Making Complex Geometry Parts with Advanced Injection Molding Technology
Not long ago, there were limited options for making plastic parts that have complex geometries. A common method was CNC machining, which can be expensive and slow. Plastic injection molding is a much faster and cost-effective way to make parts, but those with intricate designs can cause quality and processing challenges. However, New Berlin Plastics is using an innovative new tooling technology that makes it possible to produce consistent quality complex parts.
Recently, a motorcycle manufacturer hired New Berlin Plastics to mold a new exterior air vent panel that features a complex honeycomb pattern. The panel needed to be strong enough to protect the motor against debris but well perforated to permit proper airflow. The challenge was finding the best way to make such a complex part in a cost-effective manner.
Predicting problems
Before designing a mold for the new motorcycle part, NBP ran a mold flow analysis that simulated how the tool would perform in a production environment, which identified potential problems with trapped gas and heat during the injection process.
“The part’s complex honeycomb pattern requires the mold to have many angles and corners, causing a tortuous path for the molten plastic,” says Joseph Mechery, vice president of sales at New Berlin Plastics. “Gas gets trapped during injection, preventing the polymer from completely filling out the mold cavity. The results are warped and brittle parts, higher scrap rates, and damage to the mold from overheating.”
In situations like this, ejector pins, which assist in the removal the part from the mold, can serve a dual purpose to vent a mold as well. However, ejector pins are not designed to handle heavier duty venting demands, so the fragile pins tend to get clogged and break. Extra maintenance requirements would add time and cost, so NBP knew a mold using ejector pins for venting would not be the best solution.
A new way to vent
To solve this problem, New Berlin Plastics partnered with Next Chapter Manufacturing (NCM), an additive tooling company. NCM develops 3D printed mold inserts with special venting pins made from a unique technology called InnoVent. Adding InnoVent pin inserts in areas of the mold that tend to trap gas creates a microscopic porosity in the steel. Gas vents out through the mold’s pores but the polymer stays contained and flows smoothly. The pores in the steel are invisible to the naked eye at only 25 microns— about one quarter the diameter of a human hair. See a video demonstration by NCM that shows how air flows through the mold when it’s submerged under water.
InnoVent inserts extend the life of the tool, reduce ongoing tool maintenance costs, and aid in producing repeatable high-quality parts when part design creates challenging trapped gas conditions.
NBP built the new mold and added the InnoVent inserts, which NCM 3D printed out of 420 grade stainless steel. In total, the insert featured 1,200 vents. The motorcycle company is pleased with the results of its newly designed vent panel. The part is flat and smooth, providing a look that’s in line with the company’s iconic aesthetic. Plus, the panel is lightweight but strong enough to handle road debris impacts without cracking.
Design for manufacturing
NBP is a step above other injection molders because of its deep experience in providing customers with recommendations to design for manufacturability.
“We do more than just mold a part. We take an overall look at the design intent and the part application, then we identify the part design, tool design and material selection that helps engineers take the cost out of the part, eliminate potential failures, and simplify tooling,” Mechery says.
Do you need help making plastic parts with complex geometries? Contact NBP to discuss how we can help you.
