This article will take an in-depth look at plastic trim.
The article will bring more detail on topics such as:
In this chapter, we will delve into the foundational aspects of plastic trim, encompassing its manufacturing methodologies.
Plastic trim items are fabricated through a process known as extrusion, resulting in continuous profiles that can be manufactured in varying lengths. These trims are extremely adaptable due to their ability to bond, secure, and provide sealing. A variety of materials, including HDPE, LDPE, butyrate, PVC, acrylic, and vinyl, are employed in producing these extrusions and trims for multiple industries. Among them, PVC is the most commonly utilized material for manufacturing plastic trim.
Plastic trim is widely used in the construction sector, serving purposes such as window insulation, indoor and outdoor siding, door frame sealing, and protective bumpers for sharp corners and edges. In the appliance industry, trims made of flexible vinyl and PVC are used for sealing microwave and stove doors. The automotive sector also incorporates plastic trim for both exterior and interior fenders. Additionally, it sees use in furniture, recreational, and marine industries. Notable examples include edge trim, decorative in-house trim, fender flare trim, U trim, drip rail trim, lip trim, and J trim.
Plastic profile molding is distinct from injection molding as it generates two-dimensional shapes rather than three-dimensional products. The process of creating plastic profiles is straightforward and cost-effective. The technique involved is plastic extrusion, where polymer material is continuously melted and shaped, adjusting properties as needed with additives.
Initially, raw thermoplastic material is fed into an extrusion barrel through a top-loaded hopper. The polymer granules are gravity-fed into the hopper, falling onto a rotating screw driven by an electric motor in the feed throat. The design of the screw varies depending on the material and design of the final product.
Next, the rotating screw advances the plastic into a heated barrel. As it moves forward, the screw's channel or thread becomes progressively narrow, compressing the material. The barrel is equipped with multiple Proportional Integral Derivative (PID) controllers, each managing different temperatures to regulate consistent heat.
Depending on intended applications, certain additives such as colorants, UV stabilizers, or other compounds may be introduced to enhance the properties of the plastic trim.
When the plastic is thoroughly heated, it continually passes through a specially designed die opening to form blocks. The heat required to melt the plastic exceeds that set by the controllers, with the additional warmth generated by compressive forces and shear friction. Upon reaching the end of the screw, the molten plastic is thoroughly mixed and filtered through a screen pack secured by a breaker plate to remove impurities and eradicate rotational memory. The pure, molten plastic is then extruded through the die to achieve the desired trim profile. After leaving the extruder, the plastic trim is cooled and collected. The cooling method is determined by the design and shape of the trim.
In summary, extrusion is a production technique where material is drawn through a die to create a continuous profile with a consistent cross-section. In extrusion molding, plastic passes through a die, with the die's shape determining the cross-sectional profile of the final trim product.
The manufacturing process can be outlined as follows:
Relative to other industrial machinery, extrusion machines are more economical, being less complex and not requiring exceptionally high precision, unlike CNC or injection molding. The dies used in extrusion are also less expensive, with tooling costs a fraction of those associated with injection molding. As with injection molding, extrusion molding is a continuous operation, which contributes to the low cost of extruding plastic trim.
The extrusion process typically creates objects with consistent profiles, such as I-sections, T-sections, U-sections, L-sections, and round or square cross-sections.
When assessing the extrusion process, consider elements like lead time (in weeks), cycle time (in seconds or continuously), setup costs, cost per unit, and its suitability for medium to high-volume production (fewer than 1000 parts).
In the United States and Canada, a range of machines is available for producing plastic trim. These machines play a crucial role in modern manufacturing by enabling efficient and economical production of plastic trim components. They are vital for various industries, helping to manufacture key products, minimize waste, and bolster the economy. The following sections highlight some of the top machines used in this process.
The Arburg Allrounder series is renowned for its adaptability and precision. These injection molding machines are available in multiple sizes, providing the flexibility needed to mold a variety of plastic trim components. They feature sophisticated control systems that ensure high repeatability and accuracy during production. Valued for their reliability, speed, and energy efficiency, the Allrounder series is a favored option within the industry.
The KraussMaffei GX series of injection molding machines is highly esteemed for its exceptional performance and cutting-edge technology. These machines are engineered for precise molding with superior control over the process. The GX series boasts features such as efficient drive systems, intuitive controls, and a durable construction. It is widely chosen for plastic trim production due to its capability to manage intricate molds and high production rates.
The Sumitomo (SHI) Demag IntElect series is renowned for its energy efficiency and precise molding performance. Utilizing advanced servo technology, these machines deliver substantial energy savings over conventional hydraulic models. The IntElect series is also capable of high-speed and high-precision molding, making it ideal for creating detailed plastic trim components with stringent tolerances.
The Husky HyPET series is widely used for manufacturing plastic bottles and containers, as well as various plastic trim components. Known for its high-speed production capabilities, this series excels in productivity with its rapid cycle times. Additionally, the HyPET series features quick mold change systems, advanced control mechanisms, and consistent shot-to-shot precision, making it well-suited for rigorous production demands.
The Milacron Maxima series consists of large-tonnage injection molding machines ideal for manufacturing various plastic trim components. These machines are recognized for their durable construction, dependable performance, and high-efficiency hydraulics. The Maxima series ensures excellent repeatability shot-to-shot, which is crucial for maintaining consistent quality in plastic trim production.
It's important to note that the choice and popularity of a specific machine can differ based on the requirements of your plastic trim production process. Before selecting a machine, evaluate your production needs, including the size and complexity of the components, and other relevant factors to ensure the machine meets your business goals.
This chapter will explore the various plastics utilized in plastic trim and the different methods of plastic extrusion.
Plastics come in thousands of base formulations, chemistries, and additives, offering a wide array of aesthetic and functional characteristics. To streamline the process of selecting the most suitable material for a specific component, plastics are categorized into two primary types: thermosets and thermoplastics.
Thermoplastics are the most prevalent type of plastic used in plastic trim applications. Unlike thermosets, thermoplastics can undergo multiple cycles of melting and solidifying without significant degradation, which is their key distinguishing feature.
Thermoplastics are commonly supplied as small bits or sheets heated and shaped into the desired form using different manufacturing processes. The process is totally reversible because no chemical bonding happens, making melting or recycling and reusing thermoplastic feasible.
Some common types of thermoplastics are:
PVC, or polyvinyl chloride, is a versatile and widely used synthetic plastic polymer. It can be found in various forms to suit different applications. When used in its rigid form, PVC is an excellent choice for trim materials due to its durability and flexibility.
This flexible polymer is commonly used to produce plastic films for labeling and packaging. Its excellent resistance to chemicals, acids, and solvents, combined with its low-friction surface and clean finish, helps protect sensitive contents. Additionally, it finds applications in everyday household items, including decorative trim.
PET is a widely used plastic in injection molding due to its attractive finish and suitability for branded products. Known for its strength and durability, PET is also frequently used in textiles under the name polyester. Its ease of recycling further enhances its sustainability, making it a favored choice for a variety of applications.
LDPE, or low-density polyethylene, is a widely recognized thermoplastic derived from petroleum. It is characterized by its flexibility, low tensile strength, and high ductility. LDPE is used in various applications, including trim, food trays, bin liners, plastic bags, computer components, and floor tiles. Its smooth, lightweight surface is easy to clean and maintain.
ABS, or acrylonitrile butadiene styrene, is a popular transparent plastic known for its durability. It is often used as a glass alternative for both aesthetic and safety purposes. ABS can be produced in clear or colored forms to align with branding requirements. It is well-suited for applications such as fender flares, trim, containers for creams and lotions, and children's toys like building blocks. Additionally, ABS is highly compatible with 3D printing technologies.
SAN, or styrene acrylonitrile, is an older plastic used in injection molding that has largely been supplanted by Acrylonitrile Butadiene Styrene (ABS). However, it may still be found in certain industrial applications. SAN is transparent, rigid, and durable, offering excellent hygienic and protective properties. Its polymer chains readily absorb color and print, making it suitable for branded packaging, advertising, and warning signage. Additionally, SAN provides good thermal insulation, which makes it useful for products like trim seals.
Polystyrene is naturally transparent, soft, and resilient to damage from sudden impacts, so it is a valued protective packaging material. Like other polymers, polystyrene can be formed in any size, shape, and color.
The shape of the die determines the type of plastic trim that can be created, utilizing various extrusion techniques as described below:
This extrusion method is specifically used for manufacturing pipes and tubes. During the process, air with positive pressure may be introduced. Once the material exits the die, it is directed into a cooling chamber, where it typically undergoes water cooling.
Extruded tubing, commonly used for medical hoses and drinking straws, follows a process similar to standard extrusion. However, a pin or mandrel is inserted into the die to create hollow sections during extrusion. In some cases, this pin applies positive pressure to the internal cavities.
In certain applications, it’s essential to manufacture tubing with multiple lumens or holes. This is achieved by designing the tooling with several pins positioned within the die’s core. Air pressure from various sources can often be directed at these pins. By modifying the pressure applied to each pin, it becomes easy to adjust the dimensions of the individual lumens.
Blown film extrusion is utilized to produce plastic film tubes through a continuous process. During this method, the molten film is initially cooled as it exits the die, forming a partially solid tube that is then inflated to achieve the desired size and thickness of the film.
This technique is widely used for producing continuous films, often for packaging purposes. The process starts by melting the plastic in an extruder, which then feeds the molten polymer into an annular die head to form a plastic tube. To create multilayer films, separate extruders are used for each material. The molten layers are combined within the die head, resulting in a plastic tube with multiple concentric layers.
Once the film tube exits the die in its molten state, nip rollers lift it upwards. At the same time, compressed air is used to inflate the tube to achieve the desired thickness and width. The tube's outer surface is cooled with chilled air. As the film approaches the nip rollers after cooling, it is gradually flattened into a "lay-flat" form. Finally, the film is conveyed through the nip rolls to roll winders and in-line slitters at the end of the line.
This method is used for extruding plastic films or sheets that are too thick for blowing. After exiting the die, the sheets are cooled and then passed through a series of cooling rollers. The die also controls the thickness of the sheets.
Extrusion is employed to create products like plastic sheets or films. During the extrusion process, cooling is achieved by passing the polymer through a set of cooling rollers, typically three or four. These rollers, also known as calendar or "chill" rolls, ensure proper cooling. However, if the process runs too quickly, a defect known as "nerve" may occur, which results from insufficient time for the heat in the extruded plastic to dissipate properly.
The thickness and surface texture of plastic sheets are determined by the rolls used in the extrusion process, which also provide essential cooling. This is particularly true for specialized rolls, such as smooth, levant, or Haircell rolls. Additionally, co-extrusion is often employed to apply multiple layers, allowing for various attributes such as a soft touch, enhanced grip, UV protection, a matte finish, or energy reflection.
This extrusion method is used to coat wires. The wire is drawn through the center of a die during the process. If adhesion between the coating and the wire is required, a pressure tool is utilized. In this case, the wire is coated with molten plastic while still in the die and is pressurized as it exits. When adhesion is not necessary, a jacketing tool is employed to cover the wire with molten plastic as it leaves the die.
Applying a polymer jacket of varying thicknesses around a core of high-performance fibers provides protection against mechanical, environmental, and chemical damage.
The core fibers can be twisted, aligned in parallel, or formed into a rope shape. The choice of polymer jacket material from a wide range of options is made to ensure optimal flexibility, chemical resistance, temperature stability, and UV protection, tailored to the specific requirements of the application.
When selecting a manufacturing process for plastic trim products, the following factors should be taken into account:
Are the parts characterized by complex internal structures or precise tolerance needs? The design geometry may limit manufacturing options or necessitate significant design for manufacturing (DFM) efforts to ensure cost-effective production.
What is the expected total or annual volume of trim to be produced? Certain manufacturing processes involve significant initial setup and tooling costs but result in lower per-part costs at higher volumes. Conversely, processes suited for low-volume production have lower start-up costs, but due to slower cycle times, less automation, and more manual labor, the per-part cost remains steady or decreases only slightly with increased production volumes.
What is the required production speed for the parts or finished plastic trim? Some methods can produce initial components within 24 hours, whereas setup and tooling for certain high-volume processes may take several months.
What types of strains and stresses will the plastic trim products need to withstand? Choosing the most suitable material for a particular application involves evaluating several factors. This includes balancing cost with both aesthetic and functional requirements. It is essential to match the desired properties for the application with the material options offered by the chosen manufacturing process.
Plastic extrusion can produce various types of plastic trim with precise tolerances by simply altering the die through which the plastic melt is processed. The construction sector frequently employs plastic trim, while appliance manufacturers use vinyl and flexible PVC trim for sealing stove and refrigerator doors. In the automotive industry, profiled trim is utilized for both exterior and interior fenders. As previously mentioned, types of plastic trim include edge trim, J trim, decorative trim, brush guard trim, fender flare trim, drip trim, and lip rail trim.
Plastic J trim, sometimes referred to as siding channels, features unevenly molded extrusions where one end is slightly shorter than the other, creating a "J" shape in the side profile. This trim is available in a variety of abrasion-resistant materials, including PVC, metal, vinyl, and more.
Plastic J trim products are ideal for managing cables and wires as they provide a neat and finished edge. Similar to U trim, this design is also suitable for decorative frames and can be effectively used as cap molding secured with clear tape or white foam adhesive. Additionally, plastic J trim is commonly employed in retail merchandising, directories, and signage, accommodating materials like acrylic, poster board, and others.
Edge trim is designed to cover rough and sharp edges on machines and equipment, enhancing safety and ease of handling. It protects both the underlying material and any attached components, such as cables, while also adding a touch of aesthetic appeal. Made from a range of flexible plastics and polymers, edge trim often includes a metal core to enhance its ability to securely grip and clamp onto edges.
Edge trim is used to cover edges on materials such as metal sheets, wood, and ceramics. Common applications include vehicle seats, tables, windows, ceilings, PC cabinets, shelving, machine guards, and various types of furniture.
Decorative trim, often used as the finishing touch in a room’s architecture, enhances the transition between the ceiling and walls. Crown molding, also known as cornice molding, often features intricate designs, though there are many variations available. Other forms of decorative trim include chair rails, casings, picture frame molding, dentil molding, and egg-and-dart patterns.
Trim seal covers the space between two coupling surfaces to offer insulation and impermeable sealing for freezers, refrigerator doors, vehicle tailgates and compartments, passenger doors, big and insulated vessels, and other appliances. Hence, a trim seal works as a gasket.
A trim seal may feature co-extruded polymer layers coated with vinyl and rubber to guard against noise, rattling, and corrosion. Often, a metal core is included to enhance the seal's grip on the edges. When selecting trim seals, important factors to consider include service temperatures, environmental conditions (such as moisture and vibration exposure), grip strength, and size.
A fender flare trim extends the fender to offer additional coverage for large or offset wheels and tires. This extension helps ensure that SUVs or trucks comply with Vehicle Equipment Regulations, reducing the risk of fines for violations.
Often, a single thermoplastic may not meet the performance requirements for a given application. Co-extruded plastic edge trim combines the properties of two different thermoplastics into one component, leveraging the advantages of both materials to enhance overall performance.
Co-extrusions can integrate a variety of materials, including combinations of flexible and rigid substances, different colors, thin cap stocks over thicker substrates, and many other configurations.
Lip trim is commonly utilized as a decorative feature in cupboard construction but is versatile enough to serve various other purposes.
This chapter will explore the various applications and advantages of plastic trim.
Plastic trim offers a wide range of applications due to its versatility. It is particularly beneficial for any product that requires a clean, safe, and polished finish.
Plastic trim helps reduce damage and distortion while providing flexibility, making it ideal for architectural uses such as wall and ceiling trim. It is also suitable for baseboard molding and doorway edging.
Additionally, plastic trim enhances durability by protecting industrial machinery from damage, safeguarding against sharp edges, and serving as flexible bumpers. This durability makes plastic trim a valuable choice for automotive applications, where it shields both vehicles and their occupants from harm.
Additional applications of plastic trim are outlined below:
Plastic trim products offer an efficient and cost-effective way to finalize a product.
Plastic trim products offer a cost-effective and efficient solution for finishing the edges of various components. While they are widely used in the automotive and transportation industries, they are also valuable across many other applications.
Plastic trim molding enhances the visual appeal of machinery components. When well-maintained, molding and trim can distinguish a finished product from a work in progress. Additionally, plastic trim is a budget-friendly option for fabricators aiming to improve the aesthetics of their designs without overspending.
Plastic trim profiles are constructed from durable materials to ensure reliability. They are designed for easy installation, requiring no specialized skills or tools. With a focus on quick setup and secure attachment, plastic trim molding is available in a variety of materials, profiles, colors, foamed profiles, finishes, and shapes.
Historically, fabricators relied on wood and wood products to create trim, with terms like casings and trim referring to the linear lumber elements used to finish the edges and corners of homes. However, wood trim faced challenges in damp environments due to its organic nature, which led to rot. This issue prompted the construction industry to seek a material that would be entirely resistant to rotting and water damage, leading to the development of cellular PVC.
Plastic trim molding, particularly for PVC pipes, was once limited to plumbing applications. Today, however, PVC has gained widespread popularity for various uses.
The primary differences between PVC and wood trim are chemical in nature. Wood tends to swell when exposed to moisture, while PVC expands with heat.
PVC trim responds to temperature changes by shrinking in the winter and expanding in the summer. Unlike wood trim, PVC trim does not warp due to environmental factors, making it a superior choice.
Edge trim, internal ornamental trim, fender flare trim, U trim, drip rail trim, J trim, and lip trim are popular varieties of plastic trim available on the market. Plastic trim is widely used in the construction industry for various purposes, including bumpers and guards for sharp edges and corners, interior and outdoor siding, door frame insulation, and window insulation and trim. While the automotive industry uses custom trim for the outside and interior fenders, appliance makers employ elastic vinyl and PVC trim for microwave oven doors and refrigerator sealants. Additionally, plastic trim is used in the maritime, recreational, and furniture industries for many purposes.
For manufacturers, plastic edge trim solutions offer an affordable, effective alternative to finish the edges of many components. Although they are used most frequently in the industrial automotive and transportation sectors, they are useful in a variety of other applications as well. Plastic trim profiles are created from sturdy materials to ensure dependability. Additionally, they are highly safe and easy to install; in most cases, they don't require special knowledge or equipment. Fast installation and secure holding are priorities in the design of plastic trimmings.
Regarding various manufacturing methods utilizing plastics, extrusion is among the highest in demand. To start the plastic extrusion procedure, thermoplastic flakes or pellets are put into a hopper placed on top of a closed extruding channel. Gravity puts the raw plastic material into the extruding channel. Running down the channel length is a screw conveyor that moves the raw plastic straight towards the other end, heating and shearing the plastic using friction. Electric heaters inside the extruding channel frequently aid the screw conveyor in plasticizing, or melting, the plastic flakes so that the plastic melts before it comes out of the end of the channel. Manufacturers from several industries rely on advanced extrusion machines. With the proper plastic extrusion machinery, there is no better way to manufacture superior quality plastic trim products. As with all machines, an extrusion machine has benefits and drawbacks, but plastic extrusion is a versatile production process.
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