== Background ==
Our CNC machines are among the most popular tools in the space, but are not suitable for machining tough materials such as steel and cast iron and are limited in their ability to machine non-ferrous metals.
While our current Bridgeport milling machine can work with tough materials rather well, it is a manual machine which makes intricate parts tedious and sometimes impossible to produce.
For industry, aging electronics often makes older CNC machine tools obsolete before the mechanical parts wear out. These machines can be inexpensive and if mechanically sound, are good candidates for electronics retrofits. Replacing the CNC controllers provides the reliability and features of a modern machine at a small fraction of the cost of a new machine.
This proposal is to buy an older CNC milling machine in good condition and replace the majority of the electronics with modern parts.
This will likely include the motor drivers, rotary position encoders, and CNC controller. Depending on their condition, we will try to reuse the motor power supply, switches, spindle and axis motors.
=== Candidate Machine ===
We have located a Bridgeport Series I Interact machine that we believe would be a good machine for our shop. The seller is the company that sold us the DoAll bandsaw.
The CNC Bridgeport is very similar to our current manual Bridgeport with a few exceptions:
* DC servo motors controlling x & y axes and the quill.
* 34"x12" table (shorter and wider than our Bridgeport's table)
* ball screws instead of Acme screws for x, y, z axes.
* rigid ram - no nod & tilt provisions.
This is probably a mid to late '80s machine, newer than our manual machine.
Overall, the condition seems to be at least as good as our Bridgeport. The chrome ways have little wear and there are no marks on the table.
=== Software ===
LinuxCNC is the first choice for the control software on this machine. This is stable and has been used successfully in this application many times.
MachineKit, a recent fork of LinuxCNC, is not ready for servo based milling machines. Perhaps it will be useful for this project in the future.
There are several options for CAM, the software that converts a CAD design into instructions for the milling machine control.
We have Aspire, which many at PS1 already have used. As a maker space, we have free access to Inventor products. They have two products with CAM capabilities: InventorCAM and Fusion360.
=== Computer Hardware ===
CNC controller will run on an x86 machine. Older OptiPlex are reported to be good machines for LinuxCNC.
The CNC Milling Machine will be located near the Bridgeport milling machine, as they will be able to share tooling and this location is convenient to 3 phase power, which is required by the spindle motor.