As more and more experimental materials become available for low cost FDM machines, the need for optimized parameters and process control is becoming more strongly apparent. Many of the flexible and water-soluble materials are quite hygroscopic and incidence of jamming, print defects, and print failure can steadily increase over the lifespan of the spool if it is left in ambient atmosphere.
Here I will illustrate how to make a desiccating chamber for filament storage and dispensing that can hold two rolls of filament and a charge of desiccant. The goal of this design is to minimize aspects of material handling that contribute to print failure, chiefly friction and moisture content. All materials can be readily purchased from Mcmaster Carr or Amazon.
Step 1: Assemble the Materials
You will need the following from Amazon:
- 1 pack 608ZZ bearings, $8.17 each
- 1 re-usable desiccant 2-pack (contains two desiccant bricks), $14.99 each
You will need the following from Mcmaster (hyphenated quantities depend on number of spools):
- 1-2x push-to-connect tube fitting for 6mm OD tube, $4.72 each
- 1-2x 5ft length of Teflon tubing, 6mmOD, 4mm ID, $11.40 each
- 1x 10"x8.5"x9" airtight plastic box, $17.14 each
- 1x pack of 008 O-rings, $2.08 each
- 1x pack of 012 O-rings, $2.51 each
You will need to print the following pieces:
- 1-2x spool holder
- 1-2x BSPT nut (print at 100um layers to properly resolve the threads)
- 1x desiccant holder
- 8-12x M3x6mm button head cap screws
- 4x M8x16mm button head cap screws
- M8x1.25 tap
- M3x0.5 tap
- 3mm drill bit
- 10mm drill bit
- cordless drill
Depending on your configuration (one or two spools), the total comes to $58.50 or $74.62. Note also that segments of flexible filament can be used to replace the O-rings, though the seal may not be as tight.
Step 2: Assemble and Install the Spool Holder
The spool holder supports the filament on four bearings each secured with an M8 bolt. Tap the four M8 holes by passing the tap through the clearance hole. Tap the four M3 holes on the underside of the printed part, using a bottoming tap (if available) to finish. Insert each bearing into its slot and thread the M8x16mm bolt through, threading it into the tapped PLA hole on the other side of the bearing.
Next, flip the plastic bin and locate the spool holder on the bottom. Align the spool holder to a centimeter from the wall of the bin and use an awl or transfer punch to mark the holes. Insert the 008 O-rings into the channels surrounding each M3 hole and thread the four M3x6mm screws through the bottom of the bin and into the threaded holes. Make sure the O-rings are tight against the plastic wall to ensure a proper seal.
Repeat for the second spool if needed.
Step 3: Install Filament Tube Port
Set the spool into the spool holder and sight an appropriate exit path for the filament through the wall of the chamber. Gently drill a hole using the 10mm drill. Pass the push-to-connect fitting's threaded through the hole and into the chamber and slip the 012 O-ring over the plastic threads. With the arrows on the side pointing toward the fitting, thread the BSPT nut onto the fitting and tighten against the plastic wall of the chamber.
Step 4: Install the Desiccant Holder
Tap the four holes with an M3 tap and the desiccant holder in the chamber. The desiccant holder can be installed either on the bottom or the side wall of the chamber. I chose the sidewall for convenience. Transfer the hole locations with a sharpie and drill through the plastic wall. Locate the 008 O-rings around each hole and secure in place with M3x6mm screws. Slot in the two desiccant packs. Notice above the difference between a fresh pack (orange beads) and a spent pack (green beads). The packs can be easily recharged by microwaving for 1-2 minutes. I found that it was best to microwave for 30-40 seconds and then let the pack discharge water and cool off. Otherwise the steam can get hot enough to melt and distort the pack casing.
Step 5: Install Filament Tube and Print!
Insert a fresh spool of your material so that the filament exits at a tangent directly into the filament port. thread the filament into the teflon tube and then secure the tube in the port. I cut my tube to be about 34" long. Set the desiccating chamber near your printer such that the tube is has a gentle bend into the extruder (the sharper the bend, the more friction). Print away!