THC

[rustyhook]

New to the forum and new to CNC plasma cutting. Just got a table and trying to cut 11 GA (.1196") carbon steel
test pieces.

I'm trying to cut a 4" x 4" square with a 1" diameter circle in the center. I have torch height control so I set my pierce and cutting height at 0.5" in sheet cam and adjusted my table controler to cut at .0625" and pierce at .125". I have 100 IPM set and hypertherm powermax 45 set on 45 amp per manual. I'm using arc in of .2 inch.

The torch cuts the circle ok but leaves 180 degree of cut beveled in and the other 180 degree beveled out by almost an 1/8". Then on the square the torch will run/cut one side of the square ok but after first turn the torch drives down to the metal. Sometimes it is enough to bind torch to material and I have to stop program.

Is there a way to test the THC?
Are my settings on par?
Is there a setting I am missing?

Thought I might ask for some advise.

RustyHook

[jimcolt]

Rusty Hook,

Most likely you simply have some background settings incorrect....however I thought I would post this height control primer as it will help you figure out some cause and effects in regards to keeping the torch at the correct height. I posted this on another site about 6 months ago...and it was helpful to a few...

Just a few pointers on arc voltage height control and things that will affect the relationship between voltage and physical height when in auto mode:

If you are cutting along in manual, with the torch at a fixed height, (say .060") at a given speed (say 100 inches per minute) and your arc voltage meter is reading 120 volts (this is an actual measurement....if you could put a DC voltmeter on the torch electrode and the plate...you would see this voltage)...then the next step is to set the voltage setting to 120, switch into auto height. At this point, without changing anything the torch should stay at .060" off the plate and rise and fall over warpage pretty accurately. You will see the feedback voltage fluctuate....if the plate warps closer to the torch, the arc length gets shorter, shorter arc equals lower voltage...so the THC raises the torch until the voltage gets back to the preset of 120.

If you change one cutting parameter:

1. Slow the cut speed down. Expect the torch to move closer to the plate...this is because the plasma is still burning at a given output power...and with the slower speed the arc reaches out and grabs metal, effectively making a wider kerf. Because it has to reach for metal, the voltage is higher, and the THC moves the torch closer to the plate to maintain 120 volts.

2. Faster cut speed....expect the opposite of above...the torch will rise.

3. Increase the plasma amperage....expect the torch to move closer.

4. Increase and decrease the air pressure during a cut...expect the torch to raise and lower. The voltage that the THC is monitoring is actually the voltage drop through the plasma arc.....the plasma arc is conducting through a stream of ionized air, and by changing the air flow (or pressure) you are changing the resistance of the arc....hence a voltage/height change.

5. Slug of moisture from your air compressor in the air flow. Expect the torch to dive. The water breaks down and dramatically changes the resistance of the arc.

6. Bad workpiece (work clamp from plasma) connection....or a small plate with poor contact to the slats, dirty slats, etc. This will cause the torch to dive.

7. Cutting on the edge of the metal, or into a precut kerf. Dive.

8. Worn torch electrode....if the hafnium insert in the plasma torch electrode has a .020" wear pit...expect the torch to run .020" closer to the plate. If using a worn electrode it is common to have to dial in 5 or 10 more volts as it wears to maintain the correct physical height.

Just a few things to help users think about cause and effect situations with a THC system. Just remember, the arc voltage is just a feedback mechanism...the most important factor for best cut quality is the physical height....so once you get all of the other parameters dialed in...speed, air pressure, amperage...then set the voltage so that the physical height is where the cut quality and angularity is best.

This process is repeatable. If you are doing a cutting job on a particular material today....and the system is dialed in perfectly...cut quality is close to perfect......then write down all of your parameters! If you do everything exactly the same next time on the same material....then expect repeatable results. If you have a Hypertherm system...follow the specifications in the operators manual under mechanized cutting. You will find that the cut speeds listed under the "optimal cut" column...or "best quality" cut column will be very close to the right speed.....the listed physical height, pierce height, and pierce delay times are all worked out as well. The big unknown is arc voltage.....while it is listed in the Hypertherm cut charts, I find that there are calibration differences that will throw this number off from machine to machine....so dial in the voltage to whatever it takes to maintain the suggested physical torch height....and then use that for future reference for your machine.

Jim Colt Hypertherm

[rustyhook]

Mr Jim,

I don't know who you are but I appreciate and want to thank you for the time it took for you
to type up that detailed explanation. I will go back over every step from the start to actual cutting
and continue to try and find this sweet spot. Thank You Sir.

Rowdy

[muzza]

Mr Jim,

I don't know who you are but
Rowdy

Only ever heard this once before,

I was on a trip stateside and I came across a huge gathering, I wasn't sure what it was all about so I asked a guy in the crowd who told me they were all getting ready for President Obama to address the nation. Wow, what an experience I thought, better hang around for this one so I found a spot with a good view and as the president went to start his address the audio system wasn't working. Needing someone with a strong voice Hillary stepped up and asked of the crowd whether there was anyone with some electronic capabilities. Jim Colt was there and immediately offered his assistance, had a quick look, swapped a couple of connectors, turned a few dials and all was working perfect.
President Obama and Hillary were standing there thanking Jim for his help and expertise and the guy behind me taps me on the shoulder and says
"excuse me buddy, don't suppose you know who those two are talking to Jim Colt do you ? "

In all seriousness I would have to say that Jim Colt is the single most helpful person to the plasma cutting community, not just here but visit any forum where people need plasma cutting help and Jim is there. His plasma cutting knowledge is unsurpassed not just in Hypertherm products of all levels but is very conversant with other makes as well, he runs two tables at home and is working on a third not to say he has a lot of toys but to gain complete understanding from our perspective. I have never met Jim personally but have conversed with him both here and via PM and wish I could receive the same level of customer service with everything I purchased. I own a Hypertherm which I purchased because of Jim and will be purchasing another in the new year.
If Jim never stepped foot in the door at Hypertherm again he would continue to earn twice his salary based on all the work he does, I bet the ring tone on his cell phone is a plasma cutter arcing up , thanks Jim
Murray

[rustyhook]

This might be the part i'm missing. I understand everything Mr. Jim has stated so far. But I am unaware of any
"voltage" setting. Is there a setting for voltage or is it a cause and effect sceniro by torch height settings? How do I test this or monitor this? I have a Amperage setting on the hypertherm 45 plasma machine but ya'll are specific on voltage..

Rusty

[jimcolt]

Voltage is the setting on your torch height control. A higher voltage setting will cause the torch to run higher off the plate...a lower setting will cause the torch to get closer or crash into the plate. The Hypertherm operators manual suggests a voltage setting for each materials, thickness and power level...use that voltage on the voltage setting on your height control....then adjust it up or down until the cut height matches the physical cut height falso listed in the manual.

Amperage is set on the plasma system...it is the relative cutting power.

Jim Colt

This might be the part i'm missing. I understand everything Mr. Jim has stated so far. But I am unaware of any
"voltage" setting. Is there a setting for voltage or is it a cause and effect sceniro by torch height settings? How do I test this or monitor this? I have a Amperage setting on the hypertherm 45 plasma machine but ya'll are specific on voltage..

Rusty

[rustyhook]

This is exactly what I needed answered. Thank-You Sir.

My torch height control is simply a knob and labeled as such. It has a dial range of approx 270 degree total turn from stop to stop. There is no ditigal read out of voltage or range to set specific settings within this 270 degree range. So I will simply run simulation's with it till I get a "torch-to-work distance" of .06 per Hypertherm manual and the voltage setting should take care of itself I assume. Per the hypertherm manual, T45 shielded consumables on mild steel range 26 GA to 1 inch is all .06 inch "torch-to-work distance". I don't plan to cut anything thicker than 3/8 inch.

Time to play with the table.

Thanks,

RustyHook

[swidick]

Thanx Jim, Im making adjustments based on your tips. I am glad I chose Hypertherm AKA Jim Colt.