Ultrasonic tool holder for a cutting tool and method for setting the working parameters of an ultrasonic tool holder

Abstract

An ultrasonic tool holder (100) for a cutting tool configured to be equipped on a machine tool for machining alloy workpieces, the ultrasonic tool holder (100) comprising an arbor (150) and a plurality of piezo-electric discs configured to receive electrical power, to convert electrical power into vibrations and to transmit them to the cutting tool, a first adapter (101) mechanically coupled to a first end of the arbor and a second adapter (102) mechanically coupled to a second end of the arbor (150). The first adapter (101) is configured to be selectively coupled to the cutting tool in order to hold the cutting tool during the machining of the alloy workpiece; the first adapter (101) is according to ISO 26623-1 or is ISO 26623-1 compatible. The second adapter (102) is configured to be coupled to the machine tool during the machining of the alloy workpiece.

Description

TITLEUltrasonic milling device for metallic manufacturing applicationsDESCRIPTIONTECHNICAL FIELD

[0001] The subject-matter disclosed herein relates to an ultrasonic tool holder for a cutting tool configured to be equipped on a machine tool, a milling machine comprising such ultrasonic tool holder and a method for setting the working parameters of such ultrasonic tool holder.BACKGROUND ART

[0002] Ultrasonic milling is a subtractive manufacturing process that removes material from the surface of a part through high frequency, low amplitude vibrations of a tool against the material surface. In particular, known ultrasonic machining uses abrasive slurry supply and diamond-coated multi-cutting tools to impress a high frequency vibration and erosion mechanism.

[0003] Ultrasonic state of the art technology is commonly used in hard / brittle material machining. Currently, ultrasonic machining can not be applicable to common metallic alloy materials (i.e. ductile materials) used in most of machining applications and / or with standard tools (e.g. tools with helical cutting edges) typically used.

[0004] Moreover, ultrasonic state of the art technology is applied only on small milling machines and current ultrasonic tool holder are configured to hold small cutting tools, typically using a small elastic / spring collet chuck. In fact, the commercial ultrasonic milling machines available on the market have a maximum machine connection size of 63 mm (diameter) and can hold tools with a maximum size of 10 mm (diameter).SUMMARY

[0005] Therefore, it would be desirable to have an ultrasonic tool holder which can be used for ultrasonic milling of ductile materials or metallic alloys workpieces, in particular steel alloys or aluminum alloys or titanium alloys or nickel and cobalt based superalloys, therefore extending this technology application to materials and dimensions used in most machining applications, in particular in aerospace, automobile and Oil&Gas field. Advantageously, it would be desirable to have an ultrasonic tool holder which is adapted to hold cutting tools with greater dimensions, in particular with greater diameter. Even more advantageously, it would be desirable to have a method for optimally setting the working parameters of an ultrasonic tool holder for a cutting tool according to the specific application.

[0006] According to an aspect, the subject-matter disclosed herein relates to an ultrasonic tool holder for a cutting tool configured to be equipped on a machine tool for machining alloy workpieces, the ultrasonic tool holder comprising an arbor with a plurality of piezo-electric discs configured to receive electrical power, to convert electrical power into vibrations and to transmit them to the cutting tool, a first adapter mechanically coupled to a first end of the arbor and a second adapter mechanically coupled to a second end of the arbor. The first adapter is configured to be selectively coupled to the cutting tool in order to hold the cutting tool during the machining of the alloy workpiece, the first adapter being according to ISO 26623-1 or is ISO 26623-1 compatible, and the second adapter is configured to be coupled to the machine tool during the machining of the alloy workpiece,

[0007] According to another aspect, the subject-matter disclosed herein relates to a milling machine for machining alloy workpieces comprising such ultrasonic tool holder.

[0008] According to still another aspect, the subject-matter disclosed hereinrelates to a method for setting the working parameters of an ultrasonic tool holder for a cutting tool configured to be equipped on a machine tool for machining alloy workpieces. The method comprises the steps of:A. Measuring effective amplitude of cutting tool tip displacement;B. Performing power input optimization of the ultrasonic tool holder so to identify at least an optimized power which minimizes the cutting forces;C. Generate a machining parameters database comprising the optimized power identified at step B.The machining parameters database generated at step C is used for setting the optimized power of the ultrasonic tool holder for machining the alloy workpiece.BRIEF DESCRIPTION OF THE DRAWINGS

[0009] A more complete appreciation of the disclosed embodiments of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:Fig. 1 shows a simplified longitudinal sectional view of an embodiment of an innovative ultrasonic tool holder according to the present disclosure, Figs. 2 show a lateral view and a frontal view of a first end of the innovative ultrasonic tool holder of Fig. 1, andFig. 3 shows a flow chart of an embodiment of an innovative method according to the present disclosure.DETAILED DESCRIPTION OF EMBODIMENTS

[0010] According to an aspect, the subject-matter disclosed herein relates to an ultrasonic tool holder for a cutting tool configured to be equipped on a machine tool for machining alloy workpieces. The ultrasonic millingtechnology is currently related to special tools and / or special machines, in particular with limited dimensions, and / or peculiar material applications such as hard / brittle materials. Therefore, there is the need of a simple system which allows to use ultrasonic milling technology even for alloy workpieces and with the possibility to use already existing big machine tools and standard cutting tools. The Applicant has thus identified a solution that allows ultrasonic milling technology to be made compatible with standard tools and commercial extension (in order to match a wider range of machining applications with multiple sets of standard tools).

[0011] According to another aspect, the subject-matter disclosed herein relates to a method for setting the working parameters of such ultrasonic tool holder. The cutting tool tip oscillation is a key parameter for the machining of metallic materials and depends on the power input received by the ultrasonic tool holder. According to the method of the present disclosure, the optimized power setting is chosen by measuring the effective amplitude of the cutting tool tip displacement and generating a database, advantageously with data from different cutting tools, material and cutting conditions, so to choose the optimized power setting on the basis of the database.

[0012] In particular, the Applicant has performed laboratory machining tests including comparative trials using systems for measuring instantaneous cutting forces and cumulative absorbed power and remaining tool life. Moreover, the actual frequency and oscillation amplitude of the tool tip has been measured as a function of the applied power, and a correlation of these parameters with cutting forces and tool wear has been performed, as well as a FEM simulation of orthogonal cutting mechanics influenced by ultrasonic vibration and a SEM analysis of the resulting chip morphology.

[0013] The tests and the study results showed that the oscillation amplitude of the ultrasonic vibration is a key parameter in reducing cutting forces when machining ductile materials, provided that the amplitude exceeds significantly higher values (e.g. +10 pm) compared to what is required for hard / brittlematerials (please note that milling machining has radial and tangential cutting forces, unlike drilling machining which involves primarily axial cutting forces). The technology development was therefore directed toward enhancing the mechanical, electrical, and electronic components of the standard system in order to achieve a maximum oscillation amplitude greater than 10 pm.

[0014] Reference now will be made in detail to embodiments of the disclosure, examples of which are illustrated in the drawings. The examples and drawing figures are provided by way of explanation of the disclosure and should not be construed as a limitation of the disclosure. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure without departing from the scope or spirit of the disclosure. In the following description, similar reference numerals are used for the illustration of figures of the embodiments to indicate elements performing the same or similar functions. Moreover, for clarity of illustration, some references may be not repeated in all the figures.

[0015] When introducing elements of various embodiments the articles “a”, “an”, “the”, and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including”, and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.

[0016] Referring now to the drawings, Fig. 1 illustrates, for example and without limitations, a simplified cross-section view of an embodiment of the innovative ultrasonic tool holder 100. The ultrasonic tool holder 100 is suitable for holding a cutting tool configured to be equipped on a machine tool for machining alloy workpieces.

[0017] The ultrasonic tool holder 100 comprises an arbor 150 having a first end and a second end. A first adapter 101 is mechanically coupled to the first end of the arbor 150 and is configured to be selectively coupled to the cutting tool in order to hold the cutting tool during the machining of the alloy workpiece. It is to be noted that the cutting tool may be attached to or detachedfrom the first adapter 101, so that the cutting tool may be interchanged according to the machining to be performed on the alloy workpiece.

[0018] The first adapter 101 is according to ISO 26623-1 or is ISO 26623-1 compatible. For example, the first adapter 101 may be compatible with CAPTO-6 standard with a trilobate geometry (see for example Fig. 2B). In particular, the first adapter 101 is configured to accommodate tools of any size, enhancing therefore the application of ultrasonic milling technology to workpieces having materials and dimensions used in particular in aerospace, automobile and Oil&Gas field, which are mounted on an ISO 26623-1 tool holder. In other words, the first adapter 101 is the female part of a coupling with an ISO 26623-1 interface.

[0019] It is to be noted that the first adapter 101 may be directly coupled to the cutting tool if it has a ISO 26623-1 coupling, in particular the male part of a coupling with an ISO 26623-1 interface, or the cutting tool may be mounted on an connector (i.e. a standard - non ultrasonic - tool holder) having a ISO 26623-1 coupling, in particular the male part of a coupling with an ISO 26623-1 interface.

[0020] A second adapter 102 is mechanically coupled to the second end of the arbor 150 and is configured to be coupled to the machine tool during the machining of the alloy workpiece. Advantageously, the second adapter 102 may be interchangeable, so that it may fit common Numerical Control (=NC) milling machines and is interchangeable with any standard spindle interface, for example with HSK100 standard.

[0021] The ultrasonic tool holder 100 further comprises a plurality of piezo¬ electric discs 160, in particular housed in the arbor 150, configured to receive electrical power, to convert electrical power into vibrations and to transmit them to the cutting tool. In particular, the vibrations transmitted to the cutting tool are an axial high frequency motion of the cutting tool, in particular in a range of 5-25 kHz. Advantageously, the ultrasonic tool holder 100 comprises six piezo-electric discs 160 (please note that Fig. 1 shows only four piezo electric discs 160). It is to be noted that, according to the tests performed by the Applicant, increasing the number of discs allows for the increase inelectrical power needed to operate (i.e. vibrate) tools having larger size, in particular with respect to the tools which can be hold by commercial ultrasonic milling machines available on the market.

[0022] Advantageously, with non-limiting reference to Fig. 2A, the ultrasonic tool holder 100 further comprises a connector 170 electrically coupled with the plurality of piezo-electric discs 160 and to an external AC power source. In particular, the connector 170 is configured to receive electrical power from the external AC power source. Advantageously, the connector 170 is further configured to transfer to the piezo-electric discs 160 the electrical power which determines the vibration of the plurality of piezo-electric discs 160.

[0023] It is to be noted that the connector 170 and the plurality of piezo¬ electric discs 160 have been studied and adjusted according to the present disclosure so to reach the proper amplitude of cutting tool tip displacement required for the ultrasonic milling of ductile materials or metallic alloys workpieces. The Applicant has in fact determined that, with the ultrasonic milling machines currently available in the state of the art, the process cannot be carried out. This is because increasing the current supplied to the ultrasonic machining equipment would cause the connectors / generators to burn out, whereas using the current for which such machines were originally designed would result in an oscillation amplitude insufficient to provide any benefit without an appropriate setup and the necessary components (such as the piezoelectric discs) to generate the tool tip oscillation and a proper coupling enabling the use of existing large machine tools for machining large workpieces and wide surface areas.

[0024] Specifically, there are no connect! ons / adaptors currently available between ultrasonic spindles and the ISO 26623-1 interface. The Applicant’s activity has been specifically aimed at filling this technological gap by developing an ultrasonic tool holder whose architecture is compatible with the ISO 26623-1 connection standard.

[0025] Advantageously, the connector 170 is further electrically coupledwith an ultrasonic amplifier (not shown in the figures). As it will be apparent from the following, the ultrasonic amplifier is in turn electrically coupled to the external AC power source. In particular, the ultrasonic amplifier is configured to amplify (i.e. increase the magnitude of) the electrical power received by the external AC power source before being received by the connector 170.

[0026] Even more advantageously, the ultrasonic amplifier is further electrically coupled with an amplifier power setting unit. In particular, the power setting unit is configured to set the power and frequency of vibrations of the plurality of piezo-electric discs 160, in particular according to optimized parameters taken from a database.

[0027] Advantageously, the arbor 150 further comprises an internal channel 180 configured to circulate a fluid, in particular a fluid which has cooling and / or lubricating properties, which promote machining.

[0028] According to another aspect, the subject-matter disclosed herein refers to a milling machine for machining alloy workpieces comprising such ultrasonic tool holder 100.

[0029] According to still another aspect, the subject-matter disclosed herein refers to a method 200 for setting the working parameters of an ultrasonic tool holder 100 for a cutting tool configured to be equipped on a machine tool for machining alloy workpieces.

[0030] With non-limiting reference to Fig. 3, the method 200 comprises the steps ofA. Measuring 210 effective amplitude of cutting tool tip displacement;B. Performing 220 power input optimization of the ultrasonic tool holder 100 so to identify at least an optimized power which minimizes the cutting forces;C. Generate 230 a machining parameters database comprising the optimized power identified at step B.The machining parameters database generated at step C is used for setting 240 the optimized power of the ultrasonic tool holder 100 for machining the alloy workpiece.

[0031] Advantageously, step A is performed using a laser high frequency gauge, in particular with a frequency in the range 20-85 kHz.

[0032] Advantageously, step B is performed by varying the power input of the ultrasonic tool holder 100, in particular for retrieving the effective wave form of the cutting tool amplitude vibrations.

[0033] Advantageously, steps A and B are performed for a plurality of cutting tools and / or a plurality of alloys and / or a plurality of machining conditions.

[0034] Advantageously, steps A and B are performed for a plurality of cutting tools having different diameters and / or different numbers of cutting edges and / or different characteristic angles.

[0035] Advantageously, steps A and B are performed for a plurality of alloys, such as ASTM A182, ASTM A350, ASTM A705, AISI 316, ASTM B637 Nimonic, Inconel 718, Inconel 625, Hastelloy X.

[0036] Advantageously, steps A and B are performed for a plurality of machining conditions, in particular for a plurality of geometric cutting parameters, for example for different radial engagements and / or different depths of cut and / or different lead angles and / or different ramp angles.

[0037] Advantageously, steps A and B are performed for a plurality of machining conditions, in particular for a plurality of dynamic cutting parameters, for example for different cutting speeds and / or different feed rates.

Claims

CLAIMS1. An ultrasonic tool holder (100) for a cutting tool configured to be equipped on a machine tool for machining alloy workpieces, the ultrasonic tool holder (100) comprising an arbor (150), a first adapter (101) mechanically coupled to a first end of the arbor (150) and a second adapter (102) mechanically coupled to a second end of the arbor (150), wherein the ultrasonic tool holder (100) further comprises a plurality of piezo-electric discs (160) configured to receive electrical power, to convert electrical power into vibrations and to transmit them to the cutting tool,wherein the first adapter (101) is configured to be selectively coupled to the cutting tool in order to hold the cutting tool during the machining of the alloy workpiece,wherein the first adapter (101) is according to ISO 26623-1 or is ISO 26623-1 compatible,wherein the second adapter (102) is configured to be coupled to the machine tool during the machining of the alloy workpiece.

2. The ultrasonic tool holder (100) of claim 1, wherein the vibrations are an axial high frequency motion of the cutting tool, in particular in a range of 5-25 kHz.

3. The ultrasonic tool holder (100) of claim 1, wherein the first adapter (101) is interchangeable.

4. The ultrasonic tool holder (100) of claim 1, wherein the arbor (150) comprises an internal channel (180) configured to circulate a fluid, in particular a fluid which has cooling and / or lubricating properties.

5. The ultrasonic tool holder (100) of claim 1, wherein the ultrasonic tool holder (100) further comprises a connector (170) electrically coupled with the plurality of piezo-electric discs (160) and to an external AC power source,wherein the connector (170) is configured to transfer to the plurality of piezo-electric discs (160) the electrical power which determines the vibration of the plurality of piezo-electric discs (160).

6. The ultrasonic tool holder (100) of claim 5, wherein the connector (170) is further electrically coupled with an ultrasonic amplifier configured to amplify the electrical power received by the external AC power source.

7. The ultrasonic tool holder (100) of claim 6, wherein the ultrasonic amplifier is further electrically coupled with an amplifier power setting unit,wherein the amplifier power setting unit is configured to set the power and frequency of vibrations of the plurality of piezo-electric discs (160).

8. The ultrasonic tool holder (100) of claim 1, comprising six piezo-electric discs (160).

9. A milling machine for machining alloy workpieces comprising the ultrasonic tool holder (100) of claim 1.

10. Method (200) for setting the working parameters of an ultrasonic tool holder (100) for a cutting tool configured to be equipped on a machine tool for machining alloy workpieces, the method (200) comprising the steps ofA. Measuring (210) effective amplitude of cutting tool tip displacement;B. Performing (220) power input optimization of the ultrasonic tool holder (100) so to identify at least an optimized power which minimizes the cutting forces;C. Generate (230) a machining parameters database comprising the optimized power identified at step B;wherein the machining parameters database is used for setting (240) the optimized power of the ultrasonic tool holder (100) for machining the alloys workpiece.

11. The method (200) of claim 10, wherein step A is performed using a laser high frequency gauge.

12. The method (200) of claim 10, wherein step B is performed by varying the power input of the ultrasonic tool holder (100), in particular for retrieving the effective wave form of the cutting tool amplitude vibrations.

13. The method (200) of claim 10, wherein steps A and B are performed for a plurality of cutting tools and / or a plurality of alloys and / or a plurality of machining conditions.

14. The method (200) of claim 13, wherein the plurality of machining conditions comprises different geometric cutting parameters and / or different dynamic cutting parameters.

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