It’s been a while since I’ve posted anything, but I’m back with another pair of upgrades to my shapeoko 2 CNC router.
In this post I do a few modifications to my Z-axis and change out my spindle mount from a 3D printed version to a solid HDPE version.
SPINDLE BRACKET V2.0
A while back I started using a trim router from Harbor Freight as my spindle instead of a Dremel 300. To install that, I used a 3D printed bracket that clamped in the front and had an additional side hole for a vacuum tube. This first design had a couple problems.
First thing I noticed when zeroing my machine was that the side clamp for the vacuum tube would hit the front end plates of my machine. This meant I had to restrict the movement in this area such that the machine wouldn’t crash. Second issue was just the fact that it was 3D printed. I used a fairly solid infill to get decent strength, but 3D printed parts are just not as strong or rigid as solid plastic. Third issue, was that the mounting bracket clamped in the front. Due to my enclosure design, the extended area where the bolt goes to do do the actual clamping would hit my enclosure door if I did not restrict the movement. Again, this reduced my workable area. Fourth problem, though not entirely due to the mount design, was that I needed to use the universal mount blocks as spacers to avoid my router hitting the z-axis motor plates.
I addressed all four of these issues with my V2 spindle mount bracket. The rendered model is shown above. I moved the vacuum tube mount to the back to get it further out of the way, and also put the clamping holes for the spindle portion on the side instead of on the front. I also opted to make everything out of 1/2″ HDPE (sourced from amazon.com). I was also able to eliminate the need for spacers at the back, but that is mostly due to the z-axis clearance mod I did (see second half of post).
Material: 0.5″ HDPE
End Mill: 1/8″ Two Flute Square End Mill
Feed Rate: 35 in/min (x/y), 20 in/min (plunge)
Spindle Speed: “High” on trim router knob (~27000 RPM)
Depth of Cut per pass: 1/16″ per pass
Source Files (including .STEP of the trim router): http://www.thingiverse.com/thing:503637
MILLING VIDEOS AND PICTURES
**WARNING LOUD NOISES**
This was the first time I had ever machine HDPE, and wow do I enjoy it! It cuts very smoothly and quickly. The amount of chips reminds me a lot of when I machined ABS. This was also the first time I used hold down clamps instead of double sided tape to affix the stock to the waste board. I had to learn the hard way about using tabs, as my first attempt managed to get to the final cut out pass and then decide to chew up one of the edges of the clamp, making the part unusable.
All was not lost though! This was only the first cut into this piece of stock, and plenty of space was left. Another sort of good thing from this failure was that I learned that the material between the two circle cut outs was too small and made the bracket flex too much. I decided to double the thickness (at the closest point) from .125″ to .25″.
I added multiple tabs all over the place to keep everything in place this time. I still almost had a problem with the small cutout coming loose, but I managed to salvage the attempt. After the successful attempt, I rotated the stock 90 degrees to a clean area, and cut the second mount. I also cut out a jig to ensure that I got the correct hole spacing for holes where the bracket mounts to the Z-carriage. This jig was simple a pocket .3″ deep that the bracket fit into with holes already in the correct location. I used a hand drill to cut out the mounting holes.
I repeated this process twice to put the mounting holes in both brackets, then just free-hand drilled the holes for the clamping bolts.
Z-AXIS CLEARANCE MODIFICATION
Part of the reason the V1 bracket needed spacers was that the trim router would hit the Z-axis motor mount plate. This severely limited Z-axis range of motion so much so that spacers were needed. This limited y-axis movement (because of my enclosure) and reduced the rigidity of my machine since the spindle was cantilevered out farther.
There are a couple of solutions already out there for this problem. A belt driven Z screw, a re-designed aluminum mount plate, and trimming the existing motor mount plate. I chose to follow the last one, since it seemed the easiest option. I got the idea from this instructable: http://www.instructables.com/id/Shapeoko-2-Z-Axis-Fix/
It was convenient (and required) for me to do this the same time as installing the V2 mounting bracket. I basically followed the same steps as in the instructable. The first step was drilling a new 3mm hole in the motor mount plates.
The only tools I had on hand to do this metal working were a cordless drill, a drill index, a hacksaw and some thread cutting fluid. This made it difficult, but not impossible, to drill through these steel plates. What I ended up having to do was start with the smallest drill bit I had and work my way up to the correct size. Using the thread cutting fluid also helped make the drill steps easier. After drilling, I cleaned up the new holes with a countersink bit.
The next step was adding a notch to the motor spacer plate. The hole to start the notch began as a 1/4″ hole, again requiring starting at the smallest drill bit and working up. Next, I used a hacksaw with a metal blade to make the flat parts of the notch, and then a file to break the burrs and smooth out the shape.
After the spacer plate was finished, it was time to trim the motor mount plates. Using my 3D model of the shapeoko 2 assembly, I determined that I could trim the motor mount plates down to 1.625″ before it started to expose the flanged bearing and bellvue washer. I did this with only a hack saw and cutting fluid. It took forever!
The first one I cut, I started on one side then flipped. This lead to a slightly mismatched cut that I did my best to file down, but couldn’t fix entirely. The second one I did as one long cut from one side and it came out a much more smooth line! A quick pass with a file knocked down the sharp edges and rounded the corners out slightly.
After that all that was left was re-assembly of the Z-axis onto the machine. Below are several pictures around the machine after re-assembly.
BONUS Z-MAX ENDSTOP MOUNTING POSITION
A cool part about the trimming the Z motor mount plates was that the Z max endstop could be put in a new location. It was really just dumb luck that this worked, but a ziptie around the mounting screw for the Z-motor happens to be just the right place for a microswitch to live and be activated by the Z-carriage. This gives (almost) maximum Z-axis travel!
I am very pleased with the results of these two modifications. I believe I’ve increased my workable area by over an inch in the y-axis and the spindle should be much more rigid now. Doing some hand work metal was also surprisingly pleasing. It has been a while since I had done any metalworking. Maybe soon I’ll have to try cutting some aluminum on this thing!