A method for controlling the depth of grinding in layers using electrical discharge ablation-assisted grinding

Abstract

The first step of the discharge ablation-assisted grinding method with depth-layer control is to set the first-layer grinding depth δ1, the reference grinding force F0, and the pure mechanical grinding depth δ. 纯 Pure mechanical single-layer grinding depth δ 单 The first step involves determining the values ​​of the grinding wheel speed, the grinding wheel transverse feed rate, and the exponential constant n. The second step involves performing the first layer of discharge ablation-assisted grinding. The third step involves comparing the average grinding force F1 of the first layer with F0 to obtain the second layer grinding depth δ2. The fourth step involves performing the second layer of discharge ablation-assisted grinding. The fifth step involves comparing the average grinding force F2 of the second layer with F0 to obtain the third layer grinding depth δ3. The sixth step involves repeating this process until the remaining machining allowance is less than the pure mechanical grinding depth δ. 纯 The process switches to pure mechanical grinding. This invention controls the grinding depth of a single layer through real-time feedback of grinding force. When the remaining machining allowance is less than a set value, it switches to pure mechanical grinding to ensure that the molten and solidified layer is completely removed, thus achieving efficient and stable processing.

Description

Technical Field

[0001] This invention relates to the field of electrical discharge ablation assisted grinding technology, specifically to an electrical discharge ablation assisted grinding method that uses a constant speed and constant feed of the grinding wheel and controls the grinding depth in layers based on the detection of the average grinding force value. Background Technology

[0002] In aerospace, precision instrument manufacturing, and other fields, the application of difficult-to-machine metal materials such as titanium alloys and high-temperature alloys is becoming increasingly widespread. Due to their high strength and hardness, these materials pose significant challenges to the precision machining of their components. Traditional mechanical grinding processes suffer from problems such as high grinding forces, severe wheel wear, and low machining efficiency. While electrical discharge machining (EDM) can handle high-hardness materials, it suffers from low removal efficiency and the formation of a molten solidified layer on the machined surface, making it difficult to meet the requirements for high-efficiency machining.

[0003] Electrical discharge ablation-assisted grinding (EDA) is a composite machining method that combines electrical discharge induced ablation with mechanical grinding. The basic principle is as follows: First, a plasma channel is formed between the electrode and the workpiece using a pulsed power supply. The instantaneous high temperature generated by this channel rapidly activates the metal on the workpiece surface. Then, the activated metal undergoes a violent combustion reaction with oxygen between the electrodes, heating a large amount of metal to a molten state. This molten metal is removed under the action of a scouring medium. Some of the remaining molten material re-solidifies on the machining surface, forming a molten solidified layer. This layer is then removed by the abrasive grains of the grinding wheel. Because the hardness of the molten solidified layer and the underlying softened metal is lower than that of the original substrate material, the grinding force is lower than that of conventional pure mechanical grinding.

[0004] Existing electro-discharge assisted grinding (EDA) is based on the concept of average layering in mechanical grinding, meaning each layer has the same grinding depth. Since the EDA process is related to the inter-electrode discharge state, the amount of material removed and the surface softening effect vary with each layer. When a layer has less EDA, the grinding force of the next layer increases, easily damaging the workpiece surface. To avoid damage due to excessive grinding force, the grinding depth is usually set relatively small, resulting in low processing efficiency. Conversely, when a layer has more EDA, the grinding force of the next layer decreases, allowing for an increase in grinding depth to improve efficiency. However, current technology cannot effectively control the grinding depth. Therefore, the fixed grinding depth used in existing EDA-assisted grinding methods makes it difficult to achieve efficient EDA-assisted grinding. Summary of the Invention

[0005] The purpose of this invention is to address the lack of dynamic layered control over grinding depth in existing discharge ablation assisted grinding technology, which makes it difficult to adapt to dynamic changes during material removal. This invention provides a discharge ablation assisted grinding method with layered grinding depth control. The method of this invention controls the grinding depth of a single layer through real-time feedback of grinding force, and switches to pure mechanical grinding when the remaining machining allowance is less than the set pure mechanical grinding depth, ensuring that the molten solidified layer is completely removed at the end of the machining process, thereby achieving efficient and stable machining.

[0006] The technical solution of this invention is:

[0007] A method for controlling the depth of grinding in layers using electrical discharge ablation-assisted grinding includes the following steps:

[0008] Step 1: Set the first grinding depth δ1, the reference grinding force F0, and the pure mechanical grinding depth δ 纯 Pure mechanical single-layer grinding depth δ 单 The values ​​of grinding wheel speed, grinding wheel transverse feed rate, and exponential constant n, where 0 < n < 1;

[0009] Step 2: Perform the first layer of discharge ablation assisted grinding; take the first layer grinding time as the sampling period and the grinding force during the first layer grinding as the sampling signal. After the first layer grinding is completed, use the processor to calculate the average grinding force F1 of the first layer processing.

[0010] Step 3: Compare the average grinding force F1 of the first layer with the set reference grinding force F0 to obtain the scaling factor K1. Multiply the grinding depth δ1 of the first layer by the scaling factor K1 to obtain the grinding depth δ2 of the second layer; where the scaling factor K1 = (F0 ÷ F1). n ;

[0011] Step 4: Perform second-layer discharge ablation assisted grinding with the obtained second-layer grinding depth δ2; take the second-layer grinding time as the sampling period and the grinding force during the second-layer grinding as the sampling signal. After the second-layer grinding is completed, use the processor to calculate the average grinding force F2 of the second-layer processing.

[0012] Step 5: Compare the average grinding force F2 of the second layer with the set reference grinding force F0 to obtain the scaling factor K2. Multiply the second layer grinding depth δ2 by the scaling factor K2 to obtain the third layer grinding depth δ3; where the scaling factor K2 = (F0 ÷ F2). n ;

[0013] Step 6: Continue in this manner until the remaining machining allowance is less than the set pure mechanical grinding depth δ. 纯 The oxygen and pulse power supply are turned off, switching to pure mechanical grinding; the pure mechanical grinding process uses a set pure mechanical single-layer grinding depth δ. 单Continue grinding in layers to remove the molten and solidified layer on the workpiece surface.

[0014] Compared with existing technologies, in the process of electrical discharge ablation assisted grinding, the present invention uses a grinding wheel fed at a constant rotational speed and transverse speed to efficiently ablate and remove workpiece material, while simultaneously grinding away part of the molten and solidified layer. The average grinding force of the current layer is obtained by using the processing time of the current layer as the sampling period and the real-time grinding force of the current layer as the sampling signal. The average grinding force is compared with the set reference grinding force F0 to obtain a scaling factor as the basis for adjusting the depth of cut. The grinding depth of the next layer is adjusted accordingly. When the average grinding force obtained by sampling is greater than the set reference grinding force F0, the grinding depth of the current layer is multiplied by the scaling factor (which is less than 1 in this case). To reduce the grinding depth of the next layer and avoid excessive pure grinding during the next grinding process; when the average grinding force obtained by sampling is less than the set reference grinding force F0, the grinding depth of this layer is multiplied by the scaling factor (which is greater than 1 at this time), the grinding depth of the next layer is increased, the material removal is increased, and finally, the actual grinding force gradually tends to the set grinding force, so that each layer of discharge ablation assisted grinding is in the desired processing state, and when the remaining processing allowance is less than the set pure mechanical grinding depth, it switches to pure mechanical grinding, ensuring that the molten solidified layer is completely removed at the end of the processing, thereby achieving efficient and stable processing.

[0015] Furthermore, during processing, the appropriate grinding wheel speed and transverse feed rate are determined based on the workpiece material and processing requirements. Preferably, in the aforementioned discharge ablation-assisted grinding method for depth-layer control, the set grinding wheel speed is in the range of 50-3000 rpm, and the set grinding wheel transverse feed rate is in the range of 1 mm / s-50 mm / s.

[0016] Furthermore, in the aforementioned discharge ablation-assisted grinding method with layered grinding depth control, the first grinding depth δ1 is set within the range of 1-20 μm. During processing, the specific value of the first grinding depth δ1 is determined based on the material and processing requirements.

[0017] Furthermore, preferably, in the aforementioned discharge ablation-assisted grinding method for depth-layer control, the set pure mechanical grinding depth δ 纯 Within the range of 40-60 μm. Depth of pure mechanical grinding δ 纯 If the depth is too small, the thickness of the molten solidified layer may exceed the machining allowance, while the depth of pure mechanical grinding δ... 纯 An excessively large value will affect processing efficiency, reducing the depth of pure mechanical grinding δ. 纯 Setting the size within the 40-60μm range allows for a good balance between processing quality and processing efficiency.

[0018] Furthermore, in order to balance processing efficiency and processing quality, the aforementioned discharge ablation-assisted grinding method with layered grinding depth control sets a purely mechanical single-layer grinding depth δ. 单 Within the range of 1-5μm.

[0019] Furthermore, preferably, in the aforementioned discharge ablation-assisted grinding method for depth-layer control, the value range of the exponential constant n is ⅓≤n≤⅔. If n is too small, the grinding depth variation will be small, the processing adjustment will be insignificant, and the processing efficiency will be affected. If n is too large, the grinding depth variation will be too large, affecting the processing quality. Taking n within the above range can better balance processing efficiency and processing quality.

[0020] Furthermore, preferably, in the aforementioned discharge ablation-assisted grinding method with layered grinding depth control, the reference grinding force F0 is 60-80% of the grinding force value when the grinding depth is the target grinding depth δ0 under the same grinding parameters and without discharge ablation (i.e., pure mechanical grinding); the target grinding depth δ0 is in the range of 1-20 μm. The target grinding depth δ0 is determined according to the workpiece material and processing parameters and is an expected value. Based on the characteristics of discharge ablation-assisted grinding, since the single-layer grinding depth is relatively small, during the wheel feed process, the abrasive grains, under rotational action, perform grinding action on the softened matrix metal and molten solidified layer softened by discharge ablation, achieving effective removal. Therefore, the average grinding force is significantly lower than that of pure mechanical grinding. Depending on the processing material and pulse parameters, the average grinding force varies within a certain range, generally being 60%-80% of that in pure grinding. Therefore, setting the reference grinding force F0 within 60%-80% of the grinding force in pure grinding is more suitable.

[0021] Furthermore, preferably, in the aforementioned discharge ablation-assisted grinding method with layered grinding depth control, the first layer grinding depth δ1 can be equal to the target grinding depth δ0. During processing, the first layer grinding depth δ1 can be taken near the target grinding depth δ0. Specifying that the first layer grinding depth δ1 is equal to the target grinding depth δ0 is beneficial for process design.

[0022] Furthermore, preferably, in the aforementioned discharge ablation-assisted grinding method for controlling grinding depth and layering, during the pure mechanical grinding process, the system determines whether the molten and solidified layer has been completely removed based on the real-time grinding force; if the grinding force is significantly lower than the pure grinding force F... 止 If the surface still has an incompletely removed molten and solidified layer, pure mechanical grinding should continue; when the grinding force during the processing of one layer remains close to the pure grinding force F... 止 If the molten solidified layer is completely removed, the processing is terminated; wherein, the pure grinding force F 止 Under the same grinding parameters, assuming the material is not subjected to electrical discharge ablation, the grinding depth is δ. 单The grinding force value at that time. Therefore, the molten and solidified layer on the workpiece surface can be completely removed, and this is easy to implement. Furthermore, in a purely mechanical grinding process, if the grinding force in one layer is relatively greater than the pure grinding force F... 止 If the deviation does not exceed 2%, it is determined that the molten solidified layer has been completely removed. Attached Figure Description

[0023] Figure 1 This is a flowchart illustrating the grinding depth layering control in the method of the present invention.

[0024] Figure 2 This is a schematic diagram of the overall experimental system according to an embodiment of the present invention;

[0025] Figure 3 This is a schematic diagram illustrating the principle of grinding depth layering control in the method of this invention;

[0026] Figure 4 The graph shows a comparison of the efficiency of discharge ablation-assisted grinding using the traditional average layering method (Comparative Experiment 1) and the layering control method of the present invention (Comparative Experiment 2).

[0027] Figure 5 These are comparative images of the morphology of the processed workpiece under a white light interferometer in this embodiment; Detailed Implementation

[0028] The technical solution of the present invention will be further described in detail below through specific embodiments and with reference to the accompanying drawings, but this should not be construed as limiting the present invention. Contents not described in detail in the following embodiments are all common knowledge in the art or can be implemented using conventional technical means in the art.

[0029] Example (see) Figure 1-5 ):

[0030] When using the discharge ablation-assisted grinding method with layered grinding depth control, the grinding depth of a single layer is calculated and adjusted during processing based on the average grinding force value of the upper layer. The single-layer cutting depth is adjustable within the range of 1μm-20μm. During the discharge ablation-assisted grinding process, the grinding wheel feeds at a constant rotational speed and transverse velocity, efficiently ablating and removing the workpiece material in this layer. Simultaneously, it grinds away part of the molten and solidified layer. Then, using the processing time of this layer as the sampling period and the real-time grinding force of this layer as the sampling signal, the average grinding force of this layer is obtained. The obtained average grinding force is compared with the set reference grinding force F0 to obtain a scaling factor as the basis for grinding depth adjustment, thereby adjusting the grinding depth of the next layer.

[0031] See Figure 1 During processing, the grinding depth δ1 of the first layer is a fixed value within the range of 1μm-20μm, and the grinding depth δ of the (i+1)th layer is... i+1The sampling period T is determined by the processing state of the previous layer, starting from the grinding of the i-th layer and ending at the grinding of that layer. i In T i Within a given time period, the real-time grinding force value is sampled, and T is calculated using a microprocessor. n The average grinding force over time. Calculated using the formula K. i =(F0÷F i ) n The scaling factor K was calculated. i The exponential constant n = 1 / 3 represents the grinding depth δ of the (i+1)th layer. i+1 Adjusted to ki•δ i .

[0032] When the overall machining is close to the target size (machining allowance less than 50μm), the oxygen and pulse power are turned off, and pure mechanical grinding is switched to continue. The grinding depth is set to a constant 2μm, and layer grinding continues. At the same time, the system judges whether the molten and solidified layer has been completely removed based on the real-time grinding force. If the grinding force is significantly lower than the pure grinding force F thereafter, 止 (Grinding force at a pure grinding depth of 2μm under the same parameter conditions, obtained experimentally), indicates that there is still an incompletely removed molten and solidified layer on the surface, and pure mechanical grinding should continue; when the grinding force during the processing of one layer remains close to the pure grinding force F, 止 If the melted and solidified layer has been completely removed, the processing is terminated.

[0033] The present invention will be further explained below with reference to processing experiments and comparative experiments. The processing parameters are shown in Table 1 below.

[0034] Table 1: Processing Parameters

[0035] project content workpiece material YG8 cemented carbide, dimensions: 16mm × 16mm × 4.5mm Power supply method Positive polarity processing grinding wheel 800# CBN, metallic copper binder; rotation speed 1500 r / min, transverse feed speed 30 mm / s working medium Water and oxygen mixture Pulse width: interpulse width 150μs: 120μs Current 5A oxygen pressure 0.5MPa water pressure 0.15MPa

[0036] Processing experiment of this invention:

[0037] The discharge ablation-assisted grinding method of the present invention was used for machining, and the experimental system is as follows: Figure 2 The processing parameters are shown in Table 1. The baseline grinding force F0 is set to 70N (target grinding depth δ0 is 2μm, obtained experimentally as F0=70N), the first layer grinding depth δ1 is 2μm, and the exponential constant n=1 / 3. During processing, the system continuously adjusts the grinding depth, switching to pure mechanical grinding when the machining allowance is less than 50μm. Before the end of processing, the state of the molten and solidified layer is judged in real time through the grinding force signal until the grinding force relative to the pure grinding force F in one layer of processing is determined. 止 The deviation never exceeds 2% (grinding force obtained from experiments when grinding to a depth of 2μm using pure mechanical grinding). 止 =85N), stop processing, the white light interference pattern on the material surface after processing is as follows: Figure 5 As shown in (b).

[0038] Comparative Experiment 1:

[0039] use Figure 2 The experimental system shown was used for processing according to the process parameters listed in Table 1. Specifically, a conventional constant-speed feed and constant-depth grinding layer method was employed for discharge ablation-assisted grinding, with a single-layer grinding depth of 2 μm. The white light interference pattern of the processed material surface is shown below. Figure 5 As shown in (a).

[0040] from Figure 5 As can be seen, in Comparative Experiment 1, the surface of the material after processing exhibits ablation pits caused by electrical discharge erosion, and these pits are not completely removed. In contrast, the surface of the material processed using the method of this invention does not show any ablation pits; its surface morphology only shows grooves created by abrasive mechanical removal.

[0041] Comparative Experiment 2:

[0042] Comparative Experiment 2 used the same method of layered control of grinding depth as described in this invention, but without the pure mechanical grinding step.

[0043] The comparison graph of processing efficiency between Experiment 1 and Experiment 2 is shown below. Figure 4 As shown in the figure. Experiments show that the grinding depth layer control method of the present invention can improve processing efficiency.

[0044] The foregoing general description of the invention and its specific embodiments should not be construed as a limitation on the technical solution of the invention. Those skilled in the art, based on the disclosure of this application, can add, reduce, or combine the disclosed technical features in the foregoing general description and / or specific embodiments (including examples) without departing from the constituent elements of the invention, to form other technical solutions within the scope of protection of this application.

Claims

1. A discharge ablation assisted grinding machining method of deep layer control, characterized by, The method comprises the following steps: First step: setting the first layer grinding depth δ1, the reference grinding force F0, the pure mechanical grinding depth δ 纯 , the pure mechanical single layer grinding depth δ 单 , the numerical value of the grinding wheel speed, the grinding wheel transverse feed speed and the index constant n, 0 < n < 1; Second step: first layer discharge ablation assisted grinding; the first layer grinding time is taken as a sampling period, the grinding force during the first layer grinding is taken as a sampling signal, and the average grinding force F1 of the first layer processing is calculated by using a processor after the first layer grinding is completed; Third step: compare the average grinding force F1 of the first layer processing with the set reference grinding force F0, get the proportion factor K1, multiply the first layer grinding depth δ1 by the proportion factor K1 to get the second layer grinding depth δ2; wherein the proportion factor K1=F0÷F1 n ; Fourth step: second layer discharge ablation assisted grinding is performed by using the obtained second layer grinding depth δ2; the second layer grinding time is taken as a sampling period, the grinding force during the second layer grinding is taken as a sampling signal, and the average grinding force F2 of the second layer processing is calculated by using a processor after the second layer grinding is completed; Fifth step: compare the average grinding force F2 of the second layer processing with the set reference grinding force F0, get the proportion factor K2, multiply the second layer grinding depth δ2 by the proportion factor K2 to get the third layer grinding depth δ3; wherein the proportion factor K2=(F0÷F2) n ; Sixth step: in this way, until the remaining machining allowance is less than the set pure mechanical grinding depth δ 纯 , turn to pure mechanical grinding; the pure mechanical grinding process is in the set pure mechanical single-layer grinding depth δ 单 Continue to remove the melted and solidified layer on the surface of the workpiece by layered grinding; In the pure mechanical grinding process, the system judges whether the melted and solidified layer has been completely removed according to the real-time grinding force; if the grinding force is obviously lower than the pure grinding force F 止 , it indicates that the melted and solidified layer is not completely removed on the surface, and the pure mechanical grinding is continued; when the grinding force in a layer of processing continuously approaches the pure grinding force F 止 , it is determined that the melted and solidified layer has been completely removed, and the processing process is terminated; wherein the pure grinding force F 止 is the grinding force value when the grinding depth is δ 单 under the same processing conditions without the discharge ablation of the material.

2. The method of deep layer controlled discharge ablation assisted grinding machining according to claim 1, characterized in that: The set grinding wheel rotating speed is in the range of 50-3000 rpm, and the set grinding wheel transverse feeding speed is in the range of 1 mm / s-50 mm / s.

3. The deep grinding layer controlled electrical discharge assisted grinding machining method according to claim 1, characterized in that: The set first layer grinding depth δ1 is in the range of 1-20 μm.

4. The deep grinding, layer-by-layer controlled discharge machining method according to claim 1, characterized in that: Set mechanical grinding depth δ 纯 In the range of 40-60 μm.

5. The deep grinding, layer-by-layer controlled discharge machining method according to claim 1, characterized in that: Set pure mechanical single-layer grinding depth δ 单 In the range of 1-5 μm.

6. The deep grinding, layer-by-layer controlled discharge chamfering process of claim 1, wherein: The value range of the index constant n is 1 / 3≤n≤2 / 3.

7. The method of deep layer controlled discharge chamfering assisted grinding according to claim 1, wherein: The reference grinding force F0 is 60-80% of the grinding force value when the grinding depth is the target grinding depth δ0 under the same processing condition and without discharge ablation; and the target grinding depth δ0 is in the range of 1-20 μm.

8. The method of depth-of-layer controlled electro-discharge abrasive machining according to claim 7, wherein: The first layer grinding depth δ1 is equal to the target grinding depth δ0.

9. The method of claim 8, wherein: In the pure mechanical grinding process, if the deviation of the grinding force in a layer of processing relative to the pure grinding force F 止 is always less than 2%, it is determined that the molten solidification layer has been completely removed.

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