Vincent Hua from Tsinfa gave Medical Plastics News their expert opinion on micro moulding and medical plastics.

Manufacturers of medical devices, electronics, and biopharmaceuticals require newer micro-moulded goods to make tinier, less intrusive, and space-saving micro devices. Recent breakthroughs in micro-machining technology make it possible to design and manufacture micro moulds for use in surgical devices and other applications. It has resulted in global advancements in less invasive medical and pharmaceutical micro devices.

Micro moulding is a distinct kind of tight tolerance injection moulding method that necessitates precision and skill. It is a process where aluminium moulds or micro-structured steel are Computer Numerical Control (CNC) machined to a submicron or even a micron resolution. This product is small and light and used in specialised industries and crucial applications. Finished components can easily weigh less than 1 g and have cross-sectional dimensions less than 1 mm.

A precise technique is designed for the mouldable material to achieve its melting point and then transfer it to the micro-moulding chamber to produce a micro-component. It creates a mould with a cavity specifying the shape of the component and injects mouldable material into the cavity. The required part is produced once the material is set. Because micro moulding machines offer higher resolution choices, they can inject a gram's fraction with excellent precision, resulting in equal pressure distribution. 

While micro moulding is about filling, CNC machining is a subtractive process that uses cutting tools and high-speed rotation to produce custom-designed parts or components by progressively removing material until the desired shape for the part is achieved. The CNC relies on digital instructions, often created using Computer-Aided Manufacturing (CAM) or Computer-Aided Design (CAD) software. The computer converts these files into a series of commands, which are then supplied to one or more milling tools, which work on the material to create the final product. It enables a quick transition between digital designs and physical parts.

The manufacture of medical products encompasses a wide range of devices used in medical practice, ranging from surgical tools to testing equipment to pharmaceutical storage containers. As a result, the medical tools utilised must be tiny and refined. Thus, micro moulding is widely used in the manufacture of medical equipment like catheters, optical and hearing aid components, drug delivery devices, and so on, and is especially useful for instruments used in minimally invasive procedures. Listed below are reasons for micro-moulding to be well-suited to medical device manufacturing.

Medical plastic micro-molding helps cut unnecessary costs. Although the moulding tool has a high initial cost against other production techniques, the mould only needs to be manufactured once. It gets replaced after hundreds of thousands of runs, and this will be easier and less expensive to replicate.

Undoubtedly, the domain of medicine as a whole necessitates tremendous precision in most of the procedures, with no room for errors or deviations. Micro moulding has a high level of accuracy and precision. Because of the narrow tolerance margin, every inch, millimetre, or centimetre count impacts the overall moulding development.

The materials used in this manufacturing method are resistant to contaminant invasion. They also do not require much sanitation to remain germ-free. The medical devices using this technology are biocompatible, non-contaminated, and easy to use and apply.

Plastic micro-moulded medical parts are extremely robust and can withstand the high temperatures required for sterilisation in autoclaves. These materials are tough and resistant to harsh environments and usage. The products manufactured can tolerate heat, force, and vibration without cracking or breaking, making them suitable for medical purposes.

When selecting a material, the first thing you have to consider is the purpose of the part and the physical environment to which it will be exposed. So, you will need to examine what type of material will withstand various environmental problems such as temperature variations, moisture, chemical exposure, UV light, and others. 

The material's strength, durability, flexibility, and cost are next considered. As a result, I would like to assist you in narrowing your search by outlining the qualities of the most common micro-moulding materials used for medical parts. 

Polyethylene is the most widely used plastic in the world. It is a low-cost plastic that is resistant to both moisture and chemicals. It can be as transparent as glass. Engineers and designers choose these materials because they offer a variety of optical clarity and other qualities.

Polypropylene is comparable to polyethylene (PE) in characteristics, except it is slightly tougher and more heat resistant. It is the world's second most commonly used plastic. Polypropylene is resistant to chemicals and keeps its shape after torsion or bending. PP also has a high melting point and will not decompose in the presence of moisture or water.

PS polymers are cheap, light, and resistant to moisture and bacterial growth. They are also resistant to gamma radiation, which can sterilise medical instruments. Polystyrene micro-moulding also has strong chemical resistance to diluted acids and bases.

PC plastics are strong, robust, and naturally transparent materials. Its physical qualities are stable over a wide temperature range. When pigmented, the PC preserves its colour and strength throughout time. Polycarbonate is 250 times stronger than glass. PC material is also lightweight and has great optical characteristics that allow light to pass through.

Therefore, you will be able to make an informed selection regarding the material and technique that is optimal for the manufacture of your medical device or component. 

Micro moulding is an efficient means of producing more sophisticated equipment in low volumes, such as medical devices. Many medical products, particularly the expensive ones, are sold in quantities ranging from a few hundred to several thousand every year. 

As a result, the medical industry is one of the most common applications for micro moulded goods. The essence of medical micro moulding is the production of medical devices and components from medical-grade plastic materials that are durable, reliable, and comply with FDA requirements.

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