Method for machining small-micropore-diameter high-precision inner hole with coating

Abstract

The invention relates to the field of hole machining, in particular to a machining method for a small-micropore-diameter high-precision inner hole with a coating. The standard inner diameter of an inner hole with a coating is set as m, the thinnest thickness of the coating is set as n, the inner diameter range value of the inner hole during machining is calculated according to the thinnest thickness of the coating, the minimum diameter of the inner hole is m + 2n, and the maximum diameter of the inner hole is m + 2n + the maximum tolerance value of the inner hole; surface treatment: carrying out phosphate oxidation and hydrophobic treatment on the inner hole formed by machining, and finally coating the wall of the inner hole with a coating; an extrusion bar is prepared, an extrusion part is coaxially arranged on the extrusion bar, the diameter of the extrusion part is m, the part subjected to surface treatment is horizontally placed, the extrusion bar is aligned with the inner hole of the part to rotate downwards and extrude the inner hole, the extrusion part completely passes through the inner hole, and the extrusion part and the inner hole are kept coaxial during extrusion. By means of the scheme, the problem that the size of the inner hole with the coating and the small hole diameter is not prone to being qualified is solved.

Description

Technical Field

[0001] The invention relates to the field of hole processing, and in particular to a method for processing an inner hole with a small micro-aperture and high precision with a coating. Background Art

[0002] A coated small micro-aperture inner hole means that a layer of coating of a certain thickness is coated on the inner hole wall with an aperture of less than 3mm. The thickness of the coating is usually between several microns. In order to ensure that the inner hole size is qualified after the surface treatment coating, the inner hole size needs to be increased during machining to leave space for the surface treatment coating. Since the coating is too thin, it is impossible to ensure that the thickness value is completely consistent when coating the same inner hole wall. Therefore, the coating thickness on the same inner hole wall meets the requirements within 5μm-10μm. At the same time, since the tolerance range of the standard inner diameter of the coated inner hole is 0-14μm, there are many factors that affect the reserved space for the inner hole. At the same time, the reserved space is too small. Any deviation in any factor will lead to unqualified inner hole size problems, and the processing difficulty is relatively large. At present, no reference processing solution for the inner hole with this feature has been found in the existing technology. Summary of the invention

[0003] The present invention is intended to provide a high-precision inner hole machining method for small-micro-aperture coated materials, so as to solve the problem that the inner hole size of small-micro-aperture coated materials is not easy to meet the standards.

[0004] To achieve the above object, the present invention adopts the following technical solution: a method for machining a high-precision inner hole with a small micro-aperture with a coating, comprising the following steps:

[0005] Machining: Assume that the standard inner diameter of the inner hole with coating is m, and the thinnest coating thickness is n. The inner diameter range value during inner hole machining is calculated according to the thinnest coating thickness. The minimum diameter of the inner hole is m+2n, and the maximum diameter is m+2n+the maximum tolerance value of the inner hole.

[0006] Surface treatment: the inner hole formed by machining is subjected to phosphate oxidation and hydrophobic treatment, and finally a coating is applied on the inner hole wall;

[0007] Extrusion processing: prepare an extrusion rod with an extrusion part coaxially arranged on the extrusion rod. The diameter of the extrusion part is m. Place the surface-treated part horizontally, align the extrusion rod with the inner hole of the part, rotate it downward and extrude it, and make the extrusion part completely pass through the inner hole. During extrusion, the extrusion part remains coaxial with the inner hole.

[0008] Preferably, as an improvement, the outer peripheral wall of the extrusion portion is in an arc-shaped structure that is larger in the middle and smaller at both ends.

[0009] Preferably, as an improvement, a guide portion is provided on the extrusion rod, the guide portion is fixedly connected below the extrusion portion, and the inner diameter of the upper surface of the guide portion is the same as the inner diameter of the lower surface of the extrusion portion.

[0010] Preferably, as an improvement, in the extrusion processing step, when the extrusion rod extrude the part, the part will not rotate but can be displaced in the horizontal direction.

[0011] Preferably, as an improvement, in the extrusion processing step, the part is placed directly below the extrusion rod, at which time the part is in a free state, and the guide portion of the extrusion rod is driven to enter the inner hole of the part. When the part with the largest diameter of the extrusion portion enters the upper end of the inner hole, the movement of the extrusion rod is stopped and the part is clamped by a clamping tool, and then the extrusion rod is started to continue to rotate downward.

[0012] Preferably, as an improvement, when the guide portion enters the inner hole of the part until the portion with the maximum diameter of the extrusion portion enters the upper end of the inner hole, the advancement speed of the extrusion portion is less than 0.2 mm / s.

[0013] Preferably, as an improvement, the rotation speed of the extrusion part when performing rotational extrusion on the inner hole of the part is 1200r / min-1400r / min, and the downward speed is 0.02mm / r-0.05mm / r.

[0014] The principles and advantages of this solution are as follows:

[0015] Since the tolerance range of the standard inner diameter of the inner hole is 0-14μm, and there is also a thickness allowable range of 5μm-10μm during the later coating, there are many influencing parameters, the processing difficulty is greater, and the qualified rate of the processed inner hole size is low. Later, the applicant considered ensuring the qualified rate of the inner hole by improving the machining accuracy, so the size of the inner hole before surface treatment was calculated based on the tolerance range of the inner hole. That is, when the tolerance value is 0, it is necessary to consider the reserved space when the thickest coating is 10μm, that is, the inner hole diameter is 2.5mm+20μm; when the tolerance value is 14, it is necessary to consider the reserved space when the thinnest coating is 5μm, that is, the inner hole diameter is 2.5mm+24μm; at this time, the processing tolerance before the inner hole surface treatment is 4 microns, which is too small. The equipment cannot meet such high precision requirements and cannot be processed.

[0016] Later, the applicant tried to calculate the size of the inner hole before surface treatment based on the coating thickness, that is, to recalculate the size of the hole before surface treatment in the form of average coating thickness, that is, the average coating thickness is 7.5 microns, and the coating thickness of the inner hole is calculated based on the average thickness of 7.5 microns. The tolerance range of the inner diameter allowed is 0-14μm, and after calculation, the minimum diameter of the inner hole is 2.5mm+15μm, and the maximum diameter is 2.5mm+29μm. In this way, the processing tolerance of the inner hole before surface treatment is 14 microns, which meets the equipment processing requirements. However, after the holes processed by this method are surface treated, some products have out-of-tolerance phenomenon, and the upper and lower limit deviations of the inner hole are both 5 microns beyond the qualified tolerance range, and the qualified rate is less than 70%.

[0017] After many analyses, the applicant calculated the size of the inner hole before surface treatment according to the thinnest coating thickness n. The minimum diameter of the inner hole is m+2n, the maximum diameter is m+2n+the maximum tolerance value of the inner hole, and the thinnest thickness coating is 5 microns, that is, the minimum diameter of the inner hole is 2.5mm+10μm, and the maximum diameter is 2.5mm+24μm. In this way, the processing tolerance before the surface treatment of the inner hole is still maintained at 14 microns, which reduces the difficulty of equipment processing. At the same time, after surface treatment, the actual size of the hole is 2.5mm-10μm, and the maximum diameter is 2.5mm+14μm. It can be seen that the actual inner diameter of the coated inner hole is smaller than the required size. At this time, in conjunction with the extrusion processing step, the coating of the inner hole that is too small with the coating is squeezed or brought out through the extrusion rod, so that the inner hole accurately reaches the standard size. After testing and statistics, no problem of unqualified inner hole size has been found.

[0018] In summary, the inner hole size of the coated micro-aperture processed by the present method has a pass rate of up to 100%, and the processing method is simple and the processing cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the extrusion process steps of the present invention. DETAILED DESCRIPTION

[0020] The following is further described in detail through specific implementation methods:

[0021] The reference numerals in the drawings of the specification include: part 1, inner hole 2, extrusion rod 3, extrusion portion 4, guide portion 5.

[0022] A method for machining a coated small-diameter high-precision inner hole comprises the following steps:

[0023] Machining: Assume that the standard inner diameter of the inner hole 2 with coating is m. In this embodiment, the standard inner diameter of the inner hole 2 after coating is 2.5mm as an example. The tolerance range of the standard inner diameter of the inner hole is 0-14μm, and the thickness range of the coating is 5μm-10μm. In order to ensure that the size of the hole Φ2.5 is qualified after surface treatment, the size of the inner hole needs to be increased during machining to leave space for the surface treatment coating. According to the thinnest thickness n of the coating, the size of the inner hole before surface treatment is calculated. The minimum diameter of the inner hole 2 is m+2n, the maximum diameter is m+2n+the maximum tolerance value of the inner hole, and the thinnest thickness coating is 5 microns, that is, the minimum diameter of the inner hole is 2.5mm+10μm, and the maximum diameter is 2.5mm+24μm. In this way, the machining tolerance of the inner hole 2 before surface treatment is still maintained at 14 microns, which reduces the difficulty of equipment processing.

[0024] Surface treatment: The inner hole 2 formed by machining is subjected to phosphate oxidation and hydrophobic treatment, and finally a 5μm-10μm coating is applied to the inner hole wall. At this time, the actual size of the hole is 2.5mm-10μm, and the maximum diameter is 2.5mm+14μm. It can be seen that the actual inner diameter of the inner hole 2 with coating is smaller than the required size. Therefore, if a qualified standard inner hole is to be achieved, the next step of extrusion processing is required.

[0025] Extrusion processing: such as Figure 1As shown, an extrusion rod 3 is prepared, and an extrusion portion 4 is coaxially formed at the bottom of the extrusion rod 3. The outer peripheral wall of the extrusion portion 4 is an arc structure with a large middle and small ends. The maximum diameter of the extrusion portion 4 is consistent with the diameter of the standard inner hole 2 with a coating of 2.5 mm, and the surface roughness of the extrusion portion 4 is less than 0.8, so as to ensure that the coating surface is smooth after extrusion molding. A guide portion 5 is also provided on the extrusion rod 2, and the guide portion 5 is fixedly connected to the lower surface of the extrusion portion 4, and the inner diameter of the upper surface of the guide portion 5 is the same as the inner diameter of the lower surface of the extrusion portion 4. During the extrusion process, the extrusion rod 3 is first vertically mounted on the machine tool, and then the surface-treated part 1 is placed directly below the extrusion rod 3, and the part 1 is in a free state at this time. The guide portion 5 of the extrusion rod 3 is driven to slowly enter the inner hole 2 of the part 1. When the part with the maximum diameter of the extrusion portion 4 slowly enters the upper end of the inner hole 2, the extrusion rod 3 is stopped from moving and the part 1 is kept in place, and then the part is fixed by a clamping tool to prevent it from rotating with the extrusion rod, wherein the clamping tool can be a flat-nose pliers or the like. Then start the extrusion rod to continue rotating and extruding downward. In this solution, the coating surface can be made smoother by rotating and extruding downward. The rotation speed during rotation and extrusion is 1300r / min, and the downward speed is 0.04mm / r. Since the coating is thin, under the above extrusion parameters, the excess coating can be slowly squeezed and compacted or brought out, while also further ensuring that the coating surface is smoother. In the process of rotating downward, the coating on the surface of the inner hole 2 is squeezed or brought out of the inner hole, so that the inner hole 2 with an inner diameter that is too small after coating in the previous step is extruded into a standard diameter inner hole. According to test statistics, no problem of unqualified inner hole size has been found so far.

[0026] During the extrusion process, the most core and difficult step is the problem of aligning the axis of the extruded rod 3 and the inner hole 2. If there is a very small deviation between the two, although the size of the inner hole is qualified, the coating thickness on one side of the inner hole 2 will be thicker, and the other side will be thinner or even without coating. Therefore, in order to solve this problem, the applicant considered using induction alignment equipment, but the cost was too high. It was also considered to install infrared rays on the central axis of the extruded rod, and then designed a device for positioning the part 1, so that after the part is installed, the infrared ray is positioned to the center of the part. However, it was found in practice that the accuracy could not be guaranteed because the coating was too thin. If either the extruded rod 3 or the part 1 had a deviation of 1 micron or less, the product would be unqualified.

[0027] Later, the applicant adopted this method and improved the design of the extrusion rod. The extrusion part was designed as an arc-shaped structure with a large middle and small ends, and a guide part was installed at the lower end of the extrusion part. In this way, during the extrusion process, the part is placed directly below the extrusion rod. At this time, the part is in a free state and cannot be fixed by any device. The guide part of the extrusion rod is driven to slowly enter the inner hole of the part at a speed less than 0.2mm / s until the part with the largest diameter of the extrusion part slowly enters the upper end of the inner hole. In this process, since the part is in a free state, if the two are not coaxial, the extrusion part has an arc-shaped outer contour with a large middle and small ends. When it contacts the inner wall of the part, it will drive the part to automatically adjust its horizontal position until the part with the largest diameter of the extrusion part enters the inner hole, and the two are automatically in a coaxial state. In this way, without the use of additional auxiliary devices for coordination and measurement, high-precision coaxial alignment can be achieved, thereby ensuring the processing accuracy of the inner hole of the part.

[0028] Among them, when the guide part enters the inner hole of the part and when the part with the largest diameter of the extrusion part enters the upper end of the inner hole, the advancement speed of the extrusion part is less than 0.2mm / s. This advancement speed has been determined after many tests. Within this advancement speed, the two can be better aligned to achieve the best coaxial effect, so that the coating of the inner hole is more uniform.

[0029] The above is only an embodiment of the present invention, and the common knowledge such as the known specific technical solutions and / or characteristics in the solution is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several modifications and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A method for machining inner holes with small micro-aperture and high precision with coating, characterized in that: The following steps are involved: Machining: Assume that the standard inner diameter of the inner hole with coating is m, and the thinnest coating thickness is n. The inner diameter range value during inner hole machining is calculated according to the thinnest coating thickness. The minimum diameter of the inner hole is m+2n, and the maximum diameter is m+2n+the maximum tolerance value of the inner hole. Surface treatment: the inner hole formed by machining is subjected to phosphate oxidation and hydrophobic treatment, and finally a coating is applied on the inner hole wall; Extrusion processing: prepare an extrusion rod with an extrusion part coaxially arranged on the extrusion rod. The diameter of the extrusion part is m. Place the surface-treated part horizontally, align the extrusion rod with the inner hole of the part, rotate it downward and extrude it, and make the extrusion part completely pass through the inner hole. During extrusion, the extrusion part remains coaxial with the inner hole.

2. A method for machining a coated small-diameter high-precision inner hole according to claim 1, characterized in that: The outer peripheral wall of the extrusion portion is in an arc-shaped structure that is larger in the middle and smaller at both ends.

3. A method for machining a coated small-diameter high-precision inner hole according to claim 2, characterized in that: A guide portion is provided on the extrusion rod, the guide portion is fixedly connected below the extrusion portion, and the inner diameter of the upper surface of the guide portion is the same as the inner diameter of the lower surface of the extrusion portion.

4. A method for machining a coated small-diameter high-precision inner hole according to claim 3, characterized in that: During the extrusion process, the extrusion rod squeezes the part so that the part does not rotate but can be displaced in the horizontal direction.

5. A method for machining a coated small-diameter high-precision inner hole according to claim 4, characterized in that: During the extrusion process, the part is placed directly below the extrusion rod. At this time, the part is in a free state, and the guide part of the extrusion rod is driven into the inner hole of the part. When the part with the largest diameter of the extrusion part enters the upper end of the inner hole, the movement of the extrusion rod is stopped and the part is clamped by the clamping tooling, and then the extrusion rod is started to continue to rotate downward.

6. A method for machining a coated small-diameter high-precision inner hole according to claim 5, characterized in that: When the guide portion enters the inner hole of the part until the portion with the largest diameter of the extrusion portion enters the upper end of the inner hole, the advancement speed of the extrusion portion is less than 0.2 mm / s.

7. A method for machining a coated small-diameter high-precision inner hole according to claim 6, characterized in that: The rotation speed of the extrusion part when performing rotational extrusion on the inner hole of the part is 1200r / min-1400r / min, and the downward speed is 0.02mm / r-0.05mm / r.

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