Laser polishing method for additive manufacturing removable local metal denture support

Abstract

The invention discloses a laser polishing method for an additive manufacturing removable local metal denture support. The laser polishing method comprises the steps that a, stress relief annealing and support removal are conducted on the additive manufacturing metal denture support; b, the metal false tooth support is flatly placed on the surface of the flexible tool, and the metal false tooth support makes full contact with the flexible tool; c, the height difference of the metal denture support is measured, and a single-face laser polishing strategy is planned; d, placing the metal false tooth support and the flexible tool on a Z-axis displacement platform, and then integrally placing the metal false tooth support and the flexible tool in a glove box filled with protective gas; e, laser processing parameters are set, a laser processing system is started, and single-face polishing of the metal false tooth support is completed; and f, turning over the metal denture support to another unpolished surface, and repeating the steps b-e to finish polishing of the other surface of the metal denture support. Based on the laser polishing method, focus height regulation and control and flexible tool design in the polishing process are combined, and high-precision surface treatment and uniform heat dissipation of the additive manufacturing metal false tooth support are achieved.

Description

Technical Field

[0001] The invention relates to the technical field of laser surface treatment, and in particular to a laser polishing method for additively manufacturing a removable partial metal denture bracket. Background Art

[0002] Removable partial dentures are mainly composed of artificial teeth, brackets, retainers and connectors. They are one of the important ways to repair dentition defects. Metal brackets have the advantages of high precision, high strength, self-cleaning and good temperature conduction. In recent years, with the rapid development of laser powder bed fusion additive manufacturing technology, personalized metal brackets formed by additive manufacturing technology have been widely used; compared with the traditional casting method to manufacture metal denture brackets, additive manufacturing of metal brackets has high precision, simple process and excellent mechanical properties, which can greatly shorten the manufacturing cycle of metal denture brackets.

[0003] However, due to the cumulative effect of materials layer by layer during the forming process and the non-steady-state flow of the molten pool under laser irradiation, the formed surface quality is poor and the roughness is high, requiring manual grinding and post-processing. Metal denture brackets have complex shapes, and all products are customized. Currently, they are mainly processed by manual grinding, which is a complex, time-consuming, and unstable process. The mechanical grinding process can easily cause deformation and damage to the bracket. It is necessary to carry out automated grinding and polishing post-processing based on the characteristics of metal denture brackets to improve the efficiency and quality of post-processing. Summary of the invention

[0004] In view of the problems of the prior art, the present invention provides a laser grinding and polishing method for additively manufacturing a metal removable partial denture bracket. The present invention is achieved through the following technical solutions:

[0005] A laser polishing method for additively manufacturing a removable partial metal denture framework comprises the following steps:

[0006] a. Stress relief annealing and support removal of additively manufactured metal denture frameworks;

[0007] b. Place the metal denture bracket flat on the surface of the flexible tooling, and manually press it to make the metal denture bracket fully contact with the top of the support module in the flexible tooling;

[0008] c. Measure the height difference of metal denture brackets and plan the single-sided laser polishing strategy;

[0009] d. Place the metal denture bracket and the flexible tooling on the Z-axis displacement platform, and then place the whole in a glove box filled with protective gas;

[0010] e. Set the laser processing parameters, start the laser processing system, and complete the single-sided polishing of the metal denture bracket;

[0011] f. Turn the metal denture bracket over to the other unpolished surface and repeat step be to complete the polishing of the other side of the metal denture bracket.

[0012] Preferably, in step a, the metal denture bracket is an additively manufactured titanium alloy bracket or a cobalt alloy denture bracket.

[0013] Preferably, in step b, the flexible tooling includes a plurality of support modules arranged in an array, the support modules include a base and a support unit fixed on the base; the support unit includes a fixed support column, a movable support column and a damping block located between the fixed support column and the movable support column; the interior of the fixed support column is a hollow structure, the movable support column can slide in the vertical direction in the fixed support column under the action of an external force, and after the external force is removed, due to the damping effect of the damping block, the movable support column and the fixed support column remain relatively still, thereby being able to support the metal denture bracket. Further preferably, the spacing between the support modules is 2-5mm; the diameter of the fixed support column is 2-8mm, and the maximum sliding distance of the movable support column in the fixed support column is 25mm; the material of the support module is a relatively high melting point metal such as stainless steel, titanium alloy or tungsten alloy. Several support modules in the flexible tooling can be adjusted to different heights by moving the movable support column within the fixed support column. This can adapt to the personalized characteristics of the metal denture bracket and fully contact different parts of the metal denture bracket to avoid serious dimensional deformation of the metal denture bracket due to poor local heat dissipation. In addition, it can avoid high-temperature damage to the support unit during the laser polishing process.

[0014] Preferably, in step c, the laser polishing strategy is: when the height difference of the metal denture bracket is less than 10 mm, one laser polishing is adopted, and the laser focus falls on the 1 / 2 position of the height of the metal denture bracket during the polishing process; when the height difference of the metal denture bracket is greater than 10 mm and less than 20 mm, two laser polishings are adopted, and the laser focus falls on the 1 / 4 and 3 / 4 positions of the height of the metal denture bracket respectively during the polishing process, to ensure that the laser beam focus effectively acts on all areas of the metal bracket during the laser polishing process.

[0015] Preferably, in step e, the laser processing parameters are: the laser polishing area is a rectangular area covering the bracket, the laser adopts an infrared band continuous fiber laser, the laser power is 200-800W, the laser scanning rate is 500-1200mm / s, the spot diameter is 30-100μm, the laser polishing filling method is grid filling, and the filling line spacing is 30-150μm; during the polishing process, the laser focus position is adjusted by the Z-axis displacement platform in the glove box.

[0016] The present invention is based on a laser polishing method, combined with focus height control during the polishing process, and uses a flexible tooling as a special heat dissipation fixture to achieve uniform heat dissipation, thereby achieving high-precision surface treatment of additively manufactured metal denture brackets. The beneficial technical effects of the present invention include:

[0017] (1) Laser polishing replaces manual grinding, shortens the processing steps of metal denture brackets, and improves processing efficiency. The processing is applicable to metal denture brackets of any complex shape without any consumables.

[0018] (2) According to the height difference of the denture bracket, a targeted polishing strategy is set to avoid excessive defocusing of the local area of ​​the bracket, which affects the polishing quality and causes polishing dead angles;

[0019] (3) Based on the flexible tooling design, the bracket can achieve uniform heat dissipation during the polishing process, reducing thermal stress deformation caused by poor heat dissipation at the edge. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of a single supporting module of the flexible tooling of the present invention;

[0021] Figure 2 Macroscopic photograph of the cobalt-chromium-molybdenum alloy denture bracket in Example 1 before laser polishing;

[0022] Figure 3 Macroscopic photograph of the cobalt-chromium-molybdenum alloy denture bracket after laser polishing in Example 1;

[0023] Figure 4 Macroscopic photograph of the pure titanium denture framework in Example 2 before laser polishing;

[0024] Figure 5 Macroscopic photograph of the pure titanium denture framework after laser polishing in Example 2;

[0025] Figure 6 The dimensional deviation of the cobalt-chromium-molybdenum alloy denture bracket before and after laser polishing in Example 3;

[0026] Figure 7 The dimensional deviation of the cobalt-chromium-molybdenum alloy denture bracket before and after laser polishing in Comparative Example 1;

[0027] Figure numerals: 1-base, 2-fixed support column, 3-movable support column, 4-damping block. DETAILED DESCRIPTION

[0028] The technical scheme of the present invention is described in detail below in conjunction with the drawings and Examples. The following examples are exemplary only and can only be used to explain and illustrate the technical scheme of the present invention, and cannot be interpreted as a limit to the technical scheme of the present invention. Below in conjunction with the drawings and Examples, the specific implementation mode of the present invention is further described in detail. Those who do not indicate specific conditions in the embodiments are carried out according to normal conditions or the conditions recommended by the manufacturer. Those who do not indicate the manufacturer of reagents or instruments used are all conventional products that can be obtained by commercial purchase.

[0029] The flexible tooling in the present invention comprises a plurality of support modules arranged in an array. Figure 1 This is a schematic diagram of a single support module of the flexible tooling of the present invention; the support module includes a base 1 and a support unit fixed on the base; the support unit includes a fixed support column 2, a movable support column 3 and a damping block 4 located between the fixed support column and the movable support column; the interior of the fixed support column 2 is a hollow structure, and the movable support column 3 can slide in the vertical direction in the fixed support column 2 under the action of an external force. After the external force is removed, due to the damping effect of the damping block, the movable support column 3 and the fixed support column 2 remain relatively still. Further preferably, the spacing between the support modules is 2-5mm; the diameter of the fixed support column is 2-8mm, and the maximum distance that the movable support column slides in the fixed support column is 25mm.

[0030] Embodiment 1:

[0031] A laser polishing method for additively manufacturing a removable partial metal denture bracket comprises the following steps:

[0032] a. Use additive manufacturing to form cobalt-chromium-molybdenum alloy denture brackets, and carry out stress relief annealing and support removal;

[0033] b. Place the metal denture bracket flat on the flexible tooling surface and manually press it to fully contact the metal denture bracket with the support module;

[0034] c. The height difference of the metal denture bracket was measured to be 9.2 mm, and it was determined that one-time laser polishing was used, with the laser focus at a position 4.6 mm away from the uppermost surface of the flexible tooling;

[0035] d. Place the bracket and tooling on the Z-axis displacement platform, and place the whole in a glove box filled with protective gas;

[0036] e. The laser polishing area is set to a 65mm×65mm rectangular area. The laser uses infrared band continuous fiber laser, the laser power is 800W, the laser scanning rate is 1200mm / s, the spot diameter at the focus is 30μm, and the filling line spacing is 30μm. During the polishing process, the displacement platform in the glove box is moved to complete the single-sided polishing of the metal denture bracket;

[0037] f. Turn the metal denture frame over to the other unpolished surface and repeat step be to complete the polishing of the other side of the denture.

[0038] Figure 2 and Figure 3 These are macroscopic photos of metal denture brackets before and after laser polishing. The surface roughness of laser polishing is reduced from Sa9.5μm to 0.93μm, and the polished surface is smooth and pollution-free.

[0039] Embodiment 2:

[0040] A laser polishing method for additively manufacturing a removable partial metal denture framework comprises the following steps:

[0041] a. Use additive manufacturing to form pure titanium denture framework, and carry out stress relief annealing and support removal;

[0042] b. Place the metal denture bracket flat on the flexible tooling surface and manually press it to fully contact the denture bracket with the support module;

[0043] c. The height difference of the metal denture bracket was determined to be about 15mm, and it was determined that two laser polishings were used, with the laser focus being located at 4.75mm and 11.25mm from the uppermost surface of the flexible tooling;

[0044] d. Place the bracket and tooling on the Z-axis displacement platform, and place the whole in a glove box filled with protective gas;

[0045] e. Set the laser polishing area to a 60mm×60mm rectangular area. Use infrared band continuous fiber laser. The laser power is 300W. The laser scanning rate is 500mm / s. The spot diameter at the focus is 80μm. The laser polishing filling method is grid filling. The filling line spacing is 150μm. During the laser polishing process, the laser focus height is adjusted through the Z-axis platform in the glove box to complete two polishings.

[0046] f. Turn the metal denture frame over to the other unpolished surface and repeat step be to complete the polishing of the other side of the denture.

[0047] Figure 4 and Figure 5 These are macroscopic photos of a pure titanium denture framework before and after laser polishing. The surface roughness of the laser polishing is reduced from Sa9.3μm to 0.72μm, and the polished surface is smooth and pollution-free.

[0048] Embodiment 3:

[0049] A laser polishing method for additively manufacturing a removable partial metal denture framework comprises the following steps:

[0050] a. Use additive manufacturing to form cobalt-chromium-molybdenum alloy denture brackets, and carry out stress relief annealing and support removal;

[0051] b. Place the metal denture bracket flat on the flexible tooling surface and manually press the metal denture bracket to the support.

[0052] The modules are in full contact;

[0053] c. The height difference of the metal denture bracket was determined to be 12.3 mm. It was determined that two laser polishings were used and the laser focus was split at

[0054] 3.075mm and 9.225mm from the uppermost surface of the flexible tooling;

[0055] d. Place the bracket and tooling on the Z-axis displacement platform, and place the whole in a glove box filled with protective gas;

[0056] e. The laser polishing area is set to a 65mm×50mm rectangular area. The laser uses an infrared band continuous fiber laser, the laser power is 320W, the laser scanning rate is 800mm / s, the spot diameter at the focus is 30μm, and the filling line spacing is 45μm. During the polishing process, the displacement platform in the glove box is moved to complete two polishings;

[0057] f. Turn the metal denture frame over to the other unpolished surface and repeat step be to complete the polishing of the other side of the denture.

[0058] Figure 6 The size deviation of the metal denture bracket before and after laser polishing. Through the comparison of the model size after three-dimensional scanning reconstruction, it can be seen that the average size deviation of the metal denture bracket after laser polishing is 19μm compared with that before polishing, and the maximum size deviation is 253μm.

[0059] Comparative Example 1

[0060] A laser polishing method for additively manufacturing a removable partial metal denture framework comprises the following steps:

[0061] a. Use additive manufacturing to form cobalt-chromium-molybdenum alloy denture brackets, and carry out stress relief annealing and support removal;

[0062] b. The height difference of the metal denture bracket was 12.3 mm. It was determined that two laser polishings were used and the laser focus was split at

[0063] 3.075mm and 9.225mm from the uppermost surface of the flexible tooling;

[0064] c. Place the bracket directly on the Z-axis displacement platform and place the whole in a glove box filled with protective gas;

[0065] d. The laser polishing area is set to a 65mm×50mm rectangular area. The laser uses infrared band continuous fiber laser, the laser power is 320W, the laser scanning rate is 800mm / s, the spot diameter at the focus is 30μm, and the filling line spacing is 45μm. During the polishing process, the displacement platform is moved by the displacement platform in the glove box to complete two polishings;

[0066] e. Turn the metal denture frame over to the other unpolished surface and repeat step be to complete the polishing of the other side of the denture.

[0067] Figure 7 The size deviation of the metal denture bracket before and after laser polishing. Through the comparison of the model size after three-dimensional scanning reconstruction, it can be seen that due to the lack of flexible tooling to improve the heat dissipation performance, a large amount of heat accumulated at the edge position caused serious deformation of the bracket. The average size deviation of the metal denture bracket after laser polishing was 30μm compared with that before polishing, and the maximum size deviation was 376μm.

Claims

1. A laser polishing method for additively manufacturing a removable partial metal denture framework, characterized in that: The following steps are involved: a. Stress relief annealing and support removal of additively manufactured metal denture frameworks; b. Place the metal denture bracket flat on the surface of the flexible tooling, so that the metal denture bracket is in full contact with the top of the supporting module in the flexible tooling; c. Measure the height difference of metal denture brackets and plan the single-sided laser polishing strategy; d. Place the metal denture bracket and the flexible tooling on the Z-axis displacement platform, and then place the whole in a glove box filled with protective gas; e. Set the laser processing parameters, start the laser processing system, and complete the single-sided polishing of the metal denture bracket; f. Turn the metal denture bracket over to the other unpolished surface and repeat step be to complete the polishing of the other side of the metal denture bracket.

2. The laser polishing method for additively manufactured removable partial metal denture framework according to claim 1, characterized in that: In step a, the metal denture bracket is an additively manufactured titanium alloy bracket or a cobalt alloy denture bracket.

3. The laser polishing method for additively manufactured removable partial metal denture framework according to claim 1, characterized in that: In step b, the flexible tooling includes a plurality of support modules arranged in an array, the support modules include a base and a support unit fixed on the base; the support unit includes a fixed support column, a movable support column and a damping block located between the fixed support column and the movable support column; the interior of the fixed support column is a hollow structure, and the movable support column can slide in a vertical direction inside the fixed support column under the action of an external force. After the external force is removed, the movable support column and the fixed support column remain relatively still due to the damping effect of the damping block.

4. The laser polishing method for additively manufactured removable partial metal denture framework according to claim 3, characterized in that: The spacing between the support modules in the flexible tooling is 2-5 mm; the diameter of the fixed support column is 2-8 mm, and the maximum sliding distance of the movable support column in the fixed support column is 25 mm.

5. The laser polishing method for additively manufacturing a removable partial metal denture framework according to any one of claims 1 to 4, characterized in that: The support module is made of stainless steel, titanium alloy or tungsten alloy.

6. The laser polishing method for additively manufactured removable partial metal denture framework according to claim 1, characterized in that: In step c, the laser polishing strategy is: when the height difference of the metal denture bracket is less than 10 mm, one laser polishing is adopted, and the laser focus falls on the 1 / 2 position of the height of the metal denture bracket during the polishing process; when the height difference of the metal denture bracket is greater than 10 mm and less than 20 mm, two laser polishings are adopted, and the laser focus falls on the 1 / 4 and 3 / 4 positions of the height of the metal denture bracket respectively during the polishing process.

7. The laser polishing method for additively manufactured removable partial metal denture framework according to claim 1, characterized in that: In step e, the laser processing parameters are: laser power is 200-800W, laser scanning rate is 500-1200mm / s, spot diameter is 30-100μm, laser polishing filling method is grid filling, and filling line spacing is 30-150μm; during the polishing process, the laser focus position is adjusted by the Z-axis displacement platform in the glove box.

8. The laser polishing method for additively manufactured removable partial metal denture framework according to claim 7, characterized in that: The laser polishing area is a rectangular area covering the bracket, and the laser adopts infrared band continuous fiber laser.

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