[daconfusion]

Hello:

Can someone please point me to the reasoning or theory behind the need for a water table for CNC pasma cutting?

Also, once I understand that need, which I assume is:

Slates of replaceable metal that provide enough (maxium) surface area behind a sheet of metal to "blow back."

Any reasoning behind the water? Do the slates of metal act as fin coolers?

If so, would I need to perform heat transfer calculations to find the ideal fin dimensions for maximum cooling?

My fin design is rusty, but I can dig it up once someone helps me understand the need of a water table or its purpose.

Thank you!

[jimcolt]

The primary function of a water table is to trap hot microscopic particles of the materials you are cutting....which would rise in the air in the form of smoke and fumes....and cool them with water and sink them to the bottom of the water table. Fume and smoke control. Using water to perform this function is often less complicated than using a downdraft (fan that pulls the smoke/fumes) system for fume control.

Some large industrial cnc plasma tables actually have water tables with raise lower mechanisms that allow for submerged cutting......which also cuts down on audible noise as well as ultraviolet light from the plasma cutting process.

Water in contact with the plate can have some detrimental effects....such as causing a rougher cut edge (production of hydrogen from disassociation and electrolysis can cause the plasma arc to create a rough edge), more dross (resolidified metal on bottom edge of parts), as well as corrosion of the part (rust).

The slats in the cutting table are there to hold the plate and to conduct the positive side of the plasma electrical circuit to the plate. They are ultimately scrificial and must be replaced (usually a year or two) when they get covered with slag to the point that cut quality can be affected.

Jim Colt Hypertherm