Microperforation

Microperforation refers to the placement of holes or apatures in a material. Microperforation can be inserted in a web with needles, pins, laser, high pressure air, open flame or high pressure water jet.

Packaging films are often microperforated in order for the packaged contents to breathe. Other applications include medical to allow wounds to breathe, sound and vapor barriers and other applications. The most simple and cost effective method of microperforation is with pinned rotary tooling. There are very few manufacturers of this precision tooling in the world. One example would be Stewarts of America. [http:///www.stewartsofamerica.com]

These high precision tools can be integrated into an existing line of machinery, or built as a stand alone unit. Pins and needles can create two types of microperforations, hot and cold. Cold perforation simply refers to a cold pin that penetrates a material. In materials that have elasticity, this can result in a "volcano" hole that is preferred in many applications. In more brittle films, cold perforation can cause slitting rather than creating a round hole, which can jeopardize the materials integrity under pressure. The solution to this issue is often Hot needle perforation. Hot needle perforation melts a hole in the material, causing a reinforced ring around the hole. This ring of molten material aids in the integral strength of the final product. Pinned perforation rollers can be manufactured to house up to 1250 pins per square inch, with hole sizes down to 70 micrometres or so. Pinned sleeves can be interchanged to achieve different perforations. Pinned rollers or pinned plates can be also used to microperforate materials.

Laser perforation is a MUCH more expensive version of perforation. Laser perforation simply burns a hole in the material being processed.The big advantage of laser perforation is the consistency of the holesize, compared to mechanical perforation. This is very important in Modified Atmosphere Packaging for Fresh Produce. The company Perfotec in The Netherlands is specialised in this technology and developed a laser perforation system with online camera inspection and Automatic Oxygen Transmission Rate Control.