A method for evaluating energy efficiency of surface grinding process

Abstract

This invention discloses a method for evaluating the energy efficiency of a surface grinding process. By establishing an energy efficiency evaluation model for the surface grinding process, calculating the time history of the energy efficiency model, measuring the fixed power value of the surface grinding process, and establishing a variable power fitting model for the surface grinding process, this method achieves a comprehensive evaluation of the energy efficiency of the surface grinding process. This method can provide companies with comprehensive analysis and optimization design of the energy utilization characteristics of the grinding process, promoting energy conservation and emission reduction in the grinding and other precision manufacturing industries.

Description

Technical Field

[0001] The invention is applied to the field of sustainable design and manufacturing technology, and relates to a method for evaluating the energy efficiency of a precision machining process, and in particular to a method for evaluating the energy efficiency of a surface grinding process. Background Art

[0002] At present, there have been preliminary explorations into the research on energy efficiency assessment methods for CNC machine tools. Chinese invention patent CN109491323B discloses a "CNC machine tool load-energy efficiency assessment and monitoring method for energy conservation and emission reduction". By calculating the ideal processing energy consumption value of a single part and monitoring the actual processing energy consumption value of a single part, the load-energy efficiency of the CNC machine tool is obtained, and a relationship model between the load-energy efficiency of the CNC machine tool and the load rate of the CNC machine tool is constructed to realize the load-energy efficiency monitoring and over-limit alarm of the CNC machine tool, so that the load-energy efficiency of the CNC machine tool is controlled within the required range. Chinese invention patent CN103676782B discloses an "online detection method for energy efficiency during the processing of a CNC milling machine". A power analyzer is used to measure the standby power, no-load power and cutting power of the spindle, x-axis, y-axis and z-axis of the CNC milling machine, and the energy efficiency of the CNC milling machine is calculated based on the measurement results of the power analyzer. Chinese invention patent CN109634238B discloses a "Method for Evaluating and Monitoring the Quality-Energy Efficiency of CNC Machine Tool Machining Processes". Based on the CNC machine tool machining quality pass rate and the energy consumption of the CNC machine tool when there are defective products and no defective products in a given cycle, a relationship model between the quality-energy efficiency of the CNC machine tool and the machining quality pass rate is constructed, and the quality-energy efficiency of the CNC machine tool machining process is monitored in real time and over-limit alarms and controls are implemented.

[0003] Compared with turning, drilling, and milling processes, grinding is relatively efficient and low-cost, and the market share of grinding machines has now exceeded 43%. However, it consumes more energy when removing unit volume of material. For example, grinding steel materials requires 30-50J / mm 3 The specific energy of ceramic materials can even reach 120J / mm 3 Specific energy, much higher than molten iron or nickel (10J / mm 3 Furthermore, to ensure product quality during grinding, energy efficiency can even fall below 10%. For example, in a case study of grinding steel, the spindle energy efficiency dropped to as low as 2.76% when the energy consumption of the machine's electrical, cooling, and feed systems was not considered. Therefore, improving energy utilization and reducing electrical energy consumption during grinding has become a key issue in grinding technology.

[0004] Compared to existing research on machine tool energy efficiency analysis and assessment, methods for evaluating the energy efficiency of CNC machine tool processes primarily focus on online assessment, monitoring, early warning, and control of machine tool load and process quality during turning, milling, and drilling. These methods fail to consider the impact of machining parameters and machining distance settings on process energy efficiency, nor do they optimize the design of CNC machine tool process energy efficiency to improve energy utilization. Grinding processes, in particular, utilize repeated intermittent feeds between the grinding spindle and the x, y, and z axes, removing material from the workpiece surface in a segmented manner, resulting in more complex energy consumption patterns. Therefore, accurately evaluating the energy efficiency of grinding processes is crucial for analyzing the energy characteristics of CNC grinders, optimizing grinding parameters, improving grinding process energy utilization, and reducing energy consumption. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for evaluating the energy efficiency of a surface grinding process. By calculating the time history of the surface grinding process, measuring the fixed power of the CNC grinding machine subsystem and establishing a variable power model related to the grinding process parameters, the energy efficiency of the surface grinding process can be accurately evaluated, and then the energy utilization characteristics of the CNC grinding machine can be analyzed to promote energy conservation and emission reduction in the grinding process.

[0006] The present invention provides a method for evaluating the energy efficiency of a surface grinding process, comprising the following steps: 1) establishing an energy efficiency evaluation model for the surface grinding process; 2) calculating a time history of the surface grinding process; 3) measuring a subsystem power value of the surface grinding process in which the power consumed is independent of process parameters; 4) establishing a subsystem power model in which the power consumed is related to the process parameters; 5) designing grinding experiments at different levels of spindle speed, workpiece feed speed, and grinding depth, constructing grinding experiment sample points, and using a Gauss-Newton gradient method to fit undetermined coefficients in the energy efficiency evaluation model; and 6) evaluating the energy efficiency of the surface grinding process.

[0007] Step 1): Establish an energy efficiency evaluation model for the surface grinding process.

[0008] The energy efficiency η of the surface grinding process is defined as the active energy consumption, i.e., the material removal energy consumption E mrr Total energy consumption E of CNC grinding machine total Ratio:

[0009]

[0010] Among them, the total energy consumption of CNC grinding machine is E total Including electrical control energy consumption E e , cooling process energy consumption E c , spindle rotation energy consumption E s, Energy consumption of table x-axis left and right feeding E x , Grinding wheel y-axis downward feed energy consumption E y And the energy consumption E of the worktable z-axis forward and backward feed z , material removal energy consumption E mrr Specifically refers to the electrical control energy consumption E during the material removal stage em , cooling process energy consumption E cm , spindle energy consumption E sm And the energy consumption E of the worktable x-axis left and right feed xm .

[0011] The energy consumption of each part described in formula (1) is the product of the real-time power of each component and the action time, which can be further expressed as:

[0012]

[0013] Among them, the electrical control power P e , cooling power P c , Grinding wheel y-axis feed power P y And the worktable z-axis feed power P z It has nothing to do with the grinding process parameters and is a constant value. The electrical control action time is the entire time history of the grinder standby, idle stroke and processing. The cooling action time is the grinding idle stroke and processing time history. The grinding wheel y-axis feed time t y and z-axis feed time t z It is related to the acceleration and deceleration characteristics of the grinding machine motor, the size of the grinding workpiece, the grinding amount and the gap setting; the spindle rotation power consists of two parts, the air grinding power P sa and material removal power P sm , where P sa The action time is the time history of the front and rear air grinding stage, the left and right air grinding stage and the material removal stage t a1 , t a2 and t m , P sm The action time is the material removal stage time history t m , the worktable x-axis left and right feed power consists of two parts, the worktable feed power P xm and the maximum power P of the workbench x , where P xm The action time is the material removal stage time history t m and the time history of the front and back empty grinding stages t a1 , P x The action time is the time history of the left and right empty grinding stages t a2 .

[0014] Step 2): Calculate the time history of the surface grinding process.

[0015] The surface grinding process time history includes four time stages: waiting stage, front and rear idle grinding stage, left and right idle grinding stage, and material removal stage. The waiting stage time t sb is a constant, and the time of the front and back empty grinding stages is t a1 , Left and right empty grinding stage time t a2 and material removal phase time t m According to the geometric relationship between grinding clearance, grinding width, grinding parameters and workpiece size, it is determined as

[0016]

[0017]

[0018] Among them, c y and c z are the feed time of y-axis and z-axis respectively, which are constants. L is the length of the workpiece to be processed, b is the machining gap between the left and right sides of the workpiece, and V w is the workpiece feed speed, n, n j 、n so They are the total grinding stroke number, effective grinding stroke number and spark-free grinding stroke number of one grinding cycle, respectively, expressed as

[0019]

[0020] Where W is the width of the workpiece to be machined, a is the machining gap between the front and rear sides of the workpiece, and w is the grinding width.

[0021] In formula (2), the z-axis feed time t z for

[0022] t z =c z ×n (9)

[0023] Among them, c z is the feed time of the z-axis, and n is the total number of grinding strokes in one grinding cycle.

[0024] Step 3): Measure the power value of the subsystem that is independent of the process parameters during the surface grinding process.

[0025] Connect the power meter to the U, V, and W three-phase output terminals of the grinder power air circuit breaker. Turn on the grinder air circuit breaker and CNC console switches. Wait until the grinder and CNC console are started up. Measure the grinder power at this time as the grinder electrical control system power. Turn on the grinder cooling system. Measure the increased power at this time as the grinder cooling system power. Turn on the grinding wheel y-axis. Measure the maximum power increase at this time as the y-axis maximum power. Turn on the workbench z-axis. Measure the maximum power increase at this time as the z-axis maximum power. Repeat step 3) 5 times under different operating conditions in the factory workshop to obtain the average power of the electrical control system as P. e , the average power of the grinding machine cooling system is taken as P c The average value of the maximum power of the grinding wheel y axis is taken as P y , the average value of the maximum power of the workbench z axis is taken as P z , and when the grinder model is changed, repeat step 3) to obtain P for the new grinder model e 、P c 、P y and P z .

[0026] Step 4): Establish a subsystem power model related to the power consumed in the surface grinding process and the process parameters.

[0027] The variable power related to the process parameters in the surface grinding process includes the spindle air grinding power P sa , Spindle material removal power P sm , the worktable x-axis left and right feed power P xm , Maximum power P of workbench x-axis steering x Among them, the spindle air grinding power characteristic is that the spindle drives the grinding wheel to rotate at high speed and overcomes the resistance of the spindle drive mechanical transmission system, with the grinding wheel linear speed V s Establish a linear model of the grinding machine spindle idle grinding power as the independent variable:

[0028] P sa =k+δV s (10)

[0029] Among them, k and δ are unknown coefficients, which are related to the shape, size, weight and connection rigidity of the grinding wheel used in the grinding process.

[0030] The spindle material removal power characteristic is to remove the workpiece material by brittle fracture after overcoming the plastic deformation threshold of the material to be processed, with the grinding wheel linear speed V s , workpiece feed speed V w , grinding depth a p An exponential model of the spindle material removal power is constructed as the independent variable:

[0031]

[0032] Among them, κ, α, β, and γ are unknown coefficients, which are related to the characteristics of the grinding wheel abrasive material and the workpiece material to be processed.

[0033] The power characteristics of the left and right feed of the worktable x-axis are the electric drag of the grinder worktable, with the workpiece feed speed V w A quadratic function model of the left and right feed power of the worktable x-axis is established as the independent variable:

[0034]

[0035] Among them, λ, μ, and ν are unknown coefficients, which are related to the weight of the grinding machine table, the sliding friction coefficient between the table and the grinding machine, and the connection rigidity of the grinding machine system.

[0036] Maximum power P of workbench x-axis steering x Related to the starting characteristics of the x-axis motor, the workpiece feed speed V w Establish a cubic function model of the maximum power of the workbench x-axis steering as the independent variable:

[0037]

[0038] Among them, η, ξ, ψ, and ω are unknown coefficients, which are related to the weight of the grinding machine table, the sliding friction coefficient between the table and the grinding machine, and the connection rigidity of the grinding machine system.

[0039] Step 5): Design the three-factor grinding wheel speed V for surface grinding s , workpiece feed speed V w and grinding depth a p In the horizontal grinding experiment, after the grinder, grinding wheel model and workpiece to be processed are selected, the power meter is connected to the output three-phase lines of the grinder spindle and the worktable x-axis servo system, and the grinding power P of the grinder spindle is measured. sa , Spindle material removal power P sm And the worktable x-axis left and right feed power P xm , Maximum power P of workbench x-axis steering x , construct the grinding experiment sample points, and use the Gauss-Newton fast iteration method to obtain the unknown coefficients k, α, β, and γ in formulas (10)–(13). When the workpiece, grinding wheel, or grinding machine to be processed is replaced, repeat step 5) to obtain the unknown coefficients for the new workpiece, grinding wheel model, or grinding machine model.

[0040] Step 6): Evaluate the energy efficiency of the surface grinding process.

[0041] The present invention proposes a method for evaluating the energy efficiency of a surface grinding process, which can provide enterprises with a comprehensive analysis and evaluation of the energy utilization characteristics of the grinding process. The method can also be applied to other processing technologies and abrasive tool manufacturers, promoting energy conservation and emission reduction in the manufacturing industry related to abrasive tool grinding, and achieving good economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A flow chart of the steps of a method for evaluating the energy efficiency of a surface grinding process.

[0043] Figure 2 This is an energy consumption flow diagram of the surface grinding process.

[0044] Figure 3 A grinding path diagram for a surface grinding process.

[0045] Figure 4 This is a spindle power waveform diagram during a surface grinding process.

[0046] Figure 5 This is a waveform diagram of the x-axis power during a surface grinding process.

[0047] Figure 6 Comparison of experimental and model-predicted results for spindle and x-axis power in a surface grinding process. DETAILED DESCRIPTION

[0048] The specific implementation methods of the present invention are explained in detail with reference to the accompanying drawings and implementation cases.

[0049] Combined with attachment Figure 1 , a method for evaluating the energy efficiency of a surface grinding process described in the present invention is described in detail, comprising the following steps: 1) establishing an energy efficiency evaluation model for a surface grinding process; 2) calculating the time history of the surface grinding process; 3) measuring the power value of a subsystem in which the power consumed by the surface grinding process is independent of the process parameters; 4) establishing a subsystem power model in which the power consumed by the surface grinding process is related to the process parameters; 5) designing grinding experiments at different levels of spindle speed, workpiece feed speed, and grinding depth, constructing grinding experiment sample points, and using the Gauss-Newton gradient method to fit the unknown coefficients in the energy efficiency evaluation model; 6) evaluating the energy efficiency of the surface grinding process.

[0050] Combined with attachment Figure 2, detailed description of the energy efficiency evaluation model for the surface grinding process established in step 1). The electric energy consumption of the CNC grinding machine comes from the electrical control, spindle rotation, feed motion of the x, y, and z axes, and cooling process. During the grinding process, a large amount of electric energy flows to the machine tool standby and idle stroke stages, resulting in low energy efficiency in the actual processing, i.e., the material removal stage, during the grinding process. The energy efficiency η of the surface grinding process is defined as the active consumption, i.e., the material removal energy consumption E mrr Total energy consumption E of CNC grinding machine total The ratio of the total energy consumption of CNC grinding machine is E total Including electrical control energy consumption E e , cooling process energy consumption E c , spindle rotation energy consumption E s , Energy consumption of table x-axis left and right feeding E x , Grinding wheel y-axis downward feed energy consumption E y And the energy consumption E of the worktable z-axis forward and backward feed z , material removal energy consumption E mrr Specifically refers to the electrical control energy consumption E during the material removal stage em , cooling process energy consumption E cm , spindle energy consumption E sm And the energy consumption E of the worktable x-axis left and right feed xm .

[0051] Combined with attachment Figure 3 The surface grinding process time history of the surface grinding machine is described in detail in step 2). The surface grinding process time history includes four time stages: standby stage, front and rear idle grinding stage, left and right idle grinding stage, and material removal stage. The standby stage time t of the SMART B818III CNC grinding machine is t sb The time of the front and rear empty grinding stages is t a1 Including the actual front and rear air grinding and the SMART B818III CNC grinding machine's Y-axis feed time c y 0.6s, about the time of the dry grinding stage t a2 Including the actual left and right idle grinding and n times of z-axis feeding time, among which the z-axis feeding time of SMART B818III CNC grinding machine is c z is 0.3s. According to formulas (3)–(9) and the geometric relationship of the grinding gap a=5mm, b=10mm, grinding width w=5mm and workpiece size L=50mm, W=50mm in the case of surface grinding of quartz ceramics, and the workpiece feed speed V w (Take 4m / min as an example) The time model in formula (2) can be further obtained, where t a1 4.35s, t a210.80s, t m 7.50s, t y 0.6s, t z 3.6s, t e 37.39s, t c It is 22.65s.

[0052] Combined with the case of quartz ceramic surface grinding by SMART B818III CNC grinder, the fixed power value that is not related to the process parameters in step 3) is measured in detail. The five fixed power measurement values ​​are shown in Table 1, and the measurement average value P is obtained. e 437.90W, P c 67.02W, P y 0.94W and P z It is 16.01W.

[0053] Table 1 Fixed power values ​​of SMART B818III CNC grinder independent of grinding parameters

[0054]

[0055] Combined with SMART B818III CNC grinding machine surface grinding quartz ceramic case and attached Figure 4 and attached Figure 5 , describe in detail the spindle air grinding power P in step 4) and step 5) sa , Spindle material removal power P sm And the worktable x-axis left and right feed power P xm , Maximum power P of workbench x-axis steering x In the case of surface grinding of quartz ceramics, the spindle speed V is designed. s , workpiece feed speed V w and grinding depth a p There are 10 groups of grinding experiments with 3 factors and 4 levels. The spindle and x-axis power waveforms measured in the first group of experiments are shown in the attached figure. Figure 4 and attached Figure 5 The grinding parameters and spindle and x-axis power experimental values ​​of the 10 groups of grinding experiments are shown in Table 2.

[0056] Table 2 Experimental values ​​of spindle and x-axis power of SMART B818III CNC grinder related to grinding parameters

[0057]

[0058] According to the Gauss-Newton gradient method described in step 5), the spindle air grinding power P is obtained. sa , Spindle material removal power P sm And the worktable x-axis feed power P xm, Maximum power P of workbench x-axis steering x The model coefficients are shown in Table 3.

[0059] Table 3 Power model coefficients

[0060]

[0061] Combined with SMART B818III CNC grinding machine surface grinding quartz ceramic case and attached Figure 6 , detailing the model accuracy of the variable power of the fitting subsystem. In addition, 4 sets of grinding experiments were designed to verify the accuracy of the power fitting model in step 5). The grinding experiment parameters, experimentally measured power, and calculated power results are shown in Table 4. Figure 6 It can be seen that the total error of the subsystem power model established in step 5) is within 5%, which can be used to evaluate the energy efficiency of the surface grinding process.

[0062] Table 4 Comparison of experimental and calculated power values ​​of the validation group

[0063]

[0064] Combined with the case of surface grinding quartz ceramics by the SMART B818III CNC grinder, according to the energy efficiency evaluation method of the surface grinding process, the energy efficiency evaluation results of the surface grinding process in step 6) are described in detail. The energy efficiency evaluation results of the four verification groups are 28.30%, 28.50%, 33.37% and 24.95%, respectively.

Claims

1. A method for evaluating energy efficiency of a surface grinding process, characterized in that: The following steps are involved: 1) Establish an energy efficiency evaluation model for the surface grinding process; 2) Calculate the time history of the surface grinding process; 3) Measure the power values ​​of the subsystems of the surface grinding process that are independent of the process parameters; 4) Establish a subsystem power model for the surface grinding process that is dependent on the process parameters; 5) Design grinding experiments at different levels of spindle speed, workpiece feed rate, and grinding depth, construct grinding experiment sample points, and use the Gauss-Newton gradient method to fit the unknown coefficients in the energy efficiency evaluation model; 6) Evaluate the energy efficiency of the surface grinding process; Step 1): Establish an energy efficiency evaluation model for the surface grinding process, where the energy efficiency η is defined as the active energy consumption, i.e., the material removal energy consumption E mrr Total energy consumption E of CNC grinding machine total The ratio of the total energy consumption of CNC grinding machine is E total Including electrical control energy consumption E e , cooling process energy consumption E c , spindle rotation energy consumption E s , Energy consumption of table x-axis left and right feeding E x , Grinding wheel y-axis downward feed energy consumption E y And the energy consumption E of the worktable z-axis forward and backward feed z , the material removal energy consumption E mrr Specifically refers to the electrical control energy consumption E during the material removal stage em , cooling process energy consumption E cm , spindle energy consumption E sm And the energy consumption E of the worktable x-axis left and right feed xm , The energy consumption of each part is the product of real-time power and action time, which can be further expressed as: Among them, t sb , t a1 , t a2 , t m , t y , t z They are machine tool standby time, front and rear idle grinding time, left and right idle grinding time, material removal time, y-axis feed time and z-axis feed time, P e 、P c 、P y and P z They are the electrical control power, cooling power, grinding wheel y-axis downward feed power and worktable z-axis forward and backward feed power, which are constant values. sa 、P sm 、P xm and P x They are spindle air grinding power, spindle material removal power, table x-axis left and right feed power and table steering maximum power, which are related to the grinding process parameters; Step 2): Calculate the time history of the surface grinding process, which includes four time stages: waiting stage, front and rear idle grinding stage, left and right idle grinding stage, and material removal stage. The waiting stage time t sb is a constant, and the time of the front and back empty grinding stages is t a1 , Left and right empty grinding stage time t a2 , Material removal stage time t m It is determined according to the geometric relationship between the grinding clearance, grinding width, grinding parameters and workpiece size, among which the time of the front and rear idle grinding stages t a1 Including the actual idle grinding time and the y-axis feeding time, the left and right idle grinding stage time t a2 Including the actual idle grinding time and the z-axis feed time, the y-axis and z-axis feed time are constant; Step 3): Measure the power value of the subsystem that is not related to the process parameters during the surface grinding process, connect the power meter to the U, V, and W three-phase output terminals of the grinder power air circuit breaker, turn on the grinder air circuit breaker switch and the CNC console switch, wait for the grinder and CNC console to start up, measure the grinder power at this time as the grinder electrical control system power, turn on the grinder cooling system, measure the power increased at this time as the grinder cooling system power, set the grinding wheel y-axis feed once, measure the maximum power increase at this time as the y-axis maximum power, set the workbench z-axis feed once, measure the maximum power increase at this time as the z-axis maximum power, repeat step 3) 5 times under different operating conditions in the factory workshop, and obtain the average power of the electrical control system as P e , the average power of the grinding machine cooling system is taken as P c The average value of the maximum power of the grinding wheel y axis is taken as P y , the average value of the maximum power of the workbench z axis is taken as P z , and when the grinder model is changed, repeat step 3) to obtain P for the new grinder model e 、P c 、P y and P z ; Step 4): Establish a subsystem power model related to the power consumed in the surface grinding process and the process parameters, wherein the variable power related to the process parameters in the surface grinding process includes the spindle idle grinding power P sa , Spindle material removal power P sm , the worktable x-axis left and right feed power P xm , Maximum power P of workbench x-axis steering x Among them, the spindle air grinding power characteristic is that the spindle drives the grinding wheel to rotate at high speed and overcomes the resistance of the spindle drive mechanical transmission system, with the grinding wheel linear speed V s Establish a linear model of the grinding machine spindle idle grinding power as the independent variable: P sa =k+δV s (3) Among them, k and δ are unknown coefficients, which are related to the shape, size, weight and connection rigidity of the grinding wheel used in the grinding process; The spindle material removal power characteristic is to remove the workpiece material by brittle fracture after overcoming the plastic deformation threshold of the material to be processed, with the grinding wheel linear speed V s , workpiece feed speed V w , grinding depth a p An exponential model of the spindle material removal power is constructed as the independent variable: Among them, κ, α, β, and γ are unknown coefficients, which are related to the characteristics of the grinding wheel abrasive material and the workpiece material to be processed; The power characteristics of the left and right feed of the worktable x-axis are the electric drag of the grinder worktable, with the workpiece feed speed V w A quadratic function model of the left and right feed power of the worktable x-axis is established as the independent variable: Among them, λ, μ, and ν are unknown coefficients, which are related to the weight of the grinding machine table, the sliding friction coefficient between the table and the grinding machine, and the connection rigidity of the grinding machine system; The characteristics of the maximum power of the worktable x-axis steering are related to the starting characteristics of the x-axis motor, and the workpiece feed speed V w Establish a cubic function model of the maximum power of the workbench x-axis steering as the independent variable: Among them, η, ξ, ψ, and ω are unknown coefficients, which are related to the weight of the grinding machine table, the sliding friction coefficient between the table and the grinding machine, and the connection rigidity of the grinding machine system; Step 5): Design the three-factor grinding wheel speed V for surface grinding s , workpiece feed speed V w and grinding depth a p In the horizontal grinding experiment, after the grinder, grinding wheel model and workpiece to be processed are selected, the power meter is connected to the output three-phase lines of the grinder spindle and the worktable x-axis servo system, and the grinding power P of the grinder spindle is measured. sa , Spindle material removal power P sm And the worktable x-axis left and right feed power P xm , Maximum power P of workbench x-axis steering x , construct the grinding experiment sample points, use the Gauss-Newton fast iteration method to obtain the undetermined coefficients in formulas (3)–(6), and when the workpiece, grinding wheel or grinding machine to be processed is replaced, repeat step 5) to obtain the undetermined coefficients for the new workpiece, grinding wheel model or grinding machine model; Step 6): Evaluate the energy efficiency of the surface grinding process.

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