DE102015113141A1 - Method for machining a workpiece surface and workpiece - Google Patents

Abstract

Disclosed is a method for processing a workpiece surface, in which a first-order surface shape is formed by a first manufacturing method, for example a machining operation. The thereby adjusting surface shapes 2nd and / or 3rd order are then changed by a laser processing, the surface shape 1st order remains substantially unchanged. In this way, it is possible to form the first-order surface shape substantially independently of the third-order surface shape and / or the second-order surface shape, and thus to adjust the reflectance.

Description

The invention relates to a method for processing a workpiece surface according to the preamble of patent claim 1 and a workpiece produced by such a method.

On surfaces of workpieces are often made tribological, mechanical, optical or other reasons defined requirements in terms of their surface shape of different orders.

A first-order surface shape relates to the shape of the workpiece or portions of the workpiece to ensure a function.

The second-order surface shape relates to the macrostructure of the surface, in particular the waviness. This ripple is often an image of the kinematics of the manufacturing process, such as the kinematic roughness. For example, when milling as a function of tool speed and feed rate, the shape of the individual cutting edge is periodically cut into the workpiece. The distance between these cuts is then defined as a tooth feed.

Thus, every cutting process leaves its characteristic surface structure, which is not intended as the structure of the workpiece i.d.R. Often the goal is to smooth this structure by tool rounding and by reducing the tooth feed so that it is only of subordinate depth.

A special process - the broadsize machining - uses this smoothing effect by a crowning of the blade with a large radius.

In particular, using an extremely smooth cutting edge, which is made for example of monocrystalline diamond, can be an extremely smooth

Surface can be produced, which can surpass the result of a polished surface.

The fine structure of the individual section represents the third-order surface shape of the workpiece surface. It can be influenced by structuring or smoothing the cutting edge.

Analogous to machining with geometrically determined cutting edges, this relationship also applies to geometrically indefinite cutting edges. There is achieved by fine graininess of the cutting material smoothing of the surface.

There are therefore various possibilities for influencing the workpiece surface with respect to smoothing of the second and third order of the surface shape. This corresponds to an improvement of the surface, because of tribological, mechanical or optical reasons, a smoother surface desired, often a simultaneous compliance with the surface shape of the first order with high precision is sought.

For tribological, mechanical, optical or other reasons, but also a rough surface can be sought. For this purpose, there are machining processes such as brushing or grinding with a relatively coarse grain size. Other ablation methods are used, such as etching, chemical or electrochemical removal. Even applying methods such as painting or coating can produce non-reflective surfaces.

However, machining processes leave i.d.R. Processing marks that are aligned according to the direction of processing. This is often not wanted.

A disadvantage of all these methods is the influence of the surface shape of the first order, as these methods act more or less strongly on different manifestations of the surface shape. Very often, these methods are more effective in the area of workpiece edges. For example, etching and painting always leads to a certain unwanted edge rounding.

As described above, the surface shape 1st, 2nd and 3rd order can be selectively influenced by machining. In this case, for example, the tooth feed can be reduced in order to smooth the surface shape of the second order (waviness, kinematic roughness). The 3rd order surface texture (roughness) can be smoothed by improving the cutting edge chipping. In both measures, the dimensional accuracy (1st order surface shape) also becomes higher by indirectly having lower cutting pressures, which cause less deviation due to less deformation of the part during machining.

If a surface is to be influenced with regard to a low degree of reflection, then the surface must receive a targeted higher roughness.

Increasing the kinematic roughness (2nd order surface shape) by a more pointed cutting geometry adversely affects the shape accuracy (1st order surface shape).

Therefore, in particular, the third-order surface shape can be influenced by a blade chipping, so that the roughness is increased and the surface, for example, reflects less light.

However, to increase the influence of the single cut on the overall surface shape, the tooth feed must be increased. Thus, a surface is formed, which in turn has an increased waviness (2nd order surface shape).

There is therefore no possibility, for example, to reduce the degree of reflection or any other geometric surface property by means of a machining production method in a targeted manner without adversely affecting further properties of the surface. In particular, the non-reflecting surface produced by machining has limited dimensional accuracy (first-order surface shape) and high ripple (second-order surface shape). This is not wanted.

In the US 4,914,747 A is described a headlamp construction, in which a division of headlight areas is done by a beam stop. An edge of this beam diaphragm produced by projection through a corresponding optics a defined light image. The beam stop can shade certain areas. In order to increase the quality of the light image, the radiation diaphragm is specifically equipped with a non-reflective surface. This is done by a special matt lacquer layer. The non-reflective surface serves to avoid chromatic aberration of the light image. A disadvantage of this design is the high cost in the application of a special paint layer and the heat sensitivity of this paint with increase in light output and the associated increase in heat generation. Especially with a special shaping of the beam aperture, the covering of the surface not to be coated is very complicated.

In the DE 60 2004 002 043 T2 An embodiment of a headlamp is known in which two different light sources are used. In this case, a light source generates the low beam, which produces a legally prescribed cut-off line. The second light source can illuminate the area above this cut-off line. In the combination of both lights, the high beam is produced. In the case of high beam, both the area above and the area below the cut-off line are illuminated. In this case, special requirements are imposed on the dimensional accuracy (surface shape of the first order) of the radiation diaphragm because the mixture of the two light images should not have an unlit area (shading). The images should overlap with high accuracy in the range of the light-dark boundary so that it is no longer visible.

In the WO 00 2014 165 884 A2 An additional effort is described to increase the quality of the light image in the area of the cut-off line. Additional light paths are created that can illuminate the above shading. The beam stop must be equipped with at least one non-reflective area. The reflectance must be kept within a defined tolerance.

The DE 10 2010 054 858 A1 discloses a method for producing a reflection-reducing coating on a substrate, which is irradiated by a laser.

In contrast, the invention has the object to provide a method and a workpiece produced by such a method, in which an influence of the surface shape 3rd order to influence a geometric surface property, for example, the reflectance with little procedural effort is possible.

This object is achieved by a method having the features of patent claim 1 or by a workpiece produced by such a method.

Advantageous developments of this method are the subject of the dependent claims.

According to the invention, a combination of machining and laser machining is used in order to set the geometric surface property, in particular the reflectance, to the required value.

According to the invention, in a method for processing a workpiece surface, a surface shape of the first order, which is predetermined by the function of the workpiece, is formed by a shaping manufacturing process. The processing parameters result in a second-order surface shape that affects the macrostructure of the surface. This in turn forms a third-order surface shape in the form of a fine structure. According to the invention, the surface shape of the first order is created by a first production method, preferably a machining operation. The resulting second or third order surface shape is then changed by laser processing to set a predetermined geometric surface property, for example, a reflectance. This change is made such that the 1st order surface shape remains substantially unchanged.

By such a procedure, the above-described disadvantages can be avoided.

In one embodiment of the invention, the surface shape of the first order, which is predetermined by the function of the workpiece, is influenced in a targeted manner by the machining. The subsequent laser processing influences this surface shape of the first order at most to the extent that the surface shape of the 2nd and 3rd order are influenced by this laser processing. In this way, the dimensional accuracy of the workpiece over conventional solutions can be improved.

The machining operation may be, for example, a turning or milling.

In a Breitschlichtbearbeitung at least one convex secondary cutting edge is used to process the surface shape 1st order.

Dimensional accuracy can be further improved if the cutting edges used in the machining process consist of a diamond material.

The laser processing is designed in one embodiment of the invention so that a change in shape of the surface shape of 2nd order and / or 3rd order takes place.

Such a laser processing can be done by removing, wherein one or more wells can be performed.

In one embodiment of the invention, the laser processing initiates a chemical reaction on the workpiece surface whereby an oxide or other reaction product is formed or left on the surface.

In another variant, the laser processing is controlled so that the workpiece material melts and melt particles deposit again on the workpiece surface.

The control in the laser processing can be carried out by a positioning device, via which a laser beam is movable relative to the workpiece, so that the laser machining takes place at different areas of the workpiece.

The activation of the laser beam can be effected in such a way that a pattern or a structure is produced on the workpiece surface. This pattern may be a cup pattern or a line pattern or other pattern.

It is particularly preferred if the pattern of the surface shape of the 2nd and / or 3rd order is assigned.

The shape and depth of the structure / recess formed by the laser machining can be varied by changing the angle of attack of the laser.

Preferred embodiments of the invention are explained in more detail below with reference to schematic drawings. Show it:

1 Schematic representations of the surface shape 1st, 2nd and 3rd order of a workpiece;

2 a 2nd or 3rd order surface shape formed with a cup structure;

3 a variant of the embodiment according to 2 with overlapping wells;

4 a schematic representation of a method in which a laser beam is coupled obliquely to the workpiece surface;

5 a schematic diagram of a headlamp for flash and

6 a schematic diagram of a processed according to a method of the invention workpiece surface.

1a shows a schematic part of a functional area 4 a workpiece 6 , This functional area 4 is executed with a wave structure, which in the sense of the definitions explained at the outset a surface shape 1st order 1 represents. This wave structure (1st order surface shape) is due to the function of the workpiece 6 specified. Of course, the geometry of the first-order surface shape is not limited to a wave structure, but may include, for example, a flat surface, another structure, etc.

1b shows a section along the line AA in 1a , Visible in this representation is the wave structure forming the surface shape of the first order 1 , This structure is in turn with a surface shape of 2nd order 2 executed, for example, forms a ripple or kinematic roughness, which represents a characteristic surface structure depending on the manufacturing process used. Such a structure is generally undesirable.

As in detail B in 1c is shown, this characteristic surface structure (surface shape 2nd order 2 ) again with a fine structure, the surface shape 3rd order 3 formed. This can be influenced, for example, by the structuring or smoothing of a cutting edge.

According to the invention, the surface shapes become 2nd and / or 3rd order 2 . 3 specifically produced by a laser machining, the process being carried out so that the surface shape of the first order 1 remains essentially unchanged.

berechnen. Das heißt, zur Einstellung eines bestimmten Reflexionsgrades muss entsprechend das Oberflächenverhältnis A’:A gewählt werden. Selbstverständlich gehen auch andere Parameter in die Bestimmung des Reflexionsgrades ein. Wie bereits ausgeführt, ist die Erfindung jedoch keinesfalls darauf beschränkt, durch geeignete Ausbildung der Oberflächengestaltung 2. und 3. Ordnung einen Reflexionsgrad eines Werkstücks einzustellen, sondern durch die erfindungsgemäße Verfahrensweise können auch andere Oberflächeneigenschaften beeinflusst werden.Such as in 2 indicated, the surface shape 2nd order 2 or the surface shape of 3rd order 3 be formed by a cup pattern. In this case, by means of a laser beam, a plurality of well-shaped depressions 8th educated. These can be introduced, for example, by means of a fiber laser whose laser beam is directed by means of a scanner arrangement onto the area to be processed. Such lasers are used, for example, as marking lasers and are also used in the structuring and introduction of break separation notches. As in 2 shown, the well-shaped depressions 8th be arranged in a predetermined pattern, wherein the horizontal distance with x and the vertical distance with y is predetermined. The diameter of each cup is in 2 denoted by d. From this diameter d and the distances x, y, for example, the area A of a cup and the remaining, non-cupped surface portion A 'can be calculated. The design of the cell structure makes it possible, for example, to set the reflectance ρ, so that, for example, according to the method according to the invention, a reflector of a headlight can be optimized with regard to the reflectance. The area ratio of the surface portions A 'and A can be calculated according to the formula:

to calculate. That is, to set a certain reflectance, the surface ratio A ': A must be selected accordingly. Of course, other parameters also enter into the determination of the reflectance. However, as already stated, the invention is by no means limited to setting a reflectance of a workpiece by suitable design of the surface configuration of the second and third order, but other surface properties can also be influenced by the method according to the invention.

In 3 an embodiment is shown in which the well-shaped depressions 8th not spaced apart, but are arranged in sections overlapping each other, so that there is a linear cup structure with a plurality of lines 10 . 12 formed. These lines can be arranged, for example, at a parallel distance from each other. In principle, these can also be wavy. Also a crossing or different angles of attack of the lines 10 . 12 is conceivable.

4 shows a schematic diagram for explaining the formation of a cup-shaped recess 8th , As explained, this depression may be the 2nd or 3rd order surface shape 2 . 3 form. As explained, this is done by means of a laser beam 10 , which is coupled, for example via a scanner assembly with an adjustable in several axes mirror or via a movable laser head. In the illustrated embodiment, the laser beam 10 obliquely to the vertical V of the guide surface 4 coupled. Accordingly, the center axis M of the recess 8th tilted. Through this laser beam 10 will - as in 4 shown strictly geometrically formed no cup shape, but a downwardly tapered, formed in the broadest sense cone or funnel-shaped structure.

5 shows a concrete solution, according to which the inventive method for producing a reflector headlamp is used for a low beam. Such a headlamp has a light source 12 For example, a H7 lamp, the light in the direction of a reflector 14 radiates, the reflection surface of the functional surface 4 forms according to the preceding embodiments. Accordingly, this functional surface 4 executed with surface shapes of 1st, 2nd and 3rd order. The surface shape of the first order forms the curvature of the reflector 14 out. The reflectance is determined according to the in 2 specified specifications executed. That from the light source 12 radiated light is at the reflector 14 or the functional area 4 towards a projection lens 16 deflected, which then radiates the substantially parallel dipped beam. The headlight is also still in the range of a leading edge with a beam aperture 18 carried out over which a portion A1 of the reflected light is absorbed. The unabsorbed portion of the light path is shown in the illustration 5 marked with the reference A2. The distribution of the light paths A1, A2 can in principle also be influenced by suitable design of the surface shape of the 2nd and 3rd order.

6 shows a variant of a functional area 4 a workpiece, such as a reflector 14 , This has the resulting from the machining production surface shape 1st order 1 which, for example, may again have a slightly wavy structure. As in 6 indicated schematically, can then by a subsequent laser processing, in which the dimensional accuracy the surface shape 1st order 1 is not or only insignificantly influenced, a suitable surface structure 2nd or 3rd order 2 . 3 be formed. In the illustration according to 6 These structures are arranged side by side. Of course, it is possible to have both the fine structure (3rd-order surface shape) and the macro-shape (2nd-order surface shape) in the same areas of the functional area 4 train.

As mentioned, of course, other than the above-described well-shaped depressions can be formed. Their structure can be varied almost arbitrarily depending on the respective requirements of the functional area.

As explained, it is also possible within the functional area 4 to form differently structured areas.

In the following, the method according to the invention is again generally explained.

By a machining process, in particular with certain cutting edge, in particular by milling, in particular with a Breitschlichtschneide a very smooth surface with high efficiency and very high reproducibility is achieved. In this case, a very high dimensional accuracy of the surface is achieved according to the surface shape of the first order, by favorable choice of parameters and by a Schneidrrundung the kinematic roughness (surface shape 2nd order) is reduced to a minimum and the roughness due to the cutting schartigkeit (surface shape 3rd order) by very smooth cutting (especially diamond) also reduced to a minimum.

This first processing step provides a very reproducible surface for the subsequent laser processing. The surface is property neutralized and can produce the maximum material-specific reflectance.

In this processing step, by bombarding the surface by means of a laser beam, a thermal surface treatment, in particular a removing machining is performed. There are recesses where the laser has melted material and this melt is optionally removed by an additional medium.

These depressions change the surface shape of the second order of the surface, wherein the dimensional accuracy (surface shape 1st order) can remain completely unchanged.

In particular, the reflectance can be influenced since the surface within a single depression (3rd order surface shape) has a certain roughness as a result of the melted and solidified surface.

The influence of the surface, in particular of the reflectance can also be effected by solidification of melt particles on the surface unaffected by the laser.

The influence of the surface in particular of the reflectance can also be effected by oxide formation due to the introduction of reaction enthalpy by the laser and the supply of oxygen by means of the Abblasmediums. The blow-off medium can also be varied so that different reaction products can be formed via different substances which have a color. Thus, the coloring of the surface can be influenced in a targeted manner.

As a rule, lasers are pulsed. A single pulse with a relatively high energy density results in a single well. Through several pulses, these wells can be deepened, it can also be influenced by the pulse duration and energy, the size and depth of the wells.

By machine axes or by a scanner unit, the laser beam can be moved one or more axes over the workpiece surface. By juxtaposing individual wells line structures can be generated.

The alignment of the lines according to the light paths acted upon by the part can influence the reflection or the shading in a targeted manner. It can be achieved a polarization of the light.

By angle of attack of the laser beam relative to the workpiece surface, the surface shape of the wells can be varied. Thus, reflection properties can be selectively changed depending on the direction.

The degree of reflection can be adjusted in a targeted manner by replacing the area fraction A 'by the area percentage A as a percentage. A 'is the surface area of the workpiece surface uninfluenced by the laser processing, A is the area fraction of the cells with their characteristic reflectance. Ideally, the ratio between the area percentages is proportional to the total integrated reflectance of the surface.

applications

To reduce friction or to increase friction, laser structures are applied to previously machined workpiece surfaces.

The specific orientation of the position of the individual constituents of the laser structure with respect to the surface shape of the previously machined surface can be used to optimize the properties of the surface.

An assignment of the laser structure to the surface shape of the second order can substantially increase the increase in the coefficient of friction of the surface, for example, by creating an imposition of thermally melted material exactly on the roughness peaks. This results in a strong positive interlocking when a friction partner is brought into engagement with this surface.

Very many surfaces, for example for everyday objects, have visual and haptic requirements. For example, the surface should look subjectively noble and feel noble. Uniformly glossy surfaces and matt surfaces are very common since this is based on a manufacturing process.

However, it is very difficult to produce surfaces which are shiny in their 3rd order surface form, rough in their 2nd order surface form, or smooth in their 2nd order surface form and rough in their 3rd order surface form.

Technically, for example, a "silk gloss" is very difficult to produce. This is characterized by a gloss of the surface shape of the third order with simultaneous roughness of the surface shape of the second order.

The advantage of the method combination according to the invention of machining, in particular by diamond broadsizing and laser processing, is to selectively influence the surface shape of the 2nd or 3rd order without influencing the other orders. Thus, for example, a satin gloss can be generated and the reflectance and other geometric, optical and haptic properties can be specifically controlled by the arrangement and shape of the laser pattern and by the surface density, depth and other parameters of the laser pattern.

For example, in optical devices inside a telescope tube, there is a requirement to reflect little light, for which a rough, non-reflective surface is useful.

On general workpieces with optical requirements, surfaces are often specifically influenced with regard to their optical properties. Shiny but also matt surfaces are desired.

Also in light emitting devices both surfaces are to be used, which purposefully reflect light and therefore have a high degree of reflection, as well as surfaces which should not reflect deliberately and should have a correspondingly low degree of reflection. Thus, optical components in headlamps can focus light in a targeted manner in the beam path resulting scattered light is absorbed and thus creates a defined bright-dark boundary of the illuminated area. This is an important requirement especially for the dipped beam of car headlights. The street should be illuminated and the oncoming traffic should not be dazzled which is achieved by specially shaped reflectors or radiation apertures.

The Applicant reserves the right to make claims on these applications.

Disclosed is a method for processing a workpiece surface, in which a first-order surface shape is formed by a first manufacturing method, for example a machining operation. The thereby adjusting surface shapes 2nd and / or 3rd order are then changed by a laser processing, the surface shape 1st order remains substantially unchanged. In this way, it is possible to form the first-order surface shape substantially independently of the third-order surface shape and / or the second-order surface shape, and thus to adjust the reflectance.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 4914747A [0021]
• DE 602004002043 T2 [0022]
• WO 002014165884 A2 [0023]
• DE 102010054858 A1 [0024]

Claims (17)

Method for processing a workpiece surface ( 4 ) whose surface shape is 1st order ( 1 ) by the function of the workpiece ( 6 ) and is formed by means of a shaping manufacturing process, wherein a surface shape of 2nd order ( 2 ) results from the processing parameters of the manufacturing process and relates to the macrostructure of the surface, which in turn has a 3rd order surface shape ( 3 ) in the form of a fine structure, characterized in that the surface shape of the first order ( 1 ) is produced by a first manufacturing method, for example a machining, and the resulting surface shape 2. ( 2 ) or 3rd order ( 3 ) is changed by a laser processing for setting a predetermined geometric surface property, such as a reflectance, wherein the surface shape is 1st order ( 1 ) remains essentially unchanged. Method according to claim 1, wherein the surface shape is 1st order ( 1 ) is influenced by the machining and is influenced by the subsequent laser processing at most to the extent that the surface shape 2nd and 3rd order ( 2 . 3 ) by the laser processing itself. Method according to one of the preceding claims, wherein the machining operation is a turning operation. A method according to claim 1 or 2, wherein the machining operation is a milling operation. Method according to one of the preceding claims, wherein the processing is a Breitschlichtbearbeitung, wherein the tool is formed with a spherical minor cutting edge or with several spherical minor cutting edges. Method according to one of the preceding claims, wherein the cutting edge or the cutting edges of the machining operation consist of diamond. Method according to one of the preceding claims, wherein the laser machining a shape change of the surface shape 2nd order ( 2 ) and / or order ( 3 ) leaves. Method according to one of the preceding claims, wherein the laser machining is eroding and leaves one or more recesses. Method according to one of the preceding claims, wherein the laser machining causes a chemical reaction in the workpiece material and leaves an oxide or another reaction product on the surface. Method according to one of the preceding claims, wherein the laser processing melts the workpiece material and melt particles are deposited on the surface. Method according to one of the preceding claims, wherein the laser beam is moved by a positioning device on the workpiece and thus can act at different locations. A method according to claim 11, wherein the laser beam is position-controlled in such a way at various points made to work that creates a pattern on the surface. The method of claim 12, wherein the pattern is a cup pattern or a line pattern. Method according to claim 12 or 13, wherein the pattern is associated with the second-order surface shape and / or the third-order surface shape. Method according to one of the preceding claims, characterized in that the shape of the depression is influenced by angular adjustment of the laser beam. Workpiece produced by a method according to one of the preceding claims. Workpiece according to claim 16, wherein this is a reflector ( 14 ).

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