Around a year ago, when the ShapeOko 3 was first being announced I
started getting the idea that it would be really awesome to just buy the
rails and build my own machine. It just sounded like the kind of
challenge that I was looking for. Unfortunately, it quickly became
apparent that the ShapeOko 3's rails weren't going to be available by
themselves. This realization of course didn't deter me too much, I
simply started looking at ways that I could mimic the performance of the
ShapeOko 3's non-general-purpose linear motion rail.
Of course, as I'm writing this there are two very simple paths to get rails for the build I was initially envisioning. The first is by getting a Shapeoko 3 xxl expansion pack. Although, at $700, it's a bit on the pricey side. The second option is to get some MegaRail 80 shipped over from the UK. Unfortunately, neither of these options were available when I started procuring materials for this build.
Around September 2015 I decided that I'd thought about the build long enough, and if I was going to build something I should probably start doing it. With that decision made, I went about procuring all of the raw materials needed for the build. For the rails I settled on using some 1/4" thick extruded aluminum rectangle that measured 4" x 2" x 36". I really felt like I was gambling with this choice, but I got lucky and the extrusions ended up usable for the project. Now, there are several options for rail that I could've used.
One of course, was Open Build’s OpenRail. The second option would be to use hardened steel rail which is available from numerous vendors. Finally, the third option that I considered was hard coat anodized aluminum rail.
I sort of ruled out OpenRail because I felt that Delrin V-wheels might not be able to support the weight of this machine, and even if they could they'd end up being the weak link for this build. I had almost come to grips with the fact that I was going to have to spend a ton of money for steel rail. Then kind of out of the blue I discovered a guy on eBay selling hard coat aluminum V-rail. It was so much cheaper that I had to take a look and figure out if I could run steel V-wheels on it. It was kind of hard to find any solid proof that the rail would even work.
Ultimately, three things swayed me to try the hard coat rail. First, was obviously the price compared to harden steel rail. The second was that I had found some hardened steel rail that matched the hard coat aluminum rail's dimensions. This means that if the hard coat rail doesn't hold up but the machine ends up working great I at least have a relatively simple option available to fix a bad decision. The third thing that persuaded me to go with hard coat rail was a post by Bart Dring in which he answered a question about hard coat maker slide.
From reading this, I'm reasonably confident that the rail will last long enough to prove the machine a success or failure and save a bit of money right now anyways. However, I do believe there is a strong likelihood that the hard coat rail will eventually wear out. Although, it sounds like keeping the rail clear of debris will potentially aid in maintaining the rail for a longer period.
After spending most of a month sourcing and purchasing components for the build, I figured that I would be able to get the whole thing built by the end of November 2015. Boy was I wrong! Turns out that when you don't have the experience or the equipment for such a project, things take a lot longer than you think they might. Then add in the uncontrollable factors of life and work, and I find myself nearing the middle of April with less done than I thought I'd have at the end of October last year.
Early on, I identified that the linear motion rails would need to be built first. Mostly because they are the foundation that the rest of the machine is built around. So, with that, let's talk about the rails.
3X 1/4" thick 6063 extruded aluminum rectangle 4" x 2" x 36"
6X 36" hardcoat anodized aluminum V Groove rail.
1X 1/4" thick 6061 aluminum angle 1" x 1" x 24"
22x M5 8mm Low Profile Screws Per assembled rail.
8X 1/4"-20 Screws Per assembled rail.
I started by first stretching a large piece of fine grit sandpaper across the length of my table saw. I used this set up to clean up any of the minor imperfections and scratches on the three aluminum extrusions.
Then, I took the 1" x 1" aluminum angle and cut 12 ~ 1.5" long pieces to go into the ends of the large extrusions. I attempted to mill them down, so the pieces just barely fit into the ends. After getting all of the angle pieces made, I put the large extrusions into a vice on my small bench master mill. It wasn't the perfect scenario, but I managed to drill pilot holes through the large extrusions and angle aluminum. This allowed me to drill and tap the angle and then attach it firmly to the extrusion.
After both pieces of angle aluminum were mounted into one side of the extrusion I flipped it all over on its side and used a very long end mill to mill all the components flush and hopefully square.
I milled out a cast acrylic template that could fit on to the ends of the extrusions, and allowed me to use a center punch to, hopefully, consistently mark where to drill the four mounting screw holes. The template worked pretty darn good and it ended up not taking too long to drill and tap the eight screw holes on the ends of each extrusion.
Then it was back to the mill to drill, tap and mount the V-rail to the extrusions. I don't quite know what I was thinking with the first extrusion, but for some reason I thought it was a good idea to start placing M5 screws a half inch in and place screws every 2 inches. This, of course, was idiotic for two reasons. One, screws placed every 2 inches is overkill. Two, the math doesn't work out. This was a brain fart pure and simple on my part. I did a little bit better job on the other two extrusions by placing 11 screws 3.5 inches apart starting and ending a half-inch from the ends.
Wow, when I write it all down like this I have to wonder how in the world it took me so long to get these things made. Oh well, they’re done, and while they don't look the best I do believe they are reasonably accurate.
Oh, and Here's a little video I made about the rails.