After having joined the Milwaukee Makerspace , the need arose for a set of spools and a rack that would allow our Makerbot 3D printer to pull ABS plastic filament. Previously, we were loosely coiling it and using painters' tape to hold it together, peeling it off as we went. Not only was it a mess having various coils and loops of ABS plastic laying all over the table, at one point a maker had his print interrupted due to a kink in the filament.
I've covered building the spools in another Instructable, so here I will focus on the rack that I designed for tabletop use.
-2 10"x24"x1/2" boards (I used some scrap plywood lying around; I can't help but think that this would've looked better in oak)
-1 10"x22"x1/2" board (to act as a shelf)
-1 2"x22"x1/2" piece of lumber (I used pine; this is a horizontal strut for stability)
-1 1"x28" wooden dowel (we had an old broom handle laying around that cleaned up nicely)
-Bandsaw (if you have a thin enough blade, you might be able to get away with using a handheld scroll saw)
-Belt Sander (you could certainly hand sand these, if you have no life and eternal patience)
-90 degree angle clamps (these are a lifesaver. I used the makerspace's, but I now plan on getting my own)
-Powerdrill, drill bits, screws.
-Compass (the circle-drawing kind, not the superstitious "magnetic" ones)
-A 1 1/4" hole-saw (not essential...it just made things a little easier)
Step 1: Layout and Planning
I'm a big believer in not sacrificing form for function. My goal is that, once you know something will work, make it look good.
To that end I decided that I wanted to taper the top of the rack to a rounded curve. This was very easy to do.
First, I decided on the height that the middle shelf would need to be at. Since my spools were 8" in diameter, it was easiest to just divide the sides in half, giving me 12" on either side of the shelf (minus 1/2" for the shelf's thickness).
I drew my line midway to represent where the shelf would go, then split the sides vertically, right down the middle. I bisected the top half of the side and drew a circle with my compass to represent the spot where the dowel would rest.
For the top point, I used the middle, vertical line and decided on a 2" diameter curve, easily achieved with a compass. I connected the edges of the curve to the ends of the middle shelf line, thus giving me a guide for my taper.
I wanted a slot so that you could slide the fully loaded dowel into place without having to remove the spools first.
I pretty much just eyeballed it. I used a French Curve to keep the slot the same shape throughout.
Important note: Make sure that, since the dowel is 1" in diameter, the end of the slot in the side is big enough to accommodate this. In my first sketch, I just drew the lines from the edges of the middle circle right to the outside and found that as it curves, the slot narrows significantly.
The pencil didn't show up too well in the photograph, so I've used Inkscape to sketch the lines in.
Step 2: Rough-Sawing and Hole-Cutting
Here, I simply cut the taper with band saw. Remember that you're going to need to do some touch-up work, so don't fret if you're outside the lines a little.
After the taper was cut, I took a hole-saw and drill press and cut the middle hole for the dowel. This gave me a target to work towards.
Back at the band saw, I cut the curve for the dowel to slide into.
When all was said and done, I hand-sanded the curve and then sanded the edges of each piece on a belt sander.
In the pic, you can see that I have also cut and sanded the shelf. Everything is ready for assembly.
Step 3: Angle Clamps FTW
Using angle clamps, I was able to place the shelf exactly before drilling and screwing.
(I should have used a dado groove here to hold the shelf in place, but I wasn't sure how the plywood would respond to that.)
I ended up dropping the shelf down about a half-inch for aesthetic reasons. I also traced a line that followed the shelf so I would have a guide for where to put the screws.
Here, I liberally applied wood glue, then clamped the shelf and one of the sides in place. I found it necessary to predrill the holes for the screws to keep the plywood from splitting.
It seemed that the easiest way to drill and screw the first side was to lay the entire thing down and use the table as a guide to keep the drill level. One screw in the front, one in back, then one in the middle seemed to give it some stability. You can see this in the second picture.
Now repeat the process for the second side.
The entire thing seemed a bit wobbly to me, so as an after thought I clamped a thin piece of pine in place about 5" up the back of the shelf, predrilled it, and screwed it into place. This seemed to work well, though I forgot to take pictures. It was the same process that I used for the shelf, however.
Step 4: The Final Product
So this is the final product, spools and all. I should note that neither the spools nor the rack are designed for heavy loads. The ABS plastic that the Makerbot uses is light and springy and the feed rate is rather slow. I would consider different techniques for all of this if you're going to use something like this for heavy wire.