Saturday, June 26, 2010

PCB isolation routing - attempt 2

Much better results this time. Milled-and-drilled with excellent results. I decided to switch from my 1/4" router to a Dremel tool - this required a new mounting bracket. Naturally, I used the router table to make the new parts. The process is starting to get easier. I routed two brackets from 3/4" MDF and glued together.

I carefully added the mounting holes so I can easily switch from the router mount to the Dremel mount with only 4 bolts. Works great. Another benefit is the Dremel is considerably less noisy than the router, and the Dremel runs cool the whole time. Running a homeowner-quality router for an hour gets scary - you can smell the varnish on the motor windings getting hot.

Added a saw kerf and a bolt to "pinch" the Dremel into place. Like a rock.

Here's the Dremel mounted.

I secured special 1/8" milling bits from DrewTronics. It was the 1/8" shaft that made the Dremel the easy choice. I ordered 30, 45 and 60 degree bits with the idea to play with them all over time. I had to throw 'em under the microscope - here is a 45 degree bit at 20x magnification.

Routing went perfectly. Tooling still a bit to deep. Milling time was shortened considerably by using the gcode optimizer.

After routing, I decided to try drilling too. Snapped the first bit after drilling the 4th hole. Checking the setting of the gcode converter - I found one setting at zero inches - this caused the tool to move to the "home" position for a tool change, but didn't lift the drill out of the PCB first! Changed the number to one inch, and it worked fine, returned the router to the 0,0 position, raised an inch for easy drill changes.

Drill bits are from Jameco and seemed to do an excellent job.

Here's some of the traces at 20x magnification. I did nothing but scrub the board a little with a Scotch scrubbing sponge - no abrasives, no sanding. Was able to get a trace between two 0.100 inch IC pads.

Next I'll ring it with a volt meter, and if all is good, actually build the circuit.

1 comment:

  1. Do you happen to remember which DrewTronic bit you used and what your settings were for depth and feed rate?