Low(est?) Cost Reproducible 3-axis CNC Mill
Introduction: Low(est?) Cost Reproducible 3-axis CNC Mill
As far as I know as of writing: this is the lowest cost 3-axis CNC mill you can build from available parts and repeatable instructions. It's small and I haven't bothered to even try cutting steel, but it's small and that reduces the "more stuff" cost too. I've been milling acrylic, hardboard/HDF, and copper-clad FR-n with encouraging results like smooth running bevel gears:
... and fine-pitch circuit board features:
Trials with aluminum look encouraging too.
This little mill uses three similar but different versions of "a cheap compact linear motion slide". That's a huge Instructable that does the heavy lifting for this project. As a precursor to publishing this 'ible, I put some time into at least trying to make the slide 'ible fairly complete. At least for now, this 'ible remains a little more sparse. Hopefully detail in the "cheap slide" 'ible will support the relatively lightweight presentation here. I also hope to put some more time into filling in the sparse corners of this 'ible anyhow.
However, the Main Things are in here:
* SVGs for the laser cut parts
* dimensions for a frame
* already referenced the 'ible re how to assemble a slide
* link to CAD
This 'ible intentionally focuses on building the machine. No instantly gratifying milled part will fall out at the end. CAM is harder than one 'ible. The point of this project is to lower the entry ticket cost to start learning CAM.
How low is "low cost"? Here's a bill of materials verified May 2021 for US delivery:
* $22.75 - 3x motors
* $5.26 - 10x bearings (1 extra)
* $9.78 - 9x rods
* $1.52 - 100x screws
* <$1.00 - ~9"x30" 1/8" hardboard
Total <$40.31 (+tax) if you have to buy everything. 215
A quarter of that for 6mm rod scavengable from dead printers of many kinds.
That pays for the 3-axis machine. Costs I don't feel bad about leaving out include:
* access to laser cutter - that's kind of a premise of the economic proposition here; commercial laser service costs would likely push this out of the niche it aims for
* rotary tool - because that's a generally useful tool that you either have or this is the excuse you've been waiting for to get one
* frame - I built the proof-of-concept, used in photos here, from a few poor scraps and drywall screws without a saw to cut anything
* controller - because that's portable between projects -- or ~$10+misc part scrounge (example) if you want to count it.
* time - yeah... don't ask. because I don't know. (actually, I can put one of these together pretty quickly now)
Please try building one for yourself and share how you fare!
Step 1: Check Out the Linear Slide Design
Yes, that's a handwheel. Gotta start somewhere!
The "slide" 'ible uses the basic example pictured to introduce how to build the mechanism shared by other variations on that theme. Although it may sound like extra work to do, I think it will most likely help you to actually build that example first. For emphasis: I strongly encourage you to build the first example there before building any of the axes for this little mill. In other words: I think planning on building four slides would be a good plan. You can reuse parts from the first if you don't want to keep it. If you build the example only as a warmup and don't expect to keep or use it for anything else, you can leave out the leadscrew/handwheel.
The second picture shows how the XY table is a stack of two simple slides with some variation around their edges.
Step 2: Laser Cut the Flat Parts
(here's an example of this 'ible glossing over stuff the "slide" 'ible covers more carefully - at least for now)
The exact shape of many of the parts depends on the expected thickness of material. This step has SVG files for 3.0mm & 3.5mm material thickness attached. If you have material over 3.5mm thick or would like a closer fit for your measured material, you can export your own vector file from the "cut lines (r.click->change config)" tab of the CAD model.
I've been working with 1/8" (3mm) single-sided hardboard/"masonite"/HDF, cut with the good side down.
Other materials 2.5mm-4mm thick may work. 215