How to join printed parts

I'm sure everyone has their own favorite way of joining printed parts together that would not otherwise fit on the print bed. I think it would be good to start a thread compiling all of our techniques. Let's hear your methods.

I don't have my printer yet, but personally I think the best way is to print a "tongue and groove" type fitting, where one part has a tab slightly smaller than a hole in the other part. Then, you put ABS glue or acetone on them and glue them together.

 

Most wood working joints would work very well for 3d printer design.

The biggest thing to consider when designing is "Will this require support?" The problem with the tongue and groove is you're limited on what directions you can print that at without requiring support. Something similar to a dovetail could be used effectively in a lot of orientations without needing support.

 

I like the idea of dowel pins, that seems pretty effective and easy to make work. As for requiring support, I agree, every design will need a different method for joining.

How about "chemical welding" techniques. For example, lets say you wanted to print a 3 meter long truss to span across something. Are there methods of joining the materials so that they behave as one object and are not weak at the parts where they join together? I have heard that acetone melts them together and then evaporates, leaving only ABS behind. Are there any other, perhaps better methods?

 

For PLA, I've had fantastic results just making sure the bits I want to bond together are printed flat on the bed, and just using cyanoacrylate (super glue) to bond the halves together. Leave under pressure (put the pieces in a vise) for about an hour, and they are stuck just as strong as the layer bonds. Bonds between bits that are not perfectly flat like the bottom of the print are considerably weaker, but it means I can print a full 3D shape "flat" by cutting it in half before slicing, and get all nice surfaces the whole way around, rather than having any kind of yucky underside.

 

The stuff called "Goop" in pretty much any of its forms. Can be messy but bonds well.

 

Weld-on acrylic glue works very well for PLA. I used weld-on 3 but you can use any number, just depends on what working time you want.

 

Many thanks for the replies. Whenever my printer arrives I'd like to mess with printing some structures, which will need to behave as one solid piece. I'll give some of these ideas a try and see which one works best.

 

http://www.amazon.com/IPS-Weld-On-A...UTF8&qid=1395171150&sr=8-6&keywords=weld-on+3 this is what I use. It's a chemical bond like you were hinting at earlier.