Effects of adjusting volts and amps

[jhsenterprises]

So I tried searching but couldn't really find what I was looking for. I was hoping to get a better understanding of what adjusting amps down from the recommended settings accomplishes. For argument sake, say I'm cutting 16g cold rolled with a hypertherm 85 using 45amp fine cut consumerables. Why do some people adjust the amps down.

Also I've read where others are turning up the voltages from the recommended amount. I'm pretty sure I read one of Jim's suggestions on doing just this for 14g hot rolled with fine cut consumerables, to the tun of 10+ volts. Can someone explain what this is actually doing?

Mucho thanks

[acourtjester]

This is a way to get better cuts, sometime the torch works better slightly higher ( higher voltage setting for the THC). Instead of using 0.060" a higher voltage will move the torch up to maybe 0.070" to 0.080" cut height. Doing test cuts with different setting shows which works best for you.
with fine cut I don't go below 40 amps for thinner metal, I don't cut below 18 Ga metal.

[jhsenterprises]

So adjusting voltage adjusts cutting height?

[tcaudle]

on that table the voltage (Preset Volts ) is set automatically base on the tool you pick in SheetCAM. To override the Preset volts you can first load the code and THEN change the PReset volts up or down. As stated increase the Preset Volts to increase the arc gap (height) . You can also bump the volts up or down as it cuts. If you find a better setting for that tool just open the tooltable in SheetCAM , find that tool in the list and change any of the parameters then SAVE the toolset or it won't be there the next time you use it.

[jimcolt]

Yes, voltage preset is proportional to cut height, higher voltage equals higher height.

The height control reads the actual arc voltage as if you had a voltmeter with the negative lead connected to the electrode inside the torch, and the positive lead connected to the work cable that attaches to the workpiece. It then compares the preset voltage (set by the operator) to the actual voltage....if actual is higher than the preset the THC activates the z axis motor and moves the torch closer to the material until the actual and preset voltages are the same. This is how a height control works on most cnc plasma cutting tables.

On some machines / THC's the operator sets a physical cut height. The torch starts the cut at that height (after locating the surface of the plate then moving to the physical cut height) and samples the arc voltage...then locks on that voltage (it is like auto setting the preset voltage)....then adjusts torch height based on the locked on on sample voltage.

Jim Colt Hypertherm

So adjusting voltage adjusts cutting height?

[jhsenterprises]

Awesome thanks for the explanation on voltage. What about the amps? Why do some people run lower amps, and what does this actually do?

[jimcolt]

If you look at the available consumables for a Hypertherm Powermax85 (85 amps maximum) you will see there are 45 amp Finecuts, 45 amp shielded, 65 amp shielded and 85 amp shielded consumables.

Each consumable set is designed to provide its best energy density (amps per square inch of arc area) at its rated amperage. For best quality cuts you choose the minimum amperage set of consumables that the cut charts (in the operators manual for the Powermax85) suggest for your material thickness. Then you set everything (amperage, arc voltage, cut height, pierce height, pierce delay, cut speed) exactly as the cut charts suggest for your material thickness and you can expect a good quality cut. Different sheets of steel have different chemistry.....so on occasion you need to adjust cut speed, faster to eliminate dross (resolidified metal that sticks to the bottom of the workpiece) , slower to produce a squarer edge. speed is the most common adjustment to improve cut quality...though advanced machine operators often will experiment with amperage and cut height (arc voltage) to fine tune for their particular cutting application.

So....running a 45 amp rated nozzle at 45 amps usually provides the best performance in terms of cut quality and nozzle life. If you increase the amperage past 45 (with a 45 amp nozzle), expect very rapid nozzle wear/failure. If you reduce the amperage below 45 amps with a 45 amp nozzle...expect cut edge angularity, slower cut speeds and a higher probability of dross.

Typically: 45 amp Finecuts work best from 26 gauge to 10 gauge, 45 amp shielded work best from 10 gauge to 1/4" (to 1/2" if your plasma only goes to 45 amps), 65 amp shielded are best used from 1/4" through 5/8" , and 85 amps from 1/2" through 3/4". Each of these consumable sets will cut thicker than I suggest if you start on an edge. The upper limits listed here are the maximum recommended piercing capability for each power level.

Voltage is height, higher voltage, higher height. Amperage is relative cutting power, higher amperage = thicker and faster.

Jim Colt Hypertherm

Awesome thanks for the explanation on voltage. What about the amps? Why do some people run lower amps, and what does this actually do?

[xalky99]

If you look at the available consumables for a Hypertherm Powermax85 (85 amps maximum) you will see there are 45 amp Finecuts, 45 amp shielded, 65 amp shielded and 85 amp shielded consumables.

Each consumable set is designed to provide its best energy density (amps per square inch of arc area) at its rated amperage. For best quality cuts you choose the minimum amperage set of consumables that the cut charts (in the operators manual for the Powermax85) suggest for your material thickness. Then you set everything (amperage, arc voltage, cut height, pierce height, pierce delay, cut speed) exactly as the cut charts suggest for your material thickness and you can expect a good quality cut. Different sheets of steel have different chemistry.....so on occasion you need to adjust cut speed, faster to eliminate dross (resolidified metal that sticks to the bottom of the workpiece) , slower to produce a squarer edge. speed is the most common adjustment to improve cut quality...though advanced machine operators often will experiment with amperage and cut height (arc voltage) to fine tune for their particular cutting application.

So....running a 45 amp rated nozzle at 45 amps usually provides the best performance in terms of cut quality and nozzle life. If you increase the amperage past 45 (with a 45 amp nozzle), expect very rapid nozzle wear/failure. If you reduce the amperage below 45 amps with a 45 amp nozzle...expect cut edge angularity, slower cut speeds and a higher probability of dross.

Typically: 45 amp Finecuts work best from 26 gauge to 10 gauge, 45 amp shielded work best from 10 gauge to 1/4" (to 1/2" if your plasma only goes to 45 amps), 65 amp shielded are best used from 1/4" through 5/8" , and 85 amps from 1/2" through 3/4". Each of these consumable sets will cut thicker than I suggest if you start on an edge. The upper limits listed here are the maximum recommended piercing capability for each power level.

Voltage is height, higher voltage, higher height. Amperage is relative cutting power, higher amperage = thicker and faster.

Jim Colt Hypertherm

Awesome thanks for the explanation on voltage. What about the amps? Why do some people run lower amps, and what does this actually do?

Hi Jim. I have a question about slowing down the cut for a squarer edge. I'll be cutting a lot of 1/8" steel with some pretty intricate slots. I used fine cut on a sample piece and slowed it down a and I discovered that I got a lot of dross. So iI'm thinking about stepping up to the regular 45amp shielded. A square edge is pretty critical on these as theres a tab and slot congiguration where a 3 mm nut must get captured between 2 tabs. If theres an angle where the nut goes, the nut will vear off to one side making the assembly a pain. How much can I slow down the feed rate from the chart and will that affect other things like THC voltage? I already have some cut rules to slow down to 60% and turn off the THC on these small nut capture slots. The slots are 3.2 mm wide x 10- 15 mm long. Theres also a bunch of 3.2mm holes for the screws. Any help would be greatly appreciated.

Thanks
Marcel

[jimcolt]

The important thing is height. The Hypertherm units need to run at .06" off the surface on most materials. If you have the arc voltage set to a voltage that maintains that .06" cut height at a given speed.....then you slow down, expect the torch to move closer to the material, often colliding. Better height controls are linked to the machine federate and when they sense the machine getting below about 85 to 90% of the programmed federate (cut speed) the cnc sends a signal to the THC to freeze in order to maintain correct cut height. This is necessary for best cut quality. Most cnc's with integrated height control built today have this capability. Most machines with an external or standalone height control do not freeze height during slowdown.

Of course slowing down below book suggested speeds produces low speed dross. It is a necessary evil that we have to deal with at times in order to cut with the best quality. (the need to clean dross from low speed areas). Machines with high acceleration (servos or adequately matched steppers and lightweight moving mass) tend to produce less corner (slowdown) dross than machines with heavy mass and or incorrect motor sizing / gearing as they spend less tim/distance slowing and accelerating.

The plasma cannot cut holes by itself. Height control and acceleration are the keys....along with smooth, fluidic motion. Jim Colt Hypertherm

[Rtodahl01]

Ok, I am having troubles too.
The book says 119 volts for 1/4 inch and around 70 ipm
My machine darts then the torch raises almost an inch high and obviously does not cut through.
Should I slow the speed? .
My torch height is set at .06
Hmm

[tcaudle]

You cannot set voltage. Youcan only set a "target" for what you want the voltage to be. Its up to your THC to adjust the torch up (to raise) or Down (to lower the voltage. If your torch is raising up witht he THC on then either the voltage coming back from the torch (real voltage at the cut) is wrong or the voltage you have chosen is too high. The very first thing you have to know is what the voltage is coming back when the torch is at the proper cut height and the THC is off . You cannot doggedly stick to the book values especially if the voltage coming back from the torch is wrong. Lots of things play into the voltage: The Arc Gap (height) the type consumables you have. the feedrate, the thickness and type of material and even the quality of the sir you use.

[Swick73]

ive been trying to get my tabled tuned in on the fine cut setting for 14g. I think now the volt setting is 95 and height .08 with feed rate of 220 and i cant seem to keep the torch head from colliding......any suggestions

[jimcolt]

There are likely settings in your height control or machine software (depending on the make and model of machine and height control system) that are designed to eliminate diving that will occur on corner slowdowns, kerf crossings, etc. I suggest consulting with you machine manufacturer!

Jim Colt Hypertherm

[acourtjester]

when is the torch colliding, is it at the start of the cutting action or latter. if it is at the start you may not have enough delay for the voltage to stabilize, before the THC takes control of the cutting action. Somewhere between 1 to 1.5 seconds is what I use between the pierce and when the THC takes over. Also the feed rate of the Z may effect how fast it reacts, I think some are preset so it is not to fast.

Rtodah01 I use 137 volts and 48 IPM for 1/4" at 45 amps (hypertherm PM65 45 amp nozzle, CandCNC DTHC)

[rons]

With 45 amp fine cut my DTHC does not work very well at book settings or I should say not very constant, but when I raise the volts the DTHC runs like a champ.
See my post
http://www.plasmaspider.com/viewtopic.p ... dross+free