GB2113584A

GB2113584A - Tool for producing outer profiles

Info

Publication number: GB2113584A
Application number: GB08301870A
Authority: GB
Inventors: Manfred Lorenz
Original assignee: KAPP AND CO WERKZEUGMASCHINENF; KAPP AND CO WERKZEUGMASCHINENFABRIK
Current assignee: KAPP AND CO WERKZEUGMASCHINENF; KAPP AND CO WERKZEUGMASCHINENFABRIK
Priority date: 1982-01-28
Filing date: 1983-01-24
Publication date: 1983-08-10
Also published as: IT8319288A0; CH658619A5; IT1161003B; DD207171A5; GB8301870D0; DE3202695A1; JPS58132418A; FR2521048A1

Abstract

A tool for producing straight or inclined outer profiles, preferably external gear toothing, comprises single or multiple spiral threads. The total surface of the spiral threads of a steel base element 1 being provided with a uniform layer of a super-hard material 2, in particular cubic crystalline boron nitride or diamond. This layer of superhard material can be applied by electrodeposition in known manner to the base element, which is preferably hardened before coating by electrodeposition. <IMAGE>

Description

SPECIFICATION Tool for producing outer profiles The invention relates to a tool for producing straight or inclined outer profiles, preferably external gear toothing. This external gear toothing can be of either involute or noninvolute form. In order to produce such outer profiles, the tool possesses single or multiple spiral threads, of which the surface is formed by a plurality of grinding crystals.

In producing outer profiles, in particular external gear toothing, a distinction must be made between soft machining and hard machining. In soft machining, the outer profile is produced by a hob on a hobbing machine.

Beyond a certain material hardness, the use of such hobs is severely limited. In such a case, hard machining is carried out using generation grinding, in which the grinding operation can be either a continuous generation grinding operation or generation grinding by the indexing method. The movement pattern in continuous generation grinding on a generation grinding machine corresponds to the movement pattern in hobbing. A ceramic grinding wheel with a reference profile in the form of a toothed rack is used as the tool. The pattern of movement in generation grinding by the indexing method, likewise carried out on a generation grinding machine, corresponds to generation planing. Either trapezoidal double-cone grinding wheels or straight flank disc-shaped grinding wheels of ceramic material are used as the tool.Finally, straight or inclined outer profiles can also be produced by profile grinding, for example on a tooth profile grinding machine. In this case, the movement pattern corresponds to that of profile cutting with side-milling cutters The hobs used for soft machining effect an interrupted cut by virtue of their flutes. Because of this, periodic stressing of the work piece, the tool and the machine tool arises, leading to vibrations. These vibrations on the one hand limit the capacity of the hobbing machine, and on the other hand have an unfavourable effect on the life of the tool.

The particular drawback of the generation grinding used for hard machining is that the ceramic grinding tools must be frequently dressed, either on or outside the grinding machine. Because of the danger of fracture of the ceramic grinding tools, their maximum rotational speed is limited. At higher peripheral speeds, the machinig area of the machine must be enclosed at great expense, in order to prevent accidents due to shattering tools. In the case of generation grinding by the indexing method, tools comprising trapezoidal double-cone grinding wheels or disc-shaped grinding wheels are used, of which area of contact with the work piece is relatively small. In addition to the time lost due to the necessary indexing operations, the actual grinding operation also takes a relatively long time.The use of spiral ceramic grinding tools in the case of generation grinding is linked to relativeiy large grinding spiral diameters, for production capacity reasons. As this in many cases is not possible because of the shape of the work piece, the use of the method is considerably limited.

The object of the invention is to provide a tool for the production of straight or inclined involute and non-involute outer profiles, preferably external gear toothing, which is suitable both for soft machining and for hard machining, and which obviates the drawbacks of known tools, and which further makes accident-free soft and hard machining on one and the same machine possible with a production capacity which is considerably increased with respect to the known methods.

This object is attained with the aid of a tool provided with single or multiple spiral threads, wherein according to the invention the total surface of the spiral threads of a steel base element is provided with a uniform layer of a super-hard material, in particular cubic crystalline boron nitride or diamond being used as the super-hard material.

According to a further characteristic of the invention, the layer of super-hard material is applied to the base element by electro-deposition in known manner. Preferably, the base element of steel manufacture is hardened before the coating by electrodeposition.

With the tool accordng to the invention, both soft machining operations, which up to the present time have been carried out with hobs, and hard machining operations can be carried out for forming outer profiles on the same machine tool. In contrast to the known hobbing method, the tool according to the invention has the advantage that the grinding crystals of super-hard material give a continuous cut, which because of the considerably increased rotational speed, allowable by virtue of the high strength of the material according to the invention, not only results in a considerably higher cutting capacity, but also prevents vibrations arising. At the same time, high-strength materials can also be machined by the tool according to the invention, so that the machining of highly heat-treated, highalloy, hard steels gives no difficulty.By virtue of the, in comparison with ceramic spirals, considerably increased strength of the tool according to the invention, which comprises a steel base element and has its total surface coated with super-hard material, the rotational speed limits deriving from the tool strength, and which had previously to be observed during hard machining, now no longer apply.

The circumferential speed of the tool according to the invention is limited only by the maximum rotational speed of the tool and work piece as governed by the machine con struction and control system. Circumferential speeds up to 100 m per second can be strived for, so that very high removal capacities can be attained by the tool according to the invention, even in the case of hard ma chining.

With the tool according to the invention, both soft machining and hard machining become considerably more economical for producing outer profiles. In comparison with known hobs, the tool according to the invention is considerably cheaper to manufacture, particularly because if the super-hard materal wears, the steel base element can again be coated with a layer of super-hard materal. In the case of coating by electrodeposition, it is only necessary to remove the remainder of the used layer, and coat the basic element with a new layer of super-hard material. Compared with grinding tools of ceramic material, the tool according to the invention has the great advantage that the frequent dressing operations are no longer necessary, and that because of their high resistance to wear, tools of small diameter can also be used.The tools according to the invention result in a considerable shortening of the grinding time, and because of their cool grinding also enable deep grinding operations to be carried out without the structure of the work pieces being influenced by heat.

The tool according to the invention can consequently be used both instead of expensive hobs, which require frequent resharpening, and instead of ceramic grinding tools, in which case the dressing devices and timeconsuming dressing operations are both dispensed with, in addition to which the danger of accidents in the case of such ceramic tools is avoided. With the tool according to the invention, high-speed deep grinding is possible using an economically favourable method, by virtue of the fact that on the one hand tools which are very economical to manufacture, possess a long life and have a high removal capacity are used, and on the other hand special dressing devices for the tool, and the enclosing of the machining area of the machine are dispensed with.

One embodiment of the tool according to the invention is illustrated on the drawing, in which: Figure 1 is a perspective view of a spiral tool for manufacturing external toothing, and Figure 2 shows part of a plan view of the tool illustrated in Fig. 1, Figure 3 being a normal section through one spiral thread.

The tool for manufacturing straight or inclined outer profiles comprises a steel base element 1, which in the embodiment is spiralshaped with a single spiral threads. The base element can be hardened after its manufacture.

The base element 1 is provided with a uniform layer 2 of a super-hard material over the total surface of the spiral threads. Cubic crystalline boron nitride or diamond can be used in particular as the super-hard material.

The layer 2 is applied preferably by electrodeposition, so that a coating on the base element 1 is attained which is uniformly thick, and of which the thickness can be exactly predetermined. The thickness of the layer can be from 0.050 mm to 0.300 mm depending on the size of the crystals of super-hard material.

When using the tool, particularly for manufacturing a gear wheel 3 provided with outer toothing as shown in Fig. 1, the surface of the base element 1 provided with the layer 2 acts by removing chips, according to engagement conditions, so that a high removal capacity is attained, all the more so as the peripheral speed of the rotating tool can be chosen at a correspondingly high value because of its high strength, and correspondingly high feed speeds can be assocated therewith.

By using a super-hard material as the coating for the base element 1, resharpening or dressing operations are dispensed with. If after lengthy use of the tool either the whole or part of the layer 2 becomes worn to an extent exceeding its allowable range of tolerance, it is completely removed and the base element 1 is again provided by electrodeposition with a layer 2 of super-hard material.

Claims

1. A tool for producing straight or inclined outer profiles, preferably external gear toothing, comprising single or multiple spiral threads, of which the surface is formed by a plurality of grinding crystals, characterised in that the total surface of the spiral threads of a steel base element (1) is provided with a uniform layer (2) of a super-hard material, in particular cubic crystalline boron nitride or diamond.

2. A tool as claimed in claim 1, characterised in that the layer (2) of super-hard material is applied to the base element (1) by electrodeposition in known manner.

3. A tool as claimed in claim 1 or 2, characterised in that the base element (1) of steel manufacture is hardened before the coating by electrodeposition.

4. A tool as claimed in claim 1, 2 or 3, characterised by being used both for the soft machining of steel and also for hard machining.

5. A tool as claimed in at least one of claims 1 to 4, characterised in that the layer (2) applied by electrodeposition has a uniform thickness of 0.050 mm to 0.300 mm, depending upon the size of the crystals of superhard material.

6. A profile forming tool comprising a steel member having a threaded outer surface which is coated with a hard crystalline ma terial.

7. A profile forming tool substantially as herein described with reference to the accompanying drawings.