DE102007037791A1 - Process for production of rotationally symmetrical surface on workpiece by hard dry turning useful in machine and machine tool production technology is more cost effective than previous methods and avoids use of expensive coolants - Google Patents

Abstract

Process for production of a rotationally symmetrical surface on a workpiece (1) by hard dry turning (sic) of a semifinished surface (3) and grinding out the rotationally symmetrical surface (4) from it, to give a rotationally symmetrical surface of predetermined dimensions, profile, and locational and surface tolerances, which is then subjected to finish polishing.

Description

The invention relates to a method for producing a rotationally symmetrical surface on a workpiece,
wherein for the production of the rotationally symmetrical surface on the workpiece, a semi-finished surface is first produced by hard turning and then the finished rotationally symmetrical surface is produced by grinding from the semi-finished surface,
and wherein the method is performed so that the finished rotationally symmetric surface complies with predetermined dimensions, predetermined shape and position tolerances and predetermined surface tolerances.

Such a method is operated for example with "STRATOS" machines, which are in the company brochure "STRATOS grinding, hard turning and more", Studer Schaudt GmbH, Stuttgart, 10/2002 , are described.

in the Mechanical engineering becomes workpieces in a variety of ways with rotationally symmetric surfaces needed, about in bearings and gearboxes. Rotationally symmetric surfaces occur, for example, as flat surfaces, conical surfaces and bores, such as gear wheels.

Workpieces, and thus also the rotationally symmetric surfaces on workpieces, need for a designated use, such as the Installation in a machine, given dimensions and tolerances suffice; These are usually in a design drawing recorded. Holds a workpiece the given Tolerances not a, so it is for the intended use unusable and must be reworked or discarded. For rotationally symmetric surfaces on a workpiece are typically dimensions, shape and position tolerances and Surface tolerances specified.

Rotosymmetrical Surfaces are in the prior art, for example, with a STRATOS machine mentioned above, by a combination made by hard turning and wet grinding. It is done by the hard turning first a rough preprocessing of the workpiece, while still a considerable measure (usually around 1/10 mm) remains. The semi-finished surface after hard turning stops neither the given dimensions including the Form and position tolerances, nor the given surface tolerances one. Only by the subsequent wet grinding is compliance with the given dimensions and tolerances in the finished rotationally symmetric Area reached.

adversely this process involves the high costs of wet grinding, in particular by the consumption of cooling lubricant and due to wear on the grinding blade.

Object of the invention

task The present invention is to provide a method, with the rotationally symmetric surfaces on a workpiece can be produced at a lower cost.

Brief description of the invention

These Task becomes surprisingly simple, but effective Kind solved by a method of the type mentioned, characterized in that the hard turning as a dry hard turning is executed, wherein the hard turning produced Semi-finished surface already the given dimensions as well as the given shape and position tolerances, and that subsequent grinding as a dry finish grinding is performed.

in the Within the scope of the invention, the greatest part takes place the material removal on the workpiece during hard turning, and material removal during grinding is reduced to a minimum. This is possible because hard turning with a so great precision (precision hard turning) is guided that the given dimensions including at least the shape and position tolerances of the rotationally symmetric to be produced Area already adhered to the semi-finished area become. This is a lathe with high machine rigidity, short Force flow and low natural oscillations used; a temperature insulated Chip hopper and a monoblock machine bed and a Complete machine stand in mineral casting can also to comply with the required manufacturing accuracy contribute. During subsequent grinding, the workpiece needs only to be reworked so far that all predetermined Surface tolerances are met, what a very low material removal is sufficient, usually less than 5 microns Abrasive abrasion (i.e., feed path of the grinding blade from the contact of the Grinding blade to the material surface of the workpiece). The given surface tolerances usually give maximum permissible surface roughness and maximum permissible surface undulations and one Type of surface structure (directional / non-directional, possibly with maximum degree of alignment).

As a rule, in the context of the invention, the finish grinding only serves to set a desired surface structure (namely a non-oriented surface structure, as is typical for grinding) and / or to reduce surface waviness. Conventional hard turning creates a directed surface structure, which can form grooves. For many applications, such grooves on the workpiece are undesirable because they lead, for example, to the discharge of lubricating oil can. Hard turning with a geometrically determined cutting edge can also cause a periodic surface waviness. The periodic surface waviness is also undesirable for many applications since it can lead to workpiece vibrations. If edge zone damage (such as re-hardening and tempering zones on the workpiece surface) has occurred during hard turning of the workpiece, these can also be removed by the finish grinding.

Due to the low removal of material during the hard turning subsequent finishing grinding can be dispensed with the use of a cooling lubricant during grinding. The process heat generated during finishing grinding is negligible or can also be dissipated by the workpiece itself and the surrounding air; Material damage in the form of Neuhärtungs- or tempering zones are not introduced by the Schlichtschleifen. A customary chip removal rate in the case of finish grinding within the scope of the invention is 0.05 to 0.2 mm ³ / (mm.s), preferably 0.1 mm ³ / (mm.s). Also, the service life of the grinding blade is increased because less material needs to be removed during grinding per workpiece.

at conventional (coarse) hard turning and wet grinding omitted Approx. 14-17% of the manufacturing costs of a workpiece on the use of cooling lubricants and their maintenance as well as disposal; These costs can be covered by the invention be saved. By dispensing with liquid coolant is also the area required for workpiece machining reduces (in particular, no coolant treatment or filter system), the environment is relieved (no cooling lubricant disposal necessary) and a health risk to the production staff is avoided (possible skin diseases through contact with cooling lubricants).

in the Frame of the invention finds between (precision) hard turning and finishing grinding no further material removal by others Processing process instead.

Preferred variants of the invention process

at a preferred variant of the invention Method is provided that for the finished rotationally symmetric Surface specified surface tolerances a given surface roughness, a given surface waviness and a given surface structure, and that only by the finish grinding the given surface roughness, the given surface waviness and the given surface structure produced the finished rotationally symmetric surface become. In this variant, the precision requirements are limited to the hard turning on the compliance with the given dimensions as well as the shape and position tolerances, what the process control simplifies and reduces the expenditure on equipment.

A alternative, likewise preferred process variant is characterized characterized in that for the finished rotationally symmetric Surface specified surface tolerances a given surface roughness, a given surface waviness and a given surface structure include the semi-finished surface produced by hard turning as well already complies with the specified surface roughness, and that by the subsequent finishing grinding the predetermined Surface waviness and the given surface structure produced the finished rotationally symmetric surface become. In this variant, the effort (and material removal) minimized during dry finish grinding, making this process especially Fast and wear-resistant for the grinding blade is.

at an advantageous variant of the method done hard turning and the finish grinding on the same lathe and in the same Clamping the workpiece. This can make changeover time be saved; the machining of the workpiece is special fast.

Prefers is still a process variant in which for the Abrasive wear SA of finish grinding applies: SA ≤ 10 μm, preferably SA ≦ 5 μm, and more preferably SA ≦ 2 μm. An abrasion removal of this magnitude is sufficient in the process of the invention to rotationally symmetric Surfaces on workpieces with usual accuracy requirements (Tolerance bands) to manufacture.

Also preferred is a method variant in which the roughness depth R _{z of} the semi-finished surface is: R _z ≦ 5 μm. If the hard turning is performed so accurately that the surface roughness is then already as low as specified in this variant, it is regularly possible to maintain the entire surface tolerances with very little material removal in the finish grinding.

In this case, a variant of the method according to the invention is particularly preferred in which the grinding finish SA of the finish grinding and the roughness depth R _{z of} the semi-finished surface are: SA ≦ R _z . In other words, in this variant, the material removal during finish grinding is limited to the removal of tips in the surface profile. This is possible with very little wear for the grinding blade; Solid material is not removed. The carrying percentage of the surface can thus be increased become.

Advantageous is still a variant of the method in which by the Schlichtschleifen Edge zone damage from the semi-finished area be removed. Edge zone damage (such as re-hardening and tempering zones), which were created during hard turning (such as local workpiece heating), usually enough only slightly into the material (about 1-2 μm) and thus can be eliminated as part of the finish grinding become; by ablation of the edge zone damage, the Surface properties (in particular the hardness and abrasion resistance) are unified and improved.

All Particularly preferred is a process variant in which the hard turning with a geometrically determined cutting edge, in particular a CBN cutting edge, he follows. CBN cutting (CBN = cubic boron nitride) are in practice proven to wear and because of their large Hardness suitable for machining many materials.

A preferred development of this method provides that by the smoothing a periodically occurring waviness of the Semi-finished surface is shortened and reduced. Often, after hard turning with a geometrically determined Cut a surface ripple registered over the permissible (given) tolerance is. By the Simple grinding can be easily eliminated.

Prefers It is still, if the Schlichtschleifen with a geometric undefined cutting edge, in particular a CBN cutting edge or a PCD cutting edge. The abrasive particles of geometrically indeterminate Sanding blades provide an often desired non-directional surface structure. The geometrically indefinite edge can be designed in particular as a grinding wheel, grinding mandrel, or combination grinding wheel with straight and conical section. The Materials CBN and PKD (polycrystalline diamond) have become proven in practice as low-wear and can because of the great hardness for machining many workpiece materials are used.

Especially preferred is a process variant in which the finish grinding as a plunge finish grinding only by applying a grinding blade to the semi-finished area. This procedure allows a particularly high manufacturing accuracy in the finishing grinding. The grinding blade (the abrasive body) is essentially perpendicular to the local surface of the workpiece moved (delivered), and in particular not parallel to the local Advanced surface. For the production of larger Surfaces, the grinding blade is possibly multiple times stated. As an alternative to this variant, however, can also be a movement the grinding edge parallel to the local surface (usually in the axial z-direction) in the inserted state.

at an advantageous development of this process variant the grinding blade is guided by means of piezoelectric elements. Due to the piezoelectric elements is the temporal forces precisely adjustable during finish grinding; the control can be done as power-guided grinding.

at another advantageous development of the above process variant is the grinding blade on an elastically yielding element educated. About the elastically yielding element or its positioning relative to the workpiece can be a check the cutting force. The expected bend of the elastically yielding Elements is thereby in the design and alignment of the grinding blade included to the geometry of the workpiece to be produced to be able to protect precisely.

Prefers is still a variant of the invention Method in which the shape and position tolerances each have a tolerance band having a width TBB, where TBB ≤ 20 μm, preferably TBB ≤ 10 μm, and particularly preferred TBB ≤ 2 μm. Note that the semi-finished area already complies with the form and positional tolerances. The grinding removal SA in the context of the method according to the invention is then according to the invention in terms of amount smaller than the width of the tolerance band TBB in the same local Area of the workpiece, otherwise would through the grinding removal SA the given shape and position tolerances (zu which also include absolute upper and lower limits, such as for a radius) leave again.

at A preferred variant of the method comprises the shape and position tolerances Tolerances regarding roundness and / or cylindricity and / or conicity. With this information, the sufficiently well to describe most rotationally symmetric surfaces.

Further Advantages of the invention will become apparent from the description and the Drawing. Likewise, the above and the still further features according to the invention in each case individually for yourself or for several in any combination use Find. The embodiments shown and described are not meant to be an exhaustive list but rather have exemplary character for the Description of the invention.

Drawing and detailed Description of the invention

The The invention is illustrated in the drawing and is based on embodiments explained in more detail. It shows:

1 a schematic view of a workpiece on which a rotationally symmetric surface is made with the method according to the invention;

2a the result of a profile measurement in a rotationally symmetrical surface after hard turning according to the invention;

2 B the result of a profile measurement in a rotationally symmetrical surface after a dry grinding according to the invention;

3 a schematic cross-sectional view of a combination grinding wheel for use in the invention;

4 a schematic view of a grinding wheel on an elastically compliant element.

The 1 illustrates in highly schematic cross-sectional representation of the sequence of the method according to the invention for producing a rotationally symmetrical surface on a workpiece 1 , The rotationally symmetrical surface to be produced is a radially outer surface of the disk-shaped workpiece which is rotationally symmetrical with respect to an axis A. 1 , Note the radial direction r. In 1 For simplicity, only one half of the workpiece is shown.

For which is to be produced rotationally symmetric surface a specification including a form and Lagetoleranz-specification, which is especially in one to be observed Range of the radius of the surface to be produced between the absolute radius values rmin and rmax over the illustrated axial Length manifests, cf. also the dashed lines. The distance between rmin and rmax sets a tolerance bandwidth TBB with respect to the radius of the surface to be manufactured represents.

The workpiece 1 The process begins as a blank with a radially outer raw surface 2 , In the first method step according to the invention, a dry precision hard turning takes place. At the end of this hard turning, the workpiece points 1 the semi-finished area 3 on. According to the invention, the semi-finished surface stops 3 The dimensional specification, including the given shape and position tolerances, already applies: The radius of the semi-finished surface is anywhere between rmin and rmax.

However, the semi-finished area indicates 3 still an undesirable periodic ripple along the axial direction A (Note that the shape of the surface in 1 is exaggerated). According to the specifications for the surface tolerances to be observed, this waviness must still be eliminated.

Hard turning is now followed by a dry finish grinding. In this finishing grinding, there is still a minimal material removal, corresponding to the grinding removal SA. The grinding removal SA is measured from the first contact of a grinding blade to the end of the delivery of the grinding blade to the workpiece. The first contact of the sanding blade with the half-finished surface 3 can be determined acoustically, for example.

When finishing grinding in 1 only the surface waviness of the semi-finished surface will be 3 ablated. After the end of the finish grinding, the workpiece is lying 1 the finished rotationally symmetric surface 4 in front.

The finished rotationally symmetric surface 4 not only keeps the given dimensions including the given shape and position tolerances (represented here by the range between rmin and rmax of the radius), but is also free of surface waviness, so that the given surface tolerances for the finished workpiece 1 be respected. Since the specified dimensions including form and position tolerances were complied with prior to finishing grinding, the grinding allowance SA could be kept very low. In fact, even in the method according to the invention, the grinding removal SA must be kept low: a large grinding removal SA after the "hard turning to measure" would again lead to leaving the given dimensions and / or leaving the tolerance range of the given shape and position tolerances; would inevitably and irretrievably become too small.

2a and 2 B illustrate the adjustment of the surface structure according to the invention on a rotationally symmetrical surface (outer circumferential surface) of a circular cylindrical workpiece.

The workpiece was first processed according to the invention with a precision hard turning. The area after hard turning shows the surface profile according to the diagram of 2a on (right-value axis: axial position measured over 4.80 mm, high-value axis: radial position). There are regularly spaced peaks and valleys visible. The roughness depth (interval width peak to valley) is approx. 1.5 μm. There is a directed surface structure.

After dry grinding, the workpiece has the in 2 B displayed surface profile (the dimensions of 2 B and 2a are equal). Except for a few individual peaks and valleys, the roughness depth after dry grinding is comparable to the roughness depth after precision hard turning, but there is no more regularity in the change between peaks and valleys. This is a consequence of the irregular, grained surface of the grinding blade. There is a non-directional surface structure (stochastic surface).

Due to the precision hard turning, the dimensions of a rotationally symmetrical surface, together with its shape and position tolerances, can be set exactly as well as with grinding. However, the adjustment of the surface tolerances (in particular with regard to waviness and structure) is left to the finish grinding according to the invention. An abrasion removal SA, which roughly corresponds to the roughness depth R _z after hard turning, already produces a completely new surface structure.

The 3 schematically shows a pin-like grinding tool, which can be used in the invention. The grinding tool has a receiving pin 31 on, with which the grinding tool can be held and rotated in a tool spindle or its chuck. At the bottom of the grinding tool there are two grinding cutting sections. The upper, cylinder-shell-like section 32 is designed for bore loops, and the lower, cone-shaped portion is designed for cone grinding. Both sanding sections 32 . 33 are filled with CBN abrasive particles (grains) with a particle size of approx. 0.5-1 μm. Both sanding sections 32 . 33 represent geometrically indefinite cutting.

4 shows very schematically the processing of a workpiece according to the invention 1 with a geometrically indefinite sanding blade 41 , The workpiece 1 has a machined, rotationally symmetric semi-finished surface 3 and is rotatably mounted about the axis A in a workpiece spindle (not shown).

The sanding blade 41 is on an elastically yielding element 42 attached; the elastically yielding element 42 here is a wave that is the grinding edge 41 with a chuck 43 combines. Through the chuck 43 can the sanding blade 41 in rotation 44 be offset. The chuck 43 is still in two directions horizontally (x) and vertically (z) movable. In the force-free state would be the element 42 just.

In the state shown is the elastically yielding element 42 but slightly deflected, whereby an elastic force is applied to the grinding blade 41 to the workpiece 1 pressed. Through the x-position of the chuck 43 can (with known E-modulus of the element 42 ) the contact pressure of the grinding blade 41 be set. According to the invention, the geometry of the grinding blade 41 and element 42 as well as the elastic properties of the elastically yielding element 42 (ie the geometry under deflection under load) to ensure a precise machining of the workpiece 1 or to ensure the production of rotationally symmetric surface. Note that the deflection of the elastic element 42 greatly exaggerated in 4 is shown.

While the sanding blade 41 with the workpiece 1 is in contact, this is preferred only in the x-direction (ie, substantially perpendicular to the workpiece surface to be machined 3 ) delivered. Around the semi-finished area 3 over their entire extent to edit, the grinding blade 41 preferably only in the workpiece 1 lifted state in z-direction (ie substantially parallel to the surface 3 ). This improves the control over the grinding process, and in particular the control over the local grinding abrasion.

In summary describes the invention a method for producing a rotationally symmetric Surface on a workpiece, the workpiece First turned off by hard turning to the final dimensions (in accordance with the tolerance requirements for shape and position), and in a subsequent dry grinding only one more Surface treatment is made that measures the dimensions of the workpiece no longer appreciably changed. The abrasion remains below the width of the tolerance band for the Dimensions. This allows to cool lubricants when grinding be omitted, which lowers the production costs and the environment and protects the health of employees.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited non-patent literature

• - "STRATOS grinding, hard turning and more", Studer Schaudt GmbH, Stuttgart, 10/2002 [0002]

Claims (16)

Method for producing a rotationally symmetrical surface on a workpiece ( 1 ), wherein for the production of the rotationally symmetric surface on the workpiece ( 1 ) by hard turning a semi-finished surface ( 3 ) and then by grinding from the semi-finished surface ( 3 ) the finished rotationally symmetric surface ( 4 ), and wherein the method is performed so that the finished rotationally symmetric surface ( 4 ) specified dimensions, predetermined shape and position tolerances and predetermined surface tolerances, characterized in that the hard turning is performed as a dry hard turning, wherein the semi-finished surface produced by the hard turning ( 3 ) already complies with the given dimensions and the given shape and position tolerances, and that the subsequent grinding is carried out as a dry finish grinding. A method according to claim 1, characterized in that for the finished rotationally symmetric surface ( 4 ) predetermined surface roughness, a given surface waviness and a given surface structure include, and that only by the finish grinding the predetermined surface roughness, the predetermined surface waviness and the predetermined surface structure of the finished rotationally symmetric surface are produced. A method according to claim 1, characterized in that for the finished rotationally symmetric surface ( 4 ) predetermined surface roughness, a predetermined surface waviness and a predetermined surface structure include that the semi-finished surface ( 3 ) already complies with the predetermined surface roughness, and that the predetermined surface waviness and the predetermined surface structure of the finished rotationally symmetrical surface are produced by the subsequent finishing grinding. Method according to one of the preceding claims, characterized in that the hard turning and the finish grinding on the same lathe and in the same clamping of the workpiece ( 1 ) respectively. Method according to one of the preceding claims, characterized in that for the Schleifabtrag SA of Simple sanding applies: SA ≤ 10 μm, preferably SA ≦ 5 μm, and more preferably SA ≦ 2 μm. Method according to one of the preceding claims, characterized in that the roughness depth R _{z of} the semi-finished surface is: R _z ≤ 5 μm. Method according to one of the preceding claims, characterized in that the grinding removal SA of the finish grinding and the roughness depth R _{z of} the semi-finished surface are: SA ≤ R _z . Method according to one of the preceding claims, characterized in that by the finish grinding edge zone damage from the semi-finished surface ( 3 ) are removed. Method according to one of the preceding claims, characterized in that the hard turning with a geometric certain cutting edge, in particular a CBN cutting edge, takes place. A method according to claim 9, characterized in that by the finishing grinding a periodically occurring waviness of the semi-finished surface ( 3 ) is shortened and reduced. Method according to one of the preceding claims, characterized in that the finishing grinding with a geometrically indefinite cutting edge ( 41 ), in particular a CBN cutting edge or a PCD cutting edge. Method according to one of the preceding claims, characterized in that the finishing grinding as a plunge-finish grinding only by applying a grinding blade ( 41 ) to the semi-finished surface ( 3 ) he follows. A method according to claim 12, characterized in that the grinding blade ( 41 ) is guided by means of piezoelectric elements. A method according to claim 12, characterized in that the grinding blade ( 41 ) on an elastically yielding element ( 42 ) is trained. Method according to one of the preceding claims, characterized in that the shape and position tolerances respectively have a tolerance band with a width TBB, where: TBB ≤ 20 μm, preferably TBB ≤ 10 μm, and particularly preferred TBB ≤ 2 μm. Method according to one of the preceding claims, characterized in that the shape and position tolerances include tolerances with respect to - roundness and / or cylindricity - and / or conicity.