Shenlong’s differential case and ring gear production line was put into production in 1999. At that time, a series of MA three-part parts were produced. These three products are all products of the PSA Group Citroen. In order to increase the utilization rate of the equipment, the powertrain platform starts the BE steel project. For the differential case ring gear assembly, the BE series has two varieties: BE differential case +81 tooth ring gear and BE difference Speeder housing +74 tooth gear ring, these two kinds of parts are products of PSA Group Peugeot.
Fig.1 Difference in appearance of MA and BE differential case
Although there is a big difference between the BE series products and the MA series products, in order to reduce the investment cost, the overall design plan is to transform the MA differential gear case and the ring gear production line to make the differential case and ring gear production line. Flexibility to achieve the collinear production of multi-components.
Basic principles of transformation
1. Try to unify the machining process of BE and MA differential case and ring gear. For the BE ring gear, a machining center is added in front of the heat to process the mounting holes, and a grinding machine is added to the heat production line to grind the inner hole. For the BE differential case, a machining center is added after the finisher for drilling, tapping and milling.
2. Redesign and manufacture some fixtures to modify the jaws and conveyor raceways of the robot to minimize the change of tooling.
3. Redesign and manufacture some tools to minimize tool change.
4. Reprogram the BE part's machining program.
Figure 2 Process flow of BE differential case of French Peugeot Corporation
The key to transformation
The process design of the BE differential case and ring gear is the key to the entire retrofit project because:
1. The technical requirements of the BE and MA differential housings are quite different. The MA differential case and the ring gear are glued and pressed together, while the BE differential case and ring gear The fitting is made using 8 threaded holes.
2. The axle hole of the BE differential case is used in foreign countries for the machining of the honing machine. The bearing neck and the flange face are machined by grinding machines. We use boring and dry turning.
3. The BE differential housing has 8 threaded holes. The machining of the flange surface is interrupted cutting. Whether the existing equipment can meet the processing quality of the flange surface depends on the rationality of the process arrangement.
Figure 3 Process Flow of BE Differential Vessel with Independent Design
Technical content of the renovation project
1. Feasibility analysis of self-designed BE differential case process scheme
(1) The difference between the MA differential case and the BE differential case (see Figure 1). From Table 1, it can be seen that there is a big difference in the shape of the MA and BE differential housings, and the roughness of the semi-shaft holes and the bearing neck of the BE differential housing is more stringent than that of the MA.
(2) Comparing the process of designing the BE differential housing and the mature process of Peugeot. Figure 2 shows the process flow of the BE differential case of the French Peugeot Corporation, and Figure 3 shows the process flow of the BE differential case designed by us.
The biggest difference between the foreign process plan and our own designed process plan is reflected in four parts: the machining of the axle hole, bearing diameter at both ends, and flange surface. In France, honing is used for the machining of semi-axial boreholes, while grinding is used for the machining of both bearing necks and flange surfaces.
Fig. 4 Differences in the shape of the MA ring gear and BE ring gear
1 Axial hole machining. The requirement for the BE differential housing half-shaft product is φ260+0.033, and the surface roughness requirement is R5, which is equivalent to Ra1.6. The requirements of the MA differential housing half shaft hole product are φ250+0.033, the surface roughness is R6.3, which is equivalent to Ra2. The tolerance of the hole diameter is basically the same, but in terms of surface roughness, the BE differential case The requirements were more stringent. We analyzed the cutting parameters of the MA axle hole, n = 1500r/min, ap = 0.5mm, f = 0.25 mm/r. Change the cutting parameters to keep n and ap constant and decrease f. We tested different cutting parameters. When the feed amount of MA was finally reduced from 0.25 mm to 0.18 mm, the surface roughness of the tool was R4.5 when it was machined to its end of life, which satisfies the requirement of roughness.
Figure 5 Self-designed BE ring gear process
2 Bearing neck machining. The bearing neck diameter MA and BE differential housing are the same product requirements, are φ38 +0.027, but the surface roughness requirements BE is R5, MA is R6.3, according to the machining test of the axle hole, bearing The requirements of the neck are attainable.
Table 1 Differences in main technical requirements of MA and BE differential case
3 flange surface processing. There are two characteristics of the BE differential housing flange surface with 8 threaded holes. One is interrupted cutting, and the other is that the processing length is up to 20mm. The existing equipment is a horizontal CNC lathe, and dry cutting, so we designed two sets of process solutions: the first set of drilling and tapping in front of the finishing car according to the conventional process; the second set of process plan is in the finishing car. After drilling and tapping.
Fig. 6 Fixture design of MA and BE differential case in OP40
During the implementation of the process plan, we found that the existing finisher equipment could not meet the quality requirements of the flange surface of the BE differential case, so we adopted the second set of process plan to move the drilling, tapping and milling slots to the After the finishing vehicle OP105 processing. After the step drilling, we found that there was a burr at the entrance of the hole. By adding a time-delay program to the hole in the NC program, the burr on the flange surface was gone.
Through analysis and experiments, it is proved that the process of our own designed BE differential case is feasible.
2. Feasibility analysis of self-designed BE ring gears
The difference between the shape of the MA ring gear and that of the BE ring gear is shown in Fig. 4. The differences in the main technical requirements are shown in Table 2. As can be seen from Table 2, the technical parameters of the MA and BE ring gears are quite different, especially the maximum effective tip circle diameter. The BE is 29.7mm larger than the MA, and the diameter is larger than 180mm. The mandrel positioning width is BE and MA. The ring gear is narrower than the 15.4mm, so the BE ring gear is less technical than the MA ring gear.
Figure 7 Fixture Design for OP70 Differential Housing
Our self-designed BE ring gear process is shown in Figure 5. The biggest difference between the foreign process scheme and our own designed process scheme is: drilling + two-sided chamfering, France arranged at the OP30, before hobbing, and our solution is arranged at the OP70 after shaving. Since we are producing BE ring gears by retrofitting the old line, there is no space for equipment between the lathes and the hobbing gear, which can only be placed after shaving. Tests have proved that: Under the premise of convenient on-site logistics, we can completely guarantee the quality requirements of our products. This is completely feasible.
3. Retrofit of differential housing production line and ring gear production line
(1) Process design: 1 The self-designed BE differential case and BE ring gear are used in Figs. 3 and 5.
2 NC machining program preparation and debugging: NC program is compiled for parts of BE differential gear case and two BE ring gears. The involved systems include FANUC, NUM and Siemens; 12 CNC machine tools are involved. , from Japan, France and Germany, respectively.
(2) Fixture design
1 OP40, by designing the V-blocks 1, 2, and 8 and the V-type pressure block 5 shared by the MA and BE differential case as shown in Fig. 6, the jig accuracy is not adjusted. Only by replacing the axial positioning block 3, the contour support 4 and the pressure plate 6, the positioning and clamping of the MA and BE differential housings with great differences in axial dimensions, height dimensions and contours are fulfilled.
Figure 8 013 station, roughing sphere
2 OP70 is the key process of differential case processing. The design of the fixture adopts a highly centralized distribution scheme so as to leave enough space for the fixture to be arranged in 6 directions. The device is used by German ROHM company. Design fixtures. The original design was only applicable to the MA case of the Sφ77. However, the BE differential case of the Sφ84 was 12mm thicker than the case and could not be used. Due to the limitation of the function of the domestic coordinate grinding machine, it was not possible to manufacture the jig in China. We used the three-dimensional simulation to redesign the fixtures of the OP70 to carry out the renovation on the basis of the ROHM fixtures in Germany. We reduced the thickness of the fixture mounting plate 1 as shown in Fig. 7 by 12mm and extended the guide bar 2 of the fixture by 12mm. The guide rod 2, the clamping jaw 3, the slider 4, the positioning block 5 and the clamping block 6.
(3) Tool Design
1 OP40 tool design: OP40 is a three-station CNC machine tool, respectively 011/012/013 workstation. The 013 station is a spherical machining station. The structure of the tool is a crank connecting rod mechanism. When the rotation point on the arbor drops to the position of the center of the sphere, the tool crank motor is used to drive the crank linkage mechanism to complete the spherical surface. Roughing (Figure 8). We have redesigned the shared body as shown in Fig. 9 to simplify the change of shape. Only different tool holders can be replaced in different varieties.
Figure 9 Redesigned common body
2 OP70 tool design: under the premise of ensuring that the working stroke of the Z axis is not changed, the angle of the driving wedge is increased from the original 18° to 21°43′, making the radial stroke during operation increase from 15.5mm. At 19 mm, the remaining 3.5 mm is compensated by the BE boring head, which means that the BE head is 1.75 mm larger than the radial dimension of the head of the MA, achieving the common tool production of the MA and BE differential housings (as shown 10).
Figure 10: MA and BE differential housings for common-body production
(4) automated design
1 FANUC system: The FANUC0i system uses direct selection of machining programs to implement the selection of control programs for different types of parts. The FANUC18i system uses rotary switches to select the machining program to implement control program selection for different types of parts.
2 Siemens 840D system: The Siemens 840D system adopts the method of directly selecting the machining program and uses the rotary switch to realize the selection of the control program of different types of parts.
3 NUM1060 System: OP40/70
Using the MA or BE button to notify the PLC of the selected type.
The OP80 uses the E parameter of the exchange area to inform the NC to perform a corresponding jump when executing the program.
Technological innovation
In terms of the process, we first formulated the principle of the combination of two series of products passed on the same production line, so that the processing method is as consistent as possible, proposed and realized the boring instead of grinding, precision grinding car instead of grinding, reasonable adjustment of the processing Process sequence.
Table 2 Differences in the main technical requirements of MA ring gear and BE ring gear
In terms of fixtures, we have redesigned and modified more than ten existing fixtures to meet the needs of different product parts positioning and clamping functions.
On the tool side, we redesigned and modified the wedge mechanism, body, and tool head of the spherical boring tool balancer. Through experiment optimization, high-efficiency and high-precision cutting tools have been selected that are based on grinding and grinding.
In terms of electrical control systems, the secondary development of the NUM1060 CNC tool management program has expanded the tool set and automatic tool setting and automatic compensation functions.
At the same time, we also canceled the car with the differential case and ring gear and modified the MECALIX measurement system.
During the entire renovation process, the main technical innovations we conducted are as follows:
1. Independently designed the process scheme of the BE differential case and the BE ring gear, and no mature foreign technology was used. Utilizing the principle of process consolidation, using existing MA equipment, through a series of design and transformation of fixtures, tools, and control systems, the technology was reasonably arranged to meet the requirements of BE products, and it was realized that only one series product could be transformed from the original. It can be passed through two series and five varieties of flexible production lines.
2. In the aspect of technology, the French matured honing process for semi-shaft holes and grinding outer diameter of the bearing was changed. Through reasonable allocation of extra allowances, and selection of suitable high-efficiency tools and matching machining parameters, bore drilling instead of honing, Replace the grinding process with a precision car.
3. Second development of the NUM1060 CNC system has expanded the tool set, automatic tool setting and automatic compensation functions. The number of tool sets has been expanded from 4 to 5, which allows the tool to achieve tool life management, automatic tool setting and automatic compensation for 5 tool sets.
4. Redesign the fixture of OP70 by 3D simulation and reform it on the basis of ROHM fixture in Germany, which overcomes the problem that the domestic coordinate grinder cannot process holes of 200mm in length and diameters larger than φ50, and realizes the use of a set of fixtures to machine the diameter of the inner spherical surface. There are two series of differential housings that differ by 7mm and vary widely in shape.
Conclusion
The overall technical transformation plan of the project is rationally designed and has complete functions. After the implementation of the project, it is reliable in operation and has achieved flexible production. It has achieved remarkable economic and social benefits and its technology is at the leading level in the domestic industry. Not only that, 90% of the fixture design, the automation of all equipment, the preparation of processing programs, the transformation of the active measurement, and the commissioning of the equipment are all independently completed by us. This paradigm of relying on its own power to transform foreign devices is worth promoting.
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