A few weeks ago, we talked about the exceptional characteristics of the polymers used in orthopedic surgery with particular reference to PLLA. (see article https://www.legheleggere.com/green-device-for-orthopedic-surgical-use/).
Let’s see how to manufacture implantable medical devices with this GREEN material.

How are PLLA implantable medical devices manufacture?

There are different production technologies for an implantable medical device: machining by chip removal (turning or milling), hot moulding, cold moulding, investment casting and many others.

An injection molding machine is required to make components with the PLLA polymer.

All implantable medical devices produced with any technology, including those in PLLA, require processes and process controls that are very different from industrial products.

For this reason, despite the large number of highly specialize companies manufacturing plastic components, only a few have the know-how, technologies and environments, suitable for the production of implantable medical devices.

As mentioned above, the machines used are plastic injection molding machines.

What is injection molding?

During this process, the polymeric material is sucked through a feeding system inside the plasticizing cylinder where a screw is located. The screw creates a friction by rotating and translating by means of hydraulic pistons. This friction, combined with the thermal contribution of some resistances, brings the material to the melting temperature.

Once the necessary viscosity has been reached, the material is injected into the mold (injection phase) passing through appropriate channels and filling the cavity, which represents the piece in negative.

Once the cavity has been filled, the maintenance phase begins, during which the polymer is kept under pressure, in order to compensate with other material the increase in density, the decrease in temperature and the solidification, which occur during the cooling of the piece.

After the cooling phase, whose duration depends on the type of polymer and the geometry of the product, the moulded piece is extracted by means of a press and the next cycle begins.

The moulding and the detachment from the sprue carried out by specialized operators, is carried out in an ISO7 controlled atmosphere environment. After detachment, the packaging of the components takes place.

At this point the components are ready for the surgery room.