How to design a 3D-printed snap closure that works perfectly?

0
A
8

Hey guys! I’m hoping I can get some technical advice in designing an enclosure for a scientific instrument — it’s a portable and remote logging device. The device I’m enclosing is about 100 mm square and maybe 20 mm high at the maximum. It has no display, it’s a data logging device, so we will get data off it via wireless after each test cycle. I’d love to make a case that snaps together, to keep metal parts like fixings to a minimum because of some rapidly changing magnetic field issues and concerns about eddy currents.

I’ll only need a small number of these for testing right now, so I need to 3D print the case, but I need to design so it will tool ok eventually. If the test results are good, the volume will follow.

Where do I start? I’ve had a play with some design ideas, but it’s impossible to validate them as our FDM printer really can’t handle either the fine detail or the strength. My snaps didn’t engage much and broke off really easily!

This is what the snaps look like, but they just break off so plz hlp!

    • A

      Hey guys! I’m hoping I can get some technical advice in designing an enclosure for a scientific instrument — it’s a portable and remote logging device. The device I’m enclosing is about 100 mm square and maybe 20 mm high at the maximum. It has no display, it’s a data logging device, so we will get data off it via wireless after each test cycle. I’d love to make a case that snaps together, to keep metal parts like fixings to a minimum because of some rapidly changing magnetic field issues and concerns about eddy currents.

      I’ll only need a small number of these for testing right now, so I need to 3D print the case, but I need to design so it will tool ok eventually. If the test results are good, the volume will follow.

      Where do I start? I’ve had a play with some design ideas, but it’s impossible to validate them as our FDM printer really can’t handle either the fine detail or the strength. My snaps didn’t engage much and broke off really easily!

      This is what the snaps look like, but they just break off so plz hlp!

      0
    • S

      Hey Alex. I hear you. FDM isn’t ideal for this kind of fine detail. I suggest you use SLS for the prototypes, as this gives you high strength and pretty good reproduction in the fine details. The biggest benefit is anisotropic properties, so you can have strength to spare in the snap features. Most suppliers carry PA12 nylon, which is good.

      At first glance, this is quite a stiff box. I assume that’s a 1.6 mm PCB I can see? Helps me to scale the case. If so, I’m not surprised the snaps break, they’re pretty aggressive (which is good) but the upstand is quite short, so you’re asking for a lot of concentrated bending as it snaps.

      There’s some changes I’d suggest to the snap feature, but a bit of context would help us. Q: Do you ever need to open the box?

      0
      Reply
      • A
        Sarah J.

        Hey Sarah. Ideally yes, we may want to open the box even though the product is ship-and-forget, collecting them and shipping them back for a second journey would be a nice option. Opening the box to recharge the battery is a bit untidy, but a charge point that we might never use seems like a waste of money.

        I was assuming we would smash the case open and just re-use the PCB, but that does seem wasteful now I write the thought down!

        0
        Reply
      • S
        Alex Bolt

        OK, that’s clearer. Here’s a few thoughts:

        • As they stand, you have about 1mm of hook, so you’ll need to either reduce that or make the leg longer. Less hook might be a bit weak, but you don’t have heaps of space for the snap to be longer and more flexible. The filet on the case edge limits you a bit.
        • Openability is a nice feature if it costs you nothing and isn’t a huge hassle in the factory.
        • The snap legs are adding a chunk to the wall thickness. That’s fine when you prototype, not so much when you mold these parts — there’ll be a sink on the outside when the thickness changes.

        I suggest you look at the design to tweak these aspects. And when you’re ready for prototypes, we can help you source SLS. That’s laser bonded nylon 12 (usually) and it’s a lot tougher and less isotropic than FDM, so flexing of snaps will flex and not break them so easily!

        0
        Reply
      • A
        Sarah J.

        OK, that’s all good. Any thoughts on a quick way to ease the wall section problem? I’m thinking about length solutions, but disconnecting the post from the wall sounds messy.

        0
        Reply
    • D

      It’s only a little elephant, we can eat it one bite at a time. How about if your snaps were not one piece, but several legs like a comb? This kills two birds – it will reduce the stiffness AND ease some of the wall thickness issues.

      0
      Reply
      • A
        DrewK87

        I think this is what you suggested, I like it. I’ve reduced the engagement and ‘weakened’ the snap legs as well.

        0
        Reply
      • D
        Alex Bolt

        I like this, those legs look less stiff. You added filets below the snap so they’re less likely to crack. That’s nice. Did you also reduce the depth of the hook engagement, do I see?

        I suggest you reduce the recess that you’re snapping into. Get it too deep and you’ll see a shadow on the outside, at the thickness change. Also fillets at the bottom of that pocket will blend the walls a bit better.

        0
        Reply
      • A
        DrewK87

        Hey DrewK87. It is feeling nicer. Yes, the fillet felt right, and I reduced the snap by 25% or so.

        I like your thinking. This is what came out of it. Thanks for your help!

        0
        Reply
How to design a 3D-printed snap closure that works perfectly?
Your information:




Suggested Topics

Topic
Replies
Views
Activity
How do you balance aesthetics with manufacturability in product design?
Hi!Currently, I’m working on a new consumer electronics product, specifically a sleek, modern-looking smart home assistant. This device integrates voice control, home automation, and entertainment features. However, it's tough trying to find the right... read more
J
M
4
113
Jul 09
Snap-fit features in injection moulding
Hi, I'm currently working on a project involving the design of consumer electronics enclosures, and I'm looking to incorporate snap-fit features into the injection-moulded parts. What are the best practices for designing snap-fit features... read more
M
1
530
Jun 13
Deep pocket/cavity – CNC machining
Hi everyone,I understand that there are limitations on the depth of cavities, and it’s generally recommended not to exceed a depth-to-width ratio of 4:1. However, I have a design that requires a pocket/cavity with... read more
N
3
800
Jun 05
Injection molding wall thicknesses – tips?
Hello,I am a mechanical engineer currently in the design phase of developing rectangular housings using PA66 GF30 material. From my previous projects, I've encountered challenges with achieving consistent dimensions, particularly with thin wall sections.... read more
R
M
4
1.1k
May 03
CNC machining design with engraved letters – help needed
Hello! I need some advice on CNC machining designs with mechanical engraving.should I integrate the lettering directly into my CAD designs, or is it better to engrave them after machining, separately? I’m planning on... read more
T
2
1.0k
Apr 15