METHOD AND APPARATUS FOR VIBRATING CUTTING TOOL
BACKGROUND OF THE INVENTION
The present invention relates to machine industry, in particularly to metal mε?hιnιng by cutting tools with one or more cutting edges
The proposed vibration cutting method is intended for chips breakage when machining hardly machined steels, alloys, tenacious non-ferrous metals and composite materials by proposed vibrating cutting tool The vibrating cutting tool performs feed motion and oscillation motion in feed direction due to components of cutting resistance forces thus increasing cutting speed without additional power supply and special devices At the same time a cutting plate durability and machining accuracy are increased
Known are vibration cutting methods containing mechanical, electromechanical, hydraulic, magnetostπctive and other drivers for producing oscillating movement of various cutting tools But when machining hardly machined steels, alloys, tenacious non-ferrous metals and composite materials these drivers contain various oscillation generators with additional devices and equipment
Known is US Patent No 5,113,728 "Method and apparatus for forming intermittent chips when machining a rotating workpiece", issued on May 19, 1992 (Patent Application No 596041 filed on October 11 , 1990) The main disadvantage of this Patent as well as other technical solutions aimed to form intermittent chips when machining workpieces is that they need cutting tool connection to a additional device which contains a separate driver and oscillation generator
Known are cutting tools which contain removable cutting plates with hitches, horns and grooves arranged along cutting plate perimeter
But when machining hardly machined steels, alloys, tenacious non- ferrous metals and composite materials all these static solutions are non
effective and upon increasing cutting speed the machining becomes impossible due to fast wear and breaks of cutting plate
Known is the Patent of Japan No 08300207 for "Vibrating blade" issued on Nov 19, 1996 (Patient Application No 07108670 filed on May 2, 1995) The main disadvantage of this Patent as well as other technical solutions for machining hardly machined steels and alloys is that they need cutting tool connection with additional device which contains separate driver and which causes an increased power consumption To disadvantages of the known designs has to be referred also a rigid drive connection between cutting tool and oscillation generator of additional devices This is followed by cutting speed, durability and machining accuracy reduction
The proposed invention is aimed to create vibrating cutting method that enables to form intermittent chips by proposed vibrating cutting tool which performs feed motion and oscillating motion in feed direction due to cutting resistance forces and elastic elements of cutting tool oscillation loop and to increase cutting speed without additional power supply for cutting tool oscillating movement, to increase cutting plate durability, to provide machining accuracy and surface asperity value
SUMMARY OF THE INVENTION
For this purpose to be attained, it is proposed a vibrating cutting method when machining hardly machined steels, alloys, tenacious non-ferrous metals and composite materials applied to lathe with cutting tool that has forward path feed movement The method contains the following stages - workpiece rotation around rotation axis,
- cutting tool adjustment into strictly determined positions on its forward path leeα movement according to rotating workpiece angle
positions during cutting process so that
- under impact of cutting resistance forces the cutting tool nose position has sinusoidal shape with different oscillation amplitude (A) and micro asperity height (h), - oscillation amplitude of cutting tool and micro asperity height may be regulated,
- at phase angle τ values equal to zero, (π) and (2π) the cutting tool edges position under angle oscillations coincides with that of even cutting, the cutting layer section and micro asperity height for indicated phase angle values are equal while the cutting tool nose paths on two consecutive revolutions provide intermittent chips,
- at phase angle τ equal to π divided two times (π/2) the cutting tool nose paths are located on the maximum distance from each other, micro asperity height (hmax) is maximal, cutting tool nose oscillation amplitude fulfills condition A=0 5S, where S is feed value, thus intermittent chips are provided,
- at phase angle τ equal to three π divided two times (3π/2) the cutting tool nose paths touch each other, the cutting layer section is minimal, the cutting layer depth changes to zero and chips fracture occurs,
- regulation of said cutting tool nose oscillation amplitude (A) by elastic elements of different rigidity that are included into vibrating cutting tool oscillation loop
The proposed cutting tool contains a fixed working part, a cover connected to the said working part, an oscillation loop which includes movable working cutting tool part, one or several replaceable cutting plates, secured on the said front working part, a set of elastic elements which connect said movable working cutting tool part with the basis of the said fixed cutting tool working part, said oscillation loop oscillation shaft secured between the basis of the said fixed cutting tool part and said cover, while said movable working part with secured on it said replaceable cutting plate is mounted on said shaft with possibility of rotation due to cutting forces components
BRIEF DESCRIPTION OF THE DRAWINGS
Peculiarities and advantages of the proposed invention will become more evident on consideration of the preferable invention realization sample which is given exclusively for example with references on the attached drawings, wherein:
Fig.1 schematically shows vibration cutting tool with angle oscillations when performing turning machining operation.
Fig.2 schematically shows a machining surface and cutting layer sections when performing turning machining operation with cutting tool angle oscillations.
Fig.3 schematically shows cutting tool nose paths in the XOY plate;
Fig.4 schematically shows vibrating cutting tool when performing turning machining operation, top view;
Fig.5 -section B-B, see Fig.4;
Fig.6 schematically shows vibrating cutting tool when performing cutting operation - top view;
Fig.7 schematically shows vibrating cutting tool when performing cutting operation - side view.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The proposed vibration cutting method for machining hardly machined steels, alloys, tenacious non-ferrous metals and composite materials (Fig.1 to Fig.3) is schematically shown at example of turning machining operation performed on lathe and comprises the following stages:
- workpiece rotation around rotation axis; - cutting tool adjustment into strictly determined positions on its forward pathway movement according to rotating workpiece angle positions when performing cutting process;
- regulation of said cutting tool nose oscillation amplitude (A) is performed by elastic elements of different rigidity that are included into vibrating cutting tool oscillation loop. Thus when adjusting said cutting tool into strictly determined positions under impact of cutting resistant forces, the cutting tool nose movement has sinusoidal shape with different oscillation amplitude A and micro asperity height h, while said amplitude A and micro asperity height h have possibility to be regulated; - at phase angle τ values equal to zero, π and 2π, cutting tool edges positions under angle oscillations coincide with those of even cutting, the cutting layer section and micro asperity height for indicated phase angle values are equal, while the cutting tool nose paths of two consecutive revolutions provide intermittent chips; - at phase angle τ equal to π divided two times (π/2) the cutting tool nose paths are located on the maximum distance from each other, micro asperity height (hmax) is maximal, cutting tool nose oscillation amplitude fulfills condition A=0.5S, where S is feed value, thus intermittent chips are provided;
- at phase angle τ equal to three π divided two times (3π/2) the cutting tool nose paths touch each other, the cutting layer section is minimal, the cutting layer depth changes to zero and chips fracture occurs.
The machined workpiece 1 (Fig 1) is secured into lathe chuck 2 The proposed cutting tool 3 is secured into lathe tool holder 4
Upon this the vibrating cutting tool 3 (Fig 2 to Fig 7) contains a fixed working part 5, a cover 6 connected to the said working part, an oscillation loop 7, comprising front movable working cutting tool part 8, one or several replaceable cutting plates 9 which are secured on the said movable working part 8, a set of elastic elements 10, 10* and 10** which connects said movable working cutting tool part with the basis of the said fixed cutting tool working part, said oscillation loop shaft 11 secured between said fixed working part basis and said cover, bearing assemblies 12 and 12* secured between said shaft and said fixed cutting tool part, upon this said movable cutting tool working part with secured on it said replaceable cutting plate is secured on the said shaft with possibility to be rotated due to cutting forces components appeared when performing machining process The vibration cutting method is performed as follows The lathe chuck 2 power supply is switched on and machining workpiecel which is secured in the lathe chuck 2 performs rotational movement with angle speed ω The said vibrating cutting tool 3 which is secured into lathe cutting tool holder 4 is driven up to the moment when cutting tool 3 nose touches with rotating machined workpiece 1 surface Then the said cutting tool 3 is removed from the machined workpiece 1 and a cutting depth t is adjusted Then working •feβ S is adjusted for the said cutting tool The cutting depth is formed as a result of two movements machined workpiece 1 rotation movement with angle speed ω and feed movement S The machined workpiece 1 angle speed ω(τ) and cutting tool 3 linear speed which is equal to feed value are variable values The law of the cutting tool 3 oscillatory movement is harmonic
Jι=A-|Sin(τ-τo) J2=A2 sιnτ
Where J - cutting tool 3 turn angle referred to perpendicular raised from oscillation shaft K to machined workpiece 1 surface, for the first (1) and second (2) machined workpiece 1 revolutions accordingly; A - angle oscillation amplitude τ - phase shift angle τo - phase shift angle taking into account non integer number of oscillations per one revolution.
When cutting with angle oscillations (Fig.l) the cutting tool 3 performs, referred to machined workpiece 1 , angle oscillations in XOY plate except movement in feed S direction. Fig.2 shows machined surface and cut layer sections after quarter of a period for phase angle shift τ0=π. The cutting tool 3 cutting edges positions (Fig.2) are marked: at the first revolution - main cutting edge Gi and additional Vi, at second revolution G2 and V2 accordingly. Circumference length along machined worpiece 1 surface (Fig.3) is considerably more than cutting tool 3 feed per machined workpiece 1 revolution, i.e. π D » S. Thus cutting tool nose paths on two consequent revolutions differ slightly from sinusoids with equal frequency and amplitude shifted from each other along X axis by feed value and along Y axis by phase angle τ0. For cutting process interruption cutting tool 3 nose paths approach each other to the utmost at two consequent revolutions. Here condition is fulfilled: oscillation amplitude A necessarily is equal to feed value divided two times sinus of half τ0
S A=
2 sinτo/2
In considered case (Fig.2a) where τ0=π, oscillation amplitude A is half of feed A=0.5 S, this provides intermittent chips. Thus at τ=0, π, 2π (fig.2a) the cutting layer section P and micro asperity height are equal and coincide with even cutting positions.
At τ=π/2 (Fig.2b) cutting tool nose paths are located on the maximum distance from each other and at this moment micro asperity height h is maximal and is defined by the formula: micro asperity height h is equal to feed S double value times sinus of difference between cutting edge position main angle φ and workpiece 2 and angle amplitude A-\ times sinus of difference between cutting edge position additional angle φ-i referred to workpiece 2 and anyle amplitude Ai divided by sinus of the sum of the main and additional cutting edges position angles φ and φi minus angle oscillation amplitude double value; to add value of the distance from the cutting edge nose to oscillation axis lo times difference between one and cosine of angle amplitude Ai value
2S sin(φ-A1)sin(φ-A1) hmax= + lθ(1 - COSAi) sin(φ + φi - 2A-ι)
When τ =3π/2 (Fig.2c) the cutting tool nose paths touch or maximally ■approach each other. In this case the cutting layer section is minimal and it is defined according to the following formula: the minimal cutting layer section Pmin is equal to the squared difference between cutting depth t and distance l0 from the cutting tool nose to oscillation axis times difference between one and cosine of the angle oscillation amplitude Ai value times sinus of the angle oscillation amplitude Ai double value divided by the double product of the sine of the sum of main cutting edge position angle φ and angle oscillation amplitude Ai value and sine of the difference of main cutting edge position angle φ and angle oscillation amplitude Ai value:
[t - l0(1 - cosA1)]2*sin2Aι i mιn—
2sin(φ + A-ι)sin(φ - A^
It is seen from Fig.3 that Pmm area is not equal to zero but for appropriate over design consideration distances l0 the Pmιn value is sufficiently small and practically provides chips fracture when machining any material.
For considered turning machining operation of the workpiece 1 with angle oscillations of the said cutting tool 3 the oscillation loop 7 of said cutting tool 3 performs function of pendulum with oscillation shaft K. When inertia moment lxoy of the oscillation loop rectangular section movable part being equal to 0.0833 ml2 kg/mm2 a general turning rigidity C of the oscillation loop movable part is defined by formula:
(mlAω)'
C =
21 where: m - loop movable part mass, kg
I - loop movable part general length ω - oscillation rotational frequency, Hz
I - oscillation loop movable part inertia moment.
Upon this the said rigidity C provides cutting tool 3 amplitude A within 0.2-0.5 mm limits which is sufficient for reliable fraction of machined workpiece 1 chips.
The elasticity force F is derived from the relation Fy = C λ kg where: λ - movement value equal to oscillation amplitude value A.
By adjusting elastic elements 10, 10*and 10** rigidity, a sufficient oscillation loop 7 movable part and the cutting tool 3 removable cutting part 9 oscillation amplitude A value is provided. Thus reliable and stable chips fraction is achieved when machining workpiece 1. Application of oscillation loop 7 without oscillation axis K enables to get practically various oscillation loop schemes: - with axis oscillations of the movable part of the cutting part loop using elastic elements that provide linear movements only;
- with tool torsional oscillations, upon this for hole machining operation it is enough to install elastic element as torsion bar with torsion angle which provides reliable and stable chips fraction.
The use of cutting forces to perform oscillation loop vibrations of the proposed vibration cutting tool enables to completely exclude individual energy supply to the cutting tool and to exclude additional devices to perform cutting tool oscillations. The use of the proposed vibration cutting method when machining hardly machined steels, alloys, tenacious non-ferrous metals and composite materials enables to control quality performances of cutting process, machined surface micro asperity height thus providing high speed cutting with simultaneous stable and reliable chips fracture.
The presence of axis in the movable working forepart of the proposed cutting tool produces indispensable resistance forces for reduction oscillation amplitude of said cutting tool, i.e. provides automatic protection of cutting tool from overloads thus increasing its service life and makes all machining process more economically efficient.
Application of elastic elements in the proposed vibration cutting tool design enabled to increase cutting plate durability when machining above mentioned materials. Those skilled in this art will easily find that various configurations and modifications are applicable to above mentioned examples of the invention realization without departing from its scope which is formulated in proposed claims and is defined by these claims.