Thread: CNC plasma cut '40 Ford mini dash with sound

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Rather than write this all up at one time, I'm going to do it in installments. Here is the first. I'll get into the table itself in the next one.

I have no idea of how basic to make this, but I'm going to assume that everyone has some familiarity with plasma cutters and how they work. An overly simplistic explanation is that they heat metal to a molten state and blow a channel of air through it. There are all kinds of explanations out there about plasma being the 4th state of matter, solid, liquid, and gas being the first three. However, just as you don't need to know how an internal combustion engine works to drive a car, you don't need to know all the technicalities of plasma cutting to do it. If you want to read up on it, there is a wealth of information available on-line.

Manual (as opposed to CNC) plasma cutting produces edge quality somewhat smoother than oxygen-fuel cutting, as it isn't quite as sensitive to speed and motion smoothness. However, the human hand has definite limitations when it comes to manipulating a cutting torch. The CNC process has the ability to precisely control the speed and directional movement of the torch without human intervention.

It has the additional advantage of being able to combine the most elaborate of sequences into a single canned program. When the start button is pushed on your computer, the program executes and the part or parts are cut. A slight amount of dross must be tapped off the bottom of the edges - a comparatively easy task.

A single part or an entire plate full of parts can be cut from a single computer file. Cut quality is as smooth or smoother than a bandsaw-cut piece, and inside shapes and complex contours not possible with a bandsaw can be cut.

Depending on your software, absolutely no programming knowledge is required. Desired shapes can be generated in a number of ways, and converted into a cut file understood by your CNC software. Some of these are as follows:

They can be hand drawn and scanned into your computer.

An existing (small) part can be scanned into your computer.

Clip art can be imported into your computer.

A photograph can be traced by a drawing program to produce the desired shape (as in the car and motorcycle shapes above)

A dxf (drawing exchange format) file can be purchased on-line from numerous sources. Note that many such files were created by artists and others with no plasma cutting experience, and won't work in the real world.

If you attempt to take a picture of a part you want to duplicate, a perfect circle for example, it will be distorted unless the camera is perfectly centered, which is almost impossible. This doesn't happen with a flat bed scanner.

Plasma arc produces a slight bevel in the cut face, which becomes more severe as the part increases in thickness. This is insignificant in material up to about 1/8" thick (11 gauge). On steel more than 3/8" thick, oxygen-fuel may be preferable as it does not produce the bevel. There are "high definition" plasma cutters that minimize the bevel, but they are quite expensive.

An air compressor is required to provide the air jet necessary for the cut path. Your air compressor must be capable of 8 or more cfm (cubic feet per minute) at 90 psi. Less and your air pressure may become insufficient mid-way through a cut. While this eliminates small portable compressors, you don't need a gigantic unit either. Mine is a 3 hp Speedaire model with a 20 gallon tank, that produces 10.2 cfm at 90 psi. The bigger the tank, the less often it will cycle. Twenty gallons is probably the minimum. A photo of mine is below.

Plasma cutting produces small particles of "plasma dust" that are harmful to breathe, and settle on everything. Using a water table to support the material captures much of this, but requires regular cleaning and creates a wet shop environment.

I solved this problem by locating my little CNC plasma table just outside my basement door, under my deck. When not in use, I cover the small set-up with a fire pit cover. My compressor, plasma cutter, and laptop computer are just inside the door, and the motor and torch cables can be connected in minutes.

I installed a 60 amp sub-panel next to the door to handle the electrical requirements. I keep a small galvanized tub under the table to catch the debris. I wear a little Covid-type mask and eye protection when cutting, and plasma dust is a non-issue.