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Typical components of rotomold tooling

Cast Aluminum Tooling or Molds

Tooling made from aluminum castings are by far the most common type of rotational molds. They are relatively inexpensive and can be cast, machined, and framed quickly. High quaility castings with low pourousity will produce a wide range of parts with fairly intricate detail, elaborate shapes and patterned finishes. Aluminum tools are well suited to produce air or water tight plastic parts  as well.

Aluminum molds are lightweight, and transfer and dissipate heat well making them ideal for repeated cycles through rotational molding ovens.  Cast tools can be modified after they have been put into production to accommodate slight changes to the parts design.

When your part goes into production, there is no substitute for using a quality mold. A poorly designed or built tool will inevitably lead to slower production runs and mold failure ad lost production time. Sterling Technologies will guide you through the process to ensure you select the right tool for your application.

Below is an overview of a typical tow cavity rotational tool.

This is a two cavity rotational mold producing a large, patterned rain barrel. It’s components include:

Aluminum Cavity
The cast aluminum cavity is built with three sides. In this particular tool, the sides are formed with one seam and the top forms a seam just below the lip of the barrel. This design produces a seam-free top.

Interior Finish
Each mold has a specific texture inside. This ranges from a highly polished, smooth surface to a deep patterned texture which forms the parts surface.

Steel Framework
These molds are filled repeatedly throughout the production run. A steel tube frame provides the structure to fasten the sides of the mold together creating a tight clean seal.

Bolted Fasteners
The steel frame contains regularly spaced spring-loaded fasteners, normally 6 to 8-inch harden steel bolts, to securely close the cavity during the molding cycle. Torque-limited power tools are used to carefully open and close the mold.

Alignment Tracks
Some mold components require precise alignment to ensure a clean seal and to improve cycle times. This mold used a track and wheel design to slide the top of the mold into exact alignment.  

Platform
The framework is welded to a steel platform. This allows the rotational mold to be clamped onto to the machine’s arm so they can rotate freely without obstruction.

Crain Hooks
Each mold will have four even spaced hooks to easily position the mold onto the machine arm.

Rotomolded underground municipal drain

mold heads into production

Rotomolded underground municipal drain

mold heads into production

Molded top detail

This view of the rain barrel shows the "seamless" top detail which holds water. In order to create the seamless top, the tooling has been designed with three sides. Sterling's OneSource engineering team ensures the part is deigned to perform and to be efficiently produced.

Molded top detail

This view of the rain barrel shows the "seamless" top detail which holds water. In order to create the seamless top, the tooling has been designed with three sides. Sterling's OneSource engineering team ensures the part is deigned to perform and to be efficiently produced.

Mold and tooling components

Sterling engineers use a variety of techniques to improve the frame design to speed the de-molding and loading process. Here, alignment wheels have been added to quickly and properly close the mold's top section.

Mold and tooling components

Sterling engineers use a variety of techniques to improve the frame design to speed the de-molding and loading process. Here, alignment wheels have been added to quickly and properly close the mold's top section.

Tooling - top section alingement

Another view shows the mold open with the top section rolled away from the cavity. Designing tooling to improve molding and speed part production is vital to ensuring the lowest total cost of production.

Tooling - top section alingement

Another view shows the mold open with the top section rolled away from the cavity. Designing tooling to improve molding and speed part production is vital to ensuring the lowest total cost of production.

Deep Texture Pattern

An up close look at the decorative rain barrel's deep textured pattern achieved with rotational molding

Deep Texture Pattern

An up close look at the decorative rain barrel's deep textured pattern achieved with rotational molding

50 Gallon Palm Rain Saver

This is the beautiful rain barrel molded from the tooling shown above. They're available in a wide range of colors and have been assembled with spigots and screens by the Sterling team.

50 Gallon Palm Rain Saver

This is the beautiful rain barrel molded from the tooling shown above. They're available in a wide range of colors and have been assembled with spigots and screens by the Sterling team.

Polished Mold Surface

creates a smooth glossy surface

Polished Mold Surface

creates a smooth glossy surface

Tooling to Produce a Textured Part

In this same mold, a reverse pattern is designed into the original aluminum casting to produce a deep weave texture on the part.

Tooling to Produce a Textured Part

In this same mold, a reverse pattern is designed into the original aluminum casting to produce a deep weave texture on the part.

Raod Barrier Mold

Raod Barrier Mold

Rotational Molds

An example of a multi-cavity mold set

Rotational Molds

An example of a multi-cavity mold set

Open Mold Cavity

Twin molds readied to be filled. Note the deep textured pattern.

Open Mold Cavity

Twin molds readied to be filled. Note the deep textured pattern.
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