Using snap-fits to design parts can save time and money by cutting down on material costs and the number of needed parts. It can also make assembly easier.
In the past, the only way to make snap-fit joints in plastic was to use injection molding. However, 3D printing has created both new potential and creative challenges today.
Understanding snap-fit design and how it interacts with manufacturing systems is crucial. Some things could be improved with snap-fit designs. This article aims to help you navigate the complicated world of snap fits by outlining the significant characteristics. We'll also look at the key categories and the top techniques for resolving prototyping problems.
Snap-fit joints are one of the easiest and most effective ways to assemble pieces. Snap joints do not require a variety of fasteners or tools. A snap joint is a little protrusion that can be a stud, hook, or bead in its basic form. This protrusion is deflected during the assembly. In other words, during connecting, a component's protruded portion may deflect during connection, capturing some of the traits of the mating component. You usually will only need access to the snap-fit joints after assembly. This dramatically simplifies the automation of snap-fit design. The snap design also dictates whether the connection is temporary or permanent.
The displacement of flexible features during assembly and disassembly is one of the critical factors in injection molding snap fit. Snap joints mainly use plastic materials, permitting fitting and flexibility. In other words, plastic materials support a respectable amount of flexibility and strain. Large deflections are thus possible without endangering the parts. Snap fittings have no load and minimal displacement in a connected condition. They are hence advantageous for plastic materials. Stressed plastics frequently develop creeps, which could eventually lead them to lose their tension.
Stiff locator pieces aid in aligning joining components. This aids in preventing displacement and releasing the fit from the joint. In this situation, catches, recesses, lugs, and other solutions are suitable. There are numerous applications for snap-fit joints. They can be paired with a few fundamental fit types to satisfy industry standards and particular design specifications. The variety of plastic snap-fit design examples is increased as a result.
There are several snap-fit joints with different applications. We will discuss a few of them below:
An annular snap joint design is used for elliptic or circular pieces. Pen caps and container lids are some of these components. One component of this kind of snap-fit joint has a ridge around its perimeter. This ridge fits snugly inside the second component's groove. In addition to bending, the assembly may result in tensile or compressive hoop stresses.
These multiaxial strains might be challenging to account for when building a joint. We may calculate the strain of straightforward circular designs depending on the iameters of the joining components. An essential characteristic of the annular snap fitting is the stretching and compression of the circumference.
The circular hook system is usually mistaken for an annular snap fit. However, this is untrue because annular fittings' deflection is bending-dominated. Depending on how the joining components are designed, annular snap fits may display various characteristics. Just like caps, they are simple to lock and unlock. Some may also offer a permanent, non-releasing connection, depending on the angles of the joining components. But in both cases, the rotation might be allowed.
They are the most common snap-fit joints used in the manufacturing industry today. These joints are easy to use in a snap-fit design because of their straightforward geometric designs. Calculating their strain during the connecting process is similarly straightforward.
The cantilever beam in the fundamental design has a tapered hook at the tip. The joining partner also has a matching pause. The construction depicts the tapered surface gliding over the surface of the joining partner. When the hook reaches the recess, the cantilever bends and returns to its original shape.
The joint may support release at a separation force, or it may be permanent. The surface angle between the hook and the recess determines this characteristic. The cantilever may occasionally not be delivered as a straight bar. Other designs feature cantilevers that are U- or L-shaped.
Plastic materials are the most commonly used with the straight bar cantilever joint. They offer the benefit of supporting longer cantilevers while using less area, permitting smaller deflection forces in tight situations. There won't be a requirement for sliders in the injection molding design when these L- and U-shaped cantilevers are on the edge of a part.
Torsion snap fits, in contrast to cantilever snap fits, essentially deflect beams by twisting a bar. They are basic techniques for establishing detachable connections. These sturdy solutions also function as an elegant and cost-effective connecting technique. The joining partner can be opened thanks to the design of the rocker's arm quickly.
The torsion of the rocker arm's shaft provides the deflection force. For optimum connectivity, the snap-fit rocker arm and torsion bar are integrally molded. When the hook's beam extends past the axis of the torsion bar, a seesaw mechanism is created. The hook can be raised, and the joint can be released by simply pushing the beam's free end.
Snap fit design is not a problem-free process. During the process of injection molding, snap fit, or 3D printing, there may be some problems. Here, we'll talk about some of the problems engineers face when making snap-fit parts:
Snap fittings that are repeatedly assembled and disassembled may fail at stresses lower than the stress on the material. Fatigue failure usually occurs at high loading frequencies.
Most thermoplastics and plastics are prone to creep. When the materials are stressed, this is a progressive deformation when materials are tressed. The connection between the components will deteriorate with time due to creep, which could make them worthless.
Tolerance problems may arise when gaps need to be appropriately positioned. Components will only fit together perfectly whenever there are tolerance problems.
Stress may concentrate at the root of the cantilever snap joint and is used in situations with sharp edges. The cantilever becomes more prone to shearing off as a result.
These are some of the things to do to prevent problems like a creep when designing snap fit:
Decreasing the cantilever beam's cross-section along its length is a good design practice. Fewer materials will be used, and the stress on the material will be distributed more evenly.
One excellent technique to distribute stress evenly among the components and strengthen the connection is to add a fillet to the cantilever's base. The cantilever base should be 0.5 times as thick as the recommended fillet radius.
Avoid constructing snap joints that are vertically formed from the bed upwards. Because the process is anisotropic, these are usually weaker. Additionally, only deflection of the cantilever or other snap fittings should occur during assembly. In the course of component connection, they shouldn't be redirected.
Lugs will facilitate the alignment of parts in an assembly. It will also aid in transferring part of the clips' shear force.
The purpose of this technique is to make the snap-fit design stronger. Getting the ideal stiffness level could take some early trial and error. However, a minimum clip width of 5mm is advised.
Snap fittings provide producers with economical and practical solutions. Snap-fit design, however, can be a challenging and iterative process. Therefore, you only need to adhere to a few basic manufacturing best practices to get the most out of your snap-fit joints. As a result, prototyping life cycles will be further shortened.
Your first port of call for all snap-fit design solutions isAres Prototyping. An essential component of our prototype operations is plastic fabrication. We are proud to have engineers who are experts in appropriate procedures and technology. We ensure that the on-demand services you receive are of the highest caliber. All of this is available to you at affordable prices. All you need to do is upload your design files for an immediate quote.