Machining process for protecting precision of machined surface

Abstract

The invention provides a machining process for protecting the precision of a machined surface, which sequentially comprises the following steps of: performing surface shot blasting treatment on a welded to-be-machined part, and spraying primer on the surface of the shot-blasted to-be-machined part in an air spraying manner; the primer sprayed on the surface of the workpiece to be machined is dried; machining the workpiece to be machined after the surface primer is dried; finish paint is sprayed on the surface of the machined workpiece to be machined; and drying the finish paint. Therefore, the shot blasting treatment procedure is carried out before machining, a protection plate does not need to protect a to-be-machined part subjected to machining during shot blasting treatment, cutting fluid used in the machining process has no influence on the performance of sprayed primer, and under the condition that the same machining purpose is achieved, the service life of the to-be-machined part is prolonged. By simply adjusting the machining procedure, the investment of a protection plate and the investment of fastening standard parts, namely bolts and nuts can be saved, the machining efficiency is improved, and the cost is saved.

Description

Technical Field

[0001] The invention relates to the technical field of coating, and in particular to a processing technology for protecting the precision of machined surfaces. Background Art

[0002] At present, as water-based paint replaces solvent-based paint (paint) on products, water-based paint has more stringent requirements on the surface pretreatment of parts. Usually, the surface pretreatment methods of parts include manual pretreatment (manual grinding), mechanical pretreatment (shot blasting), and chemical pretreatment (pickling, phosphating). Usually, for machined welded parts, the workpiece needs to be shot blasted before painting. During the shot blasting process, the steel shot particles are thrown out by the high-speed rotating shot blasting machine blades and evenly cover the entire workpiece surface. This process cannot avoid the machined surfaces and holes. In order to ensure that the machined surfaces and holes are not damaged by the steel shots, it is necessary to install protective plates, covers or sleeves on the machined surfaces and holes for protection. This type of protective material usually uses Q235B steel plates with a thickness of 8-10mm. About 63-78kg of steel plates are required per square meter. If there are special-shaped machined surfaces, the protective plates are cut. The utilization rate of steel during production is only 20-40%, and a large amount of steel waste is wasted. At the same time, when the protective plate, cover or sleeve is used to protect the workpiece, it is also necessary to use standard bolts and nuts to fix it. The shot blasting process will also damage the studs, resulting in the difficulty of removing the bolts after shot blasting, which adds trouble to subsequent work and increases cost investment. The protective effect is short-lived and local surfaces are damaged due to deformation of the protective plate. At the same time, if the protective plate is not installed on some processed surfaces due to negligence of the workers, the processed surfaces will be damaged during shot blasting, affecting product quality, and subsequent repairs will reduce production efficiency. Summary of the invention

[0003] The main purpose of the present invention is to provide a processing technology for protecting the precision of machined surfaces, so as to at least solve the problem that the processing process of the prior art requires the use of a protective plate, resulting in high processing costs and low efficiency.

[0004] In order to achieve the above object, the present invention provides a processing technology for protecting the machining surface accuracy, comprising:

[0005] Step 1: Shot blast the surface of the workpiece after welding;

[0006] Step 2, spraying primer on the surface of the workpiece after shot blasting by air spraying;

[0007] Step 3, drying the primer sprayed on the surface of the workpiece;

[0008] Step 4, mechanically processing the workpiece after the surface primer is dried;

[0009] Step 5, spraying topcoat on the surface of the workpiece after mechanical processing;

[0010] Step 6: Dry the topcoat.

[0011] Optionally, after step 4, the method further includes: degreasing and shielding the surface of the workpiece after mechanical processing.

[0012] Optionally, after step 5, the method further includes: roughening the dried primer surface of the workpiece.

[0013] Optionally, the step 1 includes: using a shot blasting machine to spray high-speed rotating shot blasting particles onto the surface of the workpiece to be processed to remove surface impurities.

[0014] Optionally, the parameters set for spraying the primer by air spraying include:

[0015] The air pressure is 0.3-0.6Mpa, the nozzle diameter is Φ1.5-2.0, the spray gun moving speed is 200-300mm / s, and the spray dry film thickness is 45-60μm.

[0016] Optionally, in step 2, the primer is any one of iron red epoxy anti-rust primer, iron red epoxy ester primer, and polyurethane primer.

[0017] Optionally, the topcoat is any one of a polyurethane aliphatic topcoat, a polyurethane aromatic topcoat, and an alkyd topcoat.

[0018] Optionally, the step 3 comprises: placing the workpiece to be processed with the primer sprayed on the sprayed surface into a burner preheated to 70-100° C. for drying for 30-40 minutes.

[0019] The technical solution of the present invention is a processing technology for protecting the precision of machined surfaces, which is processed in sequence according to the following process: subjecting the workpiece to be processed after welding to surface shot blasting treatment, spraying primer on the surface of the workpiece to be processed after shot blasting treatment by air spraying; drying the primer sprayed on the surface of the workpiece to be processed; machining the workpiece to be processed after the surface primer is dried; spraying topcoat on the surface of the workpiece to be processed after machining; and drying the topcoat. Therefore, the shot blasting process is placed before machining, so that when shot blasting treatment is performed, no protective plate is required to protect the machined workpiece to be processed, and the cutting fluid used in the machining process has no effect on the performance of the sprayed primer. Under the condition of achieving the same machining purpose, the investment in protective plates, bolts and nuts for fastening standard parts can be saved by simply adjusting the machining process, thereby improving machining efficiency and saving costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0021] Figure 1 The present invention is an optional processing flow chart for protecting the machining surface accuracy according to an embodiment of the present invention. DETAILED DESCRIPTION

[0022] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0023] like Figure 1 As shown, a processing technology for protecting the machining surface precision includes the following steps:

[0024] Step 1: Shot blast the surface of the workpiece after welding;

[0025] Step 2, spraying primer on the surface of the workpiece after shot blasting by air spraying;

[0026] Step 3, drying the primer sprayed on the surface of the workpiece;

[0027] Step 4, mechanically processing the workpiece after the surface primer is dried;

[0028] Step 5, spraying topcoat on the surface of the workpiece after machining;

[0029] Step 6: Dry the topcoat.

[0030] Specifically, step 1, for the welded workpiece to be processed, first perform shot blasting to remove the surface oxide layer, rust, oil stains and other attachments, and at the same time make the surface reach a certain roughness to increase the adhesion of the subsequent coating.

[0031] Step 2. Spraying primer on the surface of the workpiece can enhance the adhesion between the coating and the substrate, penetrate into the tiny pores on the surface of the substrate of the workpiece, and firmly adhere to the substrate, providing a good foundation for the subsequent application of topcoat, ensuring that the topcoat can be evenly coated on the primer layer and is not easy to peel or crack. Air spraying is a coating technology that uses compressed air to atomize the paint and spray it evenly onto the surface of the workpiece. It has high coating efficiency, uniform and good coating quality, strong adaptability and easy operation. By using air spraying, the paint can be quickly covered on large areas or complex-shaped workpieces, improving production efficiency; at the same time, the atomized paint can adhere to the surface of the workpiece more evenly to form a smooth and delicate coating; in addition, air spraying is also suitable for a variety of coatings and materials to meet different coating needs.

[0032] Step 3: Primers usually contain solvents, such as water or organic solvents, which help the paint flow and cover during the spraying process. During the drying process, the solvent gradually evaporates from the coating film, allowing the pigments and solid components in the paint to combine with each other to form a continuous coating film. If the primer is not dried, the solvent will remain in the coating film, which will cause the coating film to become soft and sticky, which is not conducive to subsequent processing.

[0033] Step 4: Mechanically process the workpiece sprayed with primer. Mechanical processing includes cutting, grinding, drilling, milling and other processes, aiming to achieve the required dimensional accuracy and shape requirements. After long-term production practice, the applicant found that it is difficult for oil stains in the mechanical processing process to penetrate the paint film and enter the steel surface. Since the cutting fluid has a certain permeability to steel, adjusting the machining process after spraying the primer can prevent the cutting fluid from affecting the exposed steel surface and effectively improve the adhesion of the paint film. If the steel surface is directly exposed without spraying paint, it is easy for residual adhesion to be not conducive to the adhesion requirements of the paint film and affect the subsequent coating quality.

[0034] Step 5: Spray the topcoat on the surface of the machined workpiece. The topcoat can form a dense coating film, covering the primer and the surface of the substrate, isolating harmful factors such as moisture, oxygen, ultraviolet rays, pollutants, etc. in the external environment, thereby protecting the surface of the object from erosion and damage.

[0035] Step 6: After spraying the topcoat, the solvent or water in the paint needs to evaporate so that the solid components such as pigments and resins can combine with each other to form a continuous coating film. The drying process is the process of solvent or water evaporation, which allows the coating film to gradually solidify and reach a certain hardness and strength. If the topcoat is not dried, the coating film will remain soft and sticky, and it will not form a stable protective layer.

[0036] In the present application, the workpiece to be processed after the welding process is completed is directly transferred to the painting workshop for shot blasting, primer spraying, and primer drying in sequence, and then transferred to the machining workshop for corresponding machining processes (such as boring, milling, cylindrical surface machining, etc.) on the workpiece to be processed as required, and finally sprayed or covered with topcoat as required; after adjustment, the shot blasting process is placed before machining, so that when shot blasting is performed, no protective plate is required to protect the machined workpiece to be processed, and the cutting fluid used in the machining process has no effect on the performance of the sprayed primer. Under the condition of achieving the same processing purpose, the investment in protective plates and the investment in fastening standard parts bolts and nuts can be saved by simply adjusting the processing procedures, thereby improving processing efficiency and saving costs.

[0037] In addition, based on the cost of the protective plates for the Q16 upper / lower supports, each tower crane has one upper support and one lower support. The steel auxiliary materials required for the protective plates are about 200kg. Based on 100 sets per year, 20T of steel raw materials are needed. Based on the fact that each set of protective plates is reused five times, they will deform and the protective effect will be poor, the total amount of steel is 20T*20%=4T, about 20,000 yuan (excluding the cost of cutting and processing the protective plates). If the protection of other models or other products is added, a lot of expenses can be saved every year.

[0038] In a possible implementation manner, after step 4, the method further includes: degreasing and shielding the surface of the workpiece after machining.

[0039] Specifically, degreasing: mainly to clean the oil stains on the surface of the workpiece. The sources of oil stains mainly include the residual cutting fluid used in machining on the surface of the workpiece to be machined, and the lubricant or sweat stains on the operator's gloves. Shielding: This process is to shield and protect the parts that do not need to be painted before spraying the topcoat, such as applying calcium-based grease, peelable paint or waste newspapers to protect the processing surface.

[0040] In a possible implementation manner, after step 5, the method further includes: roughening the dried primer surface of the workpiece.

[0041] Specifically, the present application adopts a roughening treatment, which can remove the minor defects and weak adhesion areas that may exist on the primer surface by cross-grinding the primer surface to be sprayed, so as to make the contact between the topcoat and the primer surface closer, increase the physical bonding force between the topcoat and the primer, thereby improving the adhesion of the topcoat and ensuring the stability and durability of the coating quality. At the same time, for the workpiece to be processed that has been sprayed with primer, appropriate roughening treatment can also help the newly sprayed topcoat to better blend with the original paint layer to form a more solid coating system. In addition, through the roughening treatment, it is possible to observe and evaluate whether the cutting fluid has caused damage to the sprayed paint film. During the roughening process, if the polished paint film is powdery and there is no block adhesion on the gauze, this indicates that the cutting fluid has not destroyed the integrity of the paint film, the paint film has good adhesion, and meets the coating requirements. The roughening methods include manual roughening, mechanical roughening and chemical roughening.

[0042] In a possible implementation, step 1 includes: using a shot blasting machine to spray high-speed rotating shot blasting particles onto the surface of the workpiece to be processed to remove surface impurities.

[0043] Specifically, the shot blasting machine uses high-speed rotating shot blasting particles to impact and scrape the surface of the workpiece, which can quickly and effectively remove impurities such as oil, rust, and oxide layers on the surface, which is more efficient than traditional chemical cleaning or manual polishing. In addition, the shot blasting machine can handle workpieces of various shapes and sizes, whether it is large castings, forgings or complex mechanical parts, and can effectively clean them.

[0044] In a possible implementation, the parameters set for spraying the primer by air spraying include:

[0045] The air pressure is 0.3-0.6Mpa, the nozzle diameter is Φ1.5-2.0, the spray gun moving speed is 200-300mm / s, and the spray dry film thickness is 45-60μm.

[0046] Specifically, the air pressure is set within the range of 0.3-0.6Mpa, which can ensure that the paint is fully atomized, forming a fine and uniform paint mist, improving the spraying quality and making the paint film smoother and flatter. At the same time, appropriate air pressure can also help improve spraying efficiency and reduce paint waste.

[0047] Likewise, the spraying parameters used in spraying the topcoat of the present application may be consistent with the spraying parameters set for spraying the primer.

[0048] The nozzle diameter range is set at Φ1.5-2.0, which is suitable for spraying a variety of coatings and can ensure that the coating is sprayed at an appropriate flow rate. A smaller nozzle diameter helps to form a finer paint mist, while a larger diameter is suitable for spraying coatings with higher viscosity. By selecting the appropriate nozzle diameter, you can ensure that the coating is evenly covered on the surface of the workpiece and improve the spraying quality.

[0049] The spray gun movement speed is set within the range of 200-300mm / s, which can ensure that the paint is evenly covered on the surface of the workpiece to avoid missed spraying or repeated spraying. In addition, a stable spray gun movement speed can also help improve the thickness uniformity of the coating, thereby improving the overall performance of the coating. The spray dry film thickness is set within the range of 45-60μm, which helps to improve the corrosion resistance and wear resistance of the coating, and also helps to extend the service life of the coating.

[0050] In a possible implementation, in step 2, the primer is any one of iron red epoxy anti-rust primer, iron red epoxy ester primer, and polyurethane primer.

[0051] Specifically, red epoxy anti-rust primer, iron red epoxy ester primer and polyurethane primer are high-quality primer options, all of which have excellent anti-corrosion properties and can effectively protect metal materials from corrosion and extend their service life. At the same time, these types of primers have good adhesion to the metal surface, ensuring the stability and durability of the coating.

[0052] In a possible implementation, the topcoat is any one of a polyurethane aliphatic topcoat, a polyurethane aromatic topcoat, and an alkyd topcoat.

[0053] Specifically, polyurethane aliphatic topcoat, polyurethane aromatic topcoat and alkyd topcoat all have stronger weather resistance, can resist UV rays and external environmental erosion, and maintain bright colors and coating integrity for a long time. At the same time, they also have good anti-corrosion and wear resistance, can effectively extend the service life of the coated objects and resist erosion by various chemicals. In terms of adhesion, they can firmly adhere to various substrates to ensure the stability and durability of the coating.

[0054] In a possible implementation, step 3 includes: placing the workpiece to be processed with the primer sprayed on the sprayed surface into a burner preheated to 70-100° C. for drying for 30-40 minutes.

[0055] Specifically, by preheating the burner to a preset temperature in advance, the drying speed of the primer can be significantly increased. In addition, within the temperature range of 70-100°C, the solvent in the primer can evaporate faster, thereby shortening the drying time and further improving production efficiency.

[0056] The present application is further described by the following tests:

[0057] 1. Test equipment and consumables:

[0058] 1-2 steel plate specimens (t10), equipment (tower crane coating line), cleaning agent, container with cutting fluid, sandpaper, cotton yarn, adhesion tester.

[0059] 2. Test content and results

[0060] 1. Prepare t10 steel plate specimens and perform shot blasting (grade Sa2.5)

[0061] 2. Spray the primer on the shot blasted specimen and let it dry.

[0062] 3. Place the primer-sprayed specimen in the cutting fluid and soak it for about 4 hours.

[0063] 4. After cleaning and degreasing the immersed specimens, the results showed that the paint film had good integrity and no abnormalities.

[0064] 5. The coating of the test piece was properly polished (polished to a matte state and sand marks were clearly visible) to remove residual dirt on the surface and increase the adhesion of the paint film; after polishing, the paint film on the test piece was carefully observed. The results showed that no abnormal phenomena such as cracks, peeling, discoloration, uneven wear or other forms of damage were found.

[0065] 6. Spray red topcoat on the polished surface of the specimen and let it dry.

[0066] 7. Make a series of regular cross-cut patterns on the surface of the dried and cured topcoat. These cut lines should penetrate into the bottom layer of the paint film but should not touch the substrate. After a period of rest (usually 3-5 minutes), quickly pull off the tape in the vertical direction (90° or 60°). Then, carefully observe the peeling of the paint film at the intersection of the cuts. Result: The cut edge is completely smooth, and there is no paint shedding and no cracking.

[0067] The above tests show that by adjusting the coating process sequence in the machining process, the results show that the cutting fluid has no effect on the paint film. Therefore, by adjusting the process sequence, it is possible to ensure the accuracy requirements of the machined surface while also meeting the coating quality requirements and improving production efficiency. While solving the problem, it also greatly reduces the investment cost of protective tooling.

[0068] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A processing technology for protecting the surface accuracy of machined surfaces, characterized in that: include: Step 1: Shot blast the surface of the workpiece after welding; Step 2, spraying primer on the surface of the workpiece after shot blasting by air spraying; Step 3, drying the primer sprayed on the surface of the workpiece; Step 4, mechanically processing the workpiece after the surface primer is dried; Step 5, spraying topcoat on the surface of the workpiece after mechanical processing; Step 6: Dry the topcoat.

2. A processing technology for protecting the surface accuracy of a machine according to claim 1, characterized in that: After step 4, the method further includes: degreasing and shielding the surface of the workpiece after mechanical processing.

3. A processing technology for protecting the surface accuracy of a machine according to claim 1, characterized in that: After step 5, the method further includes: roughening the dried primer surface of the workpiece.

4. A processing technology for protecting the surface accuracy of a machine according to claim 1, characterized in that: The step 1 comprises: using a shot blasting machine to spray high-speed rotating shot blasting particles onto the surface of the workpiece to be processed to remove surface impurities.

5. A processing technology for protecting the surface accuracy of a machine according to claim 4, characterized in that: The parameters set for spraying the primer by air spraying include: The air pressure is 0.3-0.6Mpa, the nozzle diameter is Φ1.5-2.0, the spray gun moving speed is 200-300mm / s, and the spray dry film thickness is 45-60μm.

6. A processing technology for protecting the surface accuracy of a machine according to claim 1, characterized in that: In the step 2, the primer is any one of iron red epoxy anti-rust primer, iron red epoxy ester primer, and polyurethane primer.

7. The processing technology for protecting the surface accuracy of the machine according to claim 1 is characterized in that: The topcoat is any one of polyurethane aliphatic topcoat, polyurethane aromatic topcoat and alkyd topcoat.

8. The processing technology for protecting the surface accuracy of the machine according to claim 1 is characterized in that: The step 3 comprises: placing the workpiece to be processed with the primer sprayed on the sprayed surface into a burner preheated to 70-100° C. for drying for 30-40 minutes.

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