High-speed precision interrupted ultrasonic vibration cutting method

Abstract

A high-speed precision interrupted ultrasonic vibration cutting method includes steps of: (1) installing an ultrasonic vibration apparatus on a machine tool, and stimulating a cutting tool to generate a transverse vibration, so as to realize varieties of machining processes; (2) realizing an interrupted cutting process by setting cutting parameters and vibration parameters to satisfy an interrupted cutting conditions; and (3) turning on the ultrasonic vibration apparatus and the machine tool, and starting a high-speed precision interrupted ultrasonic vibration cutting process. High-speed precision interrupted ultrasonic vibration cutting is able to be realized through the above steps during machining of difficult-to-machine materials in aviation and aerospace fields. A cutting speed is enhanced significantly, and exceeds a critical cutting speed of a conventional ultrasonic vibration cutting method and an elliptical ultrasonic vibration cutting method and even a high speed range of a traditional cutting method.

Claims

1. A high-speed precision interrupted ultrasonic vibration cutting method, comprising steps of: (1) installing an ultrasonic vibration apparatus on a machine tool, and stimulating a cutting tool to generate a transverse vibration or a vibration with a transverse component, wherein: through combining different vibration types and machining process types, varieties of machining processes are able to be realized; (2) realizing an interrupt cutting processing by setting cutting parameters and vibration parameters to satisfy interrupted cutting conditions and periodically separating the cutting tool from a finished surface profile of a workpiece; and (3) turning on the ultrasonic vibration apparatus and the machine tool, and starting a high-speed precision interrupted ultrasonic vibration cutting process; wherein: high-speed interrupted ultrasonic vibration cutting is able to be realized through the above steps during machining of difficult-to-machine materials in aviation and aerospace fields; a cutting speed is enhanced significantly, which exceeds a critical cutting speed of a conventional ultrasonic vibration cutting method and an elliptical ultrasonic vibration cutting method and even a high speed range of a traditional cutting method; besides, beneficial effects of cutting force and cutting temperature reductions, tool life prolonging, machining cost save, and surface quality and machining accuracy improvements are all obtained at the same time; the interrupted cutting condition in the step (2) refers to a formula as listed of: $\{\begin{array}{c}2A\\ 2\arcsin \left(/2A\right)2-2\arcsin \left(/2A\right)\end{array},$ wherein: is a center line offset value of two adjacent feed tool paths, which is related to the cutting parameters of feedrate and depth of cut, and determined according to a specific machining process and vibration types; is a phase difference of the two adjacent feed tool paths, which is related to the vibration parameters of tool vibration frequency and workpiece or tool rotatory speed, and determined according to the specific machining process and the vibration types; and A is a tool vibration amplitude.

2. The high-speed precision interrupted ultrasonic vibration cutting method, as recited in claim 1, wherein the ultrasonic vibration apparatus in the step (1) is an apparatus which is able to stimulate the cutting tool to generate a transverse steady ultrasonic vibration or a steady ultrasonic vibration with a transverse component by amplifying a vibration generated by a transducer stimulated by an ultrasonic generator through an horn.

3. The high-speed precision interrupted ultrasonic vibration cutting method, as recited in claim 1, wherein the machine tool in the step (1) is one of lathes, milling machines, drilling machines, grinding machines and machine centers; and the cutting tool in the step (1) is one of turning tools, milling tools, grinding tools, drilling tools, reamers and countersinks.

4. The high-speed precision interrupted ultrasonic vibration cutting method, as recited in claim 1, wherein the transverse vibration or the vibration with the transverse component in the step (1) is an ultrasonic vibration on any point of the cutting tool, and a vibration direction thereof is vertical to a cutting speed direction.

5. The high-speed precision interrupted ultrasonic vibration cutting method, as recited in claim 1, wherein the cutting parameters in the step (2) comprise the depth of cut, the feedrate and the cutting speed; and the vibration parameters in the step (2) comprise a vibration amplitude and a vibration frequency.

6. The high-speed precision interrupted ultrasonic vibration cutting method, as recited in claim 1, wherein the step of setting cutting parameters and vibration parameters in the step (2) has principles that: a relative small and a 180 degree phase difference are optimal for an interrupted separation of best effection; is a parameter to scale a transverse relation of two adjacent feed tool paths while is a parameter to scale a longitudinal relation of the two adjacent feed tool paths, and, and affect an interrupted separation effect simultaneously; when a value of exceeds double of a value of a vibration amplitude, due to an oversized transverse distance between the two adjacent feed tool paths, whatever a value of , no interrupted separation effect occurs during the whole cutting process; conversely, when the value of is given in an appropriate neighborhood of zero, because no cross point exists at the two adjacent feed tool paths, whatever the value of , no interrupted separation effect occurs during the whole cutting process.

7. The high-speed precision interrupted ultrasonic vibration cutting method, as recited in claim 1, wherein the finished surface profile in the step (2) is a combination curve of six arcs, respectively an arc M.sub.1M.sub.2, an arc M.sub.2M.sub.3, an arc M.sub.3M.sub.4, an arc M.sub.4M.sub.5, an arc M.sub.5M.sub.6 and an arc M.sub.6M.sub.7, which are respectively an (N-1).sup.th tool motion path, an (N-2).sup.th tool motion path, an (N-3).sup.th tool motion path, an (N-4).sup.th tool motion path, an (N-5).sup.th tool motion path, and an (N-6).sup.th tool motion path; the number of the tool motion paths influencing the finished surface profile is determined by the tool vibration amplitude A and the center line offset value of two adjacent feed tool paths; when a value of 2A/ is an integer, the number equals to 2A/, while when the value of 2A/ is a decimal, the number equals to an integer part of 2A/ plus one; as a tool nose round radius is far greater than a value of , a regular surface profile is obtained after repeatedly cutting by a tool tip and thus a better surface quality is obtained.

8. The high-speed precision interrupted ultrasonic vibration cutting method, as recited in claim 1, wherein the interrupted cutting process in the step (2) is an interrupted cutting process of the cutting tool with the transverse vibration or the vibration with the transverse component along an N.sup.th tool motion path which has an interrupted separation effect on the finished surface profile of the workpiece; a point a is where the cutting tool is just engaged into the finished surface profile of the workpiece during a vibration cutting cycle; a point b is located at a lowest point of the N.sup.th tool motion path; a stage from the point a to the point b is a cut-in stage, during which the tool and the workpiece are in contact sufficiently, a depth of cut increases, a cutting force is enhanced and a cutting heat is accumulated; a point c is where the cutting tool is just disengaged form the finished surface profile of the workpiece during a vibration cycle; a stage from the point b to the point c is a cut-out stage, during which a contact area of the tool and the workpiece decreases, a cutting zone gradually separates from the workpiece, the cutting force decreases and a cutting heat accumulation slows down; at the point c, the cutting tool is completely separated from the finished surface profile of the workpiece, the cutting zone vanishes, the cutting force decreases to zero, and the cutting heat starts to transmit to surrounding mediums; a point d is where the cutting tool is just engaged into the finished surface profile in a next vibration cycle; a stage from the point c to the point d is a noncutting stage, during which the cutting tool is completely separated from the workpiece, the cutting force stays at zero, if a cooling medium exists, the cutting zone of the cutting tool fully contacts the cooling medium, and a temperature of the cutting tool decreases significantly; and, a process of (point a)-to-(point b)-to-(point c)-to-(point d) is a cutting process during one vibration cycle when the transverse vibration or the vibration with the transverse component is applied, which occurs periodically as the vibration is repeated periodically during the whole machining process.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic diagram of a speed range of high-speed machining according to prior art.

(2) FIG. 2A is a schematic diagram of a conventional ultrasonic vibration cutting method according to the prior art.

(3) FIG. 2B is a schematic diagram of an elliptical ultrasonic vibration cutting method according to the prior art.

(4) FIG. 3 is a schematic diagram of a high-speed precision interrupted ultrasonic vibration cutting method according to preferred embodiments of the present invention.

(5) FIG. 3A is a principal diagram of the high-speed precision interrupted ultrasonic vibration cutting method according to the preferred embodiments of the present invention.

(6) FIG. 3B shows a cutting surface profile of the high-speed precision interrupted ultrasonic vibration cutting method according to the preferred embodiments of the present invention.

(7) FIG. 4 is a comparison diagram of a cutting force of the high-speed precision interrupted ultrasonic vibration cutting method and a traditional cutting method according to the preferred embodiments of the present invention.

(8) FIG. 5 is a comparison diagram of a tool wear of the high-speed precision interrupted ultrasonic vibration cutting method and the traditional cutting method according to the preferred embodiments of the present invention.

(9) FIG. 6 is a comparison diagram of a surface roughness Ra of the high-speed precision interrupted ultrasonic vibration cutting method and the traditional cutting method according to the preferred embodiments of the present invention.

(10) FIG. 7 is a schematic diagram of high-speed interrupted ultrasonic vibration turning according to a first preferred embodiment of the present invention.

(11) FIG. 8A is a schematic diagram of high-speed interrupted two-dimensional (2D) elliptical ultrasonic vibration milling (grinding) according to a second preferred embodiment of the present invention.

(12) FIG. 8B is a schematic diagram of high-speed interrupted axial ultrasonic vibration plunge milling according to the second preferred embodiment of the present invention.

(13) FIG. 8C is a schematic diagram of high-speed interrupted axial ultrasonic vibration grinding according to the second preferred embodiment of the present invention.

(14) FIG. 9 is a schematic diagram of high-speed interrupted ultrasonic vibration drilling according to a third preferred embodiment of the present invention.

(15) FIG. 10 is a schematic diagram of high-speed interrupted ultrasonic vibration reaming according to the third preferred embodiment of the present invention.

(16) FIG. 11 is a schematic diagram of high-speed interrupted ultrasonic vibration counter boring according to the third preferred embodiment of the present invention.

(17) FIG. 12 is a flow chart of the high-speed precision interrupted ultrasonic vibration cutting method according to the preferred embodiments of the present invention.

(18) In figures:

(19) TABLE-US-00001 1: workpiece 2: cutting tool 21: turning tool 22: milling tool 23: grinding tool 24: drilling tool 25: reamer 26: countersink

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(20) According to preferred embodiments of the present invention, a high-speed precision interrupted ultrasonic vibration cutting method is provided, wherein a principal diagram thereof is showed in FIG. 3 and FIG. 3A, and a cutting surface profile thereof is showed in FIG. 3B. Different from a conventional ultrasonic vibration cutting method showed in FIG. 2A and an elliptical ultrasonic vibration cutting method showed in FIG. 2B, the present invention has several advantages which are respectively showed in FIG. 4, FIG. 5, and FIG. 6, and enables a cutting speed to exceed a high speed range of a traditional cutting method showed in FIG. 1. A flow chart of the cutting method of the present invention is showed in FIG. 12.

(21) First preferred embodiment: High-speed interrupted ultrasonic vibration turning

(22) Turning is a cutting process, which is for narrowing an outer diameter or an end surface of a circular profile. An application range of turning is generally from semi-roughing roughing machining to finishing machining. A cutting tool of turning is a turning tool 21, referring to FIG. 7.

(23) A workpiece 1 is firstly fixed in a lathe spindle (not shown in figures). Then, turning parameters, such as a spindle rotatory speed (or a workpiece linear speed), a depth of cut and a feedrate, are set. Next, vibration parameters of the turning tool 21, such as a vibration frequency, a vibration direction and a vibration amplitude, are set. The mentioned turning parameters and vibration parameters are required to match each other to satisfy an interrupted separation condition. When a vibration is an axial ultrasonic vibration {circle around (1)}, the vibration direction is vertical to a cutting speed direction and in parallel with a feed direction of the turning tool 21. When the vibration is a radical ultrasonic vibration {circle around (2)}, the vibration direction is vertical to the cutting speed direction and points to a center line of the workpiece 1. When the vibration is an elliptical ultrasonic vibration {circle around (3)}, the vibration direction is a combination of axial and radical directions, and a vibration plane of the vibration is vertical to the cutting speed direction. Finally, an ultrasonic vibration apparatus and the lathe spindle are turned on, and high-speed interrupted ultrasonic vibration turning is carried out.

(24) In an experiment of turning titanium alloys with a linear cutting speed of 200 m/min, a depth of cut of 0.05 mm, a feedrate of 0.005 mm/r and a regular cutting fluid, a maximum reduction of a cutting force is able to reach 50%, a cutting temperature is reduced, a tool life increases by three times, and, a cutting efficiency and a finished surface quality are improved significantly.

(25) Second preferred embodiment: High-speed interrupted ultrasonic vibration milling/grinding

(26) Milling is a process, which is for shape machining by rotatory multi-blade tools. An application range of milling is generally from roughing machining to finishing machining. A cutting tool of milling is a milling tool 22.

(27) Grinding is a process, which is for removing of a workpiece by sintered hard abrasive tools or free hard abrasive tools. An application range of grinding is generally from finishing machining to superfinishing machining. A cutting tool of grinding is a grinding tool 23.

(28) A workpiece 1 is firstly fixed in a milling/grinding machine (not shown in figures). Then, milling/grinding parameters, such as a spindle rotatory speed (or a workpiece linear speed), a depth of cut and a feedrate, are set. Next, vibration parameters of the milling tool 22 or the grinding tool 23, such as a vibration frequency, a vibration direction and a vibration amplitude, are set. The mentioned milling/grinding parameters and vibration parameters are required to match each other to satisfy an interrupted separation condition in a cutting process of each milling tooth or each grinding grain. Referring to FIG. 8A, when machining a side surface of the workpiece by a side blade of the milling tool 22 or the grinding tool 23, a vibration is a two-dimensional (2D) elliptical vibration, which has a direction component vertical to a cutting speed direction of each milling tooth or grinding grain. Referring to FIG. 8B, when machining a round corner by the milling tool 22 which is embodied to be a plunge milling tool herein, the vibration is an axial ultrasonic vibration, and the vibration direction is vertical to a cutting speed direction of each cutting blade of the plunge milling tool. Referring to FIG. 8C, when machining an end surface of the workpiece, the vibration is the axial ultrasonic vibration, and the vibration direction is vertical to the cutting speed direction of each grinding grain. Finally, an ultrasonic vibration apparatus and the milling/grinding machine are turned on, and high-speed interrupted ultrasonic vibration milling/grinding is carried out.

(29) In an experiment of milling titanium alloys with a linear cutting speed of 250 m/min, a radical depth of cut of 0.1 mm, an axial depth of cut of 2 mm, a feedrate of 0.005 mm/r and a regular cutting fluid, a maximum reduction of a cutting force is able to reach 60%, a cutting temperature is reduced, a tool life increases by 3.5 times, and, a cutting efficiency and a finished surface quality are improved significantly.

(30) (3) Third preferred embodiment: High-speed interrupted ultrasonic vibration drilling/reaming/counter boring

(31) Drilling is a process, which is for hole machining. An application range of drilling is generally from roughing machining to finishing machining. A cutting tool of drilling is a drilling tool 24, referring to FIG. 9.

(32) Reaming is a process, which is for removing a thin lamella metal from a finished hole wall in order to obtain an accurate hole diameter and geometric shape with a relatively lower surface roughness. An application range of reaming is generally finishing machining. A cutting tool of reaming is a reamer 25, referring to FIG. 10.

(33) Counter boring is a process, which is for machining a cylindrical countersunk hole, a conical countersunk hole and a raised head face on finished holes. An application range of counter boring is generally finishing machining. A cutting tool of counter boring is a countersink 26, referring to FIG. 11.

(34) A workpiece 1 is firstly fixed in a drilling machine (not shown in figures). Then, drilling/reaming/counter boring parameters, such as a spindle rotatory speed (or a workpiece linear speed) and a feedrate, are set. Next, vibration parameters of the drilling tool 24, the reamer 25, or the countersink 26, such as a vibration frequency, a vibration direction and a vibration amplitude, are set. The mentioned drilling/reaming/counter boring parameters and vibration parameters are required to match each other to satisfy an interrupted separation condition. When a vibration is an axial ultrasonic vibration {circle around (1)}, the vibration direction is vertical to a cutting speed direction and in parallel with a feed direction of the drilling tool 24, the reamer 25, or the countersink 26. When the vibration is a 2D elliptical ultrasonic vibration CD, the vibration direction is a combination of axial and radical directions, and the vibration has a direction component vertical to the cutting speed direction of the drilling tool 24, the reamer 25, or the countersink 26. Finally, an ultrasonic vibration apparatus and the drilling machine are turned on, and high-speed interrupted ultrasonic vibration drilling/reaming/counter boring is carried out.

(35) The present invention provides the high-speed precision interrupted ultrasonic vibration cutting method, wherein a transverse vibration or a vibration with a transverse component of the tool is applied and varieties of machining process are combined, such as turning, milling, drilling, and grinding. The present invention realizes high-speed precision interrupted ultrasonic vibration cutting for the workpiece. The cutting speed is significantly enhanced by an application of the transverse vibration or the vibration with the transverse component. The cutting speed is enhanced significantly, and exceeds a critical cutting speed of the conventional ultrasonic vibration cutting method and the elliptical ultrasonic vibration cutting method and even the high speed range of the traditional cutting method. Besides, beneficial effects of cutting force and cutting temperature reductions, tool life prolonging, machining cost save, and surface quality and machining accuracy improvements are all obtained at the same time. In order to satisfy the interrupted separation condition of the present invention, cutting parameters and the vibration parameters are required to satisfy a following formula of:

(36) $\{\begin{array}{c}2A\\ 2\arcsin \left(/2A\right)2-2\arcsin \left(/2A\right)\end{array}.$

(37) A periodical separation effect of the cutting tool 2 and the workpiece 1 enables a maximum reduction of a thrust cutting force of 50%, a more obvious temperature reduction because of fully cooling and lubricating the cutting tool in a noncutting stage when a cutting fluid is applied, tool wear deferring, tool life prolonging (by about three times), and significant improvements of the cutting efficiency and the finished surface quality.