Blow Molding Machine Ultimate Guide

Welcome to the ultimate guide to blow molding machines!Whether you are a novice or a professional involved in the production and packaging of plastic products, this article provides the basic knowledge of blow molding machines, such as working principles, process flow, application range and everything you need to know.It is indispensable information for you.


What is blow molding machine?

Blow Molding Machine Definition

You should know that a blow molding machine is a processing equipment specifically used to manufacture hollow plastic products.Let me tell you that this kind of equipment blows molten liquid plastic into the mold cavity through air, forcing it to expand and fit into the inner wall of the mold cavity of various shapes and sizes.The machine then cools and hardens to produce hollow plastic products such as bottles or containers.


Working Principle of Blow Molding Machines

First, what you need to do is to put the granular plastic raw materials into the hopper of the blow molding machine and stir and heat them to melt them into liquid plastic.

Then they are pushed towards the machine head through the rotation of the screw barrel. During extrusion, they will extruded into a small ball or cylindrical shape and sent to the blow mold.

The liquid plastic raw material in the blow mold is injected with air or nitrogen through a nozzle or blow port, so that it is expanded by air pressure to fit tightly against the inner wall of the mold to form the desired shape.

After the blow mold is opened, you need to take out the molded plastic product for cooling and solidification. This can also done by letting it pass through the water channel in the blow mold or blowing cold air.


Blow Molding Machine Process

Step1. Raw Material Preparation: You need to prepare plastic particles that can heated and melted. Plastic granules are usually thermoplastic, with types including PP, PETG, PVC, HDPE, LDPE, LLDPE, etc.

Step2. Feeding: You transport the plastic particles to the hopper or screw of the blow molding machine.

Step3. Heating and Melting: The hopper or screw of the blow molding machine stirs and heats the plastic particles to melt them into a liquid state. By this stage, you know, the plastic has become sticky and moldable.

Step4. Molding: Molten plastic is injected into a specific blow mould through air or mechanical force to form a parison.You will see that it looks like a tube with a hole in one end.What you do is prepare the shape and size of your desired product before injecting it into the blow mould.

Step5. Blow Molding: After the molten plastic parison is injected, the blow mould will closed. Inject high-pressure air or nitrogen through a nozzle or blowing port to inflate the plastic parison. It expands to the inner wall of the mold until it takes shape according to the profile of the blow mold. This step is a critical moment in the formation of plastic products. Do you understand?

Step6. Cooling and Solidification: After the plastic product is formed, the blow mould will cool and solidify it.This is a necessary step to maintain the shape of the molded plastic product.You can set up water channels in the blow mould or blow cold air to cool and solidify.

Step7. Open the mold and take out the product: After the plastic product is cooled and solidified, the blow mould of the blow molding machine will automatically open and pop up. All you have to do is take it out.

Step8. Trim and Leak Test: This is the quality control method for manufacturing hollow plastic products.Sometimes there will leftover edges after plastic products are formed, and you need to trim them. The excess waste can recycled and reused.Leak testing checks whether a bottle or container is ingress or egress.

Step9. Finishing: This is a secondary surface treatment of plastic products that can add labels and packaging for distribution to manufacturers or final consumers.


Types of Blow Molding Machines

Extrusion Blow Molding Machine: is one of the most common types of blow molding machines. Using extrusion molding and blow molding processes, molten plastic particles are extruded into the prepared mold, and the plastic is extruded into the shape of the inner wall of the mold through air pressure or nitrogen. It is suitable for the production of medium and small hollow plastic bottle caps in the food, beverage, daily necessities and other industries, among which the minimum 2.5ml bottle can produced.

AMB-D-10L(Double Station) Extrusion Blow Molding Machine*5
AMB-D-10L(Double Station) Extrusion Blow Molding Machine

Injection Blow Molding Machine: also one of the most common types of blow molding machines. Combining the two processes of injection molding and blow molding, the specific operation is slightly different from that of the extrusion blow molding machine, that is, the molten plastic particles are pushed into the injection barrel through the screw, and the plastic is injected into the mold under high pressure. Suitable for manufacturing hollow plastic products with complex shapes or larger sizes, such as auto parts, medical equipment, cosmetics, etc.

AM35 Injection Blow Molding Machine
AM35 Injection Blow Molding Machine

Stretch Blow Molding Machine: It is a blow molding machine specialized in manufacturing PET materials (bottles, bottle caps, food packaging and other hollow plastic products). The specific manufacturing process is to stretch the plastic blank during the blow molding process so that it can appropriately extended in length and diameter to obtain better mechanical properties and transparency.

Rotary Blow Molding Machine: It has high productivity, high efficiency and stable molding quality. It has more advantages than other types of blow molding machines and is suitable for large-scale production. Its characteristic is that multiple molds are installed on a rotating turntable or chain, which can produce multiple large-capacity plastic products at the same time, such as bottled water and detergent bottles.

Multi-Layer Blow Molding Machine: has a more complex structure and function, and can produce hollow plastic products with multi-layer structure and various performance requirements, such as oxygen barrier, moisture barrier, UV resistance, etc. Its characteristic is that multiple extruder heads are configured inside the mold, which can extrude and stack different types or colors of plastic materials together to form multi-layered plastic products to meet the needs of different industries.


The difference between blow molding machine and bottle blowing machine.

Differences in production processes:

A blow molding machine is a machine that produces hollow plastic products by heating, melting, and blowing plastic particles into a mold. Blow molding machines are divided into extrusion blow molding machines, injection blow molding machines, stretch blow molding machines, rotary blow molding machines and multi-layer blow molding machines according to the production process. The bottle blowing machine is a machine specialized in producing plastic bottles. It is divided into one-step bottle blowing method and two-step bottle blowing method.

Differences in application scope:

Bottle blowing machines are specialized in producing plastic bottles of various sizes, shapes and materials. The blow molding machine can produce plastic bottles, as well as containers, storage tanks, auto parts, toys, warning posts, pallets, floats and many other irregular hollow plastic products.


The difference between blow molding machine and injection molding machine.

Working Principle

Blow molding machine: The heated and melted plastic particles are blown into the mold and blown into the shape of the inner wall of the mold by air pressure or nitrogen. Suitable for manufacturing hollow plastic products, such as bottles, containers, barrels, etc.

Injection molding machine: Inject heated and melted plastic particles into a pre-designed mold through high pressure, and solidify under high pressure to form the desired product shape. Suitable for manufacturing solid plastic products, such as parts, appliances, etc.

Application Scope

Blow molding machine: produces hollow plastic products, which are widely used in food packaging, cosmetics, medical supplies, household products, plastic toys, chemical industry and other industries.

Injection molding machine: produces solid plastic products, such as auto parts, home appliance casings, electronic product casings, medical equipment, home furnishings, construction, plastic toys and fitness equipment accessories, etc.

Forming Method

Blow molding machine: It is mainly formed by blow molding. The specific types are divided into extrusion blow molding machine, injection blow molding machine, stretch blow molding machine, rotary blow molding machine, and multi-layer blow molding machine.

Injection molding machine: mainly molded by injection and filling of plastic.

Applicable Materials

Blow molding machine: suitable for producing hollow products of thermoplastic plastics such as LDPE, LLDPE, HDPE, PP, PVC, PETG, PS, PC, EVOH, etc.

Injection molding machine: suitable for producing solid thermoplastic products including but not limited to PP, PS, PC, PE, ABS, PVC, PET, etc.


Types of material used in Blow Molding Machine

LDPE: The biggest feature is that it is very suitable for elastic plastic products that require flexibility but can resist stress cracks. The most common application scenario is plastic bags (such as plastic wrap, garbage bags, shopping bags). Therefore, LDPE has the characteristics of lower density, good softness and flexibility, and is not easy to deform and break.

LLDPE: It is a plastic derived from LDPE. Its strength, stiffness, and heat resistance are higher than that of LDPE, and its density is lower than that of LDPE.LLDPE works at higher temperatures without easily deformed or softened, and is resistant to acids, alkalis, organic solvents, etc.Widely used in packaging, industry, agriculture, medicine, health and daily necessities and other fields.

HDPE: The best thermoplastic for blow molding and probably the safest of all plastics (FDA approved).It has a series of excellent characteristics such as high density, good strength, hardness, corrosion resistance, wear resistance, and impact resistance.Suitable for plastic products that require long-term use, such as shampoo, oil containers, fuel tanks, industrial barrels, toys and other application scenarios.

PP: It is a thermoplastic synthetic resin with excellent performance and a colorless, translucent and recyclable general-purpose plastic.PP has physical properties such as low density, thermal stability, and chemical resistance.PP raw material has good solution fluidity and can manufacture hollow plastic products with complex shapes.And it can colored, and various additives can added to improve its performance or meet specific needs.

PVC: Once the most widely produced and versatile plastic in the world, with flexible resin the preferred material for blow molding. PVC features characteristics such as corrosion resistance, weatherability, and good processing performance. However, its production and processing may generate toxic gases and wastewater, so environmental concerns need to addressed. PVC can applied in construction manufacturing, medical devices, electrical wires and cables, etc.

PETG: Simply put, it is a thermoplastic with relatively good transparency, and it is also a non-toxic and harmless food-grade plastic. It has higher impact strength, is not easy to break, and can be used in food packaging and medical devices. Its processing and forming performance is excellent and it can form products of various shapes.

PS: The biggest feature is that the thermal stability and fluidity are very good when melted, and it is easy to mold and process, especially injection blow molding. Moreover, the ratings after molding are small and the dimensional stability is good. Its density is second only to PP, and its radiation resistance is the strongest among all plastics. It is widely used in the optical industry because of its relatively good light transmittance. It can also manufacture electrical components and instruments for high-frequency environments.

PC: It is the only one of the five major engineering plastics with good transparency. Because it is similar to glass, it has outstanding impact resistance, heat resistance, low water absorption, and excellent dielectric properties. Therefore, PC is suitable for manufacturing transparent or translucent optical lenses, automobile lights, building lighting panels, medical equipment and other plastic products.

EVOH: It is a combination of ethylene polymer and vinyl alcohol polymer. It has good processing performance and barrier effect. The barrier effect is against gases, odors, fragrances, solvents, etc. It is these characteristics that are widely used in the field of food packaging, such as condiments (soy sauce), tomato sauce, meat products, cheese products and processed fruits.


Applications of Blow Molding Machines

Food Packaging: bottles (such as juice bottles, milk bottles, transparent bottles), bottle caps, containers, barrels.

Cosmetics: facial cleanser bottles, essence bottles, lotion bottles, mascara bottles.

Medical Supplies: medicine bottles, infusion bags, packaging boxes and containers for various medical devices.

Household Items: shampoo bottles, cleaning fluid bottles, buckets, trash cans, hangers, laundry baskets, storage containers.

Plastic Toys: building blocks, dolls, footballs, basketballs, table tennis, children’s playpens, slides.

Industry: Industrial containers, storage tanks, transmission pipelines.

Chemical Industry: double-ring barrel, IBC ton barrel.

Automobile: automobile lampshades, fuel tanks, ventilation ducts, interior parts, cleaning fluid bottles, oil bottles, air filters.

Transportation: anti-collision barrels, water horses, roadblocks, warning posts, fences, pallets, etc.

Ocean: buoy.


Parts of Blow Molding Machine

Blow Molding Machine Parts Name

Heating System: Heating the machine head and mold, heating the granular plastic inside to a molten state.

Machine Head: It is one of the key components of the blow molding machine, responsible for pressing out the molten plastic and feeding it into the mold. The machine head determines the diameter and wall thickness of the plastic parison, and also has a great impact on the shape and quality of hollow plastic products.

Mold: The mold used for molding hollow plastic products can designed and manufactured according to the shape and size of the product you require.

Air Blowing System: The molten plastic is blown into the shape and size in the mold through high-pressure air or nitrogen.

Cooling System: Rapidly cools and solidifies blow molded hollow plastic products.

Control System: Control and monitor the operating status and production process of the blow molding machine, including blowing system, heating system, temperature, pressure, speed, output, etc.

Transmission System: drives various components of the blow molding machine, such as motors, gears, chains, etc.

Lubrication System: Put some lubricating oil on various parts of the blow molding machine to reduce friction and wear and ensure stable operation of the machine.

Base: Made of steel plates, it carries and stabilizes various components of the blow molding machine.


Why clean the head of the blow molding machine?

You need to know clearly that the machine head is a key component of the blow molding machine. Keeping the machine head clean is an important prerequisite for blow molding high-quality hollow plastic products. Sometimes the molten plastic will degraded or remain in the machine head due to excessive heating temperature or batch blow molding. In another case, plastic particles contain some additives, which will form by-products during the heating and melting process. These two situations will cause various residues to accumulate in the machine head, which will affect the surface of the plastic parison over time, and ultimately affect the appearance of the hollow plastic product. Therefore, you need to clean the head of the blow molding machine regularly.


Blow Molding Machine Cost

What Are the Factors That Affect the Cost of Blow Molding Machines?

Machine Type:

There are five types of blow molding machines: extrusion blow molding machine, injection blow molding machine, stretch blow molding machine, rotary blow molding machine and multi-layer blow molding machine. But you need to know that each type of blow molding machine has its specific advantages and areas of use, so its cost is also different.

Production Scale:

It is an important factor affecting the cost of blow molding machine. Larger blow molds and higher-capacity blow molding machines require more material and more energy, allowing manufacturers to produce larger and more plastic products. In short, as the size and production scale of the blow molding machine increase, the cost also increases.

Degree of Automation:

There are three types of blow molding machines: manual, semi-automatic, and fully automatic. You can clearly see at a glance that the manual blow molding machine is definitely the cheapest, and the fully automatic blow molding machine is the most expensive. However, fully automated blow molding machines can improve production efficiency and quality of plastic products, shorten production time and reduce labor costs. For plastic product manufacturers who need this machine, it is an important cost factor to evaluate their production needs and balance the degree of automation and production budget.

Additional Accessories:

Sometimes you may need additional functions such as automatic cleaning systems and automatic mold replacement, which will increase your purchase cost.

Maintenance and Care:

When you buy a blow molding machine, you must also consider whether the quality of the machine is reliable, whether the service life is long, and whether there is after-sales service. Reputable brands supply high-performance blow molding machines manufactured using high-quality raw materials. The cost may be a bit high initially, but in the long run, maintenance costs can reduced and productivity can increased. Maintenance of your blow molding machine is part of the operating costs and needs to be taken into account.

Shipping and Installation:

If the blow molding machine is imported from abroad, transportation costs and customs duties may affect the total cost of purchasing the blow molding machine.

To sum up, the cost of a blow molding machine is affected by many factors, including the type of blow molding machine, production scale, degree of automation, additional accessories, maintenance, transportation and installation, etc.


Precautions for Buying Blow Molding Machine

Define Production Needs: Determine your production needs, including the type and volume of plastic products you plan to produce, size, shape, throughput per hour, and automation technology requirements.

Evaluate Machine Specifications: Evaluate the technical specifications, configuration, parameters and other aspects of the blow molding machine, such as its machine size, mold size, output per hour, energy efficiency, degree of automation, scalability, etc. This helps determine the specifications and functions of the blow molding machine you need, avoids waste of resources or insufficient output, and allows you to upgrade or expand production capacity if needed in the future.

Investigate Blow Molding Machine Manufacturers: Conduct background checks on blow molding machine suppliers, such as industry reputation and relevant production certifications. If you have the conditions, try to visit on site and inspect the operation of the blow molding machine, so that you can have a more intuitive understanding of the strength of the blow molding machine supplier, the performance and operation of the machine.

Analyze Cost-Effectiveness: A series of costs such as the purchase price, transportation costs, operating costs, maintenance costs and production efficiency of the blow molding machine need to be comprehensively considered and analyzed to choose a blow molding machine with a high cost-effectiveness.

Consider Quality: The quality of the blow molding machine is very important. It is related to whether wear and safety hazards will occur when it is put into use, which in turn affects whether the production is smooth and whether the products produced have quality problems. Therefore, you need to check the materials and manufacturing processes of each component of the blow molding machine to ensure that it can withstand long-term stable operation and production.

After-Sales Service: Consult the after-sales service of the blow molding machine supplier to ensure that they can provide you with after-sales technical assistance and spare parts supply. The more perfect the after-sales service is, the more protection you have, which will help reduce your production costs and improve production efficiency.


Blow Molding Machine Maintenance

Blow Molding Machine Troubleshooting

  1. Leakage from hollow plastic bottles with narrow necks

Reason: The bottle wall is torn; the molten plastic is contaminated by dirt or impurities in the head of the blow molding machine.

Solution: Regularly clean the remaining dirt or impurities on the head of the blow molding machine; check whether the edges and gaps of the blow molding mold are worn and damaged, and whether the gaps are narrow enough.

  1. Surface defects

Reasons: Foreign matter or degraded old plastic in the blow molding machine head causes black spots on the surface of the bottle; abnormal temperature and humidity cause moisture to condense in the cooling plastic, causing bubbles on the wall of the bottle; the rough surface on the bottle is caused by the mold The moisture on the mold condenses, the blowing air pressure is too low, and the temperature of the molten plastic is too low; the slow closing speed of the blow molding mold results in burrs on the surface.

Solution: The solution to surface black spots is to clean the pollutants in the blow molding machine head; the solution to wall bubbles is to install a hopper with a drying function so that the plastic particles with condensed water can evaporate before entering the blow molding machine hopper to ensure The cooling water flow rate at the feed port should not be too high; the solution to rough surfaces is to reduce the humidity of the mold cavity, check the blowing system and increase the blowing pressure to increase the temperature of the plastic in the molten state. The blow mold is closed in two steps. The first step is to quickly clamp the plastic parison inside the mold. The second step is to slowly close the mold and push the plastic parison inward to form a strong welding line to avoid rough edges tearing your hollow plastic. products.

  1. The wall thickness of hollow plastic products is too large

Reasons: Insufficient pressure in the blow mold; deviation in blowing; too early inflation time.

Solution: Increase the pressure of the blow mold and appropriately reduce the blowing pressure; calibrate the position of the blowing port; adjust the blowing time.


The Importance of Proper Maintenance for Blow Molding Machines

Improve machine productivity: Regular maintenance helps your blow molding machine maintain optimal performance, ensuring all components are operating properly and producing more products in less time.

Guarantee the quality of plastic products: Without regular maintenance, defective plastic products may be produced due to machine component failure or wear, resulting in customer complaints or even product recalls. This series of costs is a bit expensive. Regular maintenance to keep your blow molding machine running smoothly can avoid most problems and ensure that plastic products meet the required quality standards.

Reduce downtime and repair costs: Neglecting maintenance can lead to blow molding machine failures and unplanned downtime, affecting your production schedule and increasing repair costs. Regular maintenance and inspections can identify and eliminate potential safety hazards, keep your operators safe, reduce the risk of workplace accidents, reduce the frequency of machine breakdowns and minimize repair costs.

Extend machine life: Regular cleaning, lubrication, and replacement of worn or damaged parts ensure that the blow molding machine operates at its best for a longer period of time. In the long run, it can extend the service life of your blow molding machine and save your business money.


How should we debug the blow molding machine?

  1. Before starting the machine, check whether the temperature control is sensitive, whether the instrument panel is normal, whether the cooling water channel is smooth, whether the screws and bolts of the mold are tightened, whether the power supply is stable, and whether the safety protection facilities are complete.
  2. First heat the screw, barrel and mold of the blow molding machine, and then start the machine ten minutes later to stabilize the stability of each component of the machine.
  3. When starting the machine, add a small amount of plastic particles first, the screw speed should be slow, and then gradually speed up to maintain a balanced feed. The feed amount can gradually increased until normal extrusion.
  4. Observe the stability of various parameters of the blow molding machine and product quality during the blow molding process, and adjust at any time according to the actual situation to achieve the best state.
  5. Conduct quality inspection on the produced hollow plastic products, including appearance, size, strength, etc. If problems are found, adjust the performance parameters or mold of the blow molding machine in a timely manner and start trial production again.
  6. When the blow molding machine stops running, stop material must be added first to squeeze the molten plastic particles out of the machine, then stop the heating system and disassemble the mold for cleaning.


What factors affect the service life of the blow molding machine?

  1. High-quality materials, optimized design, and advanced manufacturing processes directly affect the stability and durability of high-quality blow molding machines.
  2. Correct operation and regular maintenance can extend the service life of the blow molding machine. On the contrary, improper operation and lack of maintenance may lead to wear, failure and damage of various parts of the blow molding machine, shortening its service life.
  3. Proper control of production compliance and reasonable arrangement of production plans will help extend the service life of the blow molding machine.
  4. Regular replacement of easily worn parts such as screws, molds, and lubrication systems and preventive maintenance will help extend the service life of the blow molding machine.
  5. Harsh working environment, such as high temperature, humidity, corrosive gas, etc., may cause corrosion and aging of the blow molding machine, so pay attention to the working environment.


Blow Molding Machine Market

The blow molding machine market is also growing due to the expanding demand for plastic products across various industries across the globe. Therefore, blow molding machines are widely used to manufacture hollow plastic products with volumes ranging from a few milliliters to thousands of liters. In addition, the introduction of advanced technology makes blow molding machines more energy-saving, improves productivity, reduces the waste of plastic raw materials, and reduces labor costs. These factors help blow molding machines expand their application range and increase demand. The Asia-Pacific region is the world’s most important blow molding machine market share and, like Latin America, is growing strongly due to rapid industrialization and expansion of manufacturing.



As one of the key equipment for the production of plastic products, the blow molding machine plays an indispensable role in the food, medical, packaging and other industries.Through this guide, we have a comprehensive understanding of the working principle, production process, machine type, plastic type, application field, component composition, cost-effectiveness, maintenance, and market demand of the blow molding machine.We hope this guide can help you better understand all aspects of the blow molding machine, provide a reference for choosing the right machine for production efficiency and product quality, and promote the sustainable development of the plastic products industry.