DE102007033767B4 - Method and device for processing workpiece surfaces - Google Patents

Abstract

Process for high-precision machining of both non-circular and rotationally symmetrical inner and outer contours on rotating workpieces (7) with the following process steps:
- Creating a desired workpiece contour by forging and / or soft machining with an allowance (A) for hard machining,
- hardening of the workpiece (7)
- Hard machining of the workpiece (7) with a defined cutting edge (17) and subsequent grinding process in one setting, characterized in that, in order to achieve a maximum feed rate, the cutting edge (17) is moved relative to the workpiece (7) in such a way that the feed movement (21) is parallel or runs at small angles to the edge of the cutting edge (17) and that the contour deviations of the workpiece (7) caused by the cutting edge shape are compensated for by an infeed movement.

Description

The invention relates to a method and a device for high-precision machining of hardened workpieces with both non-circular and rotationally symmetrical inner and outer contours. In the industrial series production of such workpieces, for example in the manufacture of seats for bearings or sealing rings, the hardened workpiece is subjected to a hard turning treatment and then ground. From the DE 199 20 467 A1 a grinding machine with a hard turning device is known. In order to be able to use the advantages of the grinding machine structure for hard turning, a holder for a turning tool or a tool turret is provided on the grinding machine bed. On this machine, the workpiece can be machined in one clamping by hard turning and grinding. Furthermore, manufacturing processes were developed for the machining of crankshafts, for example, with the aim of completely eliminating grinding machining. The EP 1 030 755 B1 shows a process in which finishing is carried out after machining with a specific cutting edge. For this purpose, when machining with a defined cutting edge, the degree of permissible deviation from predetermined dimensional and surface tolerances must be observed. In order to guarantee the desired production quality, tool wear must be closely monitored and each individual workpiece checked. The DE 10 2004 026 675 B3 relates to a method for producing rotationally symmetrical surfaces. A tool with a cutting edge, the shape of which corresponds to the cutting edge of a cylindrical milling cutter, is used. The cutting edge is moved in an arc-shaped feed movement, the main cutting movement being caused by the rotation of the workpiece.

The object of the invention is to provide a method that enables quick and inexpensive machining of hardened workpieces with high surface quality and dimensional accuracy. It is also an object of the invention to provide an apparatus for carrying out the method.

This object is achieved by a method according to claim 1 and a machine tool according to claim 5. Advantageous developments of the invention are the subject of the subclaims.

An advantageous aspect of the invention consists in accelerating the hard machining with a defined cutting edge by increasing the feed rate and thereby shortening the cycle time for machining the workpiece. For the duration of the engagement with the workpiece, the tool cutting edge is moved in a direction orthogonal to the workpiece axis of rotation, so that the feed movement runs parallel to or at small angles to the cutting edge. According to the invention, the increased feed rate is achieved through an optimized design of the tool angle. The angle of incidence, i.e. the cutting edge alignment relative to the workpiece axis, and the special geometrical relationships during the tool movement orthogonal to the workpiece axis of rotation had to be taken into account. A swivel movement of the tool relative to the workpiece causes additional changes in the setting and clearance angles. These should also be taken into account. With a setting angle of 30 ° to 60 °, a range of 80 ° to 135 ° was determined for the wedge angle at the tool cutting edge. Advantageous values for the negative rake angle are in the range from approx. -1 ° to -15 ° and for the clearance angle at 5 ° to 30 °. In this way, feed speeds of up to 900 mm / min are currently achieved. For hard machining with a defined cutting edge, a minimum grinding allowance is chosen so that unavoidable geometry errors can be corrected reliably. During the subsequent grinding process, the tool wear can be easily monitored through the regular dressing processes. Therefore, the desired production quality can also be ensured with random workpiece controls. Compared to the state of the art, this results in considerable time and cost advantages.

• 1 zeigt die Vorderansicht einer Werkzeugmaschine
• 2 zeigt den Werkzeugrevolver und die Schleifspindel von oben gesehen
• 3 zeigt den Eingriff des Werkzeugs 15 am Werkstück 7 in vergrößerter Darstellung
• 4 zeigt das Werkzeug 7 mit den Werkzeugwinkeln in vergrößerter Darstellung

The invention is explained in more detail below using exemplary embodiments.

• 1 shows the front view of a machine tool
• 2 shows the tool turret and the grinding spindle seen from above
• 3 shows the engagement of the tool 15th on the workpiece 7th in an enlarged view
• 4th shows the tool 7th with the tool angles in an enlarged view

1 shows a machine tool 1 for high-precision machining of hardened workpieces 7th with both non-circular and rotationally symmetrical inner and outer contours, with details of the drive, the control and the housing not being shown that are not essential to the invention. The work pieces 7th are in the workpiece holding device 6th , consisting of the workpiece spindle 8th and the tailstock 9 clamped and set in rotation. On the machine frame 2 are vertical guides 3 for the two vertical slides 4th , 4 ' intended. These in turn carry guides 12 for the horizontal slide 5 , 5 ' . In the horizontal slide 5 is the tool turret 10 around a pivot axis 13th rotatably mounted. The second horizontal slide 5 ' takes the grinding spindle 11 with the grinding wheel 16 on.

2 shows the tool turret 10 and the grinding spindle 11 in the view from above. By swiveling the tool turret 10 around the pivot axis 13th becomes the tool 15th with the edge 17th with the workpiece 7th engaged. The contour deviations of the workpiece caused by the shape of the cutting edge are thereby taken into account 7th by an infeed movement of the horizontal slide 5 along the guides 12 balanced.

Then the workpiece 7th in the same clamping by the grinding wheel 16 subjected to a grinding treatment. The regular dressing processes reduce wear on the grinding wheel 16 easy to monitor. Therefore, a random inspection of the workpiece is sufficient to ensure production quality.

Out 3 is the engagement of the tool 15th on the workpiece 7th evident. The cutting edge 17th is under the angle of attack ε against the workpiece rotation axis 19th inclined. It will move in the direction of movement during the procedure 20th orthogonal to the workpiece rotation axis 19th emotional. From this and the rotational movement 22nd of the workpiece 7th the result is the feed movement 22nd parallel to the cutting edge 17th or at small angles. For a better overview, in 4th the tool 7th shown enlarged with the tool angles. The cutting edge 17th is defined by the wedge angle β and the rake angle γ . As advantageous values for the wedge angle β became a range from 80 ° to 135 ° and for the negative rake angle γ a range from minus 1 ° to minus 15 ° is determined. The clearance angle α advantageously moves in a range between 5 ° and 30 °. Clearance angle α , Wedge angle β and setting angle χ each add up to 180 °; ie if two of these angles have been specified, the third is the difference to 180 °. Particularly complex relationships arise when the clearance and setting angles vary during workpiece engagement because the tool 7th around the pivot axis 13th is pivoted. With the optimized tool angles, the feed rate can be increased to values of up to 900 mm / min.

List of reference symbols

1

Machine tool

2

Machine frame

3

guide

4th

4 'vertical slide

5

5 'horizontal slide

6th

Workpiece holding device

7th

workpiece

8th

Workpiece spindle

9

Tailstock

10

Tool turret

11

Grinding spindle

12

guide

13

Swivel axis

14th

Axis of rotation

15th

Tool

16

Grinding wheel

17th

Cutting edge

18th

Dressing device

19th

Workpiece rotation axis

20th

Direction of movement

21st

Feed movement

22nd

Rotational movement

A.

Measurement

α

Clearance angle

β

Wedge angle

ε

Angle of attack

γ

Rake angle

κ

Setting angle

Claims (6)

Process for high-precision machining of both out-of-round and rotationally symmetrical inner and outer contours on rotating workpieces (7) with the following process steps: - Creating a desired workpiece contour by forging and / or soft machining with an allowance (A) for hard machining, - Hardening the workpiece ( 7) - Hard machining of the workpiece (7) with a defined cutting edge (17) and subsequent grinding process in one setting, characterized in that, in order to achieve a maximum feed rate, the cutting edge (17) is moved relative to the workpiece (7) in such a way that the feed movement (21 ) runs parallel or at small angles to the edge of the cutting edge (17) and that the contour deviations of the workpiece (7) caused by the cutting edge shape are compensated for by a feed movement. Procedure according to Claim 1 , characterized in that during hard machining with a defined cutting edge (17) the setting angle (χ) and the clearance angle (α) are changed by a pivoting movement of the tool (15) about the pivot axis (13). Procedure according to Claim 2 , characterized in that the relative movement between the tool (15) and the workpiece (7) causes the setting angle (χ) to vary within a range of 40 ° to 100 ° and the clearance angle (α) to vary within a range of 5 ° to 30 °. Method according to one of the Claims 1 to 3 , characterized in that the workpieces (7) are measured randomly to monitor the manufacturing quality. Machine tool for machining both non-circular and rotationally symmetrical inner and outer contours on a rotating workpiece (7), with at least one tool (15) with a flat cutting edge (17), the cutting edge (17) for performing a feed movement in a direction orthogonal to the workpiece axis of rotation (19) is movable, characterized in that the wedge angle (β) is in a range from 80 ° to 135 °, that the setting angle (ε) between the cutting edge (17) and the workpiece rotation axis (19) in a range between 30 ° to 60 ° and that a grinding spindle (11) is provided for grinding. Machine tool after Claim 5 , characterized in that the rake angle (γ) is in a range from minus 1 ° to minus 15 °.

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