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Hole Pattern - Conventional and Uniform
The other important aspect in perforating besides the shape and the size of the hole is the hole pattern. There are countless numbers of perforating patterns possible with many types of hole, including round, square, hexagonal, rectangular, triangular and oblong.
The most common patterns used in perforated sheet metal are straight line and staggered patterns. In a straight line pattern, the hole arrangement can be determined by two parameters: Vertical and horizontal direction. To create a square pattern, both directions should have equal distances. If the distance in the vertical direction is not the same as in the horizontal direction, the perforated pattern will be called a rectangular pattern. Unfortunately, compared to a staggered pattern, this straight line pattern is not as strong as the staggered pattern due to the nature of the layout.
This illustration above is a common square perforated pattern layout which is in a group of straight line perforated patterns.
In a staggered pattern, the hole arrangement is determined by the angle produced by two holes in a staggered layout. The most common staggered hole pattern is in 45 or 60 degree angles. Among all the types of pattern, either in straight line or staggered, the 60 degree angle pattern is the most popular pattern arrangement. This 60 degree staggered pattern is the only pattern that still retains the most strength of material while maintaining the largest possible open area on the perforated sheet. The reason for this is that the centre distance between each hole from one to another is in equal space. Thus, this gives an efficiently uniform structure on the perforated sheet.
The 60 degree angle and 45 degree angle pattern in the group of staggered layout
60 degree angle pattern with hexagonal hole type
Besides all these conventional and standard patterns, there are also many uniform perforated patterns that have been used in industries. One of these is a circular pattern layout. This type of pattern is good for use in round perimeter sheet metal. This pattern is also good for use in creating a dimple jacket for the bottom of a cylindrical tank. By its nature, the layout of a circular perforated pattern is also appealing as a decorative component in architectural buildings. A circular pattern is more likely to be fabricated using a turret punch press or a profile cutting machine.
The other non-standard pattern layout, which is also a non-uniform pattern, is the spiral pattern. This pattern is generated using a mathematical formula (i.e. spiral gauss formula) to create a striking, eye-catching pattern, that can be a decorative component combined with a substantial purpose such as ventilation or sun screen.
The first is a circular perforated pattern and the second is a spiral pattern
The hole pattern layout is not only limited to single hole shapes; they can also be combined with other shape to create even more appealing perforated pattern designs. Some of the common pattern combinations, according to IPA handbook (www.iperf.org), are a Round Cane type pattern, an Octagonal Cane pattern and a Grecian pattern. Another pattern is one that can be seen in many perforated walkways, where there is a small drain hole between the dimple holes.
Round Cane type (left) and Octagonal Cane type (right)
Grecian perforated pattern