Home made desktop CNC milling machine
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Abstract
I made a small desktop 3 axis CNC milling machine during the xmas holidays in 2008 and completed it sometime in Jan 2009. The project was inspired by another desktop CNC project (Easy to build Desktop CNC Mill) and motivated by holiday boredom. The work area is about the size of an A4 paper. |
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Table of contents Hardware The general work area is shown in Figure 1. Since the milling process is quite noisy, I'm operating it in the unused bungalow at the back of the house. The milling machine was made from common parts that can be found at Bunnings or an automotive store. I'm using stepper motors from an old laser jet printer, a standard computer power supply for 12V, an off the shelf stepper motor controller from the US, and a Dremel 300 as the milling tool. 
Figure 1: Work area Figure 2 shows the milling machine from the front. There is quite a lot of junk in the background because the bungalow is used a store room. 
Figure 2: CNC milling machine Figure 3 shows how the threaded rod is connected to the stepper motor using a rubber hose for the coupling. I stole this idea from the Easy Desktop CNC mill mentioned in the abstract. I think it's very clever. 
Figure 3: Threaded rod and stepper motor coupling using rubber hose. The threaded rod and nut are mounted to the base using plumbing copper brackets, as shown in Figure 4. There was a noticeable backlash using one nut so I used two nuts. Originally, I used a plastic base but the compression due to the bracket on the nut caused a slight bulge and created an uneven working surface. I replaced it with a 4mm thick aluminium sheet. 
Figure 4: Thread/nut mount. Two nuts are used to reduce backlash. Figure 5 shows the ball bearing support for the x-axis rod. The ball bearing is needed because the long rod wobbles quite significantly, where as the other axis are short enough to remain rigid. I used a piece of rubber hose to make a tight fitting between the rod and ball bearing. I appeared to have misaligned the bracket slightly in this picture. 
Figure 5: Ball bearing support for the x-axis. The parallel port stepper motor controller is shown in Figure 6. I used 3 EasyDriver controllers for each motor. These controllers really are easy (like shooting fish in a barrel). They accept step and direction as input, 4 wire output for the bipolar stepper motor and 2 input for power (from 7V to 30V). On the board is an adjustable current limiter, which means you don't need to build a separate voltage regulator for the stepper motor. The controller is set to 1/8 micro stepping by default. The controller works without a heatsink but I added two fans to make sure they run cool. There was a time when the motors were acting funny and jittering randomly on a hot day. I didn't figure out if it was the motor controller or power supply. The two holes for the fan was cut using the milling machine but due to the plastic melting they came out pretty rough. 
Figure 6: Motor controller using the EasyDriver board. Figure 7 shows some of the Dremel tool bits I have been experimenting with. Some have been burnt due to 'ambitious' milling in MDF wood, I set the feed depth too deep and possibly set the Dremel RPM too high. 
Figure 7: Dremel tool bits used. Some of the tools are burnt. Figure 8 shows Tux (Linux penguin mascot) engraved on wood, one of my first tests. 
Figure 8: Tux engraved on wood. |