Hello everyone,

I have built many projects in the past, and whenever I need a PCB milled I send it off, which is both expensive and has ~four week turnaround. I've also wanted to start working with metals, probably just aluminum.

I want to build my own CNC mill, I think a 12" by 18" working area would be enough for anything I want to do. I know my way around electronics, so building my own controller is not going to be an issue. I just had a few questions about the hardware aspect of the project:

Where can I read up on the subject more? Is there a wiki or a beginner sticky anywhere? My searches around here and CNCZone turned up nothing.

For a 12 by 18 working area, what torque of motors do you recommend? I'll be mostly milling PCBs, but I would also like to be able to mill aluminum and plastic.

EDIT: Also, what are the advantages of a moving gantry vs moving table?

Thanks!

Alex

Howdy xelapond,
I'll get the ball rolling and try to answer a couple questions for you. Sorry, I haven't milled any PCBs (MCBs?) so some of this is speculation.

As far as how much torque is required for milling circuit boards I would guess it would be pretty low since you'll only be cutting a few hundredths (maybe a tenth?) of an inch of copper with a very small end mill (the small ones cannot take much force). Because the small end mills will break so easily you're pretty limited in the cutting speed department. I imagine more torque would only let you overcome the friction of the screws/nuts more easily (so you could have faster rapids and faster acceleration/deceleration). The motors that come with the micRo are almost certainly sufficient.

A biggest advantage gantry routers/mills have over column mills is the footprint of the gantry router is only slightly larger than its work area. I tried to figure out a way to explain this using my words but I couldn't, if you need clarification on why this is the case maybe I (or someone else) can make up some pictures or something... Basically it boils down to the size required for the "saddle" on a column mill compared to the size of the rails and bearings on the gantry machine.

Yep, Hirudin is pretty much correct on everything. I'd like to elaborate though...

The Micro has plenty of torque for milling PCBs (or really, plastic or aluminum)- you will be limited by the mills you use and the spindle. That's the trade-off, the micRo is designed with a small spindle in mind (and small chuck). However, the next version will have a working speed in materials *not* limited by the spindle that is roughly 3-4 times that of our current release (switching from ~14ipm to around 45ipm). So, it should be pretty quick at milling PCBs.

Gantry advantages:
-generous work envelopes for the footprint.
-lighter, and use smaller motors/electronics verses comparable competing designs (translates into increases speed and/or accuracy- everything else being equal).
-usually are mechanically simpler, and therefor easier to setup, use, and maintain.

Gantry disadvantages:
-gantry is generally less rigid than other designs.
-requires regular checking and adjustment.
-generally carries lighter spindles/toolheads/tools than other designs of the same work envelope.

Hope that helps..