Metal toothed plates

Metal toothed plates (MZPs) are made of steel components that have been stamped to a thickness of 1-2 mm. On the working side of each MZP are sharp metal teeth that vary in length and shape, each serving a specific functional purpose (see photo 1). MZP offers a high strength of wood fastening because of its teeth, shape, inclination angle, and placement.

MZP – application of plates, their types and characteristics, installation

MZP are designed to be installed on wood structures, such as roofing. MZPs are best suited for building structures with the following spans because of their ideal thickness, shape, and tooth count:

  • up to 12 m – rafter trusses, interfloor trusses;
  • up to 30 m – arched and frame structures;
  • up to 10 m – beams.

You should be aware that industrial settings are typically used for MZP designs. This is particularly valid for structures like:

  • Wall panels;
  • floor beams;
  • truss covering.

This can be explained by the ease with which structural elements can be fixed in production to their exact design positions, enabling robots to operate with high precision (±10mm) and quality. MZP is used to illustrate structural elements in Photo 2.

The following tools must be used at the business in order to precisely fix structural elements:

  • hanging press bracket with conductor;
  • mobile press;
  • stationary press.

Catalyzed cold-rolled steel is used to make metal toothed plates. The zinc coating on the steel is 14–17 microns thick.

Both private and commercial housing construction use metal toothed components. Additionally, MZP makes it feasible to erect wooden formwork and produce packaging containers.

The primary MSP types are separated based on their thickness, which also dictates the plate’s width and range of application with respect to various beam sections. The majority of producers create MZP in three thicknesses (1.2, 1 and 2 mm, tab. 1). Their primary parameters are listed below.

Different minimum wage types

For joining parts with a maximum thickness of 38 mm

For joining parts with a maximum thickness of 60 mm

Any length, starting at 50 mm and increasing by 25 mm (at the customer’s request)

Extra plate dimensions

  • width: 45; 54; 63; 81; 108 mm;
  • length: 45; 70; 95; 120; 145; 170; 195 mm (for each additional width plate)

Certain MZPs are suitable for joining wooden beams with a minimum thickness of 70 mm. Depending on thickness, the following plates are available from manufacturers:

A) with a 1.2 mm thickness:

  • length – 160…340 mm;
  • width – 80…140 mm;
  • teeth length – 14.8 mm.

B) with a 2.0 mm thickness:

  • length 160…400 mm;
  • width 80…200 mm;
  • teeth length – 23.5 mm.

The minimum wage may vary depending on the nation of manufacture:

  • according to the material of manufacture;
  • by shape and number of teeth;
  • plate thickness.

The teeth in MZP elements are frequently positioned to make sure that the wood functions for crushing rather than chipping. Teeth density can reach 70 pieces/dm2.

The following are used to produce minimum wages:

  • unidirectional arrangement of teeth (Russia);
  • bidirectional arrangement of teeth (Poland, Finland, Germany).

With unidirectional teeth, the most typical design for MZP plates is a small shift in the relationship between adjacent longitudinal rows. The primary drawback of plates with unidirectional teeth is the varying strength and deformability of the teeth, the values of which are contingent upon the angle formed by the wood fibers’ direction relative to the axis of force and the plate’s axis. Nonetheless, the MZP has been improved, and now the teeth are oriented differently, parallel to the square’s diagonals and sides (forming a "herringbone").

The following kinds (systems) of minimum wages are most prevalent in the construction industry:

  • Ganges Neil (Europe);
  • MZP-1.0; MZP-1,2 and MZP-2 (CIS countries);
  • Arpad (Hungary).

One characteristic of the Arpad system is the way the teeth are arranged in rows facing each other at varying angles. This arrangement makes the teeth jam when pressed into wood, strengthening the connection overall.

The most efficient MZP Gang-Neil and Arpad varieties are taken into account; nevertheless, top manufacturers continuously enhance the design of metal-toothed plates each year.

The following tables list the essential elements of the minimum wage: 2, 3.

Principal attributes of the MZP connections

State of connection that is stressed

Typical angles α, β, and γ

Design load-bearing capacity of type-plate connections

R (MPa) the connection’s working area

Bite bending at an angle to the direction of the fibers and the acting force β, crushing wood

Rр (kN/m) width of the plate’s working section

Plate tension at the angle formed by the plates’ longitudinal axis and the acting force, represented by α

Length of the plate’s cut section, measured in Rav (kN/m).

Shear of the plate at the angle formed by the plate’s longitudinal axis and the shear force direction γ

MZP’s intended load-bearing capacity

Kind of state of stress

Load-bearing capacity R (kg/cm) at angle α (degrees) in the design

Installation of MZP plates

Two plates, one on each side, are required for a single, straightforward connection. High-strength connections require the use of a specialized press that maintains the precise positioning of the plates and guarantees the necessary speed of pressing the teeth into the wood.

As previously mentioned, the workshop installs the minimum wage and assembles the major components (structures), after which the completed structure is delivered to the construction site (see photo 3). The arrangement of the plates should be such that the tooth rows run parallel to the wood’s grain in the component that absorbs the greatest forces.

The main advantages of the minimum wage

  1. Possibility of arrangement of connecting elements in one plane.
  2. Reduces overall wood consumption.
  3. Relatively low weight of the entire structure.
  4. The ability to install wooden structures without the use of special lifting equipment.
  5. Relatively low labor intensity of installation work. Eliminates work on installing grooves and tenons in elements.
  6. Reducing financial costs when transporting and installing wooden structures.
  7. High durability of MZP elements and structures using them.
  8. The connections are relatively high strength compared to glue and nail connections.
  9. The optimal number of people for the construction of wooden structures with minimum wage is 4…5 people.
  10. Possibility of constructing wooden structures of any complexity.
  11. There is software that allows you to speed up the process of designing wooden structures, eliminating the possibility of making gross errors in calculating the strength of connections and selecting the desired section of composite beams.

Commonly used in timber construction, metal toothed plates provide a dependable and effective way to join wood pieces together. Without the use of screws or nails, these plates with their pointed metal teeth are pressed into the wood to form sturdy connections. They are a popular option for many construction projects, from assembling frames to building trusses, because of their strength and simplicity. Comprehending their advantages and uses will enable you to make well-informed choices for your building requirements.

Main disadvantages of minimum wage

  1. For the manufacture of wooden structures with minimum wages, a perfectly flat platform is required.
  2. The need for special press equipment that provides the maximum and required joint strength. Manual installation of the MZP (press-fitting) is not recommended, as it significantly reduces the strength of the connection. The technology for constructing wooden structures using MZP is not widespread in private house construction, since it requires the use of special equipment and is almost always carried out in an industrial workshop.
  3. Since the Gang-Nail system MZPs are mainly used, one of the main disadvantages is the different operation of the plate and its teeth in different directions.
  4. When the load acts on the plate along the main axis, its flexural strength of the spikes will be minimal.
  5. The weak point of the plate teeth is at the base, where the minimum value of bending rigidity.

Video on the topic

Testing the connection of the nail plate

rupture of the connection reinforced with nail plates

Press for MZP (metal toothed plates)

Machine for pressing MZP (metal toothed) or nail plates

nail plates

MZP (metal toothed plates)

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