1. Field of the Invention
The present invention relates to a precision roll turning lathe which can machine a three-dimensional pattern, consisting of three-sided or four-sided pyramids arranged in a matrix, in the peripheral surface of a roll.
2. Background Art
Roll grinders and roll turning lathes are generally used as machine tools for machining rolls. A roll grinder includes a headstock, a tail stock, and a carriage which is provided with a grinding wheel.
Such a roll grinder can carry out grinding with a grinding wheel of the peripheral surface of a roll and, in addition, machining of grooves in the peripheral surface. Japanese Patent Laid-Open Publication No. 2003-94239 describes a roll grinder which is provided, in its carriage, with a groove-machining device having a cutting saw blade for groove cutting.
A roll turning lathe is a lathe in which a tool post, having e.g. diamond tools attached thereto, is mounted in a carriage, and is basically used for machining circumferential grooves on a roll by rotating the roll with a headstock and feeding the carriage in the lateral direction (X-axis direction) of the roll. When machining axial grooves on a roll, the carriage is moved at a high speed in the longitudinal direction (Z-axis direction) of the roll while indexing the roll with the headstock (C axis), thereby producing the axial grooves.
The recent progress of machine control technology has realized ultraprecision machining with a lathe, and it has become possible to machine even with a lathe a mold for molding an optical lens. For example, the applicant has proposed a vertical lathe capable of machining a mold for molding of a Fresnel lens (Japanese Patent Laid-Open Publication No. 2004-358624). The vertical lathe can machine with high precision V-shaped lens grooves of a mold for molding of a Fresnel lens.
Owing to the widespread use of liquid crystal displays, there is an increasing demand for lens sheets for use in a backlight of a liquid crystal panel. Such lens sheets include, besides the above-mentioned Fresnel lens, a lenticular lens sheet, a cross lenticular lens sheet, a prism sheet, etc.
Molding a lenticular lens sheet, a cross lenticular lens sheet or a prism sheet by extrusion molding using a transfer roll has recently been studied.
In the case of a transfer roll for the production of a lenticular lens sheet, it is only necessary to machine with precision circumferential grooves at a predetermined pitch in the peripheral surface of the roll. Such machining is possible even with a conventional common roll turning lathe.
On the other hand, in the case of a transfer roll for a cross lenticular lens sheet or a prism sheet, it is necessary to machine a three-dimensional pattern of four-side pyramids or three-sided pyramids on the roll.
For machining of a pattern of four-sided pyramids, cutting of circumferential grooves and axial grooves in a matrix pattern in the surface of a roll is being studied. As regards machining of a pattern of three-sided pyramids, a method is being studied which involves machining axial grooves in combination with spiral grooves in the peripheral surface of a roll. However, the conventional roll lathe has not successfully matched for such ultra-precise machining.
It is therefore an object of the present invention to solve the above problems in the prior art and provide a precision roll turning lathe which can machine with high precision a three-dimensional pattern of three-sided pyramids or four-sided pyramids in the surface of a roll.
In order to achieve the object above, the present invention features a precision roll lathe which comprises: a bed; a head stock, mounted on the bed, including a main spindle for providing rotation for a roll as a work while holding one end of the roll by means of a chuck, and having an indexing axis (C axis) adapted to index the roll in the circumferential direction; a tail stock which is located on the bed to be opposed to the head stock, and is adapted to rotatably support the other end of the roll; a carriage including a saddle mounted on the bed movably in the longitudinal direction (Z axis) of the roll, and a table mounted on the saddle movably in the direction (X axis) perpendicular to the longitudinal direction of the roll; and a tool swivel mounted on the table; a tool post mounted on the tool swivel and having a cutting tool attached thereto, wherein the tool post is provided with a tool turning axis (A axis) for turning the cutting tool such that, when machining a spiral groove on the circumferential surface of the roll, a cutting face of the cutting tool is oriented to be perpendicular to the direction along which the spiral groove extends.
According to the present invention, with a roll process employing a combination of a spiral groove and a longitudinal groove formed in a roll, a pattern including three-sided pyramids which are successively arranged in both the longitudinal and transverse directions can be formed on the surface of the roll. Furthermore, in the case of forming the three-sided pyramids, since a B axis of the tool post has a function for correcting and determining the position of the cutting face of the tool, in addition to an indexing function, a precisely machined face with the spiral groove can be obtained.
Preferred embodiments of the present invention will now be described with reference to the drawings.
In
The headstock 12 is disposed on one longitudinal end of the bed 10. The headstock 12 includes a body 17, a main spindle 18, a chuck 19 secured to the front end of the main spindle 18, and a servo motor 20 for driving the main spindle 18. The main spindle 18 is supported by a not-shown hydrostatic oil bearing provided within the body 17. The chuck 19 holds a spindle of the roll W and transmits the rotation of the main spindle 18 to the roll W.
In the head stock 12, the servo-motor 20 drives the main shaft 18 so as to rotate the roll W at a high speed. In addition to this function, the head stock 12 is provided with an additional function to serve as an indexing axis (C axis) adapted to index the roll W in the circumferential direction by detecting the amount of rotations of the servo-motor 20 by using an encoder 22 and controlling the rotations of the servo-motor 20. The bearing for the head stock 12 may be a pneumatic bearing or a mechanical bearing, rather than the hydrostatic pressure bearing.
Next, the tail stock 14 is disposed on the bed 10 and opposite to the headstock 12. A not-shown guide surface is provided on the upper surface of the bed 10 so that the tail stock 14 can be moved along the guide surface. The tail stock 14 has a main spindle 24 instead of a conventional common tail spindle, and ratatably supports a spindle of the roll W by means of a chuck 25 mounted to the main shaft 24. Such a tail stock 14 basically has the same construction as the headstock 12 except for having no servo motor.
A description will now be given of the carriage 16.
The carriage 16 includes a saddle 26 mounted on the bed 10 movably in the axial direction of the roll W. On the saddle 26 is mounted a table 28 movably in a direction perpendicular to the axial direction of the roll W. In the precision roll turning lathe of this embodiment, the axis along which the saddle 26 is fed is termed Z axis, and the axis along which the table 28 is fed on the saddle 26 is termed X axis.
On a top board 32 of the tool swivel 30, a tool post 33 is detachably mounted. The tool post 33 has an integral structure which is formed, with a tool holder 34, a bearing 35, a reduction gear 37 and a servo-motor 38, into a unit. The tool post 33 can be optionally attached to or removed from the top board 32.
In the tool holder 34, a diamond tool 36 as a cutting tool is held. The shaft of the tool holder 34 is rotatably supported by the bearing 35. The output shaft of the reduction gear 37 is connected with the bearing 35, while the servo-motor 38 is connected with the input shaft. Accordingly, the rotation of the servo-motor 38 is transmitted to the tool holder 34 after decelerated by the reduction gear 37. As will be described below, with control due to the servo-motor 38, the A axis is defined around which the diamond tool 36 is turned.
In
A drive shaft 50 is attached coaxially to the top board 32. A built-in type servo-motor 51 is incorporated in the swivel body 31 together with a stator 51b, with a rotor 51a of the servo-motor 51 being fixed to the drive shaft 50. In this manner, the B axis is defined to index the diamond tool 36 on the tool post 33 to rotate the drive shaft 50 driven by the servo-motor 51 and turning the tool post 33 together with the top board 32.
Referring to
A Z-axis feed drive device for feeding the saddle 26 and an X-axis feed drive device for feeding the table 28 on which the tool swivel 30 is mounted are each comprised of a linear motor. In
In
Next, a rolling process using the precision roll turning lathe constructed as described above will be described.
As shown in
However, in
In the tool post 33 of this embodiment, however, since the A axis for indexing the direction of the cutting face of the diamond tool 36 is provided, as shown in
Machining of the first spiral grooves 64 will now be described. The first spiral grooves 64 can be machined with a diamond tool 36 while rotating the roll W in the direction of arrow A shown in
Next, the second spiral grooves 65, intersecting with and reversely spiraling to the first spiral grooves 64, can be machined by reversely rotating the roll W in the direction of arrow 3 shown in
After thus machining the first spiral grooves 64 and the second spiral grooves successively, the longitudinal groove 62 is machined as shown in
In
The fly cutter spindle device 71 includes a body 71a, a servo motor 75, and a cutter holder 76 having a fly cutter 77 attached thereto. A not-shown cutter spindle is supported by an air bearing in the interior of the body 71a. The cutter spindle is directly driven by the servo motor 75 and rotates at a high speed. The cutter holder 76, which is mounted to the front end of the cutter spindle, is disk-shaped so as to increase the circumferential speed. The fly cutter 77, comprised of a diamond tool, is held on the peripheral surface of the cutter holder 76. In this embodiment the cutter spindle device 71 supports the cutter spindle in a vertical position with respect to the X-axis direction and to the Z-axis direction, and rotates the fly cutter 77 at a high speed in the X-Z plane. The cutting edges of the diamond tools 36, mounted in the tool post 33, lie in the same X-Z plane in which the fly cutter 77 rotates.
Since the fly cutter spindle device 71 is installed at the tool post 70 as described above, the longitudinal groove 62 can be formed in the following manner.
Namely, the fly cutter spindle device 71 is first indexed by using the B-axial function, and the circumferential position to be machined of the longitudinal groove 62 of the roll W is then indexed by using the C-axial function.
To this end, the fly cutter spindle device 71 is driven and rotated at a high speed, while the fly cutter 77 is cut through the roll W in the X-axial direction. In this state, the longitudinal groove 62 can be formed by cutting the roll W due to the fly cutter 77, while the carriage 16 is fed in the Z-axial directional. Since this process can be performed while providing an optimum cutting speed (approximately 300 m/minute) to the fly cutter 77, the longitudinal groove 62 can be formed with high accuracy. Thereafter, other longitudinal grooves 62 are formed at a constant pitch in succession such that they pass through each crossing point of the spiral grooves 64, 65, while each cutting position of the roll W is indexed by utilizing the C-axial function (see
As stated above, by utilizing the tool post 33 and the tool post 70 for different purposes, the three-sided pyramids pattern as shown in
Number | Date | Country | Kind |
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2006-165144 | Jun 2006 | JP | national |