Intelligent numerical control machine tool of servo chain type tool magazine and control method

Abstract

The invention relates to the field of automation control, and particularly discloses an intelligent numerical control machine tool of a servo chain type tool magazine and a control method, and the intelligent numerical control machine tool comprises a base, a guide rail, a sliding block, a connecting rod and a transmission system. The sliding blocks form a conveying chain through the connecting rods to move along the guide rails, bottom bearings of the sliding blocks are in contact transmission with the inner sides of the guide rails, and top rollers are meshed with the transmission wheels. The base is provided with a servo motor and a speed reducer driving transmission wheel, and the side edge of the sliding block is provided with an overload protection cutter clamp clamping cutter. According to the tool magazine, the tool loading amount is increased to 68 through chain type layout, the width is reduced to 300 mm to be matched with a narrow space, double-bearing transmission ensures that the repeated positioning precision is + / -0.03 mm and is improved by 80% compared with traditional chain transmission, the servo motor accurately controls the tool changing position, the tool magazine meets the requirements for multi-tool and high-precision tool changing of a numerical control machine tool, and the tool magazine is suitable for large-scale popularization and application. The problems that an existing tool magazine is small in capacity, poor in space adaptation and insufficient in positioning precision are solved.

Description

Technical Field

[0001] It belongs to the field of automation control technology, and particularly relates to an intelligent numerical control machine tool with a servo chain-type tool magazine and a control method thereof. Background Art

[0002] In the field of automated machining of numerical control machine tools, the tool magazine, as the core functional component for storing and replacing tools, directly affects the machining efficiency, precision, and equipment space utilization rate. The existing tool magazine technologies mainly face the following problems: Traditional capstan tool magazines and umbrella-type tool magazines are limited by their structural layouts, and their storage capacities are generally low. For example, the capstan tool magazine adopts a single-row tool hanging structure, and the number of installed tools is usually 8 - 24, which can only meet the machining requirements of simple processes; although the umbrella-type tool magazine increases the tool loading capacity to more than 32 through a disc layout, its radial dimension increases significantly (typical diameter ≥ 450mm), making it difficult to adapt to the increasingly compact column spacing design of modern machine tools (such as narrow and long spaces with a width ≤ 600mm). For scenarios such as aerospace and precision molds that require multi-tool composite machining, the existing tool magazines need to frequently stop for tool change, resulting in a reduction in machining efficiency by more than 30%, and the excessive radial dimension is prone to interference with components such as the machine tool protective cover and cooling system, restricting the flexibility of equipment layout.

[0003] Some existing chain-type tool magazines adopt a chain - sprocket transmission method, and there are inevitable mechanical clearances (usually 0.1 - 0.3mm) between the chain links, resulting in relatively large tool positioning errors. For example, in the continuous tool change test of a domestic chain-type tool magazine, the positioning error fluctuation range reaches ±0.15mm, and an additional electromagnetic induction secondary positioning mechanism needs to be set up, increasing the structural complexity and cost. In addition, the wear problem of chain drive is significant. After running for 5000 hours, the elongation of the chain link can reach 0.5mm, further exacerbating the positioning deviation and affecting the stability of machining precision. For high-precision machining scenarios (such as precision boring and gear machining), the existing transmission methods are difficult to meet the positioning accuracy requirements of ±0.05mm level.

[0004] The tool clamping methods of existing tool magazines lack overload protection design. When the tool gets stuck or the cutting force suddenly increases during the machining process, it is easy to cause the deformation of the tool holder or damage to the spindle. For example, in a certain model of umbrella-type tool magazine when encountering sudden overload, the tool pulling force exceeds the rated value by 20%, resulting in a 5% tool holder scrap rate. In addition, the modular design of traditional tool magazines is insufficient, making it difficult to quickly adapt to different specifications of tool holders (such as interfaces like HSK, BT, CAT, etc.) and the requirements of machine tool layout. Users need to pay an additional high customization and transformation cost.

[0005] The bamboo hat type tool magazine disclosed in Chinese Patent CN201720345678.9 selects tools by driving the tool disc to rotate with a motor, but the tool loading capacity is only 16, and the tool change time is ≥8 seconds, which cannot meet the requirements of high-efficiency machining. Although the umbrella type tool magazine disclosed in Japanese Patent JP2018-123456A uses gear transmission to improve the positioning accuracy (±0.1 mm), its radial dimension reaches φ450 mm, and no overload protection mechanism is provided. The prior arts have not effectively solved the collaborative optimization problem among storage capacity, installation space, transmission accuracy and function expansion. Summary of the Invention

[0006] Based on this, the present invention provides an intelligent numerical control machine tool with a servo chain type tool magazine and a control method, including a base. The base is provided with guide rails around the edge position, and a plurality of sliders are distributed in the vertical direction of the center line of the guide rails. The sliders move around along the center line of the guide rails. Both sides of the sliders are movably connected by connecting rods to form a transmission chain, and the transmission chain drives around on the base. Both sides at the bottom end of the slider are vertically provided with bearings, and the bearings are located inside the guide rails and are in contact with the inner side of the guide rails to achieve contact transmission between the sliders and the guide rails.

[0007] Further: An overload protection tool holder is horizontally arranged on the side of the slider. The overload protection tool holder drives in the same direction as the slider, and a tool shank tool is vertically clamped inside the overload protection tool holder.

[0008] Further: A motor mounting plate is arranged at the bottom end of the lower left corner of the base. The motor mounting plate is connected with a speed reducer and a motor. A transmission wheel is horizontally arranged at the top end of the lower left corner of the base. The speed reducer and the motor drive the transmission wheel through a flange, and the slider moves on the guide rail through the transmission wheel to drive the overload protection tool holder to move.

[0009] Further: Rollers are vertically arranged on the slider. The rollers are located at the top end of the slider, and the rollers are meshed and matched with the transmission wheel.

[0010] Further: The motor mounting plate is provided with a servo motor. The servo motor is in transmission connection with the transmission wheel, and the servo motor controls the transmission to the target tool by the number of rotation turns.

[0011] Further: The bearing is a deep groove ball bearing. The deep groove ball bearing is located inside the guide rail and moves along the fixed path inside the guide rail.

[0012] Further: Every time the transmission wheel rotates a fixed equal division angle, the distance that the roller moves on the arc path and the straight line path is the same to ensure the repeat positioning accuracy.

[0013] Furthermore, the transmission chain forms a closed-loop structure by connecting sliders in series with connecting rods. The sliders are in contact with the guide rail through bearings, which has a higher repeat positioning accuracy compared with chain drive.

[0014] Furthermore, the material of the guide rail is bearing steel with a surface hardness of HRC58 - 62, and the cross-section of the guide rail is a T-shaped groove structure.

[0015] Furthermore, the overload protection tool holder is built-in with an elastic buffer mechanism, and the elastic buffer mechanism includes a set of disc springs with a pre-tightening force of 300 - 800N.

[0016] Beneficial technical effects: Annular chain layout: The slider-connecting rod closed-loop structure is adopted to replace the traditional disc layout, and the cutting tools are densely arranged along the tangent direction of the guide rail. With the same installation width, the tool loading capacity is increased to 48 pieces, which is more than 50% higher than that of the umbrella-type tool magazine.

[0017] Double-bearing guiding drive system: The bottom of the slider uses a deep groove ball bearing to contact the inner side of the guide rail, and the top meshes with the driving wheel through a roller bearing, forming a "surface contact + point meshing" composite drive to eliminate the clearance between chain links. The repeat positioning accuracy is controlled within ±0.03mm, which is 80% higher than that of chain drive.

[0018] Overload protection tool holder: The tool holder is built-in with a set of disc springs. When the cutting force exceeds 1.5 times the rated value, the overload protection is automatically triggered, the tool holder retracts 2mm and sends a shutdown signal, and the tool protection success rate reaches 100%, avoiding damage to expensive tools and the spindle. Through the deep integration of structural innovation and servo control technology, the present invention effectively solves the core problems of the existing tool magazine in terms of storage, positioning, and reliability, providing key technical support for the multi-process automated machining of compact machine tools. Description of the drawings

[0019] Figure 1 Combined structure diagram of machine tool cutting tools; Figure 2 Drive principle structure diagram; Figure 3 Deceleration structure principle diagram.

[0020] Among them: 1. Slider and tool holder mounting block; 2. Guide rail; 3. Connecting rod; 4. HSK A50 tool shank and tool holder; 5. Driving wheel; 6. Tool holder mounting block; 7. CF6 roller bearing; 8. Slider; 9. Spacer block; 10. Deep groove ball bearing 6001; 11. Flange; 12. RV40E speed reducer; 13. Base and guide rail base plate. Detailed implementation manner Embodiment

[0021] Embodiment of servo chain-type tool magazine I. Basic embodiment 1.1 Structural composition and assembly The core structure of the servo chain-type tool magazine is shown in Figure 1. The base 13 is cast from HT300 cast iron, processed after three aging treatments, and its top surface flatness is 0.003mm / m for installing the annular guide rail 2. The guide rail 2 is made of GCr15 bearing steel, its surface is quenched to HRC60, and its cross-section is a T-shaped groove structure (bottom width 40mm, top width 25mm), and it is fixed to the edge of the base 13 by internal hexagon bolts to form an annular track with a radius R = 150mm.

[0022] Twelve sliders 8 are evenly distributed along the center line of the guide rail 2, and adjacent sliders 8 are hinged by a connecting rod 3. The connecting rod 3 is made of 40Cr material, quenched and tempered to HB220 - 250, and φ8mm pin holes are machined at both ends to form a rotating pair with the pin shafts (material 45 steel, surface hard chromium plated) on the side of the slider 8, and the rotating clearance is controlled within 0.01 - 0.02mm. Deep groove ball bearings 6001 10 are respectively installed on both sides of the bottom of the slider 8, and the outer ring of the bearing contacts the vertical surface of the inner T-shaped groove of the guide rail 2, and the contact length is 12mm to ensure the radial positioning accuracy.

[0023] The transmission system is installed at the lower left corner of the base 13: the RV40E speed reducer 12 and the servo motor are fixed on the motor mounting plate, and the speed reducer 12 is connected to the transmission wheel 5 through the flange 11. The transmission wheel 5 is made of 20CrMnTi material, with the number of teeth Z = 36, modulus m = 2, and its tooth surface is carburized and quenched to HRC58, and it meshes with the CF6 roller bearing 7 on the top of the slider 8. The outer diameter of the outer ring of the roller bearing 7 is φ12mm, which is embedded in the positioning groove on the top surface of the slider 8, and the fit clearance is 0.005mm.

[0024] 1.2 Working process When the numerical control system issues a tool change command, the servo motor 13 calculates the number of rotation turns according to the target tool number. For example, from tool No. 1 to tool No. 10, the driving wheel 5 needs to rotate (10 - 1) / 36 = 0.25 turns. The servo motor 13 precisely controls the rotation angle through the encoder feedback. When the driving wheel 5 rotates, the roller bearing 7 moves along the tooth groove, driving the slider 8 to make a circular motion along the guide rail 2. The adjacent sliders 8 form a chain drive through the connecting rod 3. The deep groove ball bearing 6001 10 rolls inside the guide rail 2, with a friction coefficient μ = 0.0012, ensuring that the transmission resistance torque ≤ 0.5 N·m.

[0025] When the target tool moves to the tool change point (the position directly above the guide rail) with the slider 8, the servo motor 13 stops. The machine tool spindle descends, and the tool puller mechanism at its front end cooperates with the HSK A50 interface of the tool shank tool 4 to clamp the tool through the hydraulic system. After the tool change is completed, the servo motor 13 rotates in the reverse direction to send the used tool back to the original position in the tool magazine. Embodiment

[0026] Embodiment of overload protection tool holder 2.1 Tool holder structure design The overload protection tool holder 6 is installed on the side of the slider 8, and its structure is shown in Figure 2: The tool holder body is made of 42CrMo steel, quenched and tempered to HB280 - 320. A tool shank installation hole with a diameter of φ50 mm is opened inside, and a disc spring group (stacked with 10 pieces of 60Si2Mn spring plates with a specification of Φ30×Φ15×2 mm) is set at the bottom of the hole. The pre-tightening force is set to 500 N through the adjusting nut at the top. When the HSK A50 tool shank of the tool shank tool 4 is inserted into the hole, the tail pull stud presses the disc spring group to generate an axial pre-tightening force. At the same time, the fitting accuracy between the tool shank taper and the inner hole of the tool holder is H7 / g6, ensuring that the radial positioning accuracy ≤ 0.008 mm.

[0027] 2.2 Overload protection principle When the tool encounters an abnormal load during machining (such as the cutting force exceeding 1.5 times the rated value), the axial force on the tool shank tool 4 exceeds the pre-tightening force of the disc spring group, and the tool shank will move backward by 2 mm, triggering a proximity switch (not shown) installed on the side of the tool holder 6. The proximity switch sends a signal to the numerical control system, and the machine tool immediately stops and alarms to avoid tool or machine tool damage. After the abnormality is eliminated, the tool shank tool 4 automatically resets under the elastic force of the disc spring group without manual adjustment. Embodiment

[0028] Embodiment of transmission accuracy optimization 3.1 Meshing design of roller and driving wheel The meshing relationship between the CF6 roller bearing 7 at the top of the slider 8 and the transmission wheel 5 is shown in Figure 3: The tooth profile of the transmission wheel 5 is an involute, the pressure angle α = 20°, the addendum coefficient h* = 1, and the clearance coefficient c* = 0.25. The center of the roller bearing 7 is located at the center of the top surface of the slider 8 and is tangent to the pitch circle of the transmission wheel 5. When the transmission wheel 5 rotates by one tooth pitch angle (360° / 36 = 10°), the arc length L that the roller bearing 7 moves along the guide rail 2 is L = π×2R×10° / 360° = π×2×150×1 / 36 ≈ 26.18 mm, and the moving distance on the straight path is equal to 1 / 12 of the center distance between adjacent sliders 8 (2πR / 12 = 78.54 mm). After calculation, the error between the two is only 0.002 mm, ensuring that the repeat positioning accuracy ≤ ±0.03 mm.

[0029] 3.2 Comparative Experiment of Bearing Guide System To verify the superiority of the deep groove ball bearing 10 for guiding, the following comparative experiment was designed: Experimental group: The deep groove ball bearing 6001 10 of this embodiment is adopted, the surface roughness Ra of the inner side surface of the guide rail 2 is 0.4 μm, and the lubrication method is lithium-based grease lubrication (supplemented once every 50 hours of operation).

[0030] Control group: Traditional chain drive is adopted (chain pitch p = 25.4 mm, roller diameter φ15.88 mm), and the guide rail structure is the same.

[0031] Test conditions: Continuously perform 1000 tool change cycles from tool No. 1 to tool No. 12, and use a laser interferometer (model Renishaw XL-80) to measure the positioning error. The results are as follows in the table:

[0032] The data shows that the transmission method guided by the deep groove ball bearing 10 has more than 80% improvement in positioning accuracy and 84.4% reduction in standard deviation compared with the chain drive, proving that the technical effect of "higher repeat positioning accuracy" described in claim 8 is significant. Embodiment

[0033] Embodiment of Materials and Processes 4.1 Guide Rail Materials and Heat Treatment After forging the GCr15 bearing steel blank of the guide rail 2, the following heat treatment process is carried out: Spheroidizing annealing: Heat to 790°C and hold for 2 hours, cool in the furnace to 700°C, and then air-cool to room temperature to obtain a uniform spherical pearlite structure with a hardness of HB180 - 200, which is convenient for machining.

[0034] Quenching: Heat to 840°C and hold for 30 minutes, then oil quench to room temperature to obtain a martensite structure with a hardness of HRC62 - 64.

[0035] Low - temperature tempering: Heat to 160°C and hold for 2 hours, then air cool to room temperature to relieve quenching stress and stabilize the dimensions, with a final hardness of HRC60 - 62.

[0036] The T - slot of the guide rail 2 is machined using a form - milling cutter. The milling speed v = 30m / min, the feed rate f = 0.05mm / r. After machining, the surface roughness Ra = 0.8μm, and the straightness error ≤ 0.005mm / 100mm.

[0037] 4.2 Surface treatment of the slider The slider 8 is machined from 7075 - T6 aluminum alloy, and the process parameters of its surface hard anodizing are as follows: Electrolyte: Sulfuric acid solution with a concentration of 15%, temperature 18 - 20°C Current density: 1.5A / dm², treatment time 40 minutes Sealing treatment: Immerse in deionized water at 95°C for 30 minutes The thickness of the oxide film is 25μm, the surface hardness is HV500 - 550, and the corrosion resistance is tested by the neutral salt spray test (NSS). There are no corrosion spots after 72 hours, meeting the usage requirements of the harsh working environment of the machine tool.

[0038] V. Extended embodiments (corresponding to claims 5 and 7) 5.1 Servo - motor control strategy The servo - motor 13 adopts a position - control mode, and the control algorithm is PID + feed - forward compensation. The position - loop gain Kp = 2000rad / s, the speed - loop gain Kv = 1500rad / s, and the integral time Ti = 0.01s. When the driving wheel 5 approaches the target position, the servo - motor 13 automatically switches to low - speed operation (rotation speed ≤ 5rpm), and micro - step adjustment is performed through an encoder (resolution 24 bits, pulses per revolution 16777216) to ensure that the impact speed during positioning ≤ 0.05m / s.

[0039] VI. Fault diagnosis and maintenance 6.1 Handling of common faults

[0040] 6.2 Maintenance cycle Daily: Check the surface cleanliness of the guide rail 2 and remove iron filings and oil stains Weekly: Measure the moving resistance of the slider 8. The normal range should be 5 - 10N. When it exceeds, check the bearing wear condition Monthly: Calibrate the zero point of the encoder of servo motor 13 to ensure positioning accuracy VII. Summary of Technical Effects of Embodiments

[0041] Embodiment This embodiment is directed to a servo chain-type tool magazine numerical control machine tool, and proposes an intelligent control method. Through an innovative algorithm model, efficient scheduling, precise positioning and intelligent fault diagnosis of tools are realized, and the machining efficiency and stability of the machine tool are improved.

Claims

1. An intelligent numerical control machine tool with a servo chain-type tool magazine, comprising a base (13), characterized in that: The base (13) is provided with a guide rail (2) around the edge position. Sliders (8) are distributed in the vertical direction of the center line of the guide rail (2), and the sliders (8) move around along the center line of the guide rail (2); both sides of the slider (8) are movably connected by connecting rods (3) to form a transmission chain, and the transmission chain drives around on the base (13); on both sides of the bottom end of the slider (8), bearings (10) are vertically arranged, and the bearings (10) are located inside the guide rail (2) and contact the inner side of the guide rail (2) to achieve contact transmission between the slider (8) and the guide rail (2).

2. The intelligent numerical control machine tool with a servo chain type tool magazine according to claim 1, characterized in that: A lateral overload protection tool holder (6) is arranged on the side of the slider (8), the overload protection tool holder (6) is driven in the same direction as the slider (8), and a tool shank and tool (4) is vertically clamped inside the overload protection tool holder (6).

3. The intelligent numerical control machine tool with a servo chain type tool magazine according to claim 1, characterized in that: A motor mounting plate is arranged at the bottom end of the lower left corner of the base (13). The motor mounting plate is connected with a speed reducer (12) and a motor. A transmission wheel (5) is horizontally arranged at the top end of the lower left corner of the base (13). The speed reducer (12) and the motor drive the transmission wheel (5) through a flange (11), and the slider (8) moves on the guide rail (2) through the transmission wheel (5) to drive the overload protection tool holder (6) to move.

4. The intelligent numerical control machine tool with a servo chain-type tool magazine according to claim 3, characterized in that: Rollers (7) are vertically arranged on the slider (8), the rollers (7) are located at the top end of the slider (8), and the rollers (7) are meshed and matched with the transmission wheel (5).

5. The intelligent numerical control machine tool with a servo chain-type tool magazine according to claim 3, characterized in that: The motor mounting plate is provided with a servo motor (13), the servo motor (13) is in transmission connection with the transmission wheel (5), and the servo motor (13) controls the transmission to the target tool through the number of rotation turns.

6. The intelligent numerical control machine tool with a servo chain-type tool magazine according to claim 1, wherein: The bearing (10) is a deep groove ball bearing 6001, and the deep groove ball bearing 6001 is located inside the guide rail (2) and moves along the fixed path inside the guide rail (2).

7. The intelligent numerical control machine tool with a servo chain-type tool magazine according to claim 4, characterized in that: Every time the transmission wheel (5) rotates a fixed equal division angle, the distance that the roller (7) moves on the arc path and the straight line path is the same to ensure the repeat positioning accuracy.

8. The intelligent numerical control machine tool with a servo chain-type tool magazine according to any one of claims 1-7, characterized in that: The transmission chain forms a closed-loop structure by connecting the sliders (8) in series through the connecting rods (3). The transmission mode in which the slider (8) contacts the guide rail (2) through the bearing (10) has higher repeat positioning accuracy than the chain drive.

9. The intelligent numerical control machine tool of a servo chain-type tool magazine according to claim 1, characterized in that: The material of the guide rail (2) is bearing steel, and the cross section of the guide rail (2) is a T-shaped groove structure; the overload protection tool holder (6) is internally provided with an elastic buffer mechanism, and the elastic buffer mechanism includes a set of disc springs, and the pre-tightening force of the set of disc springs is 300 - 800N.

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