Your factory direct source for rigid plastic boxes.

How Plastic Boxes are Made at Alpha Rho

Wondering how we make rigid plastic boxes at Alpha Rho? Here’s how the magic happens…

It all starts with polystyrene resin. In its natural state, polystyrene resin is a clear and rigid material, and is delivered in pellet form to our factory in Fitchburg, Massachusetts.

The pellets are filled into a hopper and then fed into the barrel of an injection molding machine. Then the pellets are heated by the barrel’s exterior heater bands, which melt the solid polystyrene pellets into a molten state. Inside the barrel, a rotating screw sends the pellets forward as they begin to melt.

When enough molten plastic is accumulated in front of the screw, it is injected directly into the mold cavity. The molten material is then solidified into the same shape as the cavity’s contour, in this case, a bear-shaped plastic box.


As the mold is closed, water is circulated through the mold to cool the plastic parts. After a set period of time, depending on several factors (size of the mold, size of the finished part, cooling needed), the mold opens, and the part is retrieved.

Some boxes are molded with a cover and bottom at the same time — in which case they are assembled together. Other times, such as if there is a clear cover and a colored bottom, the pieces are molded separately for assembly later.

The plastic boxes are then removed from the machine by a member of our team. These plastic boxes are thoroughly inspected by the team member, who also assembles the cover and bottom, and packages them in a cardboard carton.

As a special service, our team can custom design plastic boxes with our tailor-made printing services to include company branding and colors.

Watch our video to learn more about how our plastic boxes are made:


Why Choose Alpha Rho?

As the largest manufacturer of high-quality rigid plastic boxes in New England, Alpha Rho has been a leading supplier of injection-molded plastic boxes, with a reputation for providing dependable plastic packaging solutions for over 50 years. Our custom rigid plastic boxes – compartment, hinged, friction fit, custom shapes – are used extensively in multiple industries such as retail and hobby, food and confectionary, medical and industrial.

We offer reliable service to meet your needs. You can check out our list of products here, or request samples today and experience the quality of Alpha Rho’s products first hand.