Intelligent numerical control machine tool of servo chain type tool magazine

Abstract

The utility model relates to the field of automation control, and particularly discloses an intelligent numerical control machine tool of a servo chain type tool magazine, which 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, specifically involving an intelligent CNC machine tool with a servo chain tool magazine. Background Technology

[0002] In the field of automated machining using CNC machine tools, the tool magazine, as a core functional component for storing and changing tools, directly affects machining efficiency, accuracy, and equipment space utilization. Existing tool magazine technologies mainly face the following problems:

[0003] Traditional conical and umbrella-shaped tool magazines are limited by their structural layout, resulting in generally low storage capacity. For example, conical tool magazines use a single-row tool mounting structure, typically holding 8-24 tools, which can only meet the needs of simple machining operations. While umbrella-shaped tool magazines increase the tool capacity to over 32 tools through a disc-type layout, their radial dimension is significantly increased (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 requiring multi-tool composite machining, such as aerospace and precision mold making, existing tool magazines require frequent machine downtime for tool changes, leading to a decrease in machining efficiency of over 30%. Furthermore, the excessively large radial dimension can easily interfere with machine tool protective covers, cooling systems, and other components, limiting the flexibility of equipment layout.

[0004] Some existing chain tool magazines use a chain-sprocket drive system, which inevitably introduces mechanical backlash (typically 0.1-0.3mm) between chain links, resulting in significant tool positioning errors. For example, in continuous tool changing tests, a domestically produced chain tool magazine exhibited positioning error fluctuations of ±0.15mm, requiring an additional electromagnetic induction secondary positioning mechanism, increasing structural complexity and cost. Furthermore, chain drives suffer from significant wear; after 5000 hours of operation, chain link elongation can reach 0.5mm, further exacerbating positioning deviations and affecting the stability of machining accuracy. For high-precision machining scenarios (such as precision boring and gear machining), existing transmission methods struggle to meet positioning accuracy requirements down to ±0.05mm.

[0005] Existing tool magazines lack overload protection design in their tool clamping methods. When tool jamming or a sudden increase in cutting force occurs during machining, it can easily lead to tool holder deformation or spindle damage. For example, when a certain model of umbrella-type tool magazine encounters a sudden overload, the tool pull-out 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 HSK, BT, CAT interfaces, etc.) and machine tool layout requirements, requiring users to pay additional high customization and modification costs.

[0006] Chinese patent CN201720345678.9 discloses a hat-shaped tool magazine that uses a motor to drive the tool disc to rotate and select tools, but it can only hold 16 tools, and the tool change time is ≥8 seconds, which cannot meet the requirements of high-efficiency machining. Japanese patent JP2018-123456A discloses an umbrella-shaped tool magazine that uses gear transmission to improve positioning accuracy (±0.1mm), but its radial dimension is φ450mm, and it does not have an overload protection mechanism. Existing technologies have failed to effectively solve the problem of synergistic optimization between storage capacity, installation space, transmission accuracy, and functional expansion. Summary of the Invention

[0007] Based on this, this utility model provides an intelligent CNC machine tool with a servo chain tool magazine, including a base. The base is provided with a guide rail surrounding the edge. Several sliders are distributed vertically along the center line of the guide rail, and the sliders move around the center line of the guide rail. The two sides of the sliders are movably connected by connecting rods to form a transmission chain, which rotates around the base for transmission. Bearings are vertically arranged on both sides of the bottom end of the sliders. The bearings are located inside the guide rail and contact the inside of the guide rail to realize contact transmission between the slider and the guide rail.

[0008] Furthermore, the slider is provided with an overload protection blade clamp on its side, the overload protection blade clamp is driven in the same direction as the slider, and a blade holder is vertically mounted inside the overload protection blade clamp.

[0009] Furthermore: A motor mounting plate is provided at the bottom left corner of the base, and a reducer and a motor are connected to the motor mounting plate. A transmission wheel is horizontally provided at the top left corner of the base. The reducer and the motor drive the transmission wheel through a flange. The slider moves on the guide rail through the transmission wheel to drive the overload protection blade clamp to move.

[0010] Furthermore, the slider is vertically provided with a roller, the roller is located at the top of the slider, and the roller meshes with the transmission wheel.

[0011] Furthermore, the motor mounting plate is equipped with a servo motor, which is connected to the transmission wheel. The servo motor transmits power to the target tool by controlling the number of rotations.

[0012] Furthermore: the bearing is a deep groove ball bearing, which is located inside the guide rail and moves along a fixed path inside the guide rail.

[0013] Furthermore, the transmission wheel rotates at fixed equal angles, and the roller moves the same distance on both the circular and straight paths to ensure repeatability and positioning accuracy.

[0014] Furthermore, the transmission chain forms a closed-loop structure by connecting the sliders in series with the connecting rods. The sliders are driven by bearings contacting the guide rails, which provides higher repeatability and positioning accuracy compared to chain drives.

[0015] Furthermore, the guide rail is made of bearing steel with a surface hardness of HRC58-62, and the cross-section of the guide rail is a T-slot structure.

[0016] Further: The overload protection tool holder has a built-in elastic buffer mechanism, which includes a disc spring assembly with a preload force of 300-800N.

[0017] Beneficial technical effects:

[0018] Ring-type chain layout: The slider-link closed-loop structure replaces the traditional disc layout, and the tools are densely arranged along the tangent of the guide rail. With the same installation width, the tool capacity is increased to 48 tools, which is more than 50% higher than the umbrella-type tool magazine.

[0019] Dual-bearing guide transmission system: The bottom of the slider uses a deep groove ball bearing to contact the inner side of the guide rail, and the top uses a roller bearing to mesh with the transmission wheel, forming a "surface contact + point meshing" composite transmission, eliminating chain link gaps, and controlling the repeatability accuracy to ±0.03mm, which is 80% higher than chain drive.

[0020] Overload Protection Tool Holder: The tool holder incorporates a disc spring assembly that automatically triggers overload protection when the cutting force exceeds 1.5 times the rated value. The tool holder retracts 2mm and sends a stop signal, ensuring 100% tool protection success rate and preventing damage to expensive tools and the spindle. This invention effectively solves the core problems of existing tool magazines in terms of storage, positioning, and reliability through structural innovation and deep integration of servo control technology, providing key technical support for multi-process automated machining on compact machine tools. Attached Figure Description

[0021] Figure 1 Machine tool tool assembly structure diagram;

[0022] Figure 2 Drive principle structure diagram.

[0023] in:

[0024] Slider and tool holder mounting block;

[0025] guide;

[0026] link;

[0027] HSK A50 tool holder and clip;

[0028] Drive wheel;

[0029] Tool holder mounting block;

[0030] CF6 roller bearing;

[0031] slider;

[0032] padding blocks;

[0033] Deep groove ball bearing 6001. Detailed Implementation

[0034] Example

[0035] Servo-driven chain tool magazine example

[0036] I. Basic Implementation Examples

[0037] 1.1 Structural Composition and Assembly

[0038] The core structure of the servo chain tool magazine is shown in Figure 1. The base 13 is made of HT300 cast iron and machined after three aging treatments. Its top surface flatness is 0.003mm / m, and it is used to install the annular guide rail 2. The guide rail 2 is made of GCr15 bearing steel and its surface is hardened to HRC60. The cross-section is a T-slot structure (bottom width 40mm, top width 25mm). It is fixed to the edge of the base 13 with hexagonal socket head cap screws to form an annular track with a radius R=150mm.

[0039] Twelve sliders 8 are evenly distributed along the centerline of guide rail 2, and adjacent sliders 8 are hinged together by connecting rods 3. Connecting rods 3 are made of 40Cr steel, heat-treated to HB220-250, and have φ8mm pin holes machined at both ends. They form a rotating pair with the pins (made of 45 steel, hard chrome plated) on the side of sliders 8, with a rotation clearance controlled between 0.01-0.02mm. Deep groove ball bearings 6001 10 are installed on both sides of the bottom of sliders 8. The outer ring of the bearing contacts the vertical surface of the T-slot on the inner side of guide rail 2, with a contact length of 12mm, ensuring radial positioning accuracy.

[0040] The transmission system is installed at the lower left corner of the base 13: the RV40E reducer 12 and the servo motor are fixed on the motor mounting plate, and the 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, the module m=2, and the tooth surface is carburized and quenched to HRC58. It meshes with the CF6 roller bearing 7 on the top of the slider 8. The outer ring diameter 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.

[0041] 1.2 Workflow

[0042] When the CNC system issues a tool change command, the servo motor 13 calculates the number of rotations based on the target tool number. For example, from tool number 1 to tool number 10, the transmission wheel 5 needs to rotate (10-1) / 36 = 0.25 times. The servo motor 13 precisely controls the rotation angle through encoder feedback. When the transmission 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. 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 is ≤ 0.5 N·m.

[0043] When the target tool moves with the slider 8 to the tool change point (directly above the guide rail), the servo motor 13 stops, the machine tool spindle descends, and the tool drawer mechanism at its front end engages with the HSK A50 interface of the tool holder 4, clamping the tool through the hydraulic system. After the tool change is completed, the servo motor 13 rotates in the reverse direction, returning the used tool to its original position in the tool magazine.

[0044] Example

[0045] Overload protection tool clip embodiment

[0046] 2.1 Tool clip structure design

[0047] The overload protection tool holder 6 is installed on the side of the slider 8, and its structure is shown in Figure 2. The main body of the tool holder is made of 42CrMo steel, heat-treated to HB280-320. A φ50mm tool holder mounting hole is opened inside. A disc spring assembly (10 stacked 60Si2Mn spring plates with specifications of Φ30×Φ15×2mm) is installed at the bottom of the hole. The preload is set to 500N via the adjusting nut at the top. When the HSK A50 tool holder of the tool holder 4 is inserted into the hole, the tail pull stud presses against the disc spring assembly, generating an axial preload. Simultaneously, the fit accuracy between the tool holder tapered surface and the inner hole of the tool holder is H7 / g6, ensuring a radial positioning accuracy ≤0.008mm.

[0048] 2.2 Overload Protection Principle

[0049] When the cutting tool encounters an abnormal load during machining (such as a cutting force exceeding 1.5 times the rated value), the axial force on the tool holder 4 exceeds the preload of the disc spring assembly. The tool holder will move backward by 2mm, triggering a proximity switch (not shown) mounted on the side of the tool holder 6. The proximity switch sends a signal to the CNC system, and the machine tool immediately stops and alarms to prevent damage to the tool or the machine tool. After the abnormality is cleared, the tool holder 4 automatically resets under the elastic force of the disc spring assembly, requiring no manual adjustment.

[0050] Example

[0051] Transmission accuracy optimization example

[0052] 3.1 Roller and drive wheel meshing design

[0053] The meshing relationship between the CF6 roller bearing 7 at the top of slider 8 and the transmission wheel 5 is as follows: The tooth profile of the transmission wheel 5 is 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 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 approximately 26.18 mm (π × 2R × 10° / 360° = π × 2 × 150 × 1 / 36). The distance it moves on the straight path is equal to 1 / 12 of the center distance between adjacent sliders 8 (2πR / 12 = 78.54 mm). The calculated error is only 0.002 mm, ensuring a repeatability accuracy of ≤ ±0.03 mm.

[0054] 3.2 Comparative Experiment of Bearing Guiding System

[0055] To verify the superior guiding performance of the deep groove ball bearing 10, a comparative experiment was designed as follows:

[0056] Experimental group: The deep groove ball bearing 6001 10 of this embodiment is used. The surface roughness of the inner side of the guide rail 2 is Ra=0.4μm. The lubrication method is lithium-based grease lubrication (replenished once every 50 hours of operation).

[0057] Control group: Traditional chain drive (chain pitch p=25.4mm, roller diameter φ15.88mm), with the same guide rail structure.

[0058] Test conditions: 1000 consecutive tool change cycles from tool #1 to tool #12 were performed. The positioning error was measured using a laser interferometer (Renishaw XL-80). The results are shown in the table below:

[0059]

[0060] Data shows that the deep groove ball bearing 10 guide transmission method improves positioning accuracy by more than 80% and reduces standard deviation by 84.4% compared with chain transmission, proving that the technical effect of "higher repeatability positioning accuracy" as described in claim 8 is significant.

[0061] Example

[0062] Materials and Process Examples

[0063] 4.1 Guide rail materials and heat treatment

[0064] The GCr15 bearing steel billet of guide rail 2 is forged and then subjected to the following heat treatment process:

[0065] Spheroidizing annealing: Heat to 790℃ and hold for 2 hours, then cool in the furnace to 700℃, and then air cool to room temperature to obtain a uniform spherical pearlite structure with a hardness of HB180-200, which is easy to machine.

[0066] Quenching: Heat to 840℃ and hold for 30 minutes, then oil cool to room temperature to obtain martensitic structure with a hardness of HRC62-64.

[0067] Low-temperature tempering: Hold at 160℃ for 2 hours, then air cool to room temperature to eliminate quenching stress, stabilize dimensions, and achieve a final hardness of HRC60-62.

[0068] The T-slot of guide rail 2 is machined using a form milling cutter with a milling speed of v=30m / min, a feed rate of f=0.05mm / r, and a surface roughness Ra=0.8μm and a straightness error ≤0.005mm / 100mm after machining.

[0069] 4.2 Slider Surface Treatment

[0070] Slider 8 is made of 7075-T6 aluminum alloy, and its surface hard anodizing process parameters are as follows:

[0071] Electrolyte: 15% sulfuric acid solution, temperature 18-20℃

[0072] Current density: 1.5 A / dm², processing time: 40 minutes

[0073] Sealing treatment: Soak in 95℃ deionized water for 30 minutes

[0074] The oxide film is 25μm thick, with a surface hardness of HV500-550. Its corrosion resistance is tested by the neutral salt spray test (NSS), and no corrosion spots are observed after 72 hours, meeting the requirements for use in harsh working environments of machine tools.

[0075] V. Extended Embodiments (corresponding to claims 5 and 7)

[0076] 5.1 Servo Motor Control Strategy

[0077] Servo motor 13 adopts position control mode, and the control algorithm is PID + feedforward compensation. The position loop gain Kp = 2000 rad / s, the speed loop gain Kv = 1500 rad / s, and the integral time Ti = 0.01s. When the transmission wheel 5 approaches the target position, servo motor 13 automatically switches to low-speed operation (speed ≤ 5 rpm) and performs micro-step adjustment through the encoder (24-bit resolution, 16,777,216 pulses per revolution) to ensure that the impact speed during positioning is ≤ 0.05 m / s.

[0078] VI. Fault Diagnosis and Maintenance

[0079] 6.1 Troubleshooting

[0080]

[0081] 6.2 Maintenance Cycle

[0082] Daily: Check the surface cleanliness of guide rail 2, and remove iron filings and oil stains.

[0083] Weekly: Measure the moving resistance of slider 8. The normal range should be 5-10N. If it exceeds this range, check the bearing wear.

[0084] Monthly: Calibrate the servo motor and encoder zero point to ensure positioning accuracy.

[0085] VII. Summary of Technical Effects of the Examples

[0086]

Claims

1. An intelligent CNC machine tool with a servo chain tool magazine, comprising a base (13), characterized in that: The base (13) is provided with a guide rail (2) surrounding the edge. A slider (8) is distributed vertically along the center line of the guide rail (2). The slider (8) moves around the center line of the guide rail (2). The two sides of the slider (8) are movably connected by a connecting rod (3) to form a transmission chain. Bearings (10) are vertically arranged on both sides of the bottom end of the slider (8). The bearings (10) are located inside the guide rail (2) and contact the inside of the guide rail (2) to realize the contact transmission between the slider (8) and the guide rail (2).

2. The intelligent CNC machine tool with a servo chain tool magazine according to claim 1, characterized in that: The slider (8) has an overload protection blade clip (6) arranged laterally on its side. The overload protection blade clip (6) is driven in the same direction as the slider (8), and a blade holder (4) is vertically mounted inside the overload protection blade clip (6).

3. The intelligent CNC machine tool with a servo chain tool magazine according to claim 1, characterized in that: A motor mounting plate is provided at the bottom left corner of the base (13), and the motor mounting plate is connected to a reducer (12) and a motor. A transmission wheel (5) is provided horizontally at the top left corner of the base (13).

4. The intelligent CNC machine tool with a servo chain tool magazine according to claim 3, characterized in that: The slider (8) is vertically provided with a roller (7), the roller (7) is located at the top of the slider (8), and the roller (7) meshes with the transmission wheel (5).

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