Guide to Rapid Tooling

Injection molding is one of the most popular manufacturing processes for thermoplastic, silicone, or rubber parts. Due to the excessively high costs of traditional metal tooling, it is also the process that can benefit most from rapid tooling. 

With affordable desktop 3D printers and temperature-resistant 3D printing materials, it is possible to create 3D printed injection molds in-house to produce functional prototypes and small, functional parts in production plastics. 

For low-volume production (approximately 10-1000 parts), 3D printed injection molds save time and money compared to expensive metal molds. They also enable a more agile manufacturing and product development approach, allowing engineers and designers to create functional prototypes or low-volume end-use parts to validate material choice and continue to iterate on their designs with low lead times and cost before investing in hard tooling.

Stereolithography (SLA) 3D printing provides a cost-effective alternative to machining aluminum or steel molds. SLA 3D printed parts are fully solid and isotropic, and materials are available with a heat deflection temperature of up to 238°C @ 0.45 MPa, meaning that they can withstand the heat and pressure of the injection molding process.

Shenzhen-based contract manufacturer Multiplus uses 3D printed injection molds with the highly glass-filled and heat resistant Rigid 10K Resin on Form 3 SLA 3D printers, shortening lead times for small batches of around 100 injection molded parts, from four weeks to only three days.

Additional examples include emergency mask straps by petrochemical company Braskem and prototype and pre-production parts for the clients of manual injection molding machine manufacturer Holimaker.

As an alternative for mid-volume production of about 500 to 10,000 parts, machining molds out of aluminum can also reduce the fixed costs associated with manufacturing molds. Machining aluminum is five to ten times faster than steel and causes less wear on the tooling, which means shorter lead times and lower costs. Aluminum also conducts heat faster than steel, resulting in less need for cooling channels and allowing manufacturers to simplify mold designs while maintaining short cycle times.

Thermoforming is an all-inclusive manufacturing process that embraces all the different ways manufacturers may choose to form heated sheets of plastic, such as vacuum forming and pressure forming. Thermoforming processes empower manufacturers to fabricate parts from a diverse range of thermoplastic materials as well as composites. 

Many businesses turn to SLA 3D printing to create molds for thermoforming processes, because it offers a fast turnaround time at a low price point, especially for shorter runs, custom parts, and prototype designs. 3D printing also offers unmatched design freedom to create complex and intricate molds. Use the Form 3+ desktop SLA printer to produce smaller molds, and the Form 3L large format SLA printer for mold sizes up to 33.5 × 20 × 30 cm (13.2 × 7.9 × 11.8 in).

Product development firm Glassboard leverages the fast print speed of Draft Resin to quickly produce molds and thermoform polycarbonate prototypes such as helmet shells or packaging. They can achieve complicated mold shapes that would be difficult to manufacture traditionally, including small features and holes for an even better vacuum distribution across the surface.

Cosmetics manufacturer Lush used to craft the master molds for their popular products by hand. But recently, they turned to 3D printing to create vacuum forming molds for detailed and textured designs, which allows them to take ideas from concept to reality in under 24 hours, and test more than a thousand design ideas each year.

3D printed rapid tooling is also ideal for cost-effectively manufacturing custom or customized end-use parts. For example, vacuum forming over 3D printed models is the go-to method for producing clear aligners in orthodontics.

High-performance composite materials such as carbon fiber can also be hand laminated on 3D printed molds. SLA 3D printers offer a smooth surface finish that is essential for layup molds.

The Formula Student team of TU Berlin hand laminates carbon fiber parts on 3D printed molds for racing cars. Printed with Tough 1500 Resin, the mold is not only strong and supportive during the layup but also sufficiently flexible to separate the part from the mold after curing, unlocking design possibilities.

Rapid tooling with 3D printed molds can also be employed for molding plastic, silicone, or rubber parts and overmolding inserts or internal hardware. 

Google’s ATAP team used 3D printed stand-ins, or surrogate parts instead of overmolded electronic sub-assemblies for the initial tool tuning at the factory

Designers at the Google Advanced Technology and Projects (ATAP) lab were able to cut costs by more than $100,000 and shorten their testing cycle from three weeks to just three days using a combination of 3D printing and insert molding. Google ATAP’s team found that by 3D printing test parts, they could save time and money over using expensive electronic parts that had to be shipped in from a supplier.

Dame Products, a Brooklyn-based startup, designs products for the health and wellness industry. They employ silicone insert molding to encapsulate internal hardware for customer beta prototypes. The Dame Products product line incorporates complex ergonomic geometries fully encapsulated in a layer of skin-safe silicone in vibrant colors.

Engineers prototype dozens of insert and overmolded devices in a single day by rotating through three or four SLA 3D printed molds. While the silicone rubber of one prototype is curing, the next can be demolded and prepared for the next fill; the finishing and cleaning of demolded prototypes happens in parallel. When prototype hardware is returned to the company, the beta device is bleached, the thin silicone layer removed, and the internal hardware is reused in a new beta prototype.

3D printed rapid tooling for compression molding can be leveraged for the production of thermoplastic, silicone, rubber, and composite parts. For prototyping small or medium-size parts, 3D printing may be the cheapest and fastest method for creating molds. Multiple iterations can be made quickly with CAD software, reprinted, and then tested. 3D printing is most commonly used for compression molds intended for heatless applications.

Product developers at kitchen appliance manufacturer OXO use 3D printing for prototyping rubbery components such as gaskets by compression molding two-part silicone using 3D printed molds.

Engineers, designers, jewelers, and hobbyists can capitalize on the speed and flexibility of 3D printing by combining metal casting processes like indirect investment casting, direct investment casting, pewter casting, and sand casting with 3D printed patterns or casting metal into 3D printed molds. Casted metal parts using 3D printed rapid tooling can be produced in a fraction of the time invested in traditional casting and at a significantly lower cost than metal 3D printing. 

Stereolithography 3D printers offer high precision and a broad material library that is well-suited for casting workflows and can produce metal parts at a lower cost, with greater design freedom, and in less time than traditional methods. 

Traditionally, patterns for direct investment casting are carved by hand or machined if the part is a one-off or expected to be only a handful of units. With 3D printing, however, jewelers can directly 3D print the patterns, removing the design and time constraints common in other processes. 

Similar to investment casting, 3D printing can be used to create patterns for sand casting. In comparison to traditional materials like ​​wood, 3D printing allows manufacturers to create complex shapes and go straight from digital design to casting. 

With 3D printing, manufacturers can also directly 3D print the mold for their pattern using materials like High Temp Resin or Rigid 10K Resin, resins with high-temperature resistance. The same method can also be used to create molds for direct pewter casting.

Beyond metals, casting is also a popular method for producing silicone and plastic parts for medical devices, audiology, food-safe applications, and more.

Medical device company Cosm manufactures patient-specific pessaries for patients with pelvic floor disorders. They 3D print molds on an SLA 3D printer and inject biocompatible, medical-grade silicone into it to create the part. Rapid tooling with 3D printing allows them to create custom parts without the high costs of traditional tooling.

Manufacturing custom ear molds with 3D printing has also revolutionized the audiology space, for applications like hearing aids, noise protection, and custom fit earphones. Digital manufacturing provides greater control and accuracy compared to traditional mold production, significantly reducing the number of errors and remakes.

3D printed rapid tooling presents some interesting properties for sheet metal forming as well. Characterized by high precision and a smooth surface finish, SLA 3D printers can fabricate tools with excellent registration features for better repeatability. Thanks to a broad material library with various mechanical properties, choosing a resin tailored to the specific use case can optimize the result of the forming. SLA resins are isotropic and fairly stable under load compared to other 3D printing materials. Plastic tooling can also eliminate a polishing step, as plastic dies do not mark the sheet as metal. 

The mechanism is similar to the general sheet metal forming workflow. The difference lies in the design and print of the two-part tool made of upper and lower dies. The blank sheet is then placed between both plastic dies, and pressed with a hydraulic press or other forming equipment.

3D printing is the fastest and most affordable way to produce rapid tooling for a variety of applications. As we saw in the previous examples, both direct and indirect rapid tooling leverages 3D printing in different ways to develop functional tools, such as molds, patterns, and dies for a variety of traditional manufacturing processes.

From the different 3D printing processes, SLA 3D printers offer the most versatile solutions for tooling. SLA 3D printed parts are accurate, watertight, have a smooth surface finish that is ideal for molds, and can replicate small details for complex molds and patterns.

High-performance SLA materials can also be easily integrated into industrial workflows to fabricate strong, smooth, highly-detailed molds and patterns capable of producing hundreds to thousands of parts.

SLA 3D printing has made in-house rapid tooling more accessible than ever before. A 3D printing workstation can be set up on a reasonable budget and operated easily in house, empowering companies to produce rapid tooling within 24 hours and iterate designs faster than with any other process.

Machining is one of the most common methods for manufacturing conventional tooling and hard tooling, but it can also be leveraged for creating rapid tooling. Instead of durable metals such as steel or nickel alloys, rapid tooling is most commonly machined out of tooling board, wood, plastic, or aluminum.

Compared to 3D printed tooling, machined tooling out of soft materials can be more efficient for large-format tooling and simple shapes, but it gets increasingly labor-intensive and expensive in line with design complexity. Aluminum tooling is more durable and is generally used for low to mid-volume production, especially for injection molding.

Machining tools are more expensive, require a trained operator, and have a complex workflow for in-house production compared to 3D printers, especially for one-off parts like consecutive prototype iterations of rapid tooling. As a result, many companies outsource machining to service providers, but this comes with an often multiple weeks-long lead time and the rapid factor of rapid tooling quickly diminishes.