CNC machining

CNC Machining
(AKA the birth of Logic Industries)
It was a cold, rainy January night. Two men sat huddled in a small study on the first floor of the Old Rock House, intently pondering the archaic symbols. Tonight was the culmination of what seemed like eons of preparation. The men tested the power supply, then hooked the electrodes to the motor. A few swift keystrokes into the computer, and the program was executed. The shaft turned slowly to the right one half of a rotation, stopped, then reversed its direction and returned exactly to its original position. The two men erupted into enourmous cheers, the kind usually reserved for those rare occasions such as breaking a 10 year losing streak or landing a man on the moon.

At this point that I knew I had conquered motion control. That’s right, Bryan & Ryan’s little science experiment of trying to turn a cheap manual milling machine into a full-blooded 3 axis CNC was finally over the hump. The mechanical side of the conversion was easy, but this electrical stuff was a mystery to both of us. The mechanical conversion took weeks, the electrical months. Finally we figured out the secrets of how to build the “magical black box” that contained DC motor drivers and an external power supply. This magic black box was then connected to an ordinary desktop computer and translated step & direction pulses sent to the computer’s printer port into useful motion out of the DC motors. Amazing!

The manual milling machine - before the conversion

All that was left was to mount the motors to the machine and see how it would cut. This page is meant to be a roadmap through the CNC conversion process for those that might want to try it themselves.

For a base I chose the benchtop milling machine shown at the right. It seemed like a logical place to start, had a dovetail column, and appeared to meet my needs at the time. In retrospect, I really had no clue what my needs were, but hindsight is always 20/20.

In reality, I had very little machining experience. I really didn’t know how much spindle horsepower I required. I didn’t understand the feeds and speeds I would need to machine at. I really just started with the manual machine, learned a little about machining by using it manually, and proceded to convert it to a 3 axis CNC milling machine in the process.

The black box - Gecko Motor Controllers

Above you see the “magical black box.” The contents of this box and how to use them are what took me the longest to figure out. I’ll outline the basics for you:

Step 1:
Create a model of what is to be machined using a CAD (computer aided design) program.

Step 2:
From this model, generate toolpaths and save as ISO standard G code. The toolpaths may be programmed manually if simple, or can be generated with the help of a CAM program (computer aided machining).

Step 3:
Use a CNC program running on x86 PC to convert the ISO standard G code into commands that will be fed to the motor controllers. This machine sent the output through the parallel (printer) port. The controllers then send the proper voltage & current to the stepper or servo motors.

Some of the parts made (aluminum)

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