When sheet metal is processed or thermally treated, stresses and distortions occur. Straightening machines compensate for these deviations and bring the sheet into the desired shape. A distinction is made between straightening machines with hydraulic cylinders for workpiece processing and roll straightening machines for straightening coils. The higher the number of straightening rolls, the smaller the roll diameter and the stiffer the machine construction is, the better the straightening results. Modern straightening machines can be bought as used without hesitation. At Surplex you will easily find a product with the desired year of manufacture and available from a location in Europe.
Straightening machines are precision work tools that are predominantly used for the final production stages of heat-treated workpieces and welded constructions. Using straightening, the misalignments and distortions that have been created through the use of thermal energy, can be corrected.
A straightening machine can straighten constructions and workpieces to the precision level of a millimetre. Straightening machines used for heat-treated workpieces are often placed in the production line near the gluing oven and the thermal coating machines (e.g. galvanising machines, chrome plating machines). Straightening machines for welded workpieces are predominantly used for automobile and plant construction. During industrial mass production, they are used during the last step, before lacquering and assembly. In the maintenance area, straightening machines are primarily used for automotive engineering and for the restoration of accidental damage.
There are two types of straightening machines. Those used for heat-treated workpieces, work with a number of assembled, hydraulic press cylinders. The workpiece is put into these cylinders and shaped into the desired dimensions, using a programmed forming process. Working with a straightening machine requires a certain amount of experience. The handling of testing equipment is necessary for controlling the quality of the results. For the production of small and medium sized products (e.g. sheet metal angles or fittings) a combination of equipment needs to be used. The process strip material is used in a single process to work on the desired products. These machines combine the use of a winch, punch and straightening machine to create one manufacturing station. Semi-skilled workers can be employed to operate these machines. Qualified experts are only necessary for the installation, renovation and maintenance of these machines. Mass production can occur either through manual or automatic loading.
Straightening machines for welded constructions are made out of an adjustable frame, to which one or more cylinder liners are hinged. The workpiece is then mounted and manually formed into the desired shape. For the operation of this machine, qualified and highly-experienced experts are needed. Steel, and especially welded steel, cannot be arbitrarily bent back and forth. Fatigue and stress cracks can happen all too easily. Therefore, in order to achieve good results with the least amount of use of manual force, it is necessary to have a lot of experience. After the straightening, it is recommended to do basic quality control. Magnetic processes such as an ultra sound or x-ray could be used, as well as manual processes such as the die penetration test and visual inspection.
Well-known manufacturers of straightening machines are UNGERER and SCHUBERT. The company OSTERBERG has specialised in combined manufacturing machines. The most well-known manufacturers of straightening jigs are SDMR, CELETTE, BLACKHAWK and DOZER.