Part production requires careful consideration and planning regarding both the material and process selection. Injection moldingvs extrusionis a popular debate because both processes can create repeatable plastic parts at a competitive speed. However, they have some differences as well.
The following text will take a brief look at the main differences between the two processes and discuss which one is the better alternative for part production.
The Main Differences Between Extrusion and Injection Molding
Both extrusion and injection moldingare common plastic parts production processes. However, there are significant differences between the two methods pertaining to the process fundamentals, compatibility, strength, and precision. All these factors combine to affect the overall cost and time of the process, which in turn affects the overall costs and capabilities of both methods.
The basics of both processes are the same. Plastic is heated to deform and take the shape of a certain dye, but this is where the similarities between injection molding and extrusion end. The remaining processes are entirely different and require different approaches.
Extrusion, for instance, melts the plastic and pushes it through a certain shape. Resultingly the extruded product, called an extrudate, takes the form of the dye and cools down to solidify.
The injection molding process is completely different. The plastic does melt but it’s not pushed through a dye or any other shape. Instead, the liquified plastic goes inside the injection mold with cavities of the required shape. The plastic then cools down inside the mold to solidify and is finally ejected for the next cycle. The process takes place in 4 states and the picture below depicts those.
Injection molding produces almost all thermoplastics and most thermoset plastics. This enables the production of permanent and recyclable components like nylon and acrylic. Extrusion only supports thermoplastics like PVC.
The melt strength is an important parameter when it comes to plastic-related processes. By comparison, the melt strength for injection molding is lower than that of extrusion because the product is ready by the time it exists in the mold cavity.
Extrusion is different because the product doesn’t get cured and may even require some subsequent processing like thermoforming depending on the application. Therefore, the melt strength requirements for extrusion are quite high when compared to that for injection molding.
Injection molding relies on a machine consisting of a clamping and injection unit. Moreover, the toolingwith the right design cavity is another requirement of the process. On the other hand, extrusion only requires a non-rubber extruder.
When it comes to precision, injection molding performs a lot better than extrusion. Injection molding is much more suitable for the design complexities of 3D objects. However, that capability to handle design complexities requires significant mold preparation time. Extrusion, on the other hand, is not as precise but delivers quick results.
Just like the difference in precision, injection molding and extrusion deliver different results. Injection moldingis generally more suitable for complex 3D shapes because of the process requirements. The mold for the process can be machining or 3D printing which results in more versatility. However, extrusion is limited when it comes to the products. It’s mostly restricted to 2D shapes, which handle really well and delivers consistent results.
There is a significant difference between injection molding and extrusion when it comes to cost. Injection molding is generally more expensive and most of it is because of the mold costs. The mold needs to be either machined or 3D printed depending on the design’s complexity. Furthermore, the material also plays a significant part in determining the cost of injection mold. The better the material, the longer will the mold last but that will come at a cost.
The extrusion process, on the other hand, is much simpler and handles 2D shapes without any intricacies. As a result, the operating costs of the process are lower but remain unaffected by economies of scale. Moreover, the overall setup costs for extrusion can be quite high considering the restriction on complex designs.
Both injection molding and extrusion work well with plastics. However, injection molding is more suitable for complex closed 3D shapes, like vehicle interior room components. These plastic components have a complex initial dye which significantly increases the capital costs but remains operational for many cycles.
Contrarily, extrusion is an ideal choice for continuous objects or repeatable parts with the same cross-section. For instance, PVC frames, pipes, and other similar objects with continuous cross-sections will almost always rely on extrusion for production.
Overview of Injection Molding
Injection molding is a process that converts plastic resin to complex plastic products using heat, pressure, an injector, and a mold. At the right temperature and pressure, a good flowing melt will take up the shape of any well-built mold to produce high-quality finished plastic components.
Injection molding is a higher quality product manufacturing process than CNC or 3D printing that can maintain intricate precision and eliminate the need for post-processes. Furthermore, it’s highly repeatable and gets affected by economies of scale. Thereby making it an effective choice for industrial production.
There are numerous other advantages of the injection molding process. Some of the most important ones are:
One of the key advantages of injection molding is the repeatability and precision it offers. The average tolerance of injection molds is around +/- 0.005 inches but it’s possible to further reduce it and enhance the overall precision of the part.
Compatibility With Various Plastics
Another capability that makes injection molding excellent is its almost universal compatibility when it comes to plastics. The process is suitable for almost all kinds of plastics which makes it unique and allows greater versatility from a product development perspective.
Building on to the previous point of precision, the consistency of injection molding machines is another factor that makes this process so great. The injectionmolding process generally creates hundreds to thousands of the same partsand all of them will have the same geometric properties as long as the mold is correct.
There are two factors to this quality. Firstly, injection molding machines can handle multiple parts in the same cycle, which means better economies of scale and more efficient production. Secondly, most injection molded parts don’t need any post-processing, which means that they are ready for the market as soon as they are ejected. Thereby enhancing overall productivity by delivering ready-for-market products sooner.
Surface Texture Options
This is an optional feature, but injection molded parts can have a surface texture to enhance the functionality or aesthetic outlook depending on the particular application. A good quality mold will always help produce plastics with a smooth surface demeriting the need to reprocess the surface after demolding.
Economies of Scale
Raw material pellets are cheap. A single mold used in high repetitions, decreases the cost further. Design complexity in molds is achievable and transferred to the final plastic product. Variety in possible color palettes and surface finishes is enough to dazzle a selector, and manufacturing speed is great, bringing down mold-to-consumer time for each piece.
While plastic injection molding has a lot of advantages, there are a few drawbacks as well. Here are a few of the main issues:
High Set-Up Costs
The injectionmolding process is expensive to set up as there are a lot of costs involved. The machine, the mold, and other associated costs can quickly become significant. Costis a concern for small to medium manufacturing units.
Long Initial Lead Times
Injection molds are an integral pre-requisite of this process and preparing them requires a lot of time and resources. This adds to the overall lead times of the project and may have a negative impact on the overall performance.
Not Suitable for Low-Volume Production
Injection molding can be really cost-effective, however,that only happens when there are enough parts produced. For low-volume production, the process can be quite expensive because of the associated costs, mainly related to mold creation.
Overview of Extrusion Molding
In the simplest terms, plastic extrusion is an overall process where a liquid plastic goes through a particular cross-section and adopts its shape during the process. There are a few other requirements related to the temperature and pressure as well; because the extrusion process requires the plastic to contain its shape as it comes out of the dye. Today the industry generally uses a screw extruder.This maintains the right amount of pressure and delivers the best results in the shortest time.
Extrusion is among a few processes that are remarkably similar for both metal and plastics. Plastic extrusion has a plethora of advantages, and the following are a few of the main ones:
The best part about the plastic extrusion process is the overall effect on the costs. The process is an ideal choice for non-complex 2D parts as it delivers consistent, quick, and quality results in the shortest time.
Excellent Surface Finish
Plastic extrusiondoesn’t require any post-processing.Plastic is forced through a limited opening with a lot of pressure, which doesn’t let any air bubblesor other deformities remain inside. Thus, the surface finish it delivers remains great.
Extrusion is an ideal choice for high-volume production.It can churn out numerous parts of the same design continuously. This makes it ideal for high-volume production. However, it’s important to note that the process doesn’t deliver the same level of economies of scale as injection molding.
No matter what kind of 2D design it is, extrusion molding can handle it like a charm. Furthermore, the process can handle many types of plastics with simplicity. Therefore, it is quite common across the industry.
Extrusion is a great choice for basic plastic part production but has a lot of disadvantages as well. Here are some examples:
One of the key limitations of the extrusion process is its inability to handle deviations in the cross-sectionor size. Any change would need a separate dye, which can potentially cause delays.
Given the limitations of extrusion relative to injection molding, the overall set-up costs are quite high. Thiscan cause the overall costs to exceed expectations.
Both extrusion and injection molding deal with heated plastic which createsseveral environmental concerns. However, extruded products are not as durable, which further intensifiesthe environmental impact of the process.
Injection Molding vs Extrusion: The Better Choice
Extrusion vs injection moldingis an essential debate for anyone in the plastic manufacturing business. However, there is unfortunately no clear winner between the two. Both processes come with their own sets of merits and demerits, but the best choice depends on the nature of the application.
The intricacies of the design, along with the capabilities of the process are only some, albeit important considerations while choosing between molding or extrusion. However, the cost required quality, and the available time is also equally important as many projects are both time-sensitive and require the perfect optimization between quality and price.
Furthermore, these two processes have very similar scientific bases and different use cases in industrial manufacturing. Injection molding’s forte is producing complicated plastic, with high finish requirements very specific three-dimensional, and low tolerance sizing. Extrusion is a lower-cost process that enables two-dimensional sizing restrictions to long continuous masses of plastics.
In conclusion, both processes can be the right choice depending on the specifics of the application. Extrusion might not be possible in some cases because of design complexities. However, that restriction doesn’t apply to injection molding services. However, in many cases where cost and time are among the primary constraints, extrusion can be a viable choice as it delivers good quality and delivers faster results.
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For instances where the customer isn’t sure about the better process, RapidDirect’s team of experts can help out in determining the right methodology based on the specificities of the project. Moreover, we provide plastic injection and extrusion mold manufacturing, overmolding, and insert molding and deal in many classes of purpose-specific molds and a variety of plastic finishes.
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Simply put, the EXTRUSION process is required to create continuous linear, two-dimensional shapes. INJECTION MOLDING produces three-dimensional shapes that do not remain constant in a parallel line.What is the difference between molding and injection molding? ›
In general, blow molding is used to make singular, hollow products like bottles and beakers. Injection molding makes solid parts, like plates and discs, or is used to produce solid parts or pieces for plastic products.What are the similarities between extrusion and injection molding? ›
At an initial glance, extrusion and injection molding may appear to be very similar manufacturing processes. Both processes send molten material through machines to mass-produce low-cost parts of the desired shape. Both are a continuous production processes that amortizes costs as one orders higher quantities of parts.What is a unique feature of products made with extrusion as compared to injection molding? ›
Another key difference here: While injection molding can produce three-dimensional parts that have incredible detail, extrusion molding is generally limited to two-dimensional parts. It's more typically used for creating flat, rectangular products like pipes and tubing, rather than complex three-dimensional shapes.What is the process of extrusion? ›
Extrusion is a process where a material undergoes plastic deformation by the application of a force causing that material to flow through an orifice or die. The material adopts the cross-sectional profile of the die and if the material has suitable properties, that shape is retained in the final extrudate.What is an example of extrusion molding? ›
Extrusion Blow Molding(Moulding) Products made by Extrusion Blow Molding Machines are milk or water bottles, shampoo bottles, automotive air ducts, jerry cans, and hollow industrial preform parts such as plastic drums or other plastic containers.What is extrusion molding process? ›
Extrusion molding (also known as plastification extruding) is a process that the stack of powders or the green body in die is pushed out to assume another form of green body or other final product under pressure.What are the 4 stages of injection molding? ›
The whole injection moulding process usual lasts from 2 seconds to 2 minutes. There are four stages in the cycle. These stages are the clamping, injection, cooling and ejection stages.What is the definition of extrusion? ›
The process of making a shaped object, such as a rod or tube, by forcing a material into a mold.What is the difference between extrusion grade and injection grade? ›
In an injection molding, high viscosity rate of material is used, while in an extrusion medium viscosity rate is used.
However, extrusion moulding offers such benefits as lower production costs due to excess plastic being able to be collected and reused. The products can be recycled due to the properties of the plastic polymers used, making the process more sustainable, cutting down on excess plastics use and reducing disposal costs.What is an example of material extrusion? ›
Examples of material extrusion technology include composite filament fabrication (CFF), fused filament fabrication (FFF) and fused deposition modelling (FDM). Similar to other 3D Printing processes, material extrusion involves drawing material through a nozzle where it is heated and deposited layer by layer.What are 3 products made by extrusion? ›
Extrusion produces items such as pipe/tubing, weatherstripping, fencing, deck railings, window frames, plastic films and sheeting, thermoplastic coatings, and wire insulation.What are the five process parameters of extrusion moulding? ›
The variable parameters of extrusion process are mean barrel temperature, screw speed, die temperature, take up unit speed, water tank temperature, and die nozzle diameter.What products are made by extrusion molding? ›
Extrusion is a manufacturing process used to make pipes, hoses, drinking straws, curtain tracks, rods, and fibre. The granules melt into a liquid which is forced through a die, forming a long 'tube like' shape. The shape of the die determines the shape of the tube.What are the different types of extrusion molding? ›
The extrusion blow moulding process can be broken down into two subcategories: Continuous extrusion blow moulding and Accumulator (Intermittent) extrusion blow moulding. In continuous blow moulding, the plastic is extruded constantly while the machine runs.What is an example of injection molding? ›
Injection molded products include plastic syringes, tools used in medical procedures, implantables, imaging components, IV connections, prosthetics, beakers and test tubes, and housings and casings for medical equipment.What are the 5 elements of injection molding? ›
The five elements that injection moulding needs to meet is temperature, speed, pressure, position and time. These five factors determine the quality of injection moulded parts.What are the 3 main parts of the injection mold? ›
An injection molding machine is comprised of four main components: the base, the hopper, the barrel, and the clamping unit.What are the basic principles of injection molding? ›
The principle of injection molding is very simple. The plastic material is heated above its melting point, resulting in the conversion of the solid polymer to a molten fluid with a reasonably low viscosity. It is then forced into a closed mold that defines the shape of the article to be produced.
If the flow rate is too high (i.e. too much filament is being pushed through the nozzle) it can lead to over extrusion and poor print quality. Incorrect flow rates can also lead to under extrusion, another common problem in FDM 3D printing. Flow rate controls how much filament is fed through the 3D printer nozzle.What are extrusion products? ›
Extrusion is a mechanical process in which certain materials are forced, under pressure, through a die opening to create products of a desired shape, size, and/or texture.What does extrusion mean in 3D? ›
According to the ASTM International standards organization, extrusion is the official name given to a specific 3D printing process where material is selectively dispensed through a nozzle or orifice.What is the formula for extrusion? ›
The total extrusion pressure (p) in MPa for the above process is related to extrusion ratio (r) as σ p = K s σ m [ 0.8 + 1.5 l n ( r ) + 2 l d 0 ] where σm, is the mean flow strength of the billet material in MPa, l is the portion of the billet length remaining to be extruded in mm, d0 is the initial diameter of the ...What machine is used for extrusion? ›
An extruder is simply the machine used to complete the extrusion process. Using a system of barrels and cylinders, the machine heats up the product and propels it through the die to create the desired shape.What are the different methods of extrusion? ›
There are different types of extrusion processes, however, including cold, hot, friction and micro.Why is extrusion better than casting? ›
Metal extrusion does have some advantages over die casting. When using certain materials, including alloys made from aluminum, magnesium, and zinc, extruded parts have strength and rigidity values similar to die cast parts, but ductility can be higher.What is the best steel for extrusion? ›
What do we use? For our extrusion dies we often use 1.2343 steel. Hot work/work steel with excellent toughness combined with high thermal stability, high resistance to thermal shocks, good thermal conductivity, limited water cooling possible.What is one advantage of injection Moulding? ›
It minimises moulding costs, and is a highly repeatable way of producing plastic or elastomeric parts with high precision. Once set up, it can produce a huge amount of parts per hour from a wide range of different plastics plus other materials such as liquid silicone rubber.Why do we use extrusion? ›
The extrusion process also offers an excellent surface finish to parts and gives considerable freedom to form in the design process. Extrusion processes are similar to drawing, which uses the tensile strength of the material to pull it through the die. The drawing process is used to produce wire, metal bars, and tubes.
Disadvantages: The nozzle radius limits and reduces the final quality. Accuracy and speed are low when compared to other processes and accuracy of the final model is limited to material nozzle thickness. Constant pressure of material is required in order to increase quality of finish.What are the advantages of plastic extrusion? ›
Money saver: plastic sheet extrusion is efficient and also low cost. It is considered the most economical manufacturing option for plastic products. Plastic extrusion machines operate continually which reduces time wasting and allows for 24-hour manufacturing.What is extrusion in injection Moulding? ›
What is Extrusion Moulding ? Extrusion moulding is used to form plastic or metal materials into a pre-defined shape. During the process, the material is melted and pushed through an extrusion moulding machine, forming a long, tube-like shape or rod. This is cooled and cut to the required length.What is the process of injection molding? ›
Injection molding is a process in which a thermoplastic polymer is heated above its melting point, resulting in the conversion of the solid polymer to a molten fluid with a reasonably low viscosity. This melt is mechanically forced, i.e.,injected, into a mold in the shape of the desired final object.What is extrusion process in plastics? ›
Plastics extrusion is a normally high volume manufacturing process where a polymer material, enriched with the desired additives, is melted and formed in a continuous process. The raw material (polymer) in the form of granulates, is gravity fed into the hopper and through the feed throat, drops on a rotating screw.How many types of extrusion are there? ›
There are different types of extrusion processes, however, including cold, hot, friction and micro.What is the difference between extrusion and casting? ›
You might find yourself asking, “What is the difference between extruding and casting of aluminum?” Extrusion is a process by which aluminum billets are forced through a die, resulting in a desired cross section. Whereas, casting is a process in which molten aluminum is poured into a mold and then allowed to solidify.What is extrusion Moulding also known as? ›
Extrusion molding (also known as plastification extruding) is a process that the stack of powders or the green body in die is pushed out to assume another form of green body or other final product under pressure.What is the major problem in extrusion? ›
One of the major problems in hot extrusion is the effect of hot metal on the equipment. Various methods are used to protect the dies. The die may be changed and allowed to cool for each piece.What are the advantages of injection Moulding? ›
- Efficient high production. Once you have developed the moulds, the process is extremely fast with cycle times as short as 10 seconds. ...
- Low cost per part. ...
- Repeatability. ...
- Large material choice. ...
- Low waste. ...
- High detail. ...
- Little or no post processing. ...
- Initial cost.