Medical products continue to shrink in size but grow in capability as the demand increases for more portable and functional devices such as implantables, wearable devices, hearing aids, and surgical instruments. Medical manufacturers must keep up with these advancements and be able to manufacture smaller, more complex devices without sacrificing quality.

The trend toward miniaturization of medical devices has resulted in an increase in micro-injection molding, a form of manufacturing that creates tiny and often complex parts. Below is more information on this form of injection molding and why it is gaining popularity across the healthcare sector. When it comes to selecting a micro-injection molding partner, OEMs must choose wisely as this form of manufacturing requires specialized equipment and skills that many injection molding companies do not possess. The team at ProMed have the know-how and state-of-the-art equipment to successfully perform a broad range of molding methods including micro-injection molding. Our team is focused on meeting the challenges that product miniaturization often present and we are positioned to assist with all of your injection molding needs

What is Micro-Injection Molding?

Micro-injection molding is a tight tolerance method of manufacturing that produces miniscule parts – often weighing significantly less than 1 gram with dimensions measured in millimeters. Many industries benefit from these tiny products including the medical market which has numerous applications for these devices. Healthcare providers as well as patients have pushed for less invasive procedures, thus, medical devices are meeting these demands by becoming smaller with more complex features.

While there are some variations between micro-injection molding methods, the main equipment and process are generally the same. The process begins when silicone is fed into a heated barrel. In the case of Liquid Silicone Rubber (LSR), manufacturing, the two liquid LSR components are stored in separate containers and then fed simultaneously into the barrel. Next, a screw is used to mix, heat, and transport the silicone toward to the mold. The melted material is then injected through a nozzle into the mold and travels via a gate and runner system into the tiny mold cavities; the proper design of the gate and runner system is essential to ensuring the mold is filled properly. As the silicone enters the mold, excess air can be released via vents. The pressure and temperature of the mold are maintained to allow the silicone to conform to the desired shape and harden quickly. Once the part is adequately cooled, the mold opens and the part is ejected, sometimes with the help of ejector pins. The mold is then ready to receive the next shot of silicone.

Micro-injection molding is one of the latest innovations within injection molding. Due to their size, these miniature products weigh significantly less than prior versions of medical devices. This is a significant advancement for medical manufacturing as weight has historically been a challenge for the healthcare sector. Smaller and lighter parts lead to less material usage and lower cost per part – a huge win for medical manufacturing, giving OEMs a competitive advantage.
Benefits of Using LSR for Micro-Injection Moldin

Silicones have long been a popular material for medical devices and medical device components due to their durability, ease of molding by many methods, wide temperature range, chemical inertness, high tensile strength, vast range of available durometers, low toxicity, and compatibility with many sterilization methods. Furthermore, silicone is compatible with human tissue and body fluids, has a very low tissue response when implanted, and does not support bacteria growth – making it a perfect option for implants. Additionally, medical-grade silicones, such as LSR, have undergone stringent purity and biocompatibility testing that make them suitable for short and long-term usage.

LSR has a lower viscosity than many other medical-grade silicones, meaning LSR is less viscous and more readily flows. Due to its lower viscosity, LSR is a good fit for micro-injection molding as it is able to fill the tiny micro spaces in the mold. Additionally, LSR’s desirable handling properties and lower shrink rate make it an excellent choice for manufacturing complex geometries and intricate micro-sized products. Due to the automated nature of injection molding, LSR can produce high volumes of components in a short period of time.

Looking for a reliable and proven partner for your next medical manufacturing project?
Contact ProMed to learn about the range of solutions and materials we offer as well as our decades of silicone injection molding experience.

Challenges of Micro-Injection Molding

While the micro-injection molding process is relatively similar to standard injection molding, there are some challenges that exist due to the scale of micro parts.

Micro-injection molding demands unparalleled precision. The weight and dimensional accuracy required in micro tooling and throughout the molding process is incredible – often measured in millimeters or milligrams. Tooling required for micro-injection molding is specialized and requires extreme attention to detail to ensure consistent alignment throughout the life cycle of the mold – which is often millions of micro parts.

Material dosing is more challenging when working with micro amounts. LSR is a 2-part liquid that cures into a solid form when mixed, which are often referred to as the A and B components. For micro-injection molding, feeding the precise dosage and ratio of A and B components of LSR is crucial to ensure the desired product quality and properties. Additionally, if additives, such as a color, are added the dosage must remain precise in order to achieve consistency from batch to batch.

Micro-injection molding requires a small shot of silicone material. Due to the small volume of material, operating conditions such as pressure and temperature throughout the molding process must be uniform and balanced to ensure proper filling and distribution of the material.

Due to their tiny size and weight, micro parts must be handled more carefully than standard injection molded products. Micro parts are often more fragile and susceptible to damage during handling and assembly. LSR parts are often tacky, further complicating the automated as well as manual handling process for micro parts. In addition, ensuring a thorough and comprehensive inspection of the miniature parts is often a challenge for micro molders.

In order to have a successful project, OEMs must partner with a micro-molder, like ProMed, that has the requisite experience with the equipment, materials, and potential pitfalls of micro-injection molding. Even the slightest deviation during micro-molding will result in parts that are unusable. OEMs must leverage the experience of their micro partner, especially during the part design and prototyping stages where many key decisions are made that will significantly impact the success of the final product.

What OEMs Should Look for in a Micro-Injection Molding Partner?

It is imperative that OEMs understand that not all injection molding companies are equipped for micro-injection molding. OEMs must look for certain characteristics when selecting a micro-molding partner such as quality control, state-of-the-art equipment, and tooling experience. At ProMed, we offer customers a broad range of silicone material and equipment offerings, including micro-injection molding, which enables us to provide support as your business grows over time.

Manufacturers that perform micro-injection molding must have ample experience and expertise with micro-molding equipment. Equipment that is able to manufacture small parts via injection molding is not necessarily able to create micro parts. As noted above, micro-molding operates at very tight tolerances and very small masses – requiring exacting and repeatability that is often not feasible with standard injection molding equipment. OEMs need a manufacturer, like ProMed, that has the necessary know-how and state-of-the-art tooling and equipment to successfully manufacture micro parts.

Similar to injection molding, OEMs must ensure micro-injection molding companies meet the requisite regulations and quality standards for the healthcare sector. Clean rooms are one method that medical manufacturers use to meet these requirements. At ProMed, our manufacturing facilities are equipped with certified class 10,000 / ISO Class 7 clean rooms, demonstrating our strong commitment to quality.

About ProMed

ProMed was founded in 1989 to address an industry need for cleanroom manufacturing of silicone components, specifically those having a medical application. Over time, we broadened our product offerings to include assembly, micro-molding of highly engineered plastics, and combination products. We have garnered a reputation as the world benchmark of implantable silicone components and assemblies – and are one of few companies in the world to provide contract manufacturing of drug-eluting products.

ProMed has expertise in working with the full spectrum of silicones covering a wide range of properties and characteristics. We will assist in your material selection to help ensure all design requirements are met. Our manufacturing facilities and equipment are designed for a single purpose—to mold medical and implantable silicone, combination components, and bio-material grade plastics with uncompromising quality and service. We currently have four divisions that are located within two manufacturing sites. All are certified class 10,000 / ISO Class 7 cleanrooms.

We can identify the right manufacturing solution for any project. We have extensive experience in a wide range of injection molding techniques including:

· Automated Injection Molding

· Multi-cavity tooling

· Micro molds and micro molding

· Servo-controlled de-molding capabilities

· Insert molds, overmolds, and automation integration

· Transfer molding

· Compression molding

Click here to see why ProMed is your silicone injection molding partner. Contact ProMed today at 763-331-3800 to discuss your next silicone injection molding project.