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My son wanted us to print the RAMbone slingshot after seeing a YouTube video about it.

We found the .stl at http://www.thingiverse.com/thing:311393. During the 17 hour print, the filament spool jammed and there was a crack that made the solid part useless... Or is it? I tried welding the crack with the same filament spun in a Dremel tool. The fast speed melts the rod and repaired the part. What a great tool a Dremel is for anyone getting into 3D printing.

The part turned out usefull. Project saved.

I do the same with a 3D Printer Pen. I have never believed the claims that have been made, like doing a free hand model of the Eiffel Tower and my experience has confirmed this.

The pen I purchased for Amazon looked to me a plastic equivalent of a wire feed MIG Welder. After using it with ABS, I find this is exactly what it is so much so that MIG welding techniques carry straight over to the plastic. For example, if you weld over a crack with a MIG welder - you still have a crack that usually comes back. If you vee out the crack and weld it back with multiple passes it works, same with the plastic. This works so well that I have used it to weld a crack in the bagger attachment on my John Deere Lawn Tractor.

Using the Dremel is also a great plan and emulates another practice of Friction Stirred Welding.

The printer pin used for 3-D printing is useless to me BUT as a plastic welder it is terrific.

nitewatchman

I do a bit of electronics work in my job, and finally the day came where I couldn't put off a hot air rework station any longer.

Surprisingly there were some fairly reasonable ones available from eBay (mine's the WEP 898D, cost about $100 delivered) and I've found the hot air pen on this works extremely well as a plastic welder, plenty of videos on how to use a hot air welder without the funky feeder nozzle out there. I know that's a lot of cash to drop to fix the occasional munted print but if you have something like it already, it's pretty handy.

I do want to give that a shot with my hot air rework station, One thing I have done is melt off the fuzzies from a PLA part with it, cleaned up the part half decent.

I've not actually tried it on prints, but have repaired a few other plastic things around the house with it.

Prep is key. Drill hole at either end of the crack for relief, file a V-groove the size of the filament and as deeply rooted as possible, whack the heat up to a magic point*, put the filament in the end of the groove pointing down the groove (so you're pushing filament into the repair rather than draping it over the top) and gently work down the crack with heat pointing just forward of the filament so the air hits the groove first, then the filament.

Similar action to oxy or TIG welding but much, much easier (and no weld puddle).

*magic point - too hot and it burns the plastic. too cool and it's too slow, which means the heat has time to soak into the plastic around the repair, which usually means holes or buckling of the good plastic around the joint. I find 320º about right for ABS, 400º for Nylon.