External thread fastener forming method

Abstract

This application relates to the fields of metal additive manufacturing and fastener manufacturing technology, and particularly to a method for forming external threaded fasteners. This method acquires parameter information and reference parameter information of the part to be formed, calculates the thread structure correction coefficient using nominal diameter and pitch as core variables, and solves for the target laser power and target scanning speed based on the base laser power, base scanning speed, and thread structure correction coefficient. Combining the inherent parameters of the equipment, the target power and scanning speed are clamped to obtain the execution parameters, while simultaneously calculating the execution scanning interval and selecting the execution powder layer thickness. Selective laser melting is then used to complete the part printing. This method has few variables, making it easy to read and calculate. The dimensionless thread structure correction coefficient establishes a correlation between thread specifications and process parameters, enabling automatic parameter generation. The dual constraints of limiting the structure correction coefficient and clamping the equipment parameter range reduce the risk of parameters exceeding the process window and reduce manual setting work.

Description

Technical Field

[0001] This application relates to the fields of metal additive manufacturing and fastener manufacturing technology, and in particular to a method for forming external threaded fasteners. Background Technology

[0002] External threaded fasteners, including bolts, screws, studs, and other components, are widely used connecting elements in the fields of machinery, aerospace, transportation, and energy equipment. Selective laser melting technology achieves the direct forming of complex metal parts by melting metal powder layer by layer with a laser, making it ideal for manufacturing small batches, customized, and multi-specification fasteners.

[0003] In the existing selective laser melting process, for external thread fasteners with different nominal diameters and pitches, engineers usually directly reuse the same set of process parameters, or rely on the subjective experience of operators to adjust the laser power and scanning speed.

[0004] If fixed energy input parameters are applied directly, small-sized threads are prone to defects such as overmelting, powder adhesion, and tooth tip passivation, while large-sized fasteners will experience problems such as insufficient local fusion and poor forming stability. On the other hand, relying on manual experience to adjust parameters is greatly affected by subjective factors, making it difficult to control the forming quality of parts stably and making it difficult to manage process costs. Summary of the Invention

[0005] To address at least the above-mentioned technical problems existing in the prior art, this application provides a method for forming external threaded fasteners.

[0006] This application provides a method for forming external threaded fasteners, the method comprising the following steps: acquiring parameter information and reference parameter information of the external threaded fastener to be formed, and calculating a thread structure correction coefficient based on the parameter information of the external threaded fastener to be formed and the reference parameter information; wherein the parameter information includes at least the nominal diameter of the external thread and the external thread pitch, and the reference parameter information includes at least a reference nominal diameter, a reference pitch, and a thread structure sensitivity coefficient; acquiring the basic laser power and basic scanning speed in the basic process parameters of the reference part, and calculating the target laser power and target scanning speed based on the basic laser power, the basic scanning speed, and the thread structure correction coefficient; acquiring the inherent parameter information of the equipment, wherein the inherent parameter information of the equipment... The information includes at least the nominal laser spot diameter, scanning spacing coefficient, layer thickness coefficient, set of powder layer thicknesses allowed by the equipment, laser power range allowed by the equipment, and scanning speed range. Based on the target laser power, target scanning speed, laser power range, and scanning speed range, clamping is performed to obtain the execution laser power and execution scanning speed. The execution scanning spacing is calculated based on the nominal laser spot diameter and scanning spacing coefficient. The execution powder layer thickness is selected based on the layer thickness coefficient, the external thread pitch, and the set of powder layer thicknesses allowed by the equipment. Based on the execution laser power, execution scanning speed, execution scanning spacing, and execution powder layer thickness, the external thread fastener to be formed is printed using a selective laser melting method.

[0007] In some embodiments, before calculating the thread structure correction coefficient, the method further includes: obtaining a three-dimensional model of the external thread fastener to be formed; setting the thread axis of the external thread fastener to be formed to be parallel to the forming direction; and slicing the three-dimensional model as a single integral model.

[0008] In some embodiments, the method further includes: the thread structure correction coefficient is determined based on the nominal diameter of the external thread, the dimensional deviation of the external thread pitch relative to the reference nominal diameter and the reference pitch, and in combination with a preset thread structure sensitivity coefficient; the thread structure sensitivity coefficient is the sensitivity of the nominal diameter and pitch of the thread to the accuracy of the formed external thread structure.

[0009] In some embodiments, after calculating the thread structure correction coefficient, the method further includes: obtaining a lower limit and an upper limit of the structure correction coefficient, and performing a limiting process on the thread structure correction coefficient to obtain a limited structure correction coefficient.

[0010] In some embodiments, before the step of obtaining the parameter information and reference parameter information of the fastener to be formed with external thread, the method further includes: establishing a reference parameter information set, wherein the reference parameter information set stores the correspondence between external thread features and reference parameter information.

[0011] In some embodiments, the method for limiting the thread structure correction coefficient includes: limiting the thread structure correction coefficient between the lower limit of the structure correction coefficient and the upper limit of the structure correction coefficient; when the thread structure correction coefficient exceeds the boundary of the interval, taking the corresponding boundary value as the limited structure correction coefficient; when it is within the interval, retaining the original value.

[0012] In some embodiments, the method for calculating the target laser power and target scanning speed based on the base laser power, the base scanning speed, and the thread structure correction coefficient includes: adjusting the target laser power and the target scanning speed relative to the base parameters by matching the structural effect of the limited structural correction coefficient; wherein, if the limited structural correction coefficient increases, the target laser power increases compared to the base laser power, and the target scanning speed decreases compared to the base scanning speed; if the limited structural correction coefficient decreases, the target laser power decreases compared to the base laser power, and the target scanning speed increases compared to the base scanning speed.

[0013] In some embodiments, the method of clamping based on the target laser power, the target scanning speed, the laser power range, and the scanning speed range to obtain the executed laser power and the executed scanning speed includes: if the target laser power exceeds the allowable range of the laser power range, then limiting the executed laser power to a corresponding boundary value allowed by the device; if the target scanning speed exceeds the allowable range of the scanning speed range, then limiting the executed scanning speed to a corresponding boundary value allowed by the device; when the target laser power and the target scanning speed fall within the allowable ranges of the laser power range and the scanning speed range, respectively, the target laser power is used as the executed laser power, and the target scanning speed is used as the executed scanning speed.

[0014] In some embodiments, before the step of printing and forming the external thread fastener to be formed by selective laser melting, the method further includes: determining the actual processing energy value based on the executed laser power, the executed scanning speed, and in combination with the executed scanning interval and the executed powder layer thickness; and determining a reference processing energy value based on the base laser power, the base scanning speed, and in combination with the executed scanning interval and the executed powder layer thickness.

[0015] In some embodiments, the external threaded fastener includes at least one of bolts, screws, studs, set screws, and self-tapping screws.

[0016] This application provides a method for forming external threaded fasteners. It selects nominal diameter and pitch as parameters for fastener structural variation, resulting in a small number of variables and facilitating parameter reading and rapid calculation. By utilizing a dimensionless thread structure correction coefficient, it establishes a correlation between different specifications of external threaded fasteners and laser power and scanning speed, enabling automatic generation of forming process parameters. This solution employs dual constraints—thread structure correction coefficient limitation and equipment process parameter range clamping—to limit the calculated target process parameters within the equipment's executable range, reducing the risk of calculation results exceeding the material and equipment's basic process window and minimizing the workload of manual parameter setting. Attached Figure Description

[0017] The above and other objects, features, and advantages of exemplary embodiments of this application will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings. Several embodiments of this application are illustrated in the drawings by way of example and not limitation, in which: In the accompanying drawings, the same or corresponding reference numerals indicate the same or corresponding parts.

[0018] Figure 1 This is a flowchart illustrating the external thread fastener forming method provided in an embodiment of this application. Detailed Implementation

[0019] To make the objectives, features, and advantages of this application more apparent and understandable, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] Currently, when different specifications / models of external threaded fasteners are formed using selective laser melting technology, if uniform fixed parameters are always used, the differences in structural dimensions cannot be reflected. If redesign is required for different parameters, the design cost and time cost will increase significantly. Alternatively, relying on manual experience to set parameters one by one has a high degree of subjectivity and uncertainty.

[0021] This application provides a method for forming external threaded fasteners, based on a new method for determining forming parameters, to solve the aforementioned technical problems. For example... Figure 1 As shown, the method includes: The nominal diameter d and pitch p of the external thread of the fastener to be formed are used as structural input parameters, with reference to the nominal diameter d. r and reference pitch p rDimensionless transformation is performed, and the thread structure correction coefficient K is obtained by combining it with the pre-set thread structure sensitivity coefficient α; then, the lower limit K of the structure correction coefficient is used. min and upper limit of structural correction coefficient K max The thread structure correction factor K is limited to obtain the limited structure correction factor K. c Then, the structural correction coefficient K after the amplitude is limited is applied. c Calculate and determine the parameters that need to be executed.

[0022] For example, the external thread fastener to be formed is at least one of bolts, screws, studs, set screws, and self-tapping screws, or a fastening component with external threads.

[0023] The specific steps are as follows: Step S10: Obtain the parameter information of the external thread fastener to be formed; wherein, the parameter information includes at least the nominal diameter d of the external thread and the pitch p of the external thread.

[0024] In this embodiment, the forming of the external thread fastener is accomplished using selective laser melting. After the design of the external thread fastener is completed, all its information parameters are determined, and these parameters can be obtained from the three-dimensional model of the external thread fastener.

[0025] The nominal diameter d and pitch p of the external thread can be extracted from the 3D model and used as input for the subsequent calculation of the structural influence coefficient. The information obtained includes at least the nominal diameter d and pitch p of the external thread.

[0026] Step S20: Set the thread axis of the external thread fastener to be formed to be parallel to the forming direction, and slice the three-dimensional model as a single whole model.

[0027] It should be noted that the forming process parameters obtained by this invention have corresponding applicable prerequisites. The geometric processing prerequisites must be locked first before parameter calculations can be performed, ensuring that all subsequent parameter calculations are based on these specific forming conditions. Based on the information from the 3D model, setting the thread axis parallel to the forming direction can eliminate the problem of large-angle thread overhang and avoid the tooth collapse defect that cannot be overcome by parameter adjustment alone. Treating the 3D model as a single, unified model slice, without separating the threaded portion, shank, and head, ensures that the set of process parameters obtained from subsequent calculations can uniformly apply to the entire solid area of ​​the fastener.

[0028] At the same time, by relying on the three-dimensional model to define the solid processing area of ​​the part, it is easy to configure the calculated forming process parameters to the solid processing area, which is compatible with the slicing process of selective laser melting forming.

[0029] The aforementioned posture and slicing processing are prerequisites for the effective functioning of the parameter scheme of this invention. Therefore, this limitation should be completed after obtaining the three-dimensional model and before performing the calculation of thread-related process parameters. If the posture is adjusted or the model is split after the parameter calculation is completed, the parameter calculation logic of this invention will no longer be suitable for the actual machining conditions.

[0030] Step S30: Obtain reference parameter information, which includes at least the reference nominal diameter d. r Reference pitch p r And the thread structure sensitivity coefficient α, and the thread structure correction coefficient K is calculated based on the parameter information and reference parameter information of the fastener to be formed external thread.

[0031] The reference parameter information is a pre-set offline calculation reference information, not derived from the current external thread fastener to be formed. It is directly read and called during the actual machining of the part. The reference parameter information is used to obtain the relative dimensional deviation of the thread to be formed relative to the reference thread, and combined with the thread structure sensitivity coefficient α, the thread structure correction coefficient K is calculated.

[0032] The thread structure sensitivity coefficient α is the degree to which changes in the nominal diameter and pitch of the thread affect the accuracy of the formed external thread structure. It is a preset value used to convert thread size deviations into process adjustment ranges.

[0033] The thread structure correction factor K is based on the nominal diameter d of the external thread and the external thread pitch p relative to the reference nominal diameter d. r Reference pitch p r The dimensional deviation is determined by combining it with the preset thread structure sensitivity coefficient α.

[0034] Please refer to the following formula for details:

[0035] In the formula, K is the thread structure correction coefficient, α is the thread structure sensitivity coefficient, d is the nominal diameter of the external thread, p is the external thread pitch, and d r For reference to the nominal diameter, p r For reference pitch.

[0036] The thread structure sensitivity coefficient α is a pre-calibrated offline process coefficient. During the calibration process, multiple sets of external thread samples with different nominal diameters and pitches are selected, and selective laser melting forming tests are carried out under the same material and equipment conditions to detect the tooth profile, dimensional accuracy and forming defects of the formed external thread. The thread structure sensitivity coefficient α is obtained by fitting, so that the process parameters calculated based on the thread structure sensitivity coefficient α can obtain the required external thread forming quality within the target thread specification range.

[0037] The thread structure sensitivity coefficient α is matched with the material to be formed, the basic process conditions of the equipment, and the specification range of the external thread to be processed. When changing the forming material, altering the equipment process conditions, or processing threads outside the original specification range, this coefficient needs to be recalibrated. After the thread structure sensitivity coefficient α is calibrated, it is compared with the lower limit K of the corresponding structure correction coefficient. min Upper limit of structural correction coefficient K max It is used in conjunction with other components; the calibrated thread structure sensitivity coefficient α is directly called during part processing, without being solved in real time during part forming.

[0038] For example, a reference parameter information set can be established, storing the correspondence between external thread features and reference parameter information. The calibrated thread structure sensitivity coefficients are stored in the reference parameter information set, allowing direct retrieval of the corresponding thread structure sensitivity coefficient based on the specification range of the thread to be processed. The correspondence between external thread features and reference parameter information is pre-established; once the external thread fastener to be formed is determined, the matching reference parameter information is retrieved from the reference parameter information set according to the specification range of its thread.

[0039] Reference nominal diameter d r With reference pitch p r The reference thread feature used for parameter calculation in this invention is employed to determine the relative dimensional deviation of the external thread fastener to be formed relative to the reference thread. Reference nominal diameter d r Reference pitch p r The selection needs to be made from the current range of specifications of the external threaded fasteners to be formed. There are two selection approaches: one is to preset a reference specification, that is, to select a standard thread specification that is mature and commonly used in this specification range as the reference specification. The reference specification corresponds to the determination of basic process parameters such as basic laser power P0 and basic scanning speed v0; the other is to select an intermediate specification in the specification range as a reference, so that the positive and negative distribution of the dimensional deviations of most external threaded fasteners to be formed relative to the reference is balanced, so as to avoid excessive deviation of the structural influence coefficient and reduce the probability of amplitude truncation.

[0040] When the nominal diameter and pitch of the external thread fastener to be formed are consistent with the reference specifications, the relative dimensional deviation is zero, and the structural influence coefficient is equal to 1; under the condition that the upper and lower limits of the structural influence coefficient are not exceeded, the structural correction coefficient K after the limit is... c If the value is also 1, the basic process parameters are used directly for processing.

[0041] Step S40: Obtain the lower limit K of the structural correction factor min and upper limit of structural correction coefficient K max The thread structure correction factor K is then limited to obtain the limited structure correction factor K. c .

[0042] Lower limit of structural correction factor K min and upper limit of structural correction coefficient K max The process threshold obtained through pre-offline calibration is used in conjunction with the thread structure sensitivity coefficient α. During the calibration phase, forming tests are conducted using multiple sets of external thread samples to detect the forming quality of the thread under different structural influence coefficients. The range of structural influence coefficient values ​​that can yield qualified external threads is determined as K. min To K max When forming external threaded fasteners, the upper and lower limits of the calibrated structural influence coefficient can be read and obtained, without real-time calculation or experimental acquisition during the part processing.

[0043] The following formula is used for amplitude limiting:

[0044] In the formula, K min and K max These are the lower and upper limits of the structural correction coefficient, respectively; clip indicates that the result is restricted to the given upper and lower limits.

[0045] Applying a limiting process to the thread structure correction factor K means constraining the calculated result of the thread structure correction factor K to the lower limit K of the structure correction factor. min With upper limit of structural correction factor K max Within the defined numerical range. When the calculated thread structure correction coefficient K is greater than the upper limit K of the structure correction coefficient. max When, take the upper limit K of the structural correction factor. max K, as the structural correction coefficient after amplitude limiting c When the calculated thread structure correction coefficient K is less than the lower limit K of the structure correction coefficient min When, take the lower limit K of the structural correction factor. min K, as the structural correction coefficient after amplitude limiting c When the calculated thread structure correction coefficient K is within the interval formed by the lower and upper limits, the original value of the calculated thread structure correction coefficient K is directly retained as the structure correction coefficient K after the amplitude is limited. c This limiting constraint prevents excessive deviation of the thread to be processed from the reference specification, thus avoiding excessive subsequent process adjustments and preventing the generation of extreme process parameters that exceed the thread forming capability.

[0046] The purpose of limiting the structural influence coefficient is to constrain it within the reasonable range when the coefficient calculated based on thread size deviation deviates from the acceptable range. This prevents extreme process adjustments due to differences in thread specifications, thus avoiding subsequent process conditions that could lead to thread collapse or over-melting. This limitation is the first level of constraint, ensuring the feasibility of thread feature formation. A second level of clamping is then applied, taking into account both thread forming quality and equipment hardware limitations.

[0047] Step S50: Obtain the basic laser power P0 and basic scanning speed v0 from the basic process parameters of the reference part, and calculate the target laser power P based on the basic laser power P0, basic scanning speed v0 and thread structure correction coefficient K. t and target scanning speed v t .

[0048] The reference part's basic process parameters are a set of mature selective laser melting process parameters for external thread fasteners (reference parts) of corresponding reference specifications, which are obtained through pre-test calibration and used as a calculation benchmark for converting process parameters of external thread fasteners of different specifications.

[0049] Target laser power P t With target scanning speed v t The adjustment range of each relative to the basic parameter, and the structural correction coefficient K after limiting. c The structural impact effect is matched: where the structural correction coefficient K after limiting is... c If it increases, the target laser power P t Compared to the increase in basic laser power P0 and target scanning speed v t Compared to the base scan speed v0, the structural correction factor K decreases; c If it decreases, the target laser power P t Compared to the decrease in base laser power P0, the target scanning speed v t The speed is improved compared to the base scan speed v0.

[0050] The calculation formula is as follows:

[0051] In the formula, P t P0 is the target laser power, P0 is the base laser power, and K is the structure correction factor after limiting. c .

[0052]

[0053] In the formula, v t Let v0 be the target scan speed, v0 be the base scan speed, and K be the base scan speed. c This is the structural correction factor after amplitude limiting.

[0054] Step S60: Obtain the inherent parameter information of the equipment, which includes at least the nominal laser spot diameter d. b Scanning spacing coefficient λ h Layer thickness coefficient λ t The equipment's allowable powder layer thickness set T, laser power range, and scanning speed range are all specified. These inherent parameters characterize the hardware boundaries of the selective laser melting equipment and the pre-matched process configuration. They are determined before parameter calculations are performed on the external threaded fastener to be formed and do not change in real-time with thread specifications during part processing.

[0055] Wherein, the nominal laser spot diameter d b The allowable laser power range, scanning speed range, and allowable powder layer thickness T of the equipment are determined by the equipment's optical and mechanical hardware conditions and belong to the inherent hardware boundaries of the equipment; the scanning spacing coefficient λ h Layer thickness coefficient λ t The process coefficients, pre-set based on the powder material and external thread forming requirements, are used to calculate the scanning spacing and powder layer thickness. During part machining, all of these parameters are read to complete the process parameter calculation and clamping process.

[0056] Based on the target laser power P t Target scanning speed v t The laser power range and scanning speed range are clamped to obtain the execution laser power P and execution scanning speed V. Specifically: If the target laser power P t If the laser power exceeds the permissible range, the laser power P will be limited to the corresponding boundary value allowed by the device; if the target scanning speed v t If the scan speed exceeds the permissible range, the scan speed V will be limited to the corresponding boundary value allowed by the device; when the target laser power P t Target scanning speed v t When the laser power and scanning speed fall within the allowable ranges respectively, the target laser power P is... t As the laser power P, the target scanning speed v t The scanning speed, v, is used for execution. The specific calculation formula is as follows:

[0057]

[0058] In the formula, P and v represent the final laser power and scanning speed executed by the device, respectively. t and v t These represent the target laser power and target scanning speed before limiting, respectively; Pmin and P max These are the minimum and maximum laser powers allowed by the device, respectively, v min and v max These are the minimum and maximum scan speeds allowed by the device, respectively; clip indicates that the results will be limited to the corresponding upper and lower limits.

[0059] According to the nominal laser spot diameter d b With the scanning spacing coefficient λ h The calculation of the scanning interval h is based on the layer thickness coefficient λ. t The external thread pitch p and the set of allowable powder layer thickness T are selected to execute the powder layer thickness t.

[0060] The formulas for calculating the scanning spacing h and the powder layer thickness t are as follows:

[0061] In the formula, h is the execution scan interval, and λ h d is the scanning spacing coefficient. b The nominal laser spot diameter is denoted as .

[0062]

[0063] In the formula, t is the thickness of the powder layer to be applied, and λ is the thickness of the powder layer to be applied. t is the layer thickness coefficient, p is the external thread pitch, T is the set of powder layer thicknesses allowed by the equipment; Select means selecting the layer thickness closest to the target value from the set.

[0064] The laser power P and scanning speed V are rounded according to the power resolution and speed resolution input by the device, and the calculated parameter values ​​are aligned to the parameter settings that the device can recognize and set. After rounding, the laser power P and scanning speed v must still be within the corresponding allowable operating range of the device to ensure that the parameters can be executed normally by the device.

[0065] Step S70: Determine the actual processing energy value E based on the laser power P, the scanning speed v, and in combination with the scanning distance h and the powder layer thickness t. v The reference processing energy value E is determined based on the basic laser power P0, the basic scanning speed v0, and in combination with the execution scanning spacing h and the execution powder layer thickness t. v,0 .

[0066] The final volumetric energy density is calculated based on the limited execution laser power P, execution scanning speed v, execution scanning spacing h, and execution powder layer thickness t, representing the laser energy received per unit powder volume under the actual forming process; the basic volumetric energy density is calculated based on the basic laser power P0, basic scanning speed v0, and the same scanning spacing and powder layer thickness, representing the mature process energy benchmark corresponding to the benchmark reference specification.

[0067] Actual processing energy value E v and reference processing energy value E v,0 The calculation formula is as follows:

[0068] In the formula, E v P represents the actual processing energy value, v represents the laser power, h represents the scanning speed, and t represents the powder layer thickness.

[0069]

[0070] In the formula, E v,0 For reference processing energy values, P0 is determined by the base laser power, v0 base scanning speed, h execution scanning interval, and t execution powder layer thickness.

[0071] By comparing the two values, the deviation of the process energy level after thread structure correction and equipment boundary limiting from the reference energy is evaluated. If the deviation is within a preset threshold range, the current process parameters are determined to meet the external thread forming requirements, and printing is performed. If the deviation exceeds the threshold, the process energy deviation is determined to be too large, posing a risk of forming defects, and forming is not initiated. This comparison process eliminates the interference of variables such as scanning spacing and powder layer thickness, and only evaluates the energy changes introduced by laser power and scanning speed correction, thus improving the reliability of the verification.

[0072] For example, the preset relative deviation threshold is 15%; when the absolute value of the relative deviation between the final volumetric energy density and the basic volumetric energy density is not greater than 15%, it is determined that the current process parameters meet the external thread forming requirements and printing forming is performed; when the absolute value of the relative deviation exceeds 15%, it is determined that the process energy deviation is too large and the thread features have the risk of forming defects such as over-melting or incomplete fusion, and forming processing is not started.

[0073] Step S80: Based on the laser power P, scanning speed v, scanning spacing h, and powder layer thickness t, the selected area laser melting method is used to complete the printing of the external thread fastener to be formed.

[0074] This step achieves the printing and forming of the part. The final executed laser power P and scanning speed v are written into all enabled solid scan paths, ensuring that the solid scan paths corresponding to the threaded portion, shank, and head of the fastener all use this power and scanning speed. The calculated execution scanning interval h is written into the solid fill path; this limitation does not apply to other scan paths such as the outer wall contour. The selected execution powder layer thickness t is set as the overall forming layer thickness of the part, and all parts are processed using a uniform powder layer thickness. The support part can continue to use its independent process parameters. After completing the corresponding configuration of parameters and scan paths, the selected area laser melting equipment is controlled to complete the powder spreading and laser melting scanning layer by layer according to the slice file, achieving the overall forming of the external threaded fastener.

[0075] Compared with adjusting parameters manually based on experience or repeatedly testing each specification individually, the technical solution of this application has at least the following advantages: Only the nominal diameter d of the external thread and the pitch p of the external thread are selected as the variable structural parameters of the fastener. The number of variables is small, which facilitates the reading of characteristic parameters and rapid calculation.

[0076] By employing a dimensionless structural influence coefficient, the correlation between different specifications of external threaded fasteners and laser power and scanning speed is established, enabling the automatic generation of forming process parameters.

[0077] First, based on the structural correction factor K after amplitude limiting c Solve for the target laser power P t Target scanning speed v t Then, the final execution parameters are obtained by clamping the parameters within the allowable parameter range of the equipment, which effectively reduces the risk of parameters exceeding the equipment process window and reduces the workload of manual parameter setting.

[0078] By successively using two levels of constraints—the structural influence coefficient limit and the equipment parameter range clamping—the adjustment range of process parameters is restricted, thereby reducing the risk of the calculated process parameters deviating from the basic process window of the material and equipment, and reducing forming defects such as thread overmelting, collapse, or insufficient fusion.

[0079] The external thread fastener to be formed is sliced ​​using a single integral model, eliminating the need to physically separate the threaded area, shank, and head. This adapts to the existing selective laser melting process, making the process implementation convenient.

[0080] The following describes the external thread fastener forming method provided in this application with reference to the embodiments.

[0081] The external thread fastener is made of TC4 (Ti-6Al-4V) titanium alloy, with a specification of M10, meaning the nominal diameter of the external thread d = 10mm and the external thread pitch p = 1.5mm. The equipment is equipped with a 500W fiber laser, with a nominal laser spot diameter d... b=70μm; the device allows a laser power range of 50... 500W, scan speed allowed range 50 8000mm / s; the device supports powder layer thickness options of 20μm, 30μm, 50μm, 60μm, 80μm and 100μm; the device power resolution is 1W and the scanning speed resolution is 10mm / s.

[0082] Pre-calibration offline yields a complete set of reference parameter information, basic process parameters, and thresholds. Reference parameter information: Reference nominal diameter d r =8mm, reference pitch p r =1.25mm, thread structure sensitivity coefficient α=1 / 4; Lower limit of structural correction factor K min =0.85, upper limit of structural correction factor K max =1.15; Reference part basic process parameters: basic laser power P0=320W, basic scanning speed v0=1300mm / s; Equipment-side process coefficient: scanning spacing coefficient λ h ≈1.714, layer thickness coefficient λ t ≈0.0333; The energy verification preset relative deviation threshold is 15%.

[0083] Step S10: Obtain parameter information of the external thread fastener to be formed: Obtain the 3D model of the M10 external thread bolt, and extract the parameter information of the part to be formed from the 3D model: nominal diameter of external thread d=10mm, external thread pitch p=1.5mm.

[0084] Step S20: Pose setting and overall model slicing; The bolt thread axis is set to be parallel to the forming direction; the 3D model remains a single, integral model, without separating the threaded part, shank, or head, and slicing is performed directly. This orientation and slicing method are prerequisites for the calculation of this set of parameters.

[0085] Step S30: Obtain the reference parameter information and calculate the thread structure correction coefficient; Read the reference parameter information corresponding to this specification range from the pre-built reference parameter information set: reference nominal diameter d r =8mm, reference pitch p r =1.25mm, thread structure sensitivity coefficient α=1 / 4.

[0086] Substitute into the formula to calculate the thread structure correction factor:

[0087] Step S40: Limiting the thread structure correction coefficient; Read the pre-calibrated lower limit K of the structural correction factor min =0.85, upper limit K max =1.15; the calculated K=1.1125 is within the interval [0.85, 1.15]. Therefore, the correction coefficient K for the threaded structure after the amplitude limit is... c =1.1125.

[0088] Step S50: Calculate the target laser power and target scanning speed; The baseline laser power is P0 = 320W, and the baseline scanning speed is v0 = 1300mm / s.

[0089]

[0090] Step S60: Read the inherent parameters of the equipment, including equipment clamping, solving for the scanning interval and powder layer thickness, and rounding the parameter resolution; Read the inherent parameter information of the equipment: nominal laser spot diameter, scanning spacing coefficient, layer thickness coefficient, equipment powder layer thickness set, and allowable range of laser power and scanning speed.

[0091] The target power and target scanning speed are both within the allowable range of the equipment. After the equipment is clamped, the laser power and scanning speed are temporarily set to P=337.8W and v=1233mm / s.

[0092] Calculate the scan interval:

[0093] Calculate the target powder layer thickness: λ t ·p=0.0333×1.5≈0.05mm, call the Select function to select the closest setting from the set T of powder layer thicknesses of the equipment, and get the powder layer thickness t=0.05mm to be executed.

[0094] The parameters are rounded according to the device resolution: the power resolution is 1W, and the laser power is P=338W after rounding; the scanning speed resolution is 10mm / s, and the scanning speed is v=1230mm / s after rounding; the rounding result is still within the range of the device's allowable parameters.

[0095] Step S70: Processing energy verification; Calculate the actual processed energy value (actual volumetric energy density):

[0096] Calculate the reference processing energy value (basic volumetric energy density):

[0097] The relative deviation between the two parameters is calculated. In this embodiment, if the absolute value of the relative deviation is less than a preset threshold of 15%, the process parameters are deemed acceptable, and the process can proceed to the forming step. If the relative deviation exceeds 15%, a defect risk is identified, and printing is not initiated.

[0098] Step S80: Selected area laser melting printing to form the shape; Write the execution laser power of 338W and the execution scanning speed of 1230mm / s into all enabled solid scanning paths; write the execution scanning spacing of 0.12mm into the solid filling path; set the execution powder layer thickness of 0.05mm to the overall forming layer thickness of the part; the outer wall contour scanning path and support structure use independent parameters and are not constrained by this set of parameters.

[0099] After the parameters are configured, the printing equipment is controlled to spread powder layer by layer and laser scan and melt, completing the overall laser melting and forming of the M10 external thread bolt.

[0100] The M10 external thread bolts that have been formed are inspected. The TC4 external thread bolts formed are found to have complete threads, no obvious over-melting, collapse, or lack of fusion defects, and the thread dimensional accuracy meets the usage requirements.

[0101] It should be understood that this embodiment is only used to illustrate the complete execution process of the method of the present invention. All calibration parameters, equipment models, thread specifications, and thresholds are exemplary and do not constitute a limitation on the scope of protection of the present invention. Those skilled in the art can recalibrate the reference parameters, upper and lower limits, process coefficients, and verification thresholds according to the actual materials, equipment, and thread specification range.

[0102] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of those different embodiments or examples.

[0103] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified.

[0104] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for forming external threaded fasteners, characterized in that, The method includes the following steps: Obtain parameter information and reference parameter information of the external thread fastener to be formed, and calculate the thread structure correction coefficient based on the parameter information of the external thread fastener to be formed and the reference parameter information; wherein, the parameter information includes at least the nominal diameter of the external thread and the external thread pitch, and the reference parameter information includes at least the reference nominal diameter, the reference pitch and the thread structure sensitivity coefficient; Obtain the base laser power and base scanning speed from the basic process parameters of the reference part, and calculate the target laser power and target scanning speed based on the base laser power, the base scanning speed and the thread structure correction coefficient; Acquire the inherent parameter information of the equipment, which includes at least the nominal laser spot diameter, scanning spacing coefficient, layer thickness coefficient, the set of powder layer thicknesses allowed by the equipment, the laser power range allowed by the equipment, and the scanning speed range. Clamp the laser based on the target laser power, target scanning speed, laser power range, and scanning speed range to obtain the execution laser power and execution scanning speed. Calculate the execution scanning spacing based on the nominal laser spot diameter and scanning spacing coefficient. Select the execution powder layer thickness based on the layer thickness coefficient, the external thread pitch, and the set of powder layer thicknesses allowed by the equipment. Based on the laser power, scanning speed, scanning interval, and powder layer thickness, the selected area laser melting method is used to complete the printing of the external thread fastener to be formed.

2. The method for forming external threaded fasteners according to claim 1, characterized in that, Before calculating the thread structure correction factor, the method further includes: Obtain a three-dimensional model of the external thread fastener to be formed; set the thread axis of the external thread fastener to be formed to be parallel to the forming direction, and slice the three-dimensional model as a single whole model.

3. The method for forming external threaded fasteners according to claim 1, characterized in that, The method further includes: The thread structure correction coefficient is determined based on the nominal diameter of the external thread, the dimensional deviation of the external thread pitch relative to the reference nominal diameter and the reference pitch, and in combination with the preset thread structure sensitivity coefficient; The thread structure sensitivity coefficient is the degree to which changes in the nominal diameter and pitch of the thread affect the accuracy of the formed external thread structure.

4. The method for forming external threaded fasteners according to claim 1, characterized in that, After calculating the thread structure correction factor, the method further includes: Obtain the lower limit and upper limit of the structural correction coefficient, and perform amplitude limiting on the thread structure correction coefficient to obtain the amplitude-limited structural correction coefficient.

5. The method for forming external threaded fasteners according to claim 1, characterized in that, Before the step of obtaining the parameter information and reference parameter information of the fastener to be formed with external thread, the method further includes: A reference parameter information set is established, which stores the correspondence between external thread features and reference parameter information.

6. The method for forming external threaded fasteners according to claim 4, characterized in that, The method for limiting the amplitude of the thread structure correction coefficient includes: The thread structure correction coefficient is limited to between the lower limit and the upper limit of the structure correction coefficient; when the thread structure correction coefficient exceeds the boundary of the interval, the corresponding boundary value is taken as the structure correction coefficient after the limit is set; when it is within the interval, the original value is retained.

7. The method for forming external threaded fasteners according to claim 6, characterized in that, The method for calculating the target laser power and target scanning speed based on the base laser power, the base scanning speed, and the thread structure correction coefficient includes: The adjustment range of the target laser power and the target scanning speed relative to the basic parameters is matched with the structural influence effect of the structure correction coefficient after limiting: Specifically, if the structure correction coefficient after limiting increases, the target laser power will increase compared to the base laser power, and the target scanning speed will decrease compared to the base scanning speed; if the structure correction coefficient after limiting decreases, the target laser power will decrease compared to the base laser power, and the target scanning speed will increase compared to the base scanning speed.

8. The method for forming external threaded fasteners according to claim 7, characterized in that, The method for clamping based on the target laser power, the target scanning speed, the laser power range, and the scanning speed range to obtain the execution laser power and the execution scanning speed includes: If the target laser power exceeds the allowable range of the laser power range, the executed laser power is limited to the corresponding boundary value allowed by the device; if the target scanning speed exceeds the allowable range of the scanning speed range, the executed scanning speed is limited to the corresponding boundary value allowed by the device. When the target laser power and the target scanning speed fall within the allowable ranges of the laser power range and the scanning speed range, respectively, the target laser power is used as the execution laser power and the target scanning speed is used as the execution scanning speed.

9. The method for forming external threaded fasteners according to claim 1, characterized in that, Before the step of printing and forming the external threaded fastener to be formed using selective laser melting, the method further includes: The actual processing energy value is determined based on the executed laser power, the executed scanning speed, the executed scanning interval, and the executed powder layer thickness; the reference processing energy value is determined based on the base laser power, the base scanning speed, the executed scanning interval, and the executed powder layer thickness.

10. The method for forming external threaded fasteners according to any one of claims 1 to 9, characterized in that, The external threaded fasteners include at least one of bolts, screws, studs, set screws, and self-tapping screws.

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