Manufacturers employ several different processes to create molded plastic parts depending on the part design and application. Injection and blow molding are two of the most widespread and cost-effective means of forming high-quality plastic components. Before deciding on which of these two molding processes to use for a production application, industry professionals should acquire an understanding of the differences between them and their advantages.
What Is Injection Molding?
The injection molding process employs precision molds and tooling to produce solid plastic parts.
The key to this molding process is in the mold. The custom-designed components are made with great detail from stainless steel or aluminum and built to withstand high temperatures and extreme pressures. Additionally, the two halves of the mold require a high precision match to allow for controlled operation and proper part production.
Once the mold is designed and produced, it can be used for manufacturing operations. The injection molding process begins with the melting of resins or polymers at very high temperatures. The liquid plastic is then injected into the completed mold using high pressure, ensuring that the material reaches all the cavities of the mold. Following the injection stage, the mold is cooled, allowing the plastic to set or harden. When sufficiently cooled, the mold releases the completed plastic part.
Plastic injection molding provides a number of advantages, including:
- Development of highly detailed molds with multi-cavity options
- Precise, cost-effective production of large volumes of small parts
- Greater material flexibility and color options
- Better material use efficiency with little scrap or waste
Injection molding is suitable for production applications that call for high volumes of precision parts. In particular, the process commonly finds application in the manufacture of thousands or millions of the same part ranging from bottle caps, hair combs, and cell phone cases to automotive parts and medical equipment components.
What Is Blow Molding?
In contrast to injection molding, the blow molding process employs principles similar to that of glassblowing to create hollow parts. Compared to injection molding, the blow molding’s tooling formation stage is not as critical. However, careful monitoring of the molding process is essential due to the increased potential for the development of wall thinning, air leaks, flash, and streaks.
The blow molding process begins by heating raw plastics materials to temperatures of 350-420 degrees F. The material is then extruded from the head of the machine as a hollow tube aka parison. The mold closes around the parison and roughly 80psi is blown into the parison causing it to balloon and take the shape of the mold. The mold is then cooled, allowing the plastic to “set.” Once the set time has been reached, the mold opens, and produces the product to the operation. The part then goes through a degating process which allows inside of the part to be accessible.
The advantages of plastic blow molding include:
- Lower production cost when compared with injection molding (depending on plastic shot weight)
- Lower initial machine investment
- Elimination of the need for two-part mold components (leading to greater part design flexibility)
Blow molding is a highly cost-effective means of creating uniform and thin-walled hollow components—such as bottles—for use in a wide range of industries, including consumer products, automotive, medical, and pharmaceutical.
Contact OMICO Plastics Today for Your Molding Needs
At OMICO Plastics, we specialize in custom plastic blow molding. However, we maintain the capacity to provide our clients with injection molded parts through our partnerships with trusted, local injection molding companies. Although the automotive industry is our primary focus, we also manufacture quality molded components for toys, pet supplies, appliances, and lawn and garden equipment.
The primary advantages gained from working with the OMICO team include:
- Employment of specialized part inspection equipment (for more effective quality control)
- Use of the purest polyethylene (PE) AL55-003 plastic purchased directly from the manufacturer (for greater production consistency)
- Commitment to open communication with the customer (we will never switch components or products with approval)
- Streamlined automation (making it easier for customers to get an accurate quote)