Method for measuring the maximum depth of continuous etch pits under uninterrupted electrical discharge single pulse

Abstract

This invention discloses a method for measuring the maximum depth of continuous etch pits under uninterrupted single-pulse electrical discharge machining (EDM). The invention derives the maximum depth of etch pits when the EDM fluid is free of mixed powder and the workpiece is stationary by performing single-pulse etching trials on the workpiece. Then, by performing single-pulse etching trials on the workpiece with mixed powder in the EDM fluid and the workpiece stationary, the maximum depth of a single etch pit is derived when the EDM fluid contains mixed powder and the workpiece is moving. Finally, the maximum depth of all but the first etch pit in a plurality of consecutive etch pits is derived when the EDM fluid contains mixed powder and the workpiece is moving. This invention provides data for measuring the surface roughness of workpieces subjected to uninterrupted single-pulse etching under different discharge voltages, discharge currents, discharge times, or workpiece materials.

Description

Technical Field

[0001] This invention belongs to the field of electrical discharge machining, specifically relating to a method for measuring the maximum depth of continuous etch pits under uninterrupted single pulse electrical discharge machining. Background Technology

[0002] Electrical discharge machining (EDM) is widely used in the machining of molds and parts, and surface roughness is a key process indicator. The surface roughness of an EDM surface primarily depends on the maximum depth of the etched pits formed during EDM, and the roughness value can be simply considered to be directly proportional to the maximum pit depth. However, changes to any parameter (such as discharge voltage, discharge current, discharge time, presence or absence of powder mixing in the EDM fluid, and the volume ratio of the mixed powder) have a significant impact on the maximum pit depth. Furthermore, there are currently few methods for measuring the maximum depth of single-pulse etching, especially for continuous single-pulse etching. Therefore, it is necessary to design a method for measuring the maximum depth of continuous single-pulse etching to facilitate subsequent calculations of EDM surface roughness and to integrate with relevant parameters for calculating EDM surface roughness under different parameters. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of existing technologies and propose a method for measuring the maximum depth of continuous etch pits under uninterrupted electrical discharge single pulse.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] The present invention provides a method for measuring the maximum depth of continuous etch pits under uninterrupted electrical discharge single pulse, as detailed below.

[0006] Step 1: Set the discharge time, discharge voltage, and discharge current for the single-pulse etching trial process.

[0007] Step 2: With the EDM fluid free of mixed powder and the workpiece stationary, perform a single-pulse etching test on the workpiece to obtain an etch pit in the case of a single stationary workpiece. The etch pit in the case of a stationary workpiece is spherical. Measure the radius a1 of the top arc and the maximum depth h1 of the etch pit in the case of a single stationary workpiece. Then calculate the volume V1 of the etch pit in the case of a single stationary workpiece. Finally, calculate the work dissipation W of a single pulse in the case of a free EDM fluid. loss ;

[0008] W loss =UIt-V1g

[0009] In the formula, U is the discharge voltage, I is the discharge current, t is the discharge time, and g is the phase transformation heat of the workpiece material.

[0010] Step 3: Under the condition that the EDM fluid is free of mixed powder and the workpiece moves at a preset speed, perform a single-pulse etching test on the workpiece to obtain an etching pit under the condition of workpiece movement. The etching pit under the condition of workpiece movement is composed of half of a spherical crown and a semi-elliptical cone with the central section of the spherical crown as the base.

[0011] Under the same environmental conditions, the volume V' of the etch pit when a single workpiece is moving is equal to the volume V1 of the etch pit when a single workpiece is stationary. The relationship between the radius a' of the top arc and the maximum depth h' of the etch pit when a single workpiece is moving is the same as the relationship between the radius a1 of the top arc and the maximum depth h1 of the etch pit when a single workpiece is stationary. Therefore, the following relationship is used to express the relationship:

[0012] a=εh

[0013] In the formula, a and h are the radius and maximum depth of the top arc of the etched pit, respectively, and ε is a coefficient;

[0014] The value of coefficient ε is calculated based on the radius a1 of the top arc of the etch pit and the maximum depth h1 when the workpiece is stationary. Then, the relationship between the radius a' of the top arc of the etch pit and the maximum depth h' when a single workpiece moves is obtained. Combined with the volume V1 of the etch pit, the maximum depth h' of the etch pit when a single workpiece moves is calculated using the volume formula of the etch pit when a single workpiece moves.

[0015] Step 4: Prepare n portions of EDM fluid containing the same powder mix but with different volume ratios, where n ≥ 5; then repeat Step 2 n times, each time replacing the unmixed EDM fluid with EDM fluid containing the same powder mix but with different volume ratios, thereby obtaining the dissipation work W of a single pulse for n portions of EDM fluid containing the same powder mix but with different volume ratios. loss-mixed ;

[0016] The dissipation work W of each single pulse in the case of mixed powder in the electrical discharge fluid loss-mixed The volume ratio of each powder mixture and the dissipation work W of a single pulse in the case of no powder mixing in step two of the EDM fluid. loss By performing fitting, the dissipation work W of a single pulse in the EDM fluid containing mixed powder under the same environmental conditions can be obtained. loss-mixed The volume ratio of mixed powders and the dissipation work W of a single pulse in the case of no powder mixing in the EDM fluid. loss The relationship between them.

[0017] Step 5: Based on the set powder mixing volume ratio, calculate the dissipation work W of a single pulse in the EDM fluid when the powder is mixed. loss-mixed The volume ratio of mixed powder and the dissipation work W of a single pulse in the case of no powder mixing in the EDM fluid. lossThe relationship between the two is used to calculate the work function W of a single pulse in the EDM fluid with a corresponding powder mixing volume ratio. loss-mixed ,and

[0018] W loss-mixed =UIt-V”g

[0019] In the formula, V” represents the volume of an etch pit in a single EDM fluid containing mixed powder.

[0020] Next, calculate the volume V” of a single etch pit in the EDM fluid with the corresponding powder mixing ratio, which is the volume of a single etch pit in the EDM fluid with the corresponding powder mixing ratio and the workpiece moving. Then, based on the relationship a=εh and the volume of a single etch pit in the EDM fluid with the corresponding powder mixing ratio, calculate the maximum depth h2 of a single etch pit in the EDM fluid with the corresponding powder mixing ratio and the workpiece moving using the formula for the volume of a single etch pit in the EDM fluid with the corresponding powder mixing ratio and the workpiece moving.

[0021] When the EDM fluid contains powder with a corresponding volume ratio and the workpiece moves at a preset speed, if a continuous single-pulse etching trial is performed, multiple consecutive etching pits are obtained under the condition of workpiece movement. Starting from the second etching pit, the center of each etching pit is the vertex of the semi-elliptical cone in the previous etching pit. Based on the calculated maximum depth h2 of a single etching pit under the condition of EDM fluid containing powder with a corresponding volume ratio and workpiece movement, the maximum depth h of the remaining etching pits (excluding the first one) among the multiple consecutive etching pits under the condition of EDM fluid containing powder with a corresponding volume ratio and workpiece movement is calculated.

[0022] Preferably, the volume of the etch pit in the single workpiece when it is stationary is

[0023]

[0024] Preferably, the dissipation work W of a single pulse in the absence of powder mixing in the electrical discharge fluid is... loss for

[0025] W loss =W input -W output

[0026] and

[0027] W input =UIt

[0028] W output =V1g

[0029] In the formula, W input W is the discharge energy of a single pulse. output This refers to the pulse heat generated in a single pulse.

[0030] Preferably, the same environmental conditions refer to the same discharge voltage, discharge current, discharge time, and workpiece material.

[0031] Preferably, the volume of the etched pit during the movement of the single workpiece is...

[0032]

[0033] In the formula, a' is the radius of the top arc of the etch pit when the workpiece moves, h' is the maximum depth of the etch pit when the workpiece moves, l is the distance the workpiece moves during the discharge time, and l = vt, where v is the translational speed of the workpiece.

[0034] Preferably, the volume ratio of the mixed powders does not exceed 0.5.

[0035] Preferably, under the same environmental conditions, the dissipation work W of a single pulse in the case of mixed powder in the electrical discharge fluid is... loss-mixed The volume ratio of mixed powders and the dissipation work W of a single pulse in the case of no powder mixing in the EDM fluid. loss The relationship is

[0036] W loss-mixed =(λe) βc ×W loss

[0037] In the formula, λ and β are both coefficients, and c is the volume ratio of the mixed powder.

[0038] Preferably, the maximum depth h” of the multiple consecutive etch pits (excluding the first one) in the case of mixed powder in the EDM fluid and workpiece movement is:

[0039]

[0040] The present invention has the following beneficial effects:

[0041] 1. This invention obtains relevant data by performing single-pulse etching trials on a stationary workpiece under set environmental conditions. It further derives the maximum depth of the etching pit when a single workpiece moves, and then further derives the maximum depth of the remaining etching pits (excluding the first one) among multiple consecutive etching pits when the workpiece moves. This provides data for the surface roughness of workpieces subjected to subsequent continuous single-pulse etching. Specifically, this invention performs single-pulse etching trials on a workpiece with no mixed powder in the EDM fluid and the workpiece stationary. It determines the coefficient values ​​of the relationship between the radius of the top arc of the etching pit and the maximum depth. From an energy perspective, it establishes a formula for calculating the dissipation work of a single pulse under no mixed powder in the EDM fluid, providing data for deriving the maximum depth of a single etching pit under no mixed powder in the EDM fluid and when the workpiece moves. Furthermore, this invention performs single-pulse etching trials on a workpiece with different mixed powder volume ratios in the EDM fluid and the workpiece stationary, obtaining the dissipation work of a single pulse under different mixed powder volume ratios. This work is then fitted to obtain... The relationship between the dissipation work of a single pulse in the EDM fluid containing mixed powder and the dissipation work of a single pulse in the EDM fluid without mixed powder was obtained. A calculation formula for the dissipation work of a single pulse in the EDM fluid containing mixed powder was also established. This provides data for deriving the calculation of the maximum depth of the etching pit when the EDM fluid contains mixed powder and the workpiece is moving. Furthermore, it provides data for calculating the maximum depth of the remaining etching pits (excluding the first one) in multiple consecutive etching pits when the EDM fluid contains mixed powder with a corresponding volume ratio and the workpiece is moving. This provides a data basis for the surface roughness of the workpiece after continuous single-pulse etching.

[0042] 2. Based on discharge voltage, discharge current, discharge time, workpiece material, and etching pit volume, this invention establishes a formula for calculating the work dissipation of a single pulse under conditions of no powder mixing and powder mixing in the EDM fluid. This provides data for the surface roughness of workpieces subjected to uninterrupted single-pulse etching under different discharge voltages, discharge currents, discharge times, or workpiece materials. Attached Figure Description

[0043] Figure 1 A schematic diagram of an etching pit on a single workpiece when it is stationary;

[0044] Figure 2 A schematic diagram of etching pits in the case of a single moving workpiece;

[0045] Figure 3 This is a schematic diagram of etching pits in the case of multiple consecutive workpieces moving. Detailed Implementation

[0046] The present invention will now be further described with reference to the accompanying drawings.

[0047] The present invention provides a method for measuring the maximum depth of continuous etch pits under uninterrupted single-pulse electrical discharge machining, as detailed below:

[0048] Step 1: Set the discharge time, discharge voltage, and discharge current for the single-pulse etching trial process.

[0049] Step 2: With the EDM fluid free of mixed powder and the workpiece stationary, perform a single-pulse etching trial on the workpiece to obtain a single etching pit under stationary conditions. The etching pit under stationary conditions is spherical, as shown below. Figure 1 As shown; the radius a1 and maximum depth h1 of the top arc of the etching pit of a single workpiece under static conditions are measured using computer image recognition technology; then the volume V1 of the etching pit of a single workpiece under static conditions, i.e., the volume of the spherical cap, is calculated; then the dissipation work W of a single pulse of EDM fluid without powder mixing is calculated. loss The volume of the etching pit for a single workpiece when it is stationary is...

[0050]

[0051] The dissipation work W of a single pulse in an EDM fluid without powder mixing loss for

[0052] W loss =W input -W output

[0053] W input =UIt

[0054] W output =V1g

[0055] In the formula, W input Let U be the discharge energy of a single pulse, I be the discharge voltage, t be the discharge time of a single pulse, and W be the discharge energy of a single pulse. output denoted as , where is the pulse heat generated by a single pulse, and g is the phase transition heat of the workpiece material.

[0056] During the single-pulse etching trial, the electrode moves downward to the predetermined lowest point and begins to discharge. Then, the electrode moves upward, and the electro-discharge fluid flowing between the electrode and the workpiece carries away the etched solid particles until the electrode discharge ends.

[0057] Step 3: With no powder mixing in the EDM fluid and the workpiece moving at a preset speed, perform a single-pulse etching trial on the workpiece to obtain an etching pit under the condition of workpiece movement. The etching pit under workpiece movement consists of half of a spherical cap and a semi-elliptical cone with the central section of the spherical cap as its base. Figure 2 As shown.

[0058] Under the same environmental conditions, regardless of whether the workpiece moves, the dissipation work generated by each single pulse is equal. Therefore, under the same environmental conditions, the etching pit volume V' of a single moving workpiece is equal to the etching pit volume V1 of a single stationary workpiece. Here, the same environmental conditions refer to the same discharge voltage, discharge current, discharge time, and workpiece material.

[0059] Meanwhile, under the same environmental conditions, the relationship between the radius a' and the maximum depth h' of the top arc of the etching pit when a single workpiece is moving is the same as the relationship between the radius a1 and the maximum depth h1 of the top arc of the etching pit when a single workpiece is stationary. Therefore, the following formula is used to express the relationship between the radius and the maximum depth of the top arc of the etching pit:

[0060] a=εh

[0061] In the formula, a and h are the radius and maximum depth of the top arc of the etching pit, respectively, and ε is a coefficient with a value range of 1.20 to 1.40. The ratio of the radius of the top arc to the maximum depth of the etching pit after the metal workpiece is subjected to and diffused by the electric arc energy at a certain point is affected by the ratio of the axial heat transfer rate to the radial heat transfer rate. The ratio of the axial heat transfer rate to the radial heat transfer rate of the metal workpiece is constant, that is, the value of ε is constant and is not affected by whether the workpiece moves or whether the EDM fluid contains mixed powder.

[0062] Based on the radius a1 of the top arc of the etching pit and the maximum depth h1 of the single workpiece when stationary, obtained in step two, the value of the coefficient ε is calculated. Then, the relationship between the radius a' of the top arc of the etching pit and the maximum depth h' of the single workpiece when moving is obtained. Based on the relationship between the radius a' of the top arc of the etching pit and the maximum depth h' of the single workpiece when moving, and the volume V1 of the etching pit under the same environmental conditions obtained in step two, the maximum depth h' of the etching pit when moving is calculated using the volume formula of the etching pit when moving (the formula for the sum of the volumes of a hemispherical cap and a semi-elliptical cone).

[0063] In the case of a single workpiece movement, the volume of the etching pit is...

[0064]

[0065] In the formula, a' and h' are the radius and maximum depth of the top arc of the etching pit when the workpiece moves, l is the distance the workpiece moves during the discharge time, and l = vt, where v is the translation speed of the workpiece.

[0066] Step 4: Prepare five portions of EDM fluid containing the same powder mix but with different powder volume ratios (the ratio of the mixed powder to the EDM fluid after adding the mixed powder). In the actual preparation, the powder volume ratio should not exceed 0.5. Then, repeat Step 2 five times, each time replacing the unmixed EDM fluid with an EDM fluid containing the same powder mix but with different powder volume ratios. This will yield five portions of single-pulse dissipation work W under the conditions of EDM fluids containing the same powder mix but with different powder volume ratios. loss-mixed ;

[0067] The dissipation work W of each single pulse in the case of mixed powder in the electrical discharge fluid loss-mixed The volume ratio of each powder mixture and the dissipation work W of a single pulse in the case of no powder mixing in step two of the EDM fluid. loss By performing fitting, the dissipation work W of a single pulse in the EDM fluid containing mixed powder under the same environmental conditions can be obtained. loss-mixed The volume ratio of mixed powders and the dissipation work W of a single pulse in the case of no powder mixing in the EDM fluid. loss The relational expression is

[0068] W loss-mixed =(λe) βc ×W loss

[0069] In the formula, λ and β are both coefficients, and c is the volume ratio of the mixed powder.

[0070] Step 5: Based on the set powder mixing volume ratio, calculate the dissipation work W of a single pulse in the EDM fluid when the powder is mixed. loss-mixed The volume ratio of mixed powder and the dissipation work W of a single pulse in the case of no powder mixing in the EDM fluid. loss The relationship between the two is used to calculate the work function W of a single pulse in the EDM fluid with a corresponding powder mixing volume ratio. loss-mixed ,and

[0071] W loss-mixed =UIt-V”g

[0072] In the formula, V” represents the volume of an etch pit in a single EDM fluid containing mixed powder.

[0073] Next, calculate the volume V” of a single etch pit in the EDM fluid with the corresponding powder mixing ratio, which is the volume of the etch pit in the EDM fluid with the corresponding powder mixing ratio and the workpiece moving. Then, based on the relationship a=εh (here a2=εh2) and the volume of the etch pit in the EDM fluid with the corresponding powder mixing ratio, calculate the maximum depth h2 of the etch pit in the EDM fluid with the corresponding powder mixing ratio and the workpiece moving by using the formula for the volume of the etch pit in the case of a single workpiece moving (substitute V” for V′ and h2 for h’).

[0074] When the EDM fluid contains powders of a specific volume ratio and the workpiece moves at a preset speed, continuous single-pulse etching will result in multiple etch pits under continuous workpiece movement. Starting from the second etch pit, the center of each pit is the vertex of the semi-elliptical cone in the previous etch pit. Figure 3 As shown.

[0075] Based on the calculated maximum depth h2 of a single etch pit in the EDM fluid with a corresponding powder mixing ratio and workpiece movement, the maximum depth h" of each etch pit in multiple consecutive etch pits in the same EDM fluid with a corresponding powder mixing ratio and workpiece movement is calculated. This provides data for determining the surface roughness of the workpiece during continuous single-pulse etching. Specifically, the maximum depth h" of each etch pit in multiple consecutive etch pits (excluding the first one) in the EDM fluid with mixed powder and workpiece movement is defined as follows:

[0076]

[0077] in, Figure 3 The length of d in the middle can be approximated as 1.2h2.

Claims

1. A method for measuring the maximum depth of continuous etched pits under uninterrupted electrical discharge single pulse, characterized in that: Specifically as follows: Step 1: Set the discharge time, discharge voltage, and discharge current for the single-pulse etching trial process; Step 2: With the EDM fluid free of mixed powder and the workpiece stationary, perform a single-pulse etching test on the workpiece to obtain an etch pit in the case of a single stationary workpiece. The etch pit in the case of a stationary workpiece is spherical. Measure the radius a1 of the top arc and the maximum depth h1 of the etch pit in the case of a single stationary workpiece. Then calculate the volume V1 of the etch pit in the case of a single stationary workpiece. Finally, calculate the work dissipation W of a single pulse in the case of a free EDM fluid. loss ; In the formula, U is the discharge voltage, I is the discharge current, t is the discharge time, and g is the phase transformation heat of the workpiece material; Step 3: Under the condition that the EDM fluid is free of mixed powder and the workpiece moves at a preset speed, perform a single-pulse etching test on the workpiece to obtain an etching pit under the condition of workpiece movement. The etching pit under the condition of workpiece movement is composed of half of a spherical crown and a semi-elliptical cone with the central section of the spherical crown as the base. Under the same environmental conditions, the volume V' of the etch pit when a single workpiece is moving is equal to the volume V1 of the etch pit when a single workpiece is stationary. The relationship between the radius a' of the top arc of the etch pit and the maximum depth h' when a single workpiece is moving is the same as the relationship between the radius a1 of the top arc of the etch pit and the maximum depth h1 when a single workpiece is stationary. Therefore, the following relationship is used to express the relationship: In the formula, a and h are the radius and maximum depth of the top arc of the etched pit, respectively, and ε is a coefficient; The value of coefficient ε is calculated based on the radius a1 of the top arc of the etch pit and the maximum depth h1 when the workpiece is stationary. Then, the relationship between the radius a' of the top arc of the etch pit and the maximum depth h' when a single workpiece moves is obtained. Combined with the volume V1 of the etch pit, the maximum depth h' of the etch pit when a single workpiece moves is calculated using the volume formula of the etch pit when a single workpiece moves. Step 4: Prepare n portions of EDM fluid containing the same powder mix but with different volume ratios, where n ≥ 5; then repeat Step 2 n times, each time replacing the unmixed EDM fluid with EDM fluid containing the same powder mix but with different volume ratios, thereby obtaining the dissipation work W of a single pulse for n portions of EDM fluid containing the same powder mix but with different volume ratios. loss-mixed ; The dissipation work W of each single pulse in the case of mixed powder in the electrical discharge fluid loss-mixed The volume ratio of each powder mixture and the dissipation work W of a single pulse in the case of no powder mixing in step two of the EDM fluid. loss By performing fitting, the dissipation work W of a single pulse in the EDM fluid containing mixed powder under the same environmental conditions can be obtained. loss-mixed The volume ratio of mixed powders and the dissipation work W of a single pulse in the case of no powder mixing in the EDM fluid. loss Relationships; Step 5: Based on the set powder mixing volume ratio, calculate the dissipation work W of a single pulse in the EDM fluid when the powder is mixed. loss-mixed The volume ratio of mixed powder and the dissipation work W of a single pulse in the case of no powder mixing in the EDM fluid. loss The relationship between the two is used to calculate the work function W of a single pulse in the EDM fluid with a corresponding powder mixing volume ratio. loss-mixed ,and In the formula, V'' is the volume of an etch pit in a single EDM fluid containing mixed powder; Next, calculate the volume V'' of a single etch pit when the EDM fluid contains the corresponding powder volume ratio, which is the volume of an etch pit when the EDM fluid contains the corresponding powder volume ratio and the workpiece is moving; then, according to The relationship between the volume of the etching pit and the volume of the etching pit in the EDM fluid with the corresponding mixing ratio are used to calculate the maximum depth h2 of the etching pit in the EDM fluid with the corresponding mixing ratio and the volume of the etching pit in the case of workpiece movement. When the EDM fluid contains powder with a corresponding volume ratio and the workpiece moves at a preset speed, if a continuous single-pulse etching trial is performed, multiple consecutive etching pits are obtained under the condition of workpiece movement. Starting from the second etching pit, the center of each etching pit is the vertex of the semi-elliptical cone in the previous etching pit. Based on the calculated maximum depth h2 of a single etching pit under the condition of EDM fluid containing powder with a corresponding volume ratio and workpiece movement, the maximum depth h'' of the remaining etching pits (excluding the first one) among the multiple consecutive etching pits under the condition of EDM fluid containing powder with a corresponding volume ratio and workpiece movement is calculated.

2. The method for measuring the maximum depth of continuous etched pits under uninterrupted electrical discharge single pulse as described in claim 1, characterized in that: The volume of the etch pit when the single workpiece is stationary is 。 3. The method for measuring the maximum depth of continuous etched pits under uninterrupted electrical discharge single pulse as described in claim 1, characterized in that: The same environmental conditions refer to the same discharge voltage, discharge current, discharge time, and workpiece material.

4. The method for measuring the maximum depth of continuous etched pits under uninterrupted electrical discharge single pulse as described in claim 1, characterized in that: The volume of the etch pit during the movement of the single workpiece is In the formula, a' is the radius of the top arc of the etched pit when the workpiece moves, h' is the maximum depth of the etched pit when the workpiece moves, and l is the distance the workpiece moves during the discharge time. v is the translational speed of the workpiece.

5. The method for measuring the maximum depth of continuous etched pits under uninterrupted electrical discharge single pulse as described in claim 1, characterized in that: The volume ratio of the mixed powders shall not exceed 0.

5.

6. The method for measuring the maximum depth of continuous etched pits under uninterrupted electrical discharge single pulse as described in claim 1, characterized in that: Under the same environmental conditions, the dissipation work W of a single pulse in an electrical discharge fluid containing mixed powder is described. loss-mixed The volume ratio of mixed powders and the dissipation work W of a single pulse in the case of no powder mixing in the EDM fluid. loss The relationship is In the formula, λ and β are both coefficients, and c is the volume ratio of the mixed powder.

7. The method for measuring the maximum depth of continuous etched pits under uninterrupted electrical discharge single pulse as described in claim 1, characterized in that: The maximum depth h'' of the multiple consecutive etch pits, excluding the first one, in the case where the EDM fluid contains mixed powder and the workpiece is moving is... 。

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