Ties Per Inch | Perforation Types

Perforations

Perforations are used on a laser form when a portion of the form needs to be detached from the rest. Perforations are classified by bursting strength and type. The bursting strength is referred to as "ties per inch" or TPI. The type of perforations are horizontal or vertical, which can be full or partial.

Ties Per Inch

The tie or tab is the part of the perforation where the paper does not get cut, but remains intact to "tie" the paper together. The ties alternate with cut areas to form the perforation. The tied areas of the perforation are usually narrower than the cut areas to allow for easier detachment of the sections separated by the perforation. The proper TPI to use is generally determined by the type of form and the function of the perforation on that form. For laser forms, a micro perforation is most commonly used for the following reasons:

• It consists of 50 to 72 TPI which are very small in width allowing the paper to burst or detach easily without noticeable residue remaining on the sheet.
• The micro perforation provides a smooth flat perforation which allows the form to lay very flat. A flat perforation allows the sheet to run through the laser printer without jamming.

There are times when a micro perforations does not work well on a laser form. If the form is on a heavy weight stock, it is hard to control the cutting depth of the perforation. Using a heavy weight stock may result in a perforation that does not properly detach. You should us a perforation with less TPI when using heavy weight stock. If you are unsure of which TPI to use, you should discuss your options with your supplier.

Perforation Types:
 

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