Finishing

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The term fine machining refers to manufacturing processes - mainly machining - that are used to produce workpieces of high quality. The quality can affect both the surface quality and the dimensional accuracy, i.e. H. refer to the permissible dimensional deviation from the nominal dimension.

The goal of fine machining almost inevitably means that it is often the last production step in a multi-stage production. This can be a process identical to the previous step under different conditions or a completely different process.

The term itself is neither defined in terms of the possible methods nor from the point of view of the achievable results, nor is it described in a standard. This would also make little sense, since technical progress always opens up new possibilities that make special fine machining superfluous. For example, it used to be necessary in most cases to finish machining a very precise cylindrical workpiece to be produced by turning by grinding , lapping or honing . However, advances in machine tool and cutting material technology mean that the desired result can now be achieved with the lathe.

Requirements for fine machining processes

The demands on the machining process are very different depending on the intended use of the workpiece. B .:

  • High proportion of material or contact area (proportion of load-bearing surfaces in the total surface) for sliding and sealing surfaces
  • small roughness to increase the material content and the wear and corrosion resistance. A roughness depth of Rz = 1… 3 µm is necessary because of the required oil adhesion for sliding surfaces.
  • high dimensional, form and positional accuracy. With fine machining processes, tolerance grade IT 4 or better can be achieved. Here, too, it is crucial which type of accuracy is required for the application.
  • no damage to the workpiece edge zone due to pressure or heat during processing
  • economical production - while lapping can be done on the simplest machines, eroding processes often have long machine running times and - in the case of die sinking erosion - usually very high tool costs, which can make them very expensive.

Procedure