GB2175517A

GB2175517A - Vertical spindle jig grinder

Info

Publication number: GB2175517A
Application number: GB08513287A
Authority: GB
Inventors: Judel Solomonovich Reibakh
Original assignee: EXNII METALLOREZH STANKOV
Current assignee: EXNII METALLOREZH STANKOV
Priority date: 1985-05-23
Filing date: 1985-05-28
Publication date: 1986-12-03
Also published as: GB8513287D0; GB2175517B

Abstract

A numerically controlled vertical spindle jig grinder comprises a bed 1 with a column 5 having vertical ways 6, and a compound table 2 carrying a workpiece 3 and a wheel dresser 4. The compound table 2 is traversable along the axes X and Y. A slide 7 having a pivot shaft 9 is traversable on the ways 6 of the column 5 along the Z axis. The slide 7 has circular ways 8 on which a cradle 10 is installed for traversing along a circular coordinate axis B with respect to the pivot shaft 9. The cradle 10 carries a turret 11 indexable about axis 12 and having at least two wheelheads 13 provided with wheel spindles 15 rotatable about the longitudinal axis 14 of the wheelhead 13, the spindles carrying spherical abrasive tools 16 of different diameters. The grinder also has a numeric control system 23 which is electrically connected to movable assemblies of the grinder. <IMAGE>

Description

SPECIFICATION Improvements in or relating to spindle jig grinders This invention relates to apparatuses for abrasive machining, such as numerically controlled (NC) vertical spindle jig grinders. Such apparatuses may be used in machining three-dimensional surfaces in mechanical engineering, eg in machining workpieces such as three-dimensional dies, moulds and templates.

The number of parts having critical intricately shaped and precise surfaces continuously grows in modern mechanical engineering because of the rising speeds of machines and intensification of manufacturing processes. This results in a wider use of automatic machine employing three-dimensional cams, templates, dies, moulds, fashioned shafts, globoids and conoids. Since these parts function under high loads, their critical surfaces should preferably be heat treated with subsequent grinding and high-precision forming to ensure wear resistance.

Known in the art is an NC vertical spindle jig grinder (cf. USSER Inventor's Certificate No 656813, Cl. B 24 B 17110, 1979), comprising a bed, a compound table transversable on the bed along X and Y axes, and a column rigidly held to the bed and carrying a wheel dresseer and vertical ways supporting a wheelhead.

It should be noted that this prior art grinder is only designed for machining workpieces with their surfaces defined by planar curves. This grinder cannot be used for machining three-dimensional workpieces with double-curvature surfaces.

According to one aspect of the invention, there is provided a grinder as defined in the appended claim 1.

According to another apsect of the invention, there is provided a grinder as defined in the appended claim 2.

It is thus possible to provide an NC vertical spindle jig grinder which ensures form trueing of spherical abrasive tools.

It is also possible to provide an NC vertical spindle jig grinder which helps obtain a required position of the generant of a spherical abrasive tool or its part contacting the workpiece surface to optimize the cutting capacity of the tool.

It is further possible to provide an NC vertical spindle jig grinder which renders it possible to match the curvature of a spherical abrasive tool with a local curvature of the workpiece surface so as to improve the tool efficiency and ensure more effective use of the grinding tool.

In order to reduce the effect of load of various assemblies of the grinder on its accuracy, the cradle preferably carries two rows of taper rollers interposed between end faces of the circular slide ways, the rollers being in contact with the end faces of the circular slide ways along generants which are substantially perpendicular to the layshaft axis.

It is thus possible to automate machining of dies, blades, propellers, templates and similar workpieces having intricate three-dimensional configuration of surfaces in mechanical engineering, and thus to dispense with large numbers of gauge makers working under harmful conditions of abrasive dust and using portable grinders that cannot ensure the desired accurace of machining.

The invention will be further described, by way of example, with reference to the accompanying drawings, in which; Figure 1 shows a schematic structural view of a vertical spindle jig grinder constituting a preferred embodiment of the invention; and Figure 2 is a sectional view taken along line Il-Il in Figure 1.

An NC (numerical control) vertical spindle jig grinder comprises a bed 1 (Figure 1) with a compound table 2 tranversable along X and Y axes and carrying a workpiece 3 and a wheel dresser 4 with a diamond grinding tool 4', and a column 5 having vertical ways. A slide 7 is transversable along a Z axis on the vertical ways 6 of the column 5 and comprises circular ways 8 and a lay-shaft 9. A cradle 10 is installed on the circular coordinate axis B with respect to the axis of the lay-shaft 9. The cradel 10 carries a turret 11 indexable about its horizontal axis 12 together with at least two wheelheads 13, the longitudinal axes 14 of the wheel heads being perpendicular to the horizontal axis 12 of the turret 11.Each of the wheelheads 13 is provided with a wheel spindle 15, whose axis includes a preset angle a with the axis 14 of the wheelhead 13, the spindle being rotatable about the axis 14 of the wheelhead 13 and carrying a spherical or part spherical abrasive tool 16 of an arbitrary diameter whose geometrical center 17 of rotation lies on a geometrical axis 18 of rotation of the cradle 10. The geometrical axis 18 of rotation of the cradle 10 is the axis of the lay shaft 9.

The wheel dresser 4 is located on the compound table 2 and the apex of the diamond grinding tool 4' of the wheel dresser 4 is situated in a vertical plane passing through the axis 18 of the lay-shaft 9 when the spherical abrasive tool is being formtrued and dressed.

The cradle 10 has arms 19 carrying two rows of taper rollers 20 in such a manner that generants 21 of the rollers 20 contacting the end faces of the circular guides 8 are perpendicular to the axis 18 of the lay-shaft 9.

The cradle 10 with the shaft 9 is journalled in the slide 7 by means of bearing 22.

The numerical control of the grinder may be effected by any appropriate known CNC (computer numerical control) system which solves problems arising in machining three-dimensional surfaces such as the Fanuc System 6M - Model F (cf FANUC (Japan), N6MF- 0.1, 1984.3). If necessary, the software package FART-DIE.II may also be used (cf FANUCM PE-02, 1983,11) for making choice of machining flowchart and strategy, corrections taking into account wear of spherical abrasive tools upon dressing and recalculation of three-dimensional equidistant surfaces.

The NC vertical spindle jig grinder according to the invention functions in the following manner.

For machining the workpiece 3 (Figure 1), the table 2, slide 7 and cradle 10 are traversed along axes X, Y, Z, B, respectively, following instructions received from an NC system 23.

The spherical abrasive tool 16 is profiled as a sphere or parts thereof by the wheel dresser 4, which is provided eg with the diamond grinding tool 4', during rotation of the cradle 10 and spindle 15.

Depending on the specific three-dimensional configuration of the workpiece and curvature of its individual portions, abrasive tools 16 having different diameters of spherical surface are brought in contact with the workpiece 3. For that purpose, the turret 11 is indexed in a manner known per se and is stopped. For achieving the desired contact between the spherical abrasive tool 16 and the workpiece 3, and to ensure more convenient access to individual portions of the intricately shaped surface of the workpiece 3, each of the spindles 15 can take various positions in space when rotated about the axis 14 of the wheelhead 13.

Therefore, a required positioning of a generant of the spherical abrasive tool 16 (or a part thereof), which is in contact with the workpiece is ensured so as to optimize the cutting capacity of the tool.

Machining of the workpiece 3 is performed by the line-by-line method during the continuous movement of the grinder assemblies along axes X, Y and B. In this case, the Z coordinate is used for the line-by-line feed. Other combinations of movement of the grinder assemblies are also possible where the Y coordinate may be used for the lineby-line feed.

Each of the tools 16 is fed for dressing towards the wheel dresser 4 by traversing the slide 7 along the Z axis.

When it is necessary to dress a straight profile of the spherical abrasive tool, the cradle 10 is rotated through the angle a in the direction away from the spindle 15 so that the axis of the spindle is set verticaily. The grinding wheel is dressed by traversing the slide 7 relative to the wheel dresser 4 which has additional horizontally arranged diamond grinding tool (not shown in the drawings).

Intermediate positions of the axis of the spindle 15 enable the spherical abrasive tool 16 to be profiled as cones and hyperbqloids.

The vertical arrangement of the grinder and functions of its basic assemblies call for the heavy cradle carrying the turret 11 to be installed without any free play relative to the slide 7. At the same time, the cradle 10 should traverse relative to the slide 7 without sliding contact friction.

For that purpose, the cradle 10 with its shaft 9 may be journal led in the slide 7, eg by means of the rolling contact bearings 22 (Figure 2), and the bending moment caused by weight G of the cradle 10 and turret 11 is taken-up by the two rows of taper rollers 20 which contact the end faces of the circular guides 8 and slide 7 without any clearance.

Depending on a specific three-dimensional configuration of the workpiece and curvature of its individual portions, abrasive tools 16 of different diameters of the spherical surface are brought in contact with the workpiece. Matching the curvature of the spherical abrasive tool with a local curvature of the workpiece makes it possible to use wach spherical abrasive tool 16 in the most effective manner.

Therefore, the NC vertical spindle jig grinder renders it possible to machine three-deminsioinal surfaces of workpieces, including those having alternating curvature, and improves the tool machining efficiency.

Claims

1. A spindle jig grinder, comprising a table for carrying a workpiece and movable in a first plane, a wheel dresser carried by the table, and a grinder assembly movable towards and away from the plane, the grinder assembly comprising a cradle which is pivotable about an axis which is substantially perpendicular to the direction of movement of the grinder assembly, a wheelhead carried by the cradle and rotatable about an axis substantially parallel to the direction of movement of the grinder assembly, a wheel spindle carried by the wheelhead and rotatable about an axis which is inclined to the axis of rotation of the wheelhead, and a spherical or part-spherical abrasive tool carried by the wheel spindle with its centre on the axis to pivoting of the cradle, the table being movable in the first plane so as to locate the wheel dresser in a second plane which is perpendicular to the first plane and passes through the axis of pivoting of the cradle.

2. An NC vertical spindle jig grinder comprising a bed having a column which is rigidly held thereto and has vertical ways, a compound table traversable along X and Y axes and arranged to carry the workpiece, a wheel dresser, and an NC system electrically connected to moveable assemblies of the grinder, wherein a slider is traversable upon the vertical column ways along a z axis, the slide having circular ways and a lay-shaft 9, a cradle being installed on the circular ways and capable of traversing along a circular coordinate axis with respect to the lay-shaft axis, the cradle carrying a turret indexable about its horizontal axis together with at least two wheelheads, the longitudinal axes of the wheelheads being substantially perpendicular to the horizontal axis of the turret, each of the wheelheads being provided with a wheel spindle whose axis makes a preset angle with the wheelhead axis, the spindle being rotatable about the wheel head longitudinal axis and carrying a spherical abrasive tool of an arbitrary diameter, a geometrical center of the spherical abrasive tool lying on the cradle geometrical axis of rotation, the wheel dresser being located on the compound table at a point which is situated on the line of intersection of a vertical plane passing through the lay-shaft axis with the horizontal surface of the compound table whent he spherical abrasive tool is being form-trued and dressed.

3. A vertical spindle jig grinder as claimed in claim 2, wherein the cradle carries two rows of taper rollers interposed between end faces of the slide circular ways, the rollers being in contact with the end faces of the circular ways along generants which are substantially perpendicular to the layshaft axis.

4. An NC vertical spindle jig grinder substantially as hereinabove described with reference to and as shown in the accompanying drawings.