JP2006231420A - Automatic lathe and rear face machining method by the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform cutting of a maximum length within allowable deflection volume without lowering productivity in an automatic lathe. <P>SOLUTION: This lathe has a control means 1 for controlling radial amount d of depth of cut. The control means 1 has a storage means 1A for setting the allowable maximum deflection amount b during the cutting at a free end to be the other end of a workpiece of the Young's modulus E, specific cutting force K, feeding amount f of the workpiece fixed in a spindle axis direction and the Young's modulus E and storing the data, a first arithmetic means 1C for determining a coefficient α as α=(3πEb)/(64Kf) based on the data from the storage means 1A, a fetch means 1B for successively fetching a length L from a cantilever base point of the workpiece up to a cutting point changing during the cutting and a minimum outer diameter D, and a second arithmetic means 1D for calculating the radial amount d of depth of cut of a cutter as d=(αD<SP>4</SP>)/L<SP>3</SP>by using successively updated L and D. A tool rest for controlling the depth of cut of the cutting based on the value of the amount d of depth of cut is controlled by an X-axis. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an automatic lathe and a back surface processing method using the automatic lathe.

  In the automatic lathe, as shown in FIG. 3 (A), a bar member 11 as a workpiece is rotatably supported by a bush 12 of a main shaft, and the bar member is rotated around its longitudinal axis. Sending in the axial direction, moving the tool 13 supported by the tool post located at a fixed position near the bush with respect to the axial direction in the radial direction, and machining the workpiece that protrudes in the axial direction from the bush 12 from one end of the tip To do. Processing in a state of being supported by the main shaft is referred to as front processing, and after completion of predetermined processing, the workpiece is cut out by the cutting tool 13 at the cutting position 14 to obtain a product.

  Depending on the product, after the front machining, the workpiece 15 is gripped by the chuck 15 at one end so as to deliver the workpiece 11 to the chuck 15 positioned axially ahead of the main shaft, as shown in FIG. Then, the workpiece 11 is cut out, and additional processing may be performed by the cutter 13 from the other end, that is, the free end which is a cut-off end, while moving the chuck 15 toward the spindle (see FIG. 3B). . The additional processing of the workpiece after holding by the chuck after the front processing is referred to as back processing.

  In this way, when the back surface processing of the bar member is performed with an automatic lathe, the work piece is changed from the main shaft to the chuck, so there is no bush on the back surface processing side, and cutting is performed in a cantilever state. It becomes. Although the workpiece is cantilevered by the bush even during front face machining, in this case, as shown in FIG. 3A, machining by the blade 13 is performed at a position close to the bush 12 in the axial direction. That is, the workpiece is processed in the vicinity of the cantilever base point. On the other hand, at the time of back surface processing, as can be seen from FIG. 3B, the workpiece 11 starts to be cut by the blade 13 from the cantilevered free end. Cutting at a position far from the cantilever base point causes the workpiece to bend due to cutting resistance during cutting (see FIG. 3B). Therefore, this deflection becomes larger when the cutter is located at a position near the free end with respect to the workpiece, that is, the clearance in the radial direction of the workpiece with respect to the cutter is increased. This relief means that the amount of movement of the blade for cutting is less than the amount of movement in the radial direction and is not cut. As a result, even if an attempt is made to machine a portion having a constant diameter in the axial direction at the end of machining, as shown in FIG. 3 (C), a radius error c that expands toward the free end has a radius error c. Then, this error may exceed the allowable value.

  In order to keep such an error within an allowable limit, generally, the machining length that can be cut with a cantilever, that is, the distance from the cantilever base point of the workpiece to the machining position, that is, the cutting point, in other words, the back surface machining The length of the workpiece is different depending on the material of the workpiece. For soft materials such as copper alloys, the cutting diameter of the workpiece is 2.5 times, and for hard materials such as steel, it is 6 times. Take a close value. That is, the maximum possible length of the workpiece is shortened in order to fall within the allowable processing error limit due to the bending.

  In order to make the amount of bending less than or equal to the allowable amount, it is conceivable to always detect the amount of bending and to correct and control the cutting amount so as to regulate the amount of bending.

Conventionally, regarding machining related to the deflection within the allowable value, although not for an automatic lathe, a deflection non-contact sensor is arranged at an intermediate portion of the grinding wheel shaft as a deflection correction control in a cantilever state for an internal grinding machine, thereby Patent Document 1 discloses a control method and apparatus for measuring a deflection displacement of a shaft, calculating a maximum deflection amount at a required grindstone position using the value, and correcting the deflection based on the calculated value. ing.
JP 2003-300132 A

  Since the method according to Patent Document 1 described above can be measured in real time in the case of a workpiece or an object to be measured in which there is no shape deformation other than bending, application in a limited region is advantageous. That is, since the diameter of the shaft that supports the grindstone does not change, it is possible to estimate the amount of bending at the grinding site from the detected value by detecting the bending of the shaft by placing a sensor close to the shaft.

  However, in the case of small thread cutting by backside processing with an automatic lathe, the position of the cutter is in a fixed position in the axial direction. Furthermore, since the diameter of the workpiece changes in real time by cutting, it is not easy to measure the deflection in real time by bringing the deflection sensor close to the workpiece. As a matter of fact, even if the sensor is arranged close to the cutter, the bending of the workpiece cannot be measured. Therefore, the measurement method of Patent Document 1 cannot be applied to the back surface processing of an automatic lathe.

  In the case of the back surface processing by the automatic lathe, the workpiece is in a cantilever state, the deflection is proportional to the cube of the cutting length of the workpiece with respect to the tip load, and the cutting diameter of the workpiece is further increased. Since there is a physical condition that is inversely proportional to the fourth power, a change in the size of the workpiece due to the cutting of the workpiece makes measurement particularly difficult.

  In view of such circumstances, an object of the present invention is to provide an automatic lathe capable of keeping the bending at the time of back surface processing within an allowable value by an extremely simple means, and a back surface processing method using the automatic lathe. .

<Backside processing method>
The present invention relates to a back surface machining method for turning a workpiece while holding one end of the workpiece in a cantilevered state with a chuck during back surface machining by an automatic lathe.

In such a method, the present invention includes a first step of setting an allowable maximum deflection amount b during machining at the free end as the other end of the workpiece having a Young's modulus E, and a specific cutting resistance K and a determination in the main shaft axis direction. A second step of obtaining a coefficient α as α = (3πEb) / (64 Kf) from the feed amount f of the workpiece to be processed, the Young's modulus E, and the allowable maximum deflection amount b, and a workpiece that changes during machining The third step of sequentially taking in the length L and the minimum outer diameter D from the cantilever base point to the cutting point, and the cutting amount d of the blade in the radial direction using the successively updated L and D is d = (αD ⁴ ). / L ³ and a fourth step, and the turning is performed with this cutting depth d.

In the above method, in the second step, the cutting amount d is used instead of the workpiece feed amount f, and the coefficient β is obtained as β = (3πEb) / (64 Kd) instead of the coefficient α. The feed amount is determined as f = (βD ⁴ ) / L ^{3 in} four steps, and cutting can be performed under this feed amount f. That is, one of d and f can be determined in advance, and the other can be controlled so that the deflection is within the allowable maximum deflection amount b.

<Automatic lathe>
The automatic lathe of the present invention for carrying out the above-described method of the present invention has a control means for controlling the cutting depth d in the radial direction, and the control means is the other end of the workpiece having a Young's modulus E. Storage means for setting the allowable maximum deflection amount b during machining at the free end, the specific cutting resistance K, the feed amount f of the work piece determined in the spindle axis direction, and the Young's modulus E and storing these data A first calculation means for obtaining a coefficient α as α = (3πEb) / (64 Kf) based on the data from the storage means, a length L from the cantilever base point of the workpiece to the cutting point, which changes during processing, and A take-in means for sequentially taking in the minimum outer diameter D, and a second calculation means for calculating the cutting amount d of the blade in the radial direction as d = (αD ⁴ ) / L ³ using L and D that have been successively updated. The cutting depth is controlled based on the value of the depth d. It is characterized by controlling the tool rest in the X-axis.

  Also in the present invention, as in the case of the method invention described above, the relationship between the cutting tool feed amount f and the cutting amount d can be interchanged. That is, a cutting amount d is set in advance in place of the workpiece feed amount f preset by the storage means, a coefficient β is obtained instead of the coefficient α by the first calculating means, and a cutting amount d is calculated by the second calculating means. Instead, the same amount of machining can be performed by obtaining the feed amount f and controlling the spindle that controls cutting feed by the Z-axis based on the value of the feed amount f.

<Principle of the invention>
The method and apparatus of the present invention is based on the following principle.

  The deflection is inherently related to the cutting force P, the distance L from the cantilever base point of the workpiece to the cutting point, and the diameter D of the workpiece, in which the cutting force P is the cutting force R that is the reaction force. Accompanied by.

  As is well known, the cutting resistance R is related to the cutting feed amount f and the cutting infeed amount d. Therefore, the cutting resistance R depends on the change in L under the condition that the bending is kept below a predetermined allowable value. By controlling d or f, an arbitrarily long object can be processed. The cutting feed amount f refers to the amount of movement of the workpiece in the main axis direction, that is, the Z axis, and the cutting amount d refers to the amount of movement of the blade in the radial direction, that is, the X axis.

As known in general teaching materials such as material mechanics, the workpiece b, for example, the deflection b of the bar member, is determined by the cutting force P, the distance L from the cantilever base point to the cutting point, the Young's modulus E of the workpiece, In relation to the diameter D of the workpiece,
b = (64PL ³ ) / (3πED ⁴ ) (1)
It becomes. Note that π is a circumference ratio.

  Further, the cutting force P in the equation (1) is balanced with the cutting resistance R as a reaction force at the cutting point, and the value thereof is equal. Therefore, the cutting force P in the formula (1) can be replaced with the cutting force R.

  On the other hand, the cutting resistance R is related to the cutting feed amount f and the cutting depth d. However, the machining conditions are intertwined in a complicated manner, and an approximate expression by experiment is generally known.

  However, in order to complicate the explanation of the approximate expression, the following theoretical expression (2) of the cutting resistance R that is generally used (lathe working method: published by Rigaku Corporation) is used here.

R = Kfd ………………………………………………………… (2)
In addition, K is a load per 1 mm ^{2 of the} chip cross-sectional area due to the specific cutting resistance, and is a constant that varies depending on the material of the workpiece.

Here, substituting the equation (2) into the equation (1) and obtaining the above cutting depth d,
d = (3πEbD ⁴ ) / (64 KfL ³ ) (3)
Is obtained.

Equation (3) is converted into the variable diameter D of the workpiece and the distance L from the cantilever base point to the cutting point,
Dividing into other constants and letting this constant be α, equation (3) is replaced by the following equation (4).

d = (αD ⁴ / L ³ ) …………………………………………… (4)
However, α = (3πEb) / (64 Kf)
When the value of each element of the coefficient α is determined in equation (4), the cutting depth d is calculated according to the value of L or D.

  Thus, when the value of the cutting depth d is determined, the workpiece of L or D within the allowable value range of the bending amount b at the cutting point can be cut.

  Note that the calculated value of the cutting depth d is a value of the cutting depth under cutting resistance R in a steady state where the bending amount b at the cutting point is equal to or less than an allowable value.

  The expression (4) is developed with the cutting depth d. However, if the cutting depth d is a set value, it can be developed with the cutting feed amount f in the same manner.

  Thus, according to the present invention, first, the maximum allowable deflection amount b is determined from the processing accuracy of the workpiece as a product, and the workpiece feed amount f at the time of cutting is set. Further, since the specific cutting resistance K and Young's modulus E are known from the material of the workpiece, the coefficient α (= (3πEb) / (64Kf)) is obtained from these values, and from the cantilever base point of the workpiece being processed. By sequentially updating and taking in the distance L to the cutting point and the minimum diameter D, the cutting amount d is obtained, and by performing processing with this cutting amount d, the bending amount b at the cutting point is less than the allowable value. Thus, the accuracy of the product can be secured without reducing the processing efficiency. Further, as described above, when the relationship between the feed amount f and the cut amount d is changed and developed, the feed amount f can be controlled by presetting a constant cut amount d.

  As described above, according to the present invention, in the back surface processing, either one of the feed amount of the workpiece and the cutting depth of the blade at the time of cutting, the constant determined by the material of the workpiece, and the dimension during the processing, the bending type Based on the above, the other of the feed amount and the cut amount is determined, and by cutting based on the value, the bending of the workpiece at the cutting point is suppressed to an allowable value or less without reducing the machining efficiency. As a result, a highly efficient and highly accurate product is obtained. In other words, according to the present invention, if the processing conditions are the same as the conventional one, it is possible to process a workpiece longer than the conventional one, and it is possible to process a conventional one that has been cut in multiple steps in one step, Processing time can be shortened. Productivity also increases in this respect.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  In FIG. 1, reference numeral 1 denotes a control unit of an automatic lathe, but this control unit 1 shows only means relating to back surface machining, and other control means are omitted. The control unit 1 is connected to a chuck support plate 2 and a tool post 3 for machining the back surface of an automatic lathe. The chuck support plate 2 is located in the axial direction of the headstock (not shown), and the work piece which has been subjected to the front face machining by the tool of the tool post is gripped on the tip side while the work piece is gripped on the tip side. It is possible to move towards. The tool post 3 is immovable in the axial direction in the vicinity of the headstock, and only the tool supported by the tool post 3 can move in the radial direction.

Since the workpiece is machined according to the machining program, the chuck support plate 2 having a chuck for gripping the workpiece is also moved in the axial direction according to the program, and the tool rest 3 is programmed according to the radial direction of the tool. Moving. Therefore, from the amount of movement of the chuck support plate 2 in the axial direction, the distance L from the cantilever base point (position held by the chuck) of the workpiece to the blade, and the amount of movement of the blade in the radial direction relative to the tool post 3 are measured. The diameter D of the workpiece can be calculated respectively.

  The control unit 1 includes a storage unit 1A, a capture unit 1B, a first calculation unit 1C, and a second calculation unit 1D.

  In the storage unit 1A, the maximum allowable deflection amount b at the cutting point (the position at which the cutting edge of the blade cuts) of the workpiece determined by the final processing accuracy by the setting input from the outside, and the blade determined from the productivity. The feed amount f in the axial direction of the workpiece, the specific cutting resistance K determined from the material of the workpiece, and the Young's modulus E can be inputted and stored as constants.

  On the other hand, the take-in part 1B sequentially takes in and updates the distance L from the surface of the chuck support board 2 and the diameter D of the work piece from the tool post 3 as values that change every moment as the cutting progresses. It is like that.

  The storage unit 1A is connected to the first calculation unit 1C to transmit the constants b, f, K, and E. In the first calculation unit 1C, the coefficient α is calculated based on the following equation based on these constants.

α = (3πEb) / (64Kf)
The first calculation unit 1C and the capture unit 1B are connected to the second calculation unit 1D. The second calculation unit 1D receives the updated new L and D values from the take-in unit 1B and the coefficient α from the first calculation unit 1C, and calculates the cutting amount d of the blade based on the following equation. .

d = (αD ⁴ ) / L ³
The second calculation unit 1D is connected to the tool post 3 and cuts and moves the tool by the cutting amount d calculated by the second calculation unit 1D.

  The cutting process in the apparatus of this embodiment will be further described in detail with reference to the flowchart of FIG.

  (1) First, when the material (material) of the workpiece is determined, the Young's modulus E, the maximum allowable deflection b determined by the allowable value of the machining accuracy, the specific cutting resistance K of the workpiece, the cutting feed amount f Each constant is obtained.

  (2) As shown in FIG. 2, these constants are input to the storage unit 1A in the input step (step S31) of the control device, and then the coefficient α is calculated (step S32) in the first calculation unit 1C according to the program. The

  (3) Next, when the workpiece diameter D and the value of the distance L from the cantilever base point to the cutting point are sequentially updated and taken into the take-in portion 1B (step S33), the values are as follows. The parameter is taken into the second computing unit 1D together with the coefficient α from the first computing unit 1C, thereby calculating the cutting depth d (step S34). This calculation (step S34) is sequentially calculated as a correction value according to the value of L or D.

  (4) The calculation result for d determines the cutting amount d of the blade, and according to this, the blade moves in the radial direction and performs cutting.

  Various calculation and control processes in the present invention are programmed, recorded on a recording medium, further added to the control device, and a basic machining control program for controlling the control device in the cutting direction, that is, a blade Is incorporated in the basic machining control program as a subprogram in the flow of the machining control program set near the cantilever base point (step 35). The basic machining control program in which the subprogram is incorporated outputs cutting amount control information (step 36) to the cutting drive control means at the cutting start point.

  In the present invention, when the shape of the workpiece in the back surface processing is complicated and the diameter changes in the axial direction, the diameter D to be taken into the take-in portion may be input as the outer diameter value of the minimum diameter portion. By doing so, the amount of bending is predicted as a larger amount than the actual amount, so the amount of cutting is suppressed and the actual amount of bending does not exceed the allowable amount of bending.

In the present invention, it is also possible to control the feed amount f by presetting the cutting amount d as a constant value. In this case, in FIG. 1, the cutting amount d is input to the storage unit 1A instead of the feed amount f, and the first calculation unit 1C calculates the coefficient β instead of the coefficient α as β = (3πEb) / (64Kd). In the second calculation unit 1D, the feed amount f is calculated as f = (βD ⁴ ) / L ³ instead of the cutting amount d. Based on this feed amount f, the movement of the chuck support plate 2 is controlled.

It is a schematic block diagram of the apparatus of one Embodiment of this invention. It is a flowchart which shows the process in the apparatus of FIG. The state of the process by the conventional method is shown, (A) shows the time when the front surface is processed, (B) shows the time when the back surface is processed, and (C) shows the time when the back surface processing ends.

Explanation of symbols

1 Control means (control unit)
1A storage means (storage unit)
1B Intake means (intake section)
1C 1st calculating means (1st calculating part)
1D second computing means (second computing unit)
b Deflection amount d Cutting amount f Feed amount D Diameter E Young's modulus K Specific cutting resistance L Distance from cantilever base point to cutting point α coefficient β coefficient

Claims (4)

In a method of turning a workpiece while holding one end of the workpiece in a cantilevered state with a chuck during back surface machining by an automatic lathe, during machining at the free end that is the other end of the workpiece having a Young's modulus E The coefficient α is determined from the first step of setting the allowable maximum deflection amount b in the above, the specific cutting resistance K, the feed amount f of the workpiece defined in the spindle axis direction, the Young's modulus E, and the allowable maximum deflection amount b. a second step for obtaining α = (3πEb) / (64 Kf), a third step for sequentially taking in the length L and the minimum outer diameter D from the cantilever base point to the cutting point of the workpiece, which changes during machining, A fourth step of using the updated L and D to obtain the cutting depth d of the blade in the radial direction as d = (αD ⁴ ) / L ³ , and turning with the cutting depth d A back surface processing method in an automatic lathe that is characterized. In a method of turning a workpiece while holding one end of the workpiece in a cantilevered state with a chuck during back surface machining by an automatic lathe, during machining at the free end that is the other end of the workpiece having a Young's modulus E In the first step of setting the allowable maximum bending amount b in the above, the coefficient β is calculated from the specific cutting resistance K, the cutting amount d of the blade defined in the radial direction, the Young's modulus E, and the allowable maximum bending amount b = ( The second step obtained as 3πEb) / (64Kd), the third step for sequentially taking in the length L and the minimum outer diameter D from the cantilever base point to the cutting point of the workpiece, which changes during the machining, and was updated sequentially. And a fourth step of obtaining the workpiece feed amount f in the axial direction as f = (βD ⁴ ) / L ³ using L and D, and turning with this feed amount f. The back surface processing method in the automatic lathe. In an automatic lathe for turning a workpiece by gripping one end of the workpiece in a cantilevered state with a chuck when processing the back surface of the workpiece, the automatic lathe has a control means for controlling a cutting amount d in the radial direction, The control means includes an allowable maximum deflection amount b during processing at the free end as the other end of the workpiece having a Young's modulus E, a specific cutting resistance K, a predetermined workpiece feed amount f in the main axis direction, A storage means for setting the Young's modulus E and storing these data; a first calculation means for determining the coefficient α as α = (3πEb) / (64 Kf) based on the data from the storage means; Using the taking-in means for successively taking in the length L and the minimum outer diameter D from the cantilever base point to the cutting point of the work piece, and the successively updated L and D, the cutting amount d of the blade in the radial direction is set as d = (αD ⁴⁾ a second calculating means for calculating as a / ^{L 3} Automatic lathe with, and controlling the tool rest which controls the incision of the cutting based on the value of the depth of cut d in the X-axis. In an automatic lathe for turning a workpiece by holding one end of the workpiece in a cantilevered state with a chuck during backside processing of the workpiece, the automatic lathe has a control means for controlling the feed amount f in the axial direction, The control means includes an allowable maximum deflection amount b during processing at the free end as the other end of the workpiece having a Young's modulus E, a specific cutting resistance K, a predetermined cutting depth d in the radial direction, and the Young's modulus E. Storage means for storing these data, first calculation means for obtaining the coefficient β as β = (3πEb) / (64 Kd) based on the data from the storage means, and a workpiece that changes during machining Using the take-in means for sequentially taking in the length L and the minimum outer diameter D from the cantilever base point to the cutting point, and the L and D that are successively updated, the feed amount f of the workpiece in the axial direction is set to f = (βD ⁴ ) / L ³ and a second calculating means for calculating as this Automatic lathe, characterized in that to control the spindle in Z-axis which controls based feed cutting the value of Ri amount f.

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