band saw

Abstract

To provide a band saw that allows efficient automatic adjustment of operation speed without experience and is capable of automatically avoiding resonance without pre-measuring the resonance frequency.SOLUTION: A band saw 10 includes: an endless saw blade 24; a pair of wheels 26 on which the saw blade 24 is wound; cutting means 20 having a rotating motor 28 that is connected to one of the wheels 26 and driven to rotate; and feed means 30 having a feed motor 32 which moves the cutting means 20 in a cutting direction. The band saw includes: a vibration measurement sensor 40 for detecting vibration that is generated during cutting; a frequency analysis unit 80 for analyzing a measurement of the vibration measurement sensor 40 per frequency and indicating a peak intensity; a determination unit 60 for determining whether or not the peak intensity of the frequency analysis unit 80 is equal to or greater than a set peak value and whether it agrees with an estimated cutting frequency of a saw blade pitch; and a control unit 70 for controlling at least one of a rotating speed of the rotating motor 28 and a rotating speed of the feed motor 32 based on the determination of the determination unit 60.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a band saw that cuts large structures using an endless saw blade. [Background technology]

[0002] Band saws with endless saw blades are used in the demolition of large structures such as large-diameter pipes. Since the wrong operating speed can cause problems such as chipping of the saw blade, band saws are difficult to adjust, and are therefore operated by experienced, skilled operators. Due to the aging and declining number of skilled operators, and the time it takes to learn and develop optimal operating speeds, there are currently technologies available that automatically adjust various operating speeds.

[0003] The vibrations generated during cutting with a band saw affect the wear and lifespan of the saw blade, so there is a need for automatic speed adjustment technology to minimize vibrations. The inventors of this application measured the vibrations of the frame during cutting and confirmed steady vibrations under certain conditions. Analysis of this steady vibration revealed that the vibrations increased at frequencies that tend to vibrate the frame, in other words, were due to frame resonance. A conventional technology for avoiding resonance of a saw blade is the portable band saw described in Patent Document 1. This technology measures in advance the frequency at which a known resonance occurs (resonance frequency), and sets the rotation speed of the drive motor of the saw blade so that it deviates from this resonant frequency by 20%.

[0004] However, in the case of a band saw frame intended to cut large structures, the resonant frequency varies depending on the height of the saw blade drive motor (saw blade elevation position), which changes in conjunction with the elevation of the saw blade, the method of fixing the frame to the floor, and the rigidity of the floor. To obtain the resonant frequency in advance, as in Patent Document 1, requires time-consuming measurements, such as changing the saw blade elevation position multiple times each time the frame is installed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-1126 Summary of the Invention [Problem to be solved by the invention]

[0006] In view of the problems of the prior art described above, the problem to be solved by the present invention is to provide a band saw that can automatically adjust the operating speed efficiently without the need for experienced technicians, and can automatically avoid resonance without the need to measure the resonance frequency in advance. [Means for solving the problem]

[0007] As a first means for solving the above-mentioned problems, the present invention provides a cutting means having an endless saw blade, a pair of wheels around which the saw blade is hung, a rotation motor connected to one of the wheels for rotating the same, and a cutting apparatus for cutting the cutting means. Up and down In a band saw equipped with a feed means having a feed motor that moves in the cutting direction, A vibration measurement sensor that detects vibrations generated during cutting; a frequency analysis unit that resolves the measurement value of the vibration measurement sensor into frequency components and expresses peak intensities; a determination unit that determines whether the peak intensity of the frequency analysis unit is equal to or greater than a peak setting value and whether it matches an estimated cutting frequency of the saw blade pitch; The object of the present invention is to provide a band saw characterized by comprising a control unit that controls at least one of the rotation speed of the rotating motor and the rotation speed of the feed motor based on the determination of the determination unit. According to the first means, resonance can be automatically avoided without measuring the resonance frequency in advance.

[0008] As a second means for solving the above-mentioned problems, the present invention provides a saw blade vertical position measuring device in the first means, which includes: a saw blade horizontal position measuring sensor for detecting the horizontal position of the saw blade; the determination unit compares the measurement value of the vibration measurement sensor with a vibration set value, the measurement value of the saw blade vertical position measurement sensor with a saw blade height change set value, and the measurement value of the saw blade horizontal position measurement sensor with a saw blade position set value; The control unit controls at least one of the rotation speed of the rotating motor and the rotation speed of the feed motor based on the determination of the determination unit. According to the second means, it is possible to perform control so that the peripheral speed or feed speed becomes optimal based on physical changes such as frame vibration and positional deviation of the saw blade.

[0009] As a third means for solving the above problem, the present invention provides a band saw characterized in that, in the second means, the saw blade vertical position measurement sensor is a laser sensor attached to the lifting frame of the cutting means to detect the height position of the saw blade. According to the third means, it is possible to determine from the detected value of the height position of the saw blade that the saw blade is slipping away in the direction opposite to the feed direction (hereinafter referred to as cutting delay).

[0010] As a fourth means for solving the above problem, the present invention provides a band saw 10 characterized in that, in the second means, the saw blade horizontal position measurement sensor is a laser sensor attached to the lifting frame of the cutting means to detect the horizontal position of the saw blade. According to the fourth means, the occurrence of twisting or bending of the saw blade can be detected from the detected value of the horizontal position of the saw blade.

[0011] As a fifth means for solving the above problem, the present invention provides a band saw characterized in that, in the first or second means, the vibration measuring sensor is provided at the connection point between the pillar of the frame body to which the feed means is attached and the upper frame. According to the fifth means, when vibration of the saw blade occurs, it can be easily detected on the frame body. [Effects of the Invention]

[0012] According to the present invention, resonance due to the cutting frequency can be automatically avoided without measuring the resonance frequency in advance. Furthermore, it is possible to perform control so that the peripheral speed or feed speed is optimized based on physical changes such as frame vibration and positional deviation of the saw blade. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic diagram of the configuration of a band saw according to a first embodiment. FIG. [Figure 2] FIG. 1 is a process flow diagram using the band saw of Example 1. [Figure 3] FIG. 10 is a schematic diagram of the configuration of a band saw according to a second embodiment. [Figure 4] FIG. 10 is an explanatory diagram of a saw blade vertical position measurement sensor that detects the height position. [Figure 5] FIG. 4 is an explanatory diagram of a saw blade horizontal position measuring sensor that detects the horizontal position. [Figure 6] FIG. 10 is a process flow diagram using the band saw of Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a band saw according to the present invention will be described in detail below with reference to the drawings.

[0015] Example 1 [Band Saw 10] FIG. 1 is a schematic diagram showing the configuration of a band saw according to the present invention. The band saw 10 of the present invention comprises a frame body 12, an endless saw blade 24, a pair of wheels 26 around which the saw blade 24 rotates, cutting means 20 having a rotation motor 28 connected to one of the wheels 26 to rotate it, feeding means 30 having a feed motor 32 that moves the cutting means 20 in the cutting direction, a vibration measuring sensor 40 that detects vibrations acting on the saw blade 24 during cutting, a frequency analysis unit 80 that resolves the measurements of the vibration measuring sensor 40 by frequency and expresses the peak intensity, a judgment unit 60 that judges whether the peak intensity of the frequency analysis unit 80 is equal to or greater than a peak setting value and whether it matches the estimated cutting frequency of the saw blade pitch, and a control unit 70 that controls at least one of the rotation speed of the rotation motor 28 and the feed motor 32 based on the judgment of the judgment unit 60.

[0016] The frame body 12 has upper and lower frames 13, 14 that are rectangular in plan view, and four pillars 15 located at the four corners between the upper and lower frames 13, 14, forming an overall rectangular parallelepiped shape. The frame body 12 is provided with a cutting means 20, a feeding means 30, etc.

[0017] The cutting means 20 has a saw blade 24, a pair of wheels 26, a rotation motor 28, and a lifting frame 29 on which these are arranged. The lifting frame 29 is a frame that moves up and down along the pillars 15 of the frame main body 12, and can lower the saw blade 24 to cut the material to be cut. A pair of lifting frames 29 are provided on both ends of the frame main body 12 in the longitudinal direction. The pair of lifting frames 29 are fitted with sliders that engage with guide rails arranged on the pillars 15.

[0018] The feed means 30 has a ball screw 33, a lifting slider, and a feed motor 32, and moves the lifting frame 29 up and down along the pillars 15. The ball screw 33 is erected along the pillars 15, outside the pillars 15 of the frame body 12. The lifting slider arranged on the lifting frame 29 engages with the ball screw 33 and moves up and down along the longitudinal direction of the ball screw 33 in accordance with the rotation of the ball screw 33. The feed motor 32 is a drive source that rotates the ball screw 33. Such a feed means 30 is arranged on each frame of the pair of lifting frames 29, and by synchronously controlling the feed motors 32, the saw blade 24 on the lifting frame 29 can be raised and lowered while rotating in a horizontal plane.

[0019] The vibration measuring sensor 40 is an acceleration sensor that is disposed on the main frame 12 and detects vibrations that occur during cutting. More specifically, the vibration measuring sensor 40 is attached to the intersection, i.e., the connection point, between the top end of the pillar 15 of the frame main body 12 and the upper frame 13. The measurement direction of the vibration measuring sensor 40 is the longitudinal direction of the frame main body 12. Such a vibration measuring sensor 40 can detect vibrations occurring during cutting with high sensitivity at the upper part of the frame body.

[0020] The frequency analysis unit 80 is an algorithm (processing program) that breaks down the vibration data (measured values) measured by the vibration measurement sensor into frequency components and performs a high-speed Fourier transform to express the main vibration frequencies and the intensity (strength) of those vibrations.

[0021] The determining unit 60 determines whether the peak intensity of the frequency analyzing unit 80 is equal to or greater than a peak set value and whether it matches the estimated cutting frequency of the saw blade pitch. When large steady vibrations occur in the frame during cutting, the vibrations may be due to resonance caused by periodic fluctuations in cutting resistance (hereinafter referred to as cutting frequency). Periodic fluctuations in cutting resistance are thought to occur when cutting chips leave the saw blade and when the cutting material moves in and out of the saw blade. Here, the cutting frequency is assumed to be as follows: Cutting frequency fcut[Hz]=peripheral speed CV[m / sec] / saw blade pitch p[m] Assuming that the frame resonance is caused only by the cutting frequency, the frame resonance occurs when the resonant frequency of the frame and the calculated cutting frequency fcut are almost the same.

[0022] When frame vibration was actually measured, the resonant frequency of the frame vibration was found to be almost the same as the calculated cutting frequency fcut when large steady vibrations occurred. In addition, the peak frequency fp of the frame vibration was almost the same as the resonant frequency of the frame, and the peak intensity was more than twice as high as when large steady vibrations were not occurring. Therefore, when the peak intensity of the measured frame vibration peak frequency fp is sufficiently large and the measured frame vibration peak frequency fp is approximately the same value as the calculated cutting frequency fcut, it is determined that resonance caused by periodic fluctuations in cutting resistance is occurring. Based on this theory, it is possible to determine whether resonance is occurring without measuring the frame's natural frequency (even if the frame's natural frequency is unknown).

[0023] Generally speaking, resonance occurs when an integer multiple of the cutting frequency matches the frame's resonance frequency. Therefore, it is determined that resonance occurs when the measured frame vibration peak frequency fp is N times (N is an integer greater than or equal to 1) the calculated cutting frequency fcut.

[0024] In the present invention, it is determined that frame resonance occurs when the following conditions are satisfied. (i) Vibrations with large accelerations are occurring stably. In other words, accelerations equal to or greater than a set value are detected a certain number of times or more within a predetermined period of time. (ii) When the vibration data of the frame is subjected to frequency analysis (FFT: Fast Fourier Transform), there is a frequency having a peak intensity equal to or greater than the peak setting value. (iii) fcut and fp calculated from the rotation speed and pitch of the saw blade have the following relationship: fp≒fcut×N Here, N is an integer equal to or greater than 1. Also, a saw blade may have multiple pitches (combination pitch) to suppress vibration of the blade during cutting, and in this case, each pitch must satisfy the relationship (iii). The determining unit 60 has input therein the operating conditions of the band saw 10, such as the saw blade pitch (model number), the range of use of the feed motor and the rotation motor (rotation or feed speed).

[0025] Based on the determination by the determination unit 60, the control unit 70 controls at least one of the rotation speed of the rotation motor 28 and the rotation speed of the feed motor 32. Specifically, the control unit 70 sends control signals to the inverter of the rotation motor 28 and to the servo amplifier of the feed motor 32, respectively, to control the respective speeds.

[0026] [Decision flow] The judgment flow using the band saw of the present invention configured as described above will be described below. Note that the judgment flow of this embodiment will be described below for a case where there are two types of saw blade pitch. When large steady vibrations occur, if the vibration is caused by resonance, the rotation speed can be adjusted, and if it is caused by the structure of the workpiece, the feed speed can be reduced. (Step 1) During operation of the band saw 10 of the present invention, vibrations are collected by the vibration measuring sensor 40 for a predetermined time, 30 seconds in this embodiment.

[0027] (Step 2) It is determined whether the measurement value of the vibration measuring sensor 40 exceeds the vibration set value. If the measured value does not reach the vibration setting value, return to step 1 and repeat the process from there. (Step 3) When the measured value reaches the vibration setting value, the frequency of exceeding the vibration setting value is checked. The frequency is calculated by counting how many times the vibration setting value is exceeded in a predetermined time. In this embodiment, as an example, the vibration exceeding setting value is set to 30 times that the vibration setting value is exceeded in a predetermined time (e.g., 30 seconds). If the measured value does not reach the vibration over-set value, return to step 1 and repeat from there.

[0028] (Step 4) When the vibration exceeds the set excessive vibration value, steady vibration is occurring, and therefore resonance determination 1 is performed. The frequency analysis unit 80 breaks down the measurement value of the vibration measurement sensor 40 into frequency components and represents the peak intensity of each frequency. Resonance determination 1 determines whether the peak intensity is equal to or greater than a peak set value. The peak setting value was set to twice the peak intensity observed when no resonance was occurring. (Step 5) If the peak intensity does not reach the peak set value, no resonance is occurring. If the workpiece has a complex structure, it is assumed that multiple vibration factors have combined to increase the vibration, and the feed speed is reduced to reduce the vibration (the control unit 70 sends a control signal to decelerate the feed motor 32 via the servo amplifier), and the process returns to step 1 and repeats from there.

[0029] (Step 6) If the peak intensity exceeds the peak setting value, a second resonance determination is further performed for the first pitch. The second resonance determination determines whether or not the measured peak frequency fp matches the estimated cutting frequency of the saw blade pitch, i.e., whether or not the measured peak frequency fp is N times (N is an integer equal to or greater than 1) the cutting frequency fcut (first pitch). (Step 7) If the conditions for Resonance Judgment 2 are not met (NO), Resonance Judgment 3 for the second pitch is performed. Resonance Judgment 3 determines whether or not the measured peak frequency fp matches the estimated cutting frequency of the saw blade pitch, i.e., whether or not the measured peak frequency fp is N times (N is an integer equal to or greater than 1) the cutting frequency fcut (second pitch). If the conditions for resonance determination 3 are not met, resonance due to the cutting frequency is not occurring. To reduce vibration, the feed speed is reduced (a control signal for reducing the speed is sent from the control unit 70 via the servo amplifier of the feed motor 32), and the process returns to step 1 and repeats from there.

[0030] (Step 8) Resonance is occurring when the conditions are met in Resonance Judgment 2 or Resonance Judgment 3. Therefore, the rotation speed is changed (accelerated or decelerated) to avoid resonance. (Step 9) If the rotation speed has not reached the upper limit, the control unit 70 sends a control signal to the inverter of the rotation motor 28 to accelerate the rotation, and then the process returns to step 1 and repeats the steps from there.

[0031] (Step 10) If the rotation speed has reached the upper limit, the control unit 70 sends a control signal to decelerate the rotation motor 28 via the inverter, and the rotation motor 28 is decelerated. Then, the process returns to step 1 and the subsequent steps are repeated.

[0032] Example 2 FIG. 3 is a schematic diagram of the band saw of the second embodiment. The band saw of Example 2 includes a saw blade vertical position measurement sensor 50 that detects the height position of the saw blade 24, and a saw blade horizontal position measurement sensor 51 that detects the horizontal position of the saw blade 24. A judgment unit compares the measurement value of the vibration measurement sensor 40 with the vibration set value, the measurement value of the saw blade vertical position measurement sensor 50 with the saw blade height change set value, and the measurement value of the saw blade horizontal position measurement sensor 51 with the saw blade position set value. A control unit 70 controls at least one of the rotation speed of the rotation motor 28 and the rotation speed of the feed motor 32 based on the judgment of the judgment unit 60.

[0033] The saw blade vertical position measuring sensor 50 is a laser sensor that detects the height position of the saw blade 24, and the saw blade horizontal position measuring sensor 51 is a laser sensor that detects the horizontal position of the saw blade 24. Both are disposed on a fixture 52 attached to the lifting frame 29. The fixture 52 moves up and down together with the lifting frame 29.

[0034] Figure 4 is an explanatory diagram of a saw blade vertical position measurement sensor that detects the height position. In this figure, the saw blade 24 rotates in a direction perpendicular to the paper surface. The sensor that detects the height position of the saw blade 24 is a pair of laser sensors positioned to sandwich the upper end of the saw blade 24. When the upper end of the saw blade 24 moves upward due to the band-like laser irradiation, the laser irradiation is blocked and the irradiation amount changes, so the height position of the saw blade 24 can be detected. This makes it possible to check for cutting delays of the saw blade 24.

[0035] Figure 5 is an explanatory diagram of the saw blade horizontal position measurement sensor that detects the horizontal position. In this figure, the saw blade 24 rotates in a direction perpendicular to the paper surface. The sensor that detects the horizontal position of the saw blade 24 is a laser displacement sensor positioned opposite the side of the saw blade 24 so that it can irradiate the side with a laser. The laser irradiation detects the distance between the side of the saw blade 24 and the sensor. When this detected distance exceeds the set saw blade position value, a load is applied from the vertical position of the saw blade 24, causing a horizontal position deviation that twists the saw blade 24, and a bent cut can be detected.

[0036] The determination unit 60 compares the measurement value of the vibration measuring sensor 40 with the vibration set value, the measurement value of the saw blade vertical position sensor 50 with the saw blade height change set value, and the measurement value of the saw blade horizontal position measuring sensor 51 with the saw blade position set value. The vibration setting value is set from the acceleration value that suddenly and instantaneously increases before the saw blade 24 breaks, measured by the vibration measurement sensor 40 during cutting (response acceleration). This value corresponds to several times the value during cutting when chips and cutting noise are good. The saw blade height change setting is the difference between the latest and previous saw blade height average values ​​calculated from measurements taken over a specified period of time. This difference changes rapidly when the feed speed is changed and gradually approaches zero over time. The saw blade height change setting is set to less than half the automatic feed acceleration rate. For example, when the automated feed measurement is 0.25 mm / min, the average change threshold is set to 0.125 mm. The saw blade position setting is also set to exceed the horizontal position fluctuation range (±0.5 mm) during normal cutting, as confirmed in tests.

[0037] Based on the determination by the determination unit 60, the control unit 70 controls at least one of the rotation speed of the rotation motor 28 and the rotation speed of the feed motor 32. Specifically, the control unit 70 sends control signals to the inverter of the rotation motor 28 and to the servo amplifier of the feed motor 32, respectively, to control the respective speeds. Other configurations are the same as those of the band saw shown in FIG. 1 and are designated by the same reference numerals.

[0038] [Processing flow] The judgment flow using the band saw of Example 2 having the above configuration will be described below. FIG. 6 is a process flow diagram using the band saw of Example 2.

[0039] (Step 21) During operation of the band saw 10 of the present invention, the saw blade horizontal position measuring sensor 51 collects the saw blade position for a predetermined time, which in this embodiment is one second. (Step 22) It is determined whether or not the measurement value of the saw blade horizontal position measuring sensor 51 exceeds the saw blade position setting value.

[0040] (Step 23) When the measured value is equal to or greater than the set saw blade position, the saw blade 24 is not in a stable cutting state (steady state) and is bending the saw blade 24. In this case, accelerating the feed speed and rotation speed will have a significant effect on defects in the saw blade 24, so the feed motor 32 is stopped and the rotation motor 28 is kept running. Operation is continued for a predetermined time. (Step 24) It is again determined whether or not the measurement value of the saw blade horizontal position measuring sensor 51 has exceeded the saw blade position setting value.

[0041] (Step 25) When the measured value is equal to or greater than the set saw blade position value, the machine is not in a steady state and excessive cutting bending is occurring. Therefore, if the machine continues in this state, there is a high possibility that a malfunction such as damage to the saw blade will occur eventually. Some kind of inspection and maintenance of the saw blade 24 is required, and operation is stopped. (Step 26) If the measured value has not reached the set saw blade position value, the cutting bend of the saw blade 24 tends to decrease due to continued operation for a predetermined period of time, so the feed motor 32 is set to a slower speed (for example, 0.25 mm / min).

[0042] (Step 27) The feeding of the saw blade 24 is resumed to perform cutting, and step 21 and subsequent steps are repeated. (Step 28) When the measured value does not reach the saw blade position setting, bending of the saw blade 24 is not occurring. During operation of the band saw 10 of the present invention, vibrations are collected by the vibration measuring sensor 40 and the height of the saw blade is collected by the saw blade vertical position measuring sensor 50 for a predetermined time, 30 seconds in this embodiment.

[0043] (Step 29) It is determined whether or not the measurement value of the vibration measuring sensor 40 exceeds the vibration set value. The determining unit 60 determines whether or not there is a sign of saw blade breakage from the measurement value of the vibration measuring sensor 40 and the vibration set value. (Step 30) If the measured value does not reach the vibration setpoint, the change in height of the saw blade 24 is checked. If the height exceeds the predetermined saw blade height change setting value, the steady state is not reached and a delay in saw blade cutting occurs, and increasing the saw blade feed speed will place excessive load on the saw blade, so steps 21 and onwards are repeated.

[0044] (Step 31) When the change in height of the saw blade 24 has not reached the set value for the change in height of the saw blade 24, the feed speed of the saw blade 24 can be accelerated in a steady state. It is determined whether or not the upper limit of the feed speed of the saw blade 24 has been reached. If the upper limit has already been reached, step 21 and subsequent steps are repeated. (Step 32) If the upper limit of the feed speed of the saw blade 24 has not been reached, the feed speed is increased (for example, by +0.25 mm / min), and step 21 and subsequent steps are repeated.

[0045] (Step 33) When the measured value reaches the vibration setting value, the frequency of exceeding the vibration setting value is checked. The frequency is calculated by counting how many times the vibration setting value is exceeded in a predetermined time. In this embodiment, as an example, the vibration exceeding setting value is set to 30 times that the vibration setting value is exceeded in a predetermined time (e.g., 30 seconds). (Step 34) When the vibration excessive setting value is not reached, sudden vibration of the saw blade 24, which is a sign of saw blade breakage, occurs, and the feed rate is excessive. On the other hand, steady vibration is not occurring, and the saw blade 24 can be operated at the upper limit of its rotational speed. It is determined whether the rotation speed of the saw blade 24 has reached an upper limit value.

[0046] (Step 35) If the upper limit has already been reached, the feed rate is reduced and step 21 and subsequent steps are repeated. (Step 36) If the upper limit has not been reached, the rotation speed is accelerated, and then steps 21 and after are repeated.

[0047] (Step 37) When the vibration exceedance setting value is reached, large steady vibration is occurring, so resonance determination 1 is performed. The frequency analysis unit 80 breaks down the measurement value of the vibration measurement sensor 40 into frequency components and displays the peak intensity of each frequency. Resonance determination 1 determines whether the peak intensity is equal to or greater than a peak set value. The peak setting value was set to twice the peak intensity observed when no resonance was occurring. If the peak intensity does not reach the peak set value, no resonance is occurring. If the workpiece has a complex structure, it is assumed that multiple vibration factors have combined to increase the vibration, and the feed speed is reduced to reduce the vibration (the control unit 70 sends a control signal to decelerate the feed motor 32 via the servo amplifier), and the process returns to step 21 and repeats the subsequent steps.

[0048] (Step 38) If the peak intensity exceeds the peak setting value, a second resonance determination is further performed for the first pitch. The second resonance determination determines whether or not the measured peak frequency fp matches the estimated cutting frequency of the saw blade pitch, i.e., whether or not the measured peak frequency fp is N times (N is an integer equal to or greater than 1) the cutting frequency fcut (first pitch). (Step 39) If the conditions for Resonance Judgment 2 are not met (NO), Resonance Judgment 3 for the second pitch is performed. Resonance Judgment 3 determines whether or not the measured peak frequency fp matches the estimated cutting frequency of the saw blade pitch, i.e., whether or not the measured peak frequency fp is N times (N is an integer equal to or greater than 1) the cutting frequency fcut (second pitch). If the conditions for resonance determination 3 are not met, resonance due to the cutting frequency is not occurring. To reduce vibration, the feed speed is reduced (a control signal for reducing the speed is sent from the control unit 70 via the servo amplifier of the feed motor 32), and the process returns to step 21 and repeats the subsequent steps.

[0049] (Step 40) Resonance is occurring when the conditions are met in Resonance Judgment 2 or Resonance Judgment 3. Therefore, the rotation speed is changed (accelerated or decelerated) to avoid resonance. (Step 41) If the rotation speed has not reached the upper limit, the control unit 70 sends a control signal to the inverter of the rotation motor 28 to accelerate the rotation, and then the process returns to step 21 and repeats the subsequent steps.

[0050] (Step 42) If the rotation speed has reached the upper limit, the control unit 70 sends a control signal to decelerate the rotation motor 28 via the inverter, and the rotation motor 28 is decelerated. After that, the process returns to step 21 and the subsequent steps are repeated.

[0051] According to the present invention, resonance due to the cutting frequency can be automatically avoided without measuring the resonance frequency in advance, and the operating speed can be automatically adjusted efficiently even without experienced skills. Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and various modifications can be made without departing from the spirit and scope of the present invention. Furthermore, the present invention is not limited to the combinations shown in the embodiments, but can be implemented in various combinations. [Explanation of symbols]

[0052] 10 Bandsaw 12 Frame body 13 Upper frame 14 Lower frame 15 pillars 20 Cutting means 24 saw blade 26 wheels 28 Rotation motor 29 Lifting frame 30 Feeding means 32 Feed motor 33 Ball screw 40 Vibration measurement sensor 50 Saw blade vertical position measurement sensor 51 Saw blade horizontal position measurement sensor 52 Fixtures 60 Judgment section 70 Control Unit 80 Frequency analysis section

Claims

1. A band saw comprising: an endless saw blade; a pair of wheels around which the saw blade is wound; a cutting means having a rotation motor connected to one of the wheels for rotating it; and a feeding means having a feeding motor for moving the cutting means in an up-and-down cutting direction, A vibration measurement sensor that detects vibrations generated during cutting; a frequency analysis unit that resolves the measurement value of the vibration measurement sensor into frequency components and expresses peak intensities; a determination unit that determines whether the peak intensity of the frequency analysis unit is equal to or greater than a peak setting value and whether it matches an estimated cutting frequency of the saw blade pitch; A band saw comprising a control unit that controls at least one of the rotation speed of the rotating motor and the rotation speed of the feed motor based on the determination of the determination unit.

2. 2. The band saw according to claim 1, a saw blade vertical position measurement sensor that detects the height position of the saw blade; a saw blade horizontal position measuring sensor for detecting the horizontal position of the saw blade; the determination unit compares the measurement value of the vibration measurement sensor with a vibration set value, the measurement value of the saw blade vertical position measurement sensor with a saw blade height change set value, and the measurement value of the saw blade horizontal position measurement sensor with a saw blade position set value; The band saw is characterized in that the control unit controls at least one of the rotation speed of the rotation motor and the rotation speed of the feed motor based on the determination of the determination unit.

3. The band saw according to claim 2, The band saw is characterized in that the saw blade vertical position measuring sensor is a laser sensor attached to a lifting frame of the cutting means to detect the height position of the saw blade.

4. The band saw according to claim 2, The band saw is characterized in that the saw blade horizontal position measuring sensor is a laser sensor attached to a lifting frame of the cutting means to detect the horizontal position of the saw blade.

5. The band saw according to claim 1 or 2, The band saw is characterized in that the vibration measuring sensor is provided at a connection point between a pillar of a frame body to which the feeding means is attached and an upper frame.

Images