What Is Blow Molding?

Find out why we love this process

We are the founders of the Double-Wall Blow Molded Case

But what are the origins of blow molding?

Blow Molded Cases

Developed in the late 1930s, blow molding is a manufacturing process that is used to form hollow plastic parts. It is most commonly used to make plastic bottles. In principal, the basic blow molding process is similar to glassblowing. Plastic resin (pelletized raw plastic material) is melted and formed into a hollow tube or parison which is then placed into a mold. The parison is then inflated using compressed air to form a finished part.

In the early 1960s, PFC founder Peter T. Schurman realized that he could combine two hollow blow molded parts to form the lid and base of a portable container or enclosure, and the “double‐wall blow molded carrying case” was born.

Compared to many other industrial operations, blow molding double‐wall cases is a surprisingly simple process, yet one that yields amazing possibilities.

A familiar material you encounter every day

PFC cases are made of high density polyethylene (HDPE). Polyethylene is the most common of all plastics. It is frequently used to make plastic bags, plastic bottles, and food containers. As a thermoplastic, it softens and becomes pliable (and moldable) when it is heated, and it hardens and becomes rigid when it cools.

blow molded case
blow molded case foam interior
blow molded case with foam
blow molded case with label
blow molded cases
blow molded plastic
custom color blow molded case
blow molded plastic cases

What are the benefits?

In the United States, polyethylene is made from clean and plentiful natural gas. It contains no BPA or other toxic materials, and there are no known hazards associated with HDPE plastics. H.D.P.E. is fully recyclable.

  • Blow molded plastic cases are durable, no other material even comes close when it comes to impact strength
  • Double wall construction provides a cushion of air between the walls to help protect your product
  • Blow molded cases are resistant to solvents, oils and moisture
  • Blow molded plastic cases will never rust or corrode.
  • Color is molded in, so it will never chip, peal, rub off or fade
  • Scratch resistant Mold-Tech™ exterior finishes stay looking good, even after years of hard use
  • Mechanical latches and hinges are designed for long-term durability
  • HDPE is durable and is not affected by changes in weather
  • HDPE is resistant to solvents, oils and moisture
  • HDPE Blow Molded cases won’t dent, rust or corrode
  • HDPE plastic is recyclable
  • HDPE is stronger than standard polyethylene, acts as an effective barrier against moisture and remains solid at room temperature
  • It resists insects, rot and chemicals
  • It is easily recyclable and can be used again and again
  • Recycled HDPE creates no harmful emissions during its production or during its use by the consumer
  • During its manufacturing process, HDPE leaks no toxic chemicals into the soil or water

  • Strength

    Because integrally molded interiors are part of the case structure itself and not glued or snapped in later, the overall case is stronger and more shock absorbent.

  • Product Protection

    The air space between the double walls prevents shocks to the case exterior from being transferred to the case interior – providing superior case protection.

  • Economy

    The exterior and the interior of a double‐wall blow molded case are molded as a single piece. That means that an interior designed specifically to package your product is integral to the overall structure of the case – not a separate insert that is made separately and installed later. That makes them surprisingly affordable.

  • Utility

    The air spaces between the double walls are extremely useful. In the top or “lid” of a case, that air space is often used to store product manuals, forms/checklists, and marketing materials. In the bottom or “base” of a case that air space is an ideal place to store ancillary items – things like cables and hoses can be easily “stuffed” into a cutout to hold them securely in place. Impacts to the case exterior are not immediately transferred to the case interior.

Process Steps

Visualize what happens inside the mold: Imagine holding a deflated balloon between your thumb and forefinger and lowering it down into a large glass jug. If you then blow up the balloon, the balloon will fill the jug and take on its shape.

  • First, HDPE pellets are melted and extruded to a consistency similar to modeling clay and then extruded (pushed) to form a hollow vertical tube of molten plastic called a parison.
  • Next, the parison is then pinched closed at the top and bottom to, in essence, create a balloon or bag.
  • The parison is then placed between two halves of an aluminum mold.
  • The mold is closed to surround the parison.
  • A hollow needle inside the mold punctures the parison, and compressed air blowing through the needle inflates the parison inside the mold.
  • The parison takes on whatever shapes and/or contours are on the inside surface of the mold.
  • When the parison cools, the mold opens and the finished part is removed and any excess material is trimmed off and recycled.

Interested in finding out how PFC can help you?

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