On Jun 28, 2012, at 10:02 PM, BRIAN GLACKIN wrote: >> I don't have a downdraft table but I assume you will have to move huge >> amounts of air to capture the dust from the plasma. Quite a bit of the >> dust flies up from the cut point so to be efficient the table will need >> to be completely enclosed to capture the dust. The amount of dust >> depends on the material condition as well. It seems to me that the more >> rust, crap, and dirt on the plate the more dust I see. >> >> I recall reading someones build blog where they immersrsed the metal > roughly 50 mm or so below the water. The plasma would hold the water back > during operation and the intimate water contact kept the dust to a complete > minimum. I cannot recall who did that though....
I have tried submerged cutting on our plasma table (http://wiki.linuxcnc.org/cgi-bin/wiki.pl?GantryPlasmaMachine). It works, but with our Hypertherm 45 the cuts are not the best. I think the molten metal cools too quickly and adheres to the under side of the cut. We get more dross that needs to be chipped/ground away. It isn't unmanageable, but it isn't as good as a cut done (just) above the water. It does indeed keep the dust down, even more than simply having the water table alone but it is a compromise with cut quality in my (limited) experience. I have heard that there are torches designed to cut underwater so perhaps it is a matter of what model torch you have. A more powerful (than the Powermax 45) torch might have no problem underwater, not sure. In general the water table keeps the dust to a minimum. There is still a little that is blasted off the top surface but I would say 95% of the dust is captured in the water table. The thing we are finding is that the dripping water/rust preventer which drips off when people handle parts after cutting is also a mess causer in terms of the floor and surfaces immediately around the plasma machine. There is also a fine steam vapor that fills the room if we are cutting continuously. 10 minutes of cutting you won't see it, 30 minutes and it is quite prevalent. Ultimately I would like to have a mist extractor hanging over the table. We have Green Cut rust preventer in the water and though it is supposedly non-toxic I don't like the idea of breathing it. Even straight water (vapor) will have particles of whatever is on the surface of the metal in it, so a mist extractor would be nice. Tom ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
