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Thermoforming vs Injection Molding: What are the differences?

Plastics are used in all types of industries, providing versatility and strength in applications ranging from automotive body parts to human body parts. Each application requires a unique manufacturing process that molds parts to specifications.

Thermoforming and injection molding are two of the most popular manufacturing processes for making plastic parts, and they offer unique advantages depending on the specific application. Although thermoforming is typically used for large-scale designs and shorter production runs, injection molding is often a better choice for small, complex parts and larger production runs.

What is Thermoforming?

Thermoforming is the process of forming a heated plastic sheet on the surface of a male or female die. Unlike injection molding, this is a single-sided plastic manufacturing process. Only one side of the plastic sheet is controlled by the mold or tool. Vacuum forming and pressure forming are both popular forms of thermoforming.

Depending on the needs of the project, thermoforming can offer several distinct advantages, including:

  • Lower tooling costs compared to injection molding
  • Rapid product development and prototyping
  • Bright color and texture options
  • Extremely adaptable and easy to adjust
  • Thermoforming is ideal for small batches (250 to 3000 parts per year).

Reduce tooling costs

Tooling for thermoforming is less expensive than injection molding. Molds for thermoforming are usually made of inexpensive aluminum. In contrast, injection molds are typically composed of thicker aluminum, steel, or other heavier alloys to withstand higher pressures and enable continuous reuse across larger production runs. Also, thermoforming uses only one-sided tools instead of double-sided injection molds. This effectively cuts the material required for mold making in half, significantly reducing the upfront cost of thermoforming. However, molds are less durable and cannot be used for large-scale or repetitive production.

Part size plays an important role in the cost-effectiveness of thermoforming compared to injection molding. The larger the component, the greater the gap between tooling costs. Thermoforming becomes increasingly cost-effective as part sizes increase.

Rapid Product Development and Prototyping

Because thermoforming molds can be produced quickly, thermoforming is much faster than injection molding in terms of product development and prototype testing. Injection molds are more time-consuming to machine because the mold is double-sided and consists of a harder material such as steel. In contrast, thermoforming tooling is easier to design, manufacture and modify, making it ideal for development and testing.

Multiple Texture and Vibrant Color Options

Thermoforming offers several benefits for product design and branding. Vibrant colors can be incorporated into thermoformed plastics for vivid, long-lasting coloration throughout the material. Additionally, thermoformable materials can accept painting, screen printing, printing, embellishment, and coating to provide unique designs, textures, and finishes that enhance product appearance and longevity.

Extremely adaptable and easy to adjust

Because thermoforming uses simple, one-sided molds made of highly formable materials, thermoformed designs can be modified quickly and at minimal cost. Injection molding, on the other hand, requires dual molds with heavier materials, which is more time-consuming and expensive for tooling.

Applications using thermoformed products

  • The lower cost, versatility, and adaptability of thermoforming make it ideal for many applications, including:
  • Automotive: Instrument panels, seat components, interior panels, bumpers and air ducts
  • Aerospace: Air ducts, seating components, interior panels, kitchen equipment and curtains
  • Structure: equipment housing, toolbox, interior and exterior panels
  • Medical: diagnostic and imaging equipment enclosures, bed and furniture components, assistive equipment, and walls and ceilings
  • Public transportation: interior and exterior trim, seat components, instrument panels and lamps
  • Office equipment: Faxes, printers, computer and copier enclosures, electrical panels, walls and ceilings, and furniture

What is Injection Molding?

Injection molding requires extensive upfront design and engineering to develop a detailed tool or mold. A split mold made of stainless steel or aluminum is injected with molten liquid polymer at high temperature and extremely high pressure. The mold is then cooled to release the complete plastic part.

Plastic injection molding has several unique advantages of its own, including:

  • Detailed, highly engineered molds with multi-cavity mold options
  • Precise and efficient handling of large numbers of small parts
  • Effectively reduce the number of pieces
  • Efficient use of materials, low scrap rate

For projects requiring thousands or even millions of identical parts, plastic injection molding is ideal for high-volume orders and mass production.

Detailed tools for complex parts

One of the main advantages of injection molding is the ability to manufacture extremely complex components with exceptional detail. The high pressures used in the injection molding process allow the production of complex parts and unusual geometries as the material is firmly pressed into the tiniest of tiny cavities. Multi-cavity mold options allow further customization of the injection molding process to meet specific needs.

Extremely high precision and efficiency

Injection molding involves repeated runs using durable and reusable molds. Users can rely on molds to deliver highly accurate, repeatable results for years of mass production. The method is particularly useful for very small, complex and complex components that are time-consuming or difficult to create using thermoforming, cutting, milling and other manufacturing methods.

Reduce injection molding costs

Although injection molding is more expensive than thermoforming, the mold design and manufacturing process can be modified in various ways to reduce overall production costs. Simplifying and simplifying the design can reduce some of the costs involved in creating detailed molds. Alternatively, employing material reduction methods such as undercutting and coring, or simply modifying molds from similar products, may provide the means to meet new project needs in an affordable manner.

Efficient material use

Injection molding is an efficient process with very low scrap rates. The amount of material for each component is precisely measured to ensure the mold is completely filled with little to no flash or waste. Injection molded products can be molded to scale and require little additional tooling after being ejected from the mold.

Application of injection molding products

  • Construction: Hand tools, fasteners, door and window locks, carpentry and handles, and other construction accessories
  • Aerospace: Turbine blades and casings, lenses, panels and gears
  • Food and Beverage: Food-grade plastics for conveyors, filters, and processing systems; and food and beverage packaging
  • Medical and Pharmaceutical: Medical Device Components, Diagnostic Kits, X-Ray Components and Surgery Prep Kits
  • Shopping malls: retail display equipment such as dividers, hooks and product stops.

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