help - too much dross!

[bossfrog]

I am running a Dynatorch with a Hypertherm 1000 using compressed air. With both a 60A tip in 7ga (100ipm, 146V THC) and a finecut 40A tip in 14 ga (90 - 100ipm, 79V THC) I am getting too much dross! I can knock some off with a chisel, but most of it needs to be ground off - pain in the butt. It takes me longer to fix the dross than it does to cut the parts. What am I doing wrong? I wanted to use air because of cost, but if another shielding gas will make the dross chip off, I might consider it. Or, are my settings screwed up?

[Torchhead]

Is your tip gap holding good at about 1/16"?

While a totally dross-free cut in the air is difficult you should be getting loose dross that comes off pretty easy and long straight or arc cuts should be virtually dross free

IF:

You have the right cut gap, the right feedrate, the workclamp to the metal being cut, sufficient clean air, correct air pressure, and new consummables .

If you can adjust your feedrate on the fly then setup a test in the material you are cutting and cut a series of straight lines at different feedrates. Tight dross (hard to chip off ususually comes from either too fast a feedrate or in the case of detail cutting, a feedrate too slow to prevent the cut area from becoming hot enough the fuse the dross to the back side.

I get good cuts with a Hypertherm 1000 and clean shop air, and my 14ga cuts with the Fine Cut tips looks almost laser cut. I seldom have to remove much dross.

[bossfrog]

I know I was running too high of volts on the THC when running a 60A tip in 7ga (100ipm) - I was using a tip protector, and I think it was causing too many crashes. I had increased the THC volts to 146, and it sounds like it should be more like 138? Took the tip protector off, and will try it again at 138.

However, I was running the finecut tip in 14ga as mentioned above, and still got terrible dross stuck to the back. Hypertherm recommended 135ipm cut speed, others here said 100 - 120ipm, but I slowed it down to 90ipm because it lost the pierce and skipped over the top of the sheet in a few places.

My compressor definitely makes some water, but I have two 8' vertical runs of pipe with drains and two filters before the plasma - I would think it would take the water out. Have never heard the torch sputter or anything like that.

Gap - how can you tell if it is cutting at 1/16" while it is running?
Air Press - I am running on the high side of the Hypertherm range (70psi?)
Work clamp - I am not directly grounding or clamping my material - but the table is well grounded.
Consumables are new.
Feedrate is typically around 100ipm.

I will take your suggestion Torchhead, and set up some long cuts at different feeds, speeds, etc. If you can tell me if any of my parameters or techniques are terribly off, it would save me alot of time... Thanks for the help.

[cut more]

Bosfrog,
Do you have a welding hood or torch cutting goggles? I use a cheap auto-darkening welding hood from Harbor tools cost about $50 This way you can see what's going on while cutting other wise you are driving blind!
If you watch the plasma without eye protection you will be driving blind!
What do the parts look like? Are they Artsy things or more geometric shapes?
I
cut a lot of artsy things out of 14 ga. with a Practical cnc with their thc and a Hypertherm 1000. Yes there is some dross but I only get near dross free cuts on more geometric shapes ie. more straights.
I also run around 70 psi with no problem.
The gap while cutting can be a big culprit for bevel & dross with all else the same.
At 90 IPM you may have gone to low speed dross where the kerf gets wider and the dross solidifies on the bottom side and becomes one again with the part.
When watching the cut if you can see the underside the plasm plume should be mostly straight down with air plasma.
Hope this helps.

[Alex S.A]

hi
if the dross has been hard to take off, you can try to increase the speed and decrease the arc voltage. I am assuming that you are cutting mild steel with 20 % of carbon.
trade off: do that keeping in your mind that decrease voltage too much can make the torch crash against the plate.

[bossfrog]

I appreciate the comments - I will get the weld helmet and watch the plume and cut height to see what is going on. I think I may have got off on the wrong foot by using the tip protector, 'cause it kep snagging on the material all the time, which forced me in increase the THC volts. I will try some test cuts to try and reduce the torch volts and increase the speed.

I run production parts with mostly straight lines in 7ga, and some artsy curvy stuff in 14ga. The fine cut consumables make a nice clean cut at 79V (per Hypertherm recommendations), but lost the pierce and started gouging in several spots (at 110ipm) especially in corners, so I ended up slowing down to around 90ipm. Maybe that was the wrong thing to do, but didn't want to hand plasma in too many places.

Torchhead had mentioned clamping to the piece, which of course is what the manufacturers all recommend - do you guys do this, or do you rely on the table being well grounded?

[Torchhead]

1. You can't machine cut with a drag tip. It holds the tip too far off for a decent cut on thinner material (and as you found snags the edges)

2. The Workclamp on a plasma is not "ground". It assumes the level of whatever you clamp it to. You may get enough conduction to the workpiece with the workclamp just clipped to the table and letting the grid connect the workpiece, but I have seen circumstances where that caused problems. I always clamp to the edage of the workpiece and if it's dirty or rusty I will wire brush a spot before clamping.

[bossfrog]

I experimented with 14ga and fine cut tips last night - test pattern was a 12" long x 1" wide slot with rounded ends. Hypertherm recommends 40A and 79V THC at 135ipm. the 135 was too fast, a little jerky on the corners and gouged in a few places. At 110ipm and 79V it cut real nice, but dross was stuck hard.

I started turning down the THC - got it to run at only 66V and the dross was very small and easy to chip off. Thought I had it all dialed in. Then put a more typical curvy pattern in, and it would crash every time! Had to go all the way back up to 79V THC to make it run without crashing, but there is that dross again.

Part of the problem is that the torch pushes down on the material to find a start height, then the material lifts up with the torch and it doesn't start right. But even if it gets started, it seems to crash on corners - I assume this is the diving that I have read about. Not sure if there is any anti-dive settings on my Dynatorch THC. Very frustrating!

[Torchhead]

There is no anti-dive on any THC that is not integrated with the motion software that controls the toolpath. The software has to be able to know what is happening with an upcoming toolpath (look ahead) and keep the THC from over reacting to small angle or corner cuts.

Ragged corner cuts (jerky motion) are the mechanics of the table and not the THC. It has to do with acceleration settings and the capabilities of the motors and gearing to make rapid directional changes (and the software to control those things using a method called Constant Velocity). If your control software is not CV capable you will never get smooth cuts on smaller arcs or artwork with lots of segments.

Once you have established a gap (voltage) for a given material it should be the same for that material every time.

In MACH3 there is the capability to pre-load a material setting and tip voltage and send that to the THC from a table of settings.

[scorpion]

I might be able to help you a little. I have essentially the same setup as you (dynatorch 5x10, air handler, Powermax 1000).

The dive you're referring to: I also expierenced this and here's what I found.

1. Are you allowing the table to find the "hardstop" home before you cut? When I didn't, funny things happen with the Z axis controller and I had multiple crashes. Try re-homing your machine to hardstops.
2. Out of the box there's a feature in the torch settings that slows the torch speed in the corners. If this setting is too high, the torch will slow to the point where it thinks it's not close enough to the material (over-cutting) and it will dive until it finds the correct voltage or crash. Check this setting. Mine is set at 30 I believe (which means it slows the cut speed by 30%). You can actually test this if you want. Make a 5" long slot that has a half circle arc on either end. Create your lead-in at the beginning of the straight so it has to run the full 4" before going into an arc. If it cuts the entire time and crashes in the corner, it's the arc compensation. If it crashes in the straights, it's not.
3. I read most of this thread and saw reference to the drag tip being used. Ditch it if you're using it on the machine torch. It's not the right tip and it's causing excessive distance between the torch and material.

In Reference to the "No Anti-dive" comment made by Torchhead: Though I agree (it doesn't exist), this system actually turns off the height control for holes smaller than 5/8", for the last partial inch of the cut segment (configurable), and in other instances. These features are actually used for the purpose of anti-dive for varoius reasons. For example - at the end of a cut segment (say a circle) you may have a lead out. A lead out would have to cross the lead-in especially if you use an overlap like I do (.125") to give a nice finish. At the time of an overlap the torch will fail to get the correct voltage reading and dive causing a crash...unless the height control is turned off.

A comment on shop air: No matter how much you try you will never get the moisture out of your air that comes from the compressor without some type of filter. There are some that you can get from welding supply houses which look like brown toilet paper. They work well but change often. I switched to a air dryer which takes all of the moisture out of the air. They're expensive but consumable life is increased big time as a result.

Comment on consumables: The better shape your consumables are in the better the results. As they begin to wear you can actually see the cut quality begin to decrease at a point. Crashes are especially hard on your consumables as well as incorrect cutting speed, torch fire without pierce (aka dry fire), and so on. Dialing in your machine is far easier with new consumables than heavily used ones for this reason.

Height Control Settings: My software loaded with the voltage set at 132. I have found the best results leaving it at the factory installed settings. The only time I change it is when I cut 1/2" plate and then I only change it to 133.

Pierce Height: I used the factory setting 3/16" with great success. I increase this to 1/4" only when I have material warpage - typically a function of how the material was stored/transported and not heating while cutting (except thinner stuff that is).

Using 60amp consumables, machine at 60amps, good clean dry shop air at approx 70psi.

• I cut 1/4" plate at 70ipm. Dross is easy to clean and in most cases there isn't much (except in the corners where you expect it because it slows down in corners)
• I cut 3/16" plate at 80ipm. Same as above for dross.
• I cut 1/8" plate at 120ipm. Same as above for dross.
• I cut 1/2" plate at 30 - 35ipm. Dross is difficult to remove but the cut is beautiful. I've actually made my own wrenches using 1/2" plate with great success. Any faster than 35ipm and it won't cut, slower than 30 and torch dives. I don't cut 1/2" too often so I haven't worked at dialing it in using other means. For now I live with the dross.
• Based on my other settings I expect 3/8" plate to be around 45 to 50 ipm.

Using 40 amp consumables, machine at 40 amps, good clean dry shop air - here's where I've had problems. Cutting 16ga I cannot get the dross to fall off easily. For the most part it's the most difficult. I've jumped all over the place trying to get the correct results (from 100ipm to 160ipm). All leave good cut quality but nasty dross. Faster than 160 and it won't cut the material all the way...after typing this I realized that I've not tried to cut slower than 100ipm. I should try that. I expect it to be too slow but maybe I'm expecting the wrong thing. Let me know if you've figured this one out.

I'd be happy to answer any questions if I can help. I can tell you I was extremely frustrated when I started using this system because it's so configurable and has many widgets. Once you find your happy place it's actually a very nice system.

Matt

[bossfrog]

Scorpion:
Thanks a ton for helping the rookie - you ar correct, it is very frustrating at first trying to get all the setting figured out.
Hardstop - I learned this the hard way, like you did - if I don't do a hardstop first, I can't re-zero the torch position - do it at startup every time now.
Torch Speed in Corners - think mine is set at 45, and both you and Leon (Dynatorch engineer) have mentioned going to 30, so I might try that.
I agree with you - ditch the drag tip - I can't see that it is doing anything but causing problems for me.
One big mistake that caused me alot of trouble was with the finecut consumables. The unshielded nozzles wear out very quickly, because the THC volts is very low (79). If the hole starts getting big, nothing works right and all hell breaks loose. With a fresh nozzle, it looks like a laser cut, and dross comes off very easy with a twisted wire wheel. I also needed to adjust my downpressure setting - at the factory setting of 80, it would push down the warped steel, the steel would follow the torch back up, and the torch would fire while in direct contact with the steel. At a setting of 55 it works much better.
I still need to play with the pierce height and pierce delay - mine seems to pause almost a second after firing, and leaves a big divot even with a short lead-in. Speaking of lead-ins, I have never been able to get an arc lead-in to work - it does all kinds of wacky things. I am using all straight line lead-ins now.
Thanks for the setting info, I will try that. For general setup, Dynatorch recommends taking the Hypertherm settings, minus 20% on the speed and plus 5 volts on the THC.

[magma-joe]

Bossfrog, Scorpion,
I have been eagerly following your threads on the Dynatorch learning curve. I also have a Dynatorch system with a 1250 Hypertherm that will be ready for its first cuts in the next few weeks. I built my own table for it out of 3x8" x 3/16 tubing. I also incorporated a water tray. Its a 5'x10'. I liked the Dynatorch air handler but just could'nt afford it. I purchased Onecnc for a cadcam software. Lots to learn. Right now I'm setting up the gantry and getting the rails straight. Anyway, hope you guys won't mind if I ask a few questions in the near future.
Thanks...