Online filament dryer

Warning !

Build / use at your own risks, fire hazard ! do not leave unattended !

Intro

I wanted a cheap, practical solution for drying my filament. This design brings the following:

• can be used while printing
• easy setup: no need to remove the filament from the printer
• built from simple, inexpensive hardware
• nice look

With custom dimensions, it should be compatible with any vertical spool holder standing on a desk, provided it's not in PLA. I'm using the triangular spool holder that I designed a while ago.

General building guidelines are exposed below, but I didn't detailed every aspect, this is more intended as an overview in case someone wants to make something similar, perhaps with different dimensions and hardware choices.

Required hardware

• fiberboard rectangles of the appropriate dimensions
• thermostat (W3230 or similar)
• two PTC heaters 35x21mm, 220V / 150°C
• 40x40 heatsinks, 40x40 aluminum plates and screws
• 12V fan(s) 40, 50, or 60mm
• 12V power supply (450mA)
• switch
• power connector (C8)
• cyanoacrylate glue
• a straight 30cm length of 1.5mm^2 copper wire
• 2A fuse with holder

Building the box

The box is made of five fiberboard rectangles held together by 3d printed ABS parts:

• angle (print in vase mode, 8 times) : vertical edges
• top (print twice)
• bottom, bottom_right (print bottom_right a second time mirrored)
• link (print 4 times in vase mode) to connect pairs of vertical edges
• bottom_link (print 8 times in vase mode) to connect vertical edges to top and bottom

The provided STL files are for 250x250x132.6mm outer dimensions, which can be customized in the OpenSCAD file. The corresponding (computed) fiberboard dimensions are: 240.8x123.4, 123.4x248.4, and 240.8x248.4, small adjustments may be needed for a perfect fit.

Everything is glued, except the top, for accessibility.

I later added 3 fiberboard parts to make some kind of thermal insulation around the thermostat and power supply. This keeps them at 60°C when the inside is at heated 80°C. The picture should give the idea.

A piece of copper wire is glued inside the notch part, in order to sustain the wear due to the filament friction.

Inside

This thing is an electric heater which runs continuously near flammable materials, so fire hazard should not be overlooked. The PTC heaters by themselves should not be able to reach a risky temperature, but a short circuit or dangerous failure can happen, for example in electronic boards, especially given the surrounding temperature. So, ensure electrical insulation of the components with cases, sheath, and don't forget the fuse.

The heating is done by two 150°C PTC heaters, attached to 4cm square heatsinks. I started with only one heater, but this was not enough to reach higher temperatures.

I currently have a 60x15 fan blowing more or less towards the heatsinks. I might try a different configuration to improve heat dissipation (so that I can get more power from the PTCs).

I printed small TPU parts to “suspend” the fan and avoid noisy vibrations. Some other (ABS) printed parts are used for PSU board, switch, and power connector casing and for holding the heaters, temperature sensor, and wires.

Conclusion

I have successfully used this dry box with several spools, it works as expected and makes a big difference. The pictures show the same E3DBuggy printed in PETG with the same printer, gcode, and spool, with the only difference being a 24H stay in the dryer in between.

I measured a peak power of around 250W (during cold start) and a minimum power of 68W during continuous heating, for a maximum temperature of 83°C, with 20°C room temperature.

For Nylon, an even higher temperature would be desirable, so more powerful heaters, fans, or larger heat sinks could help.

Let me know if you plan to use this design, or if you have any questions or comments !