When manufacturing plastic parts, thermoforming is often compared with injection molding, milling, 3D printing, and foam solutions. The decisive factors are speed, cost, design freedom, material requirements, and process reliability. This article highlights the key differences between these processes.
Talida Eichhorn
Updated on June 15, 2026
In plastics engineering, different plastic processes are used depending on the component geometry and quantity.
| Process | Category | Typical applications |
|---|---|---|
| Thermoforming | Forming | Housings, covers, trays, packaging |
| Injection molding | Casting | Mass-produced products, precision components |
| CNC milling | Machining | Precision components, prototypes |
| 3D printing | Additive | Prototypes, small series, complex geometries |
| Foam solutions | Foaming | Upholstery, simple packaging |
In plastics engineering, these processes are primarily differentiated according to the molding method, quantity, precision, and material properties.
Here is a brief overview of how they work:
In thermoforming, a plastic sheet is heated and then drawn into a mold. The process is suitable for containers, housings, packaging, and inlays.
In injection molding, plastic is first melted and then injected under pressure into a closed mold. There, the material solidifies through controlled cooling before the mold is opened and the component is removed.
In CNC milling, a component is carved out of a plastic block by a computer-controlled milling head that precisely removes material along predetermined paths.
In 3D printing, also known as additive manufacturing, a component is built up layer by layer from plastic.
Foam can be produced both chemically and physically. In chemical foaming, typical components such as polyol and isocyanate react with each other, producing CO₂ among other things. This gas causes the mass to foam. In physical foaming, a blowing agent is added which expands or evaporates when heated, thus forming the pore structure.
After foaming, the foam block hardens and can then be cut, punched, or CNC-machined. The foam parts produced in this way are particularly suitable for simple packaging, upholstery elements, or standard solutions.
The processes are compared in five categories that are often decisive when it comes to the production of plastic parts:
Fast development and production start-ups enable you to respond to market requirements. Especially in dynamic markets, a short time-to-market can be crucial for securing competitive advantages or meeting project deadlines.
In the best case scenario, a thermoforming project can be delivered in less than 6 weeks. This includes 1-2 weeks for creating the design based on the requirements and data in consultation with the company. Once the design data has been approved, production of the aluminum series tool begins. Depending on the urgency, this can be done in 3 weeks.
As soon as the tool is ready, it is taken to the thermoforming manufacturer and the first samples are drawn from the series tool and material. Once the series samples have been approved, series production begins. Depending on the quantities and provided that the manufacturer has sufficient capacity, (partial) delivery can take place after just two weeks.
In injection molding, the long tooling times of usually six to twelve weeks lead to a significantly delayed start of series production.
Milling and 3D printing are becoming increasingly complex in series production, which means that production times are longer overall. 3D printing is very fast for smaller quantities or prototypes, as no tools are required. This means there are no lead times. Once the CAD data is available, parts can be manufactured within a few days.
For large series, 3D printing or milling is limited due to slower production speeds, poor scalability, and higher material costs.
Foam and standard solutions are ready for immediate use, but often do not offer the precision required for technically demanding applications.
In moderate quantities, fixed costs have a direct impact on profitability, as they significantly increase the unit price. Processes with low fixed costs enable more efficient unit costs and reduce the risk of an uneconomical series.
A key cost driver in a thermoforming project is the tooling costs, which represent a one-time investment in the four to five-digit range. These costs are amortized as the number of units increases. Since economies of scale do not apply to the same extent to material costs, the proportion of material costs per thermoformed part increases with increasing quantity and thus becomes the largest cost center.
Compared to other plastic manufacturing processes, thermoforming occupies the “sweet spot” between several hundred and 10,000 parts, as the initial tooling costs are significantly lower than for injection molding and the unit prices are significantly lower than for 3D printing.
Injection molding requires a costly initial investment in the tool, but is more cost-effective in terms of total costs due to low unit prices for quantities of around 10,000 or more. This means that the manufacturing process only pays off for very large series.
3D printing has no initial tooling costs, but due to consistent production times, there is little scope for economies of scale in terms of quantity. Milling also incurs high unit costs, which quickly makes the process uneconomical for small and medium-sized series.
Foam solutions and standard solutions are cost-effective, but in many cases do not offer sufficient technical durability.
A manufacturing process that can respond flexibly to product changes, especially in the development phase, and does not make adjustments expensive or time-consuming reduces development risks. This allows updates and optimizations to be implemented without high additional costs.
Deep drawing offers a high degree of flexibility and allows for adjustments, even for special requirements such as ESD or STANAG compliance.
Injection molding allows for design freedom, but changes to the tool often result in considerable effort and high adjustment costs.
Milling and 3D printing allow for changes. However, milling has geometric limitations, which reduces the scope for design. 3D printing allows for a great deal of creative freedom.
Foam and standard components offer little scope for customization and are limited to standard shapes.
Thermoformed parts such as housings or panels must be resilient in real-world use. An unsuitable process will result in components that deform, break, or are unsafe, which can lead to high follow-up costs in assembly and service.
Thanks to adjustable wall thicknesses and the materials used, thermoforming offers high rigidity and excellent mechanical strength.
Injection-molded parts also achieve high strength and are mechanically equivalent to thermoformed parts in terms of robustness.
3D-printed components have significant limitations in terms of mechanical load capacity.
Foam solutions also have low mechanical load capacity and are therefore usually unsuitable for functional technical applications.
Materials determine both functionality and durability. Requirements such as ESD protection, UV resistance, temperature behavior, or chemical resistance are often crucial to a project. Processes with a limited selection of materials can severely restrict the area of application.
Thermoforming allows for a wide range of materials, including specialized variants such as ESD-compatible or flame-retardant materials, covering many technical requirements.
Injection molding offers a certain variety of materials, but is limited by process-specific requirements in the selection and combination of plastics.
The choice of materials for milling and 3D printing is highly dependent on the respective machine, meaning that not all engineering plastics can be used.
Foams are difficult to specify and therefore only meet simple material requirements.
| Advantages | Plastic thermoforming | Injection molding | Milling / 3D printing | Foam / Standard solutions |
|---|---|---|---|---|
| Time-to-Market | quickly achievable, depending on geometry & tooling | long tooling times (6–12 weeks) | quick for samples, but time-consuming for series production | immediately available, but lower precision |
| Costs for small/medium series | very efficient, low tooling costs | high fixed costs, only worthwhile for large series | high unit costs | inexpensive, but short service life |
| Design freedom & adaptability | high flexibility (also for ESD, STANAG, etc.) | high adaptation costs | geometrically limited (milling) / very free (3D printing) | hardly customizable |
| Mechanical robustness | high rigidity due to wall thickness adjustment | high strength due to compacted plastic melt | limited with 3D printing; CNC robust | low stability |
| Material selection (e.g., ESD, PC, STANAG) | wide selection, including specialized materials | limited by process-related requirements | depends on machine & process | hardly specifiable |
The choice of the appropriate process depends largely on the number of units, the type of component, and the cost requirements. A quick basis for decision-making:
| Quantity | Recommended plastic process | Why? |
|---|---|---|
| 1–20 pieces | 3D printing or CNC milling | Maximum flexibility, no tooling costs, ideal for prototypes or functional samples. |
| 20–500 pieces | Thermoforming | Very low tooling costs, fast implementation, economical for small series. |
| 10,000 - 100,000 pieces | Thermoforming or injection molding (to be considered individually) | Thermoforming is most cost-effective for thin-walled, large components; injection molding is useful for high precision/detail requirements. |
| 100,000+ pieces | typically injection molding (or thermoforming with appropriate tools) | High tooling costs are offset by minimal unit costs. |
Choosing the right process determines costs, speed, and technical performance. With formary, you not only receive high-quality products, but also support in selecting materials, surfaces, and the optimal process.
On request, we can also check whether a combination of several plastic manufacturing processes makes sense—for example, prototyping using 3D printing and subsequent series production using thermoforming. Start now with your inquiry via the formary configurator and realize your next project quickly and efficiently.
The most important plastic manufacturing processes include thermoforming, injection molding, CNC milling, 3D printing, and foaming, such as foam solutions. The most suitable process depends on the number of units, geometry, material requirements, and budget.
