A Beginner’s Guide to the Blow Molding Design Process

You’re ready to have your part designed by a blow molding supplier. What’s involved in blow molding product design process?

Here’s an introduction to the steps your blow molding designer will take to bring your product to life.

Create a mockup of the part.

The first step is to create a mockup of the part. Most projects start with an idea or a sketch. Then, the blow molding design team creates a three-dimensional CAD or e-drawing of the part.

The e-drawing allows you to:

  • Visualize your part accurately before your supplier creates a physical model or mold.
  • Rotate and measure a virtual model of your part to determine the initial dimensional

expectations.

  • Make modifications to suit your design preferences.
  • Address functionality and structural issues right out of the gate.
  • Ensure your product goals and your supplier’s production goals are precisely aligned.
  • Develop cost estimates for the part and the mold based on the material, quantity, quality, and timing desired.
  • Verify the product meets your stated commercial goals, from functionality to aesthetics, to optimize the potential for market success.

Design and build the mold.

A high-quality blow mold is the foundation of manufacturing your blow molded part. Your team will review mold design details to ensure ease and efficiency in production:

  • Blow methods. Blow molding is an umbrella term for many more specific processes, including injection blow molding, stretch blow molding, and extrusion blow molding. Each offers unique capabilities and requirements. For more info, check out this introduction to the major types of blow molding.
  • Materials. Review mold materials, construction techniques, and quantity expectations for the new mold.
  • Cooling needs. Each mold will be equipped with water lines for cooling. In the blow molding process, cooled water brings down the temperature of the mold walls. This causes the hot plastic inside the mold to harden against the mold walls.
  • Ejection requirements. Beyond cooling, the shape of the product also influences its ability to be ejected. More complex shapes, such as those that fold in on themselves, may require molds with moveable hydraulic or pneumatic parts to ease ejection.
  • Shrinkage. Because hot plastic shrinks when it cools, your mold will be larger than the final part. Your blow molder will determine the exact difference in size based on resin type, thickness, cooling requirements, and overall structure.
  • Pinch-off. The mold must also provide the pinch-off, which defines the part perimeter shape and separates the excess plastic around the blow-molded part. This pinch-off facilitates the blow molding process by trapping air in the molten plastic parison, which inflates to force the plastic against the sides of the mold.

You will also review the blow molding design before the mold is put into production. This will ensure your product vision is aligned with the production process.

Run quality checks.

Once the mold is designed, built, and approved, your product goes to production. Throughout the process, your blow molding team will conduct regular, intensive quality checks to ensure smooth sailing.

  • Establish the quality parameters through process capability studies that will assure repeatable quality in production.
  • Monitor the physical requirements of the manufacturing process.
    • Continuously monitor that the heated resin has reached the right temperature and viscosity for molding.
    • Ensure the resin is blowing consistently throughout the mold at a consistent part weight.
    • Maintain the desired cooling temperatures.
    • Check for leaks (blow-outs) and other warning signs of malfunction.
  • Evaluate product quality and consistency using state-of-the-art technology:
    • Visual inspection systems
    • Colorimeters
    • Sonic meters
    • Specialized gauges
    • X-ray analyzers

A good blow molding supply team is dedicated to getting every piece right for you, the first time around.

Interested on how your design team enhances your product? Check out our blog on how your blow molding supplier optimizes your product design.