CNC mill phase 2: CAD
Tuesday, 23 August 2011
With the system map complete and the major components sourced I set about the mechanical design of the enclosures. I originally intended to design and build a custom enclosure for the computer and drivers, out of brushed aluminum/stainless, etc. but came to my senses. Sometimes you have to recognize when to go all out, and when to just get it done. So in that spirit I found a suitable electrical pull box from Automation Direct and probably saved myself a month of fabrication and finishing time. That’s not to say this box will work as-is off the shelf, so there’s still plenty of opportunities to fabricate and modify.
This is the main two-part enclosure after the extensive modification required to mount the PC and monitor, keyboard and PCBs. Since the enclosure is steel I opted to weld as much of it together as possible in the interest of simplicity. Most of the front panel is cut away for the monitor and keyboard, so the ribs that are welded in also add rigidity. A continuous steel hinge is welded to the front panel and then bolted to the enclosure to join them together.
The touchscreen monitor will mount to the ribs on three sides, allowing the PC components to attach to the VESA mounting holes on the monitor through a simple, flat aluminum bracket. The keyboard will be sandwiched against the inside of the front panel with a flat steel plate.
The interface elements on the right side of the front panel are connected to a large PC board that includes the Arduino and charge pump circuitry. A smaller board isolates the relays, most of which will be switching AC power.
The original concept was to pack everything into the controller box so it would be a standalone assembly, but I came to understand the risk of packaging higher DC voltage components (like stepper drivers) into the same box as sensitive logic-level components (like a PC). So the motor drivers and their power supply moved into the base of the milling machine, mounted to a welded steel assembly that will mount into the base through an opening cut through the back. The pink datum planes in the screenshots represent the interior space available in the upper half of the machine’s base, which is pretty much consumed by the electronics.
Next up is the PCB design for the interface board in the controller box…