How To Design and 3D Print for Assembly
How to design, 3D print and assemble builds that require multiple parts to be joined after printing.
For some 3D models, it might not make sense to 3D print it in one piece, whether it’s too big to fit in the build volume of your printer, would require too much support material, or be impossible to use after printing. There are many reasons to consider breaking up a model to make printing easier. However, there are some things you need to consider when designing your parts to make the assembly process easier.
I printed out this Jet Engine model by CATIAV5FTW on Thingiverse, which has a lot of parts that need to be printed out and requires a lot of fasteners to put it all together, which makes it a great example for designing for assembly.
Keep Organized
Make sure that after you print a part, you have a designated spot to put everything. I actually lost some of the smaller pieces just because they’re really easy to misplace, and I had to go reprint a second set of them. Having either one bin, or cardboard box, or just a plastic bag, any of these options is a simple way to just keep all of your projects organized.
Consider How You Are Going to Assemble
For some parts, I had to decide which direction to insert the screws. In some cases, like the side of the casing, a hex wrench wouldn’t fit, so that side had to be the side with the nut. If you’re designing the part, consider how you’re tools are going to fit, and if you’re assembling it, figure out the direction that’s going to work easiest for you.
Test Your Tolerances Before You Start Assembling
Parts of this build had small hexagonal holes to accept a nut, but the hole was too small to fit it, so I had to ignore that feature. This just meant I needed a longer screw, but if you’re designing the part, test how much larger you need a feature to accommodate the difference in size after printing. Sometimes you need a hole 0.1mm larger than a 3mm screw, sometimes you need as much as 0.3mm, it all depends on your printer’s tolerances and material shrinkage.
Lay Out All the Parts After They Are Printed
This is the point where you’ll realize you have parts you either misplaced or haven’t printed yet. It’s also really handy to immediately be able to see where your next piece is and not have to search through a pile of parts. This process is also called “knolling”.
When Designing or Assembling, Count Out How Many Screws, Nuts, or Washers You Are Going to Need
Be sure to have more than you need rather than not enough. There’s nothing worse than being ¾ of the way through assembly and realizing you’re out of the wrong length of screws and have to use some that are much too long, but still work.
Make Sure That Parts Look Good and Are as Clean as You Can Get Them Before Assembly
If your parts warp, come out a little stringy, or have some skipped layers, don’t be afraid to throw it out and try again. Assembling something with this many parts, there’s a lot of time invested in putting it together, so just take a little extra time on the front end to make sure print settings are right, prints stick down, and there aren’t any quality issues with the part.
Drill Out Holes if Necessary
In some cases, holes might be designed smaller than the screw so it can self-tap the plastic, in other cases, it’s meant to run all the way through parts and meet a nut on the opposite side. For the entire engine, nuts are used, so drilling out the holes to the exact size, or slightly larger than the screw makes assembly a lot easier.
Ensure That Parts Move Smoothly and Straight Before Gluing
A lot of these parts, like the fan blades, spin and have a small amount of clearance between the next section of guards. Glue the fans on slightly askew or not far enough into the center section and you get friction and resistance between the parts.
Hand Tighten Nuts and Bolts Before Final Tightening
Spinning on the nuts by hand, if you can reach, is going to make it a lot easier to assemble before using something to hold onto the nut. It also helps to make sure things line up or thread properly.
Dry Fit Parts Before You Break Out the Super Glue
A lot of these parts were a little finicky in the order they need be assembled. Glue things in and you may have a part that now won’t fit into place, or screw things together and realize you can’t fit a part in place and have to unscrew a dozen screws.
When Using Glue, Make Sure to be Controlled With It
There’s nothing worse than getting glue on a part that’s supposed to be moving or picking a piece up and sticking it to your fingers. Anytime that happens, there really is a bit of you in the project.
And that pretty much covers it. I’m sure there are many more tips that I haven’t personally encountered, but if you have and think it’s important, leave it in a comment down below. And don’t forget to stay tuned for more episodes of How To. I’m Alec from MatterHackers, thanks for watching.