if all goes well, there should be a photo of my machine attached to this posting --- in which case this will also make a bit more sense
The machine started out as nothing more than a framework for an X-Y plotter as I wanted to do a study on motion control. However, as time went on and I kept playing with the AVRs, I got more and more ideas of what this framework could be so it has morphed into a CNC machining center for PCB work. Some of you may also recall a posting by me a few months back of the machine in it's earlier stages.
There are currently ten AVRs on this machine handling various tasks. All of these are ultimately controlled by the CNC control software running on a Windows PC.
The machine isn't done yet, probably never will be as I keep adding new toys, bells, and whistles to it as it is proving to be a great learning platform.
A brief overview of it's features
Full operator panel with many switches to control the running of the CNC program and to provide manual operation.
8" x 10" table travels
4" of Z axis travel
Stepper driven through leadscrews - .0001" resolution
Current maximum traverse speed is 110 inches per minute
Variable speed spindle 1500 ~ 7000 RPM
Maximum tool diameter - .150"
Automatic tool changing - uses a variety of sensors and a sepperate hi-torque spindle drive motor for clamping / unclamping
38 Tool capacity tool magazine (not functioning just yet)
Temperature monitoring of all critical elements - reported on LCD
All machine side electronics are interfaced to the host PC using USB-Serial adapters (FTDI)
Probably many other features and things too, but those are the major features.
Switcher, yes and no about the bearing pads. They are not 8020 brand, but are of the same material UHMW. I decided to machine my own rather than use the off-the-shelf solution from 8020 as I needed "custom" sizes anyway.
As for how well they hold up - I suspect very well. I use the same system on my big wood router and there has been no signs of trouble anywhere after 2 years or so. The PCB material is certainly more abrasive than wood, but in order for it to cause wear the debris would have to get between the two surfaces. Even then, I suspect there isn't going to be much of a problem with wear - especially when considering how little use this type of machine is going to get.
Yes, that is the magazine that holds 38 tools. The chain is a hollow pin chain so it is very handy for holding the tools vertically. The stepper motor rotates the chain to bring the tools to the change position. There are two switches that detect tool positions (1) counts the teeth on a sprocket, (2) detects tool #1. From that point, all tool's positions are known by using a simple counter based on switch #1.
The whole chain assembly the rotates and swings in under the spindle for tool changing. Inside the headstock is a rather complex "Rube Goldberg" system for clamping and un-clamping the chuck which holds the tools in the spindle.