plasma cutting help?

[BeNos]

hey all
got myself a cutskill 35amp plasma cutter. now im managing just to cut thru stuff. but im looking to better my skills.
currently trying to cut out some 8mm templates for a rear bar on the car. and for the life of me cannot get a cleanish neat cut. its very rough with heaps of dross on the bottom and even on the top.
havent got any pics but its very average.
current settings are about 70psi air, roughly 30amps i also have a wheel guide set running with a guide to keep it straight.
im possibly thinking im moving to quick but if i move much slower it stops due to no current contact.
any ideas?? tips or links to videos on how to better use a plasma.
any help much appreciated.
ps have tried like youtube and google with no real success.
cheers

 

[Windy Miller]

It sounds like you're moving to slow - try going a bit faster.

 

[BeNos]

It sounds like you're moving to slow - try going a bit faster.

il give it a go but ive also found that if i go to quick it doesnt fully cut thru. and needs to be cut again to go fully thru.

 

[mike os]

more air?

is the air dry?

 

[Mad Mick]

Hi Buddy,your machine is advertised as being capable of cutting 12mm plate,so I suggest you also check whether your tungstone is badly pitted and/or your nozzle is enlarged.If so replace.If they are ok suggest slower speed of travel,also it can help if you use a slightly stop start or pulsed hand movement,this gives the next bit of plate time to slightly pre heat and therefore cut more easily.Hope this helps,regards,Mick.

 

[chunkolini]

Try freehand with a straight edge.
I faffed about making a wheel guide thing and abandoned it, you need the tip so close it is almost touching the workpiece.
try clamping a straight edge where you need to cut, a piece of 3mm thick strip is fine.
Drag the torch along it, sliding your hand on the workpiece (wear a glove) with the tip barely touching it. Make a few practice runs first to get a feel for it. Done right it leaves a perfect edge.

Sounds to me as though you are too far off the surface.

Chunko'.

 

[langy]

I only use 40 psi & 40 amp on mine and it cuts 8mm easily, I think you maybe going too fast.

 

[astro_al]

He's not going too fast if when he slows down the circuit is broken.

Mad Mick - tungsten (not tungstone) electrodes are used in tig welding, not plasma cutting.

BeNos - what is the condition of your consumables? Is the earth well connected? Pressure sounds very high to me, is it correct for thqt plasma cutter?

Al

 

[Mad Mick]

Hi Astro Al,apologies for spelling slip,however I must point out to you that plasma cutters do indeed have a tungsten electrode in the form of a pellet set into the centre of the torch.This is removable because the tungsten wears away.Regards,Mick

 

[Paul.]

modern air plasmas usually use a hafnium electrode insert, older nitrogen plasma cutters use tungsten.

 

[astro_al]

Sorry, I thought they were all hafnium.

Al.

 

[chunkolini]

Could be made of cheese, here we are talking technique not theory.

Chunko'.

 

[astro_al]

Better a post with theoretical content than no content at all.

Al.

 

[Drains]

If you've not got a drag tip (if your tip has grooves in its face then is probably is a drag tip and you can keep it on the work surface), use a piece of steel as a guide as Chunko says, but if you can get something the right thickness to rest inside the angle made by the face of the torch and the tip, you can keep the tip a mill or two off the work surface.

As others have mentioned, tip and insert condition and dry air are important when you're close to the machine capacity (and when not), but keep the gap as tight as you can.

 

[chunkolini]

I did make up a cutting as described by Drains, I used two pieces of angle iron welded together with the gap between them just big enough to allow about 2mm clearance below the tip. It did help.
These days I just use a guide and have the tip lightly brushing the surface being cut, but with no pressure.

Chunko'.

 

[Mad Mick]

Hi All,can't help but interject here.If you know the theory,you can't help but improve the practice.For example,if you are driving your car,(a practical task),it does pay to know your destination,(a theoretical thing in the future).Regards,Mick.

 

[astro_al]

Quite right. Al.