Spatial hole system precision machining method based on dynamic reference reconstruction and positioning clamp

Abstract

The invention provides a space hole system precision machining method based on dynamic reference reconstruction and a positioning clamp, and belongs to the technical field of precision machining. Comprising the following steps that a positioning face A and a positioning pin hole of a positioning clamp are machined on a machine tool in real time, and the coaxiality of a positioning mandrel and a main shaft of the machine tool is aligned to be not larger than 0.005 mm before machining; a positioning pin is pressed into the positioning pin hole in an interference fit mode; the to-be-machined part is positioned through the machined positioning face A and the positioning pin, and accurate positioning of the part is achieved by aligning the coaxiality of a part datum hole and a machine tool spindle to be not larger than 0.005 mm; and based on the coordinate position of the positioning pin hole, performing numerical control machining on a spatial hole system on the part. The problems that in space hole system machining, due to clamp positioning errors, machine tool geometric errors and multiple times of clamping, the hole system position degree is out of tolerance, and the clamping efficiency is low are solved; the structure is simple, operation is easy, production cost is low, machining precision is high, quality is stable and reliable, and machining efficiency is high.

Description

Technical Field

[0001] The present invention belongs to the field of precision machining technology, and specifically relates to a spatial hole system precision machining method and a positioning fixture based on dynamic reference reconstruction, which is particularly suitable for multi-plane hole system machining with high positioning requirements. Background Art

[0002] When machining a large number of shaft parts in mechanical manufacturing, positioning elements such as stoppers, bosses, and locating holes are designed to ensure a relatively accurate relative positional relationship between the parts after assembly. When these positioning elements are on the same plane, the holes can be machined in one go using a CNC machine tool according to the set coordinates, using the machine tool's precision to ensure part machining accuracy. However, the hole systems of some parts are not on the same plane, which are called spatial hole systems. The most effective method for machining these parts is to use a horizontal machining center with a rotary table or to design a positioning fixture for machining on a vertical machining center. However, horizontal machining centers are expensive and have high production costs, and the machining quality is greatly affected by the accuracy of the rotary table. Traditional fixture design solutions often have the problem of small positioning clearances after multiple elements are positioned, making part clamping difficult and machining efficiency low. Large positioning clearances will cause large part positioning errors and make it impossible to guarantee the required part positioning accuracy.

[0003] In summary, the processing of spatial hole systems of such shaft parts (such as flange holes at both ends of camshafts and crankshafts) often faces the following problems: 1. The traditional "one side two pins" positioning method is difficult to balance due to the clearance. If the clearance is too small, it will cause difficulty in clamping, and if the clearance is too large, the positioning accuracy will be insufficient. 2. The vertical machining center's worktable and spindle perpendicularity error will be directly transmitted to the parts processing, resulting in out-of-tolerance hole position.

[0004] 3. Although high-precision horizontal machining centers can achieve multi-plane processing, the equipment cost is high, and the accuracy degradation of the rotary table affects long-term stability.

[0005] Therefore, there is an urgent need for a low-cost, high-precision and easy-to-operate spatial hole processing technology. Summary of the Invention

[0006] The technical problem solved by the present invention is to provide a spatial hole system precision processing method and positioning fixture based on dynamic reference reconstruction. The present invention aims to solve the problems of excessive hole system positioning and low clamping efficiency caused by fixture positioning errors, machine tool geometric errors and multiple clamping in spatial hole system processing.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is: The spatial hole system precision machining method based on dynamic datum reconstruction includes the following steps: The positioning surface A and the positioning pin hole of the positioning fixture are processed in real time on the machine tool. Before processing, the coaxiality of the positioning spindle and the machine tool spindle is adjusted to no more than 0.005 mm; Pressing the locating pin into the locating pin hole in an interference fit manner; Position the part to be machined using the machined positioning surface A and the positioning pin, and achieve precise positioning of the part by aligning the coaxiality of the part reference hole and the machine tool spindle to no more than 0.005mm; Based on the coordinate position of the positioning pin hole, a spatial hole system on the part is numerically controlled and processed.

[0008] To further limit the above scheme, the positioning fixture includes a fixture body, a positioning pin and a positioning spindle. A positioning spindle is provided at the upper center of the fixture body for cooperating with the stop of the part. The upper surface of the fixture body reserves a finishing allowance for forming the positioning surface A. The interference fit between the positioning pin and the positioning pin hole is 0.005-0.034mm.

[0009] As a further limitation of the above solution, the radial fit clearance between the positioning spindle and the stop of the part is 0.5 mm, which is used for rapid pre-positioning of the part.

[0010] A further limitation of the above scheme is that the alignment step includes determining the machine tool spindle position based on the center position of the positioning spindle on the positioning fixture determined during clinical processing of the positioning pin hole, rotating the part around the positioning pin on the positioning fixture, and correcting the runout of the alignment part reference hole by a micrometer to no more than 0.005 mm.

[0011] As a further limitation of the above solution, when machining the positioning surface A, its surface roughness is controlled to be Ra≤1.6um to eliminate the non-verticality error of the machine tool worktable.

[0012] A positioning fixture, comprising: The fixture body is provided with a positioning surface A with a reserved finishing allowance; A locating pin is installed in the locating pin hole of the fixture body in an interference fit manner; The positioning spindle is used to cooperate with the stop of the part, and its radial fitting clearance is 0.5mm.

[0013] Furthermore, the outer diameter tolerance of the locating pin is h6, and the tolerance of the locating pin hole is R7, forming a one-way interference fit.

[0014] Furthermore, the positioning surface A and the positioning pin hole are both clinically processed on a machine tool.

[0015] Furthermore, the coaxiality between the positioning spindle and the machine tool spindle is no more than 0.005 mm.

[0016] The advantages of the present invention compared with the prior art are: 1. This solution improves precision: By utilizing the fixture positioning surfaces and positioning pin holes processed clinically, it eliminates the problem of machining errors caused by the non-perpendicularity between the machine tool worktable and the spindle, and the problem of excessive positioning of the positioning pin holes in the machined parts caused by errors in the machine tool system; 2. This solution, by optimizing the positioning fixture structure and the part positioning pin hole processing method, solves the problems of traditional positioning fixtures, such as small clearance between the part and the positioning element of the positioning fixture, difficulty in clamping the part, low processing efficiency, rapid wear of the fixture positioning components, and easy damage to the positioning part during the part clamping process, when multiple factors are involved in positioning and matching. It also solves the problem of large clearance between the part and the positioning element of the positioning fixture, inaccurate part positioning, and poor processing accuracy. 3. This solution optimizes clamping: it adopts the "one-side-one-pin" positioning and radial clearance design, which greatly shortens the clamping time; 4. This solution does not require high-precision horizontal machining and can be achieved with ordinary vertical machining, which reduces costs. By using ordinary quenched and tempered steel and hardened positioning elements, and using common cutting tools, it is possible to achieve precision machining of the spatial hole system of parts. The machined parts have high positional accuracy, stable quality, high machining efficiency, and meet design requirements. 5. This solution has strong versatility: it is suitable for various shaft parts such as diesel engine camshafts, transmission gear shafts, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a front view of the positioning fixture structure in the present invention; Figure 2 A top view of the positioning fixture structure in the present invention; Figure 3 Schematic diagram of the camshaft journal structure of a certain type of diesel engine in an embodiment of the present invention; Figure 4 For the present invention Figure 3 The end face hole system structure diagram shown in the S1 direction; Figure 5 For the present invention Figure 3 The end face hole system structure diagram shown in the S2 direction. DETAILED DESCRIPTION

[0018] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0019] It should be noted that, as used herein, the terms "comprise," "include," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus comprising a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, the phrase "comprising a..." does not preclude the presence of additional identical elements in the process, method, article, or apparatus comprising the elements.

[0020] See also Figure 1-5 , details the embodiments of the present invention.

[0021] Example: This example takes the processing of a certain type of diesel engine camshaft journal structure as an example, and the parts drawing is referred to Figure 3-5 As shown. Figure 3 The figure shows the structure of the camshaft journal of a certain type of diesel engine, showing the processing parts of the end surface hole system at both ends of the camshaft journal; Figure 4 and Figure 5 Schematic diagram of the pin holes at both ends of the camshaft journal in the S1 and S2 directions. The dimensional accuracy of the four locating pin holes on both end faces is Ø12H7. The positional tolerance of the 3-Ø12H7 locating pin holes in the S1 view relative to the Ø12H7 locating pin holes in the S2 view is Ø0.05. Note that before implementing this method, the end faces and the Ø130H6 locating stop should be pre-machined, and the perpendicularity of the centerline connecting the end faces and the Ø130H6 locating stop should be strictly maintained. The two Ø130H6 locating stops should be machined in a single clamping position to ensure their coaxiality is no greater than 0.005.

[0022] This spatial hole system precision machining method based on dynamic datum reconstruction, see Figure 1-2 As shown, the following steps are included: Design of the positioning fixture: The positioning fixture 1 comprises a fixture body 1-2, a positioning pin 1-1, and a positioning spindle 1-3. Positioning spindle 1-3 is located in the center of the upper portion of the fixture body 1-2. The radial clearance between the positioning spindle 1-3 and the part stop (Ø130H6) is 0.5mm, enabling rapid pre-positioning of the part. A finishing allowance is reserved on the upper surface of the fixture body 1-2 for forming the positioning surface A. The interference fit between the positioning pin 1-1 and the fixture's positioning pin hole is 0.005-0.034mm, and a close clearance fit is achieved with the part's positioning hole, with a tolerance of H7 / h6.

[0023] Machining of the positioning fixture: The positioning surface A and the positioning pin hole of the positioning fixture 1 are processed in real time on the machine tool. Before processing, the coaxiality of the positioning spindle 1-3 and the machine tool spindle is not greater than 0.005mm; Pressing the positioning pin 1-1 into the positioning pin hole in an interference fit manner; The parts to be processed are positioned using the machined positioning surface A and the positioning pins, and the precise positioning of the parts is achieved by aligning the coaxiality of the part reference hole and the machine tool spindle to no more than 0.005mm.

[0024] In this embodiment, the parts to be processed are positioned by the clinically processed positioning surfaces and positioning pins, which eliminates the positioning error caused by the non-perpendicularity between the machine tool worktable and the main shaft. At the same time, positioning with a pin hole can make the parts accurate, solving the problems of traditional one-side two-pin positioning, which causes small fitting clearance, difficult clamping of parts, large fitting clearance, and poor part positioning accuracy.

[0025] Processing method for part hole system: Based on the coordinate position of the locating pin hole, the spatial hole system on the part is CNC-machined. When machining the hole on the other end face of the part, first fix the machine tool spindle to the center position of the locating mandrel 1-3 on the locating fixture that was aligned when machining the locating pin hole on the locating fixture. Rotate the part along the center of the locating pin 1-1 to align the center of the Ø130H6 stop of the part, ensuring that the coaxiality between the center of the Ø130H6 of the part and the center of the machine tool spindle is no more than 0.005. Then, set the CNC coordinates of the hole to be machined according to the machining requirements and perform machining. This method can ensure the mutual positional relationship of the hole systems machined at both ends of the part. This method makes good use of the machine tool precision of the CNC equipment and can control the machining accuracy of the part locating hole to within Ø0.03.

[0026] Preferably, when machining the positioning surface A, its surface roughness is controlled to be Ra≤1.6um to eliminate the non-verticality error of the machine tool worktable.

[0027] Preferably, the alignment step uses the center position of the positioning mandrel 1-3 on the positioning fixture 1, determined during clinical machining of the positioning pin hole, to determine the position of the machine tool spindle. The part is rotated around the positioning pin 1-1 on the positioning fixture 1, and the coaxiality between the Ø130H6 part and the machine tool spindle is aligned to no more than 0.005, thereby achieving precise positioning of the part to be machined. If the spatial positioning accuracy of the part is required to be higher, the coaxiality error required for alignment must be smaller.

[0028] In this embodiment, the positioning fixture 1 adopts a one-side-one-pin positioning form, which can solve the problems of traditional one-side two-pin positioning, such as small fitting clearance, difficulty in clamping parts, large fitting clearance and poor part positioning accuracy.

[0029] In this embodiment, the positioning surface and positioning pin hole of the fixture body 1-2 are clinically processed, which can maintain a high degree of consistency with the subsequent processing of the part space hole system, and can better ensure the position requirements of the processed holes.

[0030] In this embodiment, when processing the part hole system, the part is accurately positioned. Then, the machine tool accuracy is utilized to process the part according to the determined hole coordinates in accordance with the processing requirements of the product's spatial hole system. This can greatly improve the position accuracy of the hole and meet the precision processing requirements of the spatial hole system.

[0031] The positioning fixture structure comprises a fixture body 1-2, which is provided with a positioning surface A with a reserved finishing allowance; a positioning pin 1-1, which is installed in the positioning pin hole of the fixture body 1-2 with an interference fit; and a positioning spindle 1-3, which mates with the part stop (φ130H6) with a radial clearance of 0.5mm. The outer diameter tolerance of the positioning pin 1-1 is h6, and the tolerance of the positioning pin hole is R7, forming a one-way interference fit. Both the positioning surface A and the positioning pin hole are machined on a machine tool. The coaxiality of the positioning spindle 1-3 with the machine tool spindle is no greater than 0.005mm.

[0032] The operating principle of this embodiment is as follows: before machining, the fixture body is placed on the workbench of the vertical machining center, and the positioning surface A of the fixture body is first fine-machined and polished to eliminate the part alignment and machining errors caused by the non-perpendicularity of the machine tool workbench and the spindle. Then, the positioning boss Ø129.5h6 on the fixture body is aligned. After the boss center runout is no more than 0.005, the positioning pin mounting hole on the positioning fixture is machined to Ø12R7 according to the coordinate position, and the positioning pin is installed. The outer diameter of the positioning pin is Ø12h6. The part to be machined is clamped and positioned with the Ø12H7 hole in the S2 view of the part that has been machined and the Ø12h6 positioning pin on the fixture. The centers of the Ø130H6 on the part and the Ø129.5h6 boss on the positioning fixture are roughly aligned. At this time, the part only has the Ø12H7 hole The Ø12h6 locating pin on the fixture is used for positioning. The large clearance between the Ø130H6 on the part and the Ø129.5h6 boss on the fixture makes clamping the entire part easy. The machine tool spindle is then moved to the coordinate position of the original Ø129.5h6 boss. A micrometer is mounted on the spindle, and the part is rotated around the center of the fixed Ø12H7 hole until the runout of the Ø130H6 stop on the part is no more than 0.005. The part is then clamped. At this point, the part's positioning is highly consistent with the part position in view S2. The three holes in view S1 are then machined according to the positions shown in view S1. The positioning error is solely due to the Ø12H7 locating pin hole and the machine tool's accuracy. The positioning error of the Ø130H6 stop is replaced by precise alignment, significantly improving the part's positioning accuracy. The dimensional accuracy of the part is fully guaranteed by the use of a high-precision boring tool.

[0033] This invention addresses the problems of excessive hole position tolerance (>0.05mm) and low clamping efficiency during spatial hole machining caused by fixture positioning errors, machine tool geometric errors, and multiple clamping. It features a simple structure, novel design, ease of operation, low production costs, high machining precision, stable and reliable quality, and high machining efficiency.

[0034] This spatial hole precision machining method has been applied in the machining of flange hole systems at both ends of a certain type of diesel engine camshaft journal, and has achieved good results. It is gradually being promoted to the machining of spatial hole systems of other types of diesel engine shaft parts. Practice has proved that this machining technology is efficient, reasonable, has high machining accuracy, a wide range of applications, and has high promotion value.

[0035] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

[0036] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A spatial hole system precision machining method based on dynamic datum reconstruction, characterized by: The following steps are involved: The positioning surface A and the positioning pin hole of the positioning fixture (1) are processed in real time on the machine tool, and the coaxiality of the positioning spindle (1-3) and the main spindle of the machine tool is aligned to be no greater than 0.005 mm before processing; Pressing the positioning pin (1-1) into the positioning pin hole in an interference fit manner; Position the part to be machined using the machined positioning surface A and the positioning pin, and achieve precise positioning of the part by aligning the coaxiality of the part reference hole and the machine tool spindle to no more than 0.005mm; Based on the coordinate position of the positioning pin hole, a spatial hole system on the part is numerically controlled and processed.

2. The spatial hole system precision machining method based on dynamic reference reconstruction according to claim 1 is characterized in that: The positioning fixture (1) comprises a fixture body (1-2), a positioning pin (1-1) and a positioning spindle (1-3); a positioning spindle (1-3) is provided at the center of the upper portion of the fixture body (1-2) for cooperating with a stopper of a part; a finishing allowance for forming a positioning surface A is reserved on the upper surface of the fixture body (1-2); and an interference fit between the positioning pin (1-1) and the positioning pin hole is 0.005-0.034 mm.

3. The spatial hole system precision machining method based on dynamic reference reconstruction according to claim 2 is characterized in that: The radial fit clearance between the positioning spindle (1-3) and the stop of the part is 0.5 mm, which is used for rapid pre-positioning of the part.

4. The spatial hole system precision machining method based on dynamic reference reconstruction according to claim 1 is characterized in that: The alignment step includes determining the position of the machine tool spindle based on the center position of the positioning spindle (1-3) on the positioning fixture (1) determined during clinical machining of the positioning pin hole, rotating the part with the positioning pin (1-1) on the positioning fixture (1) as the center, and correcting the runout of the alignment part reference hole by a micrometer to be no more than 0.005 mm.

5. The spatial hole system precision machining method based on dynamic reference reconstruction according to claim 1 is characterized in that: When machining the positioning surface A, its surface roughness is controlled to be Ra≤1.6um to eliminate the non-verticality error of the machine tool worktable.

6. A positioning fixture for implementing the method according to any one of claims 1 to 5, characterized in that: include: The fixture body (1-2) is provided with a positioning surface A with a reserved finishing allowance; A positioning pin (1-1) is installed in the positioning pin hole of the clamp body (1-2) in an interference fit manner; The positioning spindle (1-3) is used to cooperate with the stop of the part, and its radial fitting clearance is 0.5mm.

7. The positioning fixture according to claim 6, characterized in that: The outer diameter tolerance of the locating pin (1-1) is h6, and the tolerance of the locating pin hole is R7, forming a one-way interference fit.

8. The positioning fixture according to claim 6, characterized in that: The positioning surface A and the positioning pin hole are both clinically processed on a machine tool.

9. The positioning fixture according to claim 6, characterized in that: The coaxiality between the positioning spindle (1-3) and the main spindle of the machine tool is not greater than 0.005 mm.

Images