Advantages Of Rotational Molding

advantages of rotational moulding

There are many advantages of rotational molding compared to other plastic molding process methods. Most manufacturers of hollow type plastics usually prefer this the most in producing their products. Other terms used to refer to the process are roto-molding and roto-casting. Slush molding is also used in liquid-vinyl which is also a similar process. Rotational molding has several benefits attached to it and some of the major ones include; low residual-stresses levels and cheaper molds. The process is well known for tanks manufacturing but is also used to create complex medical products and high level aesthetics point-of-sale products.

Wide Variety of Rotational Molded Products.

Rotational molding can be used to produce almost any product that you want. It can be used to make simple items such as toys, or more complicated items like medical devices. This method is very versatile and can be used to produce anything from large scale objects to small scale objects, such as:

  • Oil Tanks
  • Septic Tanks
  • Fuel Tanks
  • Shipping Tanks
  • Storage Tanks
  • Leisure Craft
  • Rowing Boats
  • Portable Toilets
  • Road Signs
  • Tornado Shelters
  • Road Barrier
  • Furniture
  • Appliances
  • Automotive parts
  • Medical devices
  • Kitchenware
  • Sports equipment
  • Toys

They are made using different materials depending on their intended purpose. For example, some toys are made out of polyethylene terephthalate (PET) or nylon. These plastics have high strength and durability. Other toys are made out of ABS or PVC. These plastics are softer but still strong enough to withstand rough play. Most materials that are used in rotational molding are from the polyethylene group (about 80%), with the most common among them being: Cross-linked polyethylene (PEX) Low-density polyethylene (LDPE)

So Let’s Look at Some of the Key Advantages of Rotational Molding

1) Size Options:

The process has a wide range of sizes and fits any size from the tiniest to larger sizes; this means that there is a room for flexibility as compared to other systems. The manufacturing process can be done on a small Ping-Pong sized plastic to even 21,000 gallon-tanks. Many manufacturers of the moldings are able to make a gallon of between 0 to 1000 pounds and as high as 17ft. This is a big advantage since different sizes can be manufactured using the process, in this aspect the molding can make many sizes to be used for many purposes.

2) Design Advantages:

types of plastic molding processes

It’s very easy to design from unusual shapes to a simple shape using the rotational molding process; this is due to the fact that when the hot plastic or compounds are put into a mold, they will take the shape of the mold as it adheres to the mold wall, which makes it ideal for complex shapes and creativity since any shape can be made from the process. Other types of molding processes are rigid in nature with few options, but the rotational molding can provide a lot of variety of rotomolded products in the manufacturing phase. Also to keep in mind is that there is more room for plastic designs in the process when compared to the blow molding method. Rotational molding can be used to manufacture many complex designs and shapes especially moving sections. Besides it has uniform-thickness of its walls, which is a distinct advantage in designing different shapes and textured finishes.

3) Inserts:

The rotational moulding process can easily accept metal inserts while producing the product and it also allows the possibility for additional threading inserts. All these can be processed at very low costs, as compared to other methods which are cumbersome. Assemblies techniques can be easily altered in the rotomoulding process, which offers the aspect of lower costs and durability in all dimensions. Other U.S. manufacturing methods don’t readily take inserts and this alone can make it more costly than the former.

4) Color Sectioning:

Color sectioning is much easier with this rotomold process and the color-blending can be done in-house to a variety of shades. The color matching is easily done on the rotational molding without extreme volumes; any pattern imaginable can be created with this process. There are a number of colors which can be achieved and at a lower cost. Some of the colors which are available include; sandstone, marble and other color varieties.

5) Quality Surface Finish:

The process offers high quality surface finishing capabilities by exactly taking the shape of the particular mold plus the texture. This makes room for very high gloss quality finishes on the product surface on the finished product. It also can reflect smoothness and quality artistic product design and take on a high oriental texture finish on its surface.

6) Decorations in Mold:

The rotomolding process takes any authentically designed decorations which are made in the mold and will feature it on the plastic in a vibrant manner. The in-mold techniques used to decorate and design graphics are a by-product of the rotational molding process. The unique design of graphics will stick permanently in the final rotational plastic product. This method makes it possible for items like serial numbers, bar-codes and colorful logos to be molded easily. They often appear and are better quality as opposed to the traditional ones.

7) Quick Tooling:

rotomolding over blow moldingAmong the advantages of rotational moulding is the process of quick tooling. The reason is, the process is slow-pressure without any need of ejection or in-mold cooling. The cast aluminum manufactured molds are very easy to use especially when cooling. The tooling process offers less expenses and production costs when aluminum is involved. A new tooling-process takes about 4 to 10 weeks depending on the design and complexity involved. Multiple hollow molds are also manufactured easily by aluminum casts. The actual fact is that the other molding processes like the blow-molding and others can be expensive and complicated. For variety of designs and even graphics, rotational molding has an upper hand. Bottom line is that with the top advantages of rotational molding

Rotational Molding Advantages and Benefits

Again rotational molding is a process that is different from other methods of manufacturing, such as blow molding and thermoforming. In roto molding, the resin melts into the the mold surface instead of being forced into it by pressure. Rotational molding operation has some advantages over other plastic molding methods, but it also has disadvantages.

Plastic Rotational Molding Benefits

  • Low Cost Tooling: You can use cheaper metals, like aluminum and stainless steel to make the tools. This is because the pressure is lower than normal.
  • Consistent Wall Thickness: the constant rotation of the mold coats the walls evenly for uniform wall thickness during both the heating and cooling manufacturing.
  • Double-wall Containers: They can have double walls with uniform wall thickness without needing to be processed twice.
  • Can be Molded as One Solid Piece: This means that the parts do not need to be welded or attached separately. Helps create a stronger part.
  • High Stability: The molding material is not exposed to external pressure, which makes it more stable and reduces the chance of defects in the finished part.
  • Long Lasting Durability: With the roto-molding process the corners will be thicker and less likely to fail and break from stress.
  • Design Flexibility: The metal used in the rotational molding tooling is easy to work which allows a lot of details to be inserted. You can do things like add logos, textures, symbols or lettering into the finished product.

Plastic Rotational Molding Disadvantages

  • Long Process Cycles: Rotomolding production runs can take up to three hours to produce one part. The parts are made at eight rotations per minute.
  • Limited to Poly-Based Resins: Rotational molding requires a type of material that can be easily turned into a plastic powder and it must also be able to withstand extreme temperatures. There are only a few types of poly-based resin materials that will work for this process.
  • Costs Higher for Materials: It is hard to find materials that have the right amount of thermal stability, and also have good additives. The material has to be ground up too.
  • Lack of Consistency: The soft metal that is used to make the machine tools can only be used about 3,000 times before it needs to be replaced or refurbished. This could cause a lack of quality in the work because of limited consistency with each cycle in the molding process.
  • Possible Higher Labor Costs: Mechanization and automation have not been fully realized yet for production process. It usually requires more labor intensity than comparable to other manufacturing processes.

Rotational Molding Process

There are two types of rotational molding: continuous and semi-continuous. The process begins with a heated metal mold which contains the shape of the part being produced. A liquid resin is then injected into the mold. As the resin cools, it hardens around the walls of the mold. Once the mold is removed from the machine, the finished part will be ready to use.

Continuous Rotational Molding

In continuous rotational molding, the mold remains stationary while the resin is injected into the cavity. After the resin has hardened, the mold opens and the finished part is ejected.

Semi-Continuous Rotational Moldings

In semi-continuous rotational molding, both the mold and the resin move during the process. Injection occurs at the same rate as the movement of the mold and resin. When the mold reaches its final position, the resin solidifies. Then, the mold moves away from the resin and ejection occurs.

Rotational Molding Equipment

Rotational molding machines come in various sizes and configurations. Some are designed for small batches of parts while others can handle larger volumes. There are also single-shot and multi-cavity machines available. Single shot machines are ideal for making prototypes or small runs of parts. Multi-cavity machines are best suited for mass manufacturing.

The most common rotational molding equipment includes the following components:

• Metal molds

• Plastic injection system

• CNC controller

• Computerized numerical control (CNC) machine

• Programmable logic controllers (PLC)

• Hydraulic systems

• Electrical systems

• Safety systems

• Quality assurance systems

• Inspection systems

• Production management software

• Data

Rotational Molding Machines

There are several different types of machines that manufacturers use to perform rotational molding. Some of these include:

• Single screw extruders

• Double screw extruders

• Twin screw extruders

• Horizontal twin screw extruders

• Vertical twin screw extruders

Single Screw Extruder

A single screw extruder is a device that consists of a barrel, a feeder, and a screw. The screw is located inside the barrel and moves back and forth as it turns. When the screw reaches the end of its travel, it pushes the melted resin out through the exit port.

Double Screw Extruder

A double screw extruder is similar to a single screw extruder except that there are two screws instead of one. These screws work together to push the melted resin out of the barrel.

Twin Screw Extruder

This type of extruder works by pushing melted resin down a channel. At the bottom of the channel, there is a second channel where the melted resin flows into another channel. This continues until the melted resin comes out of the exit port.

Horizontal Twin Screw Extruder

In this type of extruder, there are two channels on either side of the barrel. One channel feeds melted resin into the other channel. Both channels move at the same speed so they meet in the middle.

Vertical Twin Screw Extruder (VTSE)

This type of extrusion system is similar to a horizontal twin screw extruder but instead of moving horizontally, it moves vertically. This allows the melt to flow up and down rather than sideways.

How Rotational Molding Works

Rotational molding is a process used to make hollow articles from thermoplastic materials, such as polyethylene terephthalate (PET). This process involves the use of an injection-molding machine and a rotary die that has been preheated to about 200° F. The plastic material is injected into the cavity between the heated die and the rotating mold. As the mold

As mentioned earlier, rotational molding uses a heated metal mold to create the final product. After the mold has cooled, the finished product is ready to use.

During the manufacturing process, the molten plastic is forced into the mold cavity. The mold is rotated while the resin is still hot. The rotation causes the plastic to solidify quickly. The mold is then opened and the finished product is removed.

What Is the Difference Between Rotational Molding and Injection Molding?

The main difference between rotational molding and injection molding is the way the part is created. With rotational molding, the material is injected into a preheated mold. Once the mold cools, the part is ejected from the mold. On the other hand, with injection molding, the mold is closed around the material before it is injected. Once the mold opens, the finished part is ejected.

The Benefits of Using Rotational Molding

Rotational molding offers many benefits over traditional methods of manufacturing. Here are some of them:

• Low Cost

• Quick Turnaround Time

• High Quality Parts

• Easy to Use

• No Tooling Required

• Can Produce Small Batch Production

• Good For Prototyping


Plastic Rotational MoldingRotational molding is a great method for creating simple or low-cost high quality plastic parts. However, it may not be suitable for making large quantities of high-quality parts. If you need to make a lot of parts, consider using injection molding.