Metal-to-plastic conversion is a decades old concept, and it remains a popular option for addressing concerns about component or end product cost, weight, manufacturability and compliance. While metal-to-plastic conversion is effective, many industries — notably automotive, defense and medical — are leaning into it further in order to reap more benefits by consolidating multiple existing parts into a single complex injection molded plastic part.

There are many factors that impact injection molding tolerances—all of which need to be controlled with precision to meet final part specifications. The greater the number of factors, the harder it is to achieve tight tolerances consistently. That’s why it is so important to consider tight-tolerance requirements during the plastic part design process, where factors can be addressed through design modifications without impacting quality or performance. In fact, working with an experienced injection molder like Kaysun could actually result in even tighter tolerances, if needed, through expert alignment of design, materials, tooling and production process parameters.

Medical grade polymers are quickly becoming the preferred material for a broad range of surgical devices. In certain applications, the robust mechanical properties of medical molding polymers allow complete removal of metal from the surgical device design. In other instances, plastic and metal components can combine to create an enhanced product, with attributes that would not be possible in either an all-metal or an all-plastic device. 

Shrink rates for different materials vary according to the wall thickness of the plastic part. Designing wall thicknesses that are as uniform as possible helps to control the shrink rate for a specific part or product. As a consequence, non-uniform walls can lead to large pressure drops during filling, causing significant differences in shrink rates which could result in internal stresses within the part, creating warpage or other similar defects.

Manufacturers of rugged electronic devices (and their end users—for example, the military) count on their “rugged” devices to perform in challenging real-life conditions, and survive being dropped. Therefore impact resistance is a critical feature in product design and starts with material selection.

Insert molding is a type of overmolding where a hard substrate component or “insert” is placed inside a mold cavity in an injection molding machine and then “overshot” with an exterior layer—typically a thermoplastic elastomer (TPE). The interaction between the insert and the TPE must be fully understood to create the strongest possible bond. The surface of the insert should also be free of contamination, including dust or even skin oil—even the slightest contamination can weaken the bond between the TPE and the substrate, leading to premature failure.  

A surprising number of projects are completed without using a prototype mold—the general idea being that a prototype mold is just an extra step that slows down overall development and production adding unncessary cost. Actually, just the opposite is true—without a prototype mold, a lot of adjustments are usually required on the production tool, driving up cost which in turn causes delays in production.

Injection molders typically rely on outside mold builders to custom-build molds for their clients. Molds rarely arrive with perfect dimensions; typically, after the mold is received, checked out, and tested, adjustments need to be made to the mold to assure all design specifications are met. For most injection molders, this requires sending the mold out for those final adjustments, which burns up a lot of valuable time. Kaysun, however, has the ability make these adjustments in-house and “fine tune” molds after initial sampling to modify the mold core/cavity geometry and achieve the desired dimensions.

Cycle time directly influences part cost and capacities, so keeping it as low as possible is generally the overarching goal of engineers and project managers. In getting quotes from various injection molders they may be confronted with divergent cycle time estimates, calling accuracy and the molder’s capabilities into question.