Method for preventing deformation and redundancy of ultra-thin structure metal matrix through sand blasting

Abstract

The invention discloses a method for preventing deformation and redundancy in sand blowing of an ultrathin structure metal matrix, belongs to the technical field of sand blowing protection, and aims to solve the problems that a diaphragm assembly part has structures such as welding lap joint gaps and blind holes, and the available protection area is small in the sand blowing process, so that sand grains easily enter to form redundancy which is difficult to remove, and the service life of the diaphragm assembly part is prolonged. In addition, product scrapping is easily caused by quality problems such as scratches, the reliability of product quality is seriously influenced, and the production progress is delayed. Therefore, the development of process research aiming at the quality problems such as redundancy control and scratch reduction in the sand blowing process has important practical engineering significance. According to the method, through a large number of process tests and researches, the sand blasting protection effects of various materials are compared, the method for effectively controlling the sand blasting redundancy of the diaphragm assembly is found, meanwhile, the risk of quality defects such as scratching of the parts is reduced, and the reliability of the sand blasting quality of the diaphragm assembly type parts is improved to the maximum extent.

Description

Technical Field

[0001] The invention relates to a technical method for effectively controlling excess material in sandblasting of an ultra-thin structure metal substrate and reducing the risk of product scratches, in particular to a method for protecting excess material in a sandblasting process of a diaphragm component. Background Art

[0002] The ultra-thin metal matrix has the characteristics of complex structure, high surface quality requirements and high cost. At the same time, in the manual sand blasting operation, workers need to strictly control the product thinning amount, deformation amount, excess material prevention and control, product uniformity and roughness after sand blasting and other multi-scale details, which together greatly increase the difficulty of manual sand blasting. In addition, there have been many sand blasting quality problems in the actual production process (for example, excess sand particles appeared at the weld overlap on the diaphragm assembly and other quality problems), and a lot of attempts have been made to improve it.

[0003] There are many ways to prevent and control excess materials, such as using special tools, ultrasonic washing, liquid flushing, wax filling, tape sealing, etc. For the sandblasting process of complex parts, due to their special structure and complex shape, excess materials are easy to enter, and narrow spaces are difficult to protect, etc., the cost of special tooling is too high and the protection effect is poor. Therefore, the workshop often uses tape sealing for such products. The diaphragm assembly is welded by a metal diaphragm and a support ring. The metal diaphragm is inserted into the support ring. Therefore, there is a welding lap after welding (such as Figure 1 The location where excess materials are easily generated is very difficult to protect due to its special structure and narrow space. If the protection is not in place or the protection falls off during the sand blowing process, sand particles are easy to enter, forming excess materials that are difficult to remove, which seriously affects product quality and production efficiency. Summary of the invention

[0004] The technical problem solved by the present application is: to overcome the shortcomings of the prior art and provide an ultra-thin structure metal matrix sand blasting anti-deformation and excess material technology, which can effectively control the sand blasting excess material and reduce the risk of product scratches, especially as a protection technology for excess material in the sand blasting process of diaphragm components, greatly improving the controllability of the sand blasting process, and is easy to operate and has significant effects, and can be widely used in the sand blasting of diaphragm component parts.

[0005] The technical solutions provided by this application are as follows:

[0006] A method for preventing deformation and excess material from sandblasting of an ultra-thin structured metal matrix is ​​used for protecting diaphragm assembly parts during the sandblasting process. The diaphragm assembly parts include a metal diaphragm and a support ring. The metal diaphragm is inserted into the support ring. The metal diaphragm and the support ring are welded to each other. After welding, a weld lap joint exists between the metal diaphragm and the support ring. After the weld lap joint is filled with a solid filler, the sandblasting process is performed.

[0007] The solid filler is a sodium stearate solid filler or a silicone rubber sealing strip.

[0008] When the solid filler is sodium stearate solid filler, the sodium stearate solid filler is heated and melted, and then covered in the weld lap joint, and allowed to stand until the sodium stearate solid filler solidifies, thereby completing the protection.

[0009] When the solid filler is a silicone rubber sealing strip, the radial direction of the metal diaphragm is the width direction of the welded lap joint, and the diameter of the silicone rubber sealing strip is within 0 to 1 mm larger than the width of the welded lap joint.

[0010] The sand blowing process includes: the first sand blowing, using the first group of sand for sand blowing; the second sand blowing, using the second group of sand for sand blowing; the particle size of the first group of sand is smaller than the particle size of the second group of sand.

[0011] The particle size of the first group of sand is above 100 meshes, and the particle size of the second group of sand is between 40 and 50 meshes.

[0012] The pressures of the first sand blasting process and the second sand blasting process are both 0.3-0.35 MPa.

[0013] The operation steps of the first sand blasting and the second sand blasting include: holding the spray gun and fixing the diaphragm assembly parts, keeping the protective outer surface of the diaphragm assembly parts 100-200mm away from the gun muzzle, and performing pendulum swing sand blasting.

[0014] In summary, this application at least includes the following beneficial technical effects:

[0015] Effective control is achieved on multiple dimensions such as product thinning, deformation, excess material prevention and control, and product uniformity and roughness after sand blasting. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of where the sand blowing of the welded lap joints of the diaphragm assembly is likely to produce excess material;

[0017] Figure 2 The protective status and schematic diagram before and after sand blasting after the weld lap joint is filled with sodium stearate, an easy-to-remove filling medium;

[0018] Figure 3 The protective status and schematic diagram of the welded lap joints protected by foamed silicone rubber sealing strips (square strips) before and after sand blasting;

[0019] Figure 4 This is a schematic diagram of the protection status before and after sand blasting after using foam silicone rubber sealing strips (round strips) to protect the welded lap joints.

[0020] Explanation of the accompanying drawings: 1. Metal diaphragm; 2. Support ring; 3. Welded lap joint; 4. Solid filler. DETAILED DESCRIPTION

[0021] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments disclosed in the present invention will be further described in detail below with reference to the accompanying drawings.

[0022] The embodiment of the present application discloses a method for preventing deformation and excess material in sandblasting of an ultra-thin structure metal substrate, which is used for the protection of diaphragm assembly parts during sandblasting. The diaphragm assembly parts include a metal diaphragm 1 and a support ring 2. The metal diaphragm is inserted into the support ring. The metal diaphragm and the support ring are welded together. After welding, there is a welding lap joint 3 between the metal diaphragm and the support ring. The location of the welding lap joint 3 is an area that is prone to produce excess material. Solid fillers are added to the original protection method using medical tape for sandblasting protection. The grooves on the diaphragm assembly that are prone to produce excess material are tightly filled with solid fillers 4. The location of the grooves on the diaphragm assembly that are prone to produce excess material can be seen. Figure 1 .

[0023] The solid filler 4 is a sodium stearate solid filler or a silicone rubber sealing strip.

[0024] When the solid filler 4 is a sodium stearate solid filler, the sodium stearate solid filler is heated and melted and then covered on the groove of the diaphragm assembly. After standing for 2 hours, the sodium stearate solid filler solidifies and the protection is completed.

[0025] The silicone rubber sealing strip 4 is made of a soft polymer elastic material. When the solid filler is a silicone rubber sealing strip, the difference between the diameter of the silicone rubber sealing strip and the width of the diaphragm assembly groove is within the range of 0 to 1 mm. The square strip is 2 mm × 2 mm; the round strip is Φ2 mm.

[0026] The grooves on the diaphragm assembly that are prone to produce excess material are tightly filled with foamed silicone rubber sealing strips to prevent sand particles from entering during the sand blasting process. At the same time, due to the excellent elasticity and smooth surface of the foamed silicone rubber sealing strips, the risk of product scratches is greatly reduced. Combined with the refinement and quantification of the sand blasting process, the controllability of the sand blasting process is guaranteed, ensuring the quality, safety and reliability of the product.

[0027] The sand blasting process must be refined and quantified in strict accordance with the product sand blasting operation procedures and operating requirements.

[0028] The product sand blasting operation process includes pre-product inspection, pre-sand blasting protection, sand blasting process, post-sand blasting cleaning, roughness comparison, protection removal, post-product inspection, and product turnover.

[0029] The operation process of product sand blasting is as follows: First sand blasting: First select Group I sand (above 100 mesh), set the pressure to 0.3MPa, hold the spray gun and fix the diaphragm assembly, keep the protective outer surface of the diaphragm assembly 100-200mm away from the muzzle, and perform pendulum-style swing sand blasting to ensure that the sand blasting time at each point is controlled within 4s. Second sand blasting: Select 40 mesh new sand, set the pressure to 0.3MPa, hold the spray gun, fix the diaphragm assembly, keep the protective outer surface of the diaphragm assembly 100-200mm away from the muzzle, and perform pendulum-style swing sand blasting to ensure that the sand blasting time at each point is controlled within 4s.

[0030] The sand particle size of the two sand blasting processes is first fine and then coarse. Under the same sand blasting time, the first sand blasting can better remove the oxide layer, and the deformation of diaphragm components can be avoided during the entire sand blasting process. The pressure of the first and second sand blasting processes is smaller, and the deformation of the metal diaphragm is smaller.

[0031] In order to improve the sand blasting protection effect, the original sand blasting protection method was compared and analyzed. It is planned to explore the sand blasting protection method from two aspects (easily removable medium filling, tape protection combined with solid filling). The process test process involved in this technology is as follows.

[0032] Test 1:

[0033] Choose an easy-to-remove filling medium for sandblasting protection. By comparing wax filling, animal fat filling, polyvinyl alcohol resin filling, sodium stearate filling, etc., it is decided to use sodium stearate as a filler that is easy to fill at low temperature and easy to clean when heated.

[0034] The main ingredients of this sodium stearate solid filler are: sodium stearate, sorbitol, glycerin, deionized water, etc. The above ingredients are mixed evenly according to a certain ratio, and the sodium stearate solid filler is heated for saponification reaction immediately. The sodium stearate solid filler is commercially available. It is a solid block at room temperature and can be cut into any shape. It has a certain elasticity and can be bent, and its hydrophilicity at room temperature is poor and it is not easily soluble in cold water. The main ingredients are introduced as follows: Sodium stearate, also known as sodium octadecanoate, has a molecular formula of C18H35NaO2, is a white oily powder, has a relative molecular weight of 306.46, a melting point of 270°, has good water absorption, can be dissolved in cold water, is easily soluble in hot water and hot alcohol, and is commonly used in detergents and emulsifiers. Sorbitol, also known as hexadecene, has a molecular formula of C6H14O6, a relative molecular weight of 182.17, and is a non-volatile polyol, non-toxic and tasteless. White crystal or crystalline powder, easily soluble in water, insoluble in organic solvents, melting point 98-100°, boiling point 216°, PH value of 60% aqueous solution is 6-7. Commonly used as plasticizer, humectant, filler, etc.

[0035] The solid filler is heated and melted and then covered on the groove of the diaphragm assembly. After standing for 2 hours, the solid filler solidifies and then the diaphragm assembly is placed in a sand blowing machine for sand blowing operation.

[0036] First sand blasting: first select Group I sand (above 100 mesh), set the pressure to 0.3MPa, hold the spray gun, fix the diaphragm assembly, keep the protective outer surface of the diaphragm assembly 100-200mm away from the muzzle, and perform pendulum-style swing sand blasting to ensure that the sand blasting time at each point is controlled within 4s.

[0037] Second sand blasting: Use new sand of 40 mesh, set the pressure to 0.3MPa, hold the spray gun, fix the diaphragm assembly, keep the protective outer surface of the diaphragm assembly 100-200mm away from the muzzle, and perform pendulum-style sand blasting to ensure that the sand blasting time at each point is controlled within 4s.

[0038] Figure 2 (a) is the state after solid filling and protection of sodium stearate before sand blasting. Figure 2 (b) is the state after solid filling and protection of sodium stearate after sand blasting. Figure 2 (c) is a schematic diagram of sodium stearate solid filling protection before sand blasting. Figure 2 (d) is a schematic diagram of the protection of sodium stearate solid filling after sand blasting. After sand blasting, the sodium stearate solid filling can effectively protect the grooves that need to be protected and the gaps that are prone to produce excess materials.

[0039] Test 2: Solid fillers were added to the original tape protection method for sand blowing protection. After comparing various solid fillers, soft silicone rubber sealing strips were selected for testing (taking the protection of a certain diaphragm component as an example, square strips with a size of 2mm×2mm or round strips with a size of Φ2mm were selected. Subsequently, silicone rubber sealing strips of appropriate sizes were selected according to the product structure. The difference between the diameter of the silicone rubber sealing strip and the width of the diaphragm component groove was within the range of 0 to 1mm).

[0040] The silicone rubber is a new type of high molecular elastic material, with excellent high temperature resistance (180-200℃) and low temperature resistance (-40-60℃), good physiological stability, excellent resilience and small permanent deformation (200℃, 48h not more than 50%). At the same time, the silicone rubber sealing strip has a transparent and smooth surface, excellent elasticity (Shore 35-75 degrees), non-toxic and tasteless, high temperature resistance (-70℃-250℃), and is not easy to age, deform, and resistant to slight acid and alkali.

[0041] Rubber foaming refers to a method of treating rubber with a specific foaming agent so that the rubber has characteristic properties, such as lightness, wear resistance and good elasticity.

[0042] Foamed silicone rubber sealing strips (square strips or round strips) for protection. Fill the groove of the diaphragm assembly with foamed silicone rubber sealing strips (square strips: 2mm×2mm; round strips: Φ2mm). The foamed silicone rubber sealing strips have good elasticity and there is no contact gap in the groove after filling. After blocking the welding overlap gap, cover it with medical tape, and then place the diaphragm assembly into the sand blasting machine for sand blasting.

[0043] First sand blasting: first select Group I sand (above 100 mesh), set the pressure to 0.3MPa, hold the spray gun, fix the diaphragm assembly, keep the protective outer surface of the diaphragm assembly 100-200mm away from the muzzle, and perform pendulum-style swing sand blasting to ensure that the sand blasting time at each point is controlled within 4s.

[0044] Second sand blasting: Use new sand of 40 mesh, set the pressure to 0.3MPa, hold the spray gun, fix the diaphragm assembly, keep the protective outer surface of the diaphragm assembly 100-200mm away from the muzzle, and perform pendulum-style sand blasting to ensure that the sand blasting time at each point is controlled within 4s.

[0045] Figure 3 (a) is the actual state of the foamed silicone rubber sealing strip (square strip) after protection and before sandblasting. Figure 3 (b) is a schematic diagram of the protection by the foamed silicone rubber sealing strip (square strip). Figure 3 (c) is the actual state of the foamed silicone rubber sealing strip (square strip) after sandblasting protection. Figure 3 (d) is a schematic diagram of the foamed silicone rubber sealing strip (square strip) after sand blowing protection. Figure 4 (a) is the actual state of the foamed silicone rubber sealing strip (round strip) before sandblasting. Figure 4 (b) is a schematic diagram of the foamed silicone rubber sealing strip (round strip) before sand blowing protection. Figure 4 (c) is the actual state of the foamed silicone rubber sealing strip (round strip) after sandblasting. Figure 4 This is a schematic diagram of the foamed silicone rubber sealing strip (round strip) after sand blasting. After comparison, the grooves on the diaphragm assembly that are prone to produce excess materials were tightly filled with the foamed silicone rubber sealing strip. No sand particles were found in the grooves after sand blasting. This protection method is effective and reliable. The silicone rubber sealing strip has a smooth surface and excellent elasticity, which can greatly reduce the risk of product scratches during sand blasting.

[0046] Refinement and quantification of sand blasting operation process

[0047] The product sand blasting operation process is: pre-product inspection → pre-sand blasting protection → sand blasting process → post-sand blasting cleaning → roughness comparison → protection removal → post-product inspection → product turnover.

[0048] Pre-product inspection: The operator checks that there are no foreign objects on the operating table and that it is flat. At the same time, a sponge pad is laid flat on the operating table. Then, the diaphragm assembly is placed on the operating table from the transfer box with both hands, and a strong flashlight is used to directly illuminate the diaphragm assembly. The surface quality is inspected visually and with a 30x magnifying glass. First, place the diaphragm assembly flat on the operating table to check the outer surface, and then turn the diaphragm assembly over and place it in a plastic basin to check the inner surface. After the inspection is completed, the diaphragm assemblies are placed in the plastic basin one by one, and placed in a fixed parts placement area. During the entire process, the operator and inspector check the surface of the diaphragm assembly one by one to see if there are any defects such as bumps, bulges, pits, protrusions, scratches, etc., and record the inspection results in the surface quality section of the production record sheet, which is signed and stamped by the operator and inspector.

[0049] Protection before sand blasting: The operator takes the parts from the transfer box to the operating table with both hands, and handles them gently to avoid bumps and scratches. On the operating table, the operator performs sand blasting protection on the parts one by one, and puts the individual diaphragm components back into the plastic basin in time after protection. After completing the sand blasting protection of all diaphragm components in this batch, the sand blasting process is uniformly carried out. Partial sand blasting on the outer surface of the diaphragm component: First, use silicone rubber sealing strips to fill the grooves on the diaphragm component that are prone to produce excess materials, and ensure that the filler is close to the bottom of the groove. After filling, use medical tape to protect the non-sand blasting parts (the parts below the support ring are not sand blasted, that is, the upper end of the second rib of the metal diaphragm is below 2mm, and the sand blasting boundary is allowed to deviate 1-3mm upward). At the intersection produced during the protection process of medical tape, ensure that one medical tape covers the other medical tape, and the coverage range is 30 to 50mm beyond the intersection. After the protection is completed, the operator and inspector will confirm it, and record the inspection situation in the surface quality of the production record sheet, and the operator and inspector will sign and seal it.

[0050] Sand blasting process: Check the status of sand blasting equipment: Before placing the diaphragm assembly into the sand blasting equipment, check whether the equipment is in good condition and whether the protective rubber guard plate has fallen off. If there is a problem, stop the sand blasting process in time and wait until the problem is solved before proceeding with the sand blasting process. For the first sand blasting, use Group I sand (above 100 mesh), set the pressure to 0.25±0.05MPa, hold the spray gun, fix the diaphragm assembly, and keep the outer surface of the diaphragm assembly 100-200mm away from the gun. When sand blasting at a position 30-50mm above the upper end of the second rib of the metal diaphragm, the spray gun blows sand from top to bottom to ensure that the sand blasting angle is 70-90°, slowly rotate the diaphragm assembly, prohibit fixed sand blasting at a local position, and perform pendulum swing sand blasting to ensure that the sand blasting time at each point is controlled within 4s, and the sand blasting part is visually uniform gray. When sanding the position below 30-50mm on the upper end of the second rib of the metal diaphragm, the spray gun blows obliquely from bottom to top to ensure that the sand blowing angle is less than 90°, slowly rotate the diaphragm assembly, prohibit fixed sand blowing at local positions, and perform pendulum swing sand blowing to ensure that the sand blowing time at each point is controlled within 4s, and the sand blowing part is visually uniform gray. For the second sand blowing, use 40 mesh new sand, set the pressure to 0.25±0.05MPa, hold the spray gun, fix the diaphragm assembly, and keep the outer surface of the diaphragm assembly 100-200mm away from the muzzle. When sanding the position above 30-50mm on the upper end of the second rib of the metal diaphragm, the spray gun blows sand from top to bottom to ensure that the sand blowing angle is 70-90°, slowly rotate the diaphragm assembly, prohibit fixed sand blowing at local positions, and perform pendulum swing sand blowing to ensure that the sand blowing time at each point is controlled within 4s, and the sand blowing part is visually uniform gray. When blowing sand at the position 30 to 50 mm below the upper end of the second rib of the metal diaphragm, the spray gun should blow obliquely from bottom to top to ensure that the sand blowing angle is less than 90°. Slowly rotate the diaphragm assembly. It is prohibited to blow sand at a fixed position locally. Perform pendulum-style swing sand blowing to ensure that the sand blowing time at each point is controlled within 4s. Visually, the sand blowing area is a uniform gray color.

[0051] Cleaning after sand blasting: After sand blasting is completed, first use low-pressure air to blow away the floating sand on the inner and outer surfaces of the diaphragm assembly, and place it back into the plastic basin. After the sand blasting process of all diaphragm assemblies in this batch is completed, they will be uniformly inspected and protectively removed.

[0052] Roughness comparison: Operators and inspectors compare all sandblasting parts with sandblasting surface roughness comparison samples to confirm whether their surface roughness is within the Ra3.2 to Ra6.4 level.

[0053] Protection removal: Transfer the diaphragm assembly to the operating table. One operator fixes the diaphragm assembly with both hands, and another operator uses a vacuum cleaner to further remove the sand powder residue. Then use a clean white silk cloth dipped in anhydrous ethanol to wipe off the remaining sand powder on the medical tape. Then one operator turns the diaphragm assembly over with both hands so that the sandblasting surface of the diaphragm assembly is facing vertically downward. Another operator is responsible for removing the medical tape protection. At the same time, after the protection is removed, an operator uses a clean white silk cloth dipped in anhydrous ethanol to wipe off the remaining sand powder on the silicone rubber sealing strip. During the removal and wiping process, place the diaphragm assembly in a plastic basin and place a sponge inside it to reduce the risk of parts damage.

[0054] Post-product inspection: Place the diaphragm assembly on the operating table with both hands. Use a strong flashlight to shine directly on the diaphragm assembly, and use visual inspection and a 30x magnifying glass to check the surface quality. First, place the diaphragm assembly flat on the operating table to check the outer surface, and focus on checking whether there are sand particles in the gaps on the outer surface of the diaphragm assembly. During the whole process, the operator and inspector check the surface of the diaphragm assembly one by one to see if there are any defects such as bumps, bulges, pits, protrusions, scratches, and excess objects.

[0055] Product turnover: It is strictly forbidden to touch the sandblasting surface with bare hands after sandblasting. After the inspection is completed, the diaphragm components shall be placed in the transfer box in sequence (during the transfer and packing process, the operator shall put the diaphragm components into the transfer box one by one with both hands, and handle them with care), and place them in a fixed parts placement area.

[0056] The contents not described in detail in this application specification belong to the common knowledge of those skilled in the art.

[0057] The present application is described in detail above in conjunction with specific implementation methods and exemplary examples, but these descriptions cannot be understood as limiting the present application. Those skilled in the art understand that, without departing from the spirit and scope of the present application, a variety of equivalent replacements, modifications or improvements can be made to the technical solution of the present application and its implementation methods, all of which fall within the scope of the present application. The scope of protection of the present application shall be subject to the attached claims.

Claims

1. A method for sandblasting an ultra-thin metal substrate to prevent deformation and excess material, characterized in that: Used for the protection of diaphragm assembly parts during the sand blowing process. The diaphragm assembly parts include a metal diaphragm and a support ring. The metal diaphragm is inserted into the support ring. The metal diaphragm and the support ring are welded together. After welding, there is a welding lap joint between the metal diaphragm and the support ring. After the welding lap joint is filled with solid filler, the sand blowing process is carried out.

2. The method for sandblasting an ultra-thin structure metal substrate to prevent deformation and excess material according to claim 1, characterized in that: The solid filler is a sodium stearate solid filler or a silicone rubber sealing strip.

3. The method for sandblasting an ultra-thin structure metal substrate to prevent deformation and excess material according to claim 1, characterized in that: When the solid filler is sodium stearate solid filler, the sodium stearate solid filler is heated and melted, and then covered in the weld lap joint, and allowed to stand until the sodium stearate solid filler solidifies, thereby completing the protection.

4. The method for sandblasting an ultra-thin structure metal substrate to prevent deformation and excess material according to claim 1, characterized in that: When the solid filler is a silicone rubber sealing strip, the radial direction of the metal diaphragm is the width direction of the welded lap joint, and the diameter of the silicone rubber sealing strip is within a range of 0 to 1 mm greater than the width of the welded lap joint.

5. The method for sandblasting an ultra-thin structure metal substrate to prevent deformation and excess material according to claim 1, characterized in that: The sand blowing process includes: the first sand blowing, using the first group of sand for sand blowing; the second sand blowing, using the second group of sand for sand blowing; the particle size of the first group of sand is smaller than the particle size of the second group of sand.

6. The method for sandblasting an ultra-thin structure metal substrate to prevent deformation and excess material according to claim 5, characterized in that: The particle size of the first group of sand is above 100 meshes, and the particle size of the second group of sand is between 40 and 50 meshes.

7. The method for sandblasting an ultra-thin structure metal substrate to prevent deformation and excess material according to claim 5, characterized in that: The pressures of the first sand blasting process and the second sand blasting process are both 0.3-0.35 MPa.

8. The method for sandblasting an ultra-thin structure metal substrate to prevent deformation and excess material according to claim 5, characterized in that: The operation steps of the first sand blasting and the second sand blasting include: holding the spray gun and fixing the diaphragm assembly parts, keeping the protective outer surface of the diaphragm assembly parts 100-200mm away from the gun muzzle, and performing pendulum swing sand blasting.

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