Re: [CAD_CAM_EDM_DRO] Re: plasma torch water table or dust collector

On Friday 26 December 2003 16:05, jeff_birt2000 wrote:

> The first question to ask is what you are going to cut on the table.

We are intending to cut steel plate most of the time but aluminum could be a
possibility.

> I would NOT reccomend a water tabled if you cut a lot of aluminum.
> The molten aluminum passing through the water oxidizes very rapidly
> leaving aluminum oxide and hydrogen. The hydrogen will raise out of
> the water and collect under large plates which can (and has)lead to
> an explosion. A local company I used to do service work for blew the
> cross beam off their machine, it landed about 20' away. They were
> lucky noboby was hurt.

Wow, I guess you'd want to be able to deal with gas buildup then if water was
the choice.

> A water table is great for steel. The tank needs to be easy to drain
> so that the water can be changed to prevent sludge build up or
> biological growth in the tank. There also needs to be a method of
> raising a lowering the water level to facilitate changing sheets.
> Normally this is done with a large air bladder in teh bottom of the
> tank.

We'd planned on sloping bottom in the tank and be able to circulate water from
the high to the low point so that the slag and crud would migrate with the
current to the low point, and then possibly use a continuous chain with
scrapers to drag the settled out gritty stuff to a location where we could
scoop it out. What do you think?

>Also if you must cut aluminum on a water table you should add
> oxygen to the water by blowing air through it (think fish tank). The
> torch you use must be able to be used on a water table as water can
> cause starting problems.

Planned on using the Hypertherm 1650, guess we should check with them huh.

> In contrast to the other advise you recieved some contries require
> plasma cutting to be done underwater to shiled the operators from the
> UV created while cutting.

So, it must be an accepted practice then for certain applications.

> For a ventilated table you need to make sure your drawing enough air
> through the table (draw from table bottom) to prevent smoking the
> room out. Some places just vent the exaust outside but your locality
> might require a filtering system. When choosing a filtering system
> by one for the intended purpose or it will not work properly.

The city would never let us discharge outdoors. I agree the thing must be
designed properly, I'm a HVAC mechanic, would you know where i can get the
design guidelines?
Seasons Greeting,
Denis Casserly

>
> Jeff Birt
>

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