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Davek0974
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Results are in...
30A Machine torch cut on 3mm steel...
30A Hand torch cut on 3mm steel (top line only)...
20A Hand toch cut on 1.5mm steel at a good speed...
The same cut but showing the reverse side (top)...
The back dross knocked off easy, there was none on the front, one side of cut was bevelled, other was straight, i think this is normal behaviour.
SO I will be ringing the suppliers for a smaller torch more suited to 20-50A cuts than the 50-100A torch they supplied
I have also found another user who was sent a massive torch and is now just using the hand torch.
This seems to be the answer.
30A Machine torch cut on 3mm steel...
30A Hand torch cut on 3mm steel (top line only)...
20A Hand toch cut on 1.5mm steel at a good speed...
The same cut but showing the reverse side (top)...
The back dross knocked off easy, there was none on the front, one side of cut was bevelled, other was straight, i think this is normal behaviour.
SO I will be ringing the suppliers for a smaller torch more suited to 20-50A cuts than the 50-100A torch they supplied
I have also found another user who was sent a massive torch and is now just using the hand torch.
This seems to be the answer.
Davek0974
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Tried it on 3mm sheet and much better...
Both at 35A and 1500mm/min, the dross is easily knocked off, the "good" side of the cut is nice and square and within 0.1mm of dimension too.
It seems it just does not like thin steel??
I have some 1/4" scrap somewhere, will try that too, but its looking more promising.
I have a feeling thin stuff is harder than thick stuff.
Both at 35A and 1500mm/min, the dross is easily knocked off, the "good" side of the cut is nice and square and within 0.1mm of dimension too.
It seems it just does not like thin steel??
I have some 1/4" scrap somewhere, will try that too, but its looking more promising.
I have a feeling thin stuff is harder than thick stuff.
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Getting rid of/reducing the bevel is fairly easy to do. The plasma arc is relativley straight sided for a certain distance before tapering off towards the end - excess bevel is often because the torch is too far away from the workpiece. I found a good PDF on it a while ago but boogered if i can find it again.
You can find most of the plasma help tips here.
http://www.centricut.com/Training_Articles.htm
http://www.centricut.com/Training_Articles.htm
Davek0974
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Keeping the speed fixed, I varied the power this morning and got this set of results.
32A
35A
40A
The 32A cut is terrible, there is severe bevelling on the X axis cuts but oddly not on the Y axis cuts, no idea what's at play there?
I think the 35A cut is best, the dross knocked off pretty easy and it's on size.
The 40A cut is not much different than the 35 one so best speed is likely 35-37A?
Overall, I'm not impressed and am slowly losing faith. it seems this machine needs way more power than it should and does not give results to match, yet.
Do any of these cuts look respectable?
32A
35A
40A
The 32A cut is terrible, there is severe bevelling on the X axis cuts but oddly not on the Y axis cuts, no idea what's at play there?
I think the 35A cut is best, the dross knocked off pretty easy and it's on size.
The 40A cut is not much different than the 35 one so best speed is likely 35-37A?
Overall, I'm not impressed and am slowly losing faith. it seems this machine needs way more power than it should and does not give results to match, yet.
Do any of these cuts look respectable?
dan.taylor.1
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Your torch isn't pulling on the axis that's bevelling is it?
Dan
Dan
Normsthename
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I wouldn't worry too much about correct sizes.
Get it cutting nice and consistent first and then you can adjust the Kerf in the software to get it dimensionally correct
Andy
Davek0974
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No, the torch cable is suspended over the top and there is plenty of free movement, the bevelling only happened on the 32A cut but only on the horizontal edges, including the round hole but not quite as bad.
The 35a one seems best but where others are using 20a I'm having to run 35-40a which seems odd to me. I spoke to r-tech about the oversize torch and was told they always ship bigger with CNC because they get hotter! I call BS on that one as the power is the same so surely the torch will not get any hotter than a hand held? Personally I think it would be happier with a 20-50a torch and 0.8-1mm tips.
The 35a one seems best but where others are using 20a I'm having to run 35-40a which seems odd to me. I spoke to r-tech about the oversize torch and was told they always ship bigger with CNC because they get hotter! I call BS on that one as the power is the same so surely the torch will not get any hotter than a hand held? Personally I think it would be happier with a 20-50a torch and 0.8-1mm tips.
Dave, when it comes to dross free cuts even Hypetherm cant produce it all the time, i done a bit a research on this about 7 years ago and cant remember the exact statement but it went like this " can produce dross free cuts obtainable in certain windows" so take from that what you want.
To get the best of cuts on plasma can be a pain at the start and if your torch is running an over size nozzle and under powered, the flame intensity will be affected, the flame is a rugby ball shape and you have to cut right on the edge of rugby ball, to high or too low will cause bevel that's where torch height control comes in.
I built mine just when the THC was being developed and made to work with mach2 in 2003 and just went with the flow and added what was needed to make it a worth while machine, started with scratch start machinemart plasma, then the machine mart plasma king, wow did i make that transformer sing on CNC, no duty cycle, then onto a miller 1250 100 amp until it died, HF nasty thing, next was the hypetherm 1250 in 2005 and things changed, add in the Fine Cut in 2006 and again another big change in cuts up to 4mm, i soon bought the 1650 new in 2007 and still using it today.
So where your at now is that point where this works but im not real happy with the cuts, but from yesterday to today you have improved the cuts already and i don't see the last 40 amp part as bad, keep going with it and if you want to have a look at my cnc you can drop by and have a look at it cutting, my cnc plasma is setup pretty good but it will never never be laser, on par with a hpr 260 on a good day though.
Cheers.
Scot
.
To get the best of cuts on plasma can be a pain at the start and if your torch is running an over size nozzle and under powered, the flame intensity will be affected, the flame is a rugby ball shape and you have to cut right on the edge of rugby ball, to high or too low will cause bevel that's where torch height control comes in.
I built mine just when the THC was being developed and made to work with mach2 in 2003 and just went with the flow and added what was needed to make it a worth while machine, started with scratch start machinemart plasma, then the machine mart plasma king, wow did i make that transformer sing on CNC, no duty cycle, then onto a miller 1250 100 amp until it died, HF nasty thing, next was the hypetherm 1250 in 2005 and things changed, add in the Fine Cut in 2006 and again another big change in cuts up to 4mm, i soon bought the 1650 new in 2007 and still using it today.
So where your at now is that point where this works but im not real happy with the cuts, but from yesterday to today you have improved the cuts already and i don't see the last 40 amp part as bad, keep going with it and if you want to have a look at my cnc you can drop by and have a look at it cutting, my cnc plasma is setup pretty good but it will never never be laser, on par with a hpr 260 on a good day though.
Cheers.
Scot
.
Davek0974
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But surely THC will only come into play when you know where the correct height is first so you can dial in the desired voltage??
Im not overly concerned about dross, it knocks off easy anyway. What is more disappointing at the moment is the fact that angularity seems to vary with torch direction, i.e. the rugby ball is leaning over, and the fact that it makes a pigs ear out of thin metals, terrible bevelling and flame wandering regardless of speed. 3mm and above it gets better.
Im not overly concerned about dross, it knocks off easy anyway. What is more disappointing at the moment is the fact that angularity seems to vary with torch direction, i.e. the rugby ball is leaning over, and the fact that it makes a pigs ear out of thin metals, terrible bevelling and flame wandering regardless of speed. 3mm and above it gets better.
Davek0974
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Seems fairly consistent at least, these three cuts came out the same, quick to clean up, how do they look?
Divots...
These are fairly close-up, the squares are 65mm, it seems at least for this thickness and type of sheet that this setting works ok.
If I had sent these out for cutting, would I expect to get better, same or worse back?
Dimensions are good, within +/- 0.1mm, I know plasma is not hyper accurate so is that good or not?
Are there any signs visible there that mean I could tweak something to get it better or am I doing OK?
Divots...
These are fairly close-up, the squares are 65mm, it seems at least for this thickness and type of sheet that this setting works ok.
If I had sent these out for cutting, would I expect to get better, same or worse back?
Dimensions are good, within +/- 0.1mm, I know plasma is not hyper accurate so is that good or not?
Are there any signs visible there that mean I could tweak something to get it better or am I doing OK?
They look ok to me, quick clean up, they will be fine.
watch the drag lines they tell a lot, they say plasma should be vertical, try slowing the machine speed, it will be a trade off of better cut but more dross. look at the consumables and how they fit in the torch does it all fit nice and tight, is the flame is out of shape to start with. if I'm getting extreme bevel on one side after checking everything i spin the torch 90 degree, does the bevel follow the torch, if so torch consumable alignment is out.
Here's a few more thing I've learned from cnc plasma cutting.
nozzles can be damaged on the 1st pierce affecting every cut their after.
nozzles do not like going over other cuts, anything affecting the arc from going straight down can key hole the nozzle.
nozzles like to be run at full power for best cuts (not nozzle life)
nozzles are consumed ever time you fire a torch in the air.
nozzles cost a fortune but can be made to last longer by careful programming.
nozzles like to be genuine.
watch the drag lines they tell a lot, they say plasma should be vertical, try slowing the machine speed, it will be a trade off of better cut but more dross. look at the consumables and how they fit in the torch does it all fit nice and tight, is the flame is out of shape to start with. if I'm getting extreme bevel on one side after checking everything i spin the torch 90 degree, does the bevel follow the torch, if so torch consumable alignment is out.
Here's a few more thing I've learned from cnc plasma cutting.
nozzles can be damaged on the 1st pierce affecting every cut their after.
nozzles do not like going over other cuts, anything affecting the arc from going straight down can key hole the nozzle.
nozzles like to be run at full power for best cuts (not nozzle life)
nozzles are consumed ever time you fire a torch in the air.
nozzles cost a fortune but can be made to last longer by careful programming.
nozzles like to be genuine.
Davek0974
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Great, thanks for that, oddly enough I had just been reading a document about the gas exit angle, should be vertical - does that match having vertical drag lines too??
The worst part of my internal cuts seems to be the start/end where they overlap. I am using a lead-in on the start but no lead-out as it really was not happy with that when the end of the cut passed the lead-in, still getting a divot though.
Should I be concerned with ramp-in and "wiggle" starts or is that for the big-boys?
Heaviest I'm likely to use is 10mm so is a wiggle-in better on the tip for that or just stick with a standard 4mm high straight pierce?
Start your hole cut from the centre of the hole, give the arc time to stabilise, to get rid of the divot the slug must drop out at the same time the plasma shuts off, a slight over burn can help but now too much or it will divot again.
i measure the lead in cut distance as it passes the end of the cut and try and keep that gap to my kerf adjustment.
Wiggle can help but i don't use it, but i can see it being of use with 10mm plate, i use an 7mm pierce for 10mm plate with a 0.4 second delay. Piercing high can cause arc stretching which again can damage a nozzle, its a trade off for double arcing.
It becomes contradictory to get better cuts and trade off consumable life.
i measure the lead in cut distance as it passes the end of the cut and try and keep that gap to my kerf adjustment.
Wiggle can help but i don't use it, but i can see it being of use with 10mm plate, i use an 7mm pierce for 10mm plate with a 0.4 second delay. Piercing high can cause arc stretching which again can damage a nozzle, its a trade off for double arcing.
It becomes contradictory to get better cuts and trade off consumable life.
Hypertherm UK
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Hi Dave
Been reading this with interest. How is your cut quality looking now?
Been reading this with interest. How is your cut quality looking now?
Davek0974
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Having just sorted out the last few glitches on my little CNC plasma table build, I was looking for some tweaking tips based upon results, as the table is now working pretty much stable and controlled it seemed a good time to go for final messing about.
Attached are three photos, all the same part - front, back and after a quick clean up.
Cut specs were - 2mm black steel, 25A@1600mm/min, 1mm cut height, 4mm pierce height, THC set at 103v.
The speed was arrived at by running cut tests at various speeds and taking what seemed a good result. The 103v THC was arrived at by taking straight cuts at correct height with THC turned off, taking the average reading.
As I do not really know what to look for, I was hoping some kind soul could have a quick look and give me a direction to adjust etc. and I could post the results, would probably save me wasting a whole pile of metal shooting in the dark.
Thanks
Front...
Back...
After ( the dross knocked off easily)...
I'm not too worried about the divots, there is a new version of sheetcam coming and that has over-burn etc plus many other tweaks.
Attached are three photos, all the same part - front, back and after a quick clean up.
Cut specs were - 2mm black steel, 25A@1600mm/min, 1mm cut height, 4mm pierce height, THC set at 103v.
The speed was arrived at by running cut tests at various speeds and taking what seemed a good result. The 103v THC was arrived at by taking straight cuts at correct height with THC turned off, taking the average reading.
As I do not really know what to look for, I was hoping some kind soul could have a quick look and give me a direction to adjust etc. and I could post the results, would probably save me wasting a whole pile of metal shooting in the dark.
Thanks
Front...
Back...
After ( the dross knocked off easily)...
I'm not too worried about the divots, there is a new version of sheetcam coming and that has over-burn etc plus many other tweaks.
Davek0974
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Ok, based on replies from other forums, upped the speed to 2200 which cut a very nice straight line, circle was cut at 70%.
Front...
Back
The bottom test was with THC on, Top test was THC off, speeds were the same.
Failed to cut at one side on bottom run, dross is just as bad as before in all example although the small top dross did disappear at the higher speed.
Front...
Back
The bottom test was with THC on, Top test was THC off, speeds were the same.
Failed to cut at one side on bottom run, dross is just as bad as before in all example although the small top dross did disappear at the higher speed.
Davek0974
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I have been advised that i'm doing something majorly wrong.!
Yes they are crap, I'm almost ashamed to post them, it gets worse too, while waiting for kind souls to comment on my failures, I thought i'd try some 1.5mm again as i have a fair bit of that.
The picture below, 2nd from left was 20A@2400mm/min, I thought it not bad so i set those volts as standard, tried a few more and as you can see, it gets worse and worse to the point where I tried lowering the speed to gain penetration but still failed even at 2000mm/min which even by my standards is slow on 1.5mm.
Most of these cuts were made with THC off.
The earth clamp is definitely attached to the work not the bed.
I really do not know what is going on now, just going in a downward spiral i think.
I even checked the consumables in the thought that i might have blown a tip but they look almost new still, nice clean round nozzle and a small dent in the hafnium.
Yes they are crap, I'm almost ashamed to post them, it gets worse too, while waiting for kind souls to comment on my failures, I thought i'd try some 1.5mm again as i have a fair bit of that.
The picture below, 2nd from left was 20A@2400mm/min, I thought it not bad so i set those volts as standard, tried a few more and as you can see, it gets worse and worse to the point where I tried lowering the speed to gain penetration but still failed even at 2000mm/min which even by my standards is slow on 1.5mm.
Most of these cuts were made with THC off.
The earth clamp is definitely attached to the work not the bed.
I really do not know what is going on now, just going in a downward spiral i think.
I even checked the consumables in the thought that i might have blown a tip but they look almost new still, nice clean round nozzle and a small dent in the hafnium.
