Flexible precision grinding system and method of machining center based on fixed reference

Abstract

The invention discloses a flexible precision grinding system and method of a machining center based on a fixed datum, and belongs to the field of combined machining of numerical control machine tools. The diamond dressing tool is innovatively arranged as a fixed geometric reference on the workbench, absolute coordinates of the diamond dressing tool are determined through precise calibration, a real-time closed loop of online dressing, automatic compensation and precise grinding is established, and therefore the stable and high-precision grinding capacity is achieved on the machining center. Based on the core unit, a multi-workpiece clamping function and a numerical control scheduling function are further integrated, various different parts are supported to be clamped on a workbench, a system automatically schedules a grinding wheel to sequentially complete closed-loop grinding circulation of the parts, and therefore continuous and automatic machining of various technologies such as an inner hole, an outer circle and a complex profile on single equipment is achieved. The precise grinding bottleneck of a machining center is overcome, a new mode supporting multi-variety small-batch flexible production is created, and the precise grinding device has the advantages of being high in precision, high in flexibility and high in automation.

Description

Technical Field

[0001] This invention relates to the field of CNC machine tool composite machining technology, specifically to a flexible precision grinding system and method based on a machining center with a fixed reference. Background Technology

[0002] In the field of precision manufacturing, the machining of parts such as hydraulic valve cores and high-end molds often requires extremely high dimensional accuracy (e.g., ±0.005mm) and excellent surface roughness (e.g., Ra≤0.4μm). Traditionally, such precision grinding processes have relied heavily on dedicated grinding machines. While dedicated grinding machines can guarantee accuracy, their functions are limited and their flexibility is extremely poor. When products are changed, it often requires lengthy equipment adjustments, tooling changes, and even process reconstruction, making it difficult to adapt to the production demands of modern manufacturing, which involve multiple varieties, small batches, and rapid delivery.

[0003] On the other hand, general-purpose CNC machining centers, due to their high flexibility, powerful CNC functions, and wide process adaptability, have become the main equipment for machining complex parts. However, limited by their structural rigidity and thermal stability, and especially lacking precise online grinding wheel dressing and automatic wear compensation mechanisms, machining centers have long struggled to handle stable batch grinding operations with extremely high requirements for dimensional consistency. The industry has long faced the dilemma of "special-purpose grinding machines lacking flexibility, and general-purpose machine tools lacking precision."

[0004] Although attempts have been made to perform simple grinding on machining centers using grinding wheels, or to dress grinding wheels offline, closed-loop control of precision during the machining process cannot be achieved. For example, managing dressing tools as replaceable tools introduces tool change errors and repeatability errors; offline dressing cannot compensate for grinding wheel wear in real time, resulting in unstable machining quality and failing to meet the mass production requirements of high-precision parts. Summary of the Invention

[0005] The technical problem to be solved by this invention is the lack of a precise online grinding wheel dressing and automatic wear compensation mechanism in existing grinding processes.

[0006] To solve the above-mentioned technical problems, the technical solution of the present invention is to provide a flexible precision grinding system based on a fixed reference machining center. The system is installed on a grinding machine and includes a worktable, an intelligent control unit, and a machining center spindle. A reference platform is fixed on the worktable, and multiple fixtures are installed on the reference platform. Workpieces are clamped on the fixtures. A diamond dressing tool is fixed on one side of the worktable, and the location of the diamond dressing tool is the fixed reference point of the worktable. The machining center spindle is installed on the grinding machine, and a grinding wheel is installed at the lower end of the machining center spindle. The intelligent control unit is used to control the machining center spindle to drive the grinding wheel to process the workpiece or dress the grinding wheel according to a preset program.

[0007] Optionally, the intelligent control unit includes a process control module and a compensation module. The process control module is used to control the machining center spindle to move between a fixed reference point and the position of each workpiece according to a preset program, and to sequentially schedule and execute closed-loop grinding cycles for different workpieces.

[0008] The compensation module is used to control the machining center spindle to dress the grinding wheel, and automatically calculates and updates the tool radius compensation value of the grinding wheel after each dressing.

[0009] Optionally, the process control module of the intelligent control unit pre-stores machining program packages corresponding to each workpiece to realize serialized machining of different workpiece surfaces.

[0010] A precision grinding method using a flexible precision grinding system based on a fixed reference machining center includes the following steps: S1. Establishing a fixed datum and clamping multiple workpieces A diamond dressing tool is used as a fixed reference, and the coordinate point where the diamond dressing tool is located is a preset fixed point P; at the same time, at least two workpieces with different structures or process requirements are installed in different preset areas of the worktable using their respective special fixtures. S2, Fixed reference calibration The coordinates of the preset fixed point P are accurately determined by measuring the positional relationship between the preset fixed point P and at least one known auxiliary reference point in the machine tool coordinate system. S3, Serialized Closed-Loop Grinding Execution The intelligent control unit, according to preset logic, controls the machining center spindle to sequentially execute a closed-loop grinding cycle on each workpiece. This cycle includes: S31, Online Repair Drive the grinding wheel to move to the preset fixed point P, and make contact with the diamond dressing tool to dress the grinding wheel; S32, Automatic Wear Compensation Based on the amount of dressing, the tool radius compensation value of the grinding wheel in the intelligent control unit is automatically updated; S33, workpiece grinding Drive the dressed and compensated grinding wheel to perform precision grinding on the current target workpiece.

[0011] Optionally, in step S2, the coordinates of the preset fixed point P are determined using the non-collinear three-point positioning method. First, the preset fixed point P and two auxiliary reference points O and Q are selected, and then the coordinates of the preset fixed point P are calculated by measuring the relative positional relationship of the three.

[0012] Optionally, in step S3, the conditions for triggering the execution of online dressing step S31 are at least one of the following: the cumulative number of workpieces ground reaches a set value, the cumulative grinding time reaches a threshold, or the spindle load of the machining center exceeds a preset range.

[0013] In summary, the present invention has at least one of the following beneficial effects: 1. This invention achieves a precision closed loop, overcoming the precision grinding problem of general-purpose machine tools: by establishing and precisely calibrating a "fixed datum", combined with a real-time closed loop of "online dressing-automatic compensation", it fundamentally solves the industry bottleneck that machining centers cannot guarantee grinding accuracy due to the lack of stable dressing and wear compensation, enabling them to stably achieve the processing quality of special-purpose grinding machines (such as dimensional tolerance ±0.005mm, surface roughness Ra≤0.4μm).

[0014] 2. This invention creates unprecedented production flexibility: based on stable precision units, through multi-workpiece clamping layout and intelligent CNC program scheduling, it realizes unmanned continuous production of various different parts on a single machine. Changeover time can be shortened by more than 80%, and the overall utilization rate of equipment is greatly improved, perfectly meeting the market demand for multi-variety, small-batch production.

[0015] 3. This invention constructs a highly integrated intelligent system: deeply integrating functions such as benchmark management, process control, quality compensation and production scheduling into the CNC system, realizing a system-level solution from single part processing to multi-task mixed-flow production, and providing core technical support for building flexible manufacturing cells (FMC) and automated production lines.

[0016] 4. This invention reduces overall costs and technical barriers: users do not need to invest in multiple dedicated grinding machines, but can upgrade to obtain precision grinding and flexible production capabilities by utilizing widely available machining centers, thereby reducing fixed asset investment and maintenance costs. At the same time, the fully automated operation reduces reliance on operator skills. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the layout of the flexible precision grinding system of the machining center based on a fixed reference according to the present invention; Figure 2 A schematic diagram of the calibration method for fixed reference points in an embodiment of the present invention (OPQ three-point method); Figure 3 This is a flowchart of the serialized closed-loop grinding process of the present invention. Detailed Implementation

[0018] The following combination Figure 1-3 The present invention will be described in further detail below.

[0019] This invention discloses a flexible precision grinding system for machining centers based on fixed references. By innovatively setting the dressing tool as a fixed spatial reference and establishing an automatic compensation closed loop, it achieves stable and high-precision grinding capabilities on general-purpose machining centers, solving the problem of precision maintenance. Based on this precision closed-loop unit, a flexible production mode that supports continuous and automatic processing of multiple types of parts in a single clamping configuration is constructed to significantly improve production efficiency and resource utilization. The system is installed on a grinding machine tool, referring to... Figure 1 and Figure 2 The system includes a worktable, an intelligent control unit, and a machining center spindle 1. A reference platform 4 is fixed on the worktable, and multiple fixtures are installed on the reference platform 4. Workpieces are held in the fixtures. A diamond dressing tool 3 is fixed on one side of the worktable. The location of the diamond dressing tool 3 is the fixed reference point of the worktable. The machining center spindle 1 is mounted on a grinding machine. A grinding wheel 2 is installed at the lower end of the machining center spindle 1. The intelligent control unit is used to control the machining center spindle 1 to drive the grinding wheel 2 to process the workpiece or dress the grinding wheel 2 according to a preset program. Specifically, the diamond dressing tool 3 is permanently and vertically mounted on a preset fixed point P (such as the right rear) of the worktable (or reference platform 4) via a high-rigidity pen holder. Its "fixed" property is that once its machine tool coordinates are calibrated, it serves as an unchanging geometric reference origin in all subsequent machining cycles; Multiple specialized fixtures (such as) Figure 1 The 5A, 5B, and 5C components can be quickly installed at different planned positions on the platform according to production tasks, and different workpieces (such as...) can be clamped separately. Figure 1 (6A, 6B, 6C in the middle). Multiple grinding wheels 2 can be set. When not in use, the grinding wheels 2 are stored in the tool magazine of the machine tool.

[0020] In a further embodiment, the intelligent control unit includes a process control module and a compensation module. The process control module is used to control the machining center spindle 1 to move between a fixed reference point and the position of each workpiece according to a preset program, and to sequentially schedule and execute closed-loop grinding cycles for different workpieces. The compensation module is used to control the machining center spindle 1 to dress the grinding wheel 2, and automatically calculates and updates the tool radius compensation value of the grinding wheel 2 after each dressing. The intelligent control unit not only performs conventional trajectory control, but also integrates specialized process control and compensation logic, which can intelligently schedule the movement of the grinding wheel 2 between the preset fixed point P and each workpiece position, and orderly execute the complete closed-loop grinding cycle. The intelligent control unit's process control module has pre-stored machining program packages corresponding to each workpiece to achieve serialized machining of different workpiece surfaces; Its core working principle is as follows Figure 2As shown: Through precision calibration techniques such as the OPQ three-point method, the absolute coordinates (Xp, Yp) of the preset fixed point P are integrated into the machine tool coordinate system with high precision. This makes all dressing actions of the grinding wheel 2 have extremely high repeatability and positioning accuracy, providing a reliable geometric basis for subsequent automatic compensation, thus forming the cornerstone of the accuracy guarantee of the entire integrated system.

[0021] This invention also discloses a precision grinding method for a flexible precision grinding system based on a fixed reference machining center, characterized by comprising the following steps: S1. Establishing a fixed datum and clamping multiple workpieces Using the diamond dressing tool 3 as a fixed reference, and the coordinate point where the diamond dressing tool 3 is located as the preset fixed point P; at the same time, at least two workpieces with different structures or process requirements are installed in different preset areas of the worktable through their respective special fixtures. S2, Fixed reference calibration The coordinates of the preset fixed point P are accurately determined by measuring the positional relationship between the preset fixed point P and at least one known auxiliary reference point in the machine tool coordinate system. Specifically, the coordinates of the preset fixed point P are determined using the non-collinear three-point positioning method. First, the preset fixed point P and two auxiliary reference points O and Q are selected. Then, the coordinates of the preset fixed point P are calculated by measuring the relative positional relationship of the three points. S3, Serialized Closed-Loop Grinding Execution The intelligent control unit, according to preset logic, controls the machining center spindle 1 to sequentially execute a closed-loop grinding cycle on each workpiece. This cycle includes: S31, Online Repair Drive the grinding wheel 2 to move to the preset fixed point P, and make contact with the diamond dressing tool 3 to dress the grinding wheel; Specifically, the conditions for triggering this step S31 are at least one of the following: the cumulative number of workpieces ground reaches a set value, the cumulative grinding time reaches a threshold, the load on the machining center spindle 1 exceeds a preset range, or the machining program is executed according to a fixed cycle. S32, Automatic Wear Compensation Based on the amount of dressing, the tool radius compensation value of the grinding wheel 2 in the intelligent control unit is automatically updated; S33, workpiece grinding Drive the dressed and compensated grinding wheel 2 to perform precision grinding on the current target workpiece.

[0022] Example 1 This embodiment demonstrates the basic application of the method of the present invention as a precision machining unit, and verifies its effectiveness in solving the problem of maintaining accuracy.

[0023] Task: Batch grinding of the inner bore of hydraulic servo valve sleeves (requirements: φ18H5, Ra≤0.4μm).

[0024] Implementation: according to Figure 1 The principle is to fix the diamond dressing tool 3 at point P and clamp the workpiece on the worktable.

[0025] use Figure 2 The coordinates of point P are determined using the OPQ three-point method.

[0026] The core cycle logic in the CNC program is set as: "Dressing → Compensation → Grinding". The specific parameters are set as follows: this cycle is executed before grinding each workpiece, and the dressing amount per cycle is 0.02mm.

[0027] After the program is run, the system automatically executes the following closed-loop process: First, drive the grinding wheel 2 to move to point P for dressing → then automatically update the tool radius compensation value (radius reduced by 0.02mm) → then perform precision grinding on the workpiece; after the first piece is completed, this "dressing → compensation → grinding" process is repeated until the entire batch of workpieces is processed.

[0028] Results: This process ensures that grinding wheel 2 is restored to a sharp state and its effective cutting radius is precisely compensated before machining each workpiece. After machining 20 parts consecutively, the internal hole size variation remained stable within 0.005 mm, and the surface roughness Ra value remained stable below 0.4 μm. This fully verifies that the closed-loop cycle constituted by this invention can effectively isolate the influence of grinding wheel wear, achieving stable and repeatable precision grinding on the machining center.

[0029] Example 2: This embodiment demonstrates the flexible production capabilities achieved by the integrated system of the present invention, based on the precision unit verified in Embodiment 1.

[0030] Task: Machining three parts in sequence: sleeve (outer circle), distributor plate (inner hole), and cycloidal wheel (inner cycloidal).

[0031] Implementation: like Figure 1 The layout involves installing three dedicated fixtures and corresponding parts on the reference platform 4. The preset fixing point P has been marked.

[0032] The overall control program in the CNC system has the following scheduling logic: for each part, a closed-loop subroutine of "trimming → compensation → grinding" as verified in Example 1 is called. The program executes this complete closed loop sequentially for parts A, B, and C.

[0033] Start the master control program, and the equipment will operate in full automation: execute the "trimming → compensation → grinding" cycle for part A → execute the "trimming → compensation → grinding" cycle for part B → execute the "trimming → compensation → grinding" cycle for part C.

[0034] Results: The three heterogeneous grinding tasks were automatically and continuously completed in a standardized closed-loop unit after a single setup and start-up. This verifies the invention's ability to upgrade from a "precision machining unit" to a "flexible production system," realizing a leap from "dedicated machine for a single purpose" to "one machine with multiple functions" in the production mode.

[0035] In summary, this invention solves the root cause of precision problems by establishing a fixed benchmark, achieves process stability through closed-loop control, and ultimately realizes flexible production of multiple product types through system integration. It provides a reliable technical path for upgrading existing machining center resources to obtain high-end precision grinding and flexible manufacturing capabilities, possessing significant practical value and promising prospects for widespread application.

[0036] It should be noted that the above 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 preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A flexible precision grinding system based on a fixed datum machining center, the system being mounted on a grinding machine, characterized in that, The system includes a worktable, an intelligent control unit, and a machining center spindle (1). A reference platform (4) is fixed on the worktable. Multiple fixtures are installed on the reference platform (4). Workpieces are held on the fixtures. A diamond dressing tool (3) is fixed on one side of the worktable. The location of the diamond dressing tool (3) is the fixed reference point of the worktable. The machining center spindle (1) is mounted on a grinding machine. A grinding wheel (2) is installed at the lower end of the machining center spindle (1). The intelligent control unit is used to control the machining center spindle (1) to drive the grinding wheel (2) to process the workpiece or dress the grinding wheel (2) according to a preset program.

2. The flexible precision grinding system based on a fixed reference machining center according to claim 1, characterized in that, The intelligent control unit includes a process control module and a compensation module. The process control module is used to control the machining center spindle (1) to move between a fixed reference point and the position of each workpiece according to a preset program, and to sequentially schedule and execute closed-loop grinding cycles for different workpieces. The compensation module is used to control the machining center spindle (1) to dress the grinding wheel (2), and automatically calculates and updates the tool radius compensation value of the grinding wheel (2) after each dressing.

3. The flexible precision grinding system based on a fixed reference machining center according to claim 1, characterized in that, The intelligent control unit has a pre-stored machining program package corresponding to each workpiece in its process control module, so as to realize the serialized machining of different workpiece surfaces.

4. The precision grinding method of the flexible precision grinding system based on a fixed reference machining center as described in claim 3, characterized in that, Includes the following steps: S1. Establishing a fixed datum and clamping multiple workpieces Using the diamond dressing tool (3) as a fixed reference, and using the coordinate point where the diamond dressing tool (3) is located as a preset fixed point P; at the same time, at least two workpieces with different structures or process requirements are installed in different preset areas of the worktable through their respective special fixtures. S2, Fixed reference calibration The coordinates of the preset fixed point P are accurately determined by measuring the positional relationship between the preset fixed point P and at least one known auxiliary reference point in the machine tool coordinate system. S3, Serialized Closed-Loop Grinding Execution The intelligent control unit controls the machining center spindle (1) to perform a closed-loop grinding cycle on each workpiece in sequence according to preset logic. The cycle includes: S31, Online Repair Drive the grinding wheel (2) to move to the preset fixed point P and contact the diamond dressing tool (3) to dress the grinding wheel; S32, Automatic Wear Compensation Based on the amount of dressing, the tool radius compensation value of the grinding wheel (2) in the intelligent control unit is automatically updated; S33, workpiece grinding Drive the dressed and compensated grinding wheel (2) to perform precision grinding on the current target workpiece.

5. The precision grinding method of the flexible precision grinding system based on a fixed reference machining center according to claim 4, characterized in that, In step S2, the coordinates of the preset fixed point P are determined using the non-collinear three-point positioning method. First, the preset fixed point P and two auxiliary reference points O and Q are selected. Then, the coordinates of the preset fixed point P are calculated by measuring the relative positional relationship of the three.

6. The precision grinding method of the flexible precision grinding system based on a fixed reference machining center according to claim 6, characterized in that, In step S3, the conditions for triggering the execution of online dressing step S31 are at least one of the following: the cumulative number of workpieces ground reaches the set value, the cumulative grinding time reaches the threshold, or the load of the machining center spindle (1) exceeds the preset range.

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