JP5785552B2 - Machine and method for grinding a workpiece - Google Patents

Description

  The present invention is directed to a machine tool such as a tool grinder, and more specifically, to a multi-axis, high-precision computer-controlled machine tool for grinding a second-tooth profile of a rotary cutting tool.

  When grinding tooth profiles of cutting tools, such as gear hobs, worm gear hobbs, hobbs with a constant normal normal pitch, and milling cutters with module sizes greater than 8 modules, A number of grinding wheels are used to finish the entire tooth profile of both tip features. As the module size increases from 8 to about 16, different approaches can be used for grinding, depending on the desired regrinding life of the finished tooth and the width of the tooth gap at the root of the profile. The tooth re-grinding life or the length of the tooth surface taken by the cam can be maximized by using a pencil-shaped tapered cone grinding wheel having a relatively small diameter compared to the length. The number of the toothed surface is the next to the next when the radial cam grinds the flank along the index position in the case of a tooth helix of a hob screw or in the case of a milling cutter. It depends on the point of interference of the grinding wheel with respect to the teeth of the wheel.

  Depending on the geometry of the tooth gap, there are practical limits on the surface speed for grinding and the weakness of the bending / shear strength of the tip of a pencil-shaped wheel that must be taken into account. . In addressing practical use restrictions in grinding with a pencil-shaped wheel, another grinding process may be employed that uses a cup-shaped grinding wheel having a relatively large diameter compared to the width. The surface speed of grinding and the strength of the part of the wheel that grinds the root part of the tooth are solved. However, a disadvantage of the cup-shaped grinding wheel is that its diameter is large, so that the length to the interference point of the tooth surface second picked up by the cam described above is limited. As the module size increases beyond 16 modules to a maximum of 50 modules, the use of cup-shaped wheels is limited because the wheels interfere with adjacent teeth as described. In most cases, a pencil-shaped taper-cone grinding wheel is used for hob tooth sizes of more than 16 modules in order to provide sufficient double-taken length of teeth for re-grinding life. Must be used.

  In current tool manufacturing practice, tooth flank, tip roundness, and tooth tip outer diameter are made from multiple grinding wheels and grinding wheel shapes to individually grind in multiple (up to 5 times) setups Use combining profiles. Using CNC machine operating technology and rotary reshaping / dressing equipment, for example, the radius / slope of the root part, the tooth pressure angle side, the roundness of the tip, and the tip roundness In order to embody a plurality of features, such as the outer diameter, it is possible to create the above-described pencil-shaped or cup-shaped grinding wheel outline. In the example mentioned, the finish grinding process can be reduced to combining two pencil-shaped or cup-shaped grinding wheel only profiles. Inspecting the profile using a probe such as Renishaw 3-D with acoustic contact sensing helps position the grinding wheel relative to the left and right tooth reference points, and Assist in combining the profiles to obtain the required tooth profile and tooth thickness.

  From the above, many tool manufacturing facilities use a plurality of grinders dedicated to either a pencil-shaped grindstone or a cup-shaped grindstone. In a few examples, machine tool designs are employed that allow the spindle assembly and drive mechanism to be interchanged to accommodate the physical orientation of either a pencil-shaped wheel or a cup-shaped wheel. In most cases, it is necessary to use a dedicated machine with a physical orientation that is possible with grinding only with a pencil-shaped wheel or with only a cup-shaped wheel. In most, if not all, cam relief motions on a machine tool, a single axis is used to perform the radial action of the cam second take. Limiting machine flexibility.

Buckingham, Earl, Spur Gears, McGraw-Hill Book Co. Inc. NY 1928

  The present invention can be positioned (turned) at an angle, thereby eliminating the need to replace the grinding spindle assembly or modify the machine configuration to accommodate two different grinding methods, Alternatively, a cup-shaped grinding wheel and pencil shape to grind the second tooth geometry of the hob and milling cutter without the need to use additional machine axes to redirect the spindle Machine tools with an angularly oriented spindle that provide the flexibility of using both grinding wheels.

It is a figure which shows the relationship of the setting advance angle of a cup-shaped grinding wheel and the profile of a hob tooth of a universal module size. It is a figure which shows the relationship of the setting advance angle of a cup-shaped grinding wheel and the profile of a hob tooth of a universal module size. It is a figure which shows the relationship of the setting advance angle of a cup-shaped grinding wheel and the profile of a hob tooth of a universal module size. It is a figure which shows the relationship of the setting advance angle of the grinding wheel of a pencil shape, and the hob tooth profile of a universal module size. It is a figure which shows the relationship of the setting advance angle of the grinding wheel of a pencil shape, and the hob tooth profile of a universal module size. It is a figure which shows the relationship of the setting advance angle of the grinding wheel of a pencil shape, and the hob tooth profile of a universal module size. FIG. 6 is a design diagram associated with a second scrambling operation with a radial cam from the front profile to the rear profile of the hob along the involute helicoid. It is a figure which shows the change of the pressure angle from the front part of the hob tooth profile of a fixed normal pitch to the rear part. FIG. 3 shows the relationship between the main components of the machine, the hob workpiece and the grinding wheel spindle assembly oriented to use a pencil-shaped grinding wheel and the direction of the second take by the cam. FIG. 3 shows the relationship between the main machine components, the hob workpiece, and the grinding wheel spindle assembly oriented to use a cup-shaped wheel and the direction of the second take by the cam. FIG. 3 is an enlarged view showing the grinding spindle assembly of the present invention in an operating position in the machine. FIG. 5 is an enlarged view showing an automatic wheel changing unit mounted on a machine base for changing a grinding wheel pack and coolant manifold between a grinding spindle mounting interface and a storage station.

  Before describing in detail any feature and at least one configuration of the present invention, the present invention is limited in its application to the details of configuration and component arrangement set forth in the following description or illustrated in the drawings. Please understand that it is not. The invention is capable of other configurations and may be practiced or carried out in various ways. It should also be understood that the expressions and terms used herein are for purposes of illustration and should not be considered limiting.

  The use of “comprising”, “having” and “including” and endings thereof herein is meant to encompass the items described below and equivalents thereof as well as additional items. The language used to identify elements of a method or process is for identification only and does not indicate that the elements are to be performed in a specific order.

  In describing the drawings, in the following, reference may be made to directions such as top, bottom, top, bottom, back, bottom, top, front, back, etc., but for convenience these references are To see). These directions are not meant to be taken literally or to limit the invention to any form. Further, in the present specification, terms such as “first”, “second”, “third” and the like are used for explanation, but these indicate importance or significance. Not intended.

  1 (a), 1 (b) and 1 (c) contact along an involute helicoid 2 of one of a series of continuous hob teeth 3 along a single or multi-threaded thread path 4. FIG. The angle relationship of the grinding wheel in the coordinate system in the case of the cup-shaped grinding wheel 1 is shown, and the hob tooth 3 has a thread involute helicoid 2 and a straight or spiral groove 6 intersecting. A tooth having a front profile 5 at the cutting surface defined by and having a length limited by an interference point 8 between the grinding wheel 1 along the involute helicoid 2 and the adjacent hob tooth 9 At the end of the grinding life near the end of the grinding life. The relationships defined in FIGS. 1 (a), 1 (b) and 1 (c) are: a grinding spindle assembly fixed angle HA (angle 10), a grinding wheel pressure angle PA (angle 11) and a hob tooth axis. The plane pressure angle APA (angle 12), the advance angles LAS1 and LAS2 of the involute helicoid 13 seen from the front, the set value 14 of the turning device mounting angle of the grinding head assembly seen from the front, and two values for the coordinate system It is the direction 15 of the taking.

  2 (a), 2 (b) and 2 (c) contact along an involute helicoid 17 of one of a series of consecutive hob teeth 18 along a single or multiple thread path 19. In the case of a pencil-shaped or conical-shaped grinding wheel 16, the angle relationship of the grinding wheel in the coordinate system is shown, and the hob tooth 18 has a threaded involute helicoid 17 and a linear or spiral groove 21. Has a front profile 20 at the cutting surface defined by the crossing and further limited in length by an interference point 23 between the grinding wheel 16 along the involute helicoid 17 and the adjacent hob tooth 24. It has a doubled rear profile 22 near the end of the grinding life of the tooth position being made. The relationships defined in FIGS. 2 (a), 2 (b) and 2 (c) are: the fixed angle 25 of the grinding spindle assembly, the pressure angle PA reshaped / dressed on the grinding wheel and the axis plane of the hob teeth. Setting of the difference angle B (angle 26) from the pressure angle APA (angle 27), the advance angles LAS1 and LAS2 of the involute helicoid 28 seen from the front, and the turning device mounting angle of the grinding head assembly seen from the front A value 29 and a second direction 30 with respect to the coordinate system.

  FIG. 3 shows a blueprint used to optimize the grinding wheel geometry to reduce deviation from the theoretical tooth profile with or without modification of the involute and the tooth pressure angle. It defines the inherent error of the hob tooth grinding wheel with respect to the joint contact point. The design blueprint is defined at the front 31 section, the midpoint of the cammed second section 32 and the rear 33 section. The associated nominal hob tip circle radius 34, nominal hob midpoint radius 35, and nominal hob radius 36 at the end of the sharpening life are further shown.

  FIG. 4 shows the specific error in the case of an involute profile hob tooth produced by a conventional machine tool manufacturing method. Theoretically, every time the hob is ground from front to back, another new hob is created. The ground hob only cuts the gear to a rough shape as a new hob. Further, when the hob is further ground backward, the error increases. FIG. 4 shows two axial sections of a hob tooth involute helicoid profile without any involute correction for illustration purposes, where the new hob along the tooth involute helicoid is shown. A theoretically exact front position 37 and a ground rear position 38 near the end of the grinding life are shown. A grinding wheel or forming tool with an originally fixed geometric profile is driven in a fixed path by the machine taking a second action to attempt to contact this helicoid surface in both sections 37 and 38. In this case, an inherent error 39 (error A and error B) occurs.

  An attempt to recognize and solve the inherent error problem described above is known from “Buckingham, Earl, Spur Gears, McGraw-Hill Book Co. Inc., NY, 1928”, where the involute helicoid special It has been considered that the tooth surface of the hob is secondly taken advantage of this property. In the disclosed method, the contact between the second picked surface and the grinding wheel becomes a linear bus of the involute helicoid, and the second picked surface itself becomes the involute helicoid. However, this method does not make corrections, such as semi-topping slope, involute correction, and protubal balance. In the case of a fine pitch hob, the inherent error can be ignored, and the magnitude of the error is not important even in the case of a low quality coarse pitch hob. For a precision hob, the inherent error location can be specified by the following equation:

  If the factor Q is greater than 20, this indicates the approximate range in which a hob with a linear axial profile cuts a gear that actually has a true involute profile. As factor Q decreases, the axial profile of the hob teeth becomes more curved and the potential for inherent errors increases.

  By analyzing the grinding wheel contact pattern with the modified tooth involute helicoid, the set angle, and the grinding wheel offset value, the grinding process can be optimized to reduce the inherent error. Errors cannot be excluded. The corrective action of the machine to change the pressure angle relationship during the second process can minimize the inherent error to an acceptable level, thereby providing a more precise and longer life hob. Is obtained. The grinding wheel head assembly 40 (FIG. 6) of the present invention can realize the vibration operation of the grinding wheel synchronized with the second picking operation in order to minimize the inherent error.

  The CNC controller (such as a Fanuc 160iB computer controller) of the grinding machine of the present invention can be used in the horizontal direction when the grinding head assembly is positioned near a horizontal plane in order to use a grinding cup-type wheel. Positioning near a vertical plane so as to perform a double cam action with a radial cam or offset radial cam from one axis moving in a plane, or to use a pencil-type grinding wheel for grinding Use multiple shafts to achieve a second take action by a cam, and a second take action by a radial cam or an offset radial cam at a compound angle with respect to a vertical plane, It is possible to operate. In addition, the grinding head assembly can transmit a vibration motion to the grinding wheel superimposed on a second picking motion by a radial cam or an offset radial cam, and this vibration motion is a function of turning the grinding wheel with respect to the pressure angle of the hob tooth profile. It serves to change the orientation, thereby reducing the tooth pressure angle at the rear of the hob teeth relative to the front and middle points of the doubled tooth profile. This operation makes it possible to produce hobbs with a constant tooth normal normal pitch that cannot be made with previous hob grinding of the present invention.

FIG. 5 shows a table 41, a direct motor drive headstock 42, a rotating center tailstock 43, a steady rest 44 to assist in loading the arbor assembly, and a workpiece holding arbor 45 (FIG. 6). ), A hob workpiece 46, a linear motor driven longitudinal slide assembly 47, a linear motor driven vertical slide assembly 48, and a linear motor driven horizontal radial feed slide. A moving assembly 49, a grinding spindle turning assembly 50 oriented to be ground with a pencil-shaped wheel, a tilted (preferably 25 degrees) grinding spindle housing 51 with a tool spindle 65, and a spindle mounting 1 shows a machine of the present invention having a pencil grinding wheel 52 with a type adapter 66. A vector 53 indicates a composite angle of the direction second counting operation (that is, the cam second counting operation). The headstock 42 and the longitudinal shaft sliding body 47 generate hob screw leads, and the vertical sliding assembly 48 and the horizontal sliding assembly 49 combine to generate a cam numbering action 53, and In order for the optional vibration of the grinding wheel turning assembly 50 superimposed on the cam picking operation 53 to minimize the inherent error in the pressure angle profile, the five axes need to be synchronized.

FIG. 6 includes a machine table 41, a direct motor driven headstock 42, a rotating center tailstock 43, a workpiece spindle 67, and a steady rest 44 to assist in loading the arbor assembly, Workpiece holding arbor 45, hob workpiece 46, linear motor driven longitudinal slide assembly 47, linear motor driven vertical slide assembly 48, linear motor driven horizontal diameter A tilted (preferably 25 degrees) grinding spindle housing comprising a directional feed slide assembly 49, a grinding spindle turning assembly 50 oriented to grind with a cup-shaped wheel, and a tool spindle 65 51 and a cup-shaped grinding wheel 55 having a spindle mounting adapter 66 are shown. A vector 56 represents a combined angle of the radial second numbering operation (that is, the second numbering operation by the cam). When the cam screw is second picked, the headstock 42 and the longitudinal slide body 47 are positioned so as to generate the hob screw lead, and the horizontal slide assembly 49 is second picked by the cam. To be positioned to generate 56, the three axes need to be synchronized. The offset set-up angle of the grinding wheel turning assembly 50 and the height of the vertical shaft 48 are held in a fixed position during the second camping process during grinding with the cup-type grinding wheel.

The grinding wheel head assembly 40 mounted for vertical motion is preferably a composite angle set as desired depending on the grinding wheel profile, cutter thread lead and grinding spindle orientation. Until now, it has a variable-speed high-frequency grinding spindle capable of automatically swinging a vertical arc surface of at least plus or minus 120 degrees. The grinding spindle housing 51 is oriented at a fixed angular position from the vertical pivot plane of the grinding wheel head 40 and is preferably about 25 degrees from the vertical plane, where the position of the grinding wheel is relative to the workpiece. Approaching, the direct drive motor of the tool spindle 65 is away from the workpiece.

The preferred 25 degree orientation of the tool spindle 65 creates an additional clearance between the motor housing 51 of the grinding spindle and the outer diameter of the workpiece when using a cup-shaped grinding wheel 55 (FIG. 6). In this case, the grinding wheel head 40 is positioned at a plus or minus about 30 degrees from the horizontal plane, where the double grinding is combined with a rotary action and a longitudinal action for a quick horizontal action. use. A suitable 25 degree oriented grinding spindle also assists the pencil shaped grinding wheel 52 (FIG. 5) with a grinding wheel head 40 positioned about 40 degrees plus or minus from the vertical plane. So that the double grinding operation uses both rapid vertical and horizontal motions in combination with rotational and longitudinal motions. In addition to the operations described, the grinding wheel head assembly can oscillate at a plus or minus about 3.5 degrees from the set angular position during the second picking operation, so that it is double picked. A rough normal dimension right angle normal pitch hob is obtained which has a modified tooth profile pressure angle at the back and even the front of the flank of the hob teeth. The grinding spindle is preferably a fixed 25 degree orientation, but the invention is not so limited. Other angular orientations are also contemplated and are within the scope of this disclosure.

  FIG. 7 shows a grinding wheel changing cabinet 57, a grinding wheel turning assembly 50 including an inclined grinding spindle 51, a probe 58 (eg, Renishaw 3D) for setup and inspection functions, and a rotation mounted on the table. And an additional mechanical configuration including a dresser (grindstone correcting device) assembly 59. For the hob automatic grinding process and the process of combining a plurality of wheel profiles, it is preferable to replace the grinding wheel pack attached to the spindle adapter during machine operation and to use the probe 58 to Use acoustic contact sensing to determine generally the position of the grinding wheel relative to the pitch point on the tooth flank and to confirm that the position of the grinding wheel profile is in contact with the current tooth profile of the hob And using a mechanical axis with acoustic contact sensing to generate a grinding wheel profile in a number of grinding wheel technologies (including superabrasives such as CBN) using a dresser 59 mounted on the table. Probing the ground profile to combine the profile with the wheel profile and to correct errors And measuring using a-system 58 includes a be feedback analyzed automatically to correct the errors in the profiles.

FIG. 8 shows an example of a grindstone and coolant manifold automatic changer 60 comprising a plurality of stations mounted on a rotating rack 61, which is mounted on a grinding spindle adapter. Store the grinding wheel pack (collectively 62) and the accompanying coolant manifold 63. A programmable sliding assembly 64 facilitates simultaneous exchange of the grindstone pack 62 and coolant manifold 63 between the grinding spindle 51 and multiple stations on the rack 61. A grindstone and coolant manifold automatic changer 60 (located in the cabinet 57) is attached to the machine tool to facilitate fully automatic grinding of the hob or milling cutter. This automatic wheel and coolant manifold changer can install a number of grinding wheels mounted on a spindle adapter with an associated coolant manifold, and between this device and the grinding spindle. The grinding wheel pack with the agent manifold can be replaced automatically, thereby automatically providing a number of wheels required to finish the entire tooth profile of the hob or milling cutter. The standard number of stations in this grindstone and coolant manifold automatic changer is preferably 8, but usable grindstones with coolant manifolds that are limited or only usable due to space constraints A magazine storage device may be connected to the grindstone and coolant manifold automatic changer to increase the number of packs. Probing systems (e.g., to perform post-grinding inspection with automatic correction feedback of profile paths for reshaping / dressing to perform tooth gap positioning settings for multiple grinding wheels Renishaw 3D) is incorporated. It is also contemplated to measure and report the quality of ground profiles in accordance with the currently accepted internationally accepted hob and milling cutter AGMA and DIN standards.

  The machine of the present invention is in the range of about 8 to about 50 module tooth sizes with a tooth cutting surface defined by a plurality of straight or spiral grooves (blade grooves), preferably an outer diameter of 200 mm More than 1 or multiple hobs can be ground. The machine also secondarily grinds a large milling cutter, preferably over 200 mm, with a tooth cutting surface with the teeth indexed axially and defined by a plurality of straight or spiral grooves. be able to. The machine preferably has a rotational motion, a vertical motion, a horizontal motion, a longitudinal motion, and a grinding head swivel motion as defined to pre-grind each tooth profile of the hob or milling cutter. Incorporates a fast response programmable axis driven directly by a linear motor, using precise position feedback with a glass scale in combination with Hobs and milling cutters having tapered outer diameters or outer diameters that are contoured can also be ground. Multiple grinding wheels may be required to grind each tooth space to finish left and right flank, tip roundness and tip circle diameter.

  Although the invention has been described with reference to preferred embodiments, it should be understood that the invention is not limited to the features of these preferred embodiments. The present invention is intended to include modifications which will be apparent to those skilled in the art to which the subject matter pertains without departing from the spirit and scope of the appended claims.

Claims (15)

A machine for grinding rotary cutting tools ,
Table,
A workpiece spindle for rotating the rotary cutting tool about the workpiece axis;
A tool spindle for rotating the tool about the tool axis;
A vertical sliding assembly having a first side facing the workpiece spindle;
The tool spindle is located on the first side and is vertically movable along the first side of the vertical sliding assembly, and the tool spindle is on the first side. Can pivot about a pivot axis extending generally vertically to the
The machine wherein the tool spindle is tilted relative to the first side and oriented at a predetermined tilt angle.   The machine of claim 1, wherein the vertical sliding assembly is located on the table and is movable in at least one of a longitudinal direction of the table and a width direction of the table.   The machine of claim 1, wherein the tilt angle is 25 degrees.   The machine of claim 1, wherein the tool has a grinding wheel in the shape of a pencil tip.   The machine of claim 1, wherein the tool has a cup-shaped grinding wheel. The machine of claim 1, wherein the tool spindle is located in a pivot assembly and a probe is positioned on the pivot assembly.   The machine of claim 1, further comprising a grindstone and coolant manifold automatic changer having a plurality of tool storage stations.   The machine of claim 1, wherein the machine is operable to achieve at least one of a radial cam action and an offset radial cam action of the tool relative to the workpiece.   The machine of claim 8, further operable to superimpose the at least one of a radial cam motion and an offset radial cam motion to further convey a vibration motion of the tool. The machine according to claim 1, wherein the rotary cutting tool has a single-row bob, a multi-row hob or a milling cutter. A method of grinding a rotary cutting tool using a grinding wheel on a grinder,
Rotating the rotary cutting tool about the axis of the workpiece;
Rotating the grinding wheel about the axis of the tool;
Causing relative movement between the rotary cutting tool and the grinding wheel in a maximum of three directions perpendicular to each other;
Pivoting the grinding wheel about a pivot axis, wherein the pivot axis is perpendicular to a first side oriented in a vertical direction of a vertical sliding assembly on the grinder; The first side faces the rotary cutting tool and the grinding wheel is tilted relative to the first side and is oriented at a predetermined tilt angle; and
Engaging the grinding wheel and the rotary cutting tool with each other to move the grinding wheel and the rotary cutting tool relative to each other to perform at least one of a radial cam operation and an offset radial cam operation. Moving , thereby providing a clearance surface on the teeth of the rotary cutting tool .   The method of claim 11, further comprising vibrating the grinding wheel and superimposing the vibration on the at least one of a radial cam operation and an offset radial cam operation.   The method of claim 11, wherein the tilt angle is 25 degrees.   The method of claim 11, wherein the grinding wheel comprises one of a pencil-shaped grinding wheel or a cup-shaped grinding wheel. The method according to claim 11, wherein the rotary cutting tool comprises a single-row bob or a multi-row hob or a milling cutter.