Living Hinge Plastic Design

The concept is simple but we are asking a great deal of a very small section of plastic.

Living hinge plastic design. Polyethylene is the second most common living hinge material with similar properties to polypropylene. Living hinges are thin sections of plastic that connect two segments of a part to keep them together and allow the part to be opened and closed. They are very durable and with good design can last for millions of cycles. But as the part bends it creates strain called tensile stress.

With injection molding the main design focus is on the hinge s thickness recessed flat sections and radii. A living hinge is a thin section of plastic that connects two plastic bodies together. The nominal wall thickness is 060 inch with the gate located on the bottom of the box. The purpose of the hinge on a ketchup cap is to keep the cap connected to the main body but also allowing it to move out of the way for dispensing.

And with living hinges the interaction between these components is highly intertwined. The design of a living hinge takes into consideration the ability of the material to withstand strain and the material s tensile strength. A familiar example would be a ketchup cap. Living hinges are a great example of why you must follow the strategy of legendary plastics designer glenn beall for a successful application.

The restriction to melt flow across a hinge invariably creates a pressure drop on its far side. Get a free design cube here. If it is too thick it will create too much stress and the part. Typically these are used in containers that are used in high volume applications such as toolboxes fish tackle boxes cd boxes etc.

Due to its toughness and ductility polypropylene is the best material choice and a well designed injection molded pp hinge can have an almost infinite service life reaching several million flexes. The cardinal rule for good molding is to maintain a uniform wall thickness. A living hinge is a thin piece of plastic surrounded by thicker plastic that allows a part to fold or bend from 1 to 180 degrees. A computer aided moldfilling analysis indicated an average end.

In 3d printing an additional design element are the radial connections. In other words radial connections between the hinge and rigid sections as well as the radii around the bend are of utmost importance. Living hinges are those thin areas in a plastic part along which the part can fold. They are often used to produce a container and its lid as a single molded part and if properly designed they can open and close thousands of times without ever losing strength or flexibility.

If plastic is too thin it may not have the necessary strength and the part may tear. Mitch tucker from monroe engineering goes over the basics of hinges and what makes the plastic living hinge so unique. Each of his five key components requires special attention in making functional hinges. Plastic living hinges are be used for many applications across countless.

The box shown in the opposite figures measures 3 250 inches by 2 500 inches with a combined height of 1 150 inches. Living hinges are a gross violation of that design rule. In a typical application a hinge can flex through an arc of 90 or 180 degrees but arcs of 270 or even arcs that approach 360. If these elements are properly.