Molded-In Inserts

Rotational Molded-In Inserts

Molded-In Inserts Rotational Molding

Plastic products like instrument enclosures and electronic housings can use molded-in inserts. However, high-pressure forces, such as compression or injection molding, can cause molded inserts to crack or deform. With rotational molding it reduces the risk of these problems!  Our engineers at follow specific molded in inserts design guide protocol when it comes to molded-in inserts.

Rotational mold in inserts, which are dumbbell-shaped inserts are used in rotational molding to provide anchors for other hardware like handles and hinges. Rotomold inserts are available in many shapes, including square, hex, and one-headed. In addition, threading can make both metric and imperial sizes and Pipe and SAE threads.

Molded-In Inserts Service

How Molded-In Inserts Works

Inserts that have been molded into the mold cavity are installed inside. The insert is then melted and molded around it. The insert should absorb heat from the cavity’s surfaces and conduct it along its entire length. The insert should be shaped so that the plastic material can flow through it.

Selecting Molded-In Materials and Inserts

Rotational molding allows for the use of molded-in inserts made from many materials. Two requirements are essential. The first is that the insert material must chemically be compatible with the plastic material to be molded. The material used in the insert must be able to withstand temperature changes and resist deformation during molding.

Sizes for Insert Molding and Molded-In Inserts

Engineers must choose the right size inserts. The plastic shrinks when rotomolded parts cool. This can result in plastic being pulled down tightly onto the insert, and stress cracking may occur. Smaller inserts are more susceptible to cracking than larger ones. Inserts with sharp edges can also cause stress cracking.

Part Design with Multiple Molded-In Inserts

Special considerations should be made when rotomolded parts have multiple inserts. It is best to keep the distance between inserts as small and manageable as possible. Plastic shrinkage can occur between inserts that are spaced far apart. This can lead to high stresses at the joint between plastic and insert. In addition, it can make it difficult to remove the final plastic part from the cavity.

Rotational Molding: The Process & Advantages

Rotational molding, also known as rotomolding, is a plastics molding technology used to create hollow products. It is a casting process, but unlike most other plastics processes, there is no pressure involved. As a result, molds are inexpensive since they don’t have to withstand pressure. In addition, it allows for small production runs, which are more economical.

Rotomolding can be used to create a wide range of products. It allows product designers great freedom since almost any shape can be made. There are many applications and almost no limits to the sizes of moldings.

The Process

Rotational molding is a simple concept. First, in powder form, the plastic material is placed in a hollow mold. The mold is then closed and slowly rotated on two axes. Next, it is heated in an oven and rotated.

After the polymer powder is fully melted, the mold is moved to a cooling station. Once cooled, it can be re-used with water or air. The part will solidify as the mold cools. The process is stopped once the material has cooled enough to come off the mold surface. De-molded means that the product is removed from the mold.

Rotational molding may seem simple, but anyone who has been involved in it will tell you that it can be highly complex. It is a casting process that involves no pressure involved. Because of this, the material can’t be controlled the same way in high-pressure processes like injection molding. As a result, many variables can impact production and end-product quality, including ambient temperature, humidity, type, mold specification, and powder quality.

Plastic Materials

Today, the industry is heavily dependent upon Polyethylene (PE); 97% of all rotomolded products are made. The most popular polymer in the industry is Polyethylene. It’s versatile, moldable, and readily available. Rotational molding, a casting technique where the powder is almost always used instead of granules. The material must be ground. At ambient temperatures, Polyethylene is relatively easy to grind.

Because the process is slow and aggressive on other polymers, it has hindered the development of new polymers. PVC (usually in liquid form plastisol), Polypropylene, and Polyamide (PA6, PA11 & PA12). These non-Polyethylene materials can be difficult to grind. Most of them need to be ground into powder by cryogenic grinding and are more expensive than freezing. The industry is seeing a positive increase in R&D.

The Key Advantages of Rotational Molding

The advantages of rotational molding is the many unique characteristics that are not available in other molding processes.

Low tooling costs.

Since it’s a casting process, so there is no pressure. As a result, molds can be inexpensive, and low-volume molds can be economically viable. Rotational molding is an excellent option if you have an excellent idea for a product but don’t know how many to sell or need a low production run.

It is easy to create complicated shapes. Rotomolding can accommodate production complexities like stiffening of ribs and molded inserts.

Uniform wall thickness

Rotational molding ensures uniform wall thickness.

With corners being thicker, it increases product strength and integrity. However, other processes, such as blow molding, can stretch the molten material around corners and sharp edges, creating weaknesses.

The investment is minimal, and the process offers great production flexibility.

There are few limits to the sizes of products, and multiple products can be molded simultaneously.


Versatile technology that can create a wide range of moldings

Rotational molded products can be used in many sectors. These are the key areas:

  • Tanks to store water and chemicals up to 50,000 Liters
  • Material handling products include containers, crates, pallets, and insulated fish and cooler containers.
  • Environmentally friendly products include litter bins and bollards, litter cones, road cones, and traffic dividers and road signs.
  • Floats and buoys.
  • Automotive use includes truck mudguards and ducting, diesel fuel tanks, toolboxes, and tractor dashboards.
  • Kayaks, canoes, and boats
  • Outdoor products such as furniture, garden planters, and other accessories.
  • Toys and playground equipment

These traditional areas have seen a significant increase in demand for new, design-led products, such as interior and exterior objet-d’art, lighting, and high-end decorative items.

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