A perforation is a small hole in a thin material or web. There is usually more than one perforation in an organized fashion, where all of the holes are called a perforation. The process of creating perforations is called perforating, which involves puncturing the work piece with a tool.
Perforations are usually used to allow easy separation of two sections of the material, such as allowing paper to be torn easily along the line. Packaging with perforations in paperboard or plastic film is easy for consumers to open. Other purposes include filtrating fluids, sound deadening, allowing light or fluids to pass through, and to create an aesthetic design.
Perforation in print is most commonly associated with stamps, tickets, cheque books, coupons and tear off forms for replying to postal requests but perforation is also used in Metal Work, Food Packaging, Medical Supplies and general packaging. There are many types of perforation methods available including Punch & Die, Pins and Needles and Laser Perforation for high end fast and accurate perforating production. Most common within the print sector is traditional rotary or linear perforation but recently there has been a surge of interest in Punch Perforation using a slide in Perforation Die containing a perforation comb. We use both methods throughout our Obeli machinery range as this enables us to produce perforations in both directions and on a much wider variety of paper and card stocks.
Dies and punch sets can be used for thicker materials or materials that require larger holes, particularly our Layflat Photo Punch uses a heavy duty version of this Die & Punch method as the holes on that application are a relatively large perforation line. The Die & Punch method works by pressing, either by hand or electronically, the material as it passes through the die tool, the perforation comb is forced through the material being processed and punctures the matching design on to the material. The punched out material is waste or scrap which is often referred to as Chad within the print industry.
Just as you find with any perforating device there are many different patterns you can punch, in perforation these are referred to as TPi or Teeth Per Inch. The higher the TPi the perforation tool indicates the lighter the stock that the tool can cope with, as a result thicker papers and card should be perforated with a lower TPi blade. Our blades range from 8 through to 48 TPi utilising the Die & Punch method, this allows us to perforate papers from 60gsm through to 300 gsm.
The advantage of the Die & Punch perforating method is the fact that the tool can be programmed or manually activated many times in a single pass. This means that one sheet being processed can be perforated many times down or along the sheet without the need for extra tooling.
The most common method of perforation utilises a traditional wheel and anvil mechanism which punches the material as it is passed through the tooling. Commonly the top wheel is the perforation blade and the bottom is the anvil or receiver, different manufacturers use this setup in a number of ways. The basic method uses a Perforation Blade that is only sharpened on one side to a point, similar to the shape of a wedge, this is then placed alongside the receiving anvil, also shaped like a wedge, which results in a perforation being applied as the material passes through. The issue with this basic setup is the fact that the material is often nipped or crushed as it is perforated which results in a raised area around the perforation, sheets with this raise are then difficult to process through other machinery such as a digital press.
The far better method of Rotary Perforation uses a much higher quality blade which is sharpened to a pin point, just like a knife or pin head. As this tool is pin sharp at the tip it does not need an anvil to create the perforation line, instead it utilises a low cost Nylon Receiver which enables the blade to lightly penetrate the surface of the nylon and thus punches completely through the material being processed. As there is no pressure on the material at the point of perforation you get a far more consistent and truly flat perforation using this method. All the Obeli machines use the higher quality method of perforation.
The only disadvantage of this method is the fact that each perforation line needed requires an individual tool to create the perforation. This can become costly is you have a high number of perforations to complete.
Numbering is the function of applying consecutive numbers or unique identifiers to a selection of documents or materials. Invented by Edwin G Bates in 1891 as a hand operated numbering stamp which auto rotated the numbers after each impression. Primarily used at the time by legal and medical companies to label and identify different files or documents within a cabinet it was quickly taken up by the print sector for the production of numbered tickets, sequenced booklets and for basic numbering of documents for the legal and medical business sectors.
Today numbering machines are not as common place as they once were within the print market due to the emergence of digital PDF files and the fact that many of the latest Digital Print Engines can number automatically as the printed materials are produced. However, there is still a requirement for numbering in certain market sectors which does not suit production through a digital press. Quite often numbered items require accurate and reliable perforation as the numbers are often matched across the perforation or identify a certain person or ticket, as a result Obeli has introduced a new Numbering Machine to the market that can be partnered to our Swift Creasing and Perforating range for high speed accurate perforation and numbering applications.