mini-makes: drybox spool rack

As you already know, I purchased a 3D printer. During my research, I learned that keeping your filament dry was important to ensure quality prints. While some types of filaments are more sensitive to moisture than others, all of them benefited from being dried out. As a result, 3D printing makers store their filament in vacuum sealed bags stuffed with silica gel and containers called dryboxes. There are many designs out there for dryboxes. Some designs primarily utilized silica gel and others (like the one I want to build) use active heating.

the design

The design for my drybox was inspired by this active heating drybox design by Rich of RepRap development fame. I did not use his part models because I didn’t use the same parts he did. I’ll talk about this more in the drybox post (I’ll post the link here when it’s up). But, I mimicked the design by having the spools roll on a rack that sat inside a container with a space for the hygrometer/therometer. The spool can be inserted and removed to change out spools and allows for a filament feed to the printer via a PTFE tube. After messing around in Fusion 360, I came up with the you see above, based on the dimensions I’m working with.

Like Rich, I designed the rack itself to be printed in two pieces that could be easily attached via tongue and groove joints. No need to glue anything together. Since it’s in the container, it shouldn’t have any problems staying together. The large rectangular space is for the hygrometer/thermometer unit I have. It’s meant to simply sit in the space and have sufficient support to stay put.

tongue and groove joint between the two pieces
opening for hygrometer/thermometer unit

Lastly, instead of using a metal rod, I chose to utilize some M3 screws I have. They will simply screw into the holes on the ends and sit in the notches of the rack, allowing the spindle to spin, if necessary. However, the spool insert itself is undersized to allow the spools to spin freely even if the insert itself does not also spin.

threaded hole for an M3 screw

the print

I printed these on my new Prusa i3 MK3S as my first real print after doing all the calibration. I printed it with the silver Prusa PLA that was included in my kit. Each piece of the rack took nearly 5 hours to print at 0.3mm layer height and 5% rectilinear infill. The spool insert took nearly 3 hours with the same settings. The results were what you see below.

the groove of the joint
the tongue of the joint

I’m happy with the quality of the print. I was having some trouble getting the skirt to stay put so I raised the bed temperature to 70C. This worked to keep the skirt in place but it turns out, raising the bed temperature above 60C when printing PLA often results in warping. Consequently, my first piece had some warping on the corners of one side (one corner much worse than the other).

Thankfully, the print still completed successfully without any other issues. The part coming off the bed like that definitely could have made the print head dislodge the part from the bed. Luckily, there was enough surface area in the part that it stayed nicely adhered. The warping doesn’t bother me since this is a purely functional part and it definitely works as intended. In the photo slideshow below, you can see the various parts of the drybox spool coming together. The hygrometer fits nicely in the opening, though I should have designed it better in hindsight because it falls out pretty easily. The heater slides perfectly into the groove though and works great. Now, all that’s left to do is add the parts and pop everything in the container as part of a drybox setup. More on that to come…

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