16g cut hight

[quadboy]

I'm running a 4x8 dynatorch with pm85. What should my cut height be? Book says torch to work distance is 0.06 which is to low and dynatorch says it's to low. I tried 0.100 and it's to low.

[Gamelord]

.06 is where it should be for best cut with minimal dross and longest consumable life.

[Capstone]

I'm running a 4x8 dynatorch with pm85. What should my cut height be? Book says torch to work distance is 0.06 which is to low and dynatorch says it's to low. I tried 0.100 and it's to low.

How can "the book" say it's the right height, but Dynatorch say it's too low? I'm confused Simply put, The "table" never determines cut height, the plasma cutter's recommended settings do. That's like saying your car decides how fast to go, not your right foot.

[tnbndr]

Why do you say "it's to low".???

[quadboy]

Because torch keeps driving into metal. If I bring level up the it's fine. But lose cut quality. With or without thc on

[Capstone]

This sounds like something mechanical with the Dynatorch. THC, or material not remaining flat/level with the torch.

16Ga metal can certainly warp and if the THC is turned off, then problems could arise in spots where the metals sticks up. If you're not using the proper settings for the THC to function correctly then the diving of the torch might result as the controller tries to maintain the correct voltage for the preset cut and speed setting.

Nothing in what you're describing points to a problem with the Plasma Cutter itself, assuming you're using fresh consumables.

[quadboy]

Yep all sew consumables. So you guys cut 16g at .06 for real artsy Stuff with alot of lines in it. my thc is not working and then when it cuts a long straight line it starts working again. I am cutting a 120ipm and 32 amps, volts at 83. Maybe that's too
Fast

[Capstone]

Yep all sew consumables. So you guys cut 16g at .06 for real artsy Stuff with alot of lines in it. my thc is not working and then when it cuts a long straight line it starts working again. I am cutting a 120ipm and 32 amps, volts at 83. Maybe that's too
Fast

I think, and maybe Jim Colt will confirm, that unless you're using the Fine Cut consumables, the PM85 (with 85amp consumables) is overkill and isn't rated to go any thinner than 10g (1/8) mild steel.

If you're using Fine Cut Consumables, or 45A Shielded, then the recommended speeds are way way faster, like more than double.

with a .1 pierce delay, you should be cutting at .06in at 350ipm at 130volts.

That said, most of my problems start when I go any faster than 225ipm, and that's with a Powermax45 at book settings, so I have to trick my cutter into thinking it's using Fine Cut consumables due to the shudder/wavy lines made as the gantry shakes the table during hi-speed direction changes. I can't imagine how it's even possible to make this happen with a PM85. Good luck.

Frankly, I really wish all of the plasma-cutters could be optimized a LOT better for CNC use, because it seems a lot of people have this issue with the table shake affecting the cut quality on thinner materials.

[jimcolt]

The physical cut height is suggested by the torch manufacturer. Different manufacturers design their torches differently.....which makes them work better at different heights.

If you have a Hypertherm plasma torch and the manual says to operate at .06" off the material, then that is the correct height. Cutting higher will generally produce a wider kerf and dross as well as more edge angularity. If your cnc machine and its height control allows the torch to hit the material...then you need to get the height control problem solved. Controlling height to the manufacturers specifications is what torch height controls are designed to do.

The Powermax85 cut very well on materials down to about 26 gauge, using the FineCut consumables. For the Finecut consumables there are two sets of cut charts....the regular speed chart is to be used on machines that can cut accurately at speeds up to 400 inches per minute. The Low speed charts are for cnc machines that are unstable above about 150 ipm.

Jim Colt Hypertherm

[quadboy]

I just have to get thc working all the time. In a cut with lots of Conners the thc shuts off and has soon as a straight line come it jumps up. Buy slowing down it help with that.

[quadboy]

But I'm also cutting flat metal and when I turn thc off it still drives into plate so hard it move it. I hope to get some more time with rus so we can figure it out.

[btburn]

I've got a Dynatorch Super Bee and keep it set at .06, I'm running a Miller though so maybe it's with how the Table is reading volts for the THC? I've only had the torch dive once so far and still trying to figure that out. Check with Leon at Dynatorch, he's always pretty quick to respond.

[urbnsr]

But I'm also cutting flat metal and when I turn thc off it still drives into plate so hard it move it. I hope to get some more time with rus so we can figure it out.

If THC is off and still diving, I would look into interference causing pulses on the Z axis motor. I would also wonder if the table top and the gantry are running true to each other. Or gcode actually commanding the Z axis down. Not necessarily checking in that order. Depends if it happens at the same place on the table or if it happens after each pierce (or not).

HTH
Paul

[quadboy]

It's every possible it's in gcode because it don't do it if I cut straight line.

[biggator850]

I was having a similar problem on 16 ga. Sometimes it would cut great, then all of the sudden the torch would start dragging and ultimately crash on a jog because it would not raise to the proper height. I finally got some help and learned a ton about how the THC works.

basically the THC measures the tip voltage just after pierce and constantly adjusts the cut height to keep the voltage steady. If the initial cut height is too high or too low then the THC will try to maintain that voltage throughout the cut. This is a big problem on thin stuff like 16 ga because the sheet will flex, especially after you have cut a few parts.

If the sheet flexes when the torch touches down, the sheet will rise back up as the torch rises to pierce. This will make the gap between the torch tip and the sheet way too small when the cut starts and the THC will keep adjusting trying to maintain an artificially incorrect cut voltage. The THC will do all kids of crazy stuff.

If the sheet flexes up enough to actually make contact with the tip at pierce, then it will almost certainly drive the torch down throughout the cut. This is what was happening to me, and the traveling head on my Z axis was absorbing the downward adjustment throughout the cut. At the end of the cut the z axis would lift to move but there was so much slack absorbed bu the floating head the torch would still drag, thus crashing.

The easiest was to see if this is the case is to follow your torch head with a wood stick or something you can use to manually hold the sheet down so it cannot flex at the start of the cut. It usually takes a couple of seconds for the THC to take over so you don't have to hold it all the way through the cut. If this doesn't help there is probably something else wrong.

Make sure to double check your ground! I can't tell you how many foul words I have uttered before realizing the ground clamp was laying on the floor !

Hope this helps!

BC

[urbnsr]

I'm sure different THC's have different ways of controlling the height, but the ones I am aware of are preset by the operator for the voltage desired and ultimately, the cutting height. The voltage could be preset too low and that would bring the torch tip down as the THC is trying to match the voltage setting. The voltage setting seems to be somewhat of a variable. I have ran a few 100mm cuts to get the current voltage reading of the actual material and use that reading to determine the setting needed. But I don't have a high-dollar THC, either. Yet.

Paul

[jimcolt]

This something I have posted before in order that users understand the functionality of a plasma height control. They are not all the same....with different methods of sensing the surface of the material, different speeds, different accuracies. Some height control systems are almost foolproof and allow you to walk away from the machine...others require supervision. Bottom line, a well designed height control can control pierce height accuracy, and real time cutting accuracy to plus or minus .005" of the torch manufacturers recommended cut height....this is how you achieve consistent cut quality and consumable parts life. Jim Colt Hypertherm


Torch height control is the single most important aspect of any cnc plasma cutting system...if you are concerned with cut quality and consumable parts life. A properly designed plasma height control system must work in conjunction with the cnc control as well as the part program in order to achieve the correct pierce height, pierce dlay time, cut height, and must have the means to ignore voltage anomalies caused by kerf crosssing as well as machine slowdaowns due to cornering and fine feature cutting.

All industrial quality (read more robust, more expensive) cnc plasma machines have full featured , well designed height control systems.....you cannot buy on of thes machines without height control. Unfortunately...many of the low cost, entry level cnc plasma machines that are designed for hobbyist or small shop applications off height control as an option....which allows these machine builders to offer their products at lower prices. It is not a good idea to buy a cnc plasma cutter without height control....it will not cut as well and it will eat up consumables....resulting in higher cutting costs as well as poor cut quality.

A basic height control will automatically locate the surface of the material to be cut, will retract to a user set pierce height (always higher than the best cut height), will then fire the torch at the pierce height and remain in place for a pierce delay time (to allow full plate penetration before the cut starts), then will index down to the torch manufacturers recommended cut height. Once the x and y axis get to the programmed best cut speed....an arc voltage feedback control takes over the real time control of torch to work distance by monitoring arc voltage (as measured from the torch electrode to the plate), and adjusting very accurately in order to maintain the correct torch to work distance. The cnc has to be able to "freeze" the arc voltage control during normal corner slowdown and kerf crossings, as well as at the end of the cut when the arc extinguishes...this height freeze is to prevent torch diving. More sophisticated height controls also have the ability to auto - calibrate torch to work distance to compensate for normal consumable parts wear....thus ensuring that cut quality will remain constant throughout the life of a set of torch consumables.

A typical plasma height control system consists of a z axis motorized slide with mounting configuration for the plasma torch, a voltage divider /isolator circuit (to reduce the DC arc voltage signal and filter it to a usable level), an electronic control box that monitors the input, output (from CNC and plasma, and voltage divider), as well as associated cables and user interface panel. Some height control systems are "standalone" (will work with any plasma/cnc machine configuration) and some are integrated (designed to operate as an additional axis of the cnc machine.....and is operable through the motion control system software.

They are typically a fairly high price addition to an entry level cnc machine.....but make the system cut like a cnc machine should.....in a hands off automated manner.

[OTHill]

One trick I have done on my Blade runner from Cand CNC is to spring load my dthc till it puts almost no weight on the material. Therefore much less deflection problems on light gage plate.

[B Holmes]

One trick I have done on my Blade runner from Cand CNC is to spring load my dthc till it puts almost no weight on the material. Therefore much less deflection problems on light gage plate.

OTHill, I had the same issue with the weight of the z axis pushing light gauge material down, resulting in a less than accurate pierce height.
I installed Tom's ohmic sensor, and it solved more problems than I knew I had.
That one upgrade has paid for itself many times over, through longer consumable life, and virtually eliminating cutting issues that were symptoms of bad pierce height.

[tcaudle]

removed

[quadboy]

Wow thanks for all the good input. I am now running cut hight at 0.120 and it's cutting great. I also had the cut hight on some 10g at 0.170 and it cut good to. Still need to call rus at dynatorch and see why it's doing this.