Extrusion Machines – The Ultimate FAQ Guide

If you are interested in starting your business in the plastic industry or already doing it you must know about plastic extrusion machines.

These machines are used to produce products from raw plastic.

In this article, we will address all the FAQs related to extrusion machines.

Q1. What is the Plastic Extrusion Process?

To understand an extruder, it is essential to know the process of extrusion.

Extrusion is a process in which raw plastic material is melted or pushed to create quality plastic products with the help of a shaped tool called a die.

A die is a mold to shape the material through pushing and heating.

https://www.youtube.com/watch?v=Y75IQksBb0M

Q2. What Does Extrusion Pressure Mean?

The pressure in the extruder determines the output of the machine.

During the extrusion, the pressure is high inside the extruder barrel. These barrels are specifically designed to withstand pressure up to 10,000 psi.

Excessive pressure can cause cracks or even explosions due to die blown.

Q3. What is a Plastic Extrusion Machine?

Plastic extrusion machine is used to create a continuous process like tire treads, pipes, etc. A plastic extrusion machine is essential to complete a plastic extrusion process.

The machine heats up and pushes the raw plastic material through the die with a series of barrels and cylinders

      Figure 1: Overview of a plastic extrusion machine

A die attached to the machine controls the scale and form of the finished product.

The material is passed to the extruder and goes through the die in another form.

Q4. Who Invented Plastic Extrusion Machines?

Thomas Hancock invented a rubber ‘masticater’ in 1820 to recycled rubber debris.

Edwin Chafee designed a two-roller machine in 1836 to combine rubber activities.

After him, Paul Troester and his wife Ashley Gershof in Hamburg Germany created the first thermoplastic extrusion in 1935.

Q5. How Does a Plastic Extrusion Machine Work?

Raw plastic material gets pushed by a plastic extruder (a hopper) and melted by the heat produced through turning screws.

These screws are fixed with the barrels to melt down the material. To ensure the quality of the final products it is essential to maintain a constant temperature.

https://www.youtube.com/watch?v=WaB-dsB1Kfk

 The barrel is normally heated from back to front slowly. This way is used to avoid imperfection and overheating of the components.

A series of fans and water cooling system is used to control the temperature accordingly.

Extrusion dies are simply dense and oval-shaped stainless steel plates with one or more openings used in the production of the desired profile.

These dies are usually made of h-13 to resist hot aluminium pressure and excessive heat.

Q6. What Are The Main Components of a Plastic Extruder?

The basic components of the standard extruder include:

1. Feed assembly
2. Extruder barrel
3. Extruder screw
4. Extruder drive
5. Extrusion discharge or die system
6. Heating/cooling system
7. Adequate safety and control facilities.

Figure 2: Component of Plastic Extrusion Machine

Q7. How to Operate Machine?

1. Heat the unit to the required temperature.
2. Wait for nearly 20-25 minutes.
3. Fill in the hopper with the desired plastic.
4. Turn on the ignition.

https://www.youtube.com/watch?v=2rzhevw2Ong

5. The first 2 minutes are to clean the machine from the previous sessions with old plastics.
6. once the old material came out of the machine the machine is ready to produce!

Q8. What is Meant by Die Extrusion?

The extrusion die is simply a thick, circular steel disk to create a required profile. it has one or more openings constructed with H-13 die steel.

https://www.youtube.com/watch?v=U5pr-Z76Urg

Q9. How Many Types of Plastic Extrusion Machines Are There?

In general, a feed screw, a barrel, and a temperature controller are basic ingredients of an extruding unit.

The layout and specifications of the unit, however, depend on various other factors, such as the material and the product design to be extruded.

In the market, there are several plastic extrusion machines available.

• PP TQ Film Plant
• Plastic Extrusion MachinesAir Bubble Sheet Plant
• Multi-layer Blown Film Plant
• PET Box Strapping Plant
• Plastic Sheet Extrusion Machine
• Blown Film Plant
• PP/HDPE Box Strapping Plant
• HDPE pipe extrusion line
• Cast Film Line
• Raffia Tape Stretching Line
• Extrusion Coating Lamination Plant
• PP/HDPE/PET Monofilament plant

Other than these reprocess machines and Raffia Tape Line are also available for recycling the waste plastic material.

Q10. What are the Different Types of Plastic Extrusion?

Depending on the die shape, different types of plastic products can be produced through several extrusion processes.

Tubing Extrusion is used to create tubes and pipes. Air can also be applied in this method for positive internal pressure.

The tubes or pipes are pushed into a cooling tank after leaving the die as they usually are water-cooled.

Figure 3: Tubing Extrusion Process

Blow Film Extrusion used for the continuous sheeting processing of plastic film tubes. This method refreshes the film tube until the die is left, produces a semi-solid tube, and is blown to stretch to the ideal size or thickness of the film.

This method is used to manufacture plastic items like shopping bags.

Figure 4: Blow Film Extrusion Process

Sheet Film Extrusion used for extrusion of too dense to blown plastic sheets or foils. After the die is completed, a variety of cooling rolls are pulling and cooled to control the thickness of the board.

Figure 5: Sheet Film Extrusion Process

 Over Jacket Extrusion is used for wire-coating. The wire is drawn through the centre of the die in this process. Pressure tools are used where the adhesive is appropriate between the cable and the coating.

Jacketing tooling is used where adhesion is not necessary. In this way, the wire is protected by the melt as it leaves the die.

Figure 6: Over jacketing extrusion process

Q11. What Die Tools are Used in Plastic Extrusion?

In plastic extrusion, there are several dies.

Although the forms and complexities can be drastically different, both dies to allow for the continuous extrusion of silicon melt in contrast with non-continuous processing such as injection moulding.

1. Sheet Dies are the most common extrusion die for sheet products.

Commercial sheet dies normally use four features to control the flow to the die lip.

The plates are heated normally by cartouches spread over the width of the die.

Figure 7: Sheet Die

2. Blown Film Line is used to processing plastic films for items like packs and continuous sheeting. This method is the same as a natural process of extrusion before the die.
3. The annular die is the simplest, based on the polymer melting channel in the whole cross-section of the die before the die is removed; the flow can be uneven.

Figure 8: An annular rotating-die technique

4. Spider die consists of a centrally connected mandrel on the external ring via a series of “legs” while the flow is more symmetrical than the ring dies, there are some welded lines that degrade the film.

Figure 9: View of Spider Die

5. Spiral dips are the most dynamic but avoid the problem of sold lines and asymmetrical flows
6. Extruded tubing is made with very similar dies, such as PVC pipes, as used in the extrusion of blown films.
7. Over Jacketing Extrusion, the exterior coating of plastic will be added to an existing wire or cable. This is the normal isolation method. The melt touches the internal wire of the pressure tool well before it hits the lips.
8. Coextrusionis the simultaneous extrusion of many material layers. Two or more extruders are used for this method to melt and provide steady volumetric output.

The thicknesses of the sheet are influenced by the relative speed and size of the materials supplied by the individual extruders.

Q12. What are the Different Types of Plastic Extrusion Materials?

Commercially, the material of plastic extrusion is classified into three categories: product, manufacturing, and high performance, depending on their costs, market share, and material properties.

Commodity Plastics constitute 90% of the overall thermoplastic application. They are easy to produce, and the cheapest plastic for extruded goods.

They are available. For eg, polypropylene (PP), polyethene (PE), or polyvinyl chloride are popular plastics (PVC).

     Figure 10: Plastic Extrusion Material

Engineering Grade Plastics are engineered to enhance performance in complex applications with special combinations of properties.

Examples of manufacturing quality plastics include thermoplastic elastomers (TPE), polycarbonate (PC), polyamide (PA or nylon) (ABS).

Extraordinary mechanical and/or temperature characteristics are built to satisfy high-performance demands in difficult conditions for High-Performance Plastics.

Many of the more costly plastics are also normally used for specialized applications with a low volume.

Q13. What is the total estimated size of the global plastic extrusion machine market?

The Global Plastic Extrusion Machinery Market is expected to grow from $5,373.05 Million in 2018 to $7,846.23 Million by 2025.

Q14. How much plastic extrusion machine cost?

The cost of extrusion machines vary.

The price depends on the type and quality of the product.

The company’s rates also influence the rates of the extrusion machine.

The prices of extrusion machines manufactured in Taiwan are expensive to China manufactured machines.

wecoex Machines supplies durable extrusion machines and extrusion lines at reasonable prices.

Q15. What is the total sale of extruded products?

The global extruded market is expected to reach a projected value of $7.11 billion by 2022.

Q16. Who are the major plastic extrusion machine manufacturing countries?

China

Taiwan

Germany

Q17. Who are the best manufacturers of plastic extrusion machines in China?

Many Chinese manufacturers are selling not only extrusion machines but also extrusion machine parts to businesses all over the world.

wecoex Machines is one of the reliable companies. It ensures quality and provides many services including engineers’ assistance to its customers.

wecoex Machines also recommends its customers the most suited machine following their requirements. It also sells customized machines to fulfil customers’ demands.

Q18. What is the difference between Chinese and European plastic extruders?

Unlike China, European extrusion companies prefer to use household machinery extruders with less power.

Q19. What Factors Can Affect the Plastic Extrusion Process?

Impact of Mechanism

• As the head pressure increases, the volume of extrusion increases sequentially.
• The extrusion pressure decreases significantly when the random head pressure increases for a deep groove and short screw extruder.
• With the speed of the screw, the extrusion amount gets high. But the head pressure rises in proportion to the extruder volume decrease.
• The smaller the distance between the screw and the barrel, the bigger the extruder head is, with the random head pressure increasing.

The outcome of Screw Speed

• With increased screw speed, the volume of extrusion increases, but it is not sequential.
• The increase in the screw speed is correlated with the material’s increase in the extrusion frequency.
• The volume of extrusion increases at high melting temperatures at elevated velocity. However, the rise is limited at low melting temperatures.
• Due to its velocity, the volume of the uncooled screw is much greater than the cooled screw.

Impact of Temperature

• The volume of extrusion at the beginning is not adjusted as the melting temperature increases. When a certain amount of the temperature goes up, the substance viscosity reduces and the extruder quantity declines quickly.
• The volume of extrusion is therefore greatly decreased by a sudden reduction in the viscosity of the material as the temperature of the barrel is elevated to a certain limit.
• The volume of extrusion decreases dramatically with the elevated temperature of the screw.

Q20. What Kind of Material Plastic Extrusion Machine Mold or Extrude?

For the creation of different products through extrusion machines, various types of plastic materials are used.

For plastic pipes extrusion, polyvinyl chloride (PVC), high-density polyethene (HDPE), polypropylene random copolymer (PPR), and high-temperature resistant polyethene (PERT) are used.

Figure 11:  Plastic extrusions made by using different types of plastics

Polyvinyl chloride is also used to make marble plates, moisture plates, and wall panels.

In comparison to these plastic extrusion devices, polyethene, acrylic, polypropylene, polystyrene, and acrylonitrile butadiene styrene are used.

Q21. What to Consider When Selecting Plastic for Extrusion

The first task when a material is selected is to evaluate the plastic grade to analyze. Start with commodity-grade plastics unless your application is in a particularly hostile climate.

Then choose which molecular structure will give you your desirable qualities, amorphous or crystalline.

Choose the most suitable plastic for your application in that category. Consider that most plastics can be supplied with additives, filled or reinforced.

Q22. What Products Can Be Made By Plastic Extrusion Machine?

Many people from outside the plastic sector wouldn’t have the first idea of what an ‘extrusion’ is, let alone how many industries use it.

The method takes place in many unexpected locations, from our area of expertise, aluminium extrusions, to surprising sectors such as food processing.

1. Drinking Bottles
2. Automobiles
3. Wires and Pipes
4. Profile Shapes
5. Pipe/tubing
6. Weatherstripping
7. Fencing
8. Deck railings Window frames
9. Plastic films and sheeting
10. Thermoplastic coatings

Figure 12: Finished Products made by Extrusion

Q23. What is the Heat power of the production extruder?

For many commercial grades of PFA the melting points ranging between 300–310°C.

Q24. What is the method used for the extrusion of plastic pipes?

The method for extrusion of plastic pipes relies on many factors including the type of pipes. Mostly hot extrusion is used for pipes.

In this method, the plastic moves down the hopper to melt it. This is the most common way to mould the material into the required shape.

https://www.youtube.com/watch?v=zcBv_JvFDBI

The plastic moves into the die and the product are then cooled to solidify.

For this purpose, both single and double screw extruders are used following the requirements.

Q25. What is a Plastic Extrusion Machine Screw Design?

The screw is one of the integral parts of an extrusion plastic machine. The screw transports the plastic, heats it, and drives it into a die barrel.

These three steps are done in continuity to produce extrusions in a wide range of lengths.

The construction of the screw is roughly similar to the 250 BC Archimedes screw used to elevate water through the axial rotation to higher heights.

https://www.youtube.com/watch?v=Y3TK8rU1AGg

The extrusion screw will nowadays have various pitches, helix angle, ratio length to diameter, and processing stages length.

These variables affect the various strain, shear, and feed rates for a given plastic. Some extruders have double screws to help mix additives.

Q26. What is Basic Screw Design?

The basic extrusion design includes three different sections. Each section is designed to perform a specific task.

The feed section is located in the rear of the screw, in which gravity is provided by plastic pellets from above. The feed section’s length to diameter ratio is normally 4 or 5 to 1.

Figure 14: Basic Screw Design

This is enough to maximize the pressure required for the transport of the plastic.

The second section is the transition section. This section is used to transform the plastic into its liquid form by using two concurrent methods.

Heaters in a barrel have an initial melt, while the shear of the plastic on the barrel completes the process.

The root of the screw is raised in this process as the flutes or “flights” decrease. The plastic material that has been compacted in the first section gets less space in this section.

Due to the pressure, heat, and sheer plastic material begins to melt and flow. This section usually takes 5 to 10 cycle diameters.

From here the melt moves to the third section known as the metering section. Here the screw diameter stays constant with no further change.

In this section, the melted plastic with high pressure is pumped into the extruder die.

Q27. What is Barrier Screw?

Sometimes plastic is not melted completed in the basic screw design.  Barrier screws are used to avoid this issue.

To separate molten and solid material many flights are attached to the transaction section additionally.

Figure 15: China-made Screws

The strong pellet goes forward and flows through the channel due to its shear against the wall. So the solid canal is progressively widened and the liquid canal is expanded.

Q28. What is Mixing Screws?

A more convenient approach is to blend extrusion compounds with a twin extruder by combining two separate additives.

Two screws spin each other in this system and have unique features such as kneading blocks as well as forward and reverse capacities.

However, certain individual screw systems may be used for blending.

Q29. What is a Single Screw Extruder?

A single screw extruder is a machine that is used to shape plastic products as per requirements.

This machine melts the plastic material by heating it and pushes it through a die to form its shape.

Figure 16: Single Screw Extruder

Q30. What is a Double Screw Extruder?

A twin-screw extruder is a machine with two identical co-penetration and self-purifying shafts that rotate in the same direction in a closed fixed barrel.

With very short residential periods the two-screw extractors run continuously.

Figure 17: Twin-screw Extruder

Q31. What are the Distictictive points Between Single and Twin-Screw Extrdurs?

They have different mixing capacities. A double screw extruder is known for its mixing capabilities whereas a single screw extruder has very limited mixing capacity.

A double screw extruder can handle multiple processes including melting, venting, cooling, etc. whereas a single screw extruder is not designed to perform multiple functions at the same time.

https://www.youtube.com/watch?v=08_f5BRYcyM&t=12s

A single screw extruder is simple and available at low rates whereas a double screw extruder is expensive due to its complex functionality.

A single screw extruder has a simple control process whereas a double screw extruder is complexed and has a complicated control process. 

Q32. What Is The Difference Between Injection Molding and Extrusion?

Injection moulding is a form of plastic moulding which varies slightly from the usual extrusion method of plastic.

Figure 18: View of Injection Molding Machine

Moulding by injection is a good 3D forming device source consisting of two components: the clamping unit and the injection moulding unit.

Plastic pellets or resin are applied to the barrel in the injection moulding, where heat is emitted to melt it. Due to the hydraulic pressure, the plastic is then forced forward. It is not infinite produce.

The plastic molten is then pushed into a form of the appropriate shape and dimensions through an aperture. The material is pressurized to cover all room in the mould.

The cooling process begins when the mould is packed with plastic. This arises at the time of mould.

When the product is pulled out of the mould, the product is ejected.

On the other side, extrusion moulding shapes 2D artefacts. This form does not use a three-dimensional mould.

The material is extruded from a die to form uniform cross-sectional artefacts.

As passed through the die, the molten plastic takes on the unique shape of the die and has a uniform transversal region. Then it can be trimmed to the desired length.

https://www.youtube.com/watch?v=9C2As2gG7fU

Owing to the disparity, in theory, both methods have different implementations.

For the manufacture of three-dimensional objects, injector shaping is used to ensure minimal waste, because the plastic is recyclable.

Q33. What is the Difference between Direct and Indirect Extrusion Process?

There are two types of extrusions, known as direct and indirect extrusion.

https://www.youtube.com/watch?v=aLceoajLg1M

The main distinction between the two processes is the direction and intensity of the extrusion product.

The direct extrusion In a process where the material flows following the movement of the ram is called direct or forward extrusion.

After passing through the die material formed the finished product.

Usually, pipes and other hollow and semi-hollow products can be made by this method.

The major downside to this approach is that the force required to extrude the billet is higher than the force sufficient for the indirect form of extrusion.

Figure 19: Process of Direct and Indirect Extrusion

As the indirect extrusion process works backwards it is also known as the backward extrusion process.

In this process, the material moves in the opposite direction of the ram.

In this method, the die is located on the ram and the extrusion comes out of it.

This process reduces friction, which makes the extrusion faster

this process lack versatility due to the limited cross-sectional area.

In direct extrusion, the billet pushes by a set container and die through the press ram.

On the opposite, the billet is set while the diameter is pointed into the jar containing the billet during the indirect extrusion process.

Q34. What is the capacity of laboratory extruders?

The capacity of a laboratory extruder varies from 40kg to 50kg per hour.

Q35. What are the Advantages and Disadvantages of a Plastic Extrusion Machine?

There are several benefits of using extrusion machines such as:

1. The extrusion process is low cost with high efficiency.
2. The extrusion process is flexible. It can mould any type of product with ease in less time.
3. The plastic extrusion machines ensure quality products with a smooth surface.
4. Additives to the extrusion machine may also be applied to increase the properties of the materials used.
5. When the extruder exits, the plastic stays hot. It helps manufacturers to change the shape of extruded plastics to meet their needs with different rollers, dies and shoes.
6. Extrusion machines help you recycle waste to form into usable products.

Figure 20: Waste can turn into usable products

Extrusion machines also have some disadvantages such as;

1. There are high chances of die swell and it may affect the sizes of the products.
2. Production limitation is another obstacle. Only one type of product can be used in one machine. It increases the possibilities of investment.
3. The initial setup cost is relatively high.

Q36. How you can improve plastic extrusion machine efficiency?

Keep the following tips in mind to increase the efficiency of your extrusion machine.

1. Adjust the temperature of the feed throat. It should be warm to the touch when handling polyolefines. This way you can enhance processing by improving the distribution of solids and decreases energy by stopping heat from being displaced through the feed throat.
2. Keep the regrind shape consistent. Holding a cohesive structure facilitates bulk density, increases the movement of the feed hopper and provides reliable transport in the feed portion of the screw. Both these factors impact the stability of the performance of the screw.
3. Always use treated water in your closed-loop. Adding glycol to the system can change the flashpoint of the water that reduces its effectiveness to cool.
4. Select only reliable screw suppliers. Screws have a great impact on the efficiency of the machine. Poor quality screws can cause you damage.

Q37. What are the plastic extrusion problems?

The plastic extrusion has many problems such as;

1. Improper System Engineering/Installation
2. Improper Operation
3. Resin Defects
4. Improper Materials Addition
5. Surging
6. Poor mixing
7. Melt toughness or fracture
8. Overheating
9. Moisture release
10. Trapped air
11. Contamination.