Finishing (manufacturing technology)
In forging technology , finishing means the refinement of a roughly forged material by lightly striking a hammer, usually on an auxiliary hammer ( finishing hammer ) to achieve the most perfect surface possible.
In manufacturing technology, finishing follows roughing with the aim of achieving the required surface quality as well as dimensional and shape accuracy. In connection with the accuracy requirements for the workpiece, one also speaks of fine or very fine finishing . As a rule, finishing is used for finishing or finishing, but it can also be required for a subsequent manufacturing step, such as polishing or grinding . The improvements are made by reducing the process forces and using more accurate machines and tools.
If the workpiece is brought into its final shape without removing any material, it is referred to as a straightening process , especially when it comes to bending or pressing .
In the case of machining processes , the process forces arise primarily from the cutting force, which is reduced by means of a low cutting depth and feed rates as well as a significantly increased cutting speed. This prevents elastic deformations on the machine, tool and workpiece. Furthermore, the wear of the tool is lower, which results in higher dimensional accuracy. In the case of non-contact processes such as spark erosion or electrochemical removal , the energy used for material removal is reduced, analogous to the cutting force.
In addition to reducing the process force, lower feed speeds in processes with rotary cutting movements such as milling or turning result in closer spacing of the cutting engagements. The roughness depth caused directly by the cutting edge ( shape deviation 3rd order) decreases, but the feed or the cutting depth cannot be selected to be smaller than the cutting edge radius, as otherwise the material is not cut off, but only compressed and pressed off.
Spatial contours require machining that is as close as possible to the target contour. When finishing, the guided tool must therefore follow the contour in closely spaced paths. The end shape is therefore never smooth, but rather resembles a staircase shape corresponding to the tool. The exceptions here are imaging processes such as ultrasonic vibratory lapping or spark erosion sinking , but here too the tools can initially or always be affected by defects from tool manufacture.
In addition to the machine-based finishing process, there is also finishing with hand tools. In the simplest case, this is the use of a finishing file (a file with a higher cut, i.e. a small distance between the file teeth) or grinding with hand-held tools such as sandpaper.