Advice on what is causing some bevelled edges, good cut at other?

[AdrianH]

Still learning a lot of things about this plasma and although using a Chinese cutter I can not blame it all on the machine as sometimes very good cuts at other times I find I am cutting through the metal at a strangle angle.

I am assuming it is down to speed, but may be down to an earthing point and magnetic bow etc so thought I would ask.

For example when cutting shapes like the one below I can get one edge of the letter to be nice clean cut with straight edges, but the other side of the same piece can have a definite bevel on it.


On the left side of the fancy V there are definite slopes, on the right side not. On the bottom of the V looks like the plasma was shooting off at 45 degrees. Is this too fast cutting.

The metal is 3mm steel, width is 200mm height 89mm. Chinese cut machine at approx 32 Amps max speed at 0.9 m/s but around the bends will be slower.

Cheers

Adrian

 

[gerrymoore]

It's not happening on all the cuts...I presume you have the torch well fixed in the machine...any movement at all will affect the cut....I had this problem and it took me a while to realise what it was. Also try slightly slower with less amps..it's all a learning curve until you get it right!

 

[stormin]

Is you cut direction correct for the swirl direction? You cet a better cut on one side of the "flame" a bit like conventional versus climb milling produces a different finish.

 

[AdrianH]

It's not happening on all the cuts...I presume you have the torch well fixed in the machine...any movement at all will affect the cut....I had this problem and it took me a while to realise what it was. Also try slightly slower with less amps..it's all a learning curve until you get it right!

The head is bolted to the Z axis, can not get it any more ridged with the design, I will try a bit slower, and less current I am just tending to up the current at the moment and keep the same speed. On the thinner 2 mm sheet I did not have this issue.

Is you cut direction correct for the swirl direction? You cet a better cut on one side of the "flame" a bit like conventional versus climb milling produces a different finish.

It took me a while to understand what you mean on this and how there is a swirl direction on the cheap PT31 torches, but I guess it would be down to the ceramic insert between the tip and the electrode in the machine, will have to check the orientation of the holes. Then I can at least be aware of which direction they are and keep in the same direction all the time. I can also change cut direction in Sheetcam, but, I do not think I can always cut the same all the time, I will always get some cuts going 'climb' rather then 'conventional'.

I will have more of a play!

Cheers

Adrian

 

[AdrianH]

Where is that smiley for face-palm, . DUH!.

Well I found the issue and it was air pressure, I had changed my setup and not thought about it. I had extended the air line from the 1/4" stuff I was using to add a length of some other, added a separator so there now two in the line (one on the back of the Plasma. To cut a long story shorter, the air pressure was dropping to around 3.7 barr or Kg/cm2 when I should be running at 4.8 barr around 63 psi.

So out and bought 50ft 3/8" air line cut it down stuck it in and problem sorted, constant pressure as it should be.

And the end result is much better.


Still at 0.9 M/s travel and current down to just short of 30 Amp. 3mm steel.

Cheers

Adrian