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The Fundamentals of Micro Molding

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The world of micro molding is growing in medical devices, drug delivery, sensors, aerospace, and other industries that depend on ultra-small parts.

Micro molding is a molding process for the manufacture of plastic components for shot weights of 1 to 0.1 g with tolerances in the range of 10 to 100 microns. This molding process allows manufacturers to produce complicated small geometries with maximum possible accuracy and precision.

One of the first things to learn about micro molding is its spelling. While the most common spelling in the industry is “micro molding,” it’s also commonly spelled “micromolding.” In Europe, it’s often spelled, “micromoulding.”

The micro molding process starts in a tooling department where a mold is created that has a cavity in the shape of the part desired. Thermoplastic or resin is rapidly injected into the cavity, creating the component or part at high speed.

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An Accumold technician designs a micro molded part.

The Rise of Tiny Parts

According to the micro molding company, Accumold, the rise of micro molding was prompted by increasing interest from designers and manufacturers in producing smaller, lighter, and more precise devices and specialized equipment. To miniaturize technology, manufacturers must first procure high precision, micro-featured plastic parts.

Part size is an obvious factor in determining micro molding, but it’s not the only factor that matters. Micro molding produces a component or part that is: micro in size, micro in features, micro in tolerances.

The basic concept of the micro injection molding process is quite similar to the regular injection molding process. The micro injection unit is integrated into the injection molding machine.

This video offers a quick description of the essence of micro molding:

Multiple Industries Need Smaller Parts

The miniaturization of parts in automotive, medical, electronics, and telecommunications is driving the need for micro molding. Small parts are no required for applications in automobiles, medical and healthcare products, micro-optics, electronics, and packaging. “One of the primary markets is the sensor market. Whether it's an autonomous vehicle or home appliances, the need for sensors is growing,” Aaron Johnson, VP of marketing and customer strategy at Accumold, told Design News. “The smaller the better. Miniaturization has been trending for decades, and it hasn’t stopped. People are trying to do more in less space.”

According to a report from Research and Markets released in January, the global micro injection molding market is expected to grow from $904 million in 2020 to $1.6 billion by 2025, at a compound annual growth rate (CAGR) of 11.8%.

The North American micro injection molding market should grow from $330 million in 2020 to $579 million by 2025, at a CAGR of 11.9%.

The Asia-Pacific micro injection molding market should grow from $257.9 million in 2020 to $456 million by 2025, at a CAGR of 12.1%.

Micro Molding in Medical

The need for small parts is widespread in the medical industry. This includes surgical devices, endoscopic devices, catheters, testing devices, diabetes-management tools, and electronic components for medical devices. Micro parts are needed for microfluidics applications and pharmaceutical applications that include drug delivery devices, blood collection tubes, syringes, and IV parts. “The need for miniaturization is particularly high for medical devices,” said Johnson. “That includes diagnostics and drug delivery. The drug delivery includes sensors and monitoring.”

According to Johnson, the need for micro parts in medical is continuing to expand. “The medical devices are moving more in the smaller space. That includes applications such as transcatheter, vision tools, and sensors,” said Johnson. “They’re always looking for something smaller than they're currently doing.”

Materials in Micro Molding

Common materials for micro molding include:

  • Polyethylene
  • Polypropylene
  • Nylon (Polyamide)
  • Polycarbonate
  • Delrin – Acetal, Polyoxymethylene, and POM
  • Polysulfone
  • Polybutylene terephthalate
  • Acrylic – Polymethylmethacrylate and PMMA

While materials for micro molding are continually developing, they are not getting introduced at the firehose rate of materials for 3D printing. “As for materials, the demand for material development isn’t growing at the rate as the demand for miniaturization,” said Johnson.

Rob Spiegel has covered manufacturing for 19 years, 17 of them for Design News. Other topics he has covered include automation, supply chain technology, alternative energy, and cybersecurity. For 10 years, he was the owner and publisher of the food magazine Chile Pepper.

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