DE2164958A1 - Method of polishing hard objects - Google Patents

Description

l'atcsiianwalt PHN. 539 * 4 «

Anmeid ": fcj. V. Philips' Gloeilampenfahdeken File Ne. PHN- 5394 Boss / WJM. Application dated 29 Dec * 1971

"Method of polishing hard objects".

The invention relates to a method for

Polishing of hard objects, with a relatively thin surface on a hard, dimensionally stable surface Layer of a soft material is provided on which polishing grains are spread, after which the objects are polished will. When polishing hard objects such as reproduction and Recording heads for recorders, it is of great size It is important that these meet the strict requirements in terms of shape accuracy and surface quality after processing.

In order to achieve a high level of dimensional accuracy, it known »the polishing grains, for example diamond or 'carborundum grains, directly on a hard surface from

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for example to provide cast iron. Although this results in a high dimensional accuracy, but the surface quality is bad.

A good surface quality can be achieved by placing the polishing grains on a soft surface can be applied from wood, for example. Here, however, the shape accuracy is poor.

It is also known to have a hard surface to cover with a lead or tin layer and to provide the polishing grains on it. This gives better shape accuracy than one made entirely of soft material existing subsoil and a better surface quality than with a substrate made entirely of hard material.

A disadvantage of the known lead or tin layer is that the dimensional stability is not very accurate The objects to be produced are not sufficient, but the surface quality also meets the strict requirements cannot suffice, which is presumably due to the detachment from Polishing grains from their bedding is due. "To nevertheless to get the best possible surface quality, 'is made with very fine polishing grains (0-3 / u) in a very dense cast edited. This means that the work pressure must be considerable, which is partly due to the hydrodynamic pressure build-up that occurs at a very small distance occurs between the head piece and the polishing gauge in the liquid and the polishing force counteracts the shape accuracy

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impaired. Another disadvantage is that the lead layer wears out in such a way after a relatively short time is that a new teaching must be instituted. j. The purpose of the experience according to the invention is that

eliminate mentioned disadvantages ziji and is characterized by that the thin layer of a soft material through a plastic film with a thickness of at most 10 times the grain size, which is loose lies on the ground and is held on the ground by negative pressure.

Surprisingly, it has been shown that

by using such a very thin plastic film a high dimensional accuracy and a good surface quality can be achieved. You can also use coarser polishing grains can be worked, which among other things has the consequence that the already mentioned hydrodynamic pressure build-up no longer has a disruptive effect between the workpiece and the film. As a result, the working pressure could surprisingly be lower which benefits the accuracy of the shape, while the machining time is lower by factors than that known procedures.

The plastic film lies loosely on the surface, where it is only held in place by the negative pressure exerted in the ground through narrow channels. Because of the loose position the film can, if necessary, give way to the side without being destroyed. There is a big advantage in that the foils are easily exchanged

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can.

In the known process, it is customary to work with a very high degree of occupation of the grains, where $ 50 of the surface of the polishing substrate through the projected surface of the polishing grains is occupied.

In a favorable embodiment of the invention Procedure, the degree of occupation is such that the projected surface area of all polishing grains is smaller is than $ 10 of the surface of the plastic sheet.

Furthermore, according to the invention, it is advantageous to use a plastic film in which the intruder the polishing grain is about 10 times larger than that of the workpiece. This means that the cutting depth of the Grains in the workpiece is about 10 times smaller than the depth to which the grains penetrated the plastic are. The relatively soft plastic film is reduced consequently the influence of the tolerances in the grain size and holds the grains firmly due to their elasticity.

With the method according to the invention it is

possible, objects with greater dimensional accuracy, better Surface quality, shorter machining times and lower tool costs than with the previously known Polishing procedure.

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Claims (2)

PHN. 539 ^. - 5 - PATENTANS PR UC HE » { 1. J Method for polishing hard objects, whereby a relatively thin rail of a soft material is provided on a hard, dimensionally stable substrate, on which polishing grains are distributed, after which the objects are polished, characterized in that the thin layer of a soft material is replaced by a Plastic film is formed with a thickness of at most 10 χ of the grain size, which lies loosely on the substrate and is held on the substrate by negative pressure. 2. The method according to claim 1, characterized in that that the degree of occupation of the grains is such that the projected surface area of all grains is less than $ 10 of the plastic film surface in question. 3 · Method according to claim 1 or 2, characterized characterized in that a film is used as the plastic film in which the penetration of the polishing grains is approximately 10 times greater than that of the workpiece. 209834/0619