In the years since it joined the World Trade Organization (WTO) in 2001, China has rapidly become the world's largest producer in terms of output. Much of this manufacturing power comes from the Pearl River Delta area, a cluster of nine cities in southern Guangdong province that includes Shenzhen. In 2020, this region accounted for roughly a third of China's trade value.
Driven by this rapid growth, many small workshops have grown into international companies. Founded in 2005 in Shenzhen, Multiplus started as a micro-injection molding workshop and quickly became a solution provider covering the entire production cycle, from design to production of plastic products, both large and small, single or multiple (when two or more materials or colors are injection molded in one mold). Today, Multiplus serves more than 250 clients annually, including some of the Fortune 500 companies.
Some of these clients require small batch production, which is traditionally expensive and time consuming with injection molding due to the complexity of producing hard tools.
Multiplus uses 3D printed injection molds to reduce the production time for small batches of around 100 injection molded parts from four weeks to just three days.
Growing demand for small batch production
In most cases, the molds used in injection molding are made of metals such as steel or aluminum. However, when it comes to small-batch production, metal molds can be a significant expense because they are expensive and time-consuming to make.
"Although it's not the majority of what we do now, small batch production requests are becoming more common. Some are for design and functionality validation, but many are becoming end-use. This makes sense, as more and more companies want to test the market," said Kevin Lee, CEO of Multiplus.
Several years ago, Multiplus adopted 3D printing and has since purchased several 3D printers, mainly for printing communication models and design validation parts in various materials. As demand for small-batch production began to increase, Multiplus turned to 3D printing to explore different materials in an attempt to find a cost-effective way to produce cheaper plastic molds for smaller orders. Small batch production of injection molds with Formlabs 3D printers reduced costs, labor and time compared to machining aluminum molds and could be used seamlessly with their Babyplast industrial injection molding machines.
One of the materials Multiplus tested was Formlabs Rigid 10K Resin, a glass-filled resin that is very rigid, strong, as well as heat and chemical resistant, which are required properties for injection molding. Additionally, parts printed in Rigid 10K Resin on a Form 3 SLA 3D printer have a smooth matte finish that transfers to the clean surface finishes of the injected parts.
Cutting production time from four weeks to one
Multiplus has tested injection molding parts with ABS, PP, PC+ABS and PC. After designing the mold, they would print and post-process the mold in a day, assemble the molds in the assembly shop in about half an hour, and begin injection molding on their injection molding machines. Once injection molding begins, it takes approximately 3 minutes to complete the part. Multiplus limits each mold to approximately 100 uses and prints multiple molds for larger order quantities.
With multiple 3D printers and injection molding machines in the workshop, Multiplus can deliver hundreds of pieces in just 3 days, significantly shorter than the 3-4 weeks it would take to injection mold parts using a CNC machined metal mold.
| Injection molding of 100 parts | SLA 3D printed mold | CNC machined mold |
|---|---|---|
| Delivery time | 3-5 days | 3-4 weeks |
"Having the Form 3 on the production line has made our mold making process much more agile, and the Rigid 10K resin is one of the best materials we've ever used for injection molding. Now we can respond to customer requests much faster."
Kevin Lee
Injection molding conditions and results
Multiplus used its 3D printed injection molds with the Babyplast 10/12 Standard machine under a wide range of pressures, temperatures and materials. The part tested was the housing of a control box for home appliances, including several small details.
From these tests, we observed that PP injected at 180°C was quite easy to process. Multiplus received injected parts of good quality and smooth surfaces. The injection mold lasted 100 injections and was still in good condition. Similarly, ABS was processed at 220°C for 60 cycles without damaging the mold. Multiplus did not test the molds to failure due to the busy production schedule, but would expect lifetimes to be above 100 iterations per mold for PP, ABS and PC-ABS.
Tests with PC at 260°C resulted in mold cracking after only four iterations. This shows that plastics above 250°C with high viscosity are challenging to process with the Rigid 10K 3D printed mold, especially for this thin-walled geometry. High Temp Resin has a higher heat bending temperature and can be considered as an alternative material when clamping and injection pressures are not too high.
| Material | PP | ABS | PC-ABS | PC |
|---|---|---|---|---|
| Injection temperature (nozzle) | 180℃ | 220℃ | 240℃ | 260℃ |
| Injection volume | 36 cc | 39 cc | 37 cc | 40 cc |
| Cooling time | 80 sec | 60 sec | 50 sec. | 90 sec. |
| Injection pressure | 60 bar | 95 bar | 95 bar | 110 bar |
| Holding pressure | 35 bar | 30 bar | 25 bar | 80 bar |
| Holding time | 0 sec | 1.5 sec | 1 sec | 2.5 sec |
| Number of cycles | 100+ | 60+ | 60+ | 4 |
Small batch injection molding with 3D printed molds
By integrating 3D printing into its injection molding process, Multiplus has been able to grow its business, take on more business and be more competitive, all while reducing costs, improving turnaround time and helping its customers bring better products to market faster.
Download the white paper or watch the webinar for detailed workflow, design guidelines, and other best practices for using 3D printed molds in the injection molding process, as well as additional real-world case studies from Novus, Braskem, and Holimaker.