Just like printing with other plastics such as ABS, please make sure you have adequate ventilation in your workspace. Here is an instructable outlying the safety risks of printing with materials such as ABS, pure Nylon, and trimmer line: http://www.instructables.com/id/Is-3D-Printing-Safe-or-DIY-Testing-for-HCN-from-/
Advantages of Nylon:
1. It is very cheap, at less than half the price of conventional filaments. This is because the plastic is readily available as weed wacker line.
2. It is readily available. Hardware stores everywhere sell weed trimmer line in many different sizes and colors. See below for a list of internet sources.
3. Prints are flexible and wear resistant. Unlike ABS and PLA, Nylon is far less brittle, and therefore stronger. It also has self lubricating properties which are usefull for printing gears ect.
Disadvantages of Nylon:
1. It is more stringy than ABS or PLA. Overfilling the part will make a gooey mess with strings everywhere.
2. It warps more than ABS or PLA. This is why printing on cardboard is necessary to prevent warping.
3. It requires more clean up due to having to print on cardboard. More details are below.
4. You must dry Nylon before printing (see below)
5. Nylon can emit fumes (see above). I am not sure they are any worse than ABS, but be careful.
Steps for printing Nylon:
1. Get 0.105 inch trimmer line. This will work with a 3mm extruder. Make sure it is Nylon. I got mine on amazon here: http://www.amazon.com/dp/B001BKZT1S/ref=pe_175190_21431760_M2T1_SC_dp_1
2. Dry the filament by putting it in an oven at 300 F for 3-4 hours. Don't dry all of it at once especially if you live in a humid climate. I dry enough to last a week. If you do not dry it, the extruded material will get all foamy and make your parts very bad looking. This is due to the evaporating steam.
3. Put the dried filament in a ziplock bag, and put some dessicant with it to keep it dry. I used some "closet dessicant" I got from Walmart, with the ziplocks that have a slide thing.
4. Feed the filament out of the bag and into your extruder.
5. As seen in the video, make a bunch of little clamps to go around the outside of your bed. I just used some pieces of wood with holes in them and some small bolts that go through the table. You could also print something that would probably work better.
6. Cut a piece of cardboard to size, so that it fits under all of the clamps. Slide the cardboard in and screw the clamps down. You can use pieces or cardboard multiple times, and on both sides.
7. Go to http://forums.reprap.org/read.php?1,70471,page=3 for the slic3r settings (config.ini). You will need to get your heated bed up to 120 C and your nozzle up to 245 C. The given printer settings are not going to work for everyone, so experiment.
8. Calibrate the height you want to print at. The closer to the cardboard you are printing, the more adhesion, but the more cardboard you will need to get off of the bottom when the print is done. It will also make you use cardboard faster. On the other hand, if you don't care what the parts look like, it doesn't matter.
9. Start printing :)
10. Optional: Use a dremel tool with a fine wire brush attachment to take off the cardboard stuck to the bottom. The wire brush should take off the cardboard quite easily, but not damage the Nylon.
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