Kawai Plastic Industry Uses the Fusion 360 Simulation Extension to Prevent Short Shots in Injection Molding

Yuji Fujimura Yuji Fujimura August 10, 2023

5 min read

This post is also available in: 日本語 (Japanese)

See how the Fusion 360 Simulation Extension helped Kawai Plastic Industry reduce trial injection runs by 25% and improve cost efficiency.

Kawai Plastic Industry is a Japan-based company focused on the manufacture and processing of plastic injection molded products, such as automobile parts. As the manufacturing industry evolves, the team enthusiastically absorbs new knowledge and adapts new technology when necessary. 

Case in point, to prevent the occurrence of short shots and weld lines in the injection molding of plastic products, the company’s engineering department implemented the Fusion 360 Simulation Extension and began utilizing injection molding simulations. As a result, they were able to reduce the number of trial injection runs by 25%.

Plastic injection molding efforts to prevent short shots

Koichi Sato, a member of the Kawai Plastics Industry Engineering Department, says the biggest problem his team faces is the occurrence of short shots in the mass production of plastic products. Short shots occur when the cavity of the mold does not fill completely with material, resulting in an incomplete part. This can be due to a number of reasons, such as material cooling too quickly to pack the cavity, not enough cavity pressure, or poorly designed features that limit material flow to certain regions of the part. 

“When designing a new mold, we pay attention to the position of the final fill area to avoid short shots,” explains Sato. “Since it takes time to confirm the results of those trial runs and make corrections, it takes about one year to complete a single mold.” 

If a short shot occurs and the product is shipped as incomplete parts, the customer has to initiate additional inspection steps at the delivery destination and would require additional parts to be produced to cover the unusable product, increasing production costs and lead times. 

In the company’s production process, the design and manufacturing of molds are often outsourced to subcontractors, making it difficult to make fine adjustments at the design stage. As a result, problems were often discovered during trial runs after the molds were already made. 

“Some of our suppliers have asked if we could design molds earlier with higher accuracy and without short shots by using simulations at the design stage rather than just trial runs,” says Sato. “We decided to look into the possibility of reducing the number of trial runs, which would also lead to lower design costs.”

Trying the Fusion 360 Simulation Extension

The trial version of the Fusion 360 Simulation Extension was used to evaluate its functions and ease of use. “I heard that people around me were using Fusion 360, and that it was good software, so I decided to try the trial version of the Fusion 360 Simulation Extension,” Sato says. “We were able to test the extension sufficiently during the trial period. Using past mold data, we could confirm the effectiveness of plastic material flow analysis through injection molding simulation. We decided to use Fusion 360 because it allows us to read 3D CAD files from other companies without data conversion, which we believe will be useful for our future designs.”

Reducing trial runs and improving results

The trial ended up yielding exceptional results. “We were able to reduce the number of trial runs of the mold by 25% on average,” Sato says. “The 25% reduction is significant because we have to stop the actual production line for about four hours during trial runs. We design about 30 new products annually, so just one less test run saves us about 120 hours every year.”

“Injection molding simulation studies in Fusion 360 can determine if a plastic molded part can be molded, if certain appearance defects will occur, and how much it will warp,” he continues. “The material data used for the simulation is the same as that of Autodesk Moldflow and is available in 11,700+ thermoplastic material grades. The Fusion 360 Simulation Extension enables flow analysis and filling simulation using material data to determine warpage and other properties. If more detailed verification is needed, Moldflow can be used. Through flow analysis, we could visualize and eliminate potential issues.” 

Clear visual confirmation

Fusion 360’s injection molding simulation study displays possible molding defects with red and yellow animations. By simply specifying the mold design data, material data to be filled, and injection time, users can visually confirm that the plastic parts to be manufactured will be molded correctly. 

“In actual injection molding, the liquid plastic enters the mold in about one or two seconds,” Sato says. “If the mold is not designed to properly release the air in the mold at that time, there will be short shots, and parts will be chipped. Simulating this problem in advance with flow analysis allows us to provide feedback on the mold design. This eliminates the time and cost of trial runs. In particular, there was a high tendency for air to clog the final fill section where the resin is poured.”

“Our suppliers requested that we focus on checking countermeasures to prevent this problem,” he continues. “But in the past, we couldn’t visualize this data and had to make adjustments based on observation and past knowledge. By providing animations of the injection molding simulation results to our customers, we can prove the measures we take at the mold design stage. Now we can directly visualize the data, so we can focus on the finest points and adjust the position of the final filling section.”

What’s next?

The company aims to further utilize Fusion 360, including data linkage with jig design and mold design. “Currently, our main focus is on flow analysis and final fill adjustment to prevent short shots, but in the future, we’d like to analyze weld lines and air traps as well,” says Sato. “We also communicate with external subcontractors mainly by e-mail, so in the future, we want to improve efficiency by collaborating on the cloud. Eventually, we also want to utilize Fusion 360 beyond resin flow analysis—we want to take on the challenge of in-house 3D CAD design and processing.”

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