Cold needle perforation can cause a "volcanic cone" shaped structure in the material, which can be beneficial for a number of applications. Cold perforation tools include needle punches. There are very few manufacturers of this precision made equipment in the world. One of which is Stewarts of America in the USA .
Hot needle perforation melts the material being perforated, and creates a reinforcing ring around the hole. This can also be beneficial in many applications, as the ring assists in keeping the integrity of the material. There are a handful of manufacturers that specialize in hot and cold needle perforation tooling and equipment.
For microperforation, pinned rollers can be made from a variety of materials to include plastic, steel, aluminum, or other materials. Pinned sleeves can be slid onto a central shaft, so that pin patterns may be interchanged at will.
Die and punch sets can be used for thicker materials, or materials that require large gauge holes. The material is sheared by the sharp edges of the punch and die, and the chad is removed. One will see punched perforations in fruit produce bags. Other examples include hole punching and ticket punching.
Laser perforation can place many precise holes in a web. Laser perforations look similar in many respects to hot needle perforations. However, laser systems can be expensive to purchase and maintain. Many use an array of mirrors to direct the beam of light.
Perforation frequently refers to the practice of creating a long series of holes so that paper can be torn more easily along a given line, a "perforation line". Since the creation of perforation devices in the 1840s and 1850s, it has seen use in several areas. Postage stamps are one common application of this, where small round holes are cut in lines to create individual pieces (see postage stamp separation). Perforations on stamps are rather large, on the order of a millimeter, in comparison other perforated materials often have smaller holes.
It is common for notebooks and legal pads to have perforations making it easier to tear out individual pages. Film stock is perforated to allow it to be moved precise distances at a time continuously. Screwcaps on glass or plastic bottles are sealed with a ring at the bottom of the cap attached by perforation. Twisting the cap has the effect of rupturing the perforation and indicating that the original seal has been broken.
In today's cases, perforation is used in ways to separate loose leaf (or even a form of graph paper from a ringed binder). A fine perforation next to the rings allows the page to be separated from the book with no confetti.
Thoracic esophageal perforations. (Original Article).(a study finds a needs for aggressive surgery to treat thoracic esophageal perforations)
Feb 01, 2003; Background: Recognition of the importance of early diagnosis and aggressive, definitive surgical intervention has brought about a...