CNC milling combined machining device and machining method

Abstract

The invention relates to the technical field of computer numerical control milling machining, and particularly discloses a CNC milling combined machining device and method. The CNC milling combined machining device comprises a machine tool spindle, a CNC milling combined machining device and a CNC milling combined machining device, a workpiece is clamped on the workbench through a clamp assembly; and the control module is used for controlling the vibration parameters, the feeding speed and the cutting force of the cutter and milling the workpiece. The cutter can generate micron-sized elliptical orbit vibration under the ultrasonic frequency to form a periodic intermittent cutting effect, so that the cutter and a workpiece are periodically separated in the cutting process, the average cutting force and cutting heat can be reduced, the contact time of the cutter and the workpiece is shortened, the abrasion of the cutter is reduced, and chip accumulation can be inhibited.

Description

Technical Field

[0001] The present invention relates to the technical field of computer numerical control milling machining, and more specifically, the present invention relates to a CNC milling composite machining device and a machining method. Background Art

[0002] CNC milling is a subtractive manufacturing process that combines traditional milling with computer numerical control (CNC) technology. The movement of the machine is guided by pre-programmed G-code, which specifies the tool path, speed, and cutting depth. Currently, for the machining of difficult-to-machine materials such as titanium alloys, ceramics, composite materials, etc., the cutting force is relatively large, which causes greater wear on the tool and reduces the surface quality of the workpiece after machining.

[0003] Therefore, it is necessary to propose a CNC milling composite machining device and a machining method to at least partially solve the problems existing in the prior art. Summary of the Invention

[0004] A series of simplified concepts are introduced in the Summary of the Invention section, which will be further detailed in the Detailed Description section. The Summary of the Invention section of the present invention does not mean to attempt to define the key features and essential technical features of the claimed technical solution, nor does it mean to attempt to determine the protection scope of the claimed technical solution.

[0005] To at least partially solve the above problems, the present invention provides a CNC milling composite machining device, including:

[0006] A machine tool spindle, which is connected with a tool through an ultrasonic tool holder below.

[0007] A workbench, on which a workpiece is clamped through a fixture assembly.

[0008] A control module, which is used to control the vibration parameters, feed speed, and cutting force of the tool and machine the workpiece.

[0009] Preferably, the ultrasonic tool holder includes: a transducer connected to the machine tool spindle, and the tool is connected to the transducer.

[0010] Preferably, the transducer includes: a first pressing block, a plurality of piezoelectric rings, and a second pressing block arranged in sequence. Electrode plates are provided on the top and bottom of the piezoelectric rings. A horn is provided on the side of the second pressing block away from the first pressing block, and the tool is connected to the horn.

[0011] Preferably, the vibration parameters of the tool include: vibration frequency, vibration amplitude, and vibration trajectory.

[0012] Preferably, the control module includes:

[0013] A first control unit for controlling the vibration frequency of the cutting tool and the rotational speed of the machine tool spindle to satisfy a first set relationship, so that within the cutting cycle of each tooth of the cutting tool, there is at least one effective vibration separation cutting;

[0014] The formula of the first set relationship is:

[0015]

[0016] where f is the vibration frequency, with the unit of Hz, N is the rotational speed of the machine tool spindle, with the unit of r / min, and Z is the number of teeth of the cutting tool;

[0017] A second control unit for controlling the vibration amplitude of the cutting tool and the feed rate to satisfy a second set relationship, so that the vibration separation effect takes effect;

[0018] The formula of the second set relationship is:

[0019]

[0020] where A is the vibration amplitude of the cutting tool, with the unit of μm, V is the feed rate, with the unit of mm / min, and F Z is the feed per tooth, with the unit of mm / tooth;

[0021] A third control unit for controlling the vibration trajectory of the cutting tool and the cutting direction to satisfy a third set relationship, so as to optimize the chip evacuation;

[0022] The third set relationship is: the vibration trajectory is an elliptical trajectory, and the included angle between the major axis direction of the ellipse and the cutting direction is a set included angle, and the range of the set included angle is 30° to 80°.

[0023] Preferably, the control module further includes:

[0024] A feedback control unit for real-time monitoring of the cutting force and dynamically adjusting the vibration frequency, vibration amplitude or feed rate of the cutting tool according to the cutting force.

[0025] The present invention also provides a CNC milling composite machining method, including:

[0026] Determining initial machining parameters according to the material hardness of the workpiece and the type of the cutting tool; wherein the initial machining parameters are the initial vibration frequency, the initial vibration amplitude, the initial feed rate and the initial rotational speed of the machine tool spindle;

[0027] Under the condition of no workpiece, performing an idle vibration test on the cutting tool to verify the stability of the vibration trajectory of the cutting tool and the synchronization accuracy of the vibration frequency of the cutting tool and the rotational speed of the machine tool spindle;

[0028] Process the tested workpiece, detect the surface roughness of the tested workpiece and the wear degree of the tool, and optimize the initial machining parameters to obtain the optimized machining parameters;

[0029] Import the optimized machining parameters into the CNC system to perform batch machining on the workpiece.

[0030] Preferably, the determination of the initial machining parameters includes: selecting the initial vibration frequency and initial vibration amplitude of ultrasonic vibration according to the material hardness of the workpiece and the type of the tool, and matching the initial feed rate and the initial rotational speed of the machine tool spindle;

[0031] The initial vibration frequency and initial vibration amplitude can be selected within the corresponding set range, or can be determined by the following formula. Specifically:

[0032] The formula for determining the initial vibration frequency is:

[0033]

[0034] where, f 0 is the initial vibration frequency, with the unit of kHz, K is the material coefficient of the workpiece (for example, the material coefficient of titanium alloy is 0.8, and the material coefficient of ceramic is 1.2), and H is the material hardness of the workpiece;

[0035] The formula for determining the initial vibration amplitude is:

[0036] A 0 = 0.1 * D

[0037] where, A 0 is the initial vibration amplitude, with the unit of μm, and D is the diameter of the tool, with the unit of μm;

[0038] The initial feed rate and the initial rotational speed of the machine tool spindle are determined based on the formulas of the first set relationship and the second set relationship to ensure the vibration separation effect.

[0039] Preferably, it further includes:

[0040] Collect the historical machining data corresponding to the workpiece to be machined and input it into the trained neural network model to obtain the optimal machining parameters corresponding to the workpiece to be machined;

[0041] where, the historical machining data includes: the material of the workpiece, the type of the tool, and the surface roughness of the machined workpiece.

[0042] Preferably, optimizing the initial machining parameters includes:

[0043] If the surface roughness of the tested workpiece exceeds the roughness set value, increase the vibration frequency or decrease the feed rate;

[0044] If the wear degree of the cutting tool exceeds the wear set value, increase the vibration amplitude or reduce the cutting depth.

[0045] Compared with the prior art, the present invention has at least the following beneficial effects:

[0046] In the CNC milling composite machining device and machining method of the present invention, the ultrasonic tool holder can generate ultrasonic vibration, so that during the cutting process of the cutting tool, rotational movement, elliptical trajectory ultrasonic vibration and movement along the cutting path are carried out simultaneously. While the cutting tool is moving, the vibration parameters, feed speed and cutting force of the cutting tool are monitored and controlled in real time to ensure that the three movements of the cutting tool can cooperate with each other during the cutting process and improve the milling effect;

[0047] The cutting tool can generate elliptical trajectory vibration at the ultrasonic frequency, forming a periodic interrupted cutting effect, so that the cutting tool and the workpiece are periodically separated during the cutting process, which can reduce the average cutting force and cutting heat, reduce the contact time between the cutting tool and the workpiece, reduce the wear of the cutting tool, and can also inhibit chip accumulation.

[0048] In the CNC milling composite machining device and machining method of the present invention, other advantages, objectives and features of the present invention will be partially reflected by the following description, and partially will also be understood by those skilled in the art through the research and practice of the present invention. Brief Description of the Drawings

[0049] The drawings are used to provide a further understanding of the present invention, and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation to the present invention. In the drawings:

[0050] Figure 1 is a schematic structural diagram of the CNC milling composite machining device of the present invention;

[0051] Figure 2 is a schematic structural diagram of the transducer in the CNC milling composite machining device of the present invention;

[0052] Figure 3 is a schematic connection structure diagram of one group of piezoelectric rings and electrode plates in the CNC milling composite machining device of the present invention;

[0053] Figure 4 is a schematic structural diagram when the CNC milling composite machining device of the present invention cuts a workpiece;

[0054] Figure 5 is a flow chart of the CNC milling composite machining method of the present invention. Detailed Description of the Embodiments

[0055] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments, so that those skilled in the art can implement it with reference to the text of the specification.

[0056] It should be understood that the terms such as "having", "comprising" and "including" used herein do not exclude the presence or addition of one or more other elements or their combinations.

[0057] As Figure 1 shown, the present invention provides a CNC milling composite machining device, including:

[0058] A machine tool spindle 1, which is connected with a tool 3 through an ultrasonic tool holder 2 below;

[0059] A workbench 4, on which a workpiece 6 is clamped through a fixture assembly 5;

[0060] A control module, which is used to control the vibration parameters, feed speed and cutting force of the tool 3 and mill the workpiece 6.

[0061] As Figure 4 shown, the ultrasonic tool holder 2 can generate ultrasonic vibration, so that during the cutting process of the tool 3, it simultaneously performs rotational motion, elliptical trajectory ultrasonic vibration and movement along the cutting path. While the tool 3 is moving, the vibration parameters, feed speed and cutting force of the tool 3 are monitored and controlled in real time to ensure that the three motions of the tool 3 can cooperate with each other during the cutting process and improve the milling effect;

[0062] The tool 3 can generate elliptical trajectory vibration at the ultrasonic frequency, forming a periodic intermittent cutting effect, so that the tool 3 and the workpiece 6 are periodically separated during the cutting process, which can reduce the average cutting force and cutting heat, reduce the contact time between the tool 3 and the workpiece 6, reduce the wear of the tool 3, and can also inhibit chip accumulation.

[0063] As Figure 2 shown, in one embodiment, the ultrasonic tool holder 2 includes: a transducer connected to the machine tool spindle 1, and the tool 3 is connected to the transducer.

[0064] The tool 3 can be directly connected to the transducer or connected to the transducer through a separately provided horn; the transducer can make the tool 3 generate elliptical trajectory ultrasonic vibration.

[0065] As Figure 2 shown, in one embodiment, the transducer includes: a first pressure block 21, a plurality of piezoelectric rings 22 and a second pressure block 23 arranged in sequence. Electrode plates 24 are provided on the top and bottom of the piezoelectric ring 22. A horn 25 is provided on the side of the second pressure block 23 away from the first pressure block 21, and the tool 3 is connected to the horn 25.

[0066] Different types of cutting tools 3 are installed on the second pressing block 23 through clamping parts of the same standard; the second pressing block 23 and the horn 25 are integrally arranged;

[0067] The multiple piezoelectric rings 22 can be divided into two groups in different directions, such as Figure 3 As shown in the setting method of one group of piezoelectric rings 22 and electrode plates 24, electrode plates 24 cover the top and bottom of each piezoelectric ring 22 to provide an alternating voltage.

[0068] In one embodiment, the vibration parameters of the cutting tool 3 include: vibration frequency, vibration amplitude, and vibration trajectory.

[0069] The control module includes:

[0070] A first control unit for controlling the vibration frequency of the cutting tool 3 and the rotational speed of the machine tool spindle 1 to satisfy a first set relationship, so that within the cutting cycle of each tooth of the cutting tool 3, there is at least one effective vibration separation cutting;

[0071] The formula of the first set relationship is:

[0072]

[0073] where f is the vibration frequency, with the unit of Hz, N is the rotational speed of the machine tool spindle 1, with the unit of r / min, and Z is the number of teeth of the cutting tool 3;

[0074] Through the first control unit, ensuring the matching of the vibration frequency and the rotational speed of the machine tool spindle 1 can enable at least one effective vibration separation cutting within the cutting cycle of each tooth of the cutting tool 3, that is, each tooth of the cutting tool 3 intermittently contacts the workpiece 6, preventing the continuous contact between the cutting tool 3 and the workpiece 6, avoiding continuous cutting, ensuring the service life of the cutting tool 3, and reducing chip accumulation;

[0075] A second control unit for controlling the vibration amplitude of the cutting tool 3 and the feed rate to satisfy a second set relationship to enable the vibration separation effect to take effect;

[0076] The formula of the second set relationship is:

[0077]

[0078] where A is the vibration amplitude of the cutting tool 3, with the unit of μm, V is the feed rate, with the unit of mm / min, and F Z is the feed per tooth, with the unit of mm / tooth;

[0079] Through the second control unit, ensuring the coordination of the vibration amplitude and the feed rate to ensure the effective occurrence of vibration separation;

[0080] A third control unit for controlling the vibration trajectory of the cutting tool 3 to satisfy a third set relationship with the cutting direction, so as to optimize the chip discharge;

[0081] The third set relationship is: the vibration trajectory is an elliptical trajectory, the included angle between the major axis direction of the ellipse and the cutting direction is a set included angle, and the range of the set included angle is 30° to 80°;

[0082] Through the third control unit, the matching of the vibration trajectory and the cutting direction is ensured, the control of the elliptical trajectory direction is realized, that is, the major axis direction of the elliptical trajectory forms a set included angle with the cutting direction, so that the chips are effectively discharged and the accumulation affecting the cutting effect is prevented.

[0083] In one embodiment, the control module further includes:

[0084] A feedback control unit for real-time monitoring of the cutting force and dynamically adjusting the vibration frequency, vibration amplitude or feed speed of the cutting tool 3 according to the cutting force.

[0085] A piezoelectric force sensor can be installed on the machine tool spindle 1 or the workbench 4 to real-time monitor the cutting force. A threshold value is preset for the cutting force. When the cutting force exceeds the threshold value, the vibration amplitude is increased or the feed speed is decreased to avoid overloading of the cutting tool 3; the adjusted vibration amplitude or feed speed needs to satisfy the second set relationship.

[0086] As Figure 5 shown, the present invention also provides a CNC milling composite machining method, including:

[0087] S1. Determine the initial machining parameters according to the material hardness of the workpiece 6 and the type of the cutting tool 3; wherein the initial machining parameters are the initial vibration frequency, the initial vibration amplitude, the initial feed speed and the initial rotational speed of the machine tool spindle 1;

[0088] Further, the determination of the initial machining parameters includes: selecting the initial vibration frequency and the initial vibration amplitude of the ultrasonic vibration according to the material hardness of the workpiece 6 and the type of the cutting tool 3, and matching the initial feed speed and the initial rotational speed of the machine tool spindle 1;

[0089] The initial vibration frequency and the initial vibration amplitude can be selected within the corresponding set ranges, or can be determined by the following formula. Specifically:

[0090] The determination formula of the initial vibration frequency is:

[0091]

[0092] wherein, f 0is the initial vibration frequency, with the unit of kHz. K is the material coefficient of the workpiece 6 (for example, the material coefficient of titanium alloy is 0.8, and the material coefficient of ceramic is 1.2), and H is the material hardness of the workpiece 6;

[0093] The formula for determining the initial vibration amplitude is:

[0094] A 0 = 0.1 * D

[0095] where A 0 is the initial vibration amplitude, with the unit of μm, and D is the diameter of the tool 3, with the unit of μm;

[0096] The initial feed rate and the initial rotational speed of the machine tool spindle 1 are determined based on the formulas of the first setting relationship and the second setting relationship to ensure the vibration separation effect.

[0097] S2. Under the condition of no workpiece 6, conduct an idle vibration test on the tool 3 to verify the stability of the vibration trajectory of the tool 3 and the synchronization accuracy between the vibration frequency of the tool 3 and the rotational speed of the machine tool spindle 1;

[0098] Furthermore, the test of the stability of the vibration trajectory includes:

[0099] Set the ultrasonic tool holder 2 to the standby mode and control the machine tool spindle 1 to rotate idly at the target rotational speed;

[0100] Start the ultrasonic tool holder 2 and obtain the vibration trajectory of the tip of the tool 3; where the vibration trajectory is an elliptical trajectory;

[0101] Judge whether the fluctuations of the major axis and the minor axis of the elliptical trajectory are both within the set fluctuation range. If one of them is not within the set fluctuation range, it indicates that the stability of the vibration trajectory does not meet the standard. If the fluctuations of the major axis and the minor axis are both within the set fluctuation range, it indicates that the stability of the vibration trajectory meets the standard;

[0102] Through the test of the stability of the vibration trajectory, the installation of the tool 3 can be adjusted in time, the stability of the vibration trajectory can be improved, and the cutting quality of the workpiece 6 can be guaranteed;

[0103] Furthermore, the test of the synchronization accuracy between the vibration frequency of the tool 3 and the rotational speed of the machine tool spindle 1 includes:

[0104] Collect the phase of the pulse signal (such as pulses per revolution) of the encoder of the machine tool spindle 1 and the vibration signal of the tool 3 simultaneously;

[0105] Judge whether the phase jitter is less than the set value. If so, it indicates that the synchronization accuracy meets the standard. If not, it indicates that the synchronization accuracy does not meet the standard;

[0106] To ensure that the vibration period is synchronized with the rotation period of the machine tool spindle 1, the ultrasonic vibration power supply is triggered by the pulse signal of the encoder of the machine tool spindle 1, that is, the encoder signal is input into the external trigger port of the ultrasonic controller to generate a vibration signal synchronized with the machine tool spindle 1. For example, if the rotational speed of the machine tool spindle 1 is 6000 r / min (100 Hz) and the vibration frequency is set to 20 kHz, then the number of vibrations per revolution is 20 kHz / 100 Hz, which is 200 times.

[0107] By testing the synchronization accuracy between the vibration frequency of the tool 3 and the rotational speed of the machine tool spindle 1, when the synchronization accuracy does not meet the standard, it is possible to promptly check the installation stiffness of the horn related to the synchronization accuracy and other conditions, and promptly handle abnormal situations, further ensuring the machining quality of the workpiece 6.

[0108] S3. Machine the tested workpiece 6, detect the surface roughness of the tested workpiece 6 and the wear degree of the tool 3, and optimize the initial machining parameters to obtain optimized machining parameters.

[0109] S4. Import the optimized machining parameters into the CNC system and perform batch machining on the workpiece 6.

[0110] Furthermore, optimizing the initial machining parameters includes:

[0111] If the surface roughness of the tested workpiece 6 exceeds the roughness set value, increase the vibration frequency or decrease the feed rate.

[0112] If the wear degree of the tool 3 exceeds the wear set value, increase the vibration amplitude or decrease the cutting depth.

[0113] When machining a new workpiece 6, to ensure the machining quality, a small number of tested workpieces 6 can be machined first. The tested workpieces 6 are selected to be the same as the workpiece 6 to be machined. Then, obtain the surface roughness of the tested workpiece 6 and the wear degree of the tool 3. The initial machining parameters can be optimized based on the surface roughness of the tested workpiece 6 and the wear degree of the tool 3. The optimization tool can use the Taguchi method to design an orthogonal experiment to determine the parameter sensitivity, and adjust the initial machining parameters through the above optimization adjustment logic to obtain optimized machining parameters. Then, write the optimized machining parameters into the CNC system, and the workpiece 6 can be batch machined.

[0114] In one embodiment, it further includes:

[0115] Collect the historical machining data corresponding to the workpiece 6 to be machined and input it into the trained neural network model to obtain the optimal machining parameters corresponding to the workpiece 6 to be machined.

[0116] Among them, the historical machining data includes: the material of the workpiece 6, the type of the tool 3, and the surface roughness of the machined workpiece 6.

[0117] When the workpiece 6 to be processed has corresponding historical processing data, it is input into the trained neural network model, and then the optimal processing parameters corresponding to the workpiece 6 to be processed are output, improving the processing quality of the same workpiece 6.

[0118] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be understood as a limitation of the present invention.

[0119] In the present invention, unless otherwise clearly specified and defined, the terms "installed", "connected", "connected", "fixed", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection, an electrical connection, or communicable with each other; it can be directly connected, or indirectly connected through an intermediate medium, and can be the communication inside two elements or the interaction relationship between two elements, unless otherwise clearly defined. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0120] Although the embodiments of the present invention have been disclosed as above, it is not limited to the applications listed in the specification and embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the field, additional modifications can be easily achieved. Therefore, without departing from the general concept defined by the present invention, the present invention is not limited to the specific details and the examples shown and described here.

Claims

1. A CNC milling composite processing device, characterized in that: include: A machine tool spindle, with a tool connected to the bottom via an ultrasonic tool holder; A workbench on which a workpiece is clamped by a fixture assembly; The control module is used to control the vibration parameters, feed speed and cutting force of the tool to mill the workpiece.

2. The CNC milling composite processing device according to claim 1, characterized in that: The ultrasonic tool handle comprises: a transducer connected to a main shaft of a machine tool, and the tool is connected to the transducer.

3. The CNC milling compound processing device according to claim 2, characterized in that: The transducer comprises: a first pressure block, a plurality of piezoelectric rings and a second pressure block which are arranged in sequence, wherein the top and bottom of the piezoelectric rings are provided with electrode sheets, a variable amplitude rod is provided on a side of the second pressure block away from the first pressure block, and the tool is connected to the variable amplitude rod.

4. The CNC milling compound processing device according to claim 1, characterized in that: The vibration parameters of the tool include: vibration frequency, vibration amplitude and vibration trajectory.

5. The CNC milling composite processing device according to claim 4, characterized in that: The control module comprises: A first control unit, used for controlling the vibration frequency of the tool and the rotation speed of the machine tool spindle to satisfy a first set relationship, so that there is at least one effective vibration separation cutting in the cutting cycle of each tooth of the tool; A second control unit is used to control the vibration amplitude and feed speed of the tool to satisfy a second set relationship so that the vibration separation effect takes effect; The third control unit is used to control the vibration trajectory and cutting direction of the tool to satisfy a third set relationship to optimize the discharge of chips.

6. The CNC milling compound processing device according to claim 4, characterized in that: The control module also includes: The feedback control unit is used to monitor the cutting force in real time and dynamically adjust the vibration frequency, vibration amplitude or feed speed of the tool according to the cutting force.

7. A CNC milling compound processing method, using the CNC milling compound processing device according to any one of claims 1 to 6 for processing, characterized in that: include: Determine the initial machining parameters based on the material hardness of the workpiece and the type of tool; The initial machining parameters are initial vibration frequency, initial vibration amplitude, initial feed speed and initial speed of the machine tool spindle; Under the condition of no workpiece, the tool is subjected to no-load vibration test to verify the stability of the tool's vibration trajectory and the synchronization accuracy between the tool's vibration frequency and the machine tool spindle speed; Processing the tested workpiece, detecting the surface roughness of the tested workpiece and the degree of tool wear, and optimizing the initial processing parameters to obtain optimized processing parameters; The optimized processing parameters are imported into the CNC system to process the workpieces in batches.

8. The CNC milling composite processing method according to claim 7, characterized in that: Determination of the initial machining parameters includes: selecting the initial vibration frequency and initial vibration amplitude of the ultrasonic vibration according to the material hardness of the workpiece and the type of the tool, and matching the initial feed speed and the initial rotation speed of the machine tool spindle.

9. The CNC milling composite processing method according to claim 7, characterized in that: Also includes: Collect historical processing data corresponding to the workpiece to be processed, and input it into the trained neural network model to obtain the optimal processing parameters corresponding to the workpiece to be processed; The historical processing data includes: the material of the workpiece, the type of tool, and the surface roughness of the workpiece after processing.

10. The CNC milling composite processing method according to claim 8, characterized in that: Optimize initial processing parameters, including: If the surface roughness of the tested workpiece exceeds the roughness setting value, increase the vibration frequency or reduce the feed speed; If the tool wear exceeds the set wear value, increase the vibration amplitude or reduce the cutting depth.

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