Nut former machines are very useful machine tools for the fastener manufacturing industry. A nut is a type of fastener with a threaded hole. Nuts are nearly always used in combination with the corresponding bolt to tie several components together. Both partners are held together by a combination of the friction of their threads, a slight stretching of the bolt, and the pinching of the parts to be held together. Nut former machines use the cold heading process to make nuts.
Cold forging is a cold-forming process that essentially involves applying a force with a punch to the end of a metal blank contained in a die. The force must exceed the elastic limit of the metal to cause the plastic to flow. The nut forming process can be considered as a forging operation without the use of heat. The header involves embossing, and is mostly done in combination with other cold forming operations, such as scale, punching, trim, thread rolling, blank rolling, and so on.
Nuts are usually produced by a nut former machine that uses either a cold or hot forming process. The choice of one or the other procedure depends on the one hand on the size and the other on the required quantities. However, in modern joining technology, most fasteners are made by cold forming. In this procedure, the connector is formed, typically in a multi-step process, by pressure forging, cold extrusion, and reduction or a combination of these procedures. The term cold or cold forming was coined for this type of production. This procedure is usually used for large volumes as it is the most rational from an economic point of view method. The selection of the appropriate nut former machine depends on the size of the fastener and the degree of formation. The greater the degree of molding, the more molding steps are required. Sharp cut edges or thin profiles are detrimental to cold working and lead to increased tool wear.
The selection and quality of the input material play a decisive role in the quality of the end product and are almost as important as the quality of the not forming machine itself. Screw manufacturers usually get wire coiled in rolls that often weigh more than 1,000 kg. The wire is usually phosphate treated to allow excellent wire processing and to minimize tool wear. During the development phase, the designer of the screw or fastener tries to harmonize the advantages and disadvantages of the various materials with the requirements specified for the fastener. Due to the materials, there are variations between non-alloy and alloy steels, as well as corrosion-resistant steels. For example, if increased strengths are needed, it is important to subject the parts to a heat treatment process after pressing, to be able to directly influence the mechanical properties.
The cold header of a nut former machine differs significantly from processing where the material is cut to form the finished part. There is no scrap in the header, except for the minimal amount that can occur during secondary operations such as trimming. The header is not intended to override machining, however. There are many cases - highly complex parts, larger parts, or low production requirements - where it is more economical for the machine. Some materials cannot be targeted. The die head and cold forming now enable more economical and faster production of many fasteners and other parts that previously could only be made by machining.
This production method is primarily used for the production of large diameter nuts with a nut forming machine for a nut size of roughly M27 or higher. Besides, parts that can not be created by cold forming due to very small volumes or to a very high degree of formation are possible. With this process, the input material is heated to the forging temperature in whole or in part. And complex geometries or very high forming grades can be realized with this heating. The rough surface structure is a typical feature of a hot-formed component. The advantage of a hot nut former machine is that it allows the production of complex geometries, is suitable for production runs, and the above-mentioned is suitable for large diameter nuts and long fasteners.
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