The goal of every manufacturer is to provide a final product free of defects by implementing quality control measures. However, if you find your manufactured parts are fracturing into separate layers, you’re witnessing a mode of failure known as delamination. The source of delamination can range from the plastics you use to the condition of your injection mold. Fortunately, Midstate Mold & Engineering has the experience necessary to troubleshoot the different causes of delamination in injection molding.
What is Delamination?
Delamination refers to a flaw where plastic manufactured parts fracture into layers. Delamination can be seen on the surface or can be hidden deep within a part. This separation occurs when the adhesion between layers fails or the polymers debond due to several factors. Shrinkage stresses due to improper curing and cooling can cause cracking that leads to delamination, or faults in the injection molding process or machinery can result in this defect.
What Are the Common Causes of Delamination?
Delamination can occur at any stage of the injection molding process, and it’s necessary to inspect all aspects to ensure quality parts manufacturing.
Compromised Plastics, Resin, and Polymers
Inspecting the materials being applied to the mold is the first step. Here are a few problems that can result in delamination or other part defects.
- Contaminated Materials: If contaminated or foreign materials find a way into the molten plastic, separation and part defects can occur because it cannot bond with the plastic.
- Incompatible Plastics: Pairing two plastics – such as with double-shot molding and overmolding – that can’t properly bond can lead to separation.
- Excessive Moisture: Plastic materials require a different set of drying conditions. Applying the appropriate heat removes the plastic pellets’ surface moisture to prevent delamination.
Injection Molding Processing Faults
The material’s factory instructions will list the requirements involving the injection molding process. Typical processing causes of delamination include:
- Improper Mold Temperature: Some types of thermoplastics require low temperatures to achieve impact resistance and strength, but too low of a temperature causes mold shrinkage.
- Inadequate Injection Speed: An injection speed that is too slow can lead to splaying and delamination. Incrementally increase the injection speed to see if the error resolves.
- Limited injection Hold Time: If the injection hold time is too short, there won’t be enough time for the material at the part’s surface to cool and will result in excessive stress from shrinkage.
Injection Molding Machinery Errors
This issue can stem from several components, so each element of the injection molding machine must be inspected. The following are some errors that can result in delamination:
- Gate and Runner Size and Design: If the radius of a runner is too sharp, it can cause resin separation during injection, and if the gate is too narrow, it might harden before filling the mold.
- Insufficient Cushioning: During the conversion process, if there is inadequate cushioning in the gate, there isn’t enough pressure to force material into the cavity.
- Excess Release Agent Coating: If excessive release agent is applied to the mold, it can puddle and cause pinhole surface defects in the mold.
How to Prevent Delamination
Resolving delamination in molded parts first requires pinpointing the cause. Consulting with your manufacturer over the proper plastic selection can prevent the layers of polymer from separating or debonding. The manufacturer must be extra vigilant to ensure the materials entering the mold are compatible and properly uncontaminated, and they must make any adjustments to the machinery if the processing equipment is at fault. Delamination in injection molding can be a complicated issue, but if you work with a manufacturer with a dedication to quality molding, you’ll receive durable and trustworthy parts. Midstate Mold and Engineering has been producing high-quality plastic injection parts to clients around the globe for 55 years. If you have questions about injection molding ad the plastics involved, contact us today.