Editing Perforation (section)

==Processes==
===Pins and needles===
[[Image:Controlcard-crop.jpg|thumb|left|"Volcanic" perforations made with a needle punch]]
[[Image:Orientatiepaalperforatorpinnetjes Silva 433.JPG|thumb|right|A needle punch used in [[orienteering]]]]

Rotary pinned perforation rollers are precision tools that can be used to perforate a wide variety of materials. The pins or needles can be used cold or heated. Cold perforation tools include needle punches.

There are a handful of manufacturers that specialize in hot and cold needle perforation tooling and equipment. In materials that have [[Elasticity (physics)|elasticity]] this can result in a "volcano" hole that is preferred in many applications.

Pinned rollers can be made from a variety of materials, including [[plastic]], [[steel]], and [[aluminum]].

In more [[brittle]] films, cold perforation can cause slitting rather than creating a round hole, which can jeopardize the material's integrity under pressure.  The solution to this is often heating the pin; i.e. hot pin perforation. Hot perforation melts a hole in the material, causing a reinforced ring around the hole. Hot needle perforation also assists when high density pin patterns are utilized, as the heat aids the perforation of the material.

===Die and punch===
Die and punch sets can be used for thicker materials or materials that require large holes; this process is the most common for [[metalworking]]. The workpiece is [[Shearing (manufacturing)|sheared]] by pressing (either by machine or hand tool) the [[Punch (tool)|punch]] through the workpiece and into the [[die (manufacturing)|die]]. The middle section of the workpiece is scrap; commonly known as the [[chad (paper)|chad]] in paper and similar materials. The punch and die are shaped to produce the desired shaped hole. The clearance (the distance between the outside circumference of the punch and the inner circumference of the die) must be properly maintained to ensure a clean cut. [[Burr (metal)|Burr]]s are produced on the side of the workpiece that is against the die.<ref name="todd"/>

Common applications are fruit and vegetable bags, [[hole punch]]ing and [[ticket punch]]ing.

===Laser perforation===
[[Laser cutting]] can place many precise holes in a web. Laser perforations look similar in many respects to hot needle perforations. However, laser systems are expensive. The big advantage of laser perforation is the consistency of the hole size, compared to mechanical perforation. This is very important in [[Modified atmosphere|modified atmosphere packaging]] for fresh produce. The laser perforation is often carried out on [[roll slitting]] machines (slitter rewinder) as the printed material is slit down to the finished roll size.