Terminology & Measurement Methods
Aperture width (labeled w in the below diagram) is the distance between two adjacent warp or weft wires, measured in the projected plane at the mid positions.
Warp: All wires running lengthwise of the cloth as woven.
Weft: All wires running across the cloth as woven.
Wire diameter (d) is the width of the wires in the woven cloth. (The wire diameter may be altered slightly during the weaving process.)
Pitch (p) is the distance between the midpoints of two adjacent wires. Represents the sum of the aperture width (w) and wire diameter (d).
Material: The user specifies the choice of material with respect to:
A.) The final application and requirements of the wire cloth, including resistance to environmental corrosion, suitability for food products, etc.
B.) Any further processing, including suitability for shaping, welding and surface treatment, etc. Materials should be designated in accordance with appropriate standards or, if none exist, according to commercial specifications.
The number of apertures per unit length (n) is the number of apertures counted in a row one behind the other for a given unit length. The unit length may be 1cm, 1dm, 1in, or any other unit of length; however, the number of apertures with a length of 25.4mm is designated as “Mesh”.
Mesh = number of apertures per linear inch = 25.4mm : pn/cm = number of apertures per cm = 10 : pn/cm2 = number of apertures per cm2 = (10 : p)2
Open screening area (A°) is the percentage of the area of all apertures in the total screening surface, or the ratio of the square of the nominal aperture width (w) to the square of the nominal pitch (p), rounded to a full percentage value.
A° = 100.(w : p)2
Type of weave is the way in which the warp and weft wires cross each other.
Weight (G) of the steel wire cloth screen section in kg per m2 :
The actual value can be up to 3 % lower.
The wire diameter can be calculated using the following equation:
Woven wire cloth must be labeled with the following information:
- The name and the trademark of the manufacturer
- The material of the wire
- The nominal aperture width (w)
- The nominal wire diameter (d)
- The length and width of the roll or strip, or the size and number of pieces
- The weight (mass), if required
If the cloth roll consists of several roll pieces, the length of each piece must be indicated.
Woven wire cloth in strips or pieces must be labeled on the outer packing. The length and weight of each strip (coil) must be specified, subject to agreement.
Roll lengths: A standard roll is 25m or 30.5m long. Half rolls are 12.5m or 15m long. The length of rolls may vary by plus or minus 10 percent. The delivered length is the one invoiced. Partial lengths: A wire cloth roll may consist of a maximum of three roll pieces. The minimum length of a roll piece is 2.5m.
Cloth width: For full rolls or roll pieces, the width of the cloth must not be less than the nominal width, but may exceed it by 2%.
Strips and cut-to-size pieces: For strips, the width must be specified. When ordering quantities less than a standard roll, the length of individual strips may be reduced accordingly. For cut-to-size pieces, the sides, lengths, angles, and radii must be specified.
Types of Apertures
Zero Aperture “Filter Cloth”
Determination of the Wire Diameter
The post-weaving wire diameter will be determined using one of the following procedures:
- Measuring wires that have been loosened from the
woven wire cloth by using a micrometer screw.
- Measuring the wires in the cloth, provided there is
sufficient space for the instrument.
Due to the heavy deformation that occurs during the weaving, the preprocessed tolerance of the wire cannot be determined in the woven wire cloth; however, the nominal wire diameter can be calculated using the empirical weight formula.
Determination of Aperture Width
First, as part of a simplified measuring method, the number of pitches (p) in a given length (L) is determined. The given length is then divided by the number of pitches to calculate the average pitch. Subtracting the wire diameter (d) from the average pitch provides the aperture width (w). In order to determine the mean value of the aperture widths, it is important to measure as many pitches as possible to obtain a representative sample. When measuring aperture widths between 1mm and 16mm, ten pitches have to be checked. Smaller widths, such as 0.1mm or less, must be checked within twenty pitches.
Counting glass for measuring aperture widths less than 1mm in a row with determined length.
Micrometer screw used to determine wire diameter.
Vernier caliper for measuring aperture widths of more than 4mm. It can also be used for aperture widths of greater than 10mm.
Measuring row with determined length for aperture widths of 1mm to 16mm.