Preparation method of skull protective cap based on finite element stress analysis

Abstract

The invention relates to the medical field of 3D printing. The invention aims to provide a skull protective cap preparation method based on finite element stress analysis. The skull protective cap preparation method comprises the following steps: S1, acquiring preoperative and postoperative skull three-dimensional models of a patient; s2, generating a corresponding NURBS curved surface model; s3, cutting the protective cap model; s4, aligning the cut protective cap model to the postoperative cranial three-dimensional model; s5, generating a cushion model according to the form of the annular gap; s6, performing finite element stress analysis on the three-dimensional model set of the skull pad cap; and S7, forming is conducted in a 3D printing mode. According to the method, the protective cap structure better matched with the physiological parameters of the patient can be constructed in a model reconstruction mode relying on the data of the patient, and precise customization is achieved. By performing finite element analysis on the model, whether a cushion needs to be added under the protective cap or not and parameters of the cushion need to be added are scientifically and accurately determined, and a foundation is laid for subsequent scientific decision making.

Description

Technical Field

[0001] The present invention relates to the field of 3D printing medicine, and particularly relates to a preparation method of a skull protection cap based on finite element stress analysis. Background Art

[0002] In recent years, with the rapid popularization and application of 3D printing technology in the medical field, more and more hospitals and medical research institutions have gradually started to use 3D printing to form various customized instruments or protectors to meet the needs of personalized medicine and customized medicine. The skull protection cap is a protector for severe cranial injuries with skull defects, which realizes external protection of intracranial tissues by wearing the protector. Wearing the skull protection cap can provide anti-impact protection for intracranial tissues, make the intracranial tissues full, and quickly recover to the anatomical shape before injury, which is an important transitional stage for subsequent skull repair.

[0003] At present, the skull protection caps manufactured by traditional methods are not only expensive and have a long customization cycle, but also cannot truly perfectly match the shape of the cranial defect of the patient. They not only have insufficient protection, but also have poor aesthetics after wearing, and increasingly do not meet the development needs of modern medicine. This is mainly because in the production and manufacturing process of the skull protection cap prepared by traditional methods, only isolated parameters such as the shape of the protection cap and the position of the protection cap are mainly considered, without systematic mechanical property analysis. Its anti-bending and anti-torsion properties cannot be effectively guaranteed after wearing, resulting in certain deficiencies in the reliability of its protection after wearing; reducing the hidden risk during the wearing of the skull protection cap. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation method of a skull protection cap based on finite element stress analysis with good protection performance and stable and reliable stress.

[0005] To achieve the above invention purpose, the technical solution adopted by the present invention is: a preparation method of a skull protection cap based on finite element stress analysis, including the following steps:

[0006] S1. Obtain the three-dimensional models of the cranial part before and after the operation of the patient;

[0007] S2. Smooth the surface defects of the three-dimensional models of the cranial part before and after the operation; generate the corresponding NURBS surface model;

[0008] S3. Taking the skull defect range on the three-dimensional model of the cranial part after the operation as a reference, cut a block from the three-dimensional model of the cranial part before the operation as the protection cap model. The range of the protection cap model is based on being able to cover the skull defect range after the operation, and adjust the thickness of the protection cap model;

[0009] S4. Align the cut protective cap model to the postoperative cranial three-dimensional model, and reserve an annular gap for installing the soft pad between the bottom of the edge of the protective cap model and the human head soft tissue;

[0010] S5. Generate a soft pad model according to the shape of the annular gap. The soft pad model, the protective cap model and the postoperative cranial three-dimensional model jointly form a cranial pad cap three-dimensional model set; Smooth the surface defects of the cranial pad cap three-dimensional model set to generate a corresponding NURBS surface model;

[0011] S6. Import the smoothed cranial pad cap three-dimensional model set into Ansys software in X_T format, and perform finite element stress analysis on the cranial pad cap three-dimensional model set; And adjust the soft pad model according to the results of the finite element stress analysis to determine the optimization method of the soft pad model in the cranial pad cap three-dimensional model set;

[0012] S7. Import the protective cap model and the soft pad model of the optimized cranial pad cap three-dimensional model set into a 3D printing device and form them by 3D printing.

[0013] Preferably, in the step S6, the steps of finite element stress analysis include:

[0014] S6.1 Material assignment: Assign material properties to each part in the cranial pad cap three-dimensional model set in Ansys;

[0015] S6.2 Mesh division setting: Since the shape of the cranial pad cap three-dimensional model set is irregular, the protective cap model, the soft pad model, and the human head soft tissue are all divided by second-order tetrahedral mesh elements; And determine the appropriate number of mesh elements through mesh sensitivity inspection;

[0016] S6.3 Contact pair setting: Set the contact surface between the soft pad model and the protective cap model as a bonded contact, and set the contact surface between the soft pad model and the human head soft tissue as a non-separating contact; Set the contact surfaces between the remaining solid parts of the cranial pad cap three-dimensional model set as bonded contacts;

[0017] S6.4 Boundary and load condition setting: Fix the position at the bottommost part of the head in the cranial pad cap three-dimensional model set, apply a force with an axial load of 50 N and a torque of 1.5 N·m on the surface of the protective cap model to simulate four working conditions of the cranial pad cap three-dimensional model bending to the left, bending to the right, rotating to the left, and rotating to the right; And record the stress distribution of the contact surface between the human head soft tissue and the soft pad model in the cranial pad cap three-dimensional model set;

[0018] S6.5 Repeat steps S6.1 - S6.4, where the material parameters assigned to the cushion model are adjusted to be the same as those of the protective cap model, and the contact surface between the cushion model and the human head soft tissue is set as a bonded contact to serve as a model set of a cranial cap without a cushion, and record the stress distribution on the contact surface with the human head soft tissue under four working conditions of bending to the left, bending to the right, rotating to the left, and rotating to the right under the same load conditions;

[0019] S6.6 Comparison: Compare the contact surface stress distribution results of the recorded model set of the cranial cap without a cushion and the three - dimensional model set of the cranial cushion cap. Use whether the stress peak value drops as the basis for judging whether the cushion improves abnormal stress or stress concentration; use the drop amplitude of the stress peak value as the basis for optimizing the cushion model.

[0020] Preferably, in step S1, first obtain the standard DICOM - format data of the patient before and after the operation, import the standard DICOM - format data into MIMICS software, and reconstruct the cranial bone and head soft tissue data of the patient through MIMICS software to generate three - dimensional cranial models before and after the operation.

[0021] Preferably, in step S1, the source of the standard DICOM - format data is one or more of CT, MRI, and X - ray.

[0022] Preferably, in step S2, export the three - dimensional cranial model processed in step S1 in STL format and import it into geomagic software; use geomagic software to perform any one or more of filling, repairing, and smoothing the surface defects of the three - dimensional cranial model to generate a corresponding NURBS surface model after smooth processing.

[0023] Preferably, in step S3, the thickness of the protective cap model is 4 mm.

[0024] Preferably, in step S4, the reserved gap for installing the cushion is 2 mm.

[0025] Preferably, in step S5, during smooth processing, use geomagic software to perform any one or more of filling, repairing, and smoothing the surface defects of the three - dimensional model set of the cranial cushion cap to generate a corresponding NURBS surface model after smooth processing.

[0026] The beneficial effects of the present invention are mainly reflected in:

[0027] 1. Through the model reconstruction method relying on the patient's own data, a protective cap structure that better matches the patient's physiological parameters can be constructed, achieving precise customization.

[0028] 2. By performing finite element analysis on the model, scientifically and accurately determine whether it is necessary to add a soft pad under the protective cap and the parameters of the added soft pad, laying a foundation for subsequent scientific decision-making.

[0029] 3. Through this pre-prediction simulation, the risk of wearing hazards caused by poor protective cap matching and poor protection stability can be effectively reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the three-dimensional model of the patient's cranial part after the operation of the present invention;

[0031] Figure 2 It is a schematic diagram of the protective cap model of the present invention;

[0032] Figure 3 It is a schematic diagram of the soft pad model of the present invention;

[0033] Figure 4 It is a schematic diagram of the three-dimensional model set of the cranial pad cap of the present invention;

[0034] Figure 5 It is a comparison image of a certain patient treated with the cranial protective cap of the present invention;

[0035] Figure 6 It is the Von-Mises stress nephogram of the head and cranial protective cap without a soft pad;

[0036] Figure 7 It is the Von-Mises stress nephogram of the head and cranial protective cap with a soft pad. DETAILED DESCRIPTION OF THE INVENTION

[0037] The present invention discloses a 3D printed cranial protective cap with enhanced protection, which mainly includes a protective cap body formed by 3D printing and matching the cranial defect part of the patient, and a soft pad arranged between the bottom edge of the protective cap body and the human head soft tissue; the soft pad is also formed by 3D printing. In the present invention, the shape of the protective cap body can be based on Figure 2 the 3D printed entity of the protective cap model 2 in Figure 3 as a reference, and the shape of the soft pad can be based on

[0038] Figure 3 the 3D printed entity of the soft pad model 3 in as a reference. The 3D printed protective cap body and soft pad are prepared through a process of finite element force analysis, with better overall protection performance, better installation reliability, and can effectively reduce the risk during wearing. The specific preparation method is described in detail below.

[0038] By adding a soft pad, the stress condition of the contact surface with the soft tissues of the human head can be better improved, and the stability of the installation of the main body of the protective cap and the reliability of the protection can be enhanced. At the same time, the soft pad can fill the objectively existing machining error gap between the soft tissues of the human head and the main body of the protective cap, ensure the effectiveness of the contact between the soft tissues of the human head and the main body of the protective cap, improve the abnormal stress or stress concentration, and reduce the risk of the main body of the protective cap being displaced when subjected to external forces.

[0039] However, for the skull protective cap described in the present invention, in order to facilitate wearing, a fixing component is often also provided, and the fixing component is used to fix the main body of the protective cap on the patient's head. There are many specific forms or structural types of the fixing component. For example, the fixing component is a net bag worn on the patient's head, or the fixing component is an elastic strap provided on the edge of the main body of the protective cap. The fixing component is usually installed and used separately later after the skull protective cap is processed.

[0040] For some patients with high requirements for aesthetics, the present invention can also provide a beautifying layer on the outer surface of the main body of the protective cap. The beautifying layer is a layer of flexible cloth adhesively fixed on the outer surface of the main body of the protective cap, and artificial hair pasted on the flexible cloth. By adding the beautifying layer, the overall appearance of the protective cap can fit the appearance of the normal human skull, reducing the psychological burden of the patient when wearing. In addition, since the present invention is provided with a soft pad, in order to ensure the stability and convenience of the installation between the soft pad and the main body of the protective cap, a better method can also be that an installation groove extending along the circumference of the soft pad is provided at a position opposite to the soft pad at the bottom edge of the main body of the protective cap, and the soft pad is clamped in the installation groove.

[0041] Compared with the traditional 3D printing preparation method, the present invention particularly discloses a preparation method of a skull protective cap, which specifically includes the following steps:

[0042] S1. Obtain the three-dimensional models 1 of the patient's skull before and after surgery. First, obtain the standard DICOM format data of the patient before and after surgery. The source of the standard DICOM format data can be one or a combination of CT, MRI, and X-ray. Import the standard DICOM format data into the MIMICS 21.0 software of Materialise company, reconstruct the skull and head soft tissue data of the patient through the MIMICS 21.0 software, and generate the three-dimensional models 1 of the patient's skull before and after surgery. As Figure 1 shown in the figure, it is the three-dimensional model 1 of the patient's skull after surgery, and most skull defects are constructed due to the need to release intracranial pressure during the operation. The three-dimensional model 1 of the patient's skull before surgery can be regarded as the shape before the skull defect.

[0043] S2. Smooth the surface defects of the preoperative and postoperative cranial three-dimensional model 1 to generate the corresponding NURBS surface model. In practical applications, export the cranial three-dimensional model 1 processed in step S1 in STL format and import it into the Geomagic Wrap 2021 software under the American company Raindrop. Using this software, smooth the surface defects of the cranial three-dimensional model 1, such as filling holes on the surface, repairing nail-like structures, and smoothing non-smooth surfaces. After processing, generate the corresponding NURBS surface model after smoothing.

[0044] S3. Taking the skull defect range on the postoperative cranial three-dimensional model 1 as a reference, cut a block from the preoperative cranial three-dimensional model 1 as the protection cap model 2. The range of the protection cap model 2 should be able to cover the postoperative skull defect range, and adjust the thickness of the protection cap model 2, usually 4mm.

[0045] S4. Align the cut protection cap model 2 to the postoperative cranial three-dimensional model 1 to verify the reliability of its coverage of the skull defect range. Reserve an annular gap for installing the soft pad model 3 between the bottom of the edge of the protection cap model 2 and the human head soft tissue. The thickness of the annular gap is generally 2mm, and the width can be set to about 0.8 - 1.2CM.

[0046] S5. Then, generate the soft pad model 3 according to the shape of the annular gap. The soft pad model 3, the protection cap model 2, and the postoperative cranial three-dimensional model 1 together form a cranial pad cap three-dimensional model set. Perform an overall secondary smoothing process on the surface defects of the cranial pad cap three-dimensional model set to generate the corresponding NURBS surface model. The smoothing method is similar to the previous smoothing method, which is to use geomagic software to fill, repair, and smooth the surface defects of the cranial pad cap three-dimensional model set. According to the actual situation, multiple processing methods can be used alone or in combination. After processing, generate the corresponding NURBS surface model after smoothing, that is, the NURBS surface model of the cranial pad cap three-dimensional model set.

[0047] S6. Import the smoothed cranial pad cap three-dimensional model set into Ansys software in X_T format to perform finite element force analysis on the cranial pad cap three-dimensional model set. Finally, adjust the soft pad model 3 according to the results of the finite element force analysis to determine the optimization method of the soft pad model 3 in the cranial pad cap three-dimensional model set.

[0048] In this step, the specific processing method can be as follows:

[0049] S6.1 Material Assignment: In Ansys software, material properties are assigned to each part in the 3D model set of the cranial pad cap (including anatomical structures such as the skull and human head soft tissues; implants such as the protection cap model 2 and the cushion model 3). When assigning material properties, the material characteristics of each solid element can be regarded as isotropic, continuous, and uniform. Specific materials and corresponding parameters can be selected by referring to existing common materials.

[0050] S6.2 Mesh Division Setting: Since the 3D model set of the cranial pad cap has an irregular shape, the second-order tetrahedral mesh elements (C3D10 elements) are used to divide the protection cap model 2, the cushion model 3, and the human head soft tissues. And the appropriate number of mesh elements is determined through mesh sensitivity inspection.

[0051] S6.3 Contact Pair Setting: The contact surface between the cushion model 3 and the protection cap model 2 is set as a bonded contact, and the contact surface between the cushion model 3 and the human head soft tissues is set as a non-separating contact. It is assumed that there is no relative displacement between the contact surfaces of the remaining solid parts in the 3D model set of the cranial pad cap, and they are still set as bonded contacts.

[0052] S6.4 Boundary and Load Condition Setting: Fix the position at the very bottom of the head in the 3D model set of the cranial pad cap, that is, the constraint, which means fixing the 6 degrees of freedom in the three-dimensional space of the lower part of the head (neck). Simulate by applying a force of 50N in the axial direction and a torque of 1.5N·m on the surface of the protection cap model 2 to simulate four working conditions of the 3D model of the cranial pad cap bending to the left, bending to the right, rotating to the left, and rotating to the right. And record the stress distribution on the contact surface between the human head soft tissues and the cushion model 3 in the 3D model set of the cranial pad cap.

[0053] S6.5 Repeat steps S6.1 - S6.4. Among them, adjust the material parameters assigned to the cushion model 3 to be the same as those of the protection cap model 2, and set the contact surface between the cushion model 3 and the human head soft tissues as a bonded contact to serve as the cranial cap model set without the cushion model 3, and record the stress distribution on the contact surface with the human head soft tissues under the same load conditions (under the condition of applying a force of 50N in the axial direction and a torque of 1.5N·m on the surface of the protection cap model 2) for the four working conditions of bending to the left, bending to the right, rotating to the left, and rotating to the right.

[0054] S6.6 Comparison: Compare the contact surface stress distribution results of the corresponding recorded non-cushion model 3 skull cap model set and the skull cap three-dimensional model set, and use the decrease of the stress peak as the basis for judging whether the cushion model 3 improves the abnormal stress or stress concentration. If the stress peak is reduced and the stress is uniform, it means that the stress condition is positively affected by adding the cushion model 3; in some extremely special cases, the stress peak is not significantly reduced and the improvement of stress uniformity is not very obvious, which means that the matching degree between the protective cap body 2 and the soft tissue of the human head is very good, and the shape of the periphery of the skull defect makes it have good reliability even without adding the cushion model 3. In this case, the cushion can be omitted according to the wishes of the patient and the patient's family to reduce the overall cost. However, the probability of this situation is low. According to comprehensive statistics, in more than 98% of the cases, the stress condition is effectively improved after adding the cushion model 3. At the same time, the present invention can also use the decrease in the stress peak as a basis for optimizing the cushion model 3, that is, by giving different material properties to the cushion model 3 and appropriately adjusting its thickness parameters, etc., its own stress condition can be improved to a certain extent and its performance can be enhanced. After reaching an optimization plan, different cushion materials can be selected for subsequent preparation based on the patient's wishes.

[0055] S7. Import the optimized and adjusted protective cap model 2 and soft cushion model 3 of the skull cap three-dimensional model set into a 3D printing device, and shape them by 3D printing to obtain the protective cap body and soft cushion, which are then delivered to the patient for use.

[0056] Application examples:

[0057] like Figure 5 As shown in the figure, the patient, Mr. Luo, male, 58 years old, was admitted to the hospital due to a car accident. The diagnosis was: 1. Right temporal lobe cerebral contusion, 2. Right frontal, temporal and parietal acute subdural hematoma, 3. Traumatic subarachnoid hemorrhage, 4. Left parietal fracture, 5. Left parietal scalp laceration. The patient was diagnosed after a CT scan when he was admitted to the hospital. On the same day, he underwent emergency general anesthesia for "right frontal, temporal and parietal subdural hematoma removal + right temporal lobe partial resection + artificial dura mater repair + bone craniotomy decompression + debridement and suture". After the operation, he was hospitalized for a long time and was discharged after his condition improved.

[0058] Before discharge, the patient had a missing skull after surgery, the right frontal temporoparietal skin flap collapsed significantly, and the right side of the head lacked bone protection. If he fell accidentally, he would be at high risk of traumatic cerebral hemorrhage. Therefore, the present invention was used to protect the skull defect. The process of making the protective cap is consistent with the above method.

[0059] Finite element analysis: Compare the contact surface stress distribution results of the corresponding recorded non-cushion model 3 skull cap model set and the skull cap 3D model set, and use the decrease in the stress peak as a basis for determining whether the soft pad improves the abnormal stress or stress concentration of the skull cap.

[0060] The comparison data is as follows Figure 6 and 7 shown below.

[0061] Figure 6 In [reference], different colors represent different stress conditions. The red area is the distribution of the maximum stress value range, and the blue area is the distribution of the minimum stress value range. Taking the working condition of bending down to the left as an example, stress concentration is likely to occur at the connection between the head and the protective cap. The stress peak value of the head is 0.052273 Mpa, and the stress peak value of the protective cap is 1.3591 Mpa.

[0062] Figure 7 In [reference], different colors represent different stress conditions. The red area is the distribution of the maximum stress value range, and the blue area is the distribution of the minimum stress value range. Taking the working condition of bending down to the left as an example, the stress peak value of the head is 0.064354 Mpa, the stress peak value of the protective cap is 0.72995 Mpa, and the stress peak value of the soft pad is 0.049382 Mpa.

[0063] It can be seen from the comparison that compared with the model without the soft pad, although the stress peak value of the head has increased, the stress peak value of the protective cap has decreased significantly. The decrease in the stress peak value indicates that the soft pad can significantly improve the stress concentration phenomenon generated between the skull protective cap and the head, and it is suitable for assembling the soft pad.

[0064] After the model is verified by finite element method, it is prepared by 3D printing technology and placed on the patient. Since the protective cap fits and completely covers the skin flap of the patient's skull defect, the patient is satisfied with the comfort, ease of wearing, and hardness of the protective cap.

Claims

1. A method for preparing a cranial protection cap based on finite element force analysis, characterized in that, It includes the following steps: S1. Obtain the preoperative and postoperative cranial three-dimensional models (1) of the patient; S2. Smooth the surface defects of the preoperative and postoperative cranial three-dimensional models (1); generate the corresponding NURBS surface models; S3. Taking the skull defect range on the postoperative cranial three-dimensional model (1) as a reference, cut a block from the preoperative cranial three-dimensional model (1) as the protection cap model (2), and the range of the protection cap model (2) should be able to cover the postoperative skull defect range, and adjust the thickness of the protection cap model (2); S4. Align the cut protection cap model (2) to the postoperative cranial three-dimensional model (1), and reserve an annular gap for installing the soft pad model (3) between the bottom of the edge of the protection cap model (2) and the human head soft tissue; S5. Generate the soft pad model (3) according to the shape of the annular gap. The soft pad model (3), the protection cap model (2) and the postoperative cranial three-dimensional model (1) jointly form a cranial pad cap three-dimensional model set; smooth the surface defects of the cranial pad cap three-dimensional model set to generate the corresponding NURBS surface models; S6. Import the smoothed cranial pad cap three-dimensional model set into Ansys software in X_T format, and perform finite element stress analysis on the cranial pad cap three-dimensional model set; and adjust the soft pad model (3) according to the results of the finite element stress analysis to determine the optimization method of the soft pad model (3) in the cranial pad cap three-dimensional model set; S7. Import the protection cap model (2) and the soft pad model (3) of the optimized cranial pad cap three-dimensional model set into a 3D printing device and form them by 3D printing.

2. The method for preparing a cranial protection cap based on finite element force analysis according to claim 1, characterized in that: In the step S6, the steps of the finite element stress analysis include: S6.1 Material assignment: Assign material properties to each part in the cranial pad cap three-dimensional model set in Ansys; S6.2 Mesh division setting: Since the shape of the cranial pad cap three-dimensional model set is irregular, the protection cap model (2), the soft pad model (3), and the human head soft tissue are all divided by second-order tetrahedral mesh elements; and determine the appropriate number of mesh elements through mesh sensitivity inspection; S6.3 Contact pair setting: Set the contact surface between the soft pad model (3) and the protection cap model (2) as a bonded contact, and set the contact surface between the soft pad model (3) and the human head soft tissue as a non-separating contact; set the contact surfaces between the remaining solid parts of the cranial pad cap three-dimensional model set as bonded contacts; S6.4 Boundary and load condition setting: Fix the position at the lowest end of the head in the cranial pad cap three-dimensional model set, apply a force with an axial load of 50 N and a torque of 1.5 N·m on the surface of the protection cap model (2) to simulate four working conditions of the cranial pad cap three-dimensional model bending to the left, bending to the right, rotating to the left, and rotating to the right; and record the stress distribution of the contact surface between the human head soft tissue and the soft pad model (3) in the cranial pad cap three-dimensional model set; S6.5 Repeat steps S6.1 - S6.4, where the material parameters assigned to the cushion model (3) are adjusted to be the same as those of the protective cap model (2), and the contact surface between the cushion model (3) and the human head soft tissue is set as a bonded contact to serve as a cranial cap model set without the cushion model (3), and record the stress distribution on the contact surface with the human head soft tissue under four working conditions of bending to the left, bending to the right, rotating to the left, and rotating to the right under the same load conditions; S6.6 Comparison: Compare the contact surface stress distribution results of the recorded cranial cap model set without the cushion model (3) and the cranial cushion cap three - dimensional model set. Use whether the stress peak drops as the basis for judging whether the cushion model (3) improves abnormal stress or stress concentration; use the drop amplitude of the stress peak as the basis for optimizing the cushion model (3).

3. The method for preparing a cranial protection cap based on finite element force analysis according to claim 2, wherein: In step S1, first obtain the standard DICOM - format data of the patient before and after the operation, import the standard DICOM - format data into MIMICS software, and reconstruct the cranial bone and head soft tissue data of the patient through the MIMICS software to generate the pre - operative and post - operative cranial three - dimensional models (1).

4. The method for preparing a cranial protection cap based on finite element stress analysis according to claim 3, wherein: In step S1, the source of the standard DICOM - format data is one or more of CT, MRI, and X - ray.

5. The preparation method of the skull protection cap based on finite element stress analysis according to claim 4, characterized in that: In step S2, export the cranial three - dimensional model (1) processed in step S1 in STL format and import it into geomagic software; use geomagic software to perform any one or more of filling, repairing, and smoothing the surface defects of the cranial three - dimensional model (1) to generate the corresponding NURBS surface model after smooth processing.

6. The method for preparing a cranial protection cap based on finite element stress analysis according to claim 5, wherein: In step S3, the thickness of the protective cap model (2) is 4 mm.

7. The method for preparing a cranial protection cap based on finite element force analysis according to claim 6, characterized in that: In step S4, the reserved gap for installing the cushion model (3) is 2 mm.

8. The method for preparing a cranial protection cap based on finite element stress analysis according to claim 7, wherein: In step S5, during smooth processing, use geomagic software to perform any one or more of filling, repairing, and smoothing the surface defects of the cranial cushion cap three - dimensional model set to generate the corresponding NURBS surface model after smooth processing.

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