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How to Choose a Custom Injection Molding Manufacturer


Plastic injection molding is a modern manufacturing method that’s popular thanks to its cost-effectiveness at high volumes and tailor-made solutions for design problems. It’s also highly customizable to deliver your unique product specifications and requirements. The custom injection molding process uses plastic resins or polymers heated, melted and injected into custom molds under high pressure to produce products that precisely meet your project demands.

While this manufacturing process may sound simple, you need a custom injection molding partner that understands and caters to your needs and specifications. The perfect partner may not exist, but you can assess custom injection molding manufacturers on a few key factors to understand if they’re the right fit for you. 

1. Production Volume and Capacity Specification

There are two main types of custom injection molding manufacturers who have the skills and equipment to produce different volumes of plastic parts:

  • Low to medium-volume molders: These molders specialize in producing 10,000 parts or less. They’re suitable for businesses looking for parts in small volumes, such as the agriculture, medical and aerospace industries. You should also consider molders in this category if you want to create prototypes for testing or bridge the gap between small production units for market testing and full-production tooling.
  • High-volume molders: These molders produce injection molded parts in runs in the hundreds of thousands to millions. They should be your ideal choice if you want to produce parts in bulk. 

A company’s machine size and number determine its production capacity. Injection machine size is expressed as tonnage and the higher the tonnage, the larger and higher the complexity of parts it can manufacture. However, the best custom injection molding companies specialize in high and low volumes because they can accommodate your product changes.

2. Specific Product Application

The intended use of the part you’re producing through custom injection molding determines the best manufacturer because they use different designs, materials and production techniques. Your product application also dictates the development and production process the molders use to deliver the parts according to your specifications.

Establish the type of plastic resin the manufacturer uses and its suitability to both your product’s end use and your budget. The molding material is another important consideration — steel molds, for example, are ideal for large and long-term production, while aluminum works best for small and short-term production.

Your partner should be able to produce your custom injection molded parts to specification. They should also have the skills, experience and knowledge to make strong recommendations that may save you time and money without sacrificing quality

3. List of Value-Added Services

The best custom injection molding companies should be able to do more than produce parts from your design prototypes. They need to offer you valuable advice on how to ensure the parts are produced to geometric dimensioning and tolerancing (GD&T) standards, undercuts, draft angles and material selection to guarantee the project’s success. Additionally, they should utilize their knowledge to clearly explain the advantages and disadvantages of different options, such as injection molding gates.

Mold flow analysis is another value-added service offered by reliable molders to determine potential design issues and improve part quality and performance. Generally, a full-service plastic injection molding partner offers prototyping, part design, mold flow analysis and quick response manufacturing to deliver decided cost and tie efficiencies.

Quality and On-Time Deliveries

4. Quality and On-Time Deliveries

In manufacturing, sticking to deadlines and delivering quality are non-negotiable requirements. To ensure your plastic custom injection molded parts are produced and delivered on time, you need to communicate your expectations with your manufacturer. 

Assess your manufacturers’ production processes to understand how efficient they are and verify they can deliver within your timelines. It also helps to ascertain whether they can deliver products that meet your quality standards. Any reputable custom plastic injection molding company has an in-house quality assurance team that oversees the entire process to prevent quality compromises. They should also be certified by the International Organization for Standards (ISO) to verify their commitment to using the production techniques.

Some essential standards for plastic injection molding companies are AS9100 and ISO 9001, which provide them with an approach to achieve effective quality management. Polycraft Products is an ISO 9001-certified company with industry-leading delivery times and quality standards and committed to process improvements. You can count on our team to create effective custom injection molded parts and solve complex problems using the latest technologies, such as laser scanners and touch and visual CMMs.

5. Pricing 

Custom injection molding costs vary greatly depending on the production volume, simplicity or complexity of molds, the size of the mold and materials used for plastic production and mold making. Before settling on a manufacturer, you should assess quotes from several to find one that delivers your project within your budget without compromising on quality.

When requesting quotes, provide manufacturers with a complete summary of your project to ensure you get the total pricing without incurring costly surprises later. In the quotes, look out for any hidden charges and request a detailed description of payment terms so you can plan accordingly. 

Avoid running for the cheapest quote because it directly reflects the value of molds and services you sign up for. It could also indicate long or inaccurate lead times — time is money, and confidence in a finished product’s delivery date is essential. With plastic mold injection service, it’s mostly worth paying more if it guarantees precision, good design, high-quality material selection and whether or not the manufacturer offers on-time delivery.  

Contact Polycraft Products for Precise Custom Injection Molding Services

Are you looking for a custom injection molding company that ticks all the boxes? Polycraft Products fits the bill perfectly. We’re a full-service molding company that’s been in operation since 1982, consistently delivering efficiency, high quality and safety. Our experienced team is knowledgeable and well-equipped to form plastics and resins in any shape or size using our turnkey injection molds, and we offer industry-leading delivery times.

We work closely with customers to understand your needs so we can develop effective custom injection molded parts that accurately meet your specifications and requirements. You can count on us to provide advice and valuable recommendations at all stages of the process, from concept design to production. 

Whether you are looking for custom injection molded parts to use in the aerospace, medical or defense industries, we will deliver high-quality parts that comply with industry standards and regulations. To learn more about our custom plastic injection molding services, contact us today.

Contact Polycraft Products for Precise Custom Injection Molding Services