Rotational molding involves a heated hollow mold which is filled with a charge or shot weight of material. It is then slowly rotated (usually around two perpendicular axes), causing the softened material to disperse and stick to the walls of the mold. In order to maintain even thickness throughout the part, the mold continues to rotate at all times during the heating phase and to avoid sagging or deformation also during the cooling phase. The process was applied to plastics in the 1950s,but in the early years was little used because it was a slow process restricted to a small number of plastics. Over time, improvements in process control and developments with plastic powders have resulted in increased use.
Rotocasting (also known as rotacasting), by comparison, uses self-curing resins in an unheated mould, but shares slow rotational speeds in common with rotational molding. Spin casting should not be confused with using a high-speed centrifugal casting machine to shape self-curing resins or white metal.(From Wikipedia)
Rotational molding uses hollow metal molds of either aluminum or steel.Molds can be cast,machined or fabricated.
The first step in the process is to load a pre-measured amount of powdered resin int the mold.The mold is then closed using either bolts or clamps.
Next,the mold is moved into an oven where it rotates slowly about two axes simultaneously.It is this biaxial rotation which allows the mold to be evenly coated with plastic yielding inform wall thickness.
The speed of the biaxial rotation can be adjusted to suit the shape and complexity of the part.The powder material is not centrifugally thrown against the walls of the mold but the mold actually runs “through”the pile of powder resin.
As heat is transferred through the mold, the resin powder melts and adheres to the mold surface building up layers of plastic.
During the molding cycle the mold goes from ambient temperature to a few hundred degrees.This causes an air pressure build up inside the mold.
In order to minimize the air pressure build up,a bent is added to allow the expanding air to exit the mold.After the cooling cycle the vent is removed.
When all of the material is evenly melted and distributed,the mold is then sent to a cooling chamber.There,while continuing the biaxial rotation,the mold is cooled with air,water mist,or a combination of both.The temperature is lowered gradually and the plastic is solidfied into its final shape.
When the mold and part are sufficiently cooled the mold is opened and the part is removed.
In summary the mold goes through the oven cooling chamber and then the load and unload station.This complete process generally takes one hour.
Molded-in inserts can also be easily added to the molded part.An insert is held in plastic by a bold through the mold wall.The insert is completely coated during the molding process.Before de-molding the part,the bold is removed and the insert is left in place.
Similarly,inserts which form undercuts can be molded into place.
Polyethylene,which is used most often in rotational molding,is nototriously difficult to decorate.The nature of polyethylene doesn’t allow anything to stick to it.Graphics which can be molded in to the part have been developed.These graphics are molded directly into the outside layers of the part.
The graphic is applied to the mold and then molded into the part.It cannot be rubbed off or washed off with chemicals.It becomes a permanent feature of the molded part.
Rotomolding machine has arms,oven,we have a lot of sizes to make different products.
Rotational Molding Advantages and Disadvantages
Advantages of rotational molding
Rotomolding technology is prevalent, making it one of the rapidly growing industries in the last decade. There are numerous advantages of rotational molding, from design versatility, reduction of environmental impact, use of lighter materials, and meeting of demand. Why choose rotational molding as the best technology for your next plastic projects? Below are a few advantages that every part designer should be aware of.
The materials used are long-lasting and flexible
At Roto Dynamics, our rotomolded plastic products are made from polyethylene protected from the hazardous UV Rays from the sun. As you all know, Ultraviolet rays from the sun make products to fade quickly and degrade with time. Unlike metals, rotomolded plastic is free from rust, and they do not corrode easily, meaning that your products will be durable. Besides, the products made from our roto molding company are powerful since the walls are thick; hence, they are not easy to break.
Minimum environmental impact
One of the rotational molding advantages is its minimum environmental impact. During the rotomolding process, no chemicals or dangerous toxins are released hence making it environmentally friendly. Unlike metals and concrete, very few materials are wasted when manufacturing is done using plastics. One fantastic feature about plastics is that they are 100% recyclable hence simple to reduce your carbon footprints. This means that for every plastic item that is recycled, fewer materials are mined from the earth, therefore, reducing its impact on the environment.
Wide range of designs
With the rotomolding process, it is simple to generate a variety of shapes, majorly because when hot plastics are placed on a mold, they take the shape of the mold. Many molding processes have few options to choose from, but with rotomolding, any form can be designed from the process. This makes it ideal to be used in many industries. Our roto molding company provides you numerous designs of your choice.
Variety of size options
Compared to other molding processes that accommodate a few sizes, rotational molding allows for diverse sizes to choose from. At Roto Dynamics, we manufacture small-sized tanks, medium sizes, and even the largest sizes. We can design a gallon of between 0 – 1000 pounds with a height of approximately 17ft. The main advantage of creating various sizes is to allow the tanks to be used for different purposes.
The initial production cost for rotational molding is way cheaper compared to other molding processes. The low cost incurred is for machining the mold. Before heating, the mold requires finished pieces added to it like color plastics, internal pipes, and metal threads. This saves you both your time and money.
The production process takes a shorter time
Another rotational molding advantages is the process time. Compared to blow molding or perhaps injection molding, rotomolding takes a shorter duration of time. The speed at which we can produce rotational mold, makes it ideal for quick orders or rush orders. For instance, in our roto molding company, production can start in three months or less.
Disadvantages of rotational molding
Like any other plastic molding process, rotational molding has its share of disadvantages, which include :
Few material options
One of the disadvantages of rotational molding is that you have less material options. The raw materials we use in rotational molding must be changed from granules to a fine powder and excellent thermal stability. The only material suitable to be used in the process is resin.
High process durations
The rotational molding process can take as long as one hours to complete one section involving eight turns.
The astounding expense of crude oil material
The cost of crude oil is high because of the costs incurred in converting the materials to powder and the added materials.
High work costs
The use of robots in rotomolding has not been proclaimed hence requires a large workforce to take care of the operations. The cost incurred in paying the workers is high, which would have otherwise been made easier if robots were doing the work.
At our Roto molding company, Roto Dynamics, we offer an amazing portfolio of rotomolded products like water tanks, and plastic products. Our products are very durable and robust mostly since the materials are made from rotomolded plastic which is durable. Rotational molding has both advantages and disadvantages, as mentioned above, although the disadvantages are less compared to the advantages. For more information or clarification, contact us at Roto Dynamics, and we will be at your disposal.
We Help Customers Design And Produce Their Own Unique Products And Establish Uniqueness In Different Fields.
Cixi Youte Plastic Container Co., Ltd. has a long history employing more than 20 years of senior experts in integrating molding,hollow foaming and seamless technology and has been one of the best manufacturers in China.
It is an enterprise that integrates designing and manufacturing of all kinds of rotomolding products which have been widely used in military equipment,enterprises and institutions,hotels,medical treatment,transportation,sports venues,outdoor places and special requirements.
Their products such as dry ice box,cooler box,military box and other rotomolding products have been sold to most European countries,Australia,the United States,Malaysia,Chile,Viet Nam,South Africa and many other countries.
The company adopts imported LDPE special rolling plastic raw materials and advanced rolling plastic process technology,which is formed in one time and has the advantages of high structural strength,impact resistance,wrestling resistance,super airtight and durable.
Our special products:
Cixi Youte plastic container Co.,Ltd is located in No.199, Hede Road,Cixi Binhai Economic Development Zone, Zhejiang Province.
With the development of rotational molding products in global, our company was established in 2011 by meticulous preparation, strict demand, and considerate service. There are many professional workers, who has more than 20 years experience of rotational molding mold and manufacture.
Every rotational molding products must be inspected carefully while molding, installing and packing. Any defect products can not be allowed to delivered to our customers.As a company, and as individuals, we value integrity, honesty, openness, personal excellence, constructive self-criticism, continual self-improvement, and mutual respect. We are committed to our customers and partners and have a passion for rotational molding products.
We take on big challenges, and pride ourselves on seeing them through. We hold ourselves accountable to our customers, shareholders, partners, and employees by honoring our commitments, providing results, and striving for the highest quality.Until now, we have some typically products, such as military box,dry ice box,tool box,buoy,floating box.
All of them are very popular in domestic market and middle east. Meanwhile at the same time, we stick to design some new model every year to develop market and service well. We,YOUTE, warmly welcome all of you to visit our booth and factory. If you have any idea about our products, please feel free to contact us. All of staffs of YOUTE will try our best to offer the best rotational molding and best service for you.
Q1: What is the regular MOQ for your product ?
A1: Our MOQ is according to the product.Always,we support sample order for existing products,but for new products,we have to make mold at first,you have to pay the mold cost.
Q2: What’s your payment term?
A2: T/T or L/C. Other payment terms also can be discussed.
Q3: Delivery date ?
A3: For the mold,delivery time is 25-30 days,and we produce 20-24 pcs products a day with one mold.If you need big quantities,you need more mold to produce them.
Q4: How does your quality control ?
A4: We have professional QC term, control the quality during the mass production and inspect the finished packed goods.
Q5: What can you get benefit from us?
A5:We can offer one-year warranty for you.I assure you that you can enjoy our after-sales service.