Rotational molding, which is also referred to as rotomolding can make various types of plastic and metal objects. The process is done by putting power or liquid resin into a mold that rotates inside an oven making the resin melt and coat the mold cavity. After it is cooled, the part is removed and voila- you have your part. Many things are made through this thermoplastic process. For example, rolling laundry carts, recycling carts and plastic pallets for starters.
Types of Rotational Molding Machines
Rock and Roll Machine
This type of rotomolding machine specializes in making long and narrow parts. Most rock and roll machines sport two arms that roll each mold around 360 degrees in one particular direction while tipping and rocking the mold at a 45 degree angle in the other direction. Often times, hot air is used to heat up the mold but that’s usually only done for large parts like rolling laundry carts.
Clamshell machines only have one arm that rotates but it is typically supported by arms on either end of the machine. The unique thing about a clamshell machine is that it heats and cools the mold in the same place. For example, if the rolling laundry carts are being made then the mold would be placed inside the chamber and heated up in order to make the resin melt just like in the rock and roll machine. Once that part of the process is finished, the part is not removed from the chamber but the chamber begins to cool the mode right there. The benefit of this is that the machine takes up a lot less space and cost less to run. The clamshell machine is used in prototyping and higher quality models usually.
The heating and cooling areas are separate in the vertical machine. In between these areas is loading and unloading area. It is located at the very front of the machine. This is probably the most energy efficient machine because the heating and cooling chambers are compact.
This type of machine has the standard two arms that switch the mold back and forth from the heating chamber to the cooling area. However, the arms are independent of one another which means that sometimes only one needs to be used. The best thing about the shuttle machine is that it is the most environmentally friendly. It also cost less compared to the size of product that is produced. This is the type of machine that would be used in schools and for prototyping because it is available on a smaller scale.
Swing Arm Machine
This kind of machine is a little bit different because it can have up to four arms but each arm still functions independently from one another so that you do not have to use them all at the same time if it is not necessary to operate it or make the part. The arms swing in and out of the oven from all four corners. If a product needs a long cooling cycle where a lot of time in order to demold parts and this is the type of machine you would want.
This is known as a bi-axial machine and is probably the most common of its type. Having four arms and six stations, it can be fairly large but comes in a variety of sizes. The carousel machine can be either fixed or independent. A fixed machine usually has three arms that have to be moved together. The independent machine comes with three or four arms that are able to me separately from each other so that it can make different size molds with specific cycle times and thicknesses.
Well there are various different types of machines that can all do similar things, it’s still important to use the correct machine for the product. If you are going to be making something like rolling laundry carts you need to make sure that the way that the cart is heated and then cooled is appropriate for the type of shape and mold that you were using as well as the thickness and durability that you will need.