7/21/2019 3-Axis CNC Milling Device

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Robot Pages of Jaap Havinga

Mechanics Simulator

Snuf

BiPed

BiPed II

Mini Biped

Battery Charger

Hardware Programmer

RC Servo controller

CNC

Schematics

Pictures

Links to other sites

3-axis CNC milling device

I've build this 3-axis CNC milling device for milling small mechanic parts. Also, it's capable of

engraving and drilling PCB boards. The milling device is a stepper motor controlled x-y table,

and a motorized (z-axis) stand for a 'Dremel' tool.

Figure 1: CNC milling machine.

The effective work range is 160*160*65 mm and the mechanical resolution is better than 0.1

mm (stepsize = .02mm).

Mechanics

The device is build of Aluminum strips and profiles. The electronics and power supply are

located in the lower part, and the actual x-y table is constructed directly above it. Due to the

weight of the power supply the table is quite stable. I'm using bearing reels for guiding the

movement in x and y direction. The movement is driven by a screw thread that is kept in place

by radial and axial bearings (see figure 2). The Dremel spindle is attached to a part of a Dreme

stand. This part is mounted on an aluminum stand, and the lever of the Dremel stand is replaced

by a belt-wheel that is driven by a stepper motor (z-axis) (see figure 3). Look at this pagefor

more pictures

7/21/2019 3-Axis CNC Milling Device

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Figure 2:The x-y table

Figure 3: The modified Dremel stand with z-axis driver.

Electronics

The machine is controlled by a PC via the parallel port. The electronic part of the device

consists of essentially most of theprogrammerinterface described elsewhere, that is driving the

output stages of the stepper motor drivers. Each uni-polar stepper motor driver is build of a

current controlled PWM power source and some power switches to switch the coil currents.

For a change, I did not use dedicated chips to realize the drivers. See the schematics.

Software

The software is running on Windows XP and enables me to directly control the milling machine

and to execute a Gerber 274 file. Since the same electronic interface as the programmer was

used, I could happily copy the low level driving code and drivers. The maximum steppingspeed seems to be limited to about 500 steps/second. Since I did not implement acceleration,

the stepping speed is limited to 250 steps/second.