How to design Snap-fit Joints for 3D Printing?
Publish Time: 2019-09-09 Origin: Site
How to design Snap-fit Joints for 3D Printing?
The huge benefits are discussed by this guide of 3D printing snap-fits and provides design and materials recommendations.
Introduction
Snap-fit joints certainly are a easy and quick method of connecting two 3D printed elements together using interlocking features. Not merely are they an inexpensive and period saving connection method however they can also decrease the amount of parts within an assembly and give the possibility of speedy assembly and disassembly.
This article discusses the most likely snap-fit connections for 3D Printing, presents good design practices to consider when making snap-fits with plastics and briefly introduce advanced design specifications redirecting the reader to more descriptive information upon this topic.
Finally this article examines which 3D printing process are even more suitabile to manufacture your snap-fit connections.
Snap-fit connections
3D printed snap-suits also don't have injection moulding style restrictions (draft angles, separation lines, wall structure thickness, undercuts etc) and may become easily designed and altered. This makes them ideal features for fast prototype era where clearance and match are critical and as a result of this they are generally applied in the look and tests of enclosures.
Snap-fit building for a DIY loud speaker
Common snap-fit connections
There are 2 main types of snap-fit connections that work for 3D printing:
Cantilever snap-fits
The cantilever may be the most common snap-fit joint and includes a protrusion (some form of bead or hook) at one end of the beam and a structural support at the other end. This protrusion can be inserted right into a cut-out or deflects and slot upon insertion. Once inserted the protrusion bends back again locking the bond into place fully.
A cantilever snap-match on a 3D printed enclosure
Cantilever snap-fits are easy to design and intuitive for the user during assembly and disassembly. In many cases, it is the cheapest method of joining two parts together.
Annular snap-fits
The annular snap-fit utilizes hoop-strain to carry a pressed part set up. Common types of annular snap-suits are pen and bottle caps.
Push Pit Pen
With annular snap-fits, you'll be able to achieve a waterproof seal around the joint.
Because of this article the concentrate will be on cantilever snap-fits.
Designing snap-fit connections
In general, snap-meets will encounter the most stress during attachment and really should go back to their neutral position after the joining process is finished.
Once the best parts are mated, an undercut keeps them together. According to the form of the undercut, snap-match assemblies could be designed to be long term also. A smartly designed snap-fit with appropriate material may be used many instances without the noticeable fatigue.
Good design practice
Several design features could be implemented to lessen strain and pressure on the snap-in shape assembly. Included in these are:
Taper the design A snap-fit cantilever with regular cross section comes with an uneven distribution of strain (top image). An excellent design suggestion is to decrease the cross portion of cantilever beam over its size (bottom picture). This uses less materials and outcomes in a far more distribution of stress in the cantilever also. | |
Filleting the bottom of the cantilever The addition of a fillet at the bottom of the cantilever can help distribute the strain over a broader area producing the bond stronger. The radius of the fillet ought to be at least of 0.5x the thickness of the bottom of the cantilever. | |
Increase width Raising the width of the clip will add power to the look (if that is feasible in the look constraints). This might require learning from your errors to attain the correct stiffness nevertheless the clip ought to be at least 5mm wide. | |
Final position In reducing stress and enhance the strength of the bond make sure that the snap-fit cantilever is deflected through the assembly rather than when the elements are connected together. | |
Build direction It is necessary to consider build path. If possible stay away from designing snap-suit cantilevers that are designed up from the bed vertically (in the z path) as they are inherently weaker because of the anisotropic character of 3D printing. Simple fit built-in the path shown in the picture left shall be stronger. | |
Add lugs Consider adding lugs into your assembly to aid with alignment of elements and to transfer a few of the shear loads that the clips could be subjected to. |
Advanced design guides
Advanced style of snap-fit connections has gone out of the scope of the article. For more descriptive information on the look of cantilever snap-matches the MIT snap-fit design information and snap-fit style for plastics offer exceptional technical background and style specifications.
Tolerances
Variants in 3D printing properties including printer calibration, printing printer and components technology mean right now there are zero strict tolerancing guidelines when printing snap-suit connections.
For FDM a tolerance of 0.5 mm is preferred, and a tolerance of 0.3 mm greatest for all the 3D printing processes.
Technologies and materials
The table below discuss the primary 3D printing technologies and if they work for printing snap-fit joints.
Process | Description |
FDM | Cheap and effective method of production snap-fit connections but lower precision than other printing strategies. When printing with FDM it is suggested to use stress resistant components such as Ab muscles, TPU and nylon. |
SLA | SLA resins may be used for snap-fits, but are brittle increasing the probability of breaking after repeated make use of relatively. Long lasting SLA resin is preferred. |
SLS | SLS would work for printing functional snap-suit prototypes or end make use of parts which will be opened and closed often. For maximum tear level of resistance consider using an SLS Nylon. |
Material Jetting | Great strength and elasticity coupled with high res details makes Materials Jetting best for snap-fit applications. Long lasting resin (PP-like) and Digital Ab muscles will be the most common components for snap-fits because of the toughness and flexibility. |
Binder Jetting | Not fitted to snap-fit connections |
Rules of thumb
Implement good design methods that reduce tension (fillets, build path and locating lugs) and stress (tapered profiles, cantilever width)
Make use of a 0.5mm tolerance for FDM snap-in shape connections and 0.3mm for all the 3D printing processes.
SLS Nylon is most effective for snap-fit connections because of its tear resistance.
Prototyping plastics are perfect for style confirmation but are usually lower in power than SLS or Materials Jetting materials and so are not fitted to applications where in fact the connection will be opened up and closed repeatedly.