Fortuna-werke Maschinenfabrik Gmbh

Other

Horst J Wedeniwski

An apparatus and a method are disclosed for numerically controlled grinding of cams of a camshaft. The cams have a convex circular base section and a convex circular tip section with concave transitional sections interconnecting same. The concave transitional sections have a minimum radius of curvature. The cam is first ground with a first grinding wheel of a radius much bigger than the minimum radius of curvature, however, the cam material is not entirely removed during this first grinding step at the location of the concave sections, thus leaving there a zone of unground cam material. In a second grinding step, the cam is ground with a second grinding wheel of a radius being smaller than the minimum radius of curvature.

Process and device for numerically controlled grinding of cams of a

A method serves for cylindrical surface grinding of workpieces. A grinding wheel engages a workpiece which rotates in the opposite direction and is fed at a given feeding speed parallel to the axis of the workpiece. The grinding wheel rotates about an axis which is inclined at an angle relative to the axis of the workpiece. In order to achieve workpiece surfaces of low roughness at high machining speeds, in particular surfaces without spiral-shaped surface grooves, one first determines from the given surface roughness, by empirical means, a contact ratio serving as an auxiliary value whereafter the axial length of the first surface is determined and adjusted using a formula. The method is used within a range of values where workpiece diameters of 5 to 250 mm are encountered, the grinding wheel rotates at a speed of 100 to 300 m/s, the workpiece rotates at a circumferential speed of 65 to 200 m/s and the speed of the axial feed is between 150 to 2000 mm/min.

Method for cylindrical surface grinding of workspaces

A method serves for dressing grinding wheels (10) whose surface (16) comprises an embedding compound for CBN crystals. A rotating dressing roll (11) is moved along the surface (16) of the grinding wheel (10). In order to produce sharp-edged points at the CBN grains (20) during the dressing process, and obtain sufficiently large clear chip spaces in the embedding compound, the dressing roll (11) is moved over the said surface (16) at least twice, the first movement being carried out at a first, high rate of feed (v.sub.3) so that the dressing crystals of the said dressing roll (11) deflect the said CBN grains (20) elastically while setting back the embedding compound, whereas the second movement is carried out at a second, lower rate of feed (v.sub.4) so that the said dressing crystals break up the points of the said CBN grains (20).

Method for dressing grinding wheels

A process is applied for grinding cams of a camshaft (12) by means of a numerically controlled camshaft grinding machine (10). The camshaft (12) is arranged in a workpiece mounting (11) rotatably at preset angular velocity (.omega.) in predetermined angle steps about its longitudinal axis. A grinding wheel slide (17) with a grinding wheel (18) is infeedable in an axis (20) vertical to the longitudinal axis in preset steps. A grinding wheel (18) is selected as to its condition for machining as a function of the geometry, the material and the required surface condition of the camshaft (12) and cams (30), and the infeed of the grinding wheel (18) is set. In order to achieve a minimum grinding time while taking into account various process-related restrictions, a maximum possible infeed for a minimum grinding time is determined using the maximum relative metal removal rate and the preset cam geometry, and--if necessary taking into account restrictions with regard to the chip cavity repletion conditions and the grain load--the maximum infeed for grinding the camshaft (12) is set (FIG. 1).

Process for grinding cams of a camshaft

A dressing roll comprises a revolving circumferential surface, in particular two conical circumferential surfaces (12, 13) intersecting each other along an outer circumferential line (14). The circumferential surface is garnished with diamonds. In order to ensure that the diamond needles attack a grinding wheel to be dressed over a two-dimensional surface and to avoid the production of spiral-shaped dressing grooves in the grinding wheel surface, the diamonds take the form of diamond needles (15, 16) which project obliquely from the circumferential surface (12, 13) and whose free ends (17, 18) overlap each other in the circumferential direction (FIG. 1).

Dressing roll and method for producing the same

A method serves for grinding two or more cams of a camshaft. Initially the camshaft is chucked in a mounting position between a driver of a work headstock seated to rotate about a first axis (C axis), and a footstock. Then the camshaft is rotated in a defined rotary angle/time relationship. A rotating grinding wheel is advanced in the direction of a second axis (X axis) extending perpendicularly to the said first axis (C axis), the movement of the rotating grinding wheel being directed towards a first cam to be ground. The rotary angle and length of travel (x) of the grinding wheel are adjusted in response to the polar coordinates of a nominal contour of the cam, supplied by a numerical control, while the grinding wheel is in engagement with the cam. Any deviation from a nominal process value is measured. The pre-determined length of travel is corrected by a correcting value (.DELTA.x) corresponding to the weighted deviation. In order to compensate all influence that may lead to errors, with the least possible cost input, the dimensions of the contour of the cam ground first are measured. Any deviations between the values determined by measuring and the nominal values of the dimensions of the contour are determined, and the length of travel (x) is weighted with a correction factor. Finally, a second and subsequent cams are ground the same mounting condition.

Method of grinding two or more cams of a camshaft

A method serves for working, by metal-cutting processes, a surface of profiles having a non-circular contour, in particular for grinding camshafts. Starting out from a blank contour (30-1-32), material is removed from the surface to give the profile a desire contour (30a, 31a, 32a) by moving the processing tool and the profile relative to each other in such a manner that the portion of the processing tool which is at any time in engagement with the surface is moved along the contour in a path-controlled manner, while on the other hand the tool is advanced in feed-controlled manner by the surface distance between the blank contour (30,31,32) and the desired contour (30a,31a,32a). In order to reduce the processing time and to improve the processing quality, the active portion is removed initially in feed-controlled operation from a first point (40) on the surface of the blank contour (30,31,32) to a second point (42) of the desired amount (30a,31a,32a), and then moved in path-controlled operation along the desired contour (30a,31a,32a).

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Remshalden-Grunbach, Germany

Horst J Wedeniwski