Thermoforming is a popular manufacturing process widely embraced for its speed and efficiency in the shaping of large components made from thermoplastic sheets. Vacuum forming is one of the most common methods of thermoforming. This method involves heating a secured sheet of thermoplastic to its softening temperature, where it becomes pliable and can be shaped over a mold. The mold contains strategically placed cavities through which air will be suctioned out, creating a vacuum, forcing the pliable sheet to fill in and take on the shape of the mold. The versatility of this thermoforming process extends across diverse industries, including automotive, aerospace, and healthcare.

In this article, we will explore various large part thermoforming techniques and key factors influencing the success of this manufacturing method.

Large Part Thermoforming Techniques and Processes

Mold Design and Fabrication

In thermoforming and vacuum forming, tooling includes the mold onto which the thermoplastic will be formed. The mold incorporates vents through which air is removed. Some molds may also integrate a cooling system, typically using water, to speed up the curing process. Depending on the product’s design requirements, positive (male mold) or negative (female mold) may be used. Design considerations include overall part length and width, draw depth, sheet thickness, and other complexities (angles, corners, undercuts, texture, etc.). In house tooling and mold fabrication reduces overall production time. At Lerner Molded Plastics, we can accommodate parts up to 15’ in length with a draw depth up to 3’.

Sheet Heating

In the sheet heating phase, plastic sheets — typically composed of materials like polycarbonate or acrylic — undergo a carefully controlled heating process. This can be achieved through utilizing infrared heaters or ovens, ensuring that the plastic reaches the best temperature for pliability.The core of the sheet must reach forming temperature. While some variation is tolerable, the temperature of the sheet must be as uniform as possible. Proper sheet heating is vital because it determines the material’s ability to distribute uniformly across the mold.

Pressure Forming

Pressure forming has a similar process to vacuum forming, except positive pressure is used instead of vacuum pressure. The pressurized air forces the heated thermoplastic over the mold (template) and trapped air escapes through air vents on the other side. The higher pressures allow for greater levels of detail and texture as well as the ability to form thicker gauge sheets of thermoplastic. This technique is often used in fields requiring aesthetics and precision, such as medical equipment and electronic enclosures.

Twin-Sheet Forming

Twin-sheet forming involves heating and forming two plastic sheets, which are then joined together through a fusion process. This results in the creation of a hollow part with enhanced structural strength. The process offers design flexibility by allowing the creation of large parts with hollow structures, which can reduce weight without compromising strength.

Trimming and Finishing

After the thermoforming process, excess material is trimmed away to achieve the part’s final shape. Finishing processes — such as CNC machining, polishing, or other surface treatments — are also applied to meet tight tolerances and ensure the functionality of the parts. These techniques contribute to the quality and market readiness of the thermoformed components.

Key Considerations in Large Part Thermoforming

Here are the most essential elements to look into when considering thermoforming:

  • Material selection: The choice of plastic material significantly impacts the properties of the final thermoformed part. Heat resistance, impact strength, and flexibility must align with the intended application.
  • Mold design complexity: The intricacy of the mold design affects the final product’s quality and dimensional accuracy. Complex molds may require advanced engineering but can result in large, detailed parts.
  • Heating uniformity: Consistent heating across the plastic sheet is crucial for uniform material distribution. This ensures that the entire component maintains a consistent thickness and even application over the template
  • Cycle time optimization: Efficient temperature control, proper sheet heating, and cooling methods contribute to reducing cycle times. This is essential for enhancing productivity and meeting production demands.
  • Cost considerations: Thermoforming is often chosen for its cost-effectiveness. Assessing the overall costs, including material, tooling, and production, is essential for budgetary planning.
  • Tooling material: The choice of materials for molds and tooling impacts durability and precision. Common alternatives include aluminum, composite materials, and steel, each with advantages based on the application.

Partner With Lerner Molded Plastics for High-Quality Thermoforming Services

At Lerner Molded Plastics, we offer unparalleled expertise in delivering top-tier custom molding and thermoforming services across the United States! Our commitment to excellence is evident in every aspect of our operations, producing high-quality components that consistently meet standards. Whether you require a prototype to test your design concepts or need a full-scale production run, we have you covered.

Contact us today to learn more about our capabilities, or request a quote now.

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