Ties Per Inch | Perforation
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
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.
- Horizontal Perforations run across the form left to right.
- There are limitations on the number and position of horizontal
perforations that are allowed.
- Partial perforations do not run across the full width of the form
and will have the same limitations as the full horizontal perforations.
- Vertical perforations run the depth of the form.
- The number and position of the vertical perforations are usually
- Partial vertical perforations do not run the entire depth of the
- The number and position of partial vertical perforations are limited.
Consult your supplier for these limitations.
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