I’ve found some more time to progress my computer controlled CNC router and assembled the stepper motor controller. The router has 3 axes (x,y,z) and each is moved by a stepper motor driving a ball screw. This amplifies the thrust of the motor substantially, allowing the router to (hopefully) lightly mill aluminium.
Each motor needs to be controlled by a computer, which adjusts its direction and speed as appropriate for the shape required. By coordinating all 3 motors, complex shapes can be cut.
To drive the motors, I bought a full 3 axis stepper controller kit from ebay.
This included the power supply , 3 stepper motor drivers, a PC parallel port interface board, stepper motors and cable. The rather old fashioned parallel port controls the motors by pulsing pins. A pin is allocated to direction and movement for each motor. Other pins are used for the switch inputs. This is a rather archaic way of controlling things, more modern systems would use a USB type controller, but these are rather expensive.
The router requires a set of limit switches, one at each end of the 3 axes. These prevent the machine from destroying itself if any moving part tries to go past its maximum position. When the computer detects one of these switches changing, it shuts the system down before any damage is done.
I designed and 3D printed a mounting bracket to hold the connectors I am using to connect to both switches and motors. After fastening all the components to an off-cut of plywood and wiring up, it looks pretty good. I used bootlace ferrules at the end of each wire to reduce damage caused by the screw terminals.
Each row of the silver connectors supports one axis.
The mains connection to the power supply was exposed, so I 3D printed a cover to keep things safe(r).
The next step is to start assembling the Y axis, I’m awaiting some aluminium to be machined by a professional (i.e. not me).