Learn about the main differences between thermoforming and injection molding manufacturing method. View prices, software, benefits, and decide on the ideal comparison methodology of your production in 2025.
Introduction to Plastic Manufacturing Processes
The plastic manufacturing industry can present you with a variety of different ways and avenues in which to pursue, taking raw materials and turning in into finished products, including various plastic components, with thermoforming and injection molding being among the most noticeable ones. Knowledge of the core variability in the nature of such processes is imperative to manufacturers, engineers and businesses that want to streamline their output processes. Although both the thermoforming and injection molding have a similar use in large scale designs whereas injection molding is better to use in small-small, detailed parts and larger production runs. In thermoforming, parts are made of a heated sheet of plastic whereas in injection molding the plastic parts are shaped by melting plastic pellets and shooting them into a mould.
The two processes have however changed largely with the decades as more technologies and materials are involved in order to keep up with the needs of multiple industries. Whether about automotive parts, medical equipment, food packaging, or consumer electronics, the decision between injection molding and thermoforming may influence the production costs, manufacturing lead time, and product quality to a significant extent.
Understanding Thermoforming: Process and Applications
Thermoforming- it is a procedure of shaping a heated plastic sheet to the flat surface of a male or female model. The process of manufacturing is initiated by a flat sheet of thermoplastic material, which should be heated up to reach the plastic state of substance and get fragile and deformable. After the material has been heated to the maximum temperature, it is pressed (with vacuum pressure, mechanical pressure or compressed air) on or into a mold.
Thermoforming process provides incredible flexibility when it comes to producing large format parts and complicated shapes and will prove difficult or impossible to produce by other manufacturing types. Other industries using thermoforming include the automotive industry, aerospace industry, medical devices, and the packaging industry in the production of a wide variety of products going to aircraft interior panels to medical device housings and food packaging containers.
Thermoforming has the flexibility advantage of part size and not only. It does not have limitations to the types of materials, which include ABS, polystyrene, polycarbonate, PETG, and polyethylene terephthalate glycol or even special plastics used in medical devices and equipment, thus finding a wide range of uses that require different material characteristics.
Injection Molding: Precision Manufacturing at Scale
Injection moulding is a complex processing technique in which molten material made of plastics, is forced under high pressure into the highly machined pocket or cavity of a mould. This system is particularly effective in the production of small to medium sized components with high dimensional accuracy and repeatability rating it highly suitable in large volume applications.
Solid heats the injection molding process by melted pellets, or granules of plastics inside an increase barrel. Molten material is then pushed into the mold cavity using a gate system into an enclosed mold where the plastic cools and solidifies to the required final piece shape. This procedure facilitates complex geometries, fine details and close tolerances that are required in the manufacture of electronic devices, auto parts, medical equipment and consumer products.
The modern injection molding machines are fitted with sophisticated control systems which are set to keep real -time monitoring and regulation of parameters like temperatures, pressure and injection speed so that part quality is always same and there are minimal flaws. The technology has very broad capability to process thermoplastic, thermoset and engineering thermoplastics with specialist properties.
Cost Comparison: Initial Investment vs Long-term Economics
Compared to thermoforming, injection molding is usually costly. This is because the tooling of thermoforming cost and the parts used will be cheaper in the sense that it will not be subjected to such degree of pressure like injection molds. Cost comparison of these two processes takes into account various parameters that one will have to seriously consider according to some needs of the project.
Thermoforming could provide cost advantages in the terms of low initial costs and faster tooling turnaround time but in case of broader production ranges, injection molding can be beneficial due to economies of scale, and low cost per-unit produced. The tooling to perform thermoforming is much less expensive (usually by a factor of 5) than that to do injection molding since the molding is done at reduced pressures and simpler molds are needed along with a simpler molding machine and tooling materials such as aluminum and even composites may be used instead of costly tool steel.
But the economic equation turns completely different when there is an increase in the volume of production. Injection molding may be cheaper per-unit, when high-volume production runs amortise the high initial tooling cost in terms of millions of parts made. Continuity and accuracy of injection molding also minimize secondary production and inspection deepening the cash flow in the production of large quantities.
Production Volume Considerations
In thermoforming low to mid volumes are more economical whereas high volume is often more economical with injection molding. The break even with these two processes usually lies somewhere between 10,000 to 100,000 parts depending on complexity, size, and material required on the parts.
Thermoforming is quite successful in a situation in which the quantity of goods that will be produced will be between that of a prototype and a few thousand pieces/year. The economic cost of low tooling, rapid set up times makes it cost effective with short to medium runs, seasonal products or specialised where demand is expected to be variable.
The higher the volumes of production, the more injection molding is favored especially with very high volumes such as above 50,000 to 100,000 parts a year. Its ability to produce parts in a few seconds via the young pace that modern injection molding equipment has made it very effective in a large scale production.
Material Flexibility and Options
Thermoforming materials are highly flexible and pliant because injection molding involves the usage of plastic pellets whereas this process involves the usage of plastic sheets. In these two different processes of manufacture, the aspect of the selection process is very different and each of the processes has its own benefits based on the application requirements.
Thermoforming does not allow a free choice of materials because it uses ready-made plastic sheets, and the material is whatever is in sheet form on the market. This shortcoming is however countered by the fact that multi-layer sheets may be utilized, textured surface and also the use of pre-colored materials may be done, in the process completely dispensing with any secondary finishing procedures. Typical thermoformable plastics are ABS, polystyrene, polycarbonate, PETG, HDPE and many of the special grades available are for medical or food applications.
Injection molding has additional material freedom, in that injection works with plastic pellets or granulate, which can be accurately compounded (e.g. with additives, colorants, and reinforcements). This process is able to accept engineering plastics, high-temperature material, and glass filled composite, as well as exotic materials that are not available in sheet forms suitable to thermoform.
Design Flexibility and Complexity
The thermoforming and injection molding machines are widely different in design capabilities, and both processes have distinct advantages with regards to the kind of parts and geometries to which they apply. Thermoforming is better at large parts, relatively simple with consistent wall thicknesses and injection molding can accomplish the same that is able to manufacture small intricate pieces as well with complex geometries and different thicknesses of the walls.
Parts will be especially suited to thermoforming when large surface area is needed, in automobile interior paneling, aircraft, and packaging in general. Undercuts, draft angles and ribs can be easily provided in the process, but more complicated internal details or fine features may not be obtainable as a result of the constraints of the forming process.
The injection molding provides high design flexibility in more complex parts and complicated detailing, as well as, living hinges, threaded and multi-cavity parts. The elevated pressure in injection molding enables the manufacturing of thin-walled shape as well as sharp corners and complicated forms which could not be possible to make by thermoforming.
Lead Times and Production Speed
Comparing the lead time in thermoforming and injection molding, the difference in length is significant to affect the time constraints of a project and the plans to introduce a product to the market. Tooling Thermoforming can often have a quicker turn around in both tooling design and lead time in going to production as compared to injection molding and therefore has its use in time sensitive projects or in fast prototyping.
Commonly the process of thermoforming tooling can take 2-6 weeks reliant to the complexity of parts and type of mold material. These shorter lead times are caused by the fact that the tooling requirements are not very demanding and the precision that is required in machining work is also not that high. Thermoforming could be scaled up to production scale relatively quickly, once tooling is finished, making it suitable where there is seasonality of products or where a product is being tested in a market.
Tooling used in injection molding usually takes 6-16 weeks to complete, even with all of the high quality machining, as well as heat treatment, and testing of injection molds that can be performed. When it starts to produce however, injection molding can be very high in its production rate with the cycle time of small pieces often being measured in seconds.
Quality and Precision Requirements
The quality and precision potential of thermoforming and injection molding is also wide apart so the use of the process also has to rely on particular part demands and the criteria of the use. A typical advantage of injection molding over the vacuum forming method is greater dimensional control, better surface finish and repeatability.
The tolerances available with injection molding are +/-0.001 inches (+/-0.025mm) on critical dimensions and therefore suitable in areas that require high levels of precision like in the medical industry, automotives, and electronics, and require high precision in fit and operation. Also surface finishes that are achieved through high pressure and the controlled cooling in injection molding are outstanding resulting often in the avoidance of subsequent operations.
Tolerances thermoforming is generally capable of are + /0.010 to + / 0.030 inches ( + /0.25 to + /0.76mm) depending on material, and can suffice in many applications without secondary machining operations but where critical dimensions must be met, secondary physical machining may be necessary. The quality of the surface finish is a matter of the original injection sheet surface and mold finish, but tends not to approach the accuracy of injection molding.
Environmental Impact and Sustainability
Different with each use, sustainability aspects of the manufacturing processes are becoming more important in the selection of the processes to be used and both thermoforming and injection molds have special environmental strengths and weaknesses. There is a need to include material waste, energy consumption, recycling and end-of-life in the environmental impact assessment.
As a rule, thermoforming has greater material waste through scrap trims and through requirement that it uses pre-manufactured sheets. Nevertheless, recent versions of thermoforming most of the processes include a trim recycling method that utilizes a vacuum pump to recycle the leftover material through grinding as well as recycling the material hence creating significantly less wastage. Lower processing temperatures encountered in thermoforming, also means less energy intensity as compared to injection molding.
Wastes of material generated by injection molding are usually less, because the material used is the only amount required by each part, and the runner and gate material, which can be recycled. The increased processing temperatures and pressures consume more energy but per-part efficiency of high-volume production can compensate these effects.
What Are the Disadvantages of Thermoforming?
Though thermoforming is fairly flexible and inexpensive in a large number of projects, there are a number of limits to the process that need to be taken into account. The disadvantage of this is that the thickness of the part is hard to regulate and therefore the level of the vacuum pressure should be even all through the mold. The main drawbacks are low-detail resolution, thickness variation and wastage due to operations of trimming.
By the thermoforming process design, there is no consistent ability to produce fine details and sharp features by the characteristic nature of the flow of materials in forming. Deep drawn parts can have large variations in thickness with some sections longer than others. There is also the wastage of feeding excess material to formed parts and this material though reusable is also part of the lost efficiency as compared to injection molding.
Understanding the 10-10-5 Rule for Thermoforming
The 10 – 10-5 rule in thermoforming is used to define the design essentials which makes it easy to form parts successfully and build a quality part. According to this rule, the draft angles of 10 degrees, the inside corner radii which is at least 10 times the material thickness, and, the outside corner radii should have at least 5 times the material thickness.
The guidelines assist in avoiding stagnation of stress in material, enhance material flow in the forming and minimize chances of failure or quality defect of parts. Observation of the 10-10-5 rule is vital in realizing consistent results and high success level in thermoforming operations.
The Five Stages of Vacuum Forming
The oldest process of thermoforming is called vacuum forming and it is used to eliminate the air between a heated form of plastic material and a template with the help of a vacuum. Vacuum forming process is composed of five stages namely heating, positioning, forming, cooling and trimming.
The heating phase entails heating the plastic sheet to its forming temperature through using radiant heater or hot air. Positioning is done by the employer of the heated sheet and it is first applied on the mold and the edges are sealed acrylonitrile butadiene styrene. During the forming stage the material is drawn into the mold cavity by the use of the vacuum pressure, and then cured into a solid by cooling. Last of all, trimming eliminates any extra material to produce the final piece.
Three Types of Thermoforming Processes
There are three main variations of the thermoforming process including vacuum forming, pressure forming and twin-sheet forming. Vacuum forming can be described as a creation of parts driven by the difference in atmospheric pressures and hence it is ideal when dealing with simple shapes and soft materials. Pressure forming implies addition of compressed air in order to increase quality of detail definition and surface finish.
Twin-sheet forming also thermoforms two sheets and bonds them together instantly forming hollow components with multifaceted inner structure. The process is very applicable in automotive fuel tanks, air ducts and application in which a hollow structure that has more points where connections can be made.
Vacuum Casting: Advantages and Applications
The advantages of vacuum casting are low cost of tooling, high turnaround rates, and small production of high quality parts. The cheapest plastic production technology of low volumes is known to be vacuum forming. This is linked with the lost cost of prototyping and the making of the vacuum form mold.
It is well suited to prototyping, bridge-tooling and small production batches of parts that could not be cost-effectively made in injection moulds. Depending on the available tooling, the surface finish and mechanical properties of injection molded parts may be replicated by vacuum casting at much lower tooling costs and a fraction of the delivery time.
Cost Analysis: Vacuum Casting vs 3D Printing
Comparing the cost of vacuum casting to 3D printing will be entirely dependent on the size of the part, quantity of the part needed, the material needed and even the finishing of the part. In small volumes of large components, vacuum casting is usually less expensive than 3D printing, via material cost and manufacturing rate factors create parts plug assist.
Nonetheless, it has a lot of benefits in complex shapes, small components and extremely low production numbers, in these cases tooling makes no sense. The breakeven level is usually at 20-100 parts or above due to complexities of parts and size requisites lightweight packaging.
Vacuum Molding Process Explained
Vacuum molding activities start by affixing a piece of thermoplastic on top of a molding depression mold’s shape. The sheet is brought to a desirable warm state after which vacuum is placed under the mold hence the atmospheric pressure reason pushing the material into the mold cavity vacuum thermoforming. The section is then taken out of the mold by cooling multiple materials lower cost alternative.
This process is suitable with different molds materials such as aluminum, steel, wood or even 3d printed molds used in prototyping single sided mold design. Vacuum molding process is easy to do both industrially and in learning institutions desired shape.
Vacuum Forming Mold Costs and Materials
The primary merit of the vacuum forming procedure over numerous other giant moulding procedures is its lesser tooling charges. Since the tooling contains few, or no moving parts, tools may be machined or cast in one piece manufacturing capabilities. The cost of mold depends on the type of material required, size, or even the complexity required during Vacuum forming construction equipment.
Wood molding or 3D printed types of molds cost less than a five-hundred dollar investment and the same cost of the production can run between 2-thousand to 10-thousand dollars softened sheet. High-volume high pressure steel injection molds can cost between 10,000-$50,000, however are still considerably cheaper than similar injection molds epoxy molds.
Food-Safe Materials for Vacuum Forming
Vacuum food forming involves high attention to materials and manufacturing control so that the food is safe to eat and meet the FDA standards and food contact regulations plastic thermoforming. Food safe examples are PETG, polystyrene, polypropylene and special food-grade recipes of ABS and other thermoplastics structural foam.
The vacuum forming process has to ensure that the high level of temperature control and cleanliness is used so as to avoid contamination. Frequent testing and certification maintain lasting conformity with rules of food safety in the course of production same materials.
Injection Molding vs Vacuum Molding: Key Differences
The most crucial distinctions between injection and vacuum molding consist of pressure demands, intricacy of the toolings and applicability of precision other processes. The injection molding technique involves a lot of pressure (1,000-30,000 psi) to fill complex mold cavities whereas the vacuum process uses atmospheric pressure difference (max. 14.7 psi) vacuum formed products affordable tooling.
Such pressure difference has a direct effect on the kind of parts that each process can efficiently manufacture, where injection molding is better at smaller and finer parts, whereas vacuum molding capable of producing bigger and comparatively basic forms female molds. These differences can be observed in terms of tooling complexity and costs as the injection molds are range to need precise machining and vacuum molds are commonly constructed using simpler techniques mold making.
Injection Molding Machine Hourly Rates
Depending on the machine size, complexity, and geographical location, prices of injection molding machine are charged on hourly basis. The cost of the small machines (less than 100 tons) ranges between $25 and $50 per hour; whereas large (bigger than 500 tons) machines cost between 75 to 150 dollars per hour. The rates do not cover the cost of material, tooling and second operations and cover machine operation polyvinyl chloride.
Other factors that influence the hourly rates are the level of automation, the level of precision and the volume of production. Precision medical/aerospace customers can have to pay premium prices as it relates to quality control documentations.
Thermoplastic vs Injection Molding: Material Considerations
Interdependency of thermoplastics and injection molding is central to the behavior of materials when they are processed in a plastics mold. Thermoplastics can be repeatedly softened and re-solidified which makes them ideal candidates to be injection molded since quality in part can be ensured by precise temperatures thermoplastic sheet.
The various thermoplastics need particular manufacturing circumstances such as sanctioning temperature, injection speed, and cooling time. PEEK, PPS, PEI and other engineering plastics have very unique processing equipment and processing knowledge whereas commodity plastics such as polyethylene and polystyrene are less sensitive to processing requirements vacuum formed components.
Best Practices for Vacuum Forming Over Plastic
Consideration of the thermal expansion of vacuum forming over the existing plastic parts or inserts, material combination as well as bonding needs are some considerations that should be given when vacuum forming over existing plastic parts or inserts. The forming-temperature should not cause degradation or dimensional changes to the substance material which may compromise part quality.
Multi-material vacuum forming may often necessitate the use of special adhesives (or mechanical rather than adhesive attachment methods) to effect a correct bond between materials. The process parameters should be adjusted to meet the thermal characteristics of every material used.
Conclusion
Whether to choose thermoforming or injection molding process comes down to pairing the process capabilities with the project needs. The solution varies on the volume and part design of the project vacuum forming machine. The advantage is that injection molding is more optimal when it comes to high volume production of parts that are relatively small and thermo forming is more optimal when it comes to the lesser volume and larger part. When all these factors like the volume of the production, the complexity of the parts, the type of materials to be used, and the cost limits are carefully considered manufacturers will be in a position to choose the best amongst the wide range of processes available and succeed in this dynamic market place.
About GWT Worldwide
Guanwutong (originally named Shenzhen Guanwutong International Freight Forwarding Co., Ltd.), also known as GWT Worldwide, is a professional highway express, international freight forwarding, global supply chain solutions, and cross-border e-commerce international logistics service providers. Well versed in air freight, sea freight, China-Europe railway transportation and customs clearances vacuum forming material, GWT Worldwide takes care of manufacturers to transport thermoformed and injection mold products smoothly to any part of the world. We provide end-to-end logistics where we provide Amazon FBA shipping and warehousing services so your productions can be shipped safely and at a cheap rate to the international markets.
