How to join parts together?

[1031prime]

Hi all,
I am doing research before making my 3d printer purchase.
First desired project is to print a giant toy hammer with a dimension roughly 1M x 1M x 25cm.
Apparently multiple parts are needed and they will be joined together.
Per my research so far people include in their design holes and structures for screws. But for my project I hope that the hammer can be screw free and be assembled/dissembled freely.

Is there any commonly used nuts/bolts/buckles etc technics?

Many thanks.

[3dkarma]

There's a screw thread library on Thingiverse I've used quite a bit to incorporate threads into pieces I want to screw together. http://www.thingiverse.com/thing:31363

[ralphzoontjens]

I have successfully used dovetail joints and pin-hole friction fits, with 0.05-0.1 mm clearance. Not for parts that size though.

[pwoc]

I am interested in your pin/hole friction fit experience. I want to create a friction fit between an 8.35 mm nylon pin or dowel and a similar sized hole in nylon, something sort of like a Tinker Toy like fit. What would you recommend for a tight fit hole size? This would be in nylon which is slipperier than PLA.

[Wolfie]

First, let me say that your initial project may not be your best choice. There is a great deal to learn about the process and techniques from temperatures to modeling, all of which will have drastic affects on your printed item. You may wish to re-consider the giant hammer as your first project. Don't dismiss it as a project but slate it for a later time after you have become familiar with what does and does not work.

Printing takes time. Printing big parts takes a LOT of time. Printing multiple large parts that don't fit will drive you crazy and run you out of filament needlessly. Experience is a wonderful teacher. Let it teach you. But let it teach you on small items that take limited supplies to print and do so quickly.

Learn what the filament does when you print it at various temperatures. How does it hold shape? Does it sag. Play with cooling, bed heating and see how it affects the dimensional stability of the print. Try different filaments from different manufacturers until you find the one you like most. Then educate yourself on that one as much as possible so you can anticipate how it will react before you spend days printing a giant hammer that won't fit together.

Then you need to begin learning the various slicers. Some are better than others. Learn their strengths and weaknesses. Learn how to print threads, not an easy thing to print sometimes. Big threads are not so bad. I have had a nightmare trying to print small threads though. Sag, creep, and shrinkage all rear their ugly heads and make threads not fit

Pins, posts, and dovetails are the easiest to begin working with. If hardware is an option for your design, brass heat set inserts solve quite a few problems and are fairly easy to work with.

Depending on the printed plastic, solvents and glue is another are you need to research. ABS can be acetone disolved and using liquid acetone as a plastic welding agent is fairly easy as it actually welds the plastic using itself. JB weld, super glue, etc all are workable solutions as well for other plastics.

[Bassna]

Like Wolfie said, you really should put the "big" print's on the sideline until you get used to printing. Save yourself a ton of time and $$ with failed print's and fit's.

Having said that, if you are going to use ABS for the big print, mixing ABS + Acetone together and making a "glue" will work pretty decent with connecting thing's permanently. I used this method for my Giant T-rex skull print

IMAG1286.jpg

[Wolfie]

I am interested in your pin/hole friction fit experience. I want to create a friction fit between an 8.35 mm nylon pin or dowel and a similar sized hole in nylon, something sort of like a Tinker Toy like fit. What would you recommend for a tight fit hole size? This would be in nylon which is slipperier than PLA.

Tinker toys, at least from my childhood memory, are tapered at the ends with a slit across the wood to allow the ends to compress together. A similar layout could easily be done with printing in any material. Of course you need to focus on the width of the open slot as it compares to the tapering of the shaft. I don't think the hole in tinker toys is tapered but it might be to such a small degree that it escapes visual inspection as a kid. In printing I would taper the hole too but not as much as the pin. Anyway, thats where I would start at least. Pin tapered with a cross slit in the end, hole tapered but not as much as the pin.

[robosmith]

Alternatively, start by printing your model scaled to 10% (or less) size, to find out how the parts fit together.

Then just print the interface slices at 100% to avoid wasting filament on parts that don't fit.

[LambdaFF]

Personnally for most of my projects I use "pop" rivets. You can always drill the rivet head to disassemble and putting 2 holes facing each other is not complicated. Also the 'advantage of rivets is that you only need to see one side and they don't weaken you project like screws may.
Sure, when I need something nicer I can do something more discreet but this at least is a foolproof way to start.

[curious aardvark]

I had a pop rivet 'gun'. First try the rivet shaft snapped and is now permamently jammed in the gun.
So I've never actually pop riveted anything :-(
So they work well do they ?

There is a script for openscad that chops parts into sections with jigsaw like tabs on one part and the shaped holes on the others.

Ah here we go: http://www.thingiverse.com/thing:35834
Haven't tried it but it looks pretty effective.
And with a join like that then whatever glue you use will lock the parts into place.

First desired project is to print a giant toy hammer

seriously ?
Even with minimal infill do you have any idea how much filament that's going to take ?
Couldn't you just buy one of the inflatable ones they sell at carnivals and fairs ?
And use it for a paper mache mould ?