Blow molding is one of the many processes used by plastic injection molding companies. It involves placing a molten tube of thermoplastic material (often referred to as a preform or parison) within a mold cavity and inflating it with compressed air. The air forces the molten tube to take the shape of the mold cavity it was placed in.
Due to its efficiency, the blow molding process can be used in different industries. In addition, the process has enabled engineers to attempt the creation of several designs and applications resulting in multiple uses. The following benefits are four significant advantages of blow molded plastic solutions.
1. Automation
Earlier developments of the Placo X-Y machine from Japan led to the introduction of 3D blow molding. 3D blow molding is an automated production process that, due to the accurate receptacle it creates, enables the seamless incorporation of parts and increased production speed. Also, automation help manufacturers retain the quality of a wide range of blow-molded products.
2. Mass Production
The blow molding process results in quality output. For this reason, it is one of the most used in plastic production globally. With the use of machines that have 3D molding capabilities, blow molding can help manufacturers produce many units within a short period of time.
3. Cost-Effective
Extrusion blow molding uses a relatively lower level of pressure. This reduces the expenses incurred in the production process and makes the product cost-efficient. Also, the use of the blow molding process will allow manufacturers to minimize high labor costs.
4. Multiple Production Methods
The various methods made possible with blow molding allows manufacturers to have several production options and more extensive possibilities on the products produced. Extrusion blow molding, for example, can be used to create products like light bulbs, while injection blow molding produces receptacles in large quantities. On top of that, blow molding is a process that is continuously developed with the end goal being full automation.
For more information on Valencia Plastic’s blow molding process, visit our blog or contact us today. We are a leading plastic injection molding manufacturer in California, and we can held you decide if blow molding or injection molding is the best process for your needs.
Injection Blow Molding vs Extrusion Blow Molding
Both injection blow molding and extrusion blow molding processes are integral in many manufacturing applications. These techniques are used to create many disposable and recyclable plastic parts, including products used in medical and research applications. Both processes feature unique functions to produce different results, which is why it’s important to understand each process to determine which is suitable for manufacturing a particular product. To help you better understand the differences between injection blow molding and extrusion blow molding, we’ll go over how each process works so that you can determine which is best for your needs.
What is Injection Blow Molding?
To increase production efficiency in the 1930s, injection molding was developed. The process involves melting plastic and then injecting it into a predesigned mold. Primary advantages of injection molding include reduced waste, minimal finishing requirements, and recyclability. Unlike extrusion molding, the design capabilities of injection molding allow for the manufacturing of 3D components. The machines used for injection molding include two core components: the clamping unit and the injection unit. Injection blow molding, or IBM, is a specific type of injection molding process that involves the use of a metal shank or core rod. The process uses a parison that forms the basis for the finished product. The beginning of the IBM process entails transferring the parison/core rod into the blow molding unit of the machine, followed by inflating and cooling the pre-formed part. After cooling, the core rod is rotated to the ejection position, the mold is opened, and the product is removed. Throughout the process, three sets of core rods are used to facilitate mold injection, blow molding, and the ejection of the formed part.
What is Extrusion Blow Molding?
Extrusion blow molding, or EBM, is similar to IBM, but instead of injecting melted plastic into a mold, the material is extruded or expelled into a hollow tube, known as a parison. A mold closes around the parison in order to shape the part while at the blow station. At the blow station, air is blown into the parison inflating it into the shape of the mold. Once the plastic has cooled, the mold is opened, and the part is extruded. Any excess material is trimmed from the completed part. Because of the EBM process, there is typically a high level of scrap produced.
The Key Differences Between Injection and Extrusion Blow Molding
There are three main areas in which injection blow molding and extrusion blow molding differ.
Products
The principal difference between IBM and EBM is the type of products they create. IBM is typically used to form more solid parts, which can include medical parts, kitchen parts, and other solid components. Meanwhile, EBM is used for manufacturing more hollow parts like bottles and other containers. Extrusion Blow Molding can manufacture more complex shapes due to how the product is formed. However, injection molding is able to produce large volumes of quality parts quickly and accurately.
Molds
For IBM, there needs to be a high precision match between both halves of the mold to enable total control over the flow of resin. Most of the work involved in injection molding involves producing the mold. In EBM, there is a higher level of design flexibility between both mold halves since each half forms its own wall shape.
Types of Materials
Extrusion blow molding is most commonly used to form products out of:
High-density polyethylene (HDPE)
Polypropylene (PP)
Polyethylene terephthalate (PET).
Injection blow molding is most commonly used to form products out of:
Acrylic
Polycarbonate
Polyoxymethylene (POM)
Polyethylene (PE)
What Are Differences Between Blow Molding and Injection Molding
Injection and blow molding are plastic manufacturing processes for making parts with commercial and industrial applications. Both processes are different, although often confused for each other due to the word “molding.” As a result, plastic molding enthusiasts need to understand the blow molding vs injection molding comparison and know the differences between the two processes to accurately decide on the right one.
This article introduces blow and injection molding, their applications and advantages, then discuss the differences between blow molding and injection molding.
What is Blow Molding?
Blow molding is a plastic molding process that is similar to glassblowing. The process begins by heating the raw plastic material to a certain temperature (depending on the plastic). Afterward, an extrusion machine extrudes the heated plastic material to form a hollow tube, a.k.a parison.
The operator places the parison in a prepared mold and blows air (pressure of about 80psi) to the mold. As a result, the parison expands in the mold, taking its shape. On cooling, the plastic sets and forms the hollow parts according to the mold design. Delegating then occurs.
Types of Blow Molding
There are three types of blow molding:
· Injection Blow Molding
This involves using a blow or core rod to inject the parison into the mold cavity. As a result, the parison will have a test-tube shape. Upon insertion into the mold, the air is blown to the parison to take the shape of the mold.
· Extrusion Blow Molding
There are two variations: continuous or intermittent. On the one hand, the continuous variant involves constantly feeding the parison to mold and cutting it off with a blade on cooling. On the other hand, intermittent variant expels the molded part before inserting a new parison. As a result, the intermittent variant is less expensive and takes less time.
· Injection Stretch Blow Molding
This combines injection and blows molding processes to make a plastic part. The process starts with making a solid pre-form using injection molding. Afterward, a machine heats the pre-form and blows air into it.
Advantages of Blow Molding
The blow molding process has the following advantages:
It has a lower production cost in comparison with injection molding
It has a low initial machine investment
It eliminates the need for a two-part mold component
It has great part design flexibility
Applications of Blow Molding
Blow molding is highly cost-effective and functionally effective. Consequently, it is an important process in making uniform and thin-walled hollow components. Small businesses in industries such as automotive, consumer products, medical parts, pharmaceuticals, etc., use it in making hollow parts such as bottles, water tanks, etc.
What is Injection Molding?
Injection molding involves using precision molds and tooling to manufacture solid plastic parts. The mold is the component with the final product’s design made from materials such as steel and aluminum using a high precision and tolerance process such as CNC machining.
On designing and manufacturing the mold, the injection process starts. The first stage involves melting the injection molding material at a very high temperature (depending on the plastic polymer). Furthermore, the operator injects the molten plastic into the mold at high pressure. After injection, cooling occurs to harden the plastic polymer, and then ejection occurs. You can also subject the part to a surface finishing process.
Advantages of Injection Molding
Injection molding has the following advantages:
Development of highly detailed molds with multi-cavity options
It has a high precision
It is cost-effective for high-volume production
It has great material flexibility, color options, and efficiency
Applications of Injection Molding
Injection molding is applicable in the volume production of solid parts with great details and high precision. For example, container caps, combs, and mobile phone cases. It is also applicable in the automotive parts and medical parts manufacturing industry.
Differences Between Blow Molding and Injection Molding
Understanding the blow vs injection molding comparison can only be effective by understanding their differences. Below are a few differences between blow molding and injection molding and how to tailor them to your project.
Blow Molding vs Injection Molding: Molding process
One of the major blow vs injection molding comparisons concerns the molding process. Injection molding involves sealing the plastic in the injection chamber and injecting it into an already prepared mold. Consequently, the plastic is in the injection chamber and the mold throughout the injection process.
On the other hand, blow molding involves heating the plastic and blowing air using an plastic extrusion machine to form the hollowed tube or parison. Afterward, the parison is placed in the mold, and air blowing continues till the final product forms.
Key takeaway
Injection molding does not use air because it can lead to the formation of air pockets in molded plastic parts.
Blow Molding vs Injection Molding: Mold design
Another major distinction in the injection molding vs blow molding comparison concerns the mold. Injection molds should be highly precise for the accurate flow of molten plastic material on injection. Hence, the use of CNC machining.
Due to the mold’s precision, injection molding is suitable for molding plastic parts with complex designs. Also, the molds come from strong and durable materials, ensuring repeatability without losing quality.
On the other hand, molds used in blow molding have better design flexibility. In contrast to injection molding designing the mold is not an issue. The issue is more with the molding process, where issues such as air leaks, wall thinning, streaks, and flashes occur.
Blow Molding vs Injection Molding: Materials and Color Options
Both processes are compatible with a wide range of materials. However, choosing a material depends on its complexity and desired properties. Hence, the need for professional guidance.
Blow molding is majorly used for soft and flexible plastics such as Acrylonitrile Butadiene Styrene (ABS), High-Density Polyethylene (HDPE), Low-Density Polyethylene (LDPE), and Polypropylene (PP). On the other hand, injection molding is compatible with hard plastic polymers and resins such as polycarbonate.
Nevertheless, many blow molding materials are suitable for injection molding. A few examples of common materials used in blow and injection molding are:
Acrylic: Acrylic is glass-like plastic resistant to wear, scratching, color stain, and UV exposure. It is commonly used in food and beverage applications.
Acetal: Acetal is a strong plastic material resistant to friction, temperature, and abrasion. As a result, it is commonly used in mechanical and automotive applications.
Polyetheretherketone (PEEK): This thermoplastic has a high chemical, radiation, and temperature tolerances. Consequently, it is important in manufacturing parts used in many medical, automotive, and industrial environments.
Poly Vinyl Chloride (PVC): PVC has high durability, dimensional stability, and resistance to flame, chemicals, and abrasion. Therefore, it is a common injection molding material industry-wise.
Polyester: They have high tensile strength and dielectric properties in making trampolines, canoes, etc.
Urethane: This low-cost injection molding material can achieve precise tolerance. Consequently, it is applicable in making products with complex designs.
Just ensure you know the different factors in choosing the right material.
Blow Molding vs Injection Molding: Manufactured Parts
The most distinctive difference between the blow and injection molding is that the former is suitable for hollow parts, and the latter is applicable for making solid parts.
Injection molding is the right method for making plastic parts that need a rigid wall, such as bottle caps, hair combs, and computer housings. In contrast, blow molding is suitable for making hollow products with flexible or structural properties. For example, bottles, coolers, fuel tanks, and stadium seats.
Blow Molding vs Injection Molding: Cost
Blow molding has a lower cost than injection molding cost due to the shorter operation and tooling cost. Furthermore, the cost of a blow molding machine is lower than the an injection molding machine.
Quick Pick: Which is Yours Between Blow Molding and Injection Molding?
Choosing between blow molding and injection molding should only occur after knowing the differences between both processes. The major decider of your choice should be your investment capability and the types of products you want to make.
Blow molding is the best when working with hollow parts such as bottles, water tanks, etc. But if your desired project requires a solid part with a complex design, injection molding is the right process.
Conclusion
Blow molding and injection molding are common plastic part manufacturing processes used in commercial and industrial products. They are different processes with plastic parts designs. This article talks about the difference between blow and injection molding. Do you need high-quality plastic parts? Let us help you get started.
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