The open area relative to the closed surface area is referred to as the perforation degree. This is a percentage between 0 and 100%. The percentage can be determined using building principles, such as acoustics, shading or light transmittance, and from aesthetic points of view.

Experience has taught us that in perforated facades a percentage of 25 to 40% usually results in the best effect. The facade appears more closed when smaller openings are used, and with larger openings the structure will become visible. It’s also important to take into account the colour and amount of light that falls in the background.

The calculation of the perforation degree is (at a triangle stitch with round holes):

R = hole diameter
T = stitch
Perforation degree = [R2 x 90,69] / [T2]

The starting point for perforated panels of 2 to 3 mm is a minimum material position (‘c’) of 5 mm – the gap between two holes. You can reduce this, but there will be a higher chance of producing cavities and dishing of the panels. Pitch can be determined by adding the largest hole diameter to the minimum material spacing.

T design / photo perforation = [Rmax + c] Rmax = largest hole diameter
T = stitch

It is possible to perforate with round holes, squares, slots and special shapes. This can be done in different stitch patterns: triangle stitch, rectangular stitch (with sizes r1 and r2) or a skipping stitch. Typically, a (photo) perforation pattern is chosen for a triangle pitch (30-60 degree angle), as this usually gives the most desirable image, with the holes closest to each other. However, a rectangular pitch is also possible.

The number of holes per m2 is determined by the pitch. By increasing the pitch, the number of holes is reduced exponentially. The number of holes per m2 helps determine the cost of panel production.

An important starting point for the hole diameters used – referred to as R – is that the minimum hole diameter is equal to the plate thickness, therefore a smaller hole is not possible. The largest standard hole diameter is approximately 60 mm. Larger hole sizes are possible, but this requires laser cutting instead of punching, which is more expensive.

The starting point for a 2 or 3 mm set panel is a blind edge of approximately 10 mm. This is the distance from the side of the hole to the side of the panel. With a non-set panel, this edge distance may be smaller, at up to about 5 mm. When using different hole sizes in one panel, you should use a larger blind edge for small holes if you want the rows of holes to pass through properly.

You can deviate from this blind edge, but this creates a risk that the holes will be deformed into ovals instead of rounds. Material and material thicknesses also have a bearing on this. Also, the panel should be less perforated in the corner of the set. We would need to look at the possibilities specific to your project.

It is possible to make MD Designperforation of the following materials:

• Aluminum
• Corten steel
• Steel

Thicknesses range from 1.5 to 4 mm, partly depending on the type of MD Designperforation. The choice of material also determines the weight and strength of the panels, as well as the desired appearance.

The following surface treatments are available for MD Designperforation:

• Thermal galvanizing (steel)
• Powder coating (steel, aluminum)
• Anodizing (aluminum)

The choice of surface treatment depends on the desired appearance (color, shine etc) and the material type (for example corrosion protection in steel). The method of detailing also affects the surface treatment you will need.

The tolerance on MD Designperforation panels depends on your project. For example, will the panels be set to cassettes, or will they be flat? Or will the panels be secured by an MD Verti mounting with screws, or an MD Resto mounting, with panels being hung blindly? Tolerances are inevitable, and it is necessary to take this into account in advance during the detailing.

Given the many factors that play a part in determining tolerances, we recommend asking about tolerances specific to your project.

For panel dimensions it is advisable to take into account standard coil widths of 1000, 1250 and 1500 mm. This is the cut-out size, so remember to factor in the set aside for the cassette panels. The recommended panel length is 4000 mm due to the capacity and dimensions of the machining apparatus.