SLS 3D Printing vs. Injection Molding: When to Replace Molded Parts With 3D Printing?

Short Run Production
Customization
Stop-Gap and Bridge Manufacturing
New Products and Scaling Up
Aftermarket Parts
Spare Parts and Replacement Parts
Complex Designs
Manufacturing Aids

Case Study 1: Formlabs Wash L Components
Case Study 2: Haply Robotics
Calculate Your Own ROI and Savings

Virtually every piece of plastic used in daily life, from phone cases to the knob on your car stereo, is manufactured the same way—through an industrial injection molding process. Originally invented in the nineteenth century, but modernized in the mid-1950s, injection molding refers to a process where plastic pellets are melted, then squeezed into a hollow mold, where they cool and harden to form their final shape. When the mold opens, the final product is removed, and the mold can be used hundreds or thousands more times.

Injection molding is currently the preferred method of plastic fabrication due to its repeatability, low cost per part, and tight tolerances, as well as the range of mechanical properties available by choosing different types of polymers for the pellets. Because the mold and the injection pressure stay the same, tolerances are tight, and consistent dimensional accuracy is easily achieved. The process is automated to reduce labor costs, and the time required to complete each cycle is short, so manufacturers can run the machines at optimal efficiency. The only major investment is the die, or master mold, itself.

Creating the mold, usually through a metal subtractive manufacturing process, is extremely costly—usually upwards of four or five figures. This means that the process is only cost-effective at higher volumes, when the costs get distributed among hundreds or thousands of parts.

It generally takes around four to eight weeks to go from design to finished mold product. There is no room for a change in design once the mold is made, which can lock manufacturers into creating hundreds of thousands of the same part, even if the design could be optimized based on feedback from customers or manufacturing.

In recent years, some manufactures have looked to rapid tooling to bridge the gap between prototyping and end-use parts, and make injection molding a viable option also for lower volumes of parts. New methods of rapid tooling, like 3D printed or aluminum molds, are being adopted for both stopgap options while traditional molds are made, or for low volume production runs.

This white paper showcases the cost-dynamics for real-life use cases, and presents guidelines for using SLS 3D printing, injection molding, or both together.

Though 3D printing is firmly entrenched in manufacturers’ toolboxes as a prototyping solution, the adoption of it for end-use parts is still on the rise. Innovators in every industry are looking for ways to utilize the power, utility, and agility of SLS 3D printing in a variety of applications. We’ll take a look at how several manufacturers are utilizing the technology as a complement to their traditional processes.