May. 06, 2024
Hardware
While injection molding has traditionally been associated with mass production due to its significant tooling expenses, the integration of 3D printing for creating injection molds enables the process for high-quality part fabrication even in prototyping and low-volume scenarios.
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This extensive guide will delve into the utilization of 3D printed injection molds with both benchtop and industrial machinery, facilitating the cost-effective and efficient production of hundreds of functional prototypes. This technique can accelerate product development, reduce costs and lead times, and ultimately lead to superior products entering the market faster.
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Injection molding remains one of the most prevalent techniques for creating plastic products due to its cost-effectiveness and ability to produce high-precision, quality parts in large volumes. It's commonly employed for mass production due to these properties.
In the injection molding process, molten material is injected into a mold cavity under high heat and pressure, forming a part once the material cools and solidifies. The mold, usually crafted from metal through CNC machining or electric discharge machining (EDM), is designed to reflect the final product's features precisely.
The traditional mold fabrication process, involving high-end metal materials and sophisticated equipment, usually takes between four to eight weeks and can cost anywhere from $2,000 to over $100,000, depending on the design's complexity. For smaller production volumes, the high cost, time, and expert labor needed for making metal molds render traditional methods impractical. However, by using in-house 3D printing to create molds, one can significantly cut down on both time and expenses while maintaining high-quality and precision in smaller production runs.
In this video, we're partnering with injection molding service provider Multiplus to demonstrate the injection molding process using 3D printed molds.
Desktop 3D printing offers a rapid, low-cost means of fabricating injection molds, needing minimal equipment. This frees up CNC machines and skilled operators for more critical tasks. The speed and flexibility of desktop 3D printing combined with injection molding allow manufacturers to produce series of units from common thermoplastics in a few days. Complex mold designs, difficult to achieve traditionally, can also be fabricated this way, enhancing innovation and allowing development teams to test end-use materials before committing to hard tooling.
Although 3D printed molds present several advantages, they do come with limitations. They do not offer the same performance as machined metal molds; critical dimensions are more challenging to achieve, cooling times are longer due to slower thermal transfer, and the printed molds can break under extreme conditions. Despite these limitations, many companies are incorporating 3D printed molds for short runs, producing hundreds to thousands of parts, developing functional prototypes, and fabricating low-volume end-use parts cost-effectively and quickly.
Stereolithography (SLA) 3D printing is ideal for molding due to its smooth surface finish and high precision, facilitating demolding. SLA prints are fully dense and isotropic, creating high-quality functional molds not possible with fused deposition modeling (FDM) printers. Desktop SLA printers like those from Formlabs can be easily integrated into any injection molding workflow as they are straightforward to implement and maintain.
A 3D printed injection mold core combined with a metal mold shell.
For mid-volume production (500 to 10,000 parts), aluminum molds Machining can drastically cut fixed costs. Machining aluminum is considerably faster than steel, offers lower wear on the tooling, and requires simpler molds due to aluminum's better heat conductivity, leading to shorter cycle times.
Here's a summary comparing the different injection molding methods based on production volume, efficiency, and cost:
| Method | Equipment Required | Mold | Mold Cost | Lead Time to Final Parts | Production Volume | Applications |
|---|---|---|---|---|---|---|
| Low-Volume Injection Molding | In house mold production and in-house molding | 3D printed polymer | <$100 | 1-3 days | <500 | Rapid prototyping, Custom injection molding, Short-run injection molding |
| Mid-Volume Injection Molding | Outsourced mold production and molding | Machined aluminum | $2,000 - $5,000 | 3-4 weeks | 500 - 10,000 | Short-run injection molding |
| High-Volume Injection Molding | Outsourced mold production and molding | Machined steel | $10,000 - $100,000 | 4-8 weeks | 5,000+ | Mass production |
The type of injection press employed doesn't significantly affect the low-volume molding process; both large industrial machines and 3D printed molds are effective. However, traditional industrial machines are costly, strict in facility requirements, and labor-intensive, prompting many enterprises to outsource mid- and high-volume production.
For newcomers to injection molding, starting with a benchtop manual machine such as the Holipress or Galomb Model-B100 may be a cost-effective option. Small-scale automated machines like the desktop Micromolder or hydraulic Babyplast 10/12 serve well for medium-series small-part production.
Keen on understanding the different factors that contribute to overall injection molding costs? Explore our detailed guide.
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The workflow entails seven main steps:
Design your part's mold in CAD software, following standard additive manufacturing and injection mold design rules. Specific recommendations for polymer 3D printed molds can be found in our whitepaper.
Upload your design into PreForm, the print preparation software, and send it to your Formlabs 3D printer.
Select a suitable 3D printing material such as Rigid 10K Resin with a 50-micron layer height, ideal for combining strength, stiffness, and thermal resistance.
Printing the mold flat on the build platform is advised to minimize warping. After washing and post-curing, your 3D printed mold is ready for the injection molding process.
Finish the mold to critical dimensions with sanding or CNC machining if necessary.
Place the printed mold in a metal frame to counteract high pressures and prolong its life. Assemble the 3D printed mold inside the frame, adding other components such as ejector pins and inserts.
Install the assembled mold in your injection molding machine.
Insert plastic pellets, adjust settings, and start production. Using a lower clamping force is ideal if the mold is not supported by a metal frame.
A range of thermoplastics like TPE, PP, PE, ABS, POM, ASA, PA, PC, or TPU can be injected into 3D printed molds.
Initial shots might be required to establish ideal process conditions due to variables like part geometry, plastic choice, and injection parameters.
Minimize injection pressure and temperature as much as possible.
Formlabs users usually achieve hundreds of parts with easy-to-process plastics like TPE, PP, and PE, sustaining temperatures up to 250°C. For heat-sensitive plastics like PA or PC, the mold may have a shorter lifespan.
Review our process conditions documentation for test results on different molding machines.
Polymer printed molds take longer to cool compared to metal molds due to slower thermal transfer. Adding cooling channels is generally not recommended.
Cooling can be sped up with compressed air or interchangeable stacks.
Manually or automatically demold the part using ejector pins. Use a release agent for high-viscosity thermoplastics. Silicone mold releases like Slide or Sprayon are compatible with Formlabs Resins.
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This white paper offers insights into integrating rapid tooling with conventional manufacturing methods such as injection molding, thermoforming, or casting.
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Contact us to discuss your Rapid Tooling For Plastic Part Prototypes needs. Our knowledgeable sales team will help you find the best solutions.
Suggested reading:Low-volume injection molding finds its main applications in rapid prototyping, short-term injection molding, and custom on-demand injection molding.
Rapid prototyping enables companies to convert ideas into tangible proofs of concept, advancing these prototypes to high-fidelity models resembling final products, and guiding these prototypes through validation stages towards mass production.
While 3D printing is the predominant method for rapid prototyping, later development stages often require slightly larger volumes of identical prototypes made with the final parts' materials and processes. These prototypes are essential for applications such as beta testing. Combining 3D printed molds with injection molding allows for swift and efficient functional prototype production, thereby speeding up the development process.
For instance, French startup Holimaker offers a manual injection molding machine for engineers and designers to produce plastic parts on their desktop in low volumes for prototyping, pilot production, or limited series of end-use parts.
Holimaker provides feasibility studies using 3D printed molds for fast and cost-effective turnarounds, enabling clients to prototype designs quickly and validate manufacturing conditions during pilot production. These parts can then undergo field testing to ensure designs are production-ready, with molds easily adaptable for tool-grade steel in mass production.
Holimaker used 3D printed molds to create POM valve connector prototypes for a customer conducting water pressure resistance tests.
By using the same methods and materials for prototyping as final production, parts can be tested in real-world conditions, confirming they are ready for larger-scale manufacturing. Holimaker consistently uses 3D printed molds in 80% to 90% of their projects today, shortening mold production lead time to merely 24 hours.
Short-run injection molding allows manufacturers to produce small series of end-use parts for limited production quantities or test the market with pilot series before significant capital investments.
Low-volume injection molding offers a cost-effective means to manufacture accurate and repeatable end-use parts without the prohibitive fixed costs of traditional methods.
Shenzhen-based Multiplus, an injection molding solutions provider, covers the full production cycle for over 250 clients annually, including Fortune 500 companies. Some require smaller batch production, typically expensive and time-consuming due to hard tooling complexities.
Multiplus explored 3D printing to create low-cost plastic molds for small orders and pilot runs, finding significant reductions in costs, labor, and time compared to aluminum molds. Their professional 3D printers paired seamlessly with Babyplast industrial injection machines for low-volume production runs.
Rapid on-demand or custom injection molding can be essential for specific applications, human factors, or events, often requiring expedited timelines. Traditional hard tooling methods are inefficient for limited volume and short lead-time projects. Low-volume injection molding using 3D printed molds offers the ideal solution, speeding up the process and ensuring timely delivery of custom parts.
Braskem, a global petrochemical leader, provides a compelling example. During the initial COVID-19 wave, Braskem needed thousands of mask straps to safeguard their global workforce. Without 3D printing, outsourcing expensive metal molds would have wasted time and resources.
Using a Formlabs Form 3 3D printer, Braskem quickly produced the
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