Concept Sales Inc.

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Phone: (605) 528-2700

CSI Address:
508 Patrick Ave.
Hartford, SD 57033


Rotational Molding

Den Hartog Industries

Rotational molding, otherwise known as roto-molding, is a process of plastic manufacturing that produces hollow parts. Although the parts come out of the mold as a hollow piece they can be trimmed or cut to create anything from a speaker housing to a dog house.

Rotational Molding Overview

Roto-molded products are produced by melting a measured amount of plastic resin in a mold. As the mold is heated up it rotates on at least two axis, which disperses the melting plastic over the inside walls of the mold. When the plastic has been heated to the correct temperature and has stuck to the inside of the mold the heat is removed and the mold is cooled. The mold is then opened when the plastic has reached a solid state and the part is removed. From there the part can be trimmed to the specifications of the customer or simply packaged and delivered. The simplicity of the process allows for a mold which is fairly simple itself, meaning a rotational molding mold is much cheaper than other forms of plastic manufacturing. It also means that very large molds can be made, which in turn will produce larger parts than most other processes. Although roto-molding lends itself to cheaper tooling, the parts themselves can run a little more as the process takes much longer to create a single part than, say, blow molding or injection molding. This means that roto-molding is a great choice when lower quantities of around 500 or less annually are needed.

Pros and Cons


  • Lower mold cost
  • Ability to produce large pieces
  • Low initial investment
  • Good for lower quantities


  • Higher price per piece than other processes
  • Difficulty of doing larger part runs

Our Capabilities

  • In-house design with 2D, 3D and solid modeling capabilities.
  • 20 Rotational Molding machines (Ferry 190 through 550).
  • Ultrasonic thickness measurement tools, CNC coordinate measurement tools, leak test detection systems, first article inspection and reporting services, custom tailored quality audit programs.
  • Delivery fleet serving the continental U.S.