JP6612696B2 - Dressing method and workpiece grinding method - Google Patents

Description

  The present invention relates to a grinding wheel dressing method and a workpiece grinding method used in a grinding machine.

  When grinding a large amount of workpieces in grinding metal or the like, the grinding accuracy decreases due to clogging or wear of the grindstone. Therefore, conventionally, when the grinding of a preset number of workpieces is finished, the dressing device is sent toward the grindstone, the dress diamond held by the dressing device is cut into the grinding surface of the grindstone, and dressing is performed, A process for restoring the sharpness of the grindstone has been generally performed.

  By the way, in an internal grinder or the like, a disc-shaped or cylindrical grindstone rotates around a grindstone axis to perform grinding. As the accumulated grinding amount of the workpiece increases, the outer peripheral surface, which is a grinding surface, retreats inward in the radial direction due to wear, and the grindstone diameter decreases. In order to secure a sufficient dressing amount when dressing the grindstone, it is necessary to adjust the dress start time in consideration of a decrease in the grindstone diameter.

  As an example of a dressing method in consideration of the reduction in the grindstone diameter, Patent Document 1 discloses a technique for continuously shortening the dress interval in accordance with the reduction in the grindstone diameter (see FIG. 5).

  Patent Document 2 discloses a technique for measuring the diameter of a grindstone using a non-contact displacement meter and performing dressing when the reduction amount reaches a certain value.

JP 54-101591 A Japanese Utility Model Publication No. 2-33954

  However, as disclosed in Patent Document 1, in the method of continuously shortening the dress interval according to the decrease in the grindstone diameter, the grindstone diameter is maintained to a certain extent with respect to its initial value. There was a risk of dressing too much than necessary. Moreover, the dressing to the grindstone more than necessary leads to the shortening of the grindstone replacement cycle, leading to a decrease in productivity. Moreover, in the technique disclosed in Patent Document 2, a separate measuring instrument is required to measure the grindstone diameter, which may lead to complicated equipment and increased equipment costs.

  The present invention has been made in view of such points, and an object thereof is to stabilize the grindstone dress by a simple method, to extend the life of the grindstone and to maintain the grinding accuracy of the workpiece.

In order to solve the above problems, a dressing method of the present invention is a dressing method for dressing a grindstone held on a grindstone shaft by using a dressing apparatus, and the grindstone of the grindstone in a new state or after trial grinding The same dressing interval is maintained until the grindstone diameter ratio, which is the ratio of the grindstone diameter of the grindstone after repeating the grinding of the diameter and the workpiece and the dressing of the grindstone, reaches a predetermined value, and the grindstone diameter ratio is The dress interval is shortened discontinuously when it becomes less than the predetermined value, the predetermined value is 0.92, and the grinding number of workpieces and the wheel diameter ratio at the dress interval until the wheel diameter ratio becomes 0.92 The ratio of the grinding number of workpieces in the dress interval immediately after the value of 0.92 is 0.6 is 0.6 .

According to this method, the same dressing interval is maintained until the grindstone diameter ratio reaches a predetermined value, and when the grindstone diameter ratio falls below the predetermined value, the dressing interval is shortened discontinuously, and one dressing interval is obtained. By reducing the number of workpieces processed in step 1, excessive dressing at the initial stage of use of the grindstone can be prevented, and the life of the grindstone can be extended. Further, the grinding accuracy is stable over a wide range of the wheel diameter.

Another dressing method of the present invention is a dressing method of dressing a grindstone held on a grindstone shaft by using a dressing apparatus, and grinding the grindstone diameter and workpiece of the grindstone in a new state or after trial grinding. And the grindstone diameter ratio, which is a ratio of the grindstone diameter of the grindstone after repeating the grindstone dress, to the predetermined value, the same dress interval is maintained, and the grindstone diameter ratio is less than the predetermined value. At this point, the dressing interval is shortened discontinuously, and after the dressing interval is shortened discontinuously, the dressing interval is shortened continuously according to the decrease in the grindstone diameter .

Still another dressing method of the present invention is a dressing method in which a dressing device is used to dress a grindstone held on a grindstone shaft, and the grindstone diameter of the grindstone and the workpiece in a new state or after trial grinding are used. The same dress interval is maintained until the grindstone diameter ratio, which is the ratio of the grindstone diameter after repeating grinding and dressing of the grindstone, reaches a predetermined value, and the grindstone diameter ratio is equal to or less than the predetermined value. After the dressing interval is shortened discontinuously and the dressing interval is shortened discontinuously, the dressing interval is shortened continuously in accordance with the decrease in the grindstone diameter, and the predetermined value is 0.92. The ratio of the number of workpieces ground at the dress interval until the grindstone diameter ratio reaches 0.92 and the number of workpiece grinds at the dress interval immediately after the grindstone diameter ratio reaches 0.92 is 0.6. It is characterized by that.

  According to these methods, the grinding accuracy is stabilized over a wide range of the wheel diameter. Moreover, the fall of the grinding precision with respect to the reduction | decrease of a grindstone diameter can be prevented better.

  The workpiece grinding method of the present invention includes a step of dressing a grindstone by any one of the above dressing methods and a step of grinding the workpiece using the dressed grindstone.

  According to this method, it is possible to grind a workpiece with stable grinding accuracy even when using a grindstone that has become an allowable limit in the conventional method.

  According to the said structure, since the lifetime of a grindstone can be achieved and it becomes possible to extend the replacement period of a grindstone, productivity improves and production cost can be suppressed.

It is the schematic of the internal grinding machine in embodiment of this invention. It is a figure which shows the relationship between the grindstone diameter and dress space | interval in embodiment of this invention. It is a figure which shows the relationship between the grindstone diameter ratio and workpiece | work workpiece surface roughness ratio in embodiment of this invention. It is a grinding flowchart of a work in an embodiment of the present invention. It is a schematic diagram which shows the relationship between the grindstone diameter and dress space | interval in a prior art.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the following description of the preferred embodiment is merely illustrative in nature.

  In this specification, a period between a dress and the next dress is referred to as a dress interval.

(Embodiment of the Invention)
FIG. 1 is a schematic view of an internal grinding machine in the present embodiment.

  The internal grinding machine 1 moves the grindstone shaft 3 in the XY directions shown in FIG. 1, the grindstone shaft 3 that fixes and holds the grindstone 2, the grindstone shaft rotation mechanism 4 that rotates the grindstone shaft 3 around its central axis. And a grindstone shaft feed mechanism 5 to be operated.

  Further, the internal grinding machine 1 includes a chuck device 7 that fixes and holds the workpiece 6, a workpiece spindle 8 that rotates the workpiece 6, and a workpiece spindle rotating mechanism 9 that rotates the workpiece spindle 8 around its central axis. ing. The in-line sizing device 10 is set so that the inner diameter of the workpiece 6 before and during grinding is measured in-line, and the output becomes zero when the inner diameter of the workpiece 6 reaches the target dimension. Details of the inline sizing device 10 are not shown.

  The dressing device 11 has a dress diamond 12 made of single stone diamond or the like at the tip. When performing dressing, the grindstone shaft 3 moves in the XY directions and comes into contact with the outer peripheral surface of the grindstone 2 and the dress diamond 12. A feed mechanism (not shown) for moving the dress diamond 12 is provided.

  The grindstone shaft 3, the grindstone shaft rotation mechanism 4, the grindstone shaft feed mechanism 5, the chuck device 7, the work spindle 8, the work spindle rotation mechanism 9, the in-line sizing device 10, and the dressing device 11 Both are arranged on a bed (not shown).

  The grinder control device 13 controls the operation of the grinding wheel shaft rotating mechanism 4, the grinding wheel shaft feeding mechanism 5, the work spindle rotating mechanism 9, and the feeding mechanism of the dressing device 11, and the grinding wheel 2 and the grinding wheel shaft 3. In order to calculate the respective positions of the workpiece 6, the workpiece spindle 8, and the dressing device 11, an input unit 14, an arithmetic processing unit 15, a storage unit 16, a drive control unit 17, an operation panel 18, A display unit (informing unit) 19 is provided.

  Signals relating to these positions and operation states are input to the input unit 14 from the grindstone shaft rotation mechanism 4, the grindstone shaft feed mechanism 5, the work spindle rotation mechanism 9, and the feed mechanism of the dressing device 11. An output signal from the inline sizing device 10 is also input. Moreover, it has the electric power monitoring part (not shown) which detects and monitors the electric power of the grindstone shaft rotating mechanism 4.

  The arithmetic processing unit 15 receives a signal from the input unit 14 or a signal held in the storage unit 16 to calculate the position of the grindstone shaft 3, the dressing device 11, and the like, and outputs an output signal from the inline sizing device 10. Based on this, an operation control signal for the grindstone shaft 3 and the dressing device 11 is output.

  The storage unit 16 stores a signal from the input unit 14 or an output signal from the arithmetic processing unit 15, and outputs data necessary for the arithmetic processing to the arithmetic processing unit 15 in response to a request from the arithmetic processing unit 15.

  The drive control unit 17 receives a signal from the arithmetic processing unit 15 and sends a control signal to a drive circuit (not shown), the grindstone shaft rotation mechanism 4, the grindstone shaft feed mechanism 5, the work spindle rotation mechanism 9, and the dressing device. The operation with 11 feeding mechanisms is controlled.

  The operation unit 18 is used, for example, to directly input the position coordinates of the grindstone shaft 3, the workpiece 6, the dressing device 11, the target dimension of the workpiece, and the like. The grinding program is called and entered through the operation unit 18.

  The display unit 19 displays input data and the called program, the operating state of each mechanism during grinding, the position of the grindstone shaft 3, the dimensions of the workpiece 6 during grinding, and the like on the screen. It also functions as a notification unit that notifies the operator of the state of the device through a display screen, alarm lamp, audio output, or buzzer sound, etc. when work lot processing ends, device abnormality or program error occurs. To do.

  When the data input / output of the grinding machine is managed on the system, a signal notifying the system of the end of processing or abnormality is transmitted.

  Next, the relationship between the grindstone diameter and the dress interval in this embodiment will be described.

  FIG. 2 is a schematic diagram showing the relationship between the grindstone diameter and the dressing interval in the embodiment of the present invention.

  The step-like line represented by a in the figure shows the relationship between the grindstone diameter and the dress interval in the embodiment of the present invention.

  A step-like line represented by b in the figure and a line formed by combining straight lines show another example of the relationship between the grindstone diameter and the dressing interval in the embodiment of the present invention.

  The straight line represented by c in the figure shows the relationship between the grindstone diameter and the dressing interval in the conventional method shown in FIG.

  Here, the area of the region surrounded by the vertical and horizontal axes and the lines a, b, or c in the figure corresponds to the number of workpieces ground with the same grindstone. In other words, the area corresponds to the life of the grindstone, and it can be said that the larger the area, the longer the life of the grindstone.

  As can be seen from FIG. 2, the dress interval is kept constant regardless of the decrease in the grindstone diameter until it becomes a constant value, rather than continuously shortening the dress interval according to the decrease in the grindstone diameter (corresponding to the line c). In addition, when the predetermined grindstone diameter is reached, the above-described area can be increased by shortening the dress interval discontinuously (corresponding to the line a). That is, the life of the grindstone can be extended.

  The initial dress interval, the changed dress interval, and the setting of the grindstone diameter when changing the dress interval are appropriately determined according to the grindstone life and the grinding accuracy of the workpiece.

  FIG. 3 is a diagram showing the relationship between the grindstone diameter ratio and the workpiece work surface roughness ratio in the present embodiment.

  Here, the ratio of the grinding wheel diameter is the ratio of the grinding wheel diameter in the new state (initial grinding wheel diameter) to the ratio of the grinding wheel diameter after repeating the workpiece grinding and dressing (grinding wheel diameter after dressing). Diameter). However, the initial grindstone diameter may be the grindstone diameter after trial grinding.

  In addition, when the roughness of the first workpiece surface after grinding is first set to the initial roughness after dressing on the grindstone, the workpiece workpiece surface roughness ratio is the initial roughness and workpiece grinding. The ratio (roughness before dressing / initial roughness) to the roughness of the workpiece surface after dressing (roughness before dressing).

  In addition, the roughness of the workpiece surface was evaluated by arithmetic average roughness (Ra).

  The allowable limit of the workpiece work surface roughness ratio is indicated by a broken line, and in the conventional method corresponding to the line c in FIG. 2, the grindstone diameter ratio (the minimum grindstone diameter ratio) when the workpiece work surface roughness ratio reaches the allowable limit. (Conventional)) is indicated by dotted lines in FIG. The allowable limit value of the workpiece surface roughness ratio at this time was about 2.2.

  As shown in FIG. 3, when the data is above the broken line, the workpiece is a defective product. In the conventional method, when the minimum grindstone diameter ratio (conventional) is smaller than about 0.91, NG, that is, a defective product is generated.

  On the other hand, in FIG. 3, points indicated by black circles are data when the dress interval is changed by a method corresponding to the line a in FIG.

  In the present embodiment, the same dressing interval is maintained until the grindstone diameter ratio is about 0.92, and the dressing interval is set to be shortened at a timing lower than that. The ratio of the number of workpieces ground at the initial dress interval to the number of workpieces ground after the dress interval is changed is set to about 0.6.

  As shown in FIG. 3, in the method according to the present embodiment, even if the grindstone diameter ratio is less than 0.9, the workpiece surface roughness ratio does not increase significantly, and machining defects do not occur. That is, it can be seen that the grinding accuracy is not lowered even when grinding is performed in a state where the grindstone diameter is greatly reduced as compared with the conventional method.

  As described above, according to the method of the present embodiment, it is possible to extend the life of the grindstone as compared with the conventional method in which the dress interval is continuously shortened in accordance with the decrease in the grindstone diameter, and the grinding accuracy is the same as the grindstone diameter. Stable over a wide range of.

  Here, the method indicated by the line b will be described. In general, when the grindstone diameter decreases, the area of the grindstone that comes into contact with the workpiece during one rotation is reduced, and the linear velocity at the contact surface is also reduced. Therefore, when grinding a workpiece having the same grinding allowance, it is necessary to rotate more with a grindstone having a small grindstone diameter. In this case, compared with the case where the diameter of the grindstone is large, the wear of the grindstone becomes remarkable, and the dress interval is shortened.

  Therefore, when the grindstone diameter decreases below a certain level, it may be possible to prevent a decrease in grinding accuracy by continuously shortening the dress interval in accordance with the decrease in the grindstone diameter.

  In such a case, the method indicated by line b may be more suitable for actual production than the method indicated by line a.

  Next, the dressing method and the workpiece grinding method of the present invention will be specifically described with reference to flowcharts.

  FIG. 4 is a workpiece grinding flowchart in the present embodiment.

  First, when the first machine is started up, the grindstone 2 and the workpiece 6 are manually positioned. Similarly, manual positioning is performed when trial grinding is performed before the start of lot processing. The grindstone diameter is measured with a gauge or the like. When exchanging the grindstone, it is calculated based on the position coordinates as follows.

  The grinding wheel diameter and the finish target dimension of the workpiece 6 are respectively input to the input unit 14 via the operation unit 18 and stored in the storage unit 16. Similarly, the position of the grindstone shaft 3 determined by the positioning, the position of the workpiece 6, and the position of the dress diamond 12 are also input to the input unit 14 via the operation unit 18 and stored in the storage unit 16. At this time, the position of the grindstone shaft 3, the position of the workpiece 6, and the position of the dress diamond 12 are determined based on the position coordinates of the dressing device 11. Various positions appearing thereafter are also calculated based on the position coordinates of the dressing device 11. The position coordinates at the time of initial positioning can also be used as a reference.

  After the first dressing, the grindstone diameter is derived based on the position of the grindstone shaft 3 and the position of the dressing device 11 (step S1). Instead of obtaining the grindstone diameter from the position coordinates of each part as described above, a new grindstone diameter can be obtained by subtracting the dress amount from the grindstone diameter before dressing.

  Next, the inner diameter of the workpiece 6 before grinding is measured by the inline sizing device 10 (step S2). Based on the measurement result, it is determined whether the machining allowance of the workpiece 6 is abnormal (step S3).

  If the machining allowance is too small, grinding may not be performed sufficiently and the workpiece may become a defective product.

  If the machining allowance is excessive, the grindstone may come into contact with the workpiece when the grindstone is fast-forwarded, and the grindstone may break or the grinding machine may break down.

  In step S3, the workpiece whose machining allowance is determined to be abnormal is discharged as a defective product, or the display unit (notification unit) 19 notifies a nearby worker to see whether an appropriate workpiece is set. Ask for confirmation.

Next, the grindstone 2 is fast-forwarded toward the inner surface of the workpiece 6. After the rapid feed, the feed speed of the grindstone 2 is decreased and the grindstone 2 is continuously fed toward the inner surface of the workpiece 6. In the present embodiment, the period from the end of rapid feed to the contact between the grindstone and the workpiece, which will be described later, is referred to as “quasi-rapid feed”. When the grindstone 2 and the workpiece 6 come into contact with each other, the load power of the grindstone shaft rotating mechanism 4 rapidly increases. This change is monitored by a power monitoring unit (not shown) in the input unit 14, and when the load power increase value is a predetermined value or more, it is determined that the grindstone 2 and the workpiece 6 are in contact with each other. Thereafter, the workpiece is ground by changing the feed speed of the grindstone 2. Grinding is performed in the order of grinding (hereinafter referred to as “black skin grinding”) to remove the surface-modified part of the workpiece, rough grinding, finish grinding, and spark-out, and this switching is performed to the dimension measured by the in-line sizing apparatus 10. Determine based on. The feed speed of the grindstone 2 is in the order of (rapid feed)> (semi-rapid feed)> (black skin grinding)> (rough grinding)> (finish grinding). In the spark-out, the grindstone 2 is not cut into the workpiece 6 (step S4).

  The position B1 at which it is determined that the grindstone 2 and the workpiece 6 are in contact with each other is obtained by detecting the position of the grindstone shaft 3 based on the position coordinates of the dressing device 11.

  When the inline sizing device 10 outputs a zero point, the grinding of the workpiece is completed.

  When the workpiece grinding is completed, it is determined whether the lot processing has been completed based on the number of grinding processes counted so far (step S5). If the lot processing has been completed, the process is ended. If not, it is determined whether the dress start time has been reached (step S6). If the dress start time has not been reached, the ground workpiece is removed and the next The workpiece is set, and the process proceeds to dimension measurement before grinding (step S2).

  In the present embodiment, the number of processing is counted when grinding is completed.

  The dress start timing depends on the material of the grindstone, the grindstone diameter, the number of workpieces to be processed, the cumulative amount of workpiece grinding, and the like, and is determined in consideration of these factors.

  If the dress start time has been reached, dressing is performed (step S7).

  The grindstone shaft 3 is fed into the dress diamond 12 by a predetermined feed amount, and the dress diamond 12 is cut into the outer peripheral surface of the grindstone 2 for dressing. When step S7 is completed, the process returns to step S1, and the grindstone diameter is recalculated based on the position of the grindstone shaft 3 and the position of the dressing device 11. The recalculated grindstone diameter is stored in the storage unit 16. Further, the position of the grindstone shaft 3 is corrected using the recalculated grindstone diameter.

Next, it is determined whether or not the dress interval change timing has been reached (step S8).
If the dress interval change timing has not been reached, the process proceeds to step S2 to measure the inner diameter before starting grinding.

  If the dress interval change timing has been reached, the interval to the next dress is changed based on the calculated grinding wheel diameter (step S9). If step S9 is completed, it will progress to step S2 and will measure the internal diameter before a grinding start.

  After step S2, the process proceeds to grinding of the workpiece 6 in sequence, but the number of workpieces scheduled to be ground by the next dress has been changed at the time of step S9 and reaches the dress start time at an interval shorter than the previous dress interval. To do.

  In addition, if the calculated grindstone diameter is approaching the grindstone replacement limit, the operator or system in the vicinity of the grinding machine 1 is informed via the display unit (notification unit) 19.

  According to this embodiment, when the grindstone diameter is maintained to a certain extent, the dressing interval is not changed, and a fixed number of workpieces are ground at each dressing interval, and the grindstone diameter is reduced to a predetermined value. By shortening the dress interval from that point and reducing the number of workpieces to be processed in one dress interval, excessive dressing at the initial use of the grindstone can be prevented and the life of the grindstone can be extended. As a result, productivity can be improved and production cost can be reduced.

  In the present embodiment, the structure of the inline sizing device is not limited to a gauge, and other configurations such as an optical measurement system may be used.

  Moreover, although the example which dresses a grindstone using a dress diamond was shown, you may use a disk shaped or cylindrical rotary diamond instead of a dress diamond.

  In the case of using a rotary diamond, the difference between the outer peripheral surface of the rotary diamond corresponding to the tip of the dress diamond and the position reference of the dressing device, in this case, the radius of the rotary diamond, this value is input in advance and the storage unit 16 is stored. Further, the radius of the rotary diamond also varies due to wear or the like. For example, the radius is corrected again by measuring or recalculating the radius at the end of dressing, and the corrected radius value is stored in the storage unit 16. This can prevent erroneous recognition of the grindstone diameter.

  In the present embodiment, an example of an internal grinder has been shown. However, the present invention is a grinder having a structure in which a grindstone rotates around a rotation axis and an outer peripheral side surface of the grindstone serves as a grinding surface, for example, a cylindrical workpiece. The present invention can also be applied to an outer peripheral grinder that grinds the outer peripheral surface.

  The present invention is suitable for grinding a grindstone and a workpiece in a grinder equipped with a dressing device.

DESCRIPTION OF SYMBOLS 1 Internal grinding machine 2 Grinding wheel 3 Grinding wheel axis 4 Grinding wheel axis rotation mechanism 5 Grinding wheel axis feed mechanism 6 Work piece 7 Chuck device 8 Work spindle 9 Work spindle rotation mechanism 10 In-line sizing device 11 Dressing device 12 Dressing diamond 13 Grinding machine control device 14 Input Unit 15 Arithmetic processing unit 16 Storage unit 17 Drive control unit 18 Operation unit 19 Display unit (notification unit)

Claims (4)

A dressing method for dressing a grindstone held on a grindstone shaft by using a dressing device,
Until the grindstone diameter ratio, which is the ratio of the grindstone diameter of the grindstone in a new state or after trial grinding, and the grindstone diameter of the grindstone after the grinding of the workpiece and the dressing of the grindstone reaches a predetermined value Maintains the same dress interval, discontinuously shortens the dress interval when the grinding wheel diameter ratio falls below the predetermined value ,
The predetermined value is 0.92.
The ratio between the number of workpieces ground at the dress interval until the grinding wheel diameter ratio reaches 0.92 and the number of grinding workpieces at the dress interval immediately after the grinding wheel diameter ratio reaches 0.92 is 0. 6. A dressing method. A dressing method for dressing a grindstone held on a grindstone shaft by using a dressing device,
Until the grindstone diameter ratio, which is the ratio of the grindstone diameter of the grindstone in a new state or after trial grinding, and the grindstone diameter of the grindstone after the grinding of the workpiece and the dressing of the grindstone reaches a predetermined value Maintains the same dress interval, discontinuously shortens the dress interval when the grinding wheel diameter ratio falls below the predetermined value,
After the discontinuous short dress intervals, continuously shortening the dress interval in response to a decrease of the grinding wheel diameter, de-less methods. A dressing method of dressing a grindstone held on a grindstone shaft by using a dressing device,
Until the grindstone diameter ratio, which is the ratio of the grindstone diameter of the grindstone in a new state or after trial grinding, and the grindstone diameter of the grindstone after the grinding of the workpiece and the dressing of the grindstone reaches a predetermined value Maintains the same dress interval, discontinuously shortens the dress interval when the grindstone diameter ratio is less than or equal to the predetermined value,
After shortening the dressing interval discontinuously, the dressing interval is shortened continuously as the grinding wheel diameter decreases ,
The predetermined value is 0.92.
The ratio between the number of workpieces ground at the dressing interval until the grinding wheel diameter ratio reaches 0.92 and the number of grinding workpieces at the dressing interval immediately after the grinding wheel diameter ratio reaches 0.92 is 0. is 6, the de-less way. A workpiece grinding method,
Dressing the grindstone by the dressing method according to any one of claims 1 to 3,
Grinding the workpiece using the dressed grindstone, and a workpiece grinding method.

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