question is could I have it hooked up wrong?

http://www.cnczone.com/forums/attach...1&d=1219112002
http://www.cnczone.com/forums/attach...1&d=1219113517