tweaking plasma for best performance

[bossfrog]

Got my Dynatorch gantry running now, using a Hypertherm 1000 machine torch, and have the EnRoute software for converting BMPs and nesting. Burned my first parts, and realized I need to adjust the offset (parts slightly too small).

Probably need to tweak the plasma for power, speed, and offset. Any suggestion of how to do this? Someone mentioned burning 4" squares and adjusting all three variables, but there must be a preferred sequence to try, or some rule-of-thumb numbers? I will be cutting lots of 7ga, but will also be burning as light as 14ga, and some stainless too. Help?
Ric

[Torchhead]

With the proper THC where you can read tip volts as you cut if you will follow the suggested guidelines in the Hypertherm manual for cut height, tip volts and feedrate for a given material you will find them to be pretty close. The offset for a 60A tip is about .056

General rule of thumb is to use the current setting for the tip you are using. Adjusting your feedrate will do more towards getting a good cut then dinking with amps. One exception is with Fine Cut Consumables. Cuts 14ga like a dream at 30A and a .040 to .060 cut height. I use .035 offset for Fine Cut. Pierce height is critical and needs to be higher than cut height. Your software or Torch controller should take care of that.

4" inch squares happen so fast you can't even adjust your attitude let alone the torch.

Without some way to read tip volts and dynamically adjust the height in small increments you will just be shooting in the dark. Only way then is by trial and error (buy lots of nozzels and electrodes!)

Let us know how the bitmap conversion works for you. I have never seen one that works for plasma cutting on anything but the simplest objects. Maybe EnRoute will be different.

[bossfrog]

My Dynatorch Z axis is arc voltage controlled, so adjusts height and pierces by itself. Sounds like cut speed is a bigger factor than amps? Hypertherm has a chart, but it doesn't have all material gauges, so a little guess work is required. I figured I would change settings before cutting out each square, then label them and choose the best combination.

The EnRoute software really does a nice job at converting bitmaps to vector - there is always some cleanup required, but their tools make it quick and easy. The software is really made for routing and signmaking, so has 3D capabilities that are not needed for plasma work, but works great for profiling too. Sit down for the price - with the nesting software it cost me $1700 through Dynatorch. I think list price is around $3000.

[Big Woody]

[QUOTE=bossfrog]My Dynatorch Z axis is arc voltage controlled, so adjusts height and pierces by itself.]

Your arc voltage control will "keep" your torch at them same height in the cut. You should always check your initial height and correct every day.

I would recomend cutting a 4" square with a 2" hole once a day. You then measure your test square and adjust your kerf comp as needed. You will also know from the square if your X and Y servos are in sync. If both 4" measures (does not have to be 4") are the same then you are OK.

[bossfrog]

I am finally starting to cut some parts on my Dynatorch, after adding an air handler table (total plasma rookie).

In testing some 14ga test patterns, it seems that even though the Hypertherm 1000 can cut at more than 250ipm at 40A, the corners get real choppy at those speeds. I slowed it back down to around 160 - 170ipm to get a decent cut, but the dross seems to get worse the slower I go. I am just using the standard 60A consumables, and am surprised at how rough the edges are. More curf than I was expecting too. Sounds like I need the finecut consumables for the lighter (14 ga) steel? Does it work to run higher speeds but slow it down for corners?

In 7ga, it seemed to run OK at about 55A and 100ipm with a .065 offset, but again, more kerf and dross that I was hoping for. Any suggestions there?

[DSL PWR]

get some lower amp tips for the thin stuff, that will give you a smaller kerf, and probably less dross. Try some 1/4" with the big tip, you should be happier with that.

[cut more]

bossfrog,
I run 14 ga alot on my table (Practicalcnc with their thc). I cut at around 100-120"/min. @ 40 amps with fine cut tips using the powermax1000. The edges
look laser cut but still get a little dross in corners doing decorative stuff.
hope this helps.

[Torchhead]

Congratulations! You are one of the few people that have gotten the PCNC THC to work correctly. If you ever need replacement parts they should be easy to find. There are dozens I am aware of sitting on a shelf waiting for a good home.

[bossfrog]

I ran my first sheet of 7ga last night with my Dynatorch and Hypertherm 1000 - settings at 55A, .065 offset, 90 - 100ipm, and 148A THC. All my 3/8" holes are a little too small - guess I need to go to the .056 offset that Torchhead suggested. Dross comes off easy on larger parts, but stuck pretty hard on the smaller curvy parts. Previous posts indicate changing speed does the most good - should I be going faster or slower to reduce curf and dross?

I have ordered the finecut consumables for cutting 14 ga. My next project is 10ga - I assume I should use the 60A consumables - any suggestions for settings on 10ga?

[Torchhead]

Actually up to about 1/8" cuts nicely with a 40A tip and set at 40A. Kerfs are smaller, less dross and speeds can be cranked down some which makes for less stress on the machine and the operator!

Low speed Dross is usually easy to remove and looks worse than it is. High speed dross is tighter and harder to remove. One of the purposes of the anti-dive setting in MACH under THC is to keep the head from diving into the work as the machine (naturally) slows down motion at the sharp turns or a direction change.

I am cutting 11ga at 90 to 100IPM with a 40A tip and setting. I get consistant 1/16" gaps at a target volt setting of 138VDC and good cuts. The dross is all loose and easy to scape off with a swipe of a low-angle (wood cutting type) chisel.

[Scott V]

Tom,
my Thermal torch cuts quite a bit slower then the Hypertherms. I would be in
the 70/60 ipm range on the same stuff, with a lot lower tip voltage. 105 or lower. I use the exposed tip on that stuff too. A Hypertherm 100 max and a new Centricut torch seems to have the same cut speeds as my unit. I not complaining too much because there are a few advantages on my table for going slower. I did speed up the accelaration (X and Y) from the setting you gave me because some of my corners on thin stuff were rounded off. I have not noticed any lost steps or any other downside yet.

Your THC has been working really well, even being a earlier version. I cut this warped sheet of .050 MS and it followed it perfect. I also cut a 9 ft/.120 aluminum lion for a neon sign maker. No inside cutouts because it will be painted. The THC followed that sheet fine also. I can't see cutting without a THC or some other plate follower deal. I will not comment on how my Practical THC would of worked. (when it worked that is)

Scott

[monk_egram]

What, if any, gasses are you using to cut with ??? I use o2 with the ht2000. I cut everything from 14 ga to 5/8 with 200 amp nozzle and electrode ect. I adjust cut speed, stand off, gas pressure, and feed to achieve nice cuts on all. I also punch all holes since the machine is equiped with a 40 ton ram. I just recently started using a laser to cut 8mm and under with excellent results, laser is the way to go !