The key difference between extrusion and injection Blow Molding is that extrusion blow molding involves extruding heated material, whereas injection blow material involves injecting heated material into a mold.
Blow molding is the process of forming and joining together hollow plastic parts. We can also use it for the formation of glass bottles or other hollow shapes. Generally, these manufacturing processes use three types of molding processes: extrusion blow molding, Injection Blow Molding, and injection stretch blow molding. Generally, the first step of the blow molding process is softening plastic via heating and forming it into a parison, which is a tube-like piece of plastic with a hole in one end, allowing the compressed air to pass through. But injection or injection stretch methods form a preform.
1. Overview and Key Difference
2. What is Extrusion Blow Molding
3. What is Injection Blow Molding
4. Extrusion vs Injection Blow Molding in Tabular Form
5. Summary – Extrusion vs Injection Blow Molding
Extrusion blow molding can be described as a type of blow molding in which plastic is melted and extruded into a hollow tube to form a parison (a tube-like piece of plastic with a hole in one end). Thereafter, the parison is captured in a water-cooled metal mold, and the air is blown into the parison, inflating it into the shape of a hollow bottle or container. After cooling down the plastic sufficiently, we can open the mold to eject the part.
Generally, straight extrusion blow molding can be described as a way of propelling materials forward, and it is similar to injection molding at some steps. In this process, we can use the accumulator method, where an accumulator gathers melted plastic. When the previous mold has cooled and when enough plastic has been accumulated, a rod is used to push the melted plastic, and it forms the parison. There, the screw can turn continuously or intermittently. The continuous method causes the weight of the parison to drag itself, and it makes calibrating the wall thickness difficult.
Injection blow molding is a process useful for the production of hollow glass and plastic objects in large quantities. It is also abbreviated as the IBM process. In this process, the polymer is injection molded onto a core pin that can be rotated to a blow molding station that needs to be inflated and cooled. However, injection blow molding is the last used method among the three blow molding processes. Typically, it is useful in making small medical and single-serve bottles. This process has three steps named injection, blowing, and ejection.
An injection blow molding machine has an extruder barrel and screw assembly that can melt the polymer. Thereafter, the molten polymer is fed into a hot runner manifold and is injected through nozzles into a heated cavity as well as the core pin.
Blow molding is a process of forming and joining together hollow plastic parts. Generally, the manufacturing processes use three types of molding processes: extrusion blow molding, injection blow molding, and injection stretch blow molding. The key difference between extrusion and injection blow molding is that extrusion blow molding involves extruding a heated material, whereas injection blow material involves injecting heated material into a mold. While extrusion blow molding typically creates 2D products, injection blow molding typically creates 3D products.
The below infographic presents the differences between extrusion and injection blow molding in tabular form for side-by-side comparison.
The key difference between extrusion and injection blow molding is that extrusion blow molding involves extruding heated material, whereas injection blow molding involves injecting heated material into a mold. In addition, extrusion blow molding typically creates 2D products, while injection blow molding typically creates 3D products.
Reference:
1. “Extrusion Blow Molding.” Find Suppliers, Processes & Material.
Image Courtesy:
1. “Blow molding process” By Basant Nayak – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “Principe extrusion soufflage polymere” By Cdang, Brendan Rockey, University of Alberta Industrial Design, Christophe Poret – Own work, from http://en.wikipedia.org/wiki/File:Injection_molding.png (CC BY-SA 3.0) via Commons Wikimedia
Manufacturers have a clear idea about the difference between the two main processes of blow Moulding. However, to a layman, the entire concept may sound difficult to comprehend. To ease up this confusion, we will clearly spell out the differences between extrusion blow Moulding and injection blow Moulding.
EXTRUSION BLOW MOULDING PROCESS
It is a type of blow Moulding whereby the plastic is first melted at boiling temperatures. This melted plastic is then extruded into a tube. This tube is usually hollow. A better name for it will be prison. Air is then passed through it so that the plastic takes up the desired shape and be inflated. The plastic is then allowed to cool down. Once it is sufficiently chilled, the mould is opened and the item is ejected.
The products of Extrusion Blow Moulding Machines are Automotive Ducts, Traffic Safety Products, Stadium Seating and Chairs, Containers, Trays, Reservoirs, and Tanks, Coolers, Floats, Stands, Panels, and Doors, Toys and Sporting Goods, Watering Cans and Household Products and many more products.
It is again a type of blow Moulding process whereby a polymer is injected into a core pin. This pin is then allowed to rotate to a blow Moulding station where it is cooled and inflated. It is the least preferred blow Moulding process as it is used to manufacture only select items like small syringes.
The products of Injection Blow Moulding Machines are jars, dropper bottles, ovals – cylindrical and boston rounds, one piece roll-on deodorants, tablet and pill bottles and many more other products.
The first difference lies in the type of product which is produced by the respective processes. The extrusion blow Moulding process creates a two-dimensional product whereas the injection blow Moulding process creates a three-dimensional product as the final output. The second difference lies in the tool that is used in both the processes. For the former, a die is used to get the final output whereas the latter employs the use of a mold. The third difference is in the time taken to produce the final output with the two processes. The extrusion Moulding process is slower whereas the Injection Moulding process is faster. The kind of scrap or residue that remains behind makes for the fourth difference between the two processes. With the former, the scrap is with flash and trimming whereas, in case of latter, the scrap is without flash and trimming. The fifth difference is with regard to the part thickness of the machine used in both the processes. In case of extrusion, the part thickness depends on how much the material can be stretched during the process whereas, in case of intrusion, it depends upon the relationship between the core and the mold.
Extrusion Moulding is regarded as a pocket-friendly process when compared to injection Moulding. However, the quality of materials that are used varies from extremely poor to excellent. Styrene is a very poor material that is often used in this process. HDPE is excellent whereas PP and PC are just moderately good for use in the extrusion process.
The quality of all the four materials namely Styrene, PP, PC, and HDPE are excellent in the injection process. Hence it is a comparatively costly process.
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If you operate a business that requires specially formed plastic bottles or containers, such as juice and water bottles or liquid soaps and shampoos, it’s to your benefit to understand the various manufacturing processes for making those bottles and containers.
Having an understanding of the different manufacturing processes and knowing what method is best suited to product production, is important for all aspects of prototyping, planning, manufacturing, and costing.
There are various methods followed such as EBM, IBM, IM etc. Today we are talking about EBM VS IBM.
Both injection blow moulding and extrusion blow moulding processes are essential for many manufacturing purposes. 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 moulding and extrusion blow moulding, we’ll go over how each process works so that you can determine which is best for your needs.
BLOW MOULDING MACHINE
Extrusion blow moulding (EBM) is a manufacturing process whereby plastic is melted and extruded into a hollow tube called a mould. The parison is held and sealed in the metal mould. Air is then blown into the mould, thereby shaping it into the desired shape of the bottle or container. Once the plastic has cooled, the mould is opened and the part is discharged.
IBM shares many technological characteristics with conventional injection moulding. Many of the techniques for reducing energy use in injection moulding can be simply and directly transferred to IBM. These include improved setting, barrel insulation, improved motors and drives, all-electric machines, improved control of ancillaries and improvements in tool design. The additional blowing step needs control but does not add much to the direct energy use of the machine, although it adds it through the increased use of services such as compressed air for blowing.
IBM is primarily a process used for packaging and articles with less weight & high accuracy.
The main difference between blow moulding and injection blow moulding is that blow moulding is used for making hollow parts like water bottles and liquid soap containers. One of the key benefits of blow moulding is that it can be used to manufacture complex shapes – something that can be of tremendous value for such things as product branding and identity.
The injection blow moulding (IBM) process uses an injection moulding machine rather than an extruder to produce the precursor. This precursor is called a preform rather than a parison as in extrusion blow blowing (EBM). A major advantage in IBM vs. EBM is that the preform shape can be designed to receive a more consistent or desired wall thickness when Blow Moulding. The process consists of blowing a molten thermoplastic against the inside walls of a female mould cavity and chilling it to a rigid solid product. The IBM machine has an integral injection unit and a multi-impression mould assembly in which the mould cores are usually mounted on a rotary table.
These techniques are used to create many disposable and recyclable plastic parts, including products used in medical and research applications. Both processes emphasise 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.
INJECTION BLOW MOULDING MACHINE
There are three main areas in which injection blow moulding and extrusion blow moulding differ.
Extrusion blow moulding is most commonly used to form products out of:
High-density polyethylene (HDPE)
Polypropylene (PP)
Polyethylene terephthalate (PET).
Injection blow moulding is most commonly used to form products out of:
Acrylic
Polycarbonate
Polyoxymethylene (POM)
Polyethylene (PE)
The principal difference between IBM and EBM is the type of products they create. IBM is typically used to form more solid parts which are less in weight & need accuracy. 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 blow moulding can produce large volumes of quality parts quickly and accurately.
For IBM, there needs to be a high precision match between both halves of the mould to enable total control over the flow of resin. Most of the work involved in injection blow moulding involves producing the mould. In EBM, there is a higher level of design flexibility between both mould halves since each half forms its wall shape.
EBM Advantages
Low initial mould tooling costs.
The flexibility of tooling; moulds can accommodate interchangeable neck finishes.
Container sizes can range from less than 1 oz. to 55 gallons.
Container shape is not restricted; bottles can be long and flat or have handles.
Wide selection of machinery; tooling can be specifically geared to package volume requirements.
EBM Disadvantages
Containers have a flash that must be trimmed and reclaimed.
Unit cost is significantly higher than injection blown bottles in less than 5 oz. capacity.
Operator skill is critical to control container weight and quality.
IBM Advantages
Scrap free process; bottles require no trimming operation.
Neck finishes are injection moulded (not blown) at a high level of accuracy.
Weight control is extremely precise and material distribution is uniform.
Unit cost is extremely low for small capacity containers (5 oz. or less).
IBM Disadvantages
High tooling cost.
No mould flexibility.
Not economical over 16 oz. capacity.
Container shapes are limited to a blow-up ratio of 3:1 or less (diameter of container to diameter of neck finish).
Not well suited for handle ware.
While the final shape required for a part often dictates the process used, both extrusion and injection moulding have their advantages.
The choice between IBM and EBM, true of all packaging-related choices, should reflect application specifics. Acknowledging the difference in words, the following are some generalizations about specifics:
The type of container can be determined; for example, containers that have handles are better suited for EBM, while wide-mouth containers are better suited for IBM;
If the tightest tolerances (especially in the neck finish and in wall thickness) are required, the nod should go to IBM;
Regarding coextrusions, the more complex the structure, the more it favours EBM;
EBM generates scrap (in the forms of flash and trim), although they’re fed back into the process, IBM generates no such scrap;
When factoring in mould costs, it should be borne in mind that IBM requires two types of moulds but EBM only one; and,
With the issue of overall costs casting its shadow, the greater the annual quantities the more conditions point to IBM.
Overall, we know the simple difference between EBM and IBM is that; in the type of product which is produced by the respective processes. The extrusion blow Moulding process creates a two-dimensional product whereas the injection blow Moulding process creates a three-dimensional product as the final output.