Rotomolders
"Rotomolder" is one of many names for the large manufacturing machines used to create hollow and seamless plastic parts. They are also known as rotational molding machines, rotomolding machines, or rotational molders. Rotomolders present overall lower costs than other forms of plastic manufacturing, like blow molding, injection molding, or thermoforming, but they are less common because they are quite complex.
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Applications of Rotomolders
Manufacturers use rotomolders to create such products as:
- Large Industrial Tanks
- Water Bottles
- Outdoor Planters
- Construction Cones and Safety Cones
- Pink Flamingos
- Playground Slides
- Helmets
- Footballs
- Pipe Fittings
- Kayaks
Additionally, rotomolders are used in these industries:
- Agriculture
- Automotive Manufacturing
- Chemical Processing
- Construction
- Food and Beverage Processing
- Furniture
- Marine Manufacturing
- Material Handling
- Packaging and Assembly
- Pharmaceuticals
- Plumbing
- Recreation and Sporting Goods
- Toy Manufacturing
- Wastewater Management
Rotomolder Design and Function
A rotomolder typically consists of a mold, rotating spindles, an oven, a cooling chamber, and arms. It is capable of processing a variety of different thermoplastic materials, such as high density polyethylene (HDPE), low density polyethylene (LDPE), nylon, polyethylene terephthalate (PET), polycarbonate, and polyvinyl chloride (PVC).
To work, any one of these plastics are poured in powdered form onto the mold, which is made from stainless steel, aluminum, or both. Once the mold is coated, it is transferred into the oven chamber, where it continuously revolves on the rotating spindles as the metal powder melts and evenly coats the mold walls. Once the metal has completely covered the mold, the mold is transferred to the cooling chamber, where a combination of air and cold water cool and cure the molten plastic. Cooling usually takes around 20 minutes to complete.
After the plastic has dried completely, it is removed from the mold. This is typically done manually. If the plastic has shrunk during the process, as it sometimes does, this part can prove difficult. Regardless, once off the mold, the new hollow plastic part can either be sent on for shipping or sent on for further processing. Common processing procedures they undergo include cutting to size, welding with small components, painting, polishing, and cleaning.
Notable Types of Rotomolders
Rock and Roll Machines
Specially designed with small heating chambers to create long, narrow parts.
Clamshell Machines
Actually a type of rock and roll machine, though it distinguishes itself by its use of a single primary rotational arm (not counting the support arms it usually has on its ends.) Most other plastic rotational molding machines use at least two arms.
Shuttle Machines
Typically have two arms that work independently, moving the mold back and forth in between the heater and the cooler as it turns biaxially. Some shuttle machines do, however, have only one arm. In this case, the arm moves the mold horizontally from the heater to the cooler as it spins.
Vertical Rotational Machines
Smaller than most other rotomolding machines. They are considered small to medium in size. They are valued for their energy efficiency, which comes from their compact heating and cooling chambers.
Carousel Machines
One of the most commonly used rotational molding machines. Carousel machines may have up to four arms and six stations, and they come as either fixed or independent equipment. Typically, fixed arm carousel machines consist of three arms that are required to move together, while independent arm carousel machines have between three and four arms, all which move separately from one another. Both types of carousel machines are available in a wide variety of sizes.
Swing Arm Machines
Can have up to four arms, all of which move biaxially. The arms, which do not all have to be engaged at the same, are mounted on the respective corners of the machine, where they swing in and out of the oven.
Benefits of Using Rotomolders
While there are many other types of molding machines available, the rotomolder stands apart as a machine that eliminates unsightly seams in both small products in large quantities and large products in small quantities. It also creates plastic formations that are uniform in both quality and precision wall width. To find out more, share your specifications with one of the skilled manufacturers we have listed on this page!
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