The engine block is the power of the car. The casting quality of the cylinder directly affects the performance of the car, and all foundries attach great importance to it. This project is the development of a powerful grinding grinder for the engine block, which is used to complete the powerful grinding of the four end faces of the cylinder block.
After the foundry casts the engine block of the automobile, there is a large flash burr on the outer surface of the cylinder. Therefore, each cast cylinder must be cleaned before being used as a qualified casting product, and then enter the processing line. Processing. At present, among many domestic automobile engine manufacturers, large-scale foundry manufacturers still use outsourced equipment to complete the surface cleaning process after the cylinder is cast. The cost of foreign equipment is high, and it is not convenient for maintenance. Some small manufacturers use themselves. The simple cleaning equipment designed and manufactured to complete the cleaning of the cylinder surface, even some manufacturers still adopt manual grinding method, labor intensity, low productivity, poor working environment and unstable production quality.
The requirement for powerful grinding, the maximum grinding depth bed, allows the cylinder to be machined on one machine and completes the four-face machining process in one setup. The grinding head adopts the cylinder center as the center and the left and right opposite type; 3. In addition to the rotation, the grinding wheel also has the function of axial expansion and overload protection, and the moving distance is less than 25mm; the angle is used to design the machine tool.
4. Main parameters and structural scheme of the grinding machine According to the above requirements, a US-made cleaning equipment used at the production site was surveyed and analyzed, and its advantages in principle and structure were absorbed. The localization design was carried out to establish the design scheme of the grinding machine. Divide the design work into the following large assembly parts: the power head spindle structure should meet the requirements of high-efficiency grinding; the power head spindle has good sealing performance, low temperature rise and long bearing life; the grinding wheel must have extension in addition to rotation. The shrinking function has a moving distance of less than 25mm; the grinding head has a grinding wheel retracting device when the grinding is overloaded; the main shaft bearing is lubricated with the external thin oil; the belt drive adopts a circular arc synchronous toothed belt; the whole machine tool adopts a steel plate welding combined type.
The cylinder cleaning and grinding machine is a flat surface grinding and cleaning machine that integrates machine, electricity, liquid and gas technology according to the principle of strong grinding.
In order to meet the rigidity and high precision of the machine tool, the grinding head is mounted on the base of the grinding head and the sliding seat, with the cylinder center as the center, and two left and right opposite combinations are connected on one transmission base; the jig trolley and the trolley conveying device are also installed. On the same drive base; the gripper carriage is horizontally dragged on the base. A hydraulic cylinder of the crucible 180 for moving the grinding head rapidly reversing is mounted on the base of the grinding head, and the moving speed of the grinding head can be adjusted by adjusting the size of the corresponding hydraulic throttle valve. Can be stepless speed regulation. There is a manual adjustment device-screw on the grinding head slide, which is compensated when the wear of the grinding wheel affects the machining size. The grinding head slide is mounted on the double-circle guide rod to ensure smooth and light pushing when the grinding head moves; the grinding wheel rotates at a speed of 725r/min.
The cylinder is placed on the fixture on the feeding trolley, and the feeding trolley passes between the two large-diameter grinding wheels along the guide rail on the transmission base to complete the grinding process on both sides of one dimension line segment of the cylinder. When the end of the guide rail is operated by the machining cylinder for 90-position operation, the positioning pin is withdrawn, the pressure head is relaxed, and the oil pump supplies oil to the table-displacement rack cylinder. When the rack cylinder moves, the cylinder and the table are engaged by the cylinder. A pair of gears drive the worktable to perform the 90-position movement. After each indexing operation is completed, the rack cylinder is immediately in a relaxed state, so that the pin cylinder is accurately pinned and the head is pressed. After the cylinder body 90Â°| position, when the cylinder block and the clamp carriage return along the traveling rail, the grinding head is automatically shifted to the size by the automatic control device of the electric appliance, and the trolley after the indexing enters between the grinding wheels to complete another cylinder. The grinding process is performed on the two sides of the size line segment, and the feeding carriage completes one working cycle to complete the grinding and cleaning of the four faces of the cylinder blank.
The machine is equipped with two different protective devices, which are divided into two parts: the grinding wheel cover and the dust cover. The grinding wheel cover protects the grinding wheel from damage during the grinding process. The form of the cover is basically taken in most forms. A grinding wheel accident occurs and no splash injury will occur. The role of the dust hood is to prevent dust from flying during the grinding process. It is used in the grinding station to concentrate the dust generated during the grinding process in the hood and is immediately extracted by the dust extraction device. The cover is in the form of two mills across the left and right. Outside the head grinding wheel, it also meets other requirements such as the trolley and the inlet and outlet of the machined cylinder.
A vibrating flute is arranged on each side of the drive base. During the grinding process, the grinding debris falling into the drive base passes through the guide slide and then falls into the vibrating flute, and the vibrating flute moves the wear debris in the form of a parabola. Automatically discharge into the pit to collect the slag bucket.
In order to realize the semi-automatic work of the machine tool, the electric machine adopts the PLC program control, the movement of the grinding head frame and the movement of the jig trolley adopts the non-contact switch monitoring, and the other action actuators all adopt the self-contained magnetic switch.
V. Difficulties and solutions in the development work The various actions of the machine tool are controlled by the PLC program, thus realizing the automatic and semi-automatic production of the cylinder cleaning grinding machine. Since the grinding method is plane grinding, a large area is required to remove burrs and flash edges, so efficient grinding is employed. In addition, considering that the cylinder is a casting, the burr and the flash are different in depth. The power head is one of the important parts of the engine grinding machine. Therefore, in the design of the grinding head, the grinding wheel must be retracted when the grinding wheel is overloaded. In the absence of the principle, a simple and feasible solution is proposed, and the pneumatic anti-overloading retreat system is introduced from the current work to study the pneumatic components introduced in the domestic market, and the cylinder is used to realize the extension and contraction functions with a distance of 25 mm. Due to the strong grinding, the motor power should be properly selected, the selected motor is Y280S, N=75KW, n=1440r/min. In order to maintain accurate transmission ratio, the arc toothed timing belt is a key point in this subject. . There is no uniform standard for arc toothed timing belts. Therefore, the choice of belt type and belt length is based on the manufacturer's product sample. It is a burr surface with a large processing area, a large knife and a large grinding force. 400. The arrangement of the parts on the shaft makes the shaft force reasonable.
The positioning of the parts on the shaft is reliable, and the assembly and disassembly is convenient.
Has a good structural process performance, easy to manufacture and ensure accuracy.
For shafts that require high rigidity, structural deformation should also be considered to reduce the deformation of the shaft.
Considering the processing of the casting burrs, the grinding head is subjected to a large variable load. Moreover, the shaft has the functions of rotation and axial feed. The selected bearing must be able to withstand both radial and axial forces, and the main shaft is mounted inside the headstock, and also takes into account the movement of the spindle after heat generation. . The headstock is sealed so that it is dust-proof, so the spindle cannot be extended and retracted at will. Thus, tapered roller bearings can be used. The bearing capacity is strong, it can resist the radial load and the axial load; and the inner and outer rings of the tapered roller bearing can be separated, which is convenient for adjusting the clearance of the main shaft after being heated.
-2-79, the selection of tapered roller bearing model GB/T297-1994 is 32228. The motor power is transmitted to the grinding wheel spindle through the arc toothed timing belt, and the spindle rotates at high speed. At the same time, the two pneumatic cylinders on the outer side of the sliding sleeve of the main shaft drive the sliding sleeve of the main shaft, and the main shaft and the seat drive the main shaft to expand and contract in the axial direction, and are in the floating state, thereby realizing the feeding of the grinding wheel and the high-speed rotary grinding. The spindle housing is welded, with simple structure, good rigidity, good sealing performance and light weight. When the grinding wheel is worn out, the size of the machined cylinder is not in place. The grinding wheel fine adjustment feed device can be manually adjusted for compensation, and the machine seat and the bed are both manufactured by steel plate welding.
In addition to the mechanical techniques described above, the cylinder cleaning machine also uses hydraulic, pneumatic and lubrication technologies. The hydraulic principle is as follows. 1: 1 hydraulic principle hydraulic design main parameters: sechin; oil pump oil supply: 88 l / min; oil pump oil pressure: 14 MPa; oil return filtration accuracy: 20 ç¼ª; pressure valve in the system safe Protective effects.
The hydraulic system of the machine tool controls the two grinding head frames for quick reversing movement, and the work table performs 90. The movement of the grinding head frame for quick reversing movement is the selection of standard hydraulic cylinder products, and the worktable performs 90-position movement. The piece is a rack cylinder made of non-standard design.
The two grinding head wheels are axially telescoped, the clamp trolley table and the clamping arm, and the working table is powered by pneumatic control. The pneumatic principle is as follows.
2 shows: 2Pneumatic schematic diagram Before entering the grinding station, the two grinding wheels are quickly popped up to the grinding position and maintain a certain grinding support force. When the machined cylinder is ground in place, the two grinding wheels are quickly returned, popped or returned. The stroke is 15 mm and is called the grinding wheel floating stroke. When the grinding wheel is over-grinded, the grinding support force reaches the limit value. At this time, the rear cavity of the grinding wheel cylinder is quickly decompressed, and the grinding wheel quickly exits the floating stroke to protect the safety of the grinding wheel and prevent the overload grinding force from adjusting the pressure switch. Come to fix.
Pneumatic control of the jig trolley is used to press the ram at the pressure of the ram, the indexing of the clamp arm, the positioning pin of the worktable, and the trolley to sweep the slag when walking.
Before the worktable is indexed, the workbench must be lifted up by the jacking cylinder together with the cylinder to be machined, leaving the car plate for a certain distance. After the workbench is turned into position, the jacking cylinder can be retracted and the workbench can be repositioned.
Air supply flow rate: 850 liters / minute; gas supply pressure: greater than 5 MPa; taking into account the instantaneous supply pressure drop during operation, the pneumatic pump is installed in the grinding and grinding wheel cylinders to ensure the working pressure of the grinding head cylinder Between 0.7 and 1 MPa; lubrication requirements are mainly at the front and rear end bearings of the grinding head spindle, and are lubricated with thin oil. The lubrication method is timed quantitative automatic oil supply. The oil supply and oil supply intermittent time can be based on actual working conditions and requirements. Manual adjustment can be completed. In addition, lubrication of other parts such as the sliding sleeve of the main shaft and the sliding sleeve of the chip removal device are all dry oil lubrication. The lubrication principle is as follows: oil supply: 6 ml / hour; use Lubricant grade N32; tank volume: 3 liters; in the automatic state, the original conditions are met (the grinding head surface state, the motor has started, the conveyor is in the original position, the spiral arm is rotated, the table is lowered), due to the grinding head at this time In the upper position, that is, 3.10 is closed, press the cycle cycle button, and the cycle starts. When the conveyor encounters the deceleration signal of 4. 05, the left and right grinding lubrication design main parameters cylinder number length direction width direction air pressure hydraulic wheel speed r / min grinding time S grinding size after grinding size grinding time S pre-grinding size After grinding, the size head advances and the large surface begins to grind. After the large surface is finished, the left and right grinding heads are returned.
When the large surface is finished, the workbench turns left 90. After the small surface starts grinding, after the small surface is finished, the work table is raised, and the work table is turned to the right 90Â° automatic running state, when the conveyor returns or the worktable turns right. 90., left and right grinding head back.
After the work, the actual cutting operation was carried out on site, and the four faces of the cylinder blank of the foundry were ground. The results are as follows: The cleaning grinder in this subject has not been produced by the manufacturer in China, and it has a certain manufacturing. Difficulties, some parts need special customization, after the mapping of a US-made cleaning equipment used at the production site, combined with the specific requirements of the foundry, localized design, to provide the foundry with the process requirements, work performance Good, easy to maintain cylinder cleaning machine. The manufacturing cost is about 900,000 yuan less than the purchase of the same machine tool from abroad. In today's enterprises pay more attention to the quality of products to reduce production costs, in the processing of cylinder castings, the use of the grinding machine for Dongfeng Motor Co., Ltd. foundry to enhance the production capacity and efficiency of products, improve product quality provides a reliable guarantee.
Wu Zongze Editor's Manual for Mechanical Design Beijing: Mechanical Industry Press, 2002 Li Bomin, Zhao Bo, Editor-in-Chief, Modern Grinding Technology Beijing: Mechanical Industry Press, 2003 Sun Gongshou Tang Xiquan, etc. Edited Grinding Machine Refinement and Renovation Beijing: Mechanical Industry Press, Li Bomin, ed. Cutting Technology" Beijing: Mechanical Industry Press. 1996 Liu Chong editor-in-chief "Modern Design Method for Rolling Bearing System Application" Beijing: Ocean Press. 1993 1994 (2nd edition)
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