Internal arcs and corners...

[davek0974]

Have a look at the picture here, its an internal arc, about 8mm side-side, 3mm steel, 45A.

Is the way the lower side of the arc is smaller than the top side normal or a sign of something needing adjustment/tuning??

I realise it's caused by the tail of the arc not keeping up with the top but is this degree of difference normal?

Just looking for improvements here, work is being done so its more educational research.

I also see the same result on internal corners.

[BTA Plasma]

Yes if your not using an algorithm for speed, amperage, tip volts while maintaining proper cut height for the physics of small geometric changes in your tool path and simply using constantly velocity your trailing edge will have a very pronounced geometric difference between the top of the steel and the bottom. But judging by the look of the rest of the part it almost appears that you have loose mechanics.

[davek0974]

Ok, normal it is then

This is a pretty standard Stepper Motors/Mach3/SheetCam setup so no on-the-fly amperage and speed stuff.

The motion is tight but i do suffer from a bit of slat wobble or if it really gets going I get whole-table wobble as I have acceleration pretty high.

[Brand X]

45 amps should not have much of a trailing edge on that thickness.. I would try lowering your amps with a 30 amp nozzle, and see if the changes are positive. Maybe you will hit a sweet spot with everything.. Lot of things can work against you with too many amps for the thickness. IMO...

[davek0974]

Interesting, I will try lowering the amps but really don't want to go down to 30A consumables as they are unshielded and won't last as long as the shielded ones.

Maybe its a case of too hot, too fast?

[Brand X]

You will lose arc density by lowering the amps to 30 with 45 amp nozzles.. Might try both ways, and different amps. I get awesome cuts life at 30 amps exposed tips. My Victor pierces, and cuts at a way higher distance, so a low chance of messing the nozzle up.. I posted my cuts, and they are sweet.. I could never get close them using the 40 amp, shielded setup. It does other things well, but that's not what I wanted. My Esab had shielded, and un-shielded low amp nozzles, and it was super sweet down low There is probably a sweet spot your machine/table likes to run at, and if it takes 30 amp nozzles, then I would use them. At least give them try, and then you can decide if it's worth it to you.. I bet they come out nice, that's if you don't mess the nozzle up right away..

[davek0974]

I would be fairly confident the 30A unshielded will do better, I use them on 1.2mm stainless and the cuts are amazing. But the pierce height is only 2.5mm and cut at 0.5mm and pretty easy to foul up.

i will try some different settings as soon as i get a chance.

[Brand X]

Here is what I am waiting for.... Hypertherm 55 /newer torch design, and more tip amp sizes/range in consumables.. I would finally buy a Hypertherm if they ever built one.. It would be sweet, and I bet it's coming soon.. Things like the fine cut 25 amps of the LT torch,and a bit better pierce range on top.. That would hit a great sweet spot for small CNC guys..

[davek0974]

I had the 30XP first, a great little machine with fine-cut consumables, worked lovely but only had hand torch and hand consumables - not good for CNC.

If we had fine-cut shielded consumables in 30A and 45A ranges for the PM45 it would be great, the 45 seems to have been left behind a bit I think which is a pity as it really is suited to smaller shops like mine with only single phase supply and smaller cnc machines.

[Brand X]

So bump the power up a bit, make more Nozzle sizes, styles, bring the later model (machine) torch/nozzle designs into the fold.. Then it will do things on the low-end the larger machines can't match..Also make it pierce .500 better.. (Less time)for good nozzle life there.. Something is going to happen ,and I hope it's those things.. I had the Esab 400 too, and many others so I get the low-end nozzle options, and what it brings..That was a really nice unit too, and it was a powerful 30 amp machine. If they don't built it someone will.. Now that Victor, and Esab are in NH working on stuff..

[beefy]

Dave,

that looks like what I typically get. With sheetcam you can try a few tricks in that situation and use the same techniques that are used for hole cutting, like really reducing speed, turning of THC, etc. The trailing arc with plasma seems to be its weak spot and it really shows around corners, tight bends, etc. Of course any time you do a slow down, you'll need to turn off your THC so it doesn't dive. Hopefully your system doesn't pause each time the macros to turn THC on and off are used from gcode.

Keith.

[SeanP]

I see that going on with mine a good bit Dave also, not sure there is much you can do about it other than a slowdown rule in that area like others mention.
I used to use action points for that job, but I'm not sure they work right now, I keep meaning to check those out again.
Gave the 30a parts a try again the other day on some 2mm mild steel, can't make my mind up on them really, yes you get a squarer edge but I got way more dross and couldn't get rid of it slower or faster, not bad to remove from steel but I had the same problem on stainless too and that's a pain to remove dross.
I seem to get far less dross with the 45a setup, smoother cut as well I would say, the 30a shows every judder ever though its slower.

I cut that new tree of life in 2mm, it did ok with thc really was surprised how smoothly it ran, I went with 2900mm/min 83v

This is the back side of the 2mm stainless, best I could get at 2700mm/min

This was in 2mm stainless as well.

[davek0974]

I had a thought it was pretty normal due to the process. Will try some messing around but it's mainly educational.

That tree looks great Sean, what are you using for the surface colouring?

The stainless I have seen before, that was pretty much how the little 30XP cut, pretty rough and damn hard to get rid of. Stainless does seem to prefer being hit harder.

Thanks for the pics.

[SeanP]

Thanks the colouring was just propane torch and 2 part car lacquer.

[davek0974]

Very nice indeed

[davek0974]

Quick tests show that the bevel on the part above can be drastically improved by using a sheet cam rule to turn the THC off and drop speed by 40-50% then turn the THC back on again. I used a distance of 2mm before and 2mm after the arc.

Worth doing i think, no change in dross was noticed. I guess using this on internal corners will also work.

I also tried a straight line test on 3mm Alu in segments of 100mm reducing speed by 500mm/min each step and it seems I can drop by about 1000mm/min from my current speed and have no change in dross at all, this will enable sharper corners and curves etc - clearly I am running at the top of the window for good results and the span seems to be about 1000-1500mm/min.

Some more useful notes to make there

[davek0974]

Had a little play today, very small detail, 3mm steel 45A

On the right is normal speed and on the left is 50% reduction in corners and arcs.

It seems that although there is an improvement to be had by slowing down, the limit is about 50% - any slower yields no benefit.

I'll leave the rules in sheet cam and see how it goes on a job.

[Jefferyea]

Hi Guys,

Could someone help me the internal database hasnt started in over a month, Windows update has been disabled and plan to run these this weekend using the WSUS. This is the first time ive used this. Im a bit concerned from reading online if the internal database doesnt work I wont be able to use the WSUS is this correct? Sorry.

Thanks
Stephen

[davek0974]

LOL, I think you want the Windows support forum mate