JP2013059824A - Working device, and method for designing structural specification of working machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a design guideline for suppressing regenerative chatter vibrations in a working machine by clarifying the cause of generating the regenerative chatter vibrations.SOLUTION: A working device includes: a slide shaft 50 having a cutting tool 1 on its fore end; a hydrostatic oil bearing device 52 for supporting a part in a vicinity of the fore end of the slide shaft; a driving device 53 connected to a rear end of the slide shaft to drive a slide of the slide shaft; a slide bearing device 58 which is provided between the hydrostatic oil bearing device and the driving device to support the slide shaft in a slidable manner and to simulate the friction of a feed mechanism; a first spring means 63 which is provided between the hydrostatic oil bearing device and the slide bearing device to simulate the displacement in the axial direction of a tool part, and to change the spring constant; a second spring means 64 which is provided between the slide bearing device and the driving device to simulate the displacement in the axial direction of a power transmission part of the driving device and to change the spring constant; a friction force adjusting means 59 capable of adjusting the friction force of the slide shaft by applying the bearing preload P to the slide bearing device; a preload measuring means 62 for measuring the bearing preload by the friction force adjusting means; and a tool displacement measuring means 66 for measuring the displacement in the axial direction of the cutting tool.

Description

  The present invention clarifies the cause of vibration of a processing machine such as a cutting machine, particularly regenerative chatter vibration, and provides a design guideline for stabilizing regenerative chatter vibration of the processing machine and the structural specifications of the processing machine. It relates to the design method.

  The main required performance when developing a processing machine includes processing accuracy and processing capability, which greatly affect the quality and cost of the product. Therefore, quantitatively defining the structural specifications of the processing machine that satisfies the required performance is very important in designing and developing the processing machine. So far, various models have been devised for the positioning accuracy of tools and workpieces related to machining accuracy, and many studies have been conducted on the influence of structural specifications on positioning accuracy.

  On the other hand, regenerative chatter vibration is the main factor that affects the machining performance of the structural specifications, and the occurrence of regenerative chatter vibration not only greatly reduces the quality of the product, but also may damage the tool / working machine body. is there. Therefore, it is important that the processing machine main body has a structural specification capable of suppressing regenerative chatter vibration.

  Conventionally, as a countermeasure against regenerative chatter vibration, it has been common to change cutting conditions, tools, cutting oil, etc., but such countermeasures are stable due to repeated trial and error. It may take time to obtain the state, and processing may not be possible with this measure.

  Therefore, until now, based on the characteristics of existing processing machines, research on predicting regenerative chatter vibration and suppressing the predicted regenerative chatter vibration, or structural specifications using a relatively simple model Studies on the effects on vibration have been made.

  However, as a measure to suppress regenerative chatter vibration when developing a new processing machine, the main focus is simply on maximizing rigidity, and quantitatively predicting the occurrence of regenerative chatter vibration and utilizing it in the design of processing machines. There was no technology that could do it.

  As the vibration prediction method of the slicing device, in dynamic strain measurement, the dynamic strain of the milling device due to test machining of the workpiece is measured, and in the regenerative chatter vibration prediction system, machining conditions and measurement data in the test machining are input. Calculate the dynamic compliance of the milling machine, determine the milling machine conditions, enter the machining conditions and milling machine conditions in the actual machining, calculate the machining distortion, and regenerate in machining by the displacement of the machining distortion There is one that determines the influence of chatter vibration (see Patent Document 1).

  Further, it is a cutting test machine for obtaining a machining condition in which the surface roughness of the workpiece is reduced, and is a spindle that is rotatably supported on the headstock and rotates while holding the workpiece or tool, and the surface roughness of the workpiece. There is provided a surface roughness detecting means for detecting the cutting force, a cutting resistance detecting means for detecting a cutting resistance applied to the tool at the time of cutting, and a temperature detecting means for detecting the temperature of the tool at the time of cutting ( Patent Document 2).

JP 2006-102927 A JP 2006-102864 A

  However, the ones described in Patent Documents 1 and 2 are all related to a technique for increasing machining accuracy, and are used in the design stage of a processing machine by quantitatively predicting the occurrence of regenerative chatter vibration. It is not possible to provide a structural specification that can.

  The present invention has been made in view of the above-described conventional problems, and has clarified the cause of occurrence of regenerative chatter vibration, and can provide a design guideline for stabilizing regenerative chatter vibration of a processing machine and processing. The present invention relates to a structural specification design method for machines.

  The present invention provides a slide shaft having a cutting tool at the tip, an hydrostatic bearing device that supports the vicinity of the tip of the slide slidably, and a slide shaft connected to the rear end of the slide shaft. A driving device for driving; a sliding bearing device provided between the hydrostatic bearing device and the driving device for slidably supporting the slide shaft to simulate friction of a feed mechanism; and the hydrostatic bearing A first spring means which is provided on a slide shaft between a sliding device and the sliding bearing device and which can change a spring constant by simulating an axial displacement of a tool portion; and between the sliding bearing device and the driving device. Second spring means provided on the slide shaft and capable of changing the spring constant by simulating the axial displacement of the power transmission portion of the drive device, and applying a bearing preload to the slide bearing device to increase the frictional force of the slide shaft Adjustable friction force adjusting means; and A preload measuring means for measuring a bearing preload by frictional force adjusting unit, in which according to the machining apparatus, characterized in that and a tool displacement measuring means for measuring the axial displacement of the cutting tool.

  In the processing apparatus, it is preferable that the first and second spring means include a plurality of leaf springs having different thicknesses so as to be replaceable.

  In the processing apparatus, it is preferable that the frictional force adjusting means is a pressing device that applies a bearing preload to a slide shaft supported by the slide bearing device via a reduction block.

  Moreover, in the said processing apparatus, it is preferable that the said tool displacement measuring means is a laser displacement meter which measures the axial direction displacement of a cutting tool.

  Moreover, in the said processing apparatus, it is preferable that the said drive device was equipped with the cutting dynamometer.

  The present invention is a structural specification design method of a processing machine using the processing device, wherein the frictional force of the slide shaft is stepped by changing a bearing preload applied to the sliding bearing device by the frictional force adjusting means. And the operation of adjusting the spring constant stepwise by exchanging the springs of the first and second spring means, and cutting with a cutting tool for each adjustment of each operation to regenerate chatter. The operation for obtaining the vibration generation limit is performed by changing the cutting width of the cutting tool, and the chatter vibration is determined from the generation limit of chatter vibration every time the cutting width of the cutting tool is changed and each operation is adjusted. A structural specification design of a processing machine characterized in that a stable region is obtained, and a suitable frictional force of the sliding bearing device and a suitable spring constant of the first and second spring means are obtained based on the chatter vibration stable region. Method It relates to.

  Advantageous Effects of Invention According to the present invention, it is possible to achieve an excellent effect of clarifying the cause of occurrence of regenerative chatter vibration and providing a design guideline for stabilizing regenerative chatter vibration of a processing machine.

It is a side view which shows one Example of the processing apparatus of this invention. The example of the two-dimensional cutting machine with which this invention is applied is shown, (a) is a side view of a parting-off machine, (b) is a top view of an outer periphery turning machine. It is the schematic which shows the vibration model which modeled the cutting machine of FIG. 2 as a vibration system of 2 degrees of freedom.

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

  FIG. 2 shows an example of a two-dimensional cutting machine to which the present invention is applied, and FIG. 2 (a) shows a parting-off machine for parting off a rotating workpiece W with a cutting tool 1. FIG. FIG. 2B shows an outer peripheral turning machine that cuts the outer periphery of the rotating workpiece W with the cutting tool 1. In the processing machine shown in FIGS. 2A and 2B, a tool portion 3 including a cutting tool 1 and a tool holder 2 is fixed to a slide table 4. The slide table 4 constitutes a feed mechanism 7 that is fed and moved along the support frame 6 by the rotation of the feed screw 5. The feed screw 5 is connected to a motor 12 via a drive shaft 8, a support bearing 9 that supports the drive shaft 8, a coupling 10 and the like.

  In a processing machine that performs two-dimensional cutting as shown in FIG. 2, the main component force F <b> 2 in the direction in which the rotation of the workpiece W is stopped and the cutting direction are applied to the cutting point of the cutting edge of the cutting tool 1 as the cutting force. A back force F1 is generated.

  FIG. 3 is a schematic diagram of a vibration model in which the two-dimensional cutting machine of FIG. 2 is modeled as a two-degree-of-freedom vibration system. In the vibration model of FIG. Paying attention to chatter vibration, regenerative chatter vibration generally tends to occur in the direction of changing the cutting thickness (in the feed direction A in FIG. 2), so only the vibration in the cutting direction (feed direction A) by the cutting tool 1 is considered. did. In addition, regarding the cutting force, only the back component force F1 facing the feed direction A was considered, and other components having a small influence were excluded.

In the vibration model of FIG. 3, the tool portion 3 including the cutting tool 1 and the tool holder 2 that first receives the back component force F1 in FIG. 2 is regarded as a first mass m _B, and the tool portion 3 is axially It was regarded as the first spring element K _B resulting in displacement. It said first mass m _B and the first spring element K _B represents the specification of the tool unit.

The slide table 4 in FIG. 2 is regarded as the second mass m _S, and furthermore, friction generated between the feed screw 5 and the slide table 4 when the slide table 4 is moved in the feed direction A by the feed screw 5. Since the force f _f exerts a damping effect on the back component force F 1, the friction damping element V including the second mass m _S and the support frame U is set corresponding to the feed mechanism 7. The second mass m _S , the support frame U, and the friction damping element V represent the specifications of the feed mechanism.

Furthermore, the drive shaft 8 in FIG. 2, the power transmission unit 11 composed of a supporting bearing 9 and the coupling 10 is regarded as the second spring element K _S resulting in axial displacement, the back component force F1 of the second It was to transmit to the motor 12 in FIG. 2 through the spring element K _S. The second spring element K _S represents the specification of the power transmission unit.

In the vibration model of FIG. 3, the frictional force can be adjusted by applying a bearing preload P to the friction damping element V, and the first spring element K _B and the second spring element K _S can be adjusted. By making each spring constant adjustable, it was possible to meet the specifications of various processing machines as shown in FIG. In FIG. 3, C _B and C _S represent structural damping of the first and second spring elements K _B and K _S , which are excluded because they are very small compared to the damping of the friction damping element V. Can do. m _N is the mass of the support frame U, K _N is the spring constant of the support frame U, and _XX is the feed force.

  FIG. 1 shows an embodiment of the processing apparatus of the present invention manufactured based on the vibration model of FIG. In FIG. 1, reference numeral 50 denotes a slide shaft provided with a cutting tool 1 at the tip, and the vicinity of the tip of the slide shaft 50 is slidably supported by a hydrostatic bearing device 52 provided with a hydrostatic bearing 51. . The hydrostatic bearing 51 of the hydrostatic bearing device 52 has a very small change in the friction force in the direction of the back component force F1 even if the back component force F1 is loaded, and the value of the friction force itself is also very small. Only the back component force F1 can be transmitted to the rear vibration system.

  A drive device 53 that drives the slide of the slide shaft 50 is connected to the rear end of the slide shaft 50. The drive device 53 is configured to move the slide shaft 50 in the feed direction A via the feed device 55 by the rotational force of the servo motor 54. The main shaft of the servo motor 54 is supported by a large double-row tapered roller bearing to ensure sufficient rigidity and axial accuracy, and the servo motor 54 is used to achieve a high-precision rotational speed. . The driving device is provided with a cutting dynamometer 56 for measuring cutting power.

  A support frame 57 is provided between the hydrostatic bearing device 52 and the drive device 53 to support the slide shaft 50 so that the slide shaft 50 is slidable (the friction of the feed mechanism 7 in FIG. 3). A sliding bearing device 58 is provided which simulates the damping element V). For the sliding portion between the support frame 57 and the slide shaft 50 in the slide bearing device 58, a combination of fluorine resin (Turkite B [registered trademark] manufactured by Captain Industry Co., Ltd.) used as a guide part of a processing machine and S45C may be used. it can. The sliding bearing device 58 is provided with a friction force adjusting means 59 that applies a bearing preload P to the slide shaft 50 so that the friction force of the slide shaft 50 can be adjusted. As the frictional force adjusting means 59, a pressing device 61 that applies a bearing preload P to the slide shaft 50 supported by the sliding bearing device 58 via the reduction block 60 can be used. The reduction block 60 is provided with preload measuring means 62 for measuring a bearing preload P applied to the slide shaft 50 by the friction force adjusting means 59. As the preload measuring means 62, a load cell or the like can be used.

On the slide shaft 50 between the hydrostatic bearing device 52 and the slide bearing device 58, a spring simulating the axial displacement of the tool portion 3 in FIG. 2 (first spring element K _{B in} FIG. 3). A first spring means 63 whose constant is adjustable is provided. Further, the slide shaft 50 between the sliding bearing device 58 and the driving device 53 has a spring that simulates the axial displacement (second spring element K _{S in} FIG. 3) of the power transmission unit 11 in FIG. A second spring means 64 having an adjustable constant is provided. The first and second spring means 63 and 64 are configured such that a plurality of flange-like plate springs 65 having different thicknesses can be exchanged and mounted.

  The hydrostatic bearing device 52 is provided with tool displacement measuring means 66 for measuring the axial displacement of the cutting tool 1. The tool displacement measuring means 66 is shown as having a laser displacement meter 68 for measuring the axial displacement of the cutting tool 1. Moreover, you may provide the accelerometer 67 which measures the cutting acceleration of the workpiece | work W by the cutting tool 1 as needed.

  Next, the operation of the embodiment of FIG. 1 will be described.

  When the slide shaft 50 is slid in the feed direction A by the servo motor 54 of the drive device 53 via the feed device 55, the cutting tool 1 provided at the tip of the slide shaft 50 is pressed against the rotating workpiece W to cut the workpiece W. I do. The back component force F1 of the cutting force at this time is transmitted to the driving device 53 via the first spring means 63, the plain bearing device 58, and the second spring means 64.

  Here, the first spring means 63 simulating the tool part 3 of FIG. 2 can adjust the spring constant by exchanging the leaf spring 65, and the first spring means 63 simulating the power transmission part 11 of FIG. The spring means 64 of No. 2 can adjust the spring constant by exchanging the leaf spring 65, and the sliding bearing device 58 simulating the feed mechanism 7 of FIG. The frictional force of the slide shaft 50 can be adjusted by changing the bearing preload P applied to.

  The relationship between the back component force F1 and the displacement of the first spring means 63 when the back component force F1 is applied to the slide shaft 50, and the relationship between the back component force F1 and the displacement of the second spring means 64; In the sliding bearing device 58, the frictional force when the bearing preload P applied to the slide shaft 50 is adjusted by the frictional force adjusting means 59 to change the sliding speed was identified. As a result, the first spring means 63 favorably represents the axial displacement of the tool portion 3, and the second spring means 64 favorably represents the axial displacement of the power transmission portion 11. It has been found that the adjustment of the bearing preload P by the frictional force adjusting means 59 represents the frictional force of the feed mechanism 7 well.

  As described above, the operation of adjusting the spring constant of the first spring means 63, the operation of adjusting the spring constant of the second spring means 64, and the friction force adjusting means 59 adjust the friction force of the sliding bearing device 58. A test was conducted to determine the limit of occurrence of regenerative chatter vibration each time the operation was combined. Further, the cutting tool 1 was replaced with one having a different cutting width, and a test was performed to determine the generation limit of regenerative chatter vibration when the cutting width was changed. Then, the cutting width of the cutting tool is changed, and further, each regenerative chatter vibration obtained by a test carried out by adjusting the first spring means 63, the second spring means 64, and the slide bearing device 58 is performed. From the generation limit of each, the regenerative chatter vibration stable region in each was obtained.

  The prediction of regenerative chatter vibration based on the processing apparatus of FIG. 1 manufactured based on the vibration model of FIG. 3 is in good agreement with the result of testing with an actual processing machine, and thus the replay obtained in the above test is the same. It has been found that the chatter vibration stability data can be effectively applied to the regenerative chatter vibration suppression of the processing machine in the development stage.

  In other words, conventionally, as a method for suppressing regenerative chatter vibration, the focus has been on increasing the rigidity of the apparatus, but this guideline is not always correct, and the rigidity and damping of each part of the apparatus should be optimized as in the present invention. Thus, it was found that more reliable chatter vibration stability can be obtained.

  Therefore, as described above, the regenerative chatter vibration stabilization by the combination of the suitable frictional force of the sliding bearing device 58 corresponding to the cutting width of the cutting tool and the suitable spring constants of the first and second spring means 63 and 64. Since a region is required, the feed mechanism 7 based on a suitable frictional force of the receiving device 58 is designed, and a tool portion comprising the cutting tool 1 and the tool holder 2 based on a suitable spring constant of the first spring means 63. 3, and the rigidity strength of the power transmission unit 11 including the drive shaft 8, the support bearing 9, and the coupling 10 can be designed based on a suitable spring constant of the second spring means 64.

  The present invention is not limited to the above-described embodiments. For example, the tool unit and the power transmission unit may be further divided and simulated by a plurality of spring means, or the processing apparatus of the present invention. Of course, it is possible to obtain a regenerative chatter vibration stable region in various processing machines, and various modifications can be made without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Cutting tool 3 Tool part 7 Feed mechanism 11 Power transmission part 50 Slide shaft 51 Oil hydrostatic bearing 52 Oil hydrostatic bearing apparatus 53 Drive apparatus 56 Cutting dynamometer 58 Sliding bearing apparatus 59 Friction force adjustment means 60 Reduction block 61 Pressing apparatus 62 Preload measuring means 63 First spring means 64 Second spring means 65 Leaf spring 66 Tool displacement measuring means 68 Laser displacement meter

Claims (6)

  A slide shaft having a cutting tool at the tip, an hydrostatic bearing device that supports the vicinity of the tip of the slide slidably, and a drive device that is connected to the rear end of the slide shaft and drives the slide of the slide shaft A sliding bearing device that is provided between the hydrostatic bearing device and the driving device and supports the slide shaft so as to be slidable, and simulates friction of a feed mechanism, and the hydrostatic bearing device and the sliding device A first spring means provided on a slide shaft between the bearing device and capable of changing a spring constant by simulating an axial displacement of the tool portion, and provided on a slide shaft between the slide bearing device and the drive device. Second spring means capable of changing the spring constant by simulating the axial displacement of the power transmission portion of the drive device, and friction capable of adjusting the friction force of the slide shaft by applying a bearing preload to the slide bearing device Force adjusting means and friction force adjusting Processing apparatus for a preload measuring means for measuring a bearing preload by stage, the tool displacement measuring means for measuring the axial displacement of the cutting tool, comprising the.   The processing apparatus according to claim 1, wherein the first and second spring means include a plurality of leaf springs having different thicknesses so as to be exchangeable.   The processing apparatus according to claim 1, wherein the frictional force adjusting means is a pressing device that applies a bearing preload to a slide shaft supported by the sliding bearing device via a reduction block.   The processing apparatus according to claim 1, wherein the tool displacement measuring unit is a laser displacement meter that measures an axial displacement of a cutting tool.   The processing apparatus according to claim 1, wherein the driving device includes a cutting dynamometer.   A structural specification design method for a processing machine using the processing device according to any one of claims 1 to 5, wherein the frictional force adjusting means changes a bearing preload applied to the sliding bearing device. The operation of adjusting the frictional force of the slide shaft in stages and the operation of adjusting the spring constant in stages by exchanging the springs of the first and second spring means are combined and cutting is performed for each adjustment of each operation. Chatter vibration is performed every time the cutting width of the cutting tool is changed, the cutting width of the cutting tool is changed, and each operation is adjusted. Each chatter vibration stable region is obtained from the generation limit of the chatter, and based on the chatter vibration stable region, a suitable friction force of the sliding bearing device and a suitable spring constant of the first and second spring means are obtained. Processing machine Structure specification design method.

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