Plastic Injection Molding- Process, raw materials, history

Top Injection Molding Company in India

Renowned as a blue-chip plastic component manufacturer India, Bindal Technopolymer Private Limited (BTPL) is a cutting-edge production unit with an outstanding reputation. Equipped with a futuristic manufacturing infrastructure, our engineers produce impeccably customized plastic products to meet the requirements of modern living.

Being one of the globally acclaimed injection molding manufacturers in India, we take pride in serving several Fortune 500 companies across diverse sectors by providing them high-quality plastic parts manufacturing services. Automotive, electrical, and medical are some of the predominant industries relying on our product efficiency, precision, and high-end performance. Counted among the premier plastic injection molding manufacturers, BTPL assures product quality because we are an ISO 9001:2015 certified company.

Every plastic part manufactured is individually tested at the various manufacturing stages to ensure you receive the highest quality products with sturdy designs, superior dimension precision, and prolonged service life. Constantly working towards employing innovative tools and techniques, we are dedicated to becoming the most credible plastic injection molding company in Noida.

In the pursuit of seeking knowledge, skill development, and machine operation, the passionate engineers at BTPL believe in amelioration and modernization. Hence, we utilize robotics and automation to procure unfathomable results. We ensure, every time, we come up with new ideas and introduce transformation as one of the benchmark plastic mold manufacturers in Noida.

Molding Meets Technology

Bindal Technopolymer Private Limited focuses on rapid prototyping and fabricating plastic parts for OEMs and ODMs. Our customized products are precisely designed to retain exceptional precision, tolerance, and material consistency. As a notable tool manufacturing company in India, we ensure the implementation of state-of-the-art equipment accompanied by the highest standard of raw materials.

Describe the process of plastic injection moulding

The whole process starts with screening the raw materials which are generally in granular or pellet forms. It is then fed into hopper. Here the pellets are melted at high heat and made soft enough to be pressure injected into the mold cavity to produce the shapes and sizes designed or required by the manufacturer.

The mold can be single or multi-cavity. The plastic parts are left to cool down and solidify before they are removed from the mold. The mold has two parts-injection that shapes the plastic into desired form and ejection mold that extrudes or removes the formed shape from the machine.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Timeline of Plastic Injection Moulding

• 1846 – Charles Hancock, a British inventor discovered and patented a plastic injection molding machine
• 1872– American inventor John Wesley Hyatt patented the first largely recognised plastic injection molding machine. It worked like a syringe and had a large hypodermic needle and a plunger to absorb, fill, and inject molten plastic into the mold.
• 1903–  Arthur Eichengrün and Theodore Becker invented the first cellulose acetate soluble form. It was later available in powder form from which it was injection molded.
• 1946– James Watson Hendry can be credited with building the first screw injection machine
• 1990– By the 1990s, aluminum molds started being used for plastic injection molding
• Post 1995– A large number of raw materials for injection moulding purposes got introduced in the market at a rate of 750 per year.

Robotics and Plastic Injection Moulding

• Robotic applications hastened the precision and speed of the overmoulding process, combining two separately molded parts into one. The application significantly reduced batch defects, ensuring epitomic quality, reliability, and integrity of the final product.
• Machine tending is a repetitive and error-prone job. Robots are extensively used for machine tending jobs and jobs that are repititive and involve a high amount of errors. They are also used in the unloading of injection molding machine
• Robots also ensure the dispensing of sealants in a consistent manner or the dispensing of adhesives in consistent, precise, repeatable patterns, thereby ensuring better shot accuracy and minimal waste
• Sprue picker robots and pick-and-place robotic devices remove sprues or runners from plastic injection molding machines and transfer them to granulators for recycling.
• Robotic trimming machines offer superior zero-error repeatability features compared to manual processes.
• Robots are used to reduce the risk of injury in insert moulding,  which involves the process of inserting components into the molded part which often requires handling minute parts.
• Robots ensure the highest level of consistency during the labelling process thereby enabling higher levels of quality assurance
• Robotic process automation helps in weeding out batch defects, supervision defects, and other underlying discrepancies and loopholes in the process.

The most common robot types used in Plastic injection molding are

• Six Axis
• Scara and Cartesian

                 Source: https://www.rnaautomation.com/insight/robotics-in-injection-moulding/

Preparing powder or pellets for Plastic injection molding

• The raw material or plastic resins are melted down and then passed through a grinding machine and extruded through a dye cast that shreds it into small pellets or powder.
• After being melted down, the raw material or plastic resins are run through a grinding machine and extruded via a dye cast, which breaks them up into tiny pellets or powder.
• During plastic injection molding process, the plastic pellets or powder typically melt between 150 and 300 degrees Celsius.
• The pellets are 1/8 of an inch in size and are either spherical or cylindrical.
• By varying the heater band settings, backpressure, and screw rotation speed, the plastic is melted to a uniform composition.
• Raw materials and additives are often placed into the hopper manually or by means of automated loader known as a Gaylord.
• Tubing is used to move material from pellet storage when a large volume is required.
• The plastic pellets are usually fed into the hooper at a cooler temperature to prevent premature melting before the pellets pass through the heater bands.

What are the different parts of a plastic injection moulding machine?

Rotating screw

The plastic pellets are forced forward by the revolving screw, which has a variable flight and pitch design. Friction and melting action cause the pellets to melt.

 

 

 

 

 

 

 

 

Nozzle

Nozzle is the opening at the end of the cylindrical barrel where molten plastic is pressure injected into the mold. The compression of molten material alongwith pressure injecting into the mold is done by the screw. The hydraulic unit generates the force to keep the mold together in the clamping unit, so that plastic under extreme pressure is kept intact in the mold. Hydraulics also provide the precision required in the clamping unit. The hydraulic controls and valves ensure consistent plastic quality.

All electric injection molding machines are an alternative where digitally controlled extreme speed servo motors does the function instead of hydraulics and ensure repeatable, consistent, precise parts. It is a cleaner process than hydraulics and doesn’t leak fluids. It ensures faster cycle times up to 20%. Combining the best of hydraulics and plastics is the hybrid plastic injection molding machine.

Injection moulding nozzle

Heater bands

Mainly three types of heater bands are used namely ceramic, mica, and mineral (brass, aluminium, and stainless steel) insulated. The types of heaters used in injection molding are barrel heaters, nozzle heaters, and hot runner heaters. The different types of screws used in injection molding are:

• HPT hardened allow screw. The steel is made of tungsten cobalt alloy powder
• Electroplated screw
• Double allow screw
• SKD61 screw
• Ordinary nitriding screw

Plastic Injection Moulding Process: Step-by-Step Guide

1. Selection of the Material

• Thermoplastics like PP,ABS, Polyethylene (PE), Polyamide (PA), polystyrene (PS), and nylon are commonly used as raw materials. The materials of specific impact strength, temperature resistance, and inertness to solvents are chosen based on their applicability.

2. Melting the Plastic inside the barrel (Plasticizing)

• Plastic pellets (resin) alongwith additives are fed into a hopper, from where they are transferred into a heating barrel with a rotating screw. The screw moves the pellets forward. The moving forward action creates friction which generates heat. Alongwith that, the heater bands turn the pellets into a molten stage.

3. Injection

• The molten plastic is injected into the metal mould cavity employing high pressure with the help of screw or plunger. This ensures that the plastic fills the cavity completely.

4. Cooling

The mould is closed on injection. It cools the plastic, solidifies it. The cooling time depends on plastic type, part thickness, complexity. The cooling channels within the mould use water to speed up this step.

5. Mould Opening

• After cooling, the mould opens, usually opening into two halves, one half of the mould containing the solidified part

6. Ejection

• Ejector pins/air blasts- Some parts require trimming or secondary processing in case there are excess plastic edges

7. Repeat Cycle

• The mould closes and the process repeats. The cycle time ranges from few seconds to few minutes or more, depending on the complexity of the part.

Key Components of a Plastic Injection Moulding Machine

• Hopper – Stores the plastic pellets and push it into the barrel
• Heated Barrel – Melts the plastic and pushes it forward into the mould.
• Screw – Mixes the molten plastic and moves it forward through the barrel
• Mould – The cavity where the plastic acquires shape
• Clamping Unit – Opens/closes the moulds under pressure
• Ejection System – Removes the moulded part from the machine

A[Start] –> B(Raw Material Feeding)
B –> C(Heating and Melting of Plastic);
C –> D(Injection into Mold Cavity);
D –> E(Pressure Holding);
E –> F(Cooling);
F –> G(Mold Opening);
G –> H(Part Ejection);
H –> I[End]

Advantages of Plastic Injection Moulding

• High-volume of production.
• Lower per-moulded part cost.
• Repeatable and precise.
• Helps in maintaining complex geometries.

Disadvantages of plastic injection moulding

• High cost of initial tooling.
• Long lead times for excellent mould design.
• Not economical for low production volumes.

Part	Location	Function	Appearance
Barrel	Around the rotating screw	Heats and moves plastic material through the machine	Cylindrical metal tube with insulation
Rotating Screw	Inside the barrel	Mixes and pushes molten plastic forward	Spiral-shaped metal screw inside the barrel
Nozzle	At the barrel’s front end	Directs molten plastic into the mold	Tapered metal tip with a small opening
Movable Platen	Connected to the mold	Holds and moves one-half of the mold	Large flat metal plate that shifts positions
Heating Bands	Wrapped around the barrel	Generates heat to melt plastic	Metal rings with electrical wiring
Hopper	Above the barrel	Stores and feeds plastic pellets into the system	Funnel-shaped container
Mold	Between the platens	Shapes molten plastic into the final product	Metal block with custom cavities
Clamping Unit	Near the mold	Holds and secures the mold during injection	Heavy mechanical frame with hydraulic system
Ejector Pins	Inside the mold	Pushes finished plastic parts out of the mold	Small metal rods embedded in the mold
Hydraulic System	Within the machine’s frame	Powers movements like injection and clamping	Set of pumps, cylinders, and hoses
Cooling System	Around the mold	Regulates temperature and solidifies plastic	Water or coolant channels in the mold
Controller Panel	Mounted on the machine	Controls and monitors the entire process	Digital display with buttons and settings
Tie Bars	Connecting the platens	Ensures structural stability and alignment	Long, sturdy metal rods running through platens
Injection Unit	Front section of the machine	Houses components for heating and injecting plastic	Large assembly containing barrel, screw, and nozzle
Guide Pins	Inside the mold	Aligns the mold halves for precise closing	Cylindrical metal rods within the mold
Vent System	Within the mold cavities	Releases trapped air and gases during molding	Small openings in the mold cavity