Although injection molding is traditionally considered the manufacturing process for mass production due to the high cost of molds, using 3D printing technology to create injection molding molds can allow you to utilize this process to produce high-quality, repeatable parts for prototyping and low-volume production.

This comprehensive guide will teach you how to use 3D printed injection molds with both desktop and industrial machines to efficiently and cost-effectively produce hundreds of functional prototypes and mass-produced parts. This accelerates the product development process, reduces costs and production times, and enables better products to reach market faster.

Low-volume injection molding compared to traditional injection molding.

Injection molding is one of the main processes for plastic manufacturing. It is a cost-effective and highly repeatable technology that delivers high-quality parts in mass production. Therefore, it is widely used for producing many identical parts with tight tolerances.

Injection molding is a fast and intensive process involving high heat and pressure to inject molten material into a mold. The molten material depends on the scope of the production project. The most commonly used materials are various thermoplastics such as ABS, PS, PE, PC, PP, or TPU, but metals and ceramics can also be injection molded. The mold consists of a cavity that holds the injected molten material and is designed to closely resemble the final shape and properties of the part.

Typically, molds are manufactured from metal using CNC machining or EDM (Electric Discharge Machining), a costly industrial process requiring specialized equipment, advanced software, and highly skilled labor. As a result, metal mold production typically takes between four and eight weeks and costs range from $2,000 to over $100,000 depending on the shape and complexity of the part. For small-scale production, the cost, time, specialized equipment, and labor required to create metal molds using conventional manufacturing methods often make this level of injection molding practically impossible.

However, there are alternatives to metal machining. Using in-house 3D printing to create injection molding dies for prototyping and low-volume production can significantly reduce costs and time compared to metal dies, while still producing high-quality, repeatable parts.

In this video, we collaborated with Multiplus, a plastic injection molding service provider, to take you through the injection molding process using 3D-printed molds.

Desktop 3D printing is a powerful alternative to rapid, low-cost injection molding, requiring minimal equipment. This saves CNC machines and skilled labor, allowing those resources to be used for higher-value projects in the same timeframe. Manufacturers can leverage the speed and flexibility of on-premise 3D printing to create molds and match them with the production capacity of injection molding processes, delivering a number of parts made from common thermoplastics in days. It can also create complex mold shapes that are difficult to produce using traditional methods and is compatible with both desktop and industrial-scale injection molding machines, enabling product development teams to innovate more extensively.

Furthermore, the product development process benefits from the ability to iterate through design modifications and test actual materials used in real-world applications before investing in permanent mold tooling.

While 3D printing offers these advantages when used properly, it also has some limitations that should be considered. We shouldn't expect the same performance as machined metal molds from 3D-printed polymer molds. High precision sizing can be more difficult, cooling times are longer due to slower heat transfer in plastic, and the printed mold may be more prone to breakage under heat and pressure. Nevertheless, companies across many industries continue to choose 3D-printed molds for short-run injection molding, enabling the rapid production of hundreds or thousands of parts. Whether it's designing functional prototypes using real materials, pilot production, or small-volume production of specialized parts for real-world applications, 3D printing remains a cost-effective and rapid solution for producing limited quantities of parts.

Stereolithography (SLA) resin 3D printing technology is an excellent alternative for mold making, offering superior surface smoothness and high precision. These qualities are transferred from the mold to the final part, facilitating easy mold removal. SLA-printed parts are chemically bonded, resulting in perfect density and uniform mechanical properties in all directions—a feat not achievable with melt-blown modeling (FDM). Desktop SLA printers, such as those produced by Formlabs, integrate seamlessly with injection molding processes due to their ease of use, setup, and maintenance.

The 3D-printed injection mold core is assembled onto the metal mold shell.

As an alternative for medium-scale production of approximately 500 to 10,000 pieces, milling aluminum dies can also help reduce the fixed costs associated with die manufacturing. Milling aluminum takes five to ten times less time than milling steel and results in less tool wear, leading to shorter lead times and lower costs. Furthermore, aluminum conducts heat faster than steel, reducing the need for heat sinks and allowing manufacturers to design simpler dies while maintaining shorter cycle times.

To summarize, the following is an overview of the different injection molding methods and the types of molds best suited for each production volume range, considering process efficiency and the lowest cost per unit:

Injection molding type	Low-Volume Injection Molding	Mid-Volume Injection Molding	High-Volume Injection Molding
way	In-house mold manufacturing and in-house injection molding.	Outsourcing the production of molds and injection molding.	Outsourcing the production of molds and injection molding.
Required equipment	3D printer, desktop injection molding machine.	–	–
Mold material	3D printed polymers	Machined aluminum	Machined steel
Mold cost	< $100	$2,000 – $5,000	$10,000 – $100,000
The time until the final piece of work is completed.	1-3 days	3-4 weeks	4–8 weeks
Optimal production volume	< 500 pieces	500 – 10,000 pieces	More than 5,000 pieces
Proper use	Rapid prototyping
Custom injection molding for each customer.
Small batch injection molding	Small batch injection molding	Mass production

The type of injection molding machine does not have a significant impact on low-volume injection molding processes. Traditional, large-scale industrial injection molding machines can also be used with 3D-printed molds. However, these machines are expensive, require standardized installation sites, and demand highly skilled labor. For this reason, most companies choose to outsource mid-to-high-level manufacturing to service providers or contract manufacturers instead.

If you're new to injection molding and looking to test the waters with a limited investment, a benchtop manual injection molding machine like the Holipress or Galomb Model-B100 is a good option. Alternatively, smaller, automated injection molding machines such as the Micromolder (benchtop) or Babyplast 10/12 (hydraulic) are also good choices for producing small parts in medium quantities.

Want to know what factors contribute to the "total cost" of injection molding?
Read our full guide!

Step-by-step procedure for low-volume injection molding.

The low-volume injection molding process consists of 7 main steps, as follows:

1. Mold Design Design the mold for your part in your chosen CAD software. Use general design rules for additive manufacturing and injection mold design. Specific guidance for polymer-printed molds can be found in our white paper. Upload your design to PreForm, Formlabs' print preparation software, then prepare the print and send it to a Formlabs 3D printer.
2. 3D Mold Printing Choose your 3D printing material and begin printing. Rigid 10K Resin at a layer resolution of 50 microns is a suitable choice for most mold designs due to its high strength, hardness, and heat resistance. If possible, it is recommended to print the printing plate flat on the press, without using supports, to help reduce warping. After washing and hardening, your 3D mold is ready to be used in the injection molding process.
3. Mold Assembly Before assembly, you may choose to finish the surface or adjust key dimensions of the mold using hand polishing, benchtop machines, or CNC milling. It is recommended to place the printed die into a standard metal frame or Master Unit Die to help withstand high pressure and extend the lifespan of the 3D printed die. Carefully assemble the 3D printed die onto the metal frame, adding ejector pins, inserts, side-action parts, and other components as needed. Install the assembled mold into your plastic injection molding machine.
4. Mold Clamping Load the plastic pellets, enter the desired settings, and begin production. It is recommended to use low clamping force, especially if the printing mold is not protected by a metal frame. We can inject various types of plastics using 3D molds, such as TPE, PP, PE, ABS, POM, ASA, PA, PC, or TPU.
5. Plastic Injection Molding Multiple injection moldings may be required to find the optimal operating conditions, as many factors are involved, including part shape, plastic type, injection temperature and pressure, and other parameters. Reduce the injection pressure and temperature as much as possible. Based on customer feedback, a single Formlabs mold can produce hundreds of parts using easily injectable plastics such as TPE, PP, and PE at temperatures up to 250°C. Plastics requiring higher temperatures, such as PA or PC, may shorten the mold's lifespan. Read our operating conditions documentation for test results from both benchtop and industrial injection molding machines.
6. Cooling The cooling time for polymer-printed molds is longer than for metal molds because heat transfer is slower in plastic than in metal. Therefore, adding cooling vents to printed molds is generally not recommended. Accelerate cooling by using compressed air to reduce the mold temperature, or by using interchangeable mold stacks.
7. Removing the workpiece from the mold (Demolding) Remove the molded part manually or with an automatic demolition pin. Use a release agent for high-viscosity plastics. Release agents are widely available, and silicone release agents such as Slide or Sprayon are suitable for use with Formlabs resins.

The use of low-volume injection molding.

The three main applications for low-volume injection molding are rapid prototyping, short-run injection molding, and custom or bespoke injection molding.

Rapid prototyping with injection molding

Rapid prototyping allows companies to transform ideas into proven prototypes, developing these highly detailed prototypes that look and function like the actual product. The products are then subjected to rigorous testing and move towards mass production.

3D printing is generally the most commonly used method for rapid prototyping. However, towards the end of the development process, it is often necessary to produce slightly larger quantities of identical prototypes using the same materials and manufacturing processes as the final product. These prototypes can then undergo beta testing and field testing. Combining 3D printed molds with injection molding allows manufacturers to develop functional prototypes quickly and efficiently, accelerating the product development process.

For example, a French startup called Holimaker has developed a manual plastic injection molding machine that allows engineers and product designers to produce small quantities of plastic parts on their workbench for prototyping, trial production, or even limited production runs of functional components.

The company offers feasibility studies to clients using 3D-printed molds for a fast and cost-effective process. This allows their clients to quickly and cost-efficiently prototype designs and effectively verify real-world production conditions during the pilot production phase of new products.

Holimaker uses 3D-printed molds to injection mold prototypes of valve joint components from POM (polyoxymethylene) material for customers, which are then subjected to water pressure resistance testing.

By using the same manufacturing process, including mold design and materials, these parts can be field-tested, ensuring the design is ready for mass production. These 3D-printed mold designs can then be easily adapted for use as steel tooling molds during the mass production phase.

By using 3D-printed molds, Holimaker can reduce mold production time for plastic injection molding to just 24 hours, and currently they use 3D-printed molds in 80% to 90% of all their projects.

Short-Run Injection Molding

Short-run injection molding allows manufacturers to produce small quantities of functional parts for products with limited production runs or for pilot series production to test the market before investing large sums of capital in a larger project.

The use of low-volume injection molding opens up opportunities to produce precise, repeatable, functional parts without the high fixed costs associated with traditional injection molding processes.

Multiplus is a Shenzhen-based injection molding solutions provider, covering the entire production cycle from design to plastic product manufacturing. It serves over 250 clients annually, including some Fortune 500 companies. Some of these clients require low-volume production, which is typically costly and time-consuming with injection molding due to the complexity of hard tooling.

Freshly injection-molded control box housings made from ABS material using 3D-printed injection molds.

As the demand for small-batch production increased, Multiplus turned to 3D printing technology to explore various materials, with the goal of finding a more cost-effective way to produce inexpensive plastic molds for small orders and pilot production.

Creating low-volume injection molds with professional 3D printers from Formlabs significantly reduces costs, labor, and time compared to aluminum milling, and is seamlessly compatible with their Babyplast industrial injection molding machines.

On-demand or custom injection molding

Bespoke or custom injection molding, especially for urgent on-demand production, may be necessary to manufacture functional parts tailored to specific purposes, such as human factors, operating environments, or unique opportunities. These often require time constraints, limited quantities, and/or short production lead times. This means traditional injection molding using hard tooling is inefficient or impractical. In such cases, low-volume injection molding using 3D-printed molds becomes a suitable solution to accelerate the process and deliver customized parts.

The example of Braskem, one of the world's leading petrochemical companies, demonstrates the use of 3D-printed injection molding to meet urgent, on-demand production orders during the first wave of the COVID-19 pandemic. The company needed to produce thousands of mask straps to protect its global workforce. Braskem stated that injection molding was the most suitable method for manufacturing these parts, but without access to 3D printing, they would have had to outsource the production of expensive metal molds, incurring significant financial and time costs for their team.

Braskem used 3D-printed molds in conjunction with traditional industrial injection molding machines to rapidly mold mask straps for a large volume of parts in a short timeframe. This method allowed for rapid production of parts without the time and expense of traditional metal molds.

Braskem's team opted for injection molding, using a Formlabs Form 3 3D printer to print the molds for the mask straps and a fully electric Cincinnati Milacron 110 Ton Roboshot injection molding machine to produce these straps.

Using 3D printing technology, the team was able to produce thousands of straps within just one week of receiving an email from the company's vice president and quickly arrange for shipments to offices worldwide.

Get Started With Low-Volume Injection Molding

Accelerate product development, reduce costs and production times, and bring better products to market faster by integrating 3D printing and low-volume injection molding into your development processes.