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From Floppy Drive to Movable Gantry CNC Machine

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Today, we look back at how we have progressed with our cnc machines.

I started to investigate how to control cnc movement using a floppy drive. The floppy drive of a computer already had a stepper motor for moving the magnetic sensor over a floppy disk. There was a lead screw mechanism for converting the rotary movement of a stepper motor into a linear movement. The motor rotation either clockwise or anti-clockwise was able to be controlled through some signal source, so that the linear movement would be able to move in either direction. The driver for moving the stepper motor was already incorporated into a circuit board installed at the floppy disk drive. All I needed to do was to find out which wire was connected to the step or direction function. The floppy disk drive would also need to be connected to a power supply.

In order to connect the floppy disk drive to a computer, a printer cable was connected through the parallel port of the computer. However, the floppy disk drive had a Centronics fitting. The wiring connections had to be worked out with the help of pinout drawings of the parallel DB25 fitting matching with the Centronics printer configuration. The wires were soldered in place.

Next, in order for a cnc machine to work, there must be a program that would be able to run the g-code to control the movement of the cnc machine. I found that the open sourced LinuxCNC fitted this role very nicely. However, I had to run the program on Linux operating system. So I dedicated a computer to run this operating system solely for running LinuxCNC for controlling the cnc machine. I had an old computer lying around and this was excellent for the job. A test on the latency of the computer found that it was suitable to be used for my purpose.

My first setup was connected to the computer and operated on a file in LinuxCNC. Connected directly through the parallel port, through a printer cable leading to the floppy disk drive, the drive mechanism was able to move according to the commands delivered through the printer cable. From this first setup attempt, I was encouraged when I noted that I was able to control that single motor in the floppy disk drive.

There were more tinkering, experimentation and learning experiences following this, some of them having disastrous results, but getting more confident, I acquired bigger stepper motors from old printers, bought other hardware and started to design and build a movable bed cnc machine. With no idea how powerful or damaging the motor would behave when in motion, I played around experimenting with breakout boards, stepper motor drivers, counterweights and fitted the movable parts with bearings. Eventually, I had a workable movable bed cnc machine.

After a while, I was not satisfied with the small work piece area that the movable bed cnc machine was restricted to.

So I designed and fabricated a larger movable gantry cnc machine. The X axes would be driven by two stepper motors moving together. Initially, I had wanted to drive both the X and Y axes by timing belt because it was difficult to get lead screws that were long enough for my design. However, due to limited space available and problems with belts, I later converted the Y axis to lead screw drive.

There was a period of experimentation and improvement before the machine was deemed fully reliable. However today, I could say that it had given trouble free service for quite some time and it could be relied upon for accurate cnc work.

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