Once the fixed back plate (3/4″ aluminum) and the movable front plate (1″ aluminum) were machined it was assembly time. Here you can see the parts laid out and ready to go. In the upper-right you’ll see two white brackets to mount the stepper motor and tension the belt. These were 3-d printed with the mindset that I’ll mill aluminum ones when the machine is up and running. I found out about the option to put brass screw inserts in the 3-d print too late, but it looks like an awesome procedure and is something I’d do in the future.
Assembly was pretty straight forward. I did have a little binding on the lead screw and had to shim it out a little bit using some folded aluminum foil. Shim stock isn’t something I have on hand!
And some additional photos of the assembly and mounting to the y-axis.
Once it was on the machine I could locate the z-axis homing switch. I used a fairly inexpensive magnetic sensor from amazon. I mounted the sensor in the back plate, and then drilled/tapped and threaded a hex-cap bolt in the movable front plate. This bolt triggers the magnetic sensor when the z-axis is in the full-up position.
Pro-Tip : Just buy a z-axis. It’s likely not worth the hassle, unless you don’t value your time. Or if this really and truly a hobby and you enjoy doing and redoing things.
That said I built a z-axis! I bought a bundle of parts off ebay and used that as a ground floor for measuring and designing. Having parts on hand provided a good starting point for scale and feasibility in Fusion 360.
From there it was quite a few iterations to draw up what would become the axis. During this process I learned a LOT about fusion, as I wanted all the movements to work so I could watch for clearance issues etc. Saunders Machine Works’ youTube channel was a huge help. The final drawing (looks like 42 edits) looked something like this.
Mounting the stepper that way was a little more work, but it keeps it from sticking out the top, and counter-balances the weight a little bit. Here is a zip file with the fusion model if you want to use it.
I started doing the manufacturing of the backplate the manual way. Lobbed off a piece of 3/4″ aluminum stock and started drilling, tapping, and cutting. Fusion allows you to print out 1:1 sized prints which worked super well. I just sprayed on contact adhesive and glued the template to the stock. It was a lot of holes, and a lot of tapping.
The studious observer may notice the two pockets where the bearing-blocks for the lead screw attach. Those I didn’t get done in my garage. At the high school they have a old cnc Haas mill that we have access to for working on the robotics team. They were kind enough to let me run the pocket operations I needed on that mill. Thank goodness! It would have been nice to mill the whole piece there, including the drill holes but I didn’t want to overstay my welcome.
How can we make this project harder and take longer? Oh yes, lets collect new skills in a very round-about path to the destination. In this case I wanted to learn how to TIG weld. I could haphazardly do MIG welding but wanted to learn TIG. This was primarily as aluminum is a key working material for the high school robotics team and being able to weld it would likely come in handy. With a welder in hand I knocked together a frame to hold the new CNC gantry as well as a few drawers.
One of the things that’s not super obvious is behind the drawers you’ll see a ‘divider’ that leaves about a foot of space in the back. That’s where the electronics will eventually go.
I have had this 2×4 cnc machine for 4 years now, and have outgrown it. Made of MDF with aluminum rails and skate bearings it won’t go down in history as a super sturdy machine. That said it served me well and together we made some awesome things. I have been volunteering at the high school robotics team, and having a machine that can mill aluminum with a reasonable amount of accuracy was my design goal.
Doing the slow troll on craiglist and facebook marketplace I came across this guy. Stout steel frame, and nice linear bearings. The z-axis on it was some sort of ink sprayer – not sure what exactly it’s previous life was but good bones for my build. Now I just needed a table, z-axis, electronics, mill.. the little things.
One thing that was interesting/concerning was this used belts instead of ball/lead screws to move the x/y axis. There is an included gearbox with a 2.5:1 ratio off the stepper motors, and my concern was if I could get and maintain the accuracy needed. Overall these rail systems were very well built, and even the belt-tightening mechanism was well done.
My dad spent a lifetime as an automotive mechanic, specializing in transmission repair. He recently retired and I spend a few days helping him clean out his shop as he sold the building. I took a few moments to take photos of his toolbox, as the years of wear and showcase of daily-driver tools was pretty cool.