Re: [CAD_CAM_EDM_DRO] Re: plasma cutting table

Dave,
I was out for a bit so I am playing catch up here, ignore any info you already were given.

> Another question as to how dirty this work is.
>
> Does the effluent (is there and term ? on my lathe I make swarth)
> get above the table ?

yep, It gets above..... It happens when you do a pierce thru. Everything splatters back up until it shoots thru. Once thru, a water tray underneath will help to quench extra smoke and catch junk.

I've always been told that if you use water under Aluminum, you need to watch for the development of Hydrogen gas. Something to do with hot chips and water. So, check into that. I myself only cut
steel. I saw aluminum or run it on my router.

> I had though of using uni-strut as the main rail and to hang it
> upside down and use the uni-stru rollers (a style like glass shower
> doors) the roller being above the table and inside the track.
>
> It seems that using angle iron and some V rollers might be just as
> good or better.

Unistrut may get swarf hanging inside those areas the rollers run. I'd shoot for something more open with wipers to clear teh way for a roller.

> about table size, I was not planning on a large unit, probably only 5
> foot by 10 foot to allow me to cut a 4 ft x 8 ft sheet of stock. The
> overhang would allow the cutting tip to move to the edge of the stock.

I only went 4'x4' when I tried to pick up a 4'x8' sheet of 10 gauge. yikes. I'd need to put a swinging beam in the shop. Most of what I cut are under 12" square, so I just have my sheets sheared to
2x4 or 3x4 so I can handle them.

>>>about cutting speed, 500 inches a minute ? wow ! now that is FAST !

well, I never cut anything that fast, I only have a Hypetherm capable of 3/8" steel. Seems I do best with that around 20ipm, and 12gauge as fast as 60ipm. Funny thing is I am in no real hurry because
it is not for a production shop, only prototype parts. So, I have not had to try to sqeak out every extra minute I could get for a days work.

>
> Do you cut aluminum sheets that fast ? 0.08" thick ? I can see that
> a rack is the way to got for that type of speed. (where do you get
> cheap rack ?
>
> What type of accuracy do you typically get ?
> +/- o.oo5" or +/- 1/64th"

Suprisingly. I think most thin work runs =/- .010.... but again mine are pretty small, some only 6" long so I do not have to compare dimensions to long runs. Some of this depends on getting your cut
width offset set right and also the torch height. That is a science to make your edges vertical. I do not have a motorized Z axis but would build my next one with it.

> and the last question is ventilation. I was planning on a separate
> table pulling a snorkel around below the table. This unit I was
> planning on using a cable pull to move. That would (hopefully) not
> get destroyed from the effluent. do you think this would be helpful ?

ultimately, you need a non flammable flex hose right at the torch vicinity to catch the bulk of it, Then a big hood right over the unit with a full smoke extraction system throwing all your heat
outside just like any weld shop. The one thing you can do to minimize your volume of total exhaust or IF you simply can not send any air outside is to circulate air. I've made numerous spray booths
and part polishing rooms in the following way.... Build a "tunnel" either using fixed wall structures or welding curtains. you need to make sure that no air can come in anywhere except a single open
end. Equipment is placed in the tunnel. Then on the other end of the "tunnel" you either exhaust the air right outside, or run a "filter wall" with a blower housing in a cabinet, then with ductwork
send that air back to the entrance of the tunnel. This works far better than any other methods. Take for example buffing aluminum. If you try to pick up all of the garbage flying off the buffing
wheels right at the wheel, you NEVER get it all. Within an hour of buffing, the person is filthy black. If you place him in a "tunnel" with fresh air coming in behind him, ALL of the crap goes to the
filter wall. The "tunnel" design is pretty much common sense. Curtains will allow you to open the area up when done but like I said, You may need the curtain to slide next to a rigid soffet at the top
to keep air from leaking in. At the bottom, the curtain can have a chain sewn in to keep it on the floor. Of course all of that is another story...........

Chris L