Powermax 45 xp test.......

[Steambike]

So i'll keep it short this time, can I / how can I test the running output voltage on my new Powermax XP45 without destroying my meter / scope??
Why?, well my test meter and Proma thc are both showing
between 80-90 volts while cutting ( measured and calculated off of the 50:1 output from the 45 XP at a cut height of 0.06"), but book reading should be 128volts........... so to my mind verifying the raw voltage is the next step.......the cuts seem ok, but i want to get this right! I'm just not certain if this is high frequency or not, if its straight 1-200 volts dc then I have no issues except i'll have to test with machine covers off......
Thanks!

[jimcolt]

The output of the plasma is a squarewave PWM output at about 20 kHz, it is not high frequency. Most digital multimeters will read the output voltage correctly as will older analog meters. Open circuit voltage can be 300 VDC, cutting voltage will vary from about 75 VDC to 180 VDC depending on consumables being used, torch to work distance, material thickness, cut speed, amperage and air pressure (cut pressure, not input pressure). I have run across a number of Proma THC's that read out weird voltage.

1. Set up a piece of metal (1/8" or so thick) so that it is perfectly level.
2. Ensure that the torch stays exactly .060" off the material when cutting at book speeds.
3. I suggest using the 45 amp shielded parts, however the Finecuts will work as well....but much lower voltage.
4. Cut one straight line at book speeds, amperage, air pressure (cut pressure), monitor voltage on the DC output of power supply(on a Powermax45 XP connect to + and - terminals on the main power board inside the power supply)
5. Cut a second cut exactly the same at the same height and attach a meter to pins 5 and 6 on the CPC connector.
6. Divide the raw arc voltage measured in (4) above by the voltage divider ratio, it should be close to the measurement on pins 5 and 6. It will not be exact, but very close.

[Steambike]

Perfect, thank you again Jim,
I walked away tonight as I was confusing myself, but as I have a couple of days off to get everything sorted I will be pushing on again in the morning:)
I know there is an anomoly somewhere ( most likely in the THC) but without reading the raw voltage from the 45XP I had no way of figuring what was what.

So far I am loving the machine, hook up was well documented and straightforward, just got to get things dialled in:)
I also milled up a simple but very useful stepped "feeler gauge" for the 0.15" pierce and 0.060" cut height measurements (my feeler gauges don't go that big) which is already probing to be a huge time saver!
I'll let you know how I get on tomorrow!

[davek0974]

I gave up using the book voltages many moons ago, i just do a test cut at height/speed/current, note the voltage, set that in my THC(CandCNC) and away we go.

I had a Proma once and that too measured odd voltages.

[jimcolt]

In reality the book voltage listings are correct, but only if you have new consumables, and are running at exactly book specs, all specs including cut air pressure, air purity, cut speed, amperage, etc.

The voltage setting is un important, but the physical cut height is very important. The key is to adjust the voltage setting so that the listed physical cut height is maintained accurately during steady state cutting. If you have to set a different voltage to get the correct cut height...then that is what you should do.

On more advanced height controls you do not set a voltage or worry about voltage. You set a physical cut height, the torch indexes down and ohmically locates the material surface, retracts to an exact pierce height, pierces, then indexes down to an exact cut height. x and y motion starts, and when the cut speed achievs about 80% of the programmed speed the height control measures the arc voltage (at a known, correct physical height) and locks on that voltage for the remainder of the cut.

This sample and hold technology eliminates setting of voltage, and compensates / calibrates the height control on every cut cycle. This ensures that as the consumables wear, the physical height remains correct, if the operator decides to change cut speed, the height control recalibrates at the beginning of the next cut cycle. This technology has been in use for many years.......why all height control manufacturers don't adopt the technology....I just don't understand! Plasmacam has had this sample and hold technology for about 12 years on their machines with advanced height control. Jim Colt Hypertherm

[Steambike]

That is more or less the direction I was heading in, but you cleared a ton of stuff up in my mind ready for today, so thanks yet again! So really just one more big question......
As I am trying to mimic the operation of a more sophisticated THC I have built my own ohmic sensing setup which does touchdown before each cut and then goes to pierce height, delays (0.1 second, via Sheetcam) and after pierce rapids to cut height@ 100" per minute ( these work perfectly, I have been checking them often with the "feeler gauge" I mentioned above).
Once the initial high voltage drops there is a delay ( currently 0.5 seconds) and then the Proma looks for whatever voltage I tell it ( based on its display as opposed necessarily to any real value) and tries to maintain it by moving the torch up and down to keep everything nice. ( sorry, I'm kind of talking this through for me, I totally get that you know all of this stuff, and that each machine is different and mine being homebuilt is possibly VERY different)......
so where I am going is here:-
Do you have any recommendations on the Proma settings please? (obviously not volts, that is unit by unit apparently)
delay after start voltage,
Hysteresis ((currently @4volts+-)
And possibly the most important one, (actually not On the Proma) torch height control speed, I currently have mine set to 50" per minute.......
Once I get those setup I guess I start checking the settings in the sheetcam / Mach3 to prevent the dreaded "diving" issues I have been reading about, but so far not had issues with, so any preemptive advice there would be hugely appreciated.
Thanks again Jim (and DaveK, that's good advice too, and what I will do).

[jimcolt]

I'm not sure I understand what settings you need.

Typically with a THC you connect the arc transfer signal as a means of telling the system that the arc just transferred and started cutting the material. Hypertherm units measure current on the work lead, when current is sensed the relay across pins 12 and 14 on the CPC port closes....indicating that the arc is transferred. (this signal has a variety of names...such as "arc good', "motion" etc.)

Once the THC knows that the arc is cutting....there usually is an "AVC" delay (arc voltage control delay) that delays activation of arc voltage feedback (up/down) until the x - y motion is up to at least 80% of its programmed cut speed (any less and the torch will get precariously close or even collide with the material). The amount of delay set here is entirely dependent of the time it takes to get to the cut speed (different acceleration and speed ranges can have a huge affect)....so dependent on your machines characteristics. On more sophisticated cnc's this AVC on signal actually comes from the cnc.....as a contact closure when the cnc knows it is above 80% of the program speed (different totally when you are cutting thick material at 10 ipm or thin material at 400 ipm). Most stepper motor style CNC's do not monitor their own speed, so finding a time delay that works at all speeds/acceleration rates is what you likely need to do.

Z axis speed. Too fast and it will oscillate rapidly, too slow and it may hit the material if it is corrugated roofing. Somewhere in between those two issues is where I would set it! Make sure there is no mechanical backlash or coasting of the z axis. An oscillating, over correcting height control will make really ugly striations on your cut edge.

Every time your machine has to make a sharp corner or small feature or hole, expect (especially on thin materials with high cut speeds) the height control to dive. If your cnc has a "corner lockout" function....be sure that is wired to freeze the THC whenever slowdown occurs. If you do not have a way to do this...then a slower z axis speed will help (torch will dive, but slowly!). For cutting holes you can set a long enough AVC delay so that the AVC does not activate at all.

This is all automated on many cnc machines with integrated height controls (THC is just another axis).

Hope this helps a bit! Jim Colt Hypertherm

[Steambike]

Soooo.........I followed your advice Jim (& Dave) and ad-libbed a bit and ended up with the stuff below, the car and dog are both stuff I cut with my old set up too for direct comparison (these are 14 gauge mild steel) the moose is also 14g, those are roughly cleaned up........the car has Tremclad hammered paint on just because!
The bear saw was a "poop or get off the pot" moment and is exactly as it came off of my table.........it's 16 gauge mild steel ( &4' diameter), all of them are cut with normal consumables (not fine cut) they aren't perfect, but I'm very pleased so far!
Comments / suggestions welcome!
Many thanks again for everything guys!
All credits & thanks to the artists who made the files (as I recall the doggie and Magnum are from here & the moose & saw blade are fine files from dxf cnc files, thanks Jason, I'll be posting them on your Facebook page soon!

LOVE the new Hypertherm Powermax 45XP..............

[Steambike]

And hopefully, the bears.....

[Bigdogbro1]

I also do not use the cut charts. I always test cut every new material and create a new tool for that setup.

[Steambike]

Thats great advice:)
I just installed a switch and LED so I can turn off the outputs from the Proma for height control to test each piece.......progress is being made