Raw material for injection moulding

Materials for injection moulding

The injection molding process involves different types of materials, and each performs a unique function. These materials include:

• Thermoplastics

  Thermoplastics have a special characteristic where they become soft and malleable when heated. It thus makes them reshapeable, enabling them to become very firm when cooled. These plastics are very notable for their properties of recyclability. They thus make them very suitable in the production of complex and very detailed parts. Some frequent examples business should get well acquainted with are Acrylonitrile-Butadiene-Styrene (ABS). Others include Polypropylene (PP), also known as polystyrene, and polycarbonate (PC). More often than not, these materials serve the automotive, electronics, and consumer goods sectors and manufacturing.

• Elastomers

  Elastomers are predominant due to their unique flexibility and ability to return to their structures after deformation. They thus become a fitting material in production, especially when subjective to varying shapes and patterns. Depending on the business's needs, these materials should be easily formed into seals, gaskets, or even rubber-like parts. Common types consist of thermoplastic elastomers (TPEs), which are easily shaped with thermoplastics. Other types include Silicone Rubber that's heat-resistant and used widely in the field.

• Metals

  Even though metals are not molded, they are still indispensable in mold-making. They are commonly used to cater to certain metal alloys to enhance their properties such as strength to the resultant product. They are also majorly applied in high-performance applications. Some frequent examples are steel, aluminum, and bronze. Do not forget how steel is a common metal used both as a structural component and for production parts that include mold frames. Aluminum, on the other hand, contains great thermal conductivity. It therefore comes in handy during the rapid production process. Lastly, bronze minimizes friction and is therefore ideal for components such as bushings and gears.

Injection moulding process

The injection moulding process consists of well-defined steps that are taken to yield perfectly molded products. These steps include:

• Mold design and preparation

  The very first step of the injection molding process is mold design and preparation. It entails the two-party collaboration of engineers and clients. They, therefore, create the mold based on the customer's identified needs. Usually, molds are fabricated from high-grade steel or aluminum. These two materials are selected due to their high durability and ability to bear heat. The design is then put into a molding machine after the preparation is complete.

• Melting and Injection

  In this phase, the selected material, quite often in the shape of plastic pellets, gets fed into a heated barrel of the injection machine. Here, the materials experience heating until they attain a viscous state. The molten materials are then injected under pressure into the prepared mold cavity. Usually, this is conducted using a reciprocating screw mechanism.

• Cooling and solidification

  The mold is allowed to cool for a little while after it's filled with the injected material. Cooling causes the material to solidify and subsequently take the shape of the mold. The time taken for this stage is solely dependent on the complexity of the molded product and the type of material that was used.

• ejection

  Once the material is solidified, the mold then opens, and ejector pins are used to gently extract the molded product. The mold release agents are sprayed in the mold prior to ejection to minimize chances of active and permanent adhesion between the mold and the product.

• Finishing

  The finished product goes through trimming and post-processing. That is, if there exists any excess material such as sprues or runners is removed. Other operations such as painting, assembling, or even installing components can be done at this stage.

Benefits of choosing injection moulding

Injection moulding has a multitude of benefits. These benefits include:

• Precision and consistency

  The main advantage of the injection moulding is precision and consistency. It offers business's high levels of accuracy in the produced parts. Not to mention how crucial this factor is for industries such as aerospace or electronics. Moreover, it also guarantees consistency in the produced batch, thus eliminating the variability that is likely to occur when manufacturing parts.

• Cost-effective

  Usually, when the production volumes are high, injection moulding becomes very economical. The reason behind it is that the initial setup costs are offset by the reduced costs per unit in the long run. It thus allows businesses to meet large demand without incurring large costs.

• Complex designs

  Are businesses looking to produce parts with intricate designs? Then injection moulding comes to the rescue. It is because the process easily accommodates complex geometries, including holes, curves, and detailed features. Such capabilities enable businesses to take advantage and offers them competitive edges in the market.

• Material variety

  Another key advantage that comes with injection molded materials is its recyclability. It is also worth noticing how the injection molding process involves the utilization of a wide range of materials. Some of which include thermoplastics and metals. Thus offering businesses a myriad of choices to cater to their specific needs. Additionally, many of these materials are not only durable but also lightweight. Therefore making them very ideal for a multitude of applications.

• Quick production

  Injection moulding is quite effective in quick production processes. This is because the molds enable quick cycles to take advantage of high throughput. Henceforth this efficiency is particularly beneficial to businesses operating in markets that are engulfed with demands.

Factors that affect the choice of raw materials for injection moulding

The following factors affect the choice of raw materials for injection moulding.

• Thermal properties

  Thermal properties have such an important effect on the material's fluidity during the injection phase. They also affect its stability when exposed to the mold's temperature. This directly impacts the product's shape retention and dimensional accuracy. If not careful, materials with incompatible thermal properties can result in warped products. Moreover, they come characteristic with poor surface finish. Therefore, selecting a material that meets ideal thermal properties for a specific material is a must for achieving optimal molding results.

• Mechanical strength

  Mechanical strength refers to tensile strength, impact resistance, and hardness. All these have a direct implication as far as the durability of the molded product is concerned. Therefore, in application, products that require high loads or stress exposure need materials with increased strength. Normally, such materials incorporate reinforcement additives such as fibers to bolster their rigidity and toughness.

• Viscosity

  Also, material viscosity during processing plays an important role when it comes to stable and high-quality molded products. Generally, low-viscosity materials allow easier injection into the mold. Henceforth this property avails good filling. On the flip side, highly viscous materials may prove troublesome during injection. This can cause incomplete filling, which can lead to production defects. It is therefore paramount to select a material with ideal viscosity, especially when considering the complexity and intricacy of the mold design.

• Chemical resistance

  The resistance of chemicals to a certain material can significantly affect its applicability in different industries. In most cases, products that are used in hostile environments such as chemicals or high temperatures need materials that resist these substances. Also, these resistant materials come with the ability to retain their properties when exposed to various chemicals. Unfortunately, they are often affected by corrosion, degradation, or loss of strength. Therefore, assessing the product's end-use environment is critical in determining the required chemical resistance of the chosen material.

• Surface finish

  The surface finish of molded products is usually determined by the material used in molding. Worth noting is that a material's characteristics come with a special texture, gloss level, and color. Typically, they affect the products' aesthetic appeal and functionality. Also, some materials incorporate easier molding surfaces than others. Such materials include thermoplastics that are ideal for producing glossy and smooth surfaces. Conversely, materials that have higher porosity may result in dull or rough surfaces.

How to choose high-quality injection moulding materials

Some of the most effective ways to choose high-quality injection moulding materials entail being conversant with the following materials' characteristics. They are:

• Thermoplastics

  Thermoplastics are one of the most preferred materials in injection moulding. This is due to their remarkable plasticity property when receiving heat. They, therefore, give molds intricate shapes before solidifying. In addition, these materials come with a high level of recyclability. Notable examples include Acrylonitrile Butadiene Styrene (ABS) plastics that are commonly used in producing durable consumer products and Polycarbonate (PC) plastic that is molded into impact-resistance parts.

• Elastomers

  The other material that has gained notable popularity in injection moulding is elastomers. It is mainly due to their elasticity. Such a material comes quite in handy when producing automotive components that require flexibility as well as shape retention. Also, thermoplastic elastomers (TPEs) find their usage in the manufacturing of medical devices. Normally, they contain good feedback on making prototypes.

• Metals

  Another material commonly used in commercial metal injection molding is metals. These materials take advantage of their ability to create precision components like gears. They are typically preferred in industries that deal with mechanical applications. Often, materials like aluminum alloys provide a great compromise between strength and weight. Commonly, they serve as aging aircraft parts and automobile components.

• Biodegradable plastics

  Biodegradable plastics are manufactured from renewable resources. Henceforth, they become a sustainable option for environmentally-conscious industries. In most cases, they are used in packaging applications that require temporary durability. Normally, polylactic acid (PLA) plastics are produced from cornstarch and is capable of breaking down naturally over time. More often than not, manufacturers use them in producing medical implants that will eventually be absorbed by the body.

• Composite materials

  Composite materials come with varied reinforcement that includes fibers. This characteristic improves the mechanical properties of the molded product. Usually, they offer a sought balance between lightness and strength. Commonly examples consist of glass-fiber-reinforced plastics (GFRP) popular in car manufacturing and carbon-fiber-reinforced polymers (CFRP) in high-performance sports equipment. They also come with enhanced durability, and this makes them ideal for applications that are demanding.