Pleasant Hardware

With a second working 3d printer in the house, I needed an extra filament spindle box. It was easy enough to build the first one for my Makerbot, so why not build a second, improved one?

The most wanted improvement was a window.

It turns out, that it’s not only nice looking but sometimes also important to see what’s going on inside the box. So I changed the design slightly to sport a window on the front.

Since it turned out, that the second disk above the filament spool on the turntable isn’t really needed (the spindle’s construction is self-supporting and the box’s top keeps the filament on the spindle), I recycled the spare plywood disk in the second filament box: It got promoted to be the turntable. (If you don’t have an extra plywood disk at hand, see here how to cut the disk out of a rectangular sheet of plywood with a Dremel).

Needing even less wooden parts (no front side, no plywood for the turntable), the remaining material was even cheaper to get. Including the sheet of transparent plastic (“Hobby Glass”, a sheet of 2mm transparent LDPE, 25x50cm), the whole stuff cost me less than 5€ (!).

Here’s the updated part list for the box:

Qty	Size (mm)	Material
2	310 x 310	MDF 10mm
2	310 x 120	MDF 10mm
1	290 x 120	MDF 10mm
1	280 x 280	Plywood 4mm
1	~ 300 x 130	Transparent plastic, acrylic, glass...

There were some requests for detailed drawings, so here you go:

(These drawings are also available as PDF. I added them to thing 3640 on thingiverse.com.)

The change in design is, that -instead of a front wall- there’s a groove for a sheet of transparent plastic (or acrylic, or glass, or whatever).

If you got a circular saw, the grooves are quite easy to make: Adjust the circular saw blade’s height to about half the MDF thickness (i.e. if you use 10mm MDF, adjust the saw to 5mm). Then use the saw’s stop to saw the groove 10mm from the front side of the bottom, top, left and right parts (I hope I’ve got the technical terms about right in English…).

If you don’t have a circular saw at hand (I don’t!), you might use a Dremel to cut the grooves. That’s slightly more work and probably not as exact, but it’s good enough:

After cutting the grooves and drilling all holes, the assembly of the box is quite easy. I used some glue for additional stability.

Then I did measure the final width of the front window (including the depth of the grooves).

Cutting the LDPE sheet was very easy: After slightly slitting the sheet with a box cutter, the sheet can be broken at a table’s edge. It’s like cutting glass, only with a knife and without the cullets.

Now I was able to mark the final height of the window:

Another LDPE-cut later, the box was almost finished:

I didn’t change the inner construction of the box. So all printed parts, ball bearings and rods are the same as in the first box.

I added one last improvement to the box’s turntable: Since the filament roll tends to loosen up a little bit on the turntable, it can happen that some loose filament “falls” from the turntable. That’s usually not a big problem, but it could lead to a turntable-jam.

To avoid that, I used some paper (160g/m²) to build kind of a “cake setting ring” around the turntable (maybe one could actually use a real cake setting ring for this?).

The paper ring catches the loose filament windings, but it doesn’t interfere with the unwinding mechanism itself.

Ok, that was fast. Thanks to “jstiltner” who wrote a comment on Thingiverse.com, I was able to solve my problem with the missing tubing to complete my filament spindle box.

jstitner on Thingiverse.com:

The HDPE tubing that is used on the makerbot looks the be the same as the “polyethylene” tubing used to connect refrigerators that have water dispensers.

I found a package with 10m LLDPE tubing in a store, selling refrigerators, washing mashines and stuff like that.

It’s a water tube (I guess some kind of spare part for a water dispenser) with an outer diameter of 6.5mm and an inner diameter of 4mm. Perfect!

Thanks again to jstiltner for the tip!

I already had drilled a hole for the filament into the side of the box:

Now that I had the actual tubing, I printed an object to attach it to the filament box:

Actually I printed two of them. On the one hand, the object prints better when printing two at the same time (the ABS has a hard time to cool down enough between layers when printing only one), on the other hand I used the second holder to mount a spring with about the same OD as the tubing on the inside of the box to flexibly guide the filament. Both parts are bolt down with one M4x20mm bolt:

The tubing (with the filament inside) then goes loosely to the top of the Makerbot. I use a guidance ring, I used before to keep the filament out of the timing belt on top of the Makerbot, to give the tubing some support on its way to the extruder:

I updated the Thingiverse.com thing with the printed parts and added the STL file for the tubing holder part.

After way too much disrupted prints because of filament jams, I decided to upgrade my Makerbot with a state of the art filament spindle.

I liked the the horizontal design of the “official” Makerbot filament spindle, so I decided to build my own filament spindle box based on (or rather inspired by) this open source design.

Since I don’t have access to a laser cutter, I re-designed the enclosure box for the filament spindle to be build from rectangular parts. It’s cheap and easy to buy custom pre-cut wood in almost any larger hardware store. I got the pre-cut wooden parts for less than 15€:

Here’s the part list for the wooden parts:

Qty	Size (mm)	Material
2	310 x 310	MDF 10mm
2	310 x 120	MDF 10mm
2	290 x 120	MDF 10mm
2	280 x 280	Plywood 4mm

I printed all smaller and more complex parts in ABS on the Makerbot. The STL files for these parts are published on Thingiverse: http://www.thingiverse.com/thing:3640

Finally the following non-printable parts are needed:

Qty	Part
1	M8 Threaded rod (approx. 135mm long)
2	608 Ball Bearing
2	M8 nut
2	M8 washer
4	M4 x 12mm bolts
6	M4 x 55mm bolts
16	M4 nuts
26	Chipboard screws (35mm)

The only non-printable parts (too big) in a non-rectangular shape are the two disks, holding the filament in place. I used my Dremel with its circle cut tool to cut the two square plywood sheets into (more or less) round shape. It was the first time I used the circle cutter and I learned a lot about how to not use it :) However, the disks are hidden inside the box anyway…

Building the box is straight forward: Pre-drill and countersink the holes for the chipboard screws (the hole for the axle in the center is a stepped bore 8/13mm. More on this later)…

… and assemble the box, using some glue and a bunch of chipboard screws:

(Well, I guess 3 screws per edge would have been more than enough…)

The axle inside the box is stationary. The lower M8 nut is counter-sunk on the “outside” of the box (that’s why the center hole is a stepped bore). Inside the box, the axle holds a sandwic containing a M8 washer, a 608 ball bearing, another washer and finally a second nut:

The 608 ball bearing holds the bottom plywood disk (and therefor the filament roll). I know, the ball bearing isn’t designed to hold load in axial direction. But the  approx. 2.5 kg shouldn’t be any problem for a 608 ball bearing (even in axial direction) and the spool turns rather slowly. According to wikipedia, the maximum axial load of a radial ball bearing is usually between 25 and 50% of it’s maximum radial load. And a 608 ball bearing is able to handle a static radial load of about 1400N (!)

The axle is cut to length, so the upper end should end “inside” the top cover (approx. 5mm):

The top cover plate also gets a center bore (8mm diam.), but only half way thru.

That way, the top cover plate hold the stationary axle centered.

To attach the bottom plywood disk to the 608 bearing, I printed an ABS bearing holder part:

This part is bolt to the plywood disk with four M4 bolts.

The 608 ball bearing should fit snugly:

(The 608 ball bearing in the photo above was only inserted to check its fit. Later, the ball bearing is already mounted on the axle as described above and the plywood disk (with the ABS bearing holder bolt to its lower side) is pressed onto the ball bearing on the axle.)

… back to the headline

Initially I planned to use the chipboard screws only for building the wooden box. But when designing the printable parts, I ran into an old problem: how to connect the printed parts with the non-printed parts? In case of the lower bearing holder it’s no problem to use bolts and nuts to attach it to the plywood disk. But in case of the inner distance parts it’s not that easy. Using the T-slot technique (normally used with laser cut assemblies) isn’t that easy with printed ABS parts. The T-slots likely aren’t printed with enough detail and ABS is probably too soft to hold the pressure from the tiny M3 or M4 nuts.

Finally it struck me: Why not simply use chipboard screws and screw them directly into the ABS? After all, when disassembling industrial plastic objects, you almost never find bolts and nuts but self-tapping screws. So why not use the same technique with printed objects? The design gets even simpler: just print the parts with “pre-drilled” bores for the screws and you’re ready to go. No captive nuts. No fiddling around.

Granted, some nice, black socket cap bolts with self-locking nylock nuts look usually much more elegant. Also parts you want to disassemble frequently are much better off with some kind of nut & bolt connection.

But all other connections are great candidates for “direct screwing” with chipboard screws. Chipboard screws are available in all kind of sizes and they are cheap!

That said, I designed the inner distance parts with a “pre-drilled”  bore for a 35mm chipboard screw, holding it on the plywood disk:

To hold the upper end of the inner distance parts in place, I designed a second ball bearing holder:

This second holder contains slots for six M4 bolts, used as spokes:

Since I put the Makerbot on top of the closed filament spindle box, there’s no need for any additional closing mechanism.

Things to do

As mentioned above, I still need to design and print some kind of snap-in mechanism for the upper plywood disk.

A much bigger problem is, that I still don’t have any tubing to guide the filament from the box’s outlet (a hole on the right side of the box) to the extruder. It’s harder than I thought to get hands on a small amounts of plastic tubing (at least around here in my hometown). In order to minimize friction, I guess the best material would be PTFE. So far I found PTFE tubing only in online stores in large quantities of 25 or 50m (which is quite expensive, especially since I need only 1 or 2m).

If someone knows a good, cheap source for PTFE tubing in small quantities (preferably in Germany), please let me know.