Perforated plates are plates that have a large number of identically sized holes which have the same geometrical form and which are placed in evenly staggered patterns, diagonally staggered patterns or straight rows (square pitch). Many different types of material are hole punched: primarily steel and aluminium but brass, copper, tin, nickel or titanium are also turned into perforated plates; plastic, cardboard or wood fibreboard can also be found running under the perforated plate manufacturer’s hole punch press.
The plates are perforated in a number of ways: the quickest and most economical method is to make the holes with a wide press. In this method, the plate is worked on across its entire width in one pass. One or more consecutive rows of punches perforate the plate at a fast speed as it is being transported stepwise through the machine – in the case of modern machines, it can be over 400 strokes per minute. The wide press process only makes economic sense in the case of perforation types in high demand because manufacturing a tool with a large number of punches is very expensive.
Perforated plates are also produced with a strip feed press. On such a machine, an inexpensive tool outfitted with a few or, in rare cases, only one punch is used. The plate is perforated strip by strip. This means, of course, that the production process takes more time.
The perforating tools do not produce a completely smooth hole: on the side of the plate that the punch exits, a very small rim remains with the result that the back side is somewhat rough. After the perforating has been done, the plate must be flattened because the punching process deforms it somewhat.
These days, small amounts of the evenly perforated plates (from various materials) as well as irregularly perforated materials are primarily manufactured on computer-controlled machines. Depending on the material to be perforated and the production amounts involved, milling, cutter plotting, water-jet cutting and laser cutting are all available as possible methods.
The last mentioned processes have acquired ever more importance not only for the production of “perforated materials” – they are meanwhile used almost exclusively for the made-to-order production of smaller amounts of two and three dimensional objects: films are cut with the cutter plotter, facades for model making or letters are milled, metal and plastic sheets and plates are worked on with water-jets or lasers.
Applications: Sieves, presses, dryers and filters are the typical uses for perforated plates; speaker panels and washing machines are examples of their everyday use.
Perforated plates are, however, being used more and more in the realms of decoration, design and other creative endeavours. Some examples of use include such things as facing for construction pieces, in furniture construction and lampshade production all the way to everyday utility items. Aluminium and steel plates with fine perforations are often found being used in architectural model making but can also be used for jewellery and handicrafts work as well.
Interesting effects can be created by mounting one perforated plate out of line over another one with the same perforations. A moiré effect is created which can best be appreciated when light is shining through the plates.
|Product display board made from perforated plate||Two fine perforated plates are especially good for producing a moiré effect when slightly misaligned.|
Types, grades, designations
The most used hole shapes are square and round; long slots, however, both round and rectangular are used more and more often. The palette of potential perforation types is a wide one. Hexagon holes, rhombus holes, cross shaped holes and keyholes are also produced.
The dimensions of square and round holes are defined by the hole width hw (the length of a side of a square hole or the diameter of a round hole).
In the case of rectangular long slot perforations, the measurement refers to the hole length hl (the longer side of the rectangular hole). The hole separation distance is given as the hole spacing hs or the width of the partition bar pw.
In the case of long slot perforations there are two measurements of the separation distance:
• separation distance hs1 is measured crosswise to the longitudinal axis
• separation distance hs2 is measured parallel to the longitudinal axis
The pitch defines the positioning of the perforations on a plate. The most frequently encountered positioning is the 60° staggered round perforation. In this example, the perforations are staggered in such a way that a line drawn from the middle point of three neighbouring holes will form an isosceles triangle (all sides equal). Round perforations are also made in diagonal pitch (i.e. 45° staggered) and in straight rows. Plates with square perforations are available in straight, diagonal and staggered pitch as well.
The open area or, better, "the relatively free hole area a0" is defined as the percentage of open space which is based on the size of one perforation in relation to half of the area of the adjacent partitions. This data is really only important for knowing the amount of material which will pass through a perforated plate being used as a sieve in a technological process. For creative uses, this data does play a role when trying to judge the amount of light or sound that will be allowed to pass through the plate.
Perforated plates are labelled in the following way:
• SqS stands for a square perforation in a straight row (called square pitch)
• RSp stands for a round perforation with a staggered pitch
• The dimensions of the perforations are given as hw/hs (hole width/hole spacing).
A perforated plate with the label RSp 5.0/8.0 has round holes with 5.0 mm diameters and a spacing of 8.0 mm. In the case of square long slot perforated plates 2.4/3.0 – 1.2/1.8, the first pair of numbers stands for the hole length and the lengthwise spacing; the second pair stands for the same measurements but in the transverse (crosswise) direction.
The hexagon hole is a special perforation: in the given dimensions 1.5/2.2, the first one stands for the hole width measured horizontally, the second stands for the spacing.
Treatment: Perforated plates can be processed much like standard metal sheets. Thin plates with thicknesses up to 0.5 mm can be cut with a blade or scissors, thicker ones must be cut with a metal snips or, alternatively, with hydraulic or electric cutting tools. Thicker aluminium perforated plates can also be cut with a jigsaw or a circular saw (non-ferrous metal blade). The plates gain stability when they are folded over. If the surface is to be treated with paint or varnish, it must be degreased to make sure that the paint will stick. Important: As a result of the production process, whole perforated plates always come with one unperforated border (solid metal) which is between 3 and 20 mm wide. Because the pre-cut sizes that we have for sale are cut from whole sheets, we cannot guarantee that when ordering one of these it will not have such a border. If this is not satisfactory, you can always order custom cut sizes to your specifications.
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