Novel part base chamfer design method

Abstract

The invention belongs to the technical field of selective laser melting (SLM) forming, aims to solve the problem that a connecting area of an SLM forming part and a substrate is easy to crack, and discloses a novel part substrate chamfer design method. The method comprises the following steps: firstly, determining an optimal placement mode of a part and a substrate connecting area, then creating a flat substrate for the bottom of the part through Boolean operation, and finally, carrying out composite chamfering treatment of chamfering and rounding on the substrate. The stress peak is eliminated through the composite chamfer, the contact area between the flat substrate and the wide chamfer is increased to optimize heat conduction, and the chamfer with a specific angle realizes smooth transition of rigidity, so that the stress is reduced from the source. Energy consumption does not need to be increased or laser power does not need to be reduced, the performance of formed parts is not affected, operation is convenient, and the anti-cracking effect is remarkable.

Description

Technical Field

[0001] This invention belongs to the field of SLM selective laser melting forming technology, specifically relating to a novel method for designing chamfers on the substrate of a part. Background Technology

[0002] Selective laser melting (SLM) technology has been widely used in the molding and manufacturing of large-sized / structurally integrated complex parts in high-end manufacturing fields such as aerospace and automotive engineering. However, during the printing / heat treatment of such parts, printing failures and part scrapping often occur due to cracking at the connection substrate. This is mainly caused by the following reasons: 1. The rapid melting and solidification during the SLM process generates extremely high temperature gradients. Heat accumulation and cooling contraction cause high thermal stress to concentrate at the substrate connection point where structural constraints are strongest; 2. The rigid fixation of the substrate restricts the free contraction of the material, generating tensile stress at the substrate connection point; especially when the angle between the bottom of the part and the substrate is ≤90°, the stress at the connection substrate location is highly superimposed and concentrated, significantly increasing the risk of cracking.

[0003] Currently, the main measures to address this type of cracking problem are: preheating the substrate to reduce the temperature gradient between the printed layer and the substrate, thereby reducing thermal stress at the source; reducing laser input power to decrease single-point energy input and reduce stress generated by the cooling and shrinkage of the molten pool; and optimizing scanning strategies, such as partitioning and rotating scanning, to disperse heat accumulation and avoid localized stress superposition. However, these measures have disadvantages such as increased energy consumption, reduced performance of the molded part, and induction of incomplete fusion defects. Furthermore, the application of a single measure cannot directly and significantly suppress cracking at the connection substrate location. Summary of the Invention

[0004] To address the aforementioned problems in the prior art, this invention provides a novel method for designing chamfered bases for parts, comprising the following steps: Step 1: Based on factors such as printing success rate / stability, quality optimization, and support minimization, determine the optimal placement of parts and the area for connecting the printing substrate; Step 2: After completing the placement of the parts, the bottom of the parts, i.e. the area connecting to the substrate, can be determined. Boolean operations are used to create a flat base for the bottom of the parts to replace the original uneven or irregular bottom features. Step 3: After creating a flat base at the bottom of the part, perform a composite base chamfer. Select the edge where the side wall of the part intersects with the substrate and perform chamfering. Select the two new edges formed after chamfering and perform rounding.

[0005] Furthermore, the specific implementation process for determining the optimal placement of the parts and the connection area of ​​the printing substrate in step one is as follows: A1, identify the key features of the part and the area of ​​maximum overhang; A2. Adjust the orientation of the parts so that most of the overhanging structure is naturally supported by the upper layer through the step effect. Key features should face upwards or to the side to avoid direct contact with the support, while ensuring that the cross-section of the parts changes uniformly along the printing direction. A3. Check whether the overall center of gravity projection of the part falls within the contact surface of the substrate, and whether the slender cantilever thin-walled structure is effectively supported. Fine-tune the placement angle or optimize the local structural design of the part.

[0006] Furthermore, before finalizing the optimal placement of the parts and the area to be connected to the printing substrate, the support generation function of the slicing software is used to preview and confirm whether the support is within an acceptable range.

[0007] Furthermore, the specific implementation process for creating a flat substrate in step two is as follows: D1. Import the model to be processed into the 3D modeling software; D2, create a cube and adjust its size to ensure it completely covers the area of ​​the model to be cut; D3, precisely move this cube to the area of ​​the model to be cut, select the original model as the object to be cut, select the cube as the cutting tool, and perform a Boolean difference operation. At this time, the bottom of the model is a flat bottom surface.

[0008] Furthermore, if it is not permissible to have missing features at the bottom of the part or if the bottom cross-sectional area is too small to ensure printing stability, a plane can be drawn at a suitable height on the model, intersecting with the model to extract the cross-section, and the cross-section can be selected and stretched towards the bottom. The stretching height should be greater than or equal to the distance between the plane and the bottom of the model to obtain the solid. Select the solid and the model, and perform a Boolean union operation. At this point, a flat base has been created at the bottom of the part.

[0009] Furthermore, before performing the composite base chamfering, it also includes adding machining allowance. Select the flat base created in step two and stretch it towards the bottom to add machining allowance.

[0010] Furthermore, the oblique angle distance H1 is 8mm, and the angle value α is 75°.

[0011] Furthermore, the fillet is a constant chord length fillet with a radius value R of 4 mm.

[0012] Compared with the prior art, the present invention has the following outstanding advantages: 1. Stress concentration in the connection area with the substrate during the printing of large-size parts is also the root cause of cracking. This invention eliminates stress peaks through a combined design of chamfering and rounding. The smooth transition angle avoids the sharp increase of stress at the corners, expands the stress dispersion area, and disperses the stress into the larger volume of material corresponding to the inclined surface, thus reducing the stress value per unit area.

[0013] 2. The creation of a flat substrate and the wide chamfer structure in this invention increases the contact area between the substrate and the part body, which provides a better conduction path for the heat accumulated during the printing process, helps to direct the heat to the substrate, reduces the thermal gradient, thereby reducing stress (thermal stress) to prevent cracking in the area where the part is connected to the substrate, and also plays an anti-warping role.

[0014] 3. There is a huge abrupt change in stiffness between the relatively weak component and the solid substrate. By using a large 75° chamfer as a transition zone, the overall stiffness changes smoothly from the "strong substrate" to the "weak component", avoiding interface tearing caused by the drastic change in stiffness.

[0015] 4. This invention does not affect the performance of the molded part or induce incomplete fusion defects without increasing energy consumption or reducing laser input power. It is highly efficient and easy to operate, directly addressing the root cause of stress concentration. Significant anti-cracking effect can be achieved through simple structural optimization. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a novel part base chamfer design method according to the present invention; Figure 2 for Figure 1 Enlarged view of point A in the middle; Figure 3 A schematic diagram showing the optimal placement of parts and the area connecting the printing substrate; Figure 4 A diagram illustrating the creation of a flat base for the bottom of the part; Figure 5 A schematic diagram showing the addition of machining allowance to the substrate; Figure 6 This is a schematic diagram of chamfering. Figure 7 for Figure 6 Enlarged view at point B in the middle; Figure 8 This is a schematic diagram of the fillet treatment; Figure 9 for Figure 8 Enlarged view of point C in the middle.

[0017] In the diagram: 1-part, 2-substrate, 3-base. Detailed Implementation

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] like Figure 1 , 2 As shown, this invention discloses a novel method for designing the chamfer of a part's base, comprising the following steps: Step 1: Based on factors such as printing success rate / stability, quality optimization, and support minimization, determine the optimal placement of part 1 and the area connecting to printing substrate 2; Step 2: After placing part 1, the bottom of the part, i.e. the area connecting the substrate 2, can be determined. Boolean operations are used to create a flat base 3 for the bottom of part 1 to replace the original uneven or irregular bottom features. Step 3: After creating a flat base 3 at the bottom of part 1, perform a composite base chamfer. Select the intersection of the side wall of part 1 and the base plate 2 and perform chamfering. Select the two new edges formed after chamfering and perform rounding.

[0020] like Figure 3 As shown, the specific implementation process for determining the optimal placement of part 1 and the area connecting the printing substrate 2 in step one is as follows: A1, Identify the key features and maximum overhang area of ​​part 1; A2, Adjust the placement direction of part 1 so that most of the overhanging structure is naturally supported by the upper layer through the step effect, with key features facing upwards or to the side to avoid direct contact with the support, while ensuring that the cross-section of part 1 changes uniformly along the printing direction. A3, Check whether the overall center of gravity projection of part 1 falls within the contact surface of the substrate, such as Figure 3 As shown, the key features of part 1 face upwards, and the projection of its center of gravity falls within the contact surface of substrate 2. Whether the slender cantilever thin wall and other structures are effectively supported, the placement angle can be finely adjusted or the local structural design of the part can be optimized.

[0021] A further optimization approach involves using the support generation function of the slicing software to preview the optimal placement of part 1 and the area connected to the printing substrate 2 before final confirmation, to confirm whether the support is within an acceptable range.

[0022] like Figure 4 As shown, the specific implementation process for creating a flat substrate 3 in step two is as follows: D1. Import the model to be processed into 3D modeling software, such as Solidworks, Fusion360, Rhino, etc. D2, create a cube and adjust its size to ensure it completely covers the area of ​​the model to be cut; D3, precisely move this cube to the area of ​​the model to be cut, select the original model as the object to be cut, select the cube as the cutting tool, and perform a Boolean difference operation. At this time, the bottom of the model is a flat bottom surface.

[0023] Additionally, if it's unacceptable to have missing features on the bottom of the part or if the bottom cross-sectional area is too small to guarantee printing stability, a plane can be drawn at a suitable height on the model. This plane intersects the model to extract a cross-section. The cross-section is then selected and stretched towards the bottom, with the stretching height greater than or equal to the distance between the plane and the bottom of the model. This creates a solid. The solid and the model are then selected, and a Boolean union operation is performed. At this point, a flat base has been created at the bottom of the part. After printing, any excess parts can be removed through machining, sanding, or other post-processing methods to restore the bottom feature shape of the part.

[0024] like Figure 5 As shown, before performing the composite base chamfering, additional machining allowance is added. The flat base 3 created in step two is selected and stretched towards the bottom. The "Stretch" command is executed, with a stretch distance H2 of 9mm, in a direction away from the body of part 1, adding machining allowance. The purpose is to provide a stress buffer layer and subsequent machining allowance, inhibiting crack propagation to the body of part 1.

[0025] like Figure 6 , 7 As shown, the bevel distance H1 is 8mm and the angle α is 75°. Select the intersection of the part's sidewall and the substrate, execute the "Bevel" command, and set the distance to 8mm and the angle to 75°. This achieves a smooth transition from substrate 3 to part 1, optimizes heat conduction, and avoids stress concentration.

[0026] like Figure 8 , Figure 9 As shown, the fillet is a constant chord length fillet with a radius R of 4mm. Select the new edge formed after chamfering, execute the "Fillet" command, and set the radius to 4mm. The fillet eliminates the sharp edge formed after chamfering, further dispersing stress.

[0027] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements can be made without departing from the principle of the present invention, and these improvements should also be considered within the scope of protection of the present invention.

Claims

1. A novel method for designing chamfers on the base of a part, characterized in that, Includes the following steps: Step 1: Based on factors such as printing success rate / stability, quality optimization, and support minimization, determine the optimal placement of part (1) and the area for connecting the printing substrate (2); Step 2: After placing the part (1), the bottom of the part, i.e. the area connecting the substrate (2), can be determined. Boolean operation is used to create a flat base (3) for the bottom of the part (1) to replace the original uneven or irregular bottom features. Step 3: After creating a flat base (3) at the bottom of part (1), perform composite base chamfering. Select the intersection of the side wall of part (1) and the substrate (2) for chamfering. Select the two new edges formed after chamfering for rounding.

2. The novel part base chamfer design method according to claim 1, characterized in that, The specific implementation process for determining the optimal placement of part (1) and the area connecting the printing substrate (2) in step one is as follows: A1, identify the key features and maximum overhang area of ​​part (1); A2, adjust the placement direction of part (1) so that most of the overhanging structure is naturally supported by the upper layer through the step effect, with key features facing upward or sideways to avoid direct contact with the support, while ensuring that the cross-section of part (1) changes uniformly along the printing direction. A3, check whether the overall center of gravity projection of part (1) falls within the contact surface of the substrate, whether the slender cantilever thin wall and other structures are effectively supported, and fine-tune the placement angle or optimize the local structural design of the part.

3. The novel part base chamfer design method according to claim 2, characterized in that, Before finalizing the optimal placement of part (1) and the area for connecting the printing substrate (2), use the support generation function of the slicing software to preview and confirm whether the support is within acceptable limits.

4. The novel part base chamfer design method according to claim 1, characterized in that, The specific implementation process for creating a flat base (3) in step two is as follows: D1. Import the model to be processed into the 3D modeling software; D2, create a cube and adjust its size to ensure it completely covers the area of ​​the model to be cut; D3, precisely move this cube to the area of ​​the model to be cut, select the original model as the object to be cut, select the cube as the cutting tool, and perform a Boolean difference operation. At this time, the bottom of the model is a flat bottom surface.

5. The novel part base chamfer design method according to claim 4, characterized in that, If the bottom feature of the part is not allowed to be damaged or the bottom cross-sectional area is too small to ensure printing stability, a plane can be drawn at a suitable height of the model, and the cross-section can be extracted by intersecting the model. The cross-section is selected and stretched to the bottom. The stretching height should be greater than or equal to the distance between the plane and the bottom of the model to obtain the solid. Select the solid and the model and perform a Boolean union operation. At this time, a flat base has been created at the bottom of the part (3).

6. The novel part base chamfer design method according to claim 1, characterized in that, Before performing composite base chamfering, it also includes adding machining allowance. Select the flat base (3) created in step two and stretch it to the bottom direction to add machining allowance.

7. The novel part base chamfer design method according to claim 1, characterized in that, The oblique angle distance H1 is 8mm, and the angle α is 75°.

8. The novel part base chamfer design method according to claim 1, characterized in that, The fillet is a constant chord length fillet with a radius R of 4 mm.

Images