Excessive moisture in the nylon filament will boil off as the filament goes through the hot end. This causes steam to push its way out along with the extruded line which will result in bubbles and poor layer to layer adhesion. Besides making the print unsightly, it will also make it more prone to delamination. Moisture control is definitely something to consider when printing in nylon and can also effect ABS and PLA when the humidity is extreme. In the summer months, I use the dry box for all my filaments and store those not in use in a giant seal-able bin.
Materials for Drybox:
- Air-tight tupperware-like box that is an appropriate shape for the spool (Mine was a rubbermade that I believe was made to accommodate cereal).
- 608 bearings X2
- body of a ball-point pen or dowel rod
- 1/4 in tubing push connector
- 1/4 in tubing ~ 1 meter
- 3D printed bearing holder
- foam rubber
- silica desiccant beads ( I purchased some of mine from protoparadigm.com)
The design for this is extremely simple and although I listed specific components, they certainly can be replaced with anything that will function in a similar fashion. The two most important considerations are that the box can be sealed, more or less airtight, and that the filament can be spooled out of the box with as little friction as possible.This second point is absolutely key.
- Print the bearing holders that will go over your bearings and provide a surface on to which you can glue your rubber grippers. I will attache the STL's for the holders I used for my 608 bearings, but if you have different bearings, its is literally one of the simplest shapes to generate in sketchup. Its just an extruded square with a circle pushed down into it.
- Place the bearings inside the bearing holders and glue the foam rubber grips to the flat side.
- Cut a length of tubing or dowel that will both fit inside the bearings inner ring snugly and be just long enough to press against the sides of container when the bearings are attached to each end. I used the body of a ball point pen.
- Drill a hole in the lid for the push connector and screw in push connector.
- Push in length of tubing* (I should note here that I ended up threading another bit of PTFE tubing, of the type that I had used for my bowden extruder, inside the regular PVC tubing in an effort to reduce the friction and it helped quite a bit. I didn't have the push connector that fit the PTFE tubing I already had, so that's why I went with the 1/4in. This isn't necessary if you have the correct connectors and could just go straight to your bowden tubing. Ultimately, you want a very slippery tubing that is only slightly larger than your filament so as to reduce the amount of air that can pass through the tube and into the drybox while not causing too much friction that the filament cannot feed properly).
- Add silica beads to the drybox to help absorb the moisture and keep the humidity in the box low. If you live in a moist climate or are frequently changing the spool, you may want to occasionally dry out your beads using a microwave or oven. They aren't toxic, but I would advocate using a container that would keep them from spilling into an area where your food might be prepared.
That's it, now you have a mobile drybox storage container and filament spool holder. This drastically improved the quality of my prints, especially with 618 and 645 nylon. Bridge seems to be a little more resistant to moisture absorption, but I still use a drybox with it.