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History of Plastic Moulding

The injection moulding is a process for manufacturing a product by injecting molten material into a mould. The material of the mould is mostly metal.

In this process the material is injected into a heated barrel and mixed and then injected into a mould. After injected into a mould the material is cool down and gets it strength. The mould is mainly made with metals like aluminum or steel.

The first injection moulding machine was patented in 1872 by an American inventor John Wesley Hyatt and his brother Isaiah. The design is basic and much simpler than current machines.

The machine uses a hypodermic needle, use plunger to inject plastic into a heated cylinder to the mould. It is used to made products like buttons, combs and collar stays.

The growth of injection moulding products gets hike after American inventor James Watson Hendry invent the screw injection moulding machine. With this technique, the materials can be mixed to get the desired product before an injection. Today all the modern day machine uses screw injection.

How PLASTIC Moulding Works

The moulds are closes. After that, the heated plastic material is injected into mould. When the melted material is entered into mould the air flows through vents in injection pins.

After the mould is filled the mould is left for some time to be cool and the time is fixed for hardening the material. This time depends on the resin is used and the thickness of the product. Every mould has internal cooling lines where water flows continuously to maintain the constant temperature.

In the cooling process, when the resin cools down the screw barrel retracts the material from the hopper. The next step is the mould is open and ejects the ready product. There is a large tub or bin to collect the ready product.

Material Use In Moulding Process

Now which material we can use? The most of materials are polymers generally known as resin and also thermoplastics, some of the thermosets and some elastomers. After 1995 the total numbers of injection moulding materials are increased at 750 per year. There are more than 18000 materials are available.

The materials are generally alloys and are a mixture of materials. It is depending on the product designer that which material they choose. Mostly the materials are choosing on the basis of strength, costs and other properties like when the material bent, heat deflection and water absorption.

The common examples of thermosetting plastics are epoxy and phenolic and the thermoplastic is nylon, polyethylene and polystyrene.

Machine For Moulding

The machine for injection moulding contains a material hopper, a screw-type plunger and a heating unit.

Use of Mould in Moulding Process

There is also used a mould commonly known as die is used to make plastic products.  There are various materials are used to make a mould. The manufacturing cost of a mould is very high and steel moulds are more costly. The materials used for making mould are hardened steel, pre-hardened steel, aluminum and beryllium-copper alloy.

There is a difference between mold and mould but only in spelling, the meaning is the same. The mold is commonly used in American English and meaning is to form the material as mold and the fungi which are developed on fungi. The Mould is British spelling and they don’t use the mold. The mold and mould have the same meaning with a different spelling.

So When using the mold?

The mold can be used as a noun or a verb.

Sometimes mold as a noun meaning fungus that grows on organic matter. Look at this sentence.

I want to eat bread which I made a week ago but it had mold on it.

Mold is also used in a process where liquid turns into solid. Look at these sentences.

The molten plastic poured into mould to get proper shape and size.

The new mold is required for the new design.

Sometimes it is used as a verb as transforming from.

We can mold everything as per your need.

Now, what is the meaning of Mould?

The Mould is mostly used in British English. It is used the same as mold in British English. The difference is only in spelling but the meaning is the same at both places.

In the end, what are mold and mould? Both are the same but use at a different place.

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The extrusion process is used to manufacture those parts, food containers, pipes, garden accessories etc. In this process, the thermoplastic raw material is added from the top hopper into the barrel. The other additives like colorants and UV inhibitors are in liquid or pellet form used and added into a hopper with resin. The manufacturing process is the same as plastic injection molding just this is the continuous process. The injection molding has a similar profile and is in the similar length and the finished product comes from the die and in this process, the fluid is extruded from dying.

Related Article:

Plastic Blow Moulding

The material is fed from the hopper and it reaches to barrel and come in the contact with the screw. The screw is rotating and push the resin ahead into the barrel and heated to set temperature depends on a resin. In the process, a heating profile is set for a barrel to use three or more PID (proportional-integral-derivative) controlled heat zones that increase the temperature time to time of the barrel at the rear where the resin enters to the front. This setup melts plastic resin gradually as the resin flows ahead in the barrel and minimize the risk of overheating which is harmful to product quality. 

At the front of the barrel, the resin leaves and moves ahead through the reinforced screen to remove contaminants. The breaker plate provides extra strength to screen as the pressure is very high around 5000 psi. After a pass from breaker plate, the resin enters into a die. The die gives the shape or profile to the final product, the products have the designed properly as the melted plastic flow through the cylindrical profile to get product’s shape. The flow must be continuous if it is not the product is produced with unwanted stress at some points. This problem cause warping above cooling. We can get any shape if it is a continuous profile.

The cooling process is must required and completed with a water bath. As the plastic is thermal insulated and it is not quickly cooled as steel. The plastic took more time to cool than steel. In the pipe, a sealed water bath is done in a controlled vacuum to keep the shape of the pipe from collapse. There is a set of cooling rollers is used in sheet extrusion process for cooling as it comes from the extruder. The plastic extruders are used for recycled plastic waste or raw material after sorting, cleaning and made it suitable for resin pallet used by the plastic industry.

There are various products are made with extrusion molding. The PVC water pipes are made with extrusion molding. The long cross-section shapes are made with extrusion molding. The insulation on the electrical wire is made with extrusion. The wire is stretch through the die and the insulation is then extruded.

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The more and more companies try to make light-weight containers by reducing the weight of containers. The main challenge is to engineers have to design light-weight container without losing aesthetic of container, impact performance, top load requirement and most important stability. The research took a long time to make perfect light-weight containers. For last few years’ manufacturers of blow moulded containers try to reduce the weight of the traditional design of dairy, water and juice. When reducing the weight of container the main factor to be considered is gram weight.

The reducing process is very difficult as the researchers have to starting with an existing design or they have to make a new design. The process is start with analyzing the current weight of the container and other factors like volume capacity, top load, and drop impact with wall mapping of the entire container. The problems has found after the destruct test. If there is a new design of the container there are two steps to follow. One is passing through FEA (Finite Element Analysis) capability. With this test researches find a weak portion that needs to be correct. The other factor is heat transfer which has to be considering as it is cooled down the mould.

After collecting the data the engineers have to research previous data to apply the new attributes which is add to reduction design. These data consists of radius, angles, ribs and the texture of the main part. If the bottle has a handle, the design of the handle is have to be strong, comfortable and have a easy blow to make the whole process easy. The data is collected from a lab where it is tested. There must be the latest equipment which also has a top load tester, drop impact chamber, top wave vision system, vibration stand, and Magna Mike and altitude chamber. These equipments help in the process to get the best design.

The method is how much you saved with new less weight design. First, take the gram weight to save per container and then multiply by a number of containers made in one week. Convert the grams in KGs or pounds, and then multiply by resin cost after that you will get your weekly savings.

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The blow moulding is worked as its name stated. The molten material is known as parison or preform placing it in the mould and inflate with compressed air until it covers the mould and cools down before the mould is removed. Any hollow plastic product can be made with blow moulding. There are wide ranges of hollow plastic products around us and we use it in our daily routine life. Here are some products that are made with blow moulding.

• Medical supplies
• Household items
• Industry products
• Toys
• Plastic bottles
• Automotive parts

The blow moulding process is similar to glass blowing process. The first production machines and products are developed in 1930 to manufacture blow moulded bottles. After the introducing of low and high-density polyethene which is suitable for blow moulding, the market is hiked for blow moulding products.

The blow moulding process can be done with three different methods according to a product. Which are

• Extrusion blow moulding
• Injection blow moulding
• Injection stretch blow moulding

The main difference between these processes is forming the prison.

Now start with Extrusion Blow Moulding. In this process, the polymer is melted and it is extruded from a die to make a parison or hollow tube. The moulds covered the prison and with the pressurised air blows through the needle and it inflates the shape of a mould. After this, the cool air is blown and moulds are opened and eject the complete product. The extrusion blow moulding there are two methods of extrusion which are continuous and intermittent. In the continuous method, the parison is extruded continuously and mould open and close to complete the process. In the intermittent, the plastic is collected by an extruder and then push it to die to make parison. The products made with this process are bottles, toys, appliances and automotive parts etc.

Let’s discuss Injection Blow Moulding. In this process, the polymer is injected into a core to form a hollow tube known as a preform. Then the preforms are rotated on a core rod to blow mould and are inflated and cooled at blowing station. The injection blow process is suitable for small bottles. The process has three steps namely injection, blow moulding and ejection and all this action done in the single machine. The products like medical supplies, product packages etc.

Next is Injection Stretch Blow Moulding. This process is quite similar to injection blow moulding. In this process, the moulded preform is stretched up to decided length to get better strength and is light in weight. The raw material is used for this process is PET or PP and they are stretched for a better physical characteristic. The wall thickness of the final product is high than extrusion and injection blow moulding. The injection stretch blow moulding is divided in one step and two-step process.

The One Step process the preforms and blowing in the same machine. This process is completed in three or four station machines. At different stations, there is different action performs namely Injection, Conditioning, Blowing and Ejection.  This process is suitable for small to high capacity with different shapes and various size plastic bottles.

In the Two-Step process first, the preform is made with injection moulding. The preforms have necks and threads on the top. These preforms are cooled and stored for re-heat blow moulding. The preforms are heated generally with infrared heaters and then stretched and blow using high-pressure air in the mould.  The Two Step process is suitable for 1-litre bottles and under.

Their materials used for blow moulding are High-Density Polyethylene, Low-Density Polyethylene, PET, PVC, Polycarbonate etc.

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The Sadhi machinery Plastic Products are famous for their fully automatic blow moulding machine. The fully automatic machines help in production flawless and didn’t require constant monitoring. These machines are easy to operate and once it is install the company technician give training to the workers and help in production. The latest technology makes these machines fully automatic. The parts are used in machines are precise and bought from well known manufacturers. There are highly trained workers who assembled these and have expert engineers to ensure that these machines work perfectly. There are testing units to perform different tests on the ready product.

The R&D department is continuously research in development of machines. These Automatic Blow Moulding Machine have fully automatic de-flashing option to remove access material from a finished product. The melted material cut by hot wire cutter and poured in prison. After that air flows into it and inflates up to the mould size and cools down it. When the product is sufficiently cool the mould is open and passes for the next process. These machines are customizable with the single or double stations and single and double head options which increase the production capacity. The overall build quality is super strong and long-lasting. The parts and the design make this machine durable. These machines have very low maintenance and its feature of cloud fault diagnosis function module automatically scan the machine and find the fault by itself which save time of technician and start production after fix the problem. The Sadhi machinery is leading manufacturer of blow molding. These machines have intelligent operation function module makes the operation easy for operator. With the few settings workers are expert in operations and maximize the production. The cloud fault alarm system rings and blink lights when the machine stop working which is very important feature.

These machines have a safety feature which helps to prevent accidents.  The blow moulding machines are highly efficient and give maximum production and have low power consumption. These machines passed through various quality checks. After that it reaches to the customers to ensure that they will get best product. There are range of materials can be used in process and the product is strong and durable. There are range of products can be made with blow molding machines.

These products are used in houses as well as workplaces. There are number of single body hollow plastic toys can be made with this process. The reason behind the wide use of blow molding machines is its easy operations and highly cost-efficient. The automatic blow moulding machine requires less action to complete process and it is fast than conventional methods. These machines can work up to 24 hours and 7 days. The mould is made direct contact with the melted plastic and has to be durable. For that reason is made with high grade M.S which is durable than other material.

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There are different methods to produce plastic products. In the blow moulding there are three methods and are injection blow moulding, extrusion blow moulding and injection stretch blow moulding. In the extrusion blow moulding process the plastic is melted to is boiling temperature than forming into prison in the round mould of the product. After removing it from the furnace it makes it a hole into it to allow compressed air to blown away to the shape of the mould. After cooling down the product is ejected from the mould. After Cooling down the product is ejected from the mold.

There are numbers of advantages of blow moulding process. This method increases the production capacity. But it has disadvantage also.

Advantages of Blow Moulding

Advanced technology

The blow moulding technique completely changed the manufacture of plastic products. With the blow moulding method manufacturer can make various plastic products according to market and products that help people in their daily routine life. The blow moulding makes production fast and cheap for a manufacturer and produces more numbers of products.

Variety of Products

Most of the plastic bottles which are used to store liquids and other items are made with blow molding process. This technique allows engineers to redesign old products and create new products with the help of this method. There are some famous products made with blow moulding are plastic bottles, trays, plastic containers and some toys also.

Cost Efficient

For particular extrusion blow moulding needs low-pressure air which makes this machine cheaper the process is simple and easier. It is not required high skill to operate but with simple training, anyone is able to control it. One labor can operate this machine so it minimizes the labor cost.

Multiple Production methods

The blow moulding uses different methods to complete the process as we described earlier in the article. One of them is extrusion blow moulding works same as glass moulding where melted material blown to the mold. As we discuss in the injection blow moulding the melted material injected directly into the mold instead of blown by air. This makes production faster and this technology is continuously developed to increase the production.

High Productivity

With this globally accepted technology helps the manufacturer to produce plastic products worldwide.  This technology helps producers to increase the production and get high quality and quantity in a limited time. These machines have low maintenance and are easy to operate. This is beneficial for manufacturer due to less production cost.

These methods can allow choosing from different materials in productions. With blow molding method it can be possible to make products of different size and shapes. The plastic parison used to make single pieced hollow products. The build quality of products made with blow molding is durable and sustaining.

Now let’s talk about disadvantage. There are few disadvantages of blow moulding machines.

As the raw material is used in the blow molding machine are all made from petroleum products. The price of petroleum products is hike day by day and thus increase the production cost. Sometimes the supply is less than the demand and this affects the production.

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