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How to design Snap-fit for 3D Printing Enclosures Part 1

So in this article there are three parts, which will give you a detail concept on snap-fits.

  • Snap-fit joints are a quick and easy way of connecting two 3D printed components together using interlocking features.
  • snap-fit is an assembly method used to attach flexible parts, usually plastic, to form the final product by pushing the parts’ interlocking components together.

Why do we use Snap Fits???

  • Improved aesthetic and it will be good interlocking feature.
  • Can be designed right into the molding process, eliminating assembly steps and speeding up assembly and throughput.

Advantages of Snap-fits:

  • Snap-fits can decrease product cost by reducing the overall part count and lowering labor costs.
  • Easy to lock two parts without damaging the part by screwing and tapping.

There are 2 main types of snap-fit connections that are appropriate for 3D printing: cantilever and annular.

●    Cantilever snap-fits

●    Annular snap-fits

Cantilever snap-fits :

  • The cantilever is the most common snap-fit joint and consists of a protrusion (some type of bead or hook) at one end of the beam and a structural support at the other end.
  • This protrusion is inserted into a cut-out or slot and deflects upon insertion. Once fully inserted, the protrusion bends back locking the connection into place.
  • Cantilever snap-fits are easy to design and intuitive for the user during assembly and disassembly. In many cases, it’s the cheapest way to join 2 parts together.
  • A cantilever design can be multiple use or permanent. A multiple use snap-fit usually has a lever or pin to be pushed, in order to undo the snap-fit.
  • However, on a permanent snap-fit there is no lever or pin. Attempting to undo a permanent snap-fit can result in the piece breaking.

U-Shaped Cantilever                   L-Shaped Cantilever

The U-Shaped design has the additional benefit of constraining the maximum amount of deflecting that a user can apply as the moving beam contacts the backup surface of the part. This eliminates the possibility of the user over deflecting the cantilever causing failure. The total deflection can also be quite large allowing for easily removable parts.

The “L” shaped snap is formed by designing in slots in the base wall which effectively increases the beam length and flexibility compared to a standard cantilever beam. This allows the designer to reduce the strain during assemble below the allowable limit of the selected material. It should be noted that adding a slot to the base wall may not be acceptable in some designs for cosmetic or air flow concerns.

Why do we use cantilever snap-fits  ???

For special cases and/or tight packaging, the U or L shaped snap may be advantageous. Both the U and L shaped design are easily designed with smooth large radius features which typically have reduced strain during assembly. mundane tamper-proof aspirin bottle-and-cap assemblies  to highly engineered, rugged parts such as power tool housings, automotive wheel covers, air cleaner housing and door handle assemblies.

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