Friday, November 25, 2016

Yes, That Is a Jerky Maker in Our 3D Printing Lab

And, no, we’re not using it to turn our Thanksgiving leftovers into turkey jerky. The food dehyrdrator is part of our low-tech solution to a common 3D printing problem – brittle filament.

If you’ve been working with FDM (fused deposition modeling) printers, you’ve probably discovered to your dismay that filament absorbs moisture from the air. If you leave it exposed for too long, the plastic breaks easily – leading to print failures, rough surfaces and even clogged print heads. 

It seems counterintuitive that water can make a material less flexible; especially plastic, which we think of as being moisture-resistant. But most 3D printing filaments are made with some type of polymer. Water molecules break polymer chains, weakening the material’s structure. has a good explanation of the science behind this process, called hydrolysis

The type of filament we use most at our 3D ThinkLink class sites and in our lab is PLA (Polylactic Acid) a biodegradable polymer made from plants such as corn. It’s safer than another commonly used type of filament, ABS (Acrylonitrile Butadiene Styrene), because it doesn’t emit potentially dangerous fumes when it melts in the 3D printer’s hot end. PLA absorbs water faster than ABS. Moisture is an even bigger problem with two other kinds of filament we sometimes use – nylon and 3D Systems’ Infinity water-soluble support material.

Tiny pockets of water will turn to steam when the filament is extruded through the printer’s hot end, leaving pits in what should be smooth surfaces of printed objects. Moisture can also make filament swell up, causing a clog that could ruin your machine’s print head. 

We’ve learned through trial and error that it’s not enough to store filament in an airtight container, although that’s also part of the solution. When you encounter a moisture-related problem, you have to actively dry the filament. That’s where our jerky maker comes in.

3D printing enthusiasts have devised all sorts of methods for drying filament. We’ve found that using a home food dehydrator is a safe, simple, affordable way to make troublesome filament usable again.

We use a Nesco FD-61, which is widely available for well under $100 online and at most big-box stores, but any similar machine will do. Make sure it’s large enough to accommodate the filament spools you use. 
Screen removed from tray to make spacer
We had to cut away the screen portion of a few trays to create spaces between levels deep enough for large spools like this one.
Filament spool ready for drying
Dry the filament at a temperature of 140 degrees Fahrenheit for 4 to 6 hours, then run a test print to make sure you’re satisfied with the quality. 

You can do the same thing if you have a convection oven, which constantly circulates hot air just like the dehydrator. But you have to keep a close watch on the temperature to make sure you don’t melt the plastic. 
Cube 2 filament cartridge opened
If you use filament cartridges such as the ones for the Cube 2 printer, it's best to remove the spool for drying to avoid possible heat damage to the plastic case. Carefully press each tab around the edge of the cartridge and pull apart the two halves of the shell, then take out the cardboard spool and put it in the dehydrator. After drying, reassemble the cartridge, making sure the tiny verification chip in the base of the case remains in place and the filament is threaded correctly through the guides behind the exit hole so that it moves freely. 

Once you’ve removed all that annoying moisture, make sure your filament stays dry by storing it in an airtight container with a desiccant pack. Again, you’ll find many creative filament storage inventions online. We have dozens of cartridges and spools in the 3D ThinkLink Creativity Lab, so we like to use five-gallon plastic buckets with 12-inch screw-top lids. You can find them in the paint section of any major home improvement supply store. They stack easily and have plenty of room for filament cartridges and desiccant.
Storage bucket with screw-top lid and rechargeable desiccant block
Now that our filament is dry and safe in the sealed buckets, maybe we will use the dehydrator to make some jerky after all. Anyone have a good recipe?

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