In the early 20th century, producing moving parts en masse required stamping and hot metal casting. Most plastics were nonexistent and the ones that were around had limited uses. Wood and metal ruled the day, though that gave way to plastics in the early 1930s with the invention of polyethylene, the most common type of plastic today. After that, plastics started showing up everywhere, from bags and bottles to artificial joints and bulletproof vests. Plastic rules our world now, but we’re not done refining its use. New types of plastics come out every year; some can handle extreme temperatures that used to require metals, while others maintain strength, even in parts just nanometers wide. But the most intense developments in plastic production are how we create things with it. Two technologies — 3D printing and micro molding — are making plastics easier to work with and more integral to manufacturing than ever before.
3D printing
Since the 1980s, manufacturers have been using 3D printers to create prototypes, but the technology has come a long way since then. Now 3D printers can produce detailed, near-finished quality prototypes complete with moving parts. They work by depositing layer after layer of material, usually plastic or metal, to create a final product. The machine starts with a digital model that is mapped out to its physical printing space. As the printer works, it operates much like a two-dimensional inkjet printer, laying down line after line of material where it’s needed. For producing small quantities of products or prototyping a design, 3D printing is king. That’s why business is booming for companies like DF Robot in China.
Micro molding
Injection molding requires more lead time; you have to produce a permanent mold for each piece you want to produce and you can’t create full moving parts. The upshot of all the preparation, however, is the ability to churn out hundreds or thousands of parts quickly. Machines feed pellets of material (again, normally plastics) into a hopper before making their way into a heated barrel with a screw. By heating the pellets and forcing them down the barrel, the machine simultaneously melts the plastic and injects it into the mold. All of this happens in less than a second.
Both 3D printing and micro molding involve heating plastic and forming it into shapes, but they do this very differently. The mass production capabilities of micro molding mean that companies can order huge runs of very tiny parts — 20 micron nozzles or gears for camera lenses — and have them completed quickly with a very tight range of tolerance. 3D printing, on the other hand, is too slow (for now) to use for full production, but it allows engineers to create complicated prototypes and models in a fraction of the time — and for a fraction of the cost — that it would take for traditional prototyping. By combining the two technologies, manufacturers could reduce R&D costs while speeding up production with low-cost, high-quality parts.
In the future, we’ll see companies using both of these technologies together more often. As resolutions and speed increase for 3D printing, we may even see the two combine to an extent, though micro molding will always be better at mass production of tiny parts. Eventually, however, manufacturers could offer greater customization for consumers, allowing them to choose from several configurations or designs while still using the same basic components. When manufacturing technology improves, so do our choices.