In today’s competitive manufacturing landscape, businesses looking for short-run plastic part production often face a critical decision: Should you choose low volume injection molding or thermoforming plastic? Both methods offer unique advantages, but selecting the right one depends on your part design, material needs, budget, and future scalability.
At UGP Plastics, with over 70 years of experience in custom plastic manufacturing, we understand the complexities of these decisions. This guide will help you understand which method is best suited for your next low volume plastic manufacturing project.
What Is Thermoforming Plastic and How Does It Work?
The thermoforming process involves heating plastic sheets until they become pliable before using vacuum pressure or mechanical force to shape them over molds. The formed plastic maintains the mold shape after cooling before receiving its final trim to become the finished product.
The method works best for creating bigger basic shapes which find applications in packaging and displays as well as automotive interior panels and trays. The process operates at a fast pace and remains cost-effective because thermoforming molds work faster and cost less to produce than metal injection molds.
What Is Low Volume Injection Molding?
Low volume plastic injection molding involves injecting molten plastic into precision-engineered molds to produce highly detailed and durable parts. This method is best suited for production volumes ranging from a few hundred to several thousand units and is ideal for prototyping, product testing, or pilot runs before transitioning to full-scale manufacturing.
Unlike thermoforming, injection molding supports tight tolerances, high repeatability, and the ability to use a wide variety of plastic resins with complex geometries.
Key Differences between Low Volume Injection Molding and Thermoforming
While both methods serve short-run needs, they differ significantly in application and performance. Here’s a breakdown of their core differences:
1. Tooling Costs
• Thermoforming molds are less expensive and faster to produce.
• Injection molding requires higher upfront investment in steel or aluminum molds.
2. Part Design Complexity
• Injection molding allows for intricate, tight-tolerance parts.
• Thermoforming is more suited to simple, large-area designs with limited detailing.
3. Material Variety
• Injection molding supports a wide array of engineered resins.
• Thermoforming is limited to sheet-based thermoformable plastics.
4. Lead Time
• Thermoforming typically offers a quicker turnaround (1–2 weeks).
• Injection molding takes 2–4 weeks, depending on mold complexity.
5. Finish and Strength
• Injection molded parts deliver better surface finishes and structural strength.
• Thermoformed parts may require post-processing for sharp finishes.
When Should You Choose Small Run Injection Molding?
You should choose small run injection molding when your project requires:
• High precision and consistent quality: Injection molding delivers exact replication of intricate designs, ensuring each part meets tight tolerances and engineering specifications—ideal for medical, aerospace, and electronics components.
• Complex shapes and detailed textures: With the ability to produce undercuts, sharp corners, and finely textured surfaces, injection molding supports even the most intricate geometries without sacrificing quality.
• Strength and durability for functional parts: The process allows for the use of strong, engineering-grade resins, making it suitable for end-use products that require high structural integrity and thermal resistance.
• Repeatability for multiple design iterations: If you’re prototyping or testing variations of a product, small run injection molding ensures that every version maintains consistent dimensions and performance.
• Scalable solutions for future high-volume production: Once your part design is finalized, the same mold can be used for scaling up production, reducing costs and speeding up time to market.
When Is Thermoforming Plastic the Better Choice?
Thermoforming plastic is best when your production requires:
• Cost-effective tooling for low-volume needs: Thermoforming molds are significantly cheaper and faster to produce than injection molds, making them ideal for initial product trials or budget-conscious projects.
• Fast prototyping and turnaround: With shorter lead times and simpler mold requirements, thermoforming is a smart option when you need to get your product to market quickly or test form and fit in real-world conditions.
• Large or shallow parts with basic shapes: Thermoforming excels in producing wide, thin-walled components such as trays, clamshells, enclosures, and display covers with minimal tooling complexity.
• Low mechanical strength and simple applications: For parts that do not require high tensile strength—such as packaging or disposable containers—thermoforming offers a practical and lightweight solution.
• Lightweight packaging or temporary-use items: This process is commonly used in the food, retail, and medical sectors where disposability, light weight, and cost-efficiency are critical.
Injection molding can produce extremely small, precise parts — even down to a few millimeters. This capability is especially important in medical devices, microelectronics, and compact component designs, where dimensional accuracy and repeatability are crucial.
Understanding the Types of Injection Molding Processes
There are two widely used injection molding processes, each suited to different material needs and end-use environments:
• Thermoplastic Injection Molding: This process uses thermoplastic resins—plastics that can be reheated and remolded multiple times without significant degradation. It is ideal for high-volume production, rapid prototyping, and industries where flexibility, recyclability, and lightweight properties are essential. Materials include ABS, polycarbonate, nylon, polypropylene, and more.
• Thermoset Injection Molding: Unlike thermoplastics, thermoset materials undergo a chemical reaction during molding that permanently sets their shape. These product materials cannot be remelted, making them extremely heat-resistant and structurally rigid. Thermoset injection molding is often used in electrical, automotive, and industrial applications that demand long-term durability and performance in harsh conditions.
Understanding the differences allows manufacturers to choose the right process based on strength requirements, temperature exposure, and application longevity.
What Is a Thermoforming Polymer?
A thermoforming polymer is a plastic material that becomes soft and pliable when heated, allowing it to be molded over a form or mold. Once cooled, it retains the new shape, making it ideal for creating lightweight and cost-efficient components.
Common thermoforming polymers include PET (Polyethylene Terephthalate), PVC (Polyvinyl Chloride), HIPS (High Impact Polystyrene), ABS (Acrylonitrile Butadiene Styrene), and PP (Polypropylene). Each offers unique advantages in clarity, durability, chemical resistance, and formability—allowing manufacturers to match the right polymer with the demands of the end-use environment.
The versatility of thermoforming polymers enables their use in food packaging as well as point-of-sale displays and clamshell containers and medical trays and automotive interior panels because they produce large functional lightweight parts at reduced tooling expenses.
Whether you’re launching a new product or testing a concept, choosing between thermoforming plastic and low volume plastic injection molding can significantly impact your success. At UGP Plastics, we’ve spent over seven decades helping companies across Canada and North America make the right choices for their plastic part production.
If you’re unsure which process fits your needs — whether it’s thermoforming molds for rapid prototyping or small run injection molding for scalable production — we’re here to help.
Contact UGP Plastics today for expert consultation and high-quality custom plastic manufacturing solutions.
Frequently Asked Questions (FAQ):
What is a thermoforming polymer?
The thermoforming polymer exists as a plastic material which turns pliable when heated. The material maintains its formed shape after it cools down from the heating process. The most common thermoforming polymers consist of ABS, PET, PVC and polystyrene.
What is low volume injection molding?
The production method of low volume injection molding creates plastic parts through custom molds when making small quantities. An error occurred while processing your request. Please try again.
What are the two common types of injection molding processes?
The two most common types are thermoplastic injection molding and thermoset injection molding. Thermoplastic molding uses resins that can be melted and reused, making it ideal for flexible, recyclable applications. Thermoset molding involves materials that cure permanently during molding, offering superior heat resistance and structural strength for demanding applications.
How small can injection molding be?
Injection molding can produce parts as small as a few millimeters in size. Precision micro-molding techniques can handle components with extremely tight tolerances, making it suitable for medical, electronics, and miniature product applications.
