Plasma table build, first question....

**irving2008** · 25-01-2014

Steel bearings running on ali profile? Smooth now but that profile will wear; maybe not as fast on a plasma m/c as no cutting forces but eventually you'll find 'loose' sections...

**Davek0974** · 25-01-2014

Yeah I know, but I have a mountain of the stuff :) and it's not going to see production use so we'll see how it goes.

maybe the mk2 will have a steel gantry and welded frame, who knows.

**Boyan Silyavski** · 25-01-2014

It could be good idea to fashion some kind of cleaning brushes in front of the bearings, or a sponge.

**Davek0974** · 25-01-2014

That's possible, maybe some draught-excluder brush stuff.

**Boyan Silyavski** · 25-01-2014

I have seen a very expensive plasma table and it had small motors with brushes in front all the bearing blocks. Amazingly funny.

**Davek0974** · 25-01-2014

Wow, that's a step too far I think ;)

**Davek0974** · 28-01-2014

htmlEncouraging discovery, after another few hours googling I found this excellent thread...

http://www.machsupport.com/forum/index.php/topic,20076.0

The guy modified a cheap HF start plasma by adding a ground wire to the tip thereby tricking the machine into thinking it is in drag contact permanently, this gave him full power plasma without hitting the metal and also cut the HF interference problem a lot.

its an inspired idea I think.

As it's starting with full plasma, could I then start my piercing cut at a more reasonable distance??

this needs experimenting I think....

**Boyan Silyavski** · 30-01-2014

Originally Posted by Davek0974

htmlEncouraging discovery, after another few hours googling I found this excellent thread...

http://www.machsupport.com/forum/index.php/topic,20076.0

The guy modified a cheap HF start plasma by adding a ground wire to the tip thereby tricking the machine into thinking it is in drag contact permanently, this gave him full power plasma without hitting the metal and also cut the HF interference problem a lot.

its an inspired idea I think.

As it's starting with full plasma, could I then start my piercing cut at a more reasonable distance??

this needs experimenting I think....

I remember that one. A great idea.

**Davek0974** · 30-01-2014

The beast lives :)

wired it all all together today, just temporary lash-up for testing without the torch.

after a little debugging and tweaking motor steps and speeds, it is now running very nicely as a pen plotter :)

better than expected, very fast and accurate so far but will be testing for lost steps tomorrow if I get a chance.

are there any figures to aim for I.e.acceleration G's or mm/sec etc, never having run a CNC anything, it's hard to know what to aim for.

**Davek0974** · 31-01-2014

A short vid of the beast playing...
http://www.davekearley.co.uk/LinkPics/CNCVID1.mp4

fun to play with :)

i have the motors tuned to 15m/min , can't remember what acceleration was, this test file was programmed to 3m/min cut.