Patent Publication Number: US-2009234490-A1

Title: Smart Machining System and Smart Tool Holder Therefor

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority from U.S. Provisional Patent Application Ser. No. 61/037,033 filed Mar. 17, 2008, the disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Field of the Invention 
     The invention relates generally to tool holder assemblies, and, more particularly, to smart tool holders for use with machine tool platforms. The invention also relates to a smart tool assembly for use with a machine tool platform. The invention further relates to a smart machining system employing a smart tool holder. 
     2. Background Information 
     Annual U.S. expenditures on machining operations are estimated to be in excess of $200 billion. Accordingly, there exists a great demand for improved cutting tools and machining methods in order to minimize such expenditures. In December 2007, the National Institute of Standards and Technology (NIST) hosted a workshop on “Smart Machine Tools” organized by the Integrated Manufacturing Technology Initiative (IMTI) association to “assess the needs, opportunities, and requirements for increasing the intelligence of machine tools for material removal.” Two of the top priorities, as voted by the participants, were to establish physics based process models for a smart machine tool testbed and to capture and understand the information necessary to determine machine conditions. 
     In order for a machining monitoring system, such as an end mill condition monitoring system, to be widely accepted by industry, the deployment onto shop floor machinery must be low cost, noninvasive, and cause no disruption of the machining envelope. However, a monitoring system typically requires data collection sensors to be located on or in the machine. Unfortunately, many sensor types are high in cost, are invasive to the machining envelope, and/or are difficult to deploy. 
     Historically, the ability to record in-process data about the response of the tool tip has been limited to data collected from sensors at locations physically distant from the cutting process. Often, these sensors are mounted on the material workpiece or the machine spindle. However, the complexity of the end milling system causes noisy transmission of vibration between the tool tip and the location of a traditionally mounted stationary sensor. This fact increases the difficulty of analyzing the dynamic motion of the tool tip and decreases the resolution on subtle phenomena of interest. In order to fully understand dynamic end milling problems such as tool chatter, wear, or run out, it is necessary to observe the tool tip response characteristics at their source during the cutting process. 
     A known instance of a non-invasive sensor is a power monitor located on a spindle drive motor of a machine tool platform. Although non-invasive and cost effective, sensors such as power monitoring do not provide sufficient bandwidth to capture many important details of the machining process. Additionally, many known condition monitoring techniques require sensors such as bed-type dynamometers which are largely impractical. From a research perspective, such sensor types are necessary for the development and validation of robust system models. However, in real world application, the sensing approach should accommodate cost, ease of setup, and performance. 
     There is, therefore, room for improvement in monitoring of machining systems, particularly in monitoring of cutting tools and the equipment used therefor. 
     SUMMARY OF THE INVENTION 
     These needs and others are met by embodiments of the invention, which are directed to a smart tool holder for use with a machine tool platform, a smart tool assembly for use with a machine tool platform, and a smart machining system employing a smart tool holder. 
     As one aspect of the invention, a smart tool holder is for use with a machine tool platform. The smart tool holder comprises a body having a first end and an opposite second end, a processor disposed with the body, and a transceiver disposed with the body and in communication with the processor. The transceiver is structured to communicate with an external receiving device. The first end of the body is structured to be coupled to the machine tool platform and the opposite second end of the body is structured to be selectively coupled to a cutting assembly having a number of sensors. The processor is structured to communicate with the number of sensors when the cutting assembly is coupled to the body. 
     The body may include a first electrical connector disposed at or near the opposite second end, the first electrical connector being electrically connected with the processor. The cutting assembly may comprise a rotary cutting tool having a first end selectively coupled to the opposite second end of the body and an opposite second end structured to engage a work piece. The first end may include a second electrical connector electrically connected with the number of sensors of the cutting assembly. The first electrical connector may be electrically connected with the second electrical connector when the cutting assembly is coupled to the body. 
     The transceiver may be a wireless transceiver. 
     The processor may comprise a microprocessor, microcontroller, or digital signal processor unit. The processor may comprise a number of data processing algorithms and models disposed therein. 
     The body may further comprise a power supply disposed therewith. The power supply may be rechargeable and may comprise a charging aperture having a removable cover, the charging aperture may be structured to connect to an external charging device. The power supply may be rechargeable by inductive charging. 
     As another aspect of the invention, a smart tool assembly is for use with a machine tool platform. The smart tool assembly comprises a smart tool holder and a cutting assembly. The smart tool holder comprises a body having a first end structured to be coupled to the machine tool platform and an opposite second end, a processor disposed with the body, and a transceiver disposed with the body and in communication with the processor. The transceiver being structured to communicate with an external receiving device. The cutting assembly having a first end and a second end, the first end being selectively coupled to the opposite second end of the body of the smart tool holder and the second end of the cutting assembly being structured to engage a workpiece. The cutting assembly having a number of sensors in communication with the processor when the cutting assembly is coupled to the smart tool holder. 
     The opposite second end of the body of the tool holder may comprise a first electrical connector and the first end of the cutting assembly may comprise a second electrical connector, the first electrical connector and the second electrical connector being positioned to cooperatively electrically and mechanically engage when the cutting assembly is coupled to the tool holder thus allowing communication between the number of sensors and the processor. 
     The cutting assembly may comprise a rotary cutting tool having a first end coupled to the opposite second end of the body of the tool holder and an opposite second end structured to engage a workpiece. The rotary cutting tool may comprise one of an endmill, shell mill, face mill, drilling tool, boring tool and other metal cutting tooling. 
     The cutting assembly may comprise an insert holder having a number of cutting inserts selectively coupled thereto. The number of sensors may be structured to sense at least one of temperature, acceleration, force, and torque. 
     The smart tool holder may further comprise a power supply disposed therewith. 
     As a further aspect of the invention, a smart tool holder is for use with a machine tool platform. The smart tool holder comprises a body having a first end and an opposite second end, a processor disposed with the body, a number of sensors disposed with the body and in communication with the processor, and a transceiver disposed with the body and in communication with the processor. The processor being structured to communicate with an external receiving device. The first end of the body being structured to be selectively coupled to the machine tool platform and the opposite second end of the body being structured to be selectively coupled to a cutting assembly. 
     The transceiver may be a wireless transceiver. 
     The processor may comprise a microprocessor, microcontroller, or digital signal processing unit. The processor may comprise a number of data processing algorithms and models disposed therein. 
     The body may further comprise a power supply disposed therewith. The power supply may be rechargeable and may comprise a charging aperture having a removable cover. The charging aperture may be structured to connect to an external charging device. The power supply may be rechargeable by inductive charging. 
     The number of sensors may be structured to sense at least one of temperature, acceleration, force, and torque. 
     As yet another aspect of the invention, a smart machining system is for machining a workpiece. The smart machining system comprises a machine tool platform, a smart tool holder, a cutting assembly, and an external receiver device. The smart tool holder comprises a body having a first end being selectively coupled to the machine tool platform and an opposite second end, a processor disposed with the body, and a transceiver disposed with the body and being in communication with the processor. The transceiver being structured to communicate with an external receiving device. The cutting assembly having a first end and a second end, the first end being selectively coupled to the opposite second end of the body of the tool holder and the second end of the cutting assembly being structured to engage a workpiece. The cutting assembly has a number of sensors in communication with the processor when the cutting assembly is coupled to the smart tool holder. 
     The machine tool platform may comprise a machine tool controller, wherein the external receiver device provides a signal to the machine tool controller. The transceiver and the external receiver device may communicate wirelessly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
       A full understanding of the invention can be gained from the following description of the preferred embodiments when read in conjunction with the accompanying drawings in which: 
         FIG. 1  is an isometric view of a smart tool holder assembly in accordance with an embodiment of the invention; 
         FIG. 2  is an exploded isometric view of the smart tool assembly of  FIG. 1 ; 
         FIG. 3  is an isometric view of another smart tool assembly in accordance with another embodiment of the invention; 
         FIG. 4  is an exploded isometric view of the smart tool assembly of  FIG. 3 ; 
         FIG. 5  is an isometric view of yet another smart tool assembly in accordance with a further embodiment of the invention; 
         FIG. 6  is a schematic diagram in block form of a smart machining system in accordance with an embodiment of the invention; 
         FIG. 7  is a schematic diagram in block form of another smart machining system in accordance with another embodiment of the invention; and 
         FIG. 8  is a schematic diagram in block form of a further smart machining system in accordance with a further embodiment of the invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As employed herein, the term “number” shall mean one or an integer greater than one (i.e., a plurality). 
     As employed herein, the term “processor” means a programmable analog and/or digital device that can store, retrieve, and process data; a computer; a workstation; a personal computer; a microprocessor; a microcontroller; a microcomputer; a central processing unit; a mainframe computer; a mini-computer; a server; a networked processor; or any suitable processing device or apparatus. Example embodiments consists of 8 bit and 32 bit microprocessors with internal DSP (digital signal processing) commands. These processing units are supplemented by high bandwidth digital to analog converters. The processing unit is also supplemented by a specialized coprocessor for controlling digital radio transmission, communication error checking, synchronization with the receiving device, and communications channel operations. 
     As employed herein, the term “sensor” means a device or apparatus that responds to a physical stimulus (e.g., without limitation, temperature, vibration, acceleration, force, torque, sound, hoop stress, infrared emission, dynamic optical stimulus (interferometer)) and outputs a resulting impulse or signal (e.g., without limitation, for monitoring, measurement and/or control). Of specific interest are semiconductor based sensors for measurement of torsion strain, bending strain, axial strain, and temperature. For example, sensors consisting of P (positive doped) or N (negative doped) type silicon materials. In an embodiment, sensors consisting of P type silicon have been made using the Czochralski process. In another embodiment, N-type silicon sensors are deployed to match sensor resistance-temperature coefficient to the linear expansion coefficient of the tool holder, minimizing temperature related drift in a torsion strain signal. Semiconductor sensor examples include, without limitation, Micron Instruments “SSGH” and Kyowa “KSN” products. 
     As employed herein, the term “smart” means operating by automation; or including or employing a number of processors, data processing algorithms, model-based decision making, and/or sensors. The term “smart” also refers to the ability of the tool holder to establish and maintain two-way communication with a machine controller or a receiving device. 
     As employed herein, the term “with” means on, partially on, partially within, or within an associated object. 
     Directional phrases used herein, such as, for example, left, right, front, back, top, bottom and derivatives thereof, relate to the orientation of the elements shown in the drawings and are not limiting upon the claims unless expressly recited therein. Identical parts are provided with the same reference number in all drawings. 
     The smart tool holder described herein overcomes shortcomings of known solutions by providing a robust, real-time sensor interface system that can provide tool tip sensor data for process condition monitoring during metal cutting by transmitting acceleration and/or force data directly from an end mill tool tip or from individual cutting inserts. Such capability is advantageous, in order to advance physical modeling and condition monitoring techniques for an end mill system. Furthermore, the smart tool holder ascends known sensor techniques by implementing onboard data analysis and model based decision making, suggesting changes in the machining conditions through a two-way communication with a CNC (Computer Numerical Control) machine tool. 
     Condition monitoring includes tool wear, runout, and stability evaluation. The example smart tool holder described herein enables accurate determination of CNC metal cutting system dynamics in order that cutting forces and, ultimately, part quality can be estimated in-process. Dynamic effects can result in tool forces and deflections an order of magnitude higher than the static deflections. Therefore, the smart tool holder can provide data for on-line characterization of machine tool dynamics to quantify their effect on part accuracy, user safety, and process evaluation. 
     The example tool holders  10  and  10 ″ depicted in  FIGS. 1-5  and described below were constructed from a High Performance Milling Chuck manufactured by Kennametal Inc. of Latrobe, Pa. It is to be appreciated, however, that the invention is not intended to be limited in any manner to such tool holders. Other suitable tool holders (e.g., without limitation, Shrink Fit Tool Holders, Weldon Shank Set Screw Tool Holders, Collet Tool Holders, ISO Capto Tool Holders, Vibration Damped Tool Holders, Face Milling Adapters, Thread Milling Tool Holders, Solid Carbide/HSS Milling Tools, Precision Hole Tool Holders, Tooling Length Extension Units, Turning and Lathe tools) may be modified and employed without departing from the scope of the present invention. 
     Referring to  FIG. 1 , an example smart tool holder assembly  6  for use with a machine tool platform  8  (shown in phantom line drawing) in performing machining operations on a workpiece (not shown) in accordance with one non-limiting embodiment of the invention is shown. The smart tool holder assembly  6  includes a smart tool holder  10  and a removable cutting assembly  18 . 
     As shown in  FIG. 2 , the smart tool holder  10  includes a body  12  having a first end  14  and an opposite second end  16 . The first end  14  of the body  12  is structured to be selectively coupled to the machine tool platform  8 . Such coupling of the first end  14  of the smart tool holder  10  to the machine tool platform  8  may readily be accomplished by for example, without limitation, standard spindle tapers such as the CV50 geometry shown, CV40, HSK, BT40, BT30, ISO Capto, among other industry standard spindle geometries available on modern machine tools. 
     The opposite second end  16  of body  12  is structured to selectively couple one of a variety of potential cutting assemblies  18 . Such coupling of the second end  16  of the smart tool holder  10  to the cutting assembly  18  may readily be accomplished by for example, without limitation, shrink fit, precision chuck, collet, weldon shank, among various available proprietary tool holding interface geometries. 
     Body  12  of smart tool holder  10  can include a number of electrical components as shown, for example, in  FIGS. 6-8 . More particularly, body  12  includes a processor  20 , a transceiver  22 , and power supply  23  disposed on, partially on, within, or partially within body  12 . In some embodiments, body  12  may also include a number of sensors (not shown in  FIG. 1 ) as will be discussed further below. Processor  20  includes one or more of an internal and external memory (not shown). The processor  20  may be, for example and without limitation, a microprocessor (μP) that interfaces with the memory or a standalone DSP (digital signal processing) unit. The memory may be any one or more of a variety of types of internal and/or external storage media such as, without limitation, RAM, ROM, EPROM(s), EEPROM(s), FLASH, and the like that provide a storage register, i.e., a machine readable medium, for data storage in a similar fashion to an internal memory storage of a computer, and can be volatile memory or nonvolatile memory. The memory has stored therein a number of routines  24  that are executable by the processor  20 . One or more of the routines  24  implement a software-based analysis system that is operable to receive input from one or more sensors  26  (discussed below) and provide output to the transceiver  22  for further transmission outside of the body  12  of the smart tool holder  10 . It is to be appreciated that the routines  24  shown in  FIGS. 6-8  are provided for example purposes only and are not meant to be limiting upon the scope of the present invention. Routines  24  may, for example, and without limitation, perform data processing/analysis techniques such as: estimating and predicting chatter frequencies, suggesting stable spindle speeds, wear monitoring, and suggesting feed rate overrides. Such techniques, for example, may commonly employ the methods of: Kalman filters, formant frequency tracking/LPC (Linear Predictive Coding), autoregressive models, mechanistic cutting force models, FIR (Finite Impulse Response) and IIR (Infinite Impulse Response) digital filters, Fourier spectral analysis, and statistical data analysis. 
     Transceiver  22  preferably comprises a digital wireless transceiver, for example, without limitation, a FHSS (Frequency Hopping Spread Spectrum) transceiver, a frequency agility transceiver, or a digital infrared transceiver employing for example, without limitation, the methods of auto retransmission, error correction, and ISM (Industrial, Scientific, and Medical) band frequencies. Transceiver  22  is structured to send and receive signals from a receiver/transceiver device  28  ( FIGS. 6-8 ) positioned external to the smart tool holder  10 . The receiver/transceiver device  28  may comprise a transceiver module interfaced with analog or digital outputs and integrated with a data analysis processing unit consisting of a PC, microprocessor, or DSP (digital signal processing) hardware. 
     Generally the system transceiver  22  will either send all of the data in a streaming fashion (high bandwidth), or, it will send analysis results in a condensed form (low bandwidth). A user of the system would have the option of requesting either. High bandwidth data is sent at a rate on the order of about 10-20 kHz at 16 bit resolution. Low bandwidth analysis results are sent at a rate on the order of about 1 kHz. A third option allows the transceiver to be turned off to set the tool in data logging mode, wherein the tool collects and stores information for later retrieval. In such case, such storage and later retrieval of data may also be accomplished through use of a removable memory device (not shown) included additional to, or in place of, transceiver device  22 . Communication with the smart tool holder  10  is preferably two-way since process parameters (e.g., without limitation, cut feed rates, spindle speed, positions, tool engagements) may be sent to the smart tool holder  10 . 
     Power supply  23  provides electrical power to processor  20  and as needed to other electrical components of the smart tool holder  10 . Power supply  23  may include replaceable batteries or replaceable rechargeable batteries that may be recharged using an external charging station (not shown). Additionally, power supply  23  may include internal rechargeable batteries or an internal super capacitor. Examples of foreseeable recharging sources for such internal power supplies include, without limitation, inductive charging, near field magnetic resonant coupling (such as WiTricity), a physical charging jack, photovoltaics (solar panels), vibration energy harvesting (such as piezoelectric parasitic generators), inertial energy harvesting (through a dynamo or other generator), generators designed to harvest power from the flow of through-coolant, and generators operating from dynamic air movement around the rotating tool holder. Power transmission through directed radio frequency emission or lasers may also be employed. In the embodiments shown in  FIGS. 1-4 , the power supply  23  may be recharged through the use of an external charging jack (not shown) that would be coupled to a charging aperture  27  provided on the body  12  of the smart tool holder  10 . During machining operations, the charging aperture  27  may be covered with a protective cover or cap  29  that may readily be removed when charging operations are to be performed, such as when the smart tool holder assembly  6  is not engaged in machining operations. 
     Body  12  further includes an electrical connector  30  electrically connected to processor  20  and disposed generally at or near the opposite second end  16 . Another embodiment of the smart tool holder  10 ″ (shown in  FIG. 5 ) contains sensors disposed on the body  12  and does not contain an electrical interface to the tool. Such embodiment as shown in  FIG. 5  does not interfere with through coolant use and can sense data from any standard (non-sensor integrated) cutting tools. In the embodiments depicted in  FIGS. 1-4 , processor  20  and transceiver  22  are housed within a sealed housing  32  on body  12 . Processor  20  and transceiver  22  are electrically connected such that processor  20  may send and receive information from transceiver  22 . 
     Body  12  may further comprise a number of lights or other indicia (not numbered) for providing one or more visible indications of the status of the smart tool holder  10 . Such indications may be employed to inform an operator of such condition as, for example, without limitation, the presence of sensor outputs, tool condition, power status, displaying the arc length of tool engagement, and displaying ‘stationary’ images or text on the tool holder by illuminating at the frequency of tool holder rotation. 
     The smart tool holder assembly  6  shown in  FIGS. 1 and 2  depicts an embodiment in which the cutting assembly  18  comprises an insert holder  34  of generally longitudinal shape having a first end  36  and a generally opposite second end  38 , the first end  36  being structured to be selectively coupled to the opposite second end  16  of the body  12  of smart tool holder  10  (as shown in  FIG. 1 ). Insert holder  34  includes a number of cutting inserts  40  selectively coupled generally at or near the opposite second end  38 , a number of sensors  26  disposed at selected locations on, partially within, or within the insert holder  34 , and an electrical connector  42  preferably disposed at or near the first end  36 . The electrical connector  42  is electrically connected to each of the number of sensors  26  and is structured to cooperatively mechanically and electrically engage the electrical connector  30  of the smart tool holder  10  when the cutting assembly  18  is coupled to the smart tool holder  10  (as shown in  FIG. 1 ). Each of the cutting inserts  40  is structured to engage a workpiece  50  ( FIGS. 6-8 ) during machining operations. 
     As shown in  FIG. 2 , the number of sensors  26  may include a tool tip accelerometer  44  embedded within the insert holder  34  and a force or torque sensor  46  disposed at or near a surface of the insert holder  34 . It is to be readily appreciated that such sensors  26  and locations are given for example purposes only and are not intended to limit the scope of the invention. In the case of an accelerometer, it is important to locate the sensor as close to the tool tip as possible in order to observe the movement dynamics of the tool tip without requiring the methods of RCSA (receptance coupling substructure analysis). 
     The smart tool holder assembly  6 ′ shown in  FIGS. 3 and 4  depicts an embodiment in which the cutting assembly  18 ′ comprises a rotary end mill cutting tool  52  (shown in  FIG. 4 ) of generally longitudinal shape having a first end  54  and a generally opposite second end  56 , the first end  54  being structured to be selectively coupled to the opposite second end  16  of the body  12  of smart tool holder  10  (as shown in  FIG. 3 ) and the second end being structured to engage a workpiece  50  ( FIGS. 6-8 ) during machining operations. Cutting tool  52  further includes a number of sensors  26  disposed at selected locations on or within the cutting tool  52 , and an electrical connector  42  preferably disposed at or near the first end  54 . The electrical connector  42  is electrically connected to each of the number of sensors  26  and is structured to cooperatively mechanically and electrically engage the electrical connector  30  of the smart tool holder  10  when the cutting assembly  18 ′ is coupled to the smart tool holder  10  (as shown in  FIG. 3 ). 
     As shown in  FIG. 4 , the number of sensors  26  may include a tool tip accelerometer  58  embedded within the cutting tool  52  and a force or torque sensor  60  disposed at or near a surface of the cutting tool  52 . It is to be readily appreciated that such sensors  26  and locations are given for example purposes only and are not intended to limit the scope of the invention. 
     The smart tool holder assembly  6 ″ shown in  FIG. 5  depicts a further embodiment in which the smart tool holder  10 ″ itself includes a number of sensors  26  disposed therewith. Sensors  26  may include, for example without limitation, sensors for detecting torque, bending force, axial force, hoop stress, and acceleration. In this embodiment, cutting assembly  18 ″ is shown as a known rotary end mill cutting tool. However it is to be appreciated that other cutting tools may readily be employed as cutting assembly  18 ″ (e.g., without limitation, endmills, shell mills, face mills, drilling tools, boring tools, and other metal cutting tooling). 
     Furthermore, it is to be readily appreciated that such sensors  26  and locations are given for example purposes only and are not intended to limit the scope of the invention. 
     Having thus described some example tool holder assemblies  6 ,  6 ′, and  6 ″, an example smart machining system employing the tool holder assembly  6  will now be described.  FIG. 6  shows a smart machining system employing a smart tool assembly  6  utilizing insert holder  34  such as shown in  FIGS. 1 and 2  having a number of cutting inserts  40  that machine the workpiece  50 . During machining, the sensors  26  provide data to the processor  20  which then analyzes the data using one or more of the routines  24 . The data resulting from such analysis by the processor  20  is then transmitted by the transceiver  22  to receiver/transmitter device  28  external to the smart tool holder  10  for observation or potential further analysis. In addition to transmitting data from the smart tool holder  10 , transceiver  22  may further be used to receive data transmitted to the smart tool holder  10  by the external receiver/transmitter device  28  or by another communication device or apparatus (not shown). Such data transmitted to the smart tool holder  10  may include data sent prior to, during, or after machining operations (e.g., without limitation, cut feed rates, spindle speed, positions, tool engagements). 
     It is to be readily appreciated that  FIG. 7  shows a smart machining system employing a smart tool assembly  6 ′, such as shown in  FIGS. 3 and 4 , and which operates substantially the same as the system previously described in regard to  FIG. 6 . Likewise,  FIG. 8  shows a smart machining system employing a smart tool assembly  6 ″, such as shown in  FIG. 5 , and which also operates substantially the same as the system previously described in regard to  FIG. 6 . Accordingly, a detailed discussion of  FIGS. 7 and 8  is not provided herein. 
     While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the claims appended and any and all equivalents thereof.