DE102005009030A1 - Chipping tool for micro-precision work has shaft region with narrow part adjacent to cutting region - Google Patents

Abstract

The chipping tool (1) has a cutting region (2) to machine the workpiece (10) and an adjacent shaft region, with a narrow part adjacent to the cutting region. The shaft region narrows to a minimum diameter point (d), which may be a nominal diameter equal to the nominal diameter (D) of the cutting region, narrowing from this point onwards.

Description

The The invention relates to a cutting tool, in particular for the micromachining and precision mold construction The preamble of claim 1. In particular, the invention relates micro-machining with end mills, Nose end mills or grinding pins smallest diameter in the range between 0.1 and 1 mm.

background the invention

• • die hochpräzise Mikrostrukturierung makroskopischer Bauteile (z. B. Ferrules, opto-elektronische Kopplungsbausteine) und Komponenten komplexer Mikrosysteme,
• • die Herstellung von Abformwerkzeugen für die Massenfertigung mikrotechnischer Produkte (z. B. mikrostrukturierte Formnester von Mikrospritzgießwerkzeugen für die Massenfertigung mikrofluidischer Systeme, Mikroprägestempel),
• • die direkte Herstellung mikro- und feinwerktechnischer Produkte als Prototypen oder in Klein- und Mittelserien (z. B. mikromechanische Komponenten der minimal-invasiven Chirurgie) und Komponenten komplexer Mikrosysteme (wie z. B. Mikroreaktoren, Mikromischer, Mikroantriebe oder bio-analytische Mikrochips),
• • die Oberflächenfeinbearbeitung von funktionalen Flächenelementen von Kleinstbauteilen (z. B. optoelektronische Kopplungsbausteine, Gehäuse für hybride Mikrosensoren),
• • die hochpräzise Mikrostrukturierung von komplexen Feinbauteilen mit erforderlicher Komplettbearbeitung in einer Aufspannung (z. B. Stents).

It is known to use machining processes such as milling and grinding for the high-precision production of complex cavities and functional surfaces in micro and precision mold making. In addition to the direct production of microcomponents, such processes represent an important link in the process chain for the mass production of micro and precision components and offer decisive advantages in terms of their applicability and cost-effectiveness. Depending on the processing technology, a high degree of geometry complexity and flexibility with regard to the material spectrum to be processed can be achieved with cutting processes. The following microtechnical application fields have great economic relevance for the use of high-precision machining and ablation processes:

• • the high-precision microstructuring of macroscopic components (eg ferrules, optoelectronic coupling components) and components of complex microsystems,
• The production of impression tools for the mass production of microtechnical products (eg microstructured mold cavities of micro injection molding tools for mass production of microfluidic systems, micro stamping dies),
• • the direct production of micro and precision engineering products as prototypes or in small and medium series (eg micromechanical components of minimally invasive surgery) and components of complex microsystems (such as microreactors, micromixers, microdrives or bio-analytical microchips )
• The surface finishing of functional surface elements of very small components (eg optoelectronic coupling modules, housing for hybrid microsensors),
• • The high-precision microstructuring of complex fine components with complete machining required in one set-up (eg stents).

When Microzerspanbare materials come in particular non-ferrous metals, plastics, Graphite and steel materials with a hardness up to 58 HRC are used. The current process limits are based on the quality of the milling and drilling tools and the machine-side restrictions. They are coated (TiN, TiAlN, TiCN) carbide milling tools with a diameter of at least 0.1 mm as well as drilling tools with Diameter to a minimum of 0.07 mm known.

The high-precision milling of microstructures in particular depends on a large number of process input parameters. The machining parameters of the cutting speed v _c and of the tooth feed f _z and the infeed variables cutting depth a _p and engagement width a _{e are of} particular relevance. Furthermore, the properties of the workpiece to be produced, such as the complexity of the geometry or the mechanical properties of the workpiece material, also belong to the process input parameters. An important influencing factor is the configuration of the machine tool and to what extent it meets the requirements for the production of very small structures. The totality of these factors is reflected in the component quality.

limiting for the Wide application of high precision milling in the field of microtechnology is in addition to the machine technology in particular the quality and lifetime of available Milling tools. It has been shown that the machining processes are not in the Dimensions manageable are, as it is quality, Precision and cost conditions require. The high-precision milling machining for the Manufacture of micro products is therefore currently still restrained used.

• • die Schneidkanten weisen Verrundungen mit einem Radius von 2 μm bis 5 μm auf und sind teilweise durch mikroskopische Ausbrüche gekennzeichnet,
• • die Beschichtungen weisen inhomogene Bereiche auf, die einen adhäsiven Verschleiß des Werkzeugs unterstützen,
• • die makroskopische Gestalt bewirkt einen Rundlauffehler, der in Abhängigkeit vom Werkzeug-hersteller zwischen 1 μm und etwa 10 μm betragen kann.

In particular, a prior art analysis of high precision milling machining technology shows that both the design and fabrication of micromilling tools in the 0.1mm to 1mm diameter range are based on the scaling of conventional miniaturized tools. The currently available end mills are usually made of a sintered finest grain carbide blank. If required, the tools are also surface-treated with a ceramic multi-layer hard coating of TiN, TiCN or TiAlN. The production of the surfaces and edges of the designed with few exceptions as a double cutter tools is done by a grinding. This results in three major weaknesses:

• • The cutting edges have fillets with a radius of 2 μm to 5 μm and are partially pierced characterized by microscopic outbreaks,
• The coatings have inhomogeneous regions which promote adhesive wear of the tool,
• • The macroscopic shape causes a concentricity error, which can be between 1 .mu.m and about 10 .mu.m, depending on the tool manufacturer.

It has thus shown that a pure scaling of known tool geometries in the miniaturized area is insufficient to meet the requirements of the micromachining process.

Task of invention

Of the present invention is based on the object, a machining Tool especially for the Micro and precision mold making to disposal to provide, which is characterized by a novel geometry, the the disadvantages and limitations of the prior art largely eliminated.

Summary the invention

These Task is achieved by a cutting tool with the features of claim 1 solved. preferred and advantageous embodiments of the invention are specified in the subclaims.

The solution according to the invention is based after that on the thought that the shank area of a chipping Tool forms a taper adjacent to the cutting area, wherein the shaft area is minimized to a point or area Tapered diameter, i.e. gradually and is getting narrower.

This allows it, the cutting length on the material-dependent typical depth of cut plus to reduce safety against wear. Training prevents or reduces the shaft area with a taper about that In addition, the contact of the shaft portion with a machined Workpiece and thus an additional Stress due to frictional forces. The solution according to the invention provides a cutting tool available that is characterized by a high load capacity, long service life as well a process-safe operational capability in precision machining distinguished.

By the reduction of the cutting area on the tool tip and the rejuvenation of the shaft is another advantage of the influence of the helix angle on tool stability - different as with conventional Micro mills - eliminated. There are twist angles in a wide angle range in particular between 15 ° and 45 ° without problems realizable.

In In a preferred embodiment, the shaft region is adjacent at the cutting area a nominal diameter equal to the Nominal diameter of the cutting area is. It rejuvenates the Shank area from this nominal diameter to the point or area of minimum diameter. The diameter of the shaft Thus, adjacent to the cutting area, it is initially substantially identical with the diameter of the cutting area.

Of the Minimum diameter of the cutting area is preferably the same the core diameter of the tool. The core diameter d is different of the nominal diameter D, also referred to as cutter diameter, by the depth of the cutting edge or the depth of the spiral groove, the on the cutting edge is adjacent.

The core diameter d is decisive for the stability of the tool. Its minimum is limited by the material-dependent micro-cutting geometry and by the depth of the spiral groove. The geometry of the swirl groove is in turn determined from the rake angle γ, the clearance angle α, the wedge angle β and from the chip space dependent on the tooth advance f _z and the cutting depth a _p . As will be explained, there is a theoretical optimum of the core diameter for a given nominal diameter.

In a preferred embodiment of the invention, the swirl groove of the tool extends from the Cutting area up to the shaft area. In this case, the cutting edge in the cutting area, which serves for the machining of a workpiece, a maximum. Depth of the swirl groove. The depth of the spiral groove is reduced to zero in the shaft area up to the point of minimum depth. The tapering of the shaft region in this embodiment is thus associated with a reduction in the depth of the swirl groove, while the core diameter of the shaft region remains unaffected by the taper.

Prefers the diameter of the shaft area decreases behind the point or area minimum diameter again. The shaft forms in the Area of increasing diameter no longer cutting out. It results at least in a local area adjacent to the cutting area an arcuate rejuvenation and a subsequent one Diameter increase of the shaft area.

The Tool cutting can basically have any shape.

Of the Shank region may in preferred embodiments of the form of a Arc, a hyperbola or other conic. Particularly preferably, the taper of the shank region follows the shape of a circular arc, because such a form in a machine tool easy to program and manufacture. It is preferred provided that the circular arc firstly the circumferential point of minimum diameter of the shaft portion tangentially touched. Second, the touches Arc a cone of the shaft area, this on his the end portion facing away from the cutting area and adjacent to the circular area formed. Third, the circular arc intersects the point of the shaft region, in the immediately adjacent to the cutting area, the taper in Direction of the minimum diameter begins. Through these three conditions the radius is geometrically uniquely determined. He depends on the effective tool length l, the core diameter d of the shank and the nominal diameter of the cutting area D.

It It has already been pointed out that the tool according to the invention realize different helix angles in a wide angular range can. The helix angle ensures a gentle tool entry during machining. Its minimum results from sanctions of the tool manufacturing process. For example can in a tool according to the invention produced by grinding with a nominal diameter D of 0.5 mm and an effective tool length l of 2.5 mm, a minimum helix angle of 15 ° can be realized. Prefers The tool can realize a helix angle between 15 ° and 45 °.

Of the Nominal diameter of the cutting area is for example in the range between 0.05 and 2.0 mm, the effective tool length is for example, between 0.25 and 10 mm. The ratio of nominal diameter to effective tool length, also as an aspect ratio is preferably between 1: 2 and 1: 7. The realization greater aspect ratios is increasingly difficult because of the bending moments that occur. The inventive cutting Tool and provided by this entitlement favorable geometry enable the realization of a big one Aspect ratio.

In In a preferred embodiment, the tool is made in one piece formed the cutting area and the shaft area. This is special then the case when the tool is small, for micro and precision mold making having suitable dimensions. It is noted, however, that the tool geometry according to the invention also on larger tools can be realized. In particular, it can be provided for this case be made separately, the cutting area and the shaft area and then connect with each other or the tool in a different way to train in several parts. For larger dimensions of the tool, it is also possible that the cutting area and the shaft portion are made of different materials. Also can the cutting area and / or the shaft area taken alone be multi-part and / or consist of several materials.

The inventive tool is preferred as a micro end mill or as a face radius cutter (tools with a geometrically determined cutting edge) or as a grinding pin (tools with a geometrically indefinite edge).

description preferred embodiments the invention

The Invention will be described below with reference to the figures an embodiment explained in more detail. It demonstrate:

1 a side view of a tool according to the invention and a workpiece in a sectional view, which is processed with the tool;

2 a cross section of the tool of 1 cut along the line BB;

3 a representation of a tool connected to a drive motor in a lateral view, wherein the 1 the area A of the tool 3 reproduces;

4 in a lateral perspective view of an embodiment of an end mill according to the prior art;

5 a section through the end mill of the 4 along the line AA;

6 a representation of the dependence of the bending moments occurring at an end mill by the process forces from the distance to the tool tip;

7 in a lateral perspective view of an embodiment of an end mill according to the invention;

8th a section through the end mill of 7 along the line BB;

9 the dependence of the tool deformation u on the tool core diameter d for a given nominal tool diameter D and a given effective tool length l; and

10a - 10f Embodiments of various embodiments of a tool according to the invention with variation of the helix angle φ _A , the core diameter d and the nominal diameter D.

The 1 shows a trained as an end mill micro mill 1 , which at the tool tip a cutting area 2 and then a shaft area 3 formed. The tool is used for machining a workpiece 10 ,

The cutting area 2 forms a cutting edge 4 from under a certain helix angle φ _A in the cutting area 2 is executed. The outer contours of the cutting edge 4 determine according to the 2 the nominal diameter D of the cutting area 2 or the tool 1 , The relative to the nominal diameter D smaller core diameter d of the cutting edge 2 is determined by the micro-cutting geometry of the tool and, as can be seen, results from the nominal diameter minus the depth of the swirl groove.

The cutting area 2 has a maximum cutting length a, which results from the maximum, application-dependent cutting depth plus a security against wear.

The 1 further shows the application-dependent effective tool length l, which is also referred to as the target length. The target length l minus the maximum cutting length a he gives the effective length b of the shaft portion 3 , It gives the area of the shaft 3 on, which can always come into contact with the workpiece at a workpiece machining. Because the shaft area 3 protrudes from the workpiece, the total shaft length is greater than the effective shaft length b.

The shaft area 3 tapers from a maximum diameter directly adjacent to the cutting area 2 to a minimum diameter equal to the core diameter d of the tool. Thereafter, the shaft area widens 3 again, where he can take a much larger diameter outside the workpiece.

In the area of the effective length b of the shaft area 3 the outer shape of the stem preferably follows a circular arc of radius r. The circle center M _r is not drawn to scale. The circular arc with the radius r is tangent to the circumference of the shaft area at the point 31 lowest diameter d. Furthermore, the circular arc touches a point 32 The shaft 3 at the transition to the cutting area 2 trains, also tangential. The shaft 3 points at the transition to the cutting area 2 the same nominal diameter as the cutting area 2 on. Third, the circular arc affects the end point of a cone 33 which the shank forms adjacent to the arcuate area, cf. also 3 , These values clearly define the radius r.

With the named quantities, the radius r and its center position M _{r are} calculated with the coordinates dinates x _r and y _r as follows:

The 3 shows the entire tool. It can be seen that at the circular arc-shaped shaft region, the conically enlarging region 33 followed. The conical area 33 forms at its rear end a power transmission surface 34 out with a rotary drive element 5 is connectable, so that shank 3 and cutting edge 2 can be set in rotational motion.

It should be noted that in the 1 illustrated processing state of the workpiece 10 by a multiple processing with the tool 1 originated. The illustrated groove or milling edge has arisen by multiple milling of the workpiece perpendicular to the plane of the drawing, the state shown indicating the maximum depth of cut or target length l.

The 4 to 7 illustrate the mechanical advantages of the tool described 1 , The 4 shows a conventional end mill 6 with a long cutting area 60 , At the tool tip, a force F _c engages transversely. The 6 shows the resulting bending moment as a function of the distance to the tool tip, on which the transverse force acts. Naturally, the bending moment increases linearly with increasing distance.

Particularly problematic in terms of the risk of breakage of the tool is the area of the tool that has to absorb the largest bending moment when compared to other areas of the same or reduced diameter. This area lies with the tool of 6 in the plane defined by the section along the arrows AA plane, since here the distance to the tool tip is greatest before the thickness of the tool then increases with an even greater distance. According to the sectional view of 5 the workpiece is not symmetrical in the area in question due to the existing tool cutting edge. This further increases the risk of undesired breakage.

The 7 shows a tool 1 that according to the 1 is formed. At the cutting area 2 Accordingly, a tapered shaft area is adjacent 3 at. It should be noted that - as in the 7 shown - the cutting edge 4 of the cutting area 2 quite in, the tapered area of the shaft 3 can extend. However, the depth of the swirl groove in the shaft area decreases 3 continuously decreases and reaches the point 31 of the smallest diameter d the value zero. The taper of the shaft area is thus by a constant reduction of the depth of the swirl groove 4 achieved, the core diameter remains constant.

In the point 31 smallest diameter d are the maximum bending moments occurring when a transverse force F _c is applied, since the diameter of the shaft increases again with a further distance from the tool tip.

It can now be seen that the point 31 smallest diameter d opposite the workpiece 6 of the prior art is moved much closer to the tool tip, so that the bending moments occurring are reduced in the weakest region, see. 6 , In addition, the shank in this area according to the 8th circular, ie symmetrical, whereby the risk of breakage is further reduced.

from that results in a significant advantage of the novel tool geometry. By moving the minimum, circular cross-section closer towards the tool tip will attack at the minimum cross section Bending moments reduced and better absorbed. Furthermore be through the tangential transition between cutting area and shaft area geometrically caused Voltage peaks in the heavily loaded transition area excluded.

The 9 shows the dependence of the tool deformation u of the tool core diameter d at a given nominal diameter D, in the example shown by D = 0.5 mm, and a vorgege correspond effective tool length l, in the example shown by 2.5 mm. It can be seen that the tool deformation u reaches a minimum at a certain core diameter d (at 0.4 mm). This core diameter is accordingly preferably realized.

there is generally true that simulation studies all parametric specified geometry features of each tool model varies and in interdependence can be optimized.

The 10a -F show an experimental verification of the described new tool geometry. Among other things, micromotors with D × l = 0.5 mm × 2.5 mm and D × l = 0.1 mm × 1 mm were produced. For tools with diameter D = 0.5 mm, the core diameter d was also varied in accordance with theoretical considerations. Also, the helix angles φ _{A were} varied. All test tools were coated with TiAlN.

A Pilot series with microfrots conventional Geometry and an effective tool length of l = 1.5 mm was in used a reference experiment. The standard criterion was a average roughness depth of Rz = 5 μm defined and the experiments were broken or broken tool Deterioration of the workpiece surface finished.

It On the one hand, it was possible to significantly reduce the risk of tool breakage be detected by the novel tool geometry. The tool failure limited now on signs of wear at the cutting edges. This phenomenon can only through adapted cutting materials and / or coating systems be counteracted. On the other hand, a process-reliable increase of the Longevity achieved by almost 30%.

It is also clear that an increase in the core diameter d does not necessarily contribute to an increase in the stability of the micro mill and thus to an improvement in the work result. This deterioration of the surface results from the lower stability of the tool with higher core diameter d, as already the tool deformations in the parameter study to the core diameter d according to the 9 have shown.

About the Life examinations were after gradual hardening of the Test material PM X190CrVMo 20 Reference structures milled. The Process parameters were identical to those of the bench tests. It could now with a micromillers with d = 0.5 mm at a hardness of 62 HRC an aspect ratio the groove of 5: 1 can be achieved. Furthermore, it is possible microstege almost gradfrei to produce in different forms. With these editing results has been demonstrated that the limits known in the art micro-machining with end mills made of carbide clearly exceeded can be.

By The present invention, it is possible with the Mikrozerspanung with carbide tools just for applications such. As the tool and mold for the mass production of micro parts for consumer products or the Direct production of micromechanical components made of steel.

The present invention limited not on the described embodiments, the only to be understood by way of example. In particular, an implementation the invention in end mills, Stirnradiusfräsern and Grinding, micro-machining of a wide variety of materials (such as plastics, graphite, unalloyed steels, stainless steels, others Tool steels, Composites) as well as for Various cutting materials (such as HSS, HM, PCD, cermet) possible.

Claims (19)

A cutting tool, in particular for the micro- and precision mold making, comprising - a cutting area, which serves for the machining of a workpiece, and - a shank area adjoining the cutting area, wherein - the shank area with means for providing a rotational movement of the cutting area and the shank area is connected or connectable, characterized in that the shaft region ( 3 ) adjacent to the cutting area ( 2 ) forms a taper, wherein the shaft region ( 3 ) tapers to a point or area of minimum diameter (d). Tool according to claim 1, characterized in that the shank region ( 3 ) adjacent to the cutting area ( 2 ) has a nominal diameter equal to the nominal diameter (D) of the cutting area, and tapers from said nominal diameter (D) to the point or area of minimum diameter (d). Tool according to claim 1 or 2, characterized that the minimum diameter (d) is equal to the core diameter of the Tool is. Tool according to one of claims 1 to 3, characterized in that the swirl groove of the tool is in the shaft region ( 3 ), wherein the swirl groove in the cutting area ( 2 ) has a maximum depth and reduces the depth of the swirl groove in the shank region to zero to the point of minimum diameter. Tool according to claim 4, characterized in that the taper of the shank region ( 3 ) is associated with the reduction of the depth of the swirl groove, while the core diameter (d) of the shaft region ( 3 ) is unaffected by the rejuvenation. Tool according to one of claims 1 to 5, characterized in that the diameter of the shaft portion ( 3 ) increases again behind the point or area of minimum diameter. Tool according to claim 6, characterized in that the shaft ( 3 ) no longer forms a cutting edge in the region of increasing diameter. Tool according to one of claims 1 to 7, characterized in that the taper of the shaft portion ( 3 ) takes place arcuately. Tool according to claim 8, characterized in that the taper of the shank area ( 3 ) follows the shape of a circular arc. Tool according to claim 9, characterized in that the shank region has a conically shaped region ( 33 ), which adjoins the arcuate area. Tool according to claim 10, characterized in that the circular arc the peripheral point ( 31 ) minimum diameter (d) of the shank area ( 3 ), the cone ( 33 ) of the shaft region ( 3 ) at the transition to the arcuate region and the peripheral point ( 32 ) at the transition between the cutting area ( 2 ) and the shaft area ( 3 ) touched tangentially. Tool according to at least one of the preceding claims, characterized in that the tool ( 1 ) has a helix angle between 15 ° and 45 °. Tool according to at least one of the preceding claims, characterized in that the nominal diameter (D) of the cutting area ( 2 ) is between 0.05 and 2 mm. Tool according to at least one of the preceding Claims, characterized in that the effective tool length (l) between 0.25 and 10 mm. Tool according to at least one of the preceding Claims, characterized in that the ratio of nominal diameter (D) to effective tool length (l) is between 1: 2 and 1: 7. Tool according to at least one of the preceding claims, characterized in that the tool ( 1 ) in one piece from the cutting area ( 2 ) and shaft area ( 3 ) is formed. Tool according to at least one of the preceding claims, characterized in that the tool ( 1 ) is designed as end mill. Tool according to at least one of claims 1 to 17, characterized in that the tool ( 1 ) is designed as Stirnradiusfräser. Tool according to at least one of claims 1 to 17, characterized in that the factory stuff ( 1 ) is designed as a grinding pin.