What is Precision Injection Molding? 5 Things to Know

What is precision injection molding? 

1. Creates precise plastic components
2. Materials should have a low shrinkage capacity
3. Rely on the precision injection mold
4. A slow and steady process
5. Uses polymer optics

Many molding processes are known to mass produce products that are used in daily life. However, various industries have parts and pieces that are too complex to be made with ordinary plastic injection moldings. A process called precision injection molding is used for such processes. 

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But, what is precision injection molding? It is a highly technical process that makes use of precise molds. It is not used to develop whole products, instead, it develops more complex plastic parts. 

It differs from convection modeling in many ways, from the materials used to the mold created to the machine used in creating the product. This article tackles all you need to know about this technical process. By the end, you can assess if this is the molding process that you need for your next project. 

Creates precise plastic components

Compared to plastic injection molding, this method produces precise plastic parts. It does not mass produce whole parts. These products that are made in the process replace high-precision metal parts from different industrial appliances. 

The plastic components produced in precision injection molding require a tight tolerance. That means that the requirements for the product have precise and accurate procedures. When not followed, it can break inside the mold.

Products that are produced in precise injection molding are also comprised of complex geometric parts. These items have specific shapes that are needed for certain items in automotive, pharmaceutical, information technology, and medical fields. 

Materials should have a low shrinkage capacity

Precise injection molding can cause plastics to shrink during the manufacturing process. That’s why its materials are different from other injection molding materials. 

When materials have a high shrinkage capacity, they melt as they undergo the precise injection molding process. It ruins the product in the end. 

The materials used for this molding process need to have a low shrinkage capacity. The shrinkage required is around +/-0.01” or +/-0.02”. However, many materials can’t reach this range. 

An example of this would be ABS, a thermoplastic polymer. This kind of plastic can retain its elasticity while going through high temperatures. However, its shrinkage of +/-0.06 is still not appropriate for precision molding. Glass and other resin can be added to reach the desired shrinkage. These help the material absorb the excess heat while keeping the plastic stable. 

Rely on the precision injection mold

The precision made during this molding process is achieved through its mold. It needs to suit the design engineering requirements. 

To craft the mold, it needs to undergo accurate study, design, and testing. Many elements need to be taken into account for the mold. Here are some of the elements that need attention: 

• The mold cavity size – its position and the number of cavities it has
• The precision of the parting surface
• The materials used for the mold (this can be made from steel alloys or cast irons)
• The bottom plate’s thickness
• The runner size

Precision injection models are made with tolerances between +/-0.02” and +/-0.01” or less. All elements mentioned are considered when considering the dimensions tolerance. 

A slow and steady process

A high-precision model is required when creating plastic parts that have tight tolerances. Each part made in a precise injection model needs to be identical. This process can only be applied to plastic parts that are placed and connected with other parts in a fixed form. 

Because of the precise products, the manufacturer should not rely on rapid tools for this method. Precise injection modeling is a slow and steady process that makes a high-precision tool. 

Want more information on medical molds? Feel free to contact us.

Uses polymer optics

Polymer optics are used in precise injection molding. This is when CNC machining is used to mold the plastics into precise and calculated shapes. The machines have high pressure that helps improve the quality and precision of the plastic parts. They also manage to repeatedly create an accurate product. 

The entire process is automated and conducted through computers through an automatic handling system. It allows the producer to customize the process for the product needed to be molded. 

This reduces the cost of labor while increasing production efficiency thanks to its automated process.

Key Takeaway 

Now that you’ve answered what precision injection molding is, you can check if you can apply it to some of your products. As stated above, it can also develop a wide variety of complex products. 

Precision in Plastic Design for Injection Molding

Precision begins with the design phase. Our engineering team thoroughly reviews part drawings, evaluating them for molding and tooling issues. We examine features that may pose challenges for molded plastic, such as undercuts, texture requirements, draft angles, and thickness. By addressing these concerns early on, we ensure that the final design will meet the required form, fit, and function while optimizing the manufacturability of the part.

DFM Tooling

To simplify the tooling process, IMS engineers utilize the principles of Design for Manufacturing (DFM). By employing intelligent mold design strategies, we can achieve complex geometries using simple precision tooling methods. Our goal is to engineer cost-effective tooling solutions while maintaining the highest levels of precision and delivering on customer requirements. By collaborating closely with toolmakers, we guarantee that the tooling is precisely crafted to meet the specific requirements of each project. We also perform routine maintenance and upkeep on each precision mold to ensure mold longevity.

Precision Injection Molding Process Control

Our injection molding process is guided by an unwavering commitment to precision and consistency. Customer satisfaction is our primary goal, and we ensure that the tools and processes we use serve that goal. We utilize hydraulic and hybrid hydraulic electric machines that offer exceptional precision, as opposed to an injection molding machine focused solely on speed. By leveraging our expertise in process control and material behavior, we can achieve precise and consistent results.

From the very beginning of a project, IMS engineers identify the key parameters required to establish and maintain consistency throughout the manufacturing process. We adjust injection mold temperature, material temperature, injection speed, and injection pressure to optimize the mold cavity filling and ensure the parts come out exactly as intended and avoid pitfalls like sink or shrinkage. Our mastery of process control and material behavior allows us to minimize unnecessary post-processing requirements, such as trimming, and deliver high precision parts that meet the strictest tolerances. For necessary post-process treatments like assembly, painting, or fastening, IMS upholds our precision injection molding standards.

Prototyping and Validation

To provide customers with a clear understanding of the final product, IMS employs advanced 3D printing technology. Our precision 3D printers produce prototypes that closely resemble the actual model dimensions. This allows customers to visualize and test the part’s form, fit, and function before moving into production. In alignment with our goal of customer satisfaction, IMS utilizes the highest quality 3D printers to deliver prototypes with tight dimensional tolerance.

Tool Verification and First Article Inspection

Before proceeding to production, IMS experts conduct thorough tool verification and First Article Inspection (FAI). The toolmaker runs samples and ships them to IMS for evaluation. We measure the tolerances of these samples to ensure that the injection mold can consistently produce precision plastic parts within the given requirements. Once the customer approves the samples, the mold is shipped to our facility for FAI.

During the FAI process, we utilize the Cp/Cpk (Process Capability Analysis) method to assess the precision and consistency of the parts. By running our own sample lot and checking the primary dimensions of each sample injection molded part, we can determine the mold’s capability to produce parts that meet the desired specifications. Our target Cp/Cpk value is greater than 1.33, and we are proud that our regular results exceed this threshold, ranging from Cpk 2.5 to 3. This level of consistency assures our customers that each plastic part will be consistently produced with the utmost precision.

Production and Quality Control

Our commitment to precision extends to our production processes. We employ proactive Quality Assurance (QA) techniques to prevent defects and rejections. By identifying potential risks and areas of improvement, we ensure consistent and high-quality production. Our operators perform regular inspections throughout the production run, and we conduct maintenance on molds and injection machines to ensure longevity and precision.

In the event of a defective plastic part, we implement reactive Quality Control (QC) measures. We employ a corrective action process, starting with a corrective action report to contain the issue and prevent further defective parts from being released. Through root cause analysis, we identify the underlying cause of the defect and implement the necessary corrective solutions, such as process adjustments or molding machine operator training. This information is then fed back into our Quality Assurance system to further refine our precision plastic injection molding process and maintain the highest level of dimensional accuracy in each plastic component we manufacture.

Acceptable Quality Limits

In order to maintain the highest standards of quality, IMS utilizes the concept of Acceptable Quality Limits (AQL) based on Mil standard 105D. AQL is a heavily utilized sampling plan across our manufacturing processes. It enables us to conduct Out of Box Audits (OAB’s) and statistically assess the quality of finished products. By referring to the AQL chart (see below), we determine the number of parts in a lot that need to be tested to ensure compliance with quality standards. This rigorous sampling plan allows us to identify any potential deviations and take corrective actions promptly, ensuring that our products consistently meet the desired level of precision. By employing AQL, IMS further strengthens our commitment to making parts right the first time and upholding our reputation for delivering precise, high-quality plastic components.

Our Precision Injection Molding Training and Certifications

Integrated Molding Solutions understands that precision and consistency require skilled operators who are well-versed in the intricacies of the molding process. To ensure that our team meets the highest standards of expertise, we provide comprehensive training programs for our employees. Through these programs, our operators receive in-depth knowledge about injection molding principles, machine operation, mold maintenance, and quality control procedures. We also offer opportunities for our employees to become certified operators, equipping them with the necessary skills and knowledge to handle complex molding projects with precision and efficiency. By investing in training, certification, and continuing education, we empower our team of industry veterans to deliver exceptional results and uphold the utmost precision in every aspect of our operations.

For precision in plastic design and manufacturing, contact IMS today.