Her Name is Mildred

Having completed my workbench, it was time to shave the next yak. I needed a computer controlled wood cutter. I thought they were called CNC mills, so I decided that, whichever one I got, I would name it Mildred. Milby for short. Turns out CNC mills are similar, but for cutting metal. What I needed is called a CNC router. In fact, it’s literally a machine that you plop a regular old DeWalt handheld router into. Probably should have named it Rudy the Router, but I figured it’d be cruel to change even a hypothetical being’s name out from under it, so Mildred it is.

Picking a CNC router to buy was an easy process, and I definitely did not spend countless hours comparing the pros and cons of every single model available. I definitely did not watch every youtube video or read every reddit thread entitled “Which CNC Router is right for you.” It ended up coming down to two popular models, the X-Carve or the Shapeoko3. I ended up picking the Shapeoko3 because I heard that it was more rigid, and also because I thought it looked cooler? I have no idea if the Shapeoko3 is the best choice out there, but so far I love it, it was (relatively) easy to assemble, super solid, surprisingly accurate, and a lot of fun to use.

Shapeoko3

I actually ordered my Shapeoko3 ahead of time, and it arrived halfway through my workbench build. In an extremely impressive show of self restraint, I did not open the box until the workbench was done.

The box was pretty heavy. BMO is wondering what I’ve gotten myself into, but he’s promised to help out when he has time.

As with any project in which you assemble things, the first step is Knolling. Only I didn’t know that that’s what it’s called, until @sluicing pointed it out. Turns out I’m a life long knoll-er. Check it out on wikipedia, it’s a thing.

Knolling is when you arrange all the parts at right angles, and group like items together

The bulk of what’s in the box is the large MDF base board, and some heavy aluminum rails. I opted for the XL model, which is much bigger than the default size but still half the size of the XXL. I think someday I may upgrade to the XXL, which can be done with an extension kit.

There’s also some electronics, the router itself, and the stepper motors.

First I attached the base board to the main frame. Then the Z axis plate, which holds the router and can move up and down. Then put together the X axis rail and mount the Z plate onto it. The Z plate can move left and right along the X rail. The X rail attaches to the two (smaller) Y rails for forward / back motion.

At this point, the main frame is complete, and feels very solid and slides around with a very satisfying smoothness.

Dremel’s slogan is “Big on Detail” but I’d like to propose a new one

I also had to remove one of the factory installed screws on the Z-Plate, so that an optional part (a homing switch) could be added. The factory installed screws were essentially glued in place with Loctite, and I ended up stripping the screw. After a few hours of trying to use vice grips, a slightly larger alan wrench, and lots of non-verbal muttering, I realized I was stuck. I’d come this far, taken classes, built a workbench, assembled this frame, and a single stripped screw was going to be the end of it. I emailed the folks at carbide3d (makers of the Shapeoko3) and they recommended I try heating up the screw with a lighter, to help undo the Loctite. It was a pretty hilarious prank in retrospect, and I bought it wholesale, and was left scratching my head and with a still-stuck screw, now slightly blackened.

Googling around for ways to deal with a stuck and stripped screw, I discovered the nuclear option. Use a Dremel to cut a big old groove into the screw, and then use a regular flathead screwdriver. You basically convert the alan screw to a flat head screw. Luckily, I had already bought myself a Dremel. It just seemed like something you have to have around for situations like this. It worked.

Next came attaching the stepper motors, and lots and lots of wiring. With those in place, it was time to connect dear Mildred to my laptop and see if a bit of lighting could bring her to life.

The Hello World equivalent of CNC routing is to zip-tie a sharpie to the router and draw something. A CNC router’s feature set is pretty much a direct superset of everything a pen plotter can do, so I mounted a sharpie and ran the test program which drew the carbide3d logo on a piece of paper. It went pretty well. Feeling confident, I decided to have the router draw my handle onto the name tag that came with kit.

It uh, it went about as well as I hope you’ve come to expect from me. It didn’t work. That’s ok. You know what, why don’t you just take a look at some of my roommate Chandler Abraham’s pen plotter work. And then just imagine Mildred the incorrectly named CNC router doing something similar.

Mildred… This could be us but you playin

What happened was I put the name tag on some cardboard, which was bowed slightly, and so the surface wasn’t perfectly flat. Which meant when I zeroed the pen to the left side, by the time it got to the right it was slightly above the surface of the tag, and just drawing in the air.

Lesson learned. Good work holding and flat surfaces are important. More on that to come in future posts. Oh? You thought I was ready to build my clock now that Mildred is up and running? There’s that sense of humor of yours again. I love it, really I, do.

But don’t be silly, there’s more yaks to shave, and work holding is only one of them! I digress.

BMO was kind enough to finish the name tag for me by hand, and expertly affix it to the center of the X rail as well.

Once again made confident by my recent failures, the only reasonable thing to do was to charge ahead blindly and try again, but something even more difficult this time. It was time to engrave some wood.

V-Bits are used for engraving “V-Carve” toolpaths. The router can engrave lines of varying width simply by making deeper or shallower cuts.

I grabbed a scrap piece of 2x4, threw some super strong double sided tape on it, and stuck it onto the router’s base board. I chucked a 60 degree V-Bit into the router, created an engraving toolpath in the software, and gave it a go.

Once again, the surface of the wood was not perpendicular to the router, so the cuts are shallower on the left, and deeper on the right. Both pen plotting and shallow engraving like this are very sensitive to that. Deeper cuts, like those used to cut thick 2D parts, aren’t really affected by this. But don’t worry, in a future post I’ll continue yak shaving by delving into surface planing and jointing with Mildred. Stay tuned.

Sorry, this was the best I could stabilize this. I did get better at making these videos later.

And look at that. It sort of worked.

Next up, I wanted to try actually cutting a part (instead of engraving). I decided to skip right ahead to a functional part, a basic edge to edge joint, which would give me an opportunity to design a profile cut, and also give me a sense for how accurate this thing was out of the box. I headed over to Fusion360, and sketched up something like this:

And then I decided to just cut a tiny part of the above.

The picture doesn’t really do it justice. It fit together perfectly. I didn’t design any wiggle room in, so I actually had to use a hammer to get it together, and I was unable to separate the two pieces afterward.

Thus Mildred was born, tested, and ready for action. I was one step closer to building my damn clock.