An assembly process method for concentricity between a main shaft and a tool holder of a die-bushing machine

Abstract

This invention discloses an assembly process method for ensuring the concentricity of the spindle and tool holder of a Swiss-type lathe. The method includes: installing a mandrel in the spindle taper hole under thermally stable conditions and detecting its radial runout accuracy; installing and initially fixing the tool holder to the machine body; collecting runout data from multiple points on the tool holder end face using a measurement system; generating compensation amounts for each adjusting bolt based on the runout dataset; leveling the tool holder to a first preset threshold according to the compensation amount set and then locking it; installing a boring tool system to the positioning interface of the mandrel; driving the spindle to rotate the tool holder; and performing a one-time boring operation on the tool holder inner hole according to preset cutting parameters to form a target inner hole coaxial with the spindle axis. This method avoids the time loss and error accumulation caused by traditional processes that rely on disassembly, scraping, and repeated correction. It not only allows the concentricity of the tool holder inner hole to be directly closed to the spindle reference through machining, but also ensures the stability and repeatability of concentricity accuracy, significantly improving assembly efficiency and machining quality.

Description

Technical Field

[0001] This invention relates to the field of tool holder assembly, and more particularly to an assembly process method for ensuring concentricity between the spindle and the tool holder of a Swiss-type lathe. Background Technology

[0002] In the field of CNC machine tools, especially in Swiss-type lathes used for high-precision machining, the concentricity assembly accuracy between the spindle and the tool post directly determines the cutting accuracy and surface quality of the workpiece. Swiss-type lathes, due to their long-stroke spindle movement and fixed cutting tool structure, are widely used in the mass production of medical devices, automotive parts, and precision electronic components. With the industry's increasing demands for dimensional accuracy and machining efficiency for micro-parts, how to quickly and reliably achieve concentricity correction between the spindle and the tool post during assembly has become a key technical issue in machine tool manufacturing and assembly.

[0003] Existing assembly processes generally employ a "leveling, scraping, and re-measurement" approach. This involves first using a dial indicator to calibrate the tool holder end face to within a small range of perpendicularity to the spindle axis, then scraping and correcting the tool holder mounting surface, and repeatedly disassembling and reassembling to ensure concentricity meets requirements. However, this method suffers from cumbersome procedures, long processing times, and high reliance on the experience of assembly workers. Especially when concentricity fails to meet the standard on the first attempt, repeated disassembly and scraping are often necessary, leading to low efficiency and the introduction of new errors, making it difficult to consistently guarantee final accuracy. Therefore, existing technologies present technical challenges in terms of assembly efficiency and concentricity stability. Summary of the Invention

[0004] The purpose of this invention is to provide an assembly process method for ensuring the concentricity of the spindle and tool holder of a Swiss-type lathe, so as to solve the above-mentioned technical problems.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] An assembly process for ensuring concentricity between the spindle and tool post of a Swiss-type lathe includes the following steps:

[0007] S1. Under the thermally stable state of the machine tool, a mandrel is installed in the spindle taper hole and its radial runout accuracy is tested. At the same time, the tool tip size of the boring tool system is preset and verified in the offline state.

[0008] S2, Install the tool holder to the machine tool body and fix it initially. Collect runout data of multiple points on the end face of the tool holder through the measurement system. Calculate the compensation amount of each adjusting bolt based on the runout dataset. Adjust the tool holder to the first preset threshold according to the compensation amount set and then complete the locking.

[0009] S3, the boring tool system is installed to the positioning interface of the mandrel, and the spindle drives it to rotate. According to the preset cutting parameters, the inner hole of the tool holder is boringed in one go to form a target inner hole coaxial with the spindle axis.

[0010] Optionally, step S3 may be followed by:

[0011] S4. After machining by the boring tool system, a standard calibration body is installed at the same station. The concentricity and dimensional accuracy data of the newly machined inner hole are collected by the measurement system, and the accuracy data is compared with the accuracy standard to generate an assembly quality report.

[0012] S5, remove the mandrel and the standard calibration body, clean the assembly mating surface, and then install the tools required for production to enter the processing state.

[0013] Optionally, step S1 specifically includes:

[0014] S11, start the Swiss Army machine spindle to the preset balance speed for idle operation, monitor the temperature change rate of the spindle nose end through the infrared temperature measuring device, and determine that the whole machine has entered thermal steady state when the temperature change rate is continuously lower than the set threshold. Then, clean and prevent rust on the spindle end face, taper hole and tool holder mating surface.

[0015] S12, gently push the mandrel into the cleaned spindle taper hole, apply axial tension with a constant torque hydraulic nut according to the preset locking curve to complete stress-free installation, and then use the first lever gauge to preliminarily verify the approximate value of the mandrel proximal end runout;

[0016] S13, drive the spindle to rotate at low speed, and simultaneously collect radial runout data of the far end and near end of the spindle around one revolution through two displacement sensors arranged in mutually perpendicular directions, and generate a radial runout accuracy mapping dataset of the spindle-spindle system;

[0017] S14. In offline mode, the boring tool system is clamped in a dedicated tool setter. Based on the radial runout accuracy mapping dataset and the target size of the tool holder inner hole, the radial compensation amount of the insert is calculated and set, and the cutting parameters are preloaded to the machine tool CNC system.

[0018] Optionally, step S2 specifically includes:

[0019] S21. Use a special lifting tool to smoothly move the tool post to the machine tool body mounting base, and use constant torque bolts to pre-tighten the tool post in a diagonal sequence;

[0020] S22, the electronic probe is installed on the spindle mandrel and the spindle is driven to rotate at a low constant speed. The electronic probe continuously collects the runout timing data of the entire end face area using at least four evenly distributed measurement circles preset on the tool holder end face as the path.

[0021] S23, the collected time-series fluctuation data is filtered and transformed to generate a three-dimensional point cloud model of the tool holder end face. By fitting the three-dimensional point cloud model with the ideal plane using the least squares method, the current overall flatness error and tilt vector of the end face are calculated.

[0022] S24. Based on the tilt vector, the distribution coordinates of the adjusting bolts, and the pitch parameters, the theoretical axial displacement required for each adjusting bolt is calculated in reverse using a spatial geometric solution model to converge the end face flatness error to within ≤0.2mm, and then converted into a specific set of compensation amounts for rotation angles.

[0023] Optionally, after step S24, the method further includes:

[0024] S25, according to the compensation set displayed on the machine tool CNC system interface, the corresponding adjustment bolts are finely adjusted in a specified order. After each bolt adjustment is completed, the machine tool CNC system updates the remaining adjustment amount in real time and guides the operation until the end face runout measured value reaches the first preset threshold.

[0025] S26, after confirming that the position and posture meet the requirements, adopts a torque-angle composite control strategy to tighten all fixing bolts according to the preset locking torque and sequence.

[0026] Optionally, step S3 specifically includes:

[0027] S31, the boring tool system that has been pre-set offline is assembled with the corresponding interface of the spindle mandrel through its taper shank or flange interface, and the connecting parts are locked according to the preset locking curve and sequence using a torque wrench, and the assembly stress is monitored by micro-strain gauges integrated at the interface.

[0028] S32, retrieve a cutting parameter package from the machine tool CNC system parameter library that matches the current tool holder material and target hole diameter. The cutting parameters include preset logic for spindle speed, feed rate, depth of cut and coolant spray mode, and are then finely adjusted by the machine tool CNC system according to the current spindle load power and thermal expansion compensation amount before being loaded into the machining program.

[0029] S33 drives the spindle from low speed to target speed for frequency sweeping without the tool contacting the workpiece. It collects no-load vibration data through a vibration acceleration sensor mounted on the tool holder and performs spectrum analysis. If an abnormal peak occurs in a specific frequency band, it automatically adjusts the vibration damping speed before resuming machining.

[0030] Optionally, after S33, the following may also be included:

[0031] S34, start the machining program, drive the spindle and feed axis to move in coordination according to the predetermined parameters, so that the rotating boring tool can complete the one-time boring of the tool holder inner hole. During this process, the machine tool CNC system monitors the spindle current, axial force and vibration data in real time, and compares them with the theoretical load curve to realize closed-loop monitoring of process stability.

[0032] S35. After boring is completed, the spindle remains stationary. A non-contact displacement sensor installed on the machine tool is used to quickly scan the roundness profile of the newly machined inner hole. The profile data is compared with the theoretical circle to calculate the difference. It is determined whether the difference is better than the second preset threshold. If so, the machining is completed; otherwise, the compensation reboring program is triggered.

[0033] Optionally, step S4 specifically includes:

[0034] S41, a standard calibration bar whose temperature has been pre-stabilized to the same range as the machine tool spindle is used as a reference transfer body, gently pushed into and locked into the positioning interface of the spindle core, and left to stand for a preset time to allow the entire measurement system to reach thermal equilibrium.

[0035] S42 drives the spindle to rotate at a low and uniform speed. Through the displacement sensor fixed on the machine tool body, the radial runout data of the standard calibration bar on the first, middle and last cross sections of the newly machined inner hole are collected synchronously.

[0036] S43. Input the circumferential and radial runout data of the three cross sections into the algorithm model, fit the theoretical center axis of the inner hole by the least squares method, calculate the maximum radial offset between the theoretical center axis and the main shaft rotation axis on each cross section, and obtain the concentricity error value.

[0037] Optionally, after S43, the following may also be included:

[0038] S44. Using a temperature-calibrated pneumatic-electric meter, insert its probe into multiple axial positions of the target inner hole, collect inner diameter data under constant measurement pressure, and compensate for the measurement results based on the real-time temperature of the material to calculate the actual hole diameter value.

[0039] S45, compare the concentricity error value with the actual aperture value, along with the preset form and position tolerance and dimensional tolerance thresholds, and automatically fill the comparison results, the collected original data curves and the judgment conclusions into the standard template to generate a structured assembly quality report and upload it to the database.

[0040] Compared with the prior art, the present invention has the following advantages: Under the condition that the machine tool is in a thermally stable state, firstly, the mandrel is installed in the spindle taper hole and its radial runout accuracy is tested. At the same time, the tool tip size of the boring tool system is preset and verified offline. Then, the tool holder is installed on the machine tool body and initially fixed. The runout data of multiple points on the end face of the tool holder is collected by the measurement system, and the compensation amount of each adjusting bolt is generated based on the runout data. The tool holder is then leveled to the preset threshold and locked. After that, the boring tool system is installed on the positioning interface of the mandrel and driven by the spindle. The tool holder is rotated and a one-time boring operation is performed on the inner hole of the tool holder according to the preset cutting parameters, so that the inner hole formed is coaxial with the spindle axis. This method positions the boring tool system with the spindle mandrel as the reference and uses the spindle to drive the tool to perform one-time boring of the inner hole of the tool holder. It can avoid the time loss and error accumulation caused by disassembly, scraping and repeated correction in traditional processes. It not only makes the concentricity of the inner hole of the tool holder directly close to the spindle reference through the machining behavior, but also ensures the stability and repeatability of the concentricity accuracy, which greatly improves the assembly efficiency and machining quality. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] The structures, proportions, sizes, etc., shown in the accompanying drawings of this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed in the specification, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0043] Figure 1 This is one of the flowcharts illustrating the assembly process method in this embodiment;

[0044] Figure 2 This is the second schematic diagram of the assembly process method in this embodiment;

[0045] Figure 3 This is a schematic diagram of the equipment used in the actual assembly process of the spindle and tool holder in the assembly method of this embodiment. Detailed Implementation

[0046] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0047] In the description of this invention, it should be understood that the terms "upper," "lower," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to the other component or there may be a component positioned centrally in the connection.

[0048] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0049] Combination Figures 1 to 3 As shown, where Figure 3 This is a schematic diagram of the equipment during the actual assembly process of the spindle and tool holder in this solution. This embodiment of the invention provides an assembly process method for ensuring the concentricity of the spindle and tool holder of a Swiss-type lathe, including the following steps:

[0050] S1. Under the thermally stable state of the machine tool, a spindle 20 is installed in the taper hole of the spindle 10 and its radial runout accuracy is tested. At the same time, the tool tip size of the boring tool system 30 is preset and verified in the offline state.

[0051] It should be noted that the core purpose of this step is to establish an unquestionable machining benchmark. First, "machine tool thermal stability" is a prerequisite for precision machining, aiming to eliminate spindle 10 axis drift caused by thermal deformation of the machine tool. Installing the "mandrel 20" materializes the invisible internal rotation axis of the spindle 10 into a tangible and measurable physical benchmark. Detecting its radial runout accuracy verifies the accuracy of the spindle 10 itself and the success of the installation, ensuring the reliability of this benchmark. Simultaneously, the "offline pre-adjustment boring tool system 30" is crucial, separating the time-consuming tool loading, tool setting, and dimensional setting work from the main machining time of the machine tool and completing it on a dedicated alignment instrument. This not only ensures the accuracy of the tool itself but also greatly reduces the time the machine tool spindle 10 is occupied, improving overall assembly efficiency.

[0052] S2, Install the tool holder 40 to the machine tool body and fix it initially. Collect runout data of more than 60 points on the end face of the tool holder through the measurement system. Calculate the compensation amount of each adjusting bolt based on the runout dataset. Adjust the tool holder 40 to the preset threshold according to the compensation amount set and then lock it.

[0053] It should be noted that the extremely high surface perpendicularity requirement (≤0.01mm), which must be achieved through scraping in traditional processes, has been significantly relaxed to a threshold (≤0.2mm) that can be quickly achieved through simple position adjustments. By "collecting runout data from more than 60 points on the tool holder end face using a measurement system," a quantitative dataset describing the current pose of the tool holder 40 was obtained. Subsequently, "compensation amounts for each adjusting bolt were generated based on the runout dataset." This process introduces a data-driven decision-making method. The operator only needs to make fine adjustments based on the generated "compensation amount set" to efficiently level the tool holder 40 within the preset range and complete the locking.

[0054] S3, the boring tool system 30 is installed to the positioning interface of the spindle 20 and driven to rotate by the spindle 10. According to the preset cutting parameters, the inner hole of the tool holder 40 is boringed in one go to form the target inner hole 50 coaxial with the axis of the spindle 10.

[0055] It should be noted that step S3 is the core of the entire method, realizing a paradigm shift from "assembly and debugging" to "in-situ manufacturing." Installing the "boring tool system 30" onto the established "mandrel 20" datum means that the rotation center of the tool is highly coincident with the rotation axis of the spindle 10. Subsequently, the spindle 10 drives its rotation, acting as the "machine tool." "Performing a one-time boring operation on the inner hole of the tool holder 40 according to preset cutting parameters" directly uses the axis of the spindle 10 as a datum, constructing a completely new target inner hole 50 on the tool holder 40, naturally coaxial with the axis of the spindle 10. This process eliminates error propagation in intermediate stages, directly raising the assembly accuracy to the original accuracy level of the machine tool spindle 10. Essentially, it transforms the assembly challenge of "ensuring concentricity" into a simple machining problem of "machining a hole using its own datum," thereby fundamentally guaranteeing extremely high concentricity accuracy and high consistency of "≤0.005mm."

[0056] S4. After machining by the boring tool system 30, a standard calibration body is installed at the same station. The concentricity and dimensional accuracy data of the newly machined inner hole are collected by the measurement system, and the accuracy data is compared with the accuracy standard to generate an assembly quality report.

[0057] Installing the standard calibration body at the same work station avoids the errors caused by secondary clamping, ensures the unity of the inspection reference and the machining reference. Collecting the concentricity and dimensional accuracy data of the newly machined inner hole through the measurement system is a direct inspection of the machining result in step S3. Subsequently, comparing the accuracy data with the accuracy standard completes the objective determination of qualification or non - qualification; generating an assembly quality report provides a data traceability record, ensuring that the assembly quality of each piece of equipment leaving the factory is有据可查 (verifiable).

[0058] S5. Remove the mandrel 20 and the standard calibration body, clean the assembly joint surface, and then install the cutting tool required for production to enter the machining state.

[0059] After confirming that the assembly accuracy is qualified, "removing the mandrel 20 and the standard calibration body" is to clean the tooling fixtures used for assembly and debugging. "Cleaning the assembly joint surface" is a necessary operation to ensure the long - term maintenance of connection rigidity and accuracy. Finally, "installing the cutting tool required for production to enter the machining state" means that the equipment is ready and can be immediately put into production. This process is designed to be simple and efficient, minimizing the downtime of the equipment caused by assembly and debugging, and directly improving the utilization rate and production capacity of the equipment.

[0060] The working principle of the present invention is as follows: Under the condition that the machine tool is in a thermal steady state, first install the mandrel 20 in the taper hole of the spindle 10 and detect its radial run - out accuracy. At the same time, preset and calibrate the tip size of the boring tool system 30 in an offline state; then install the tool holder 40 onto the machine tool body and preliminarily fix it. Collect the run - out data of multiple points on the end face 60 of the tool holder through the measurement system, and calculate the compensation amount of each adjustment bolt based on this run - out data, so as to level the tool holder 40 to the preset threshold and then complete the locking; then install the boring tool system 30 onto the positioning interface of the mandrel 20, drive it to rotate by the spindle 10, and perform a one - time boring process on the inner hole of the tool holder 40 according to the preset cutting parameters, so that the formed inner hole is coaxial with the axis of the spindle 10; This method positions the boring tool system 30 based on the mandrel 20 of the spindle 10 and uses the spindle 10 to drive the tool to perform a one - time boring forming on the inner hole of the tool holder 40, which can avoid the time loss and error accumulation caused by disassembly, scraping and repeated calibration in the traditional process. Not only does the concentricity of the inner hole of the tool holder 40 directly close to the spindle 10 reference by the machining behavior, but also ensures the stability and repeatability of the concentric accuracy, greatly improving the assembly efficiency and machining quality.

[0061] In this embodiment, specifically, step S1 specifically includes:

[0062] S11, start the Swiss-type lathe spindle 10 to the preset balance speed for idle operation, monitor the temperature change rate of the nose end of the spindle 10 through an infrared temperature measuring device, and determine that the whole machine has entered thermal steady state when the temperature change rate is continuously lower than the set threshold. Then, clean and prevent rust on the end face of the spindle 10, the taper hole, and the mating surface of the tool holder 40.

[0063] It should be noted that as a precision machine tool, the Swiss-type lathe generates heat during operation, causing thermal deformation of its components such as the spindle 10 and guide rails, resulting in a drift in the axis position of the spindle 10. If assembly is performed in a cold state and the required precision is achieved, the precision will be lost due to thermal deformation once the machine reaches its operating temperature. The heating conditions under operating conditions were simulated by allowing the spindle 10 to idle at a preset equilibrium speed. Monitoring the temperature change rate at the nose of the spindle 10 using an infrared thermometer is a quantitative method for determining thermal steady state. When the rate of change remains below a threshold, it indicates that the heat generated and dissipated by the main heat sources of the machine tool has reached equilibrium, and the overall structure no longer experiences significant thermal deformation. The subsequent cleaning work is to ensure that the mounting surfaces of the subsequent reference tooling (mandrel 20) and tool post 40 are free of impurities and oil, preventing these minor factors from introducing assembly stress or positioning errors.

[0064] S12, gently push the mandrel 20 into the cleaned taper hole of the spindle 10, apply axial tension using a constant torque hydraulic nut according to a preset locking curve to complete stress-free installation, and then use the first lever gauge to preliminarily check the approximate value of the proximal runout of the mandrel 20.

[0065] The mandrel 20 is a physical extension of the internal rotation axis of the spindle 10, and its installation quality directly determines the accuracy of all subsequent operations. A constant torque hydraulic nut is used to apply axial tension according to a preset locking curve. By precisely controlling the magnitude and loading rate of the tension force, consistent locking force is ensured for each installation, avoiding stress differences caused by varying operator strength, thus achieving "stress-free installation." This is crucial for ensuring the repeatability of the mandrel 20's runout accuracy. The subsequent preliminary verification using a first lever gauge is a rapid process inspection. Its purpose is to immediately confirm that no major abnormalities occurred during the installation (such as the mandrel 20 not being in place or the presence of foreign objects). This is an efficient quality control point, preventing more complex subsequent operations from being performed based on errors.

[0066] S13 drives the spindle 10 to rotate at a low speed. Through two displacement sensors arranged in mutually perpendicular directions, the radial runout data of the far end and near end of the spindle 20 are collected synchronously to generate a radial runout accuracy mapping dataset of the spindle 20-spindle 10 system. The radial runout accuracy mapping dataset can reflect the runout characteristics of the spindle 10 and spindle 20 combination in dynamic rotation.

[0067] It should be noted that even if the mandrel 20 itself is manufactured with extremely high precision and installed correctly, its final radial runout is a comprehensive reflection of the rotational precision of the spindle 10, the precision of the taper hole, and the precision of the mandrel 20. Driving the spindle 10 to rotate at a low speed is to avoid interference from dynamic factors such as centrifugal force at high speeds.

[0068] Synchronous acquisition using two displacement sensors positioned perpendicularly to each other is to obtain the complete runout trajectory of the mandrel 20 in both the X and Y directions (i.e., a circular trajectory in a plane), which more accurately reflects the overall error than single-point measurement. Synchronous acquisition of radial runout data from both the distal and proximal ends allows for the calculation of the mandrel 20's tilt error, thus providing a comprehensive assessment of the reference system's condition. The generated radial runout accuracy mapping dataset contains not only the magnitude (numerical value) of the runout but also its phase (angle) information, providing crucial data support for precise tool pre-adjustment in the next step.

[0069] S14, In offline mode, the boring tool system 30 is clamped in a dedicated tool setter. Based on the radial runout accuracy mapping dataset and the target size of the inner hole of the tool holder 40, the radial compensation amount of the insert is calculated and set, and the cutting parameters are preloaded to the machine tool CNC system. In this way, the accuracy calibration of the tool system and the configuration of the cutting parameters can be completed before the actual machining, ensuring that the tool trajectory is consistent with the spindle 10 reference during boring, thereby improving the concentricity and dimensional accuracy of the inner hole machining of the tool holder 40.

[0070] It should be noted that in traditional online tool setting methods, the tool setting process consumes machine tool time and is subject to many environmental interference factors. This solution innovatively adopts the method of "clamping the boring tool system 30 in a dedicated tool setting device in an offline state". The dedicated tool setting device has a stable environment and high precision, and can independently, quickly and accurately complete the setting of the tool tip position without being affected by machine tool vibration and temperature changes. Through algorithms, the system can compensate for the inherent error of the spindle 10 system measured in step S13, so that the actual cutting trajectory of the tool tip is as close as possible to the ideal axis, thereby planning higher machining accuracy from the source. At the same time, "preloading cutting parameters to the machine tool CNC system" completes the production preparation, so that the machine tool can start machining immediately after receiving the tool, minimizing the spindle 10 waiting time and combining efficient offline pre-setting with in-situ machining.

[0071] In this embodiment, step S2 specifically includes:

[0072] S21. Using a special lifting tool, the tool holder 40 is smoothly moved to the machine tool body mounting base. The tool holder 40 is initially fixed by using constant torque bolts in a diagonal pre-tightening sequence to ensure uniform contact of the mating surfaces and no assembly stress distortion, so as to ensure that the tool holder 40 has a stable reference posture in the initial installation state.

[0073] As the final functional component to be machined and used, the initial installation quality of the tool holder 40 directly affects the efficiency and final accuracy of subsequent adjustments. Using specialized lifting tools is to prevent deformation or scratches on the precision mating surfaces of the tool holder 40 due to uneven force or collisions during lifting. Initial fixing is achieved using constant torque bolts in a diagonal pre-tightening sequence. This method ensures a uniform and stable fit between the tool holder 40 and the machine tool body mounting surface, preventing twisting or internal stress (i.e., "assembly stress distortion") caused by improper bolt tightening sequence or uneven torque.

[0074] S22, the electronic probe is installed on the spindle 20 of the main spindle 10, and the main spindle 10 is driven to rotate at a low constant speed. The electronic probe continuously collects the runout timing data of the entire end face area by taking at least four evenly distributed measurement circles preset on the tool holder end face 60 as the path. This process can perform comprehensive and dynamic detection of the end face flatness without disassembling the tool holder 40, thereby improving the coverage and accuracy of the measurement.

[0075] The scanning was performed using at least four pre-defined uniformly distributed measurement circles on the end face 60 of the tool holder as the path. Multiple sampling points were performed in both the radial and circumferential directions, which enabled continuous acquisition of the timing data of the entire end face's fluctuations. This resulted in a high-density data field covering the entire end face, providing a sufficient data foundation for the subsequent construction of an accurate 3D model of the end face and avoiding misjudgments caused by insufficient measurement data.

[0076] S23 filters and transforms the collected time-series fluctuation data to generate a three-dimensional point cloud model of the tool holder end face 60. By fitting the three-dimensional point cloud model with the ideal plane using the least squares method, the current overall flatness error and tilt vector of the end face are calculated; thus, the complex fluctuation data is transformed into intuitive geometric error information.

[0077] The acquired timing fluctuation data contains interference signals from machine tool vibration and measurement noise. Filtering can remove these interferences, preserving the true shape information. Coordinate transformation processing converts the probe-based data to the machine tool coordinate system, providing a unified reference. Generating a 3D point cloud model of the tool holder end face 60 involves reconstructing a series of discrete point data into a visual and computable digital 3D surface. Finally, by fitting the 3D point cloud model to an ideal plane using the least squares method, the ideal plane that best represents the overall tilt of the current end face is calculated. The deviation between the current end face and this ideal plane, i.e., the overall flatness error, and the specific tilt direction and angle of the end face in space, i.e., the tilt vector, are also accurately calculated.

[0078] S24, based on the tilt vector, the distribution coordinates of the adjusting bolts and the pitch parameters, uses a spatial geometric solution model to inversely calculate the theoretical axial displacement required for each adjusting bolt when the end face flatness error is converged to within ≤0.2mm, and converts it into a specific set of compensation amounts for rotation angles.

[0079] Based on the tilt vector calculated in the previous step (indicating the direction and magnitude of the correction required), combined with the distribution coordinates of the adjusting bolts (clarifying the direction of influence of each adjusting bolt on the end face pose in space) and their pitch parameters (determining the conversion relationship between bolt rotation angle and axial lifting amount), a spatial geometric solution model is constructed. This model can inversely solve for: how much theoretical axial displacement each adjusting bolt needs to move precisely to compensate for the calculated tilt error, and convert this displacement into a rotation angle easily executed by the operator. The final output set of compensation amounts is a set of adjustment instructions.

[0080] S25, based on the compensation set displayed on the machine tool CNC system interface, fine-tune the corresponding adjusting bolts in a specified order. After each bolt adjustment is completed, the machine tool CNC system updates the remaining adjustment amount in real time, guiding the operation until the actual value of end face runout reaches the first preset threshold.

[0081] This step is a human-machine interaction process that transforms digital adjustment commands into physical reality. Operators no longer need to guess based on experience or intuition; they only need to operate strictly according to the compensation set displayed on the machine tool's CNC system interface. The system guides adjustments in a specified sequence, avoiding mutual interference during the adjustment process. The system updates the remaining adjustment amount in real time after each bolt adjustment is completed, forming a dynamic and visual feedback loop. Setting the adjustment target to a "first preset threshold" of ≤0.2mm, rather than the traditional ≤0.01mm, makes rapid adjustment possible.

[0082] S26, after confirming that the position and posture meet the requirements, adopts a torque-angle composite control strategy to tighten all fixing bolts according to the preset locking torque and sequence.

[0083] It should be noted that the bolts are not completely locked during the adjustment phase. Once the orientation is confirmed to be correct, final tightening is required. Tightening by feel alone, with a large locking force, may slightly alter the already adjusted orientation. The "torque-angle composite control strategy" is an advanced bolt tightening method. It first applies an initial torque to ensure tight contact between the parts, then controls the bolt rotation at a precise angle, thereby accurately controlling the bolt elongation and the final clamping force. This ensures that all bolts are subjected to uniform force, following the "preset locking torque and sequence," minimizing the risk of introducing new stress due to improper tightening or causing the already adjusted tool holder 40 to "drift."

[0084] In this embodiment, step S3 specifically includes:

[0085] S31, the pre-set boring tool system 30 is assembled with the corresponding interface of the spindle 10 spindle 20 via its taper shank or flange interface. The connecting parts are tightened according to the preset locking curve and sequence using a torque wrench, and the assembly stress is monitored by micro-strain gauges integrated at the interface.

[0086] As the executing component, the boring tool system 30's connection quality with the spindle 10 and spindle 20 directly determines the accuracy of the tool tip's trajectory. The tool's initial coordinates have been set in a stable environment, ensuring basic dimensional accuracy. Using a torque wrench to tighten according to a preset tightening curve and sequence is crucial to ensuring consistency in each connection. A smooth loading curve avoids impacts, and a strict sequence ensures uniform force on the interface, preventing skewing.

[0087] By monitoring assembly stress using micro-strain gauges integrated at the interface, quantitative monitoring of the installation process is achieved. The purpose is not only to prevent overstress installation from damaging precision interfaces, but also to ensure the connection is within the optimal compressive stress range, thereby maintaining extremely high rigidity during high-speed rotation and avoiding machining vibrations and precision degradation caused by loose connections or slight displacement.

[0088] S32, retrieves a cutting parameter package from the machine tool CNC system parameter library that matches the current material of the tool holder 40 and the target hole diameter. The cutting parameters include the preset logic of the spindle speed 10, feed rate, depth of cut and coolant spray mode. The machine tool CNC system then fine-tunes the parameters according to the current load power and thermal expansion compensation of the spindle 10 before loading them into the machining program.

[0089] The selection of cutting parameters (spindle speed, feed rate, depth of cut) directly affects machining force, thermal deformation, and surface quality. "Calling a cutting parameter package from the parameter library that matches the current tool holder 40 material and target hole diameter" digitally encapsulates and reuses process experience. The system can "fine-tune based on the current load power of spindle 10 and the amount of thermal expansion compensation," demonstrating adaptive intelligence. For example, if the system detects that the spindle 10 power is lower than expected, it can slightly increase the feed rate to optimize efficiency; if the thermal expansion model shows that the spindle 10 has a slight extension, it can perform micron-level compensation on the Z-axis starting point. This dynamic optimization allows the machining process to adapt to the real-time state of the machine tool, thus stably outputting the preset machining quality under various conditions.

[0090] S33, without the tool contacting the workpiece, drives the spindle 10 to sweep the frequency from low speed to the target speed. The vibration acceleration sensor installed on the tool holder 40 collects the no-load vibration data and performs spectrum analysis. If an abnormal peak occurs in a specific frequency band, the vibration damping speed is automatically adjusted before entering the machining process.

[0091] This solution actively excites the entire rotating system by performing frequency sweeping operation "without the tool contacting the workpiece." "By collecting no-load vibration data and performing spectrum analysis using a vibration acceleration sensor mounted on the tool holder 40," it can accurately identify whether the entire system has inherent resonance points or vibration peaks caused by imbalances at specific speeds. If "abnormal peaks appear in a specific frequency band," the system "automatically adjusts the vibration damping speed," selecting a safe speed to avoid the resonance speed for machining. This step transforms the traditional "trial cutting - listening to the sound - judging by experience" process into a data-driven, predictable, and preventative advanced process method, fundamentally avoiding the risk of surface quality deterioration or even tool breakage due to chatter.

[0092] S34, start the machining program, drive the spindle 10 and the feed axis to move in coordination according to the predetermined parameters, so that the rotating boring tool can complete the one-time boring of the inner hole of the tool holder 40. During this process, the machine tool CNC system monitors the current, axial force and vibration data of the spindle 10 in real time, and compares them with the theoretical load curve to realize closed-loop monitoring of process stability.

[0093] When the machining program starts, the spindle 10 and the feed axis move in tandem according to optimized parameters to complete the boring process. During this process, "real-time monitoring of spindle 10 current, axial force, and vibration data" provides a comprehensive understanding of the machining status. Spindle 10 current indirectly reflects the cutting torque, axial force reflects the cutting load, and vibration data reflects process stability. Once abnormal data is detected, such as a sudden increase in load (which may indicate tool wear or chipping) or increased vibration (which may indicate chip entanglement), the system can issue an alarm or even execute a protective shutdown.

[0094] S35, after boring is completed, the spindle 10 remains stationary. The non-contact displacement sensor installed on the machine tool is used to quickly scan the roundness profile of the newly machined inner hole. The profile data is compared with the theoretical circle to calculate the difference. It is determined whether the difference is better than the second preset threshold. If so, the machining is completed; otherwise, the compensation re-boring program is triggered.

[0095] After boring, the spindle 10 remains stationary for measurement, ensuring 100% consistency between the measurement datum and the machining datum, and avoiding errors caused by moving parts. A non-contact displacement sensor is used for scanning, avoiding scratches on the machined surface that might occur with contact measurements. Rapid scanning of the inner hole's roundness and comparison with the theoretical circle quickly obtains key indicators representing machining accuracy (roundness indirectly reflects concentricity). The system automatically judges whether the difference is better than a second preset threshold: if it meets the threshold, the process ends with extremely high efficiency; if it does not meet the threshold, a compensation reboring program is immediately triggered, performing tool compensation based on the measured error and executing micro-remapping to correct the error. This step achieves a fully automated closed loop of "measurement-decision-compensation action".

[0096] In this embodiment, step S4 specifically includes:

[0097] S41, a standard calibration bar whose temperature has been pre-stabilized to the same range as that of the machine tool spindle 10 is used as a reference transfer body, gently pushed into and locked into the positioning interface of the spindle 20 of the spindle 10, and left to stand for a preset time to allow the entire measurement system to reach thermal equilibrium.

[0098] In precision measurement, components such as the machine tool spindle 10, standard calibration bar, and tool holder 40 have different coefficients of thermal expansion due to their different materials. If there is a temperature difference between the components, even a small temperature difference can lead to a significant deviation in the measurement results due to the effect of thermal expansion and contraction, and this deviation is uncertain.

[0099] This solution ensures that the reference transmission body and the main machine are in the same thermal state by pre-stabilizing the standard calibration bar to the same range as the machine tool spindle 10. Allowing it to stand for a preset time after installation allows the entire measurement chain (spindle 10 - mandrel 20 - calibration bar - tool holder 40) to fully reach thermal equilibrium and eliminates internal thermal stress flow.

[0100] S42 drives the spindle 10 to rotate at a low and uniform speed. Through the displacement sensor fixed on the machine tool body, it synchronously collects the radial runout data of the standard calibration bar on the first, middle and last cross sections of the newly machined inner hole.

[0101] This step aims to comprehensively collect raw data for evaluating concentricity. Traditional concentricity testing typically measures only one cross-section (often the borehole opening), which fails to accurately reflect the spatial orientation of the inner hole's axis across its entire depth and may miss bending or taper errors. This approach requires simultaneously collecting radial runout data of a standard calibration bar across the first, middle, and last cross-sections of the newly machined inner hole. This is equivalent to acquiring three coordinate points representing the center of each cross-section in space. This multi-cross-section, full-circumference sampling method provides sufficient and necessary data for the next step of accurately reconstructing the spatial axis of the inner hole.

[0102] S43, input the circumferential and radial runout data of the three cross sections into the algorithm model, fit the theoretical center axis of the inner hole by the least squares method, calculate the maximum radial offset of the theoretical center axis and the rotation axis of the main shaft 10 on each cross section, and solve for the concentricity error value.

[0103] This scheme employs an algorithm that fits the theoretical central axis of the inner hole using the least squares method. This algorithm can calculate an ideal axis that best represents the orientation of the entire inner hole space based on data from three cross sections. Subsequently, the maximum radial offset between this theoretical central axis and the rotation axis of the main shaft 10 on each cross section is calculated. The resulting concentricity error value is an evaluation index that conforms to the ISO standard definition.

[0104] S44. Using a temperature-calibrated pneumatic-electric meter, insert its probe into multiple axial positions of the target inner hole 50, collect inner diameter data under constant measurement pressure, and compensate for the measurement results based on the real-time temperature of the material to calculate the actual hole diameter value.

[0105] A temperature-calibrated gas-electric meter is used because of its high measurement accuracy, fast response speed, and non-contact measurement (an air film exists between the probe and the hole wall), which will not scratch the finished surface. By collecting data at multiple axial positions, the cylindricity (whether it is bulging or saddle-shaped) and dimensional consistency of the hole can be comprehensively evaluated. Due to the thermal expansion and contraction characteristics of metallic materials, the dimensions of the same object measured at different temperatures will be different. This solution uses real-time temperature measurement and compensation calculations to uniformly convert the measured values ​​to the results at a standard temperature (e.g., 20°C), thereby obtaining the true actual hole diameter value and ensuring the accuracy of dimensional determination.

[0106] S45 compares the concentricity error value with the actual aperture value, along with the preset geometric tolerance and dimensional tolerance thresholds, and automatically fills the comparison results, the collected original data curves, and the judgment conclusions into the standard template to generate a structured assembly quality report and upload it to the database.

[0107] The comparison results, collected raw data curves, and judgment conclusions are automatically populated into a standard template to generate a structured assembly quality report. This report includes judgment conclusions, detailed data, and even raw waveforms, and is finally uploaded to the database, enabling quality traceability throughout the entire lifecycle.

[0108] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for assembling the spindle and tool post of a Swiss-type lathe to ensure concentricity, characterized in that, Includes the following steps: S1. Under the thermally stable state of the machine tool, a mandrel is installed in the spindle taper hole and its radial runout accuracy is tested. At the same time, the tool tip size of the boring tool system is preset and verified in the offline state. S2, Install the tool holder to the machine tool body and fix it initially. Collect runout data of multiple points on the end face of the tool holder through the measurement system. Calculate the compensation amount of each adjusting bolt based on the runout dataset. Adjust the tool holder to the first preset threshold according to the compensation amount set and then complete the locking. S3, the boring tool system is installed to the positioning interface of the mandrel, and the spindle drives it to rotate. According to the preset cutting parameters, the inner hole of the tool holder is boringed in one go to form a target inner hole coaxial with the spindle axis.

2. The assembly process method for ensuring concentricity between the spindle and tool post of a Swiss-type lathe according to claim 1, characterized in that, The step S3 is followed by: S4. After machining by the boring tool system, a standard calibration body is installed at the same station. The concentricity and dimensional accuracy data of the newly machined inner hole are collected by the measurement system, and the accuracy data is compared with the accuracy standard to generate an assembly quality report. S5, remove the mandrel and the standard calibration body, clean the assembly mating surface, and then install the tools required for production to enter the processing state.

3. The assembly process method for ensuring concentricity between the spindle and tool post of a Swiss-type lathe according to claim 1, characterized in that, Step S1 specifically includes: S11, start the Swiss Army machine spindle to the preset balance speed for idle operation, monitor the temperature change rate of the spindle nose end through the infrared temperature measuring device, and determine that the whole machine has entered thermal steady state when the temperature change rate is continuously lower than the set threshold. Then, clean and prevent rust on the spindle end face, taper hole and tool holder mating surface. S12, gently push the mandrel into the cleaned spindle taper hole, apply axial tension with a constant torque hydraulic nut according to the preset locking curve to complete stress-free installation, and then use the first lever gauge to preliminarily verify the approximate value of the mandrel proximal end runout; S13, drive the spindle to rotate at low speed, and simultaneously collect radial runout data of the far end and near end of the spindle around one revolution through two displacement sensors arranged in mutually perpendicular directions, and generate a radial runout accuracy mapping dataset of the spindle-spindle system; S14. In offline mode, the boring tool system is clamped in a dedicated tool setter. Based on the radial runout accuracy mapping dataset and the target size of the tool holder inner hole, the radial compensation amount of the insert is calculated and set, and the cutting parameters are preloaded to the machine tool CNC system.

4. The assembly process method for ensuring concentricity between the spindle and tool post of a Swiss-type lathe according to claim 1, characterized in that, Step S2 specifically includes: S21. Use a special lifting tool to smoothly move the tool holder to the machine tool body mounting base, and use constant torque bolts to pre-tighten the tool holder in a diagonal pre-tightening sequence; S22, the electronic probe is installed on the spindle mandrel and the spindle is driven to rotate at a low constant speed. The electronic probe continuously collects the runout timing data of the entire end face area using at least four evenly distributed measurement circles preset on the tool holder end face as the path. S23, the collected jump time data is filtered and coordinate transformed to generate a three-dimensional point cloud model of the tool holder end face. By fitting the three-dimensional point cloud model with the ideal plane using the least squares method, the current overall flatness error and tilt vector of the end face are calculated. S24. Based on the tilt vector, the distribution coordinates of the adjusting bolts, and the pitch parameters, the theoretical axial displacement required for each adjusting bolt is calculated in reverse using a spatial geometric solution model to converge the end face flatness error to within ≤0.2mm, and then converted into a specific set of compensation amounts for rotation angles.

5. The assembly process method for ensuring concentricity between the spindle and tool post of a Swiss-type lathe according to claim 4, characterized in that, Following step S24, the following is also included: S25, according to the compensation set displayed on the machine tool CNC system interface, the corresponding adjusting bolts are finely adjusted in a specified order. After each adjusting bolt is adjusted, the machine tool CNC system updates the remaining adjustment amount in real time and guides the operation until the end face runout measured value reaches the first preset threshold. S26 After confirming that the position and posture meet the requirements, a torque-angle composite control strategy is adopted to tighten all adjusting bolts according to the preset locking torque and sequence.

6. The assembly process method for ensuring concentricity between the spindle and tool post of a Swiss-type lathe according to claim 1, characterized in that, Step S3 specifically includes: S31, the boring tool system that has been pre-set offline is assembled with the corresponding interface of the spindle mandrel through its taper shank or flange interface, and the connecting parts are locked according to the preset locking curve and sequence using a torque wrench, and the assembly stress is monitored by micro-strain gauges integrated at the interface. S32, retrieve a cutting parameter package from the machine tool CNC system parameter library that matches the current tool holder material and target hole diameter. The cutting parameters include preset logic for spindle speed, feed rate, depth of cut and coolant spray mode, and are then finely adjusted by the machine tool CNC system according to the current spindle load power and thermal expansion compensation amount before being loaded into the machining program. S33 drives the spindle from low speed to target speed for frequency sweeping without the tool contacting the workpiece. It collects no-load vibration data through a vibration acceleration sensor mounted on the tool holder and performs spectrum analysis. If an abnormal peak occurs in a specific frequency band, it automatically adjusts the vibration damping speed before resuming machining.

7. The assembly process method for ensuring concentricity between the spindle and tool post of a Swiss-type lathe according to claim 6, characterized in that, Following S33, the following is also included: S34, start the machining program, drive the spindle and feed axis to move in coordination according to the predetermined parameters, so that the rotating boring tool can complete the one-time boring of the tool holder inner hole. During this process, the machine tool CNC system monitors the spindle current, axial force and vibration data in real time, and compares them with the theoretical load curve to realize closed-loop monitoring of process stability. S35. After boring is completed, the spindle remains stationary. A non-contact displacement sensor installed on the machine tool is used to quickly scan the roundness profile of the newly machined inner hole. The profile data is compared with the theoretical circle to calculate the difference. It is determined whether the difference is better than the second preset threshold. If so, the machining is completed; otherwise, the compensation reboring program is triggered.

8. The assembly process method for ensuring concentricity between the spindle and tool post of a Swiss-type lathe according to claim 2, characterized in that, Step S4 specifically includes: S41, a standard calibration bar whose temperature has been pre-stabilized to the same range as the machine tool spindle is used as a reference transfer body, gently pushed into and locked into the positioning interface of the spindle core, and left to stand for a preset time to allow the entire measurement system to reach thermal equilibrium. S42 drives the spindle to rotate at a low and uniform speed. Through the displacement sensor fixed on the machine tool body, the radial runout data of the standard calibration bar on the first, middle and last cross sections of the newly machined inner hole are collected synchronously. S43. Input the circumferential and radial runout data of the three cross sections into the algorithm model, fit the theoretical center axis of the inner hole by the least squares method, calculate the maximum radial offset between the theoretical center axis and the main shaft rotation axis on each cross section, and obtain the concentricity error value.

9. The assembly process method for ensuring concentricity between the spindle and tool post of a Swiss-type lathe according to claim 8, characterized in that, Following S43, the following is also included: S44. Using a temperature-calibrated pneumatic-electric meter, insert its probe into multiple axial positions of the target inner hole, collect inner diameter data under constant measurement pressure, and compensate for the measurement results based on the real-time temperature of the material to calculate the actual hole diameter value. S45, compare the concentricity error value with the actual aperture value, along with the preset form and position tolerance and dimensional tolerance thresholds, and automatically fill the comparison results, the collected original data curves and the judgment conclusions into the standard template to generate a structured assembly quality report and upload it to the database.

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