Moulds for Medical Parts

Plastics are used a lot in medical parts. Injection molding is used widely as the method of their manufacture.
Therefore, it can also be said that a substantial part of the medical parts are being manufactured using molds.

Some typical medical parts made of plastic are the following.

1. Cylinders of syringes (injection tube): PP, PE
2. Pistons of syringes: PP
3. Pipette tips: PP
4. Catheters: PVC, PC
5. Blood collection test tubes: PC
6. Petri dishes for culture growth: PS

The plastic materials used for medical parts, depending on the application, can only be used if they satisfy the quality standards of laws related to pharmaceuticals and drugs or of regulations of related governmental ministries or organizations. The use of these materials is limited to plastics that can withstand sterilization processing by irradiation with ultraviolet rays or gamma rays, and to plastics that have passed the clinical approval tests such as blood coagulation reactions or allergy reactions, etc., on human body.
In addition, since these devices are basically of a disposable type, the materials should also be those that do not destroy the environment when disposed off by burning.

It is recommended that molds are manufactured using materials that are resistant to rusting. Therefore, structures preventing corrosion of the cavity and core are used widely such as using stainless steel or ion plating coatings, hard chromium electroplating, etc.
Further, valve gate molds are also used widely for molded products that are manufactured in very large quantities.

Since molded products become quality defects if burrs are present on the periphery of the molded product, precision products are used for the positioning guides on the movable side and fixed side, and also various techniques are adopted for preventing abnormal wear of core pins of various structures.

In order to stabilize the quality of molded products, since it is necessary to design delicately even the mechanisms for the temperature control of cavities and cores, it is necessary to pay attention to the structures of the cooling circuits and heat pipes. The cooling structure on the interior of the core becomes extremely important in the case of the tubes of syringes, etc.

In terms of quality control, removing any dirt or soot adhered to the surfaces of molds is also a very important point. Setting up of gas vents and forced suction structures are also being used.

This article was composed from notes taken from posts in misumi-techcentral.com