The preparation process of the metallographic sample usually includes four steps of intercepting the sample, setting the sample, grinding the sample and polishing the sample. Each stage of the sample preparation process must be carefully operated, as any errors will affect the preparation of the subsequent steps. Properly prepared samples suitable for metallographic observation are the basis for various studies. The failure to produce a sample seriously affects the organization of the metallographic analysis, and the error microstructure can have immeasurable consequences. The prepared sample needs to represent the object to be studied. It is necessary to ensure that the analysis surface of the metallographic sample is mirror-finished without scratch defects, which is not conducive to the observation of the microstructure. At present, the method of preparing samples in various enterprises and research institutes is still at the stage of manual preparation. There are many steps in the manual sample preparation process, and the sampler is required to have a skilled technical level and a wealth of experience in processing the sample, so that the efficiency of the preparation of the sample is very low. With the rapid development of information engineering and cybernetics, computer-controlled mechanical equipment for the acquisition of metallographic samples has gradually replaced the traditional equipment for manual sample preparation, and the efficiency has been greatly improved. The quality is also perfect. Foreign metallographic sample cutting machines have developed well, but they are expensive. The metallographic sample cutting machine in China has low automation and low precision, so it is of great significance to design and develop an automated metallographic sample cutting machine. The highly automated metallographic sample cutting machine mainly consists of a mechanical part and a control part. This paper selects and designs the relevant parts for the mechanical part of the metallographic sample cutting machine to suit the mechanical structure requirements of the mechatronics product. .
2The overall design and design of the cutting machine adopts the desktop structure. The cutting method adopts the fixed form of the main motor and the grinding wheel. The stepping motor drives the feeding system so that the table with the sample is close to the grinding wheel, according to the sample size. Select the appropriate cutting mode for cutting.
The mechanical part of the designed metallographic sample cutting machine is composed of a body, a cutting mechanism, a feeding mechanism, a clamp and a cooling system. The main motor and the shaft support frame are mounted on the H-shaped steel base, and the two V-belts are used for power transmission. The main motor drives the cutting blade to rotate after being driven by the pulley, which can protect the cutting mechanism from being damaged in the event of an accident. In order to meet the requirements of various materials, the spindle can be rotated at 3000r/min, 1500r/min and 1000r/min. The spindle speed can be controlled by the single-chip microcomputer controlling the working pole of the main motor. The longitudinal stepping motor is mounted on the frame, and the extended end of the motor is connected with the longitudinal lead screw and then mounted on the frame through the bearing seat. The longitudinal nut is fixed to the transverse feed frame, and the transverse feed motor passes through the coupling. It is connected to the transverse screw and mounted on the transverse feed frame. The transverse nut is fixed to the vertical feed frame. The vertical feed motor is connected to the vertical screw through the coupling and mounted on the vertical feed frame. Vertical nut Fix the sample feed with the feed table. The entire feed mechanism is isolated from the outside by a feed hood to prevent damage to the feed mechanism caused by dust or the like. The entire cutting process is carried out in a closed state, with two limit switches and one displacement sensor in each of the three feed directions to facilitate control and prevent overtravel.
Called the feeding mechanism. Longitudinal feed 2. Horizontal feed 3. Vertical feed 3 The main part of the design frame is welded with H-beam, and the hole for bolt connection can be machined at the appropriate position of the H-beam, which can easily fix the feed mechanism. The belt drive for cutting allows the rotation of the main motor to be transmitted to the cutting spindle, thereby driving the grinding wheel to rotate. In order to install and periodically tension the belt, the position of the main motor can be moved back and forth in the horizontal plane; in order to reduce the radial force of the belt to the main shaft, the main pulley is designed as an unloading pulley; in order to adjust the axial clearance of the bearing, The adjustment gasket is designed; in order to make the spindle have good lubrication conditions, oil lubrication and oil mark design are adopted, and the lubrication state can be easily known.
3.2 The feed mechanism speed is continuously adjustable within a certain range, and the stepping motor is selected as the feed motor.
In order to stabilize the feeding process and avoid low-speed creeping, the ball screw is used to convert the rotation of the motor into the movement of the mechanism. In the working process of the metallographic sample cutting machine, the feeding mechanism is not stressed, and the torque of the ball screw is increased, so the actual output torque of the stepping motor is small, and the flange coupling can be used. The output of the stepper motor is directly connected to the lead screw. In this design, the measurement main body form of the coordinate measuring machine of the form of GB/T5843GY1. Feeding mechanism is selected. In this design the longitudinal movement is done by a longitudinal screw nut, the lateral movement is done by a transverse screw nut coupled to the longitudinal nut, and the vertical movement is done by a vertical screw nut coupled to the transverse nut, as shown.
3.3 Fixture and cooling system design Because the screw clamping mechanism is widely used in the clamping mechanism, it has the characteristics of good self-locking property, large adjustment range of clamping stroke and large force ratio. In order to avoid damage to the surface of the sample, the screw clamp is used for screw clamping. The handwheel is designed to increase the flexibility of clamping the workpiece.
In order to automatically align the sample with the axis of the grinding wheel after clamping, the two pressure blocks are made movable, and the left-hand thread and the right-hand thread are respectively processed on the same shaft, and the left-hand thread can be made by different rotation directions. The two clamps respectively connected with the right-handed thread have different moving directions, so that the automatic centering of the sample clamping can be achieved, and the sample axis is in the same vertical plane as the spindle axis after the clamping, which simplifies cutting. process.
When cutting the specimen, if the specimen is fed linearly, the maximum specimen diameter that the grinding wheel can cut is the effective cutting depth of the grinding wheel. If the specimen is rotated 180 and fed again after feeding a radius value, in this case The maximum sample radius that can be machined by the grinding wheel is the effective cutting depth of the grinding wheel. Thus, when cutting a large sample of the same diameter, a grinding wheel having a smaller diameter can be used, which is advantageous for miniaturization of the cutting machine. In practice, each rotation is 120 to reduce the difficulty of operation.
The cooling system designed in this paper is mainly composed of a cooling pump, a watering cover, an inlet pipe, an outlet pipe, a water tank, a return pipe and a filter. In order to meet the needs of small equipment and save mechanical devices, the protective cover of the semi-circular grinding wheel is converted into a watering cover in the design. The wheel cover is actually designed as a two-layer structure that can hold pre-selected coolant. A plurality of small holes are formed in the inner layer of the grinding wheel cover, and a small hole at a specific angle is formed in the lower part of the grinding wheel cover, so that the sprayed cooling liquid can reach any place where the grinding wheel piece contacts the sample, thereby greatly improving the cooling effect. It must be pointed out that the control system should start the operation of the cooling system before the main motor works. During the cutting process, the cooling pump draws out the coolant in the water tank and sprays it onto the cut sample and the grinding wheel to ensure simultaneous cooling. The water tank is equipped with a filter that filters out the chips from the coolant. Recycle the coolant for reuse.
4 Conclusion The spindle speed is driven by a three-phase variable speed asynchronous motor, which can select different speeds when cutting different materials, eliminating the shifting mechanism, simplifying the system structure and improving the transmission efficiency.
The feed mechanism is driven by a stepper motor and uses a ball screw drive to improve the feed transmission efficiency and avoid creep during low speed feed. Two travel switches in each feed direction ensure that the machine will not be damaged if the control system fails.
A multi-purpose fixture was designed to double the diameter of the specimen that the cutter system can cut, increasing the cutting range and miniaturizing the machine.
Sun Weilian, Wang Chengwei, Xu Lihong, et al. Overview of domestic and international research on metallographic cutting machines. Physical and Chemical Testing - Physical Volume, 2003, 39 (7): 357-360. High School Peng. Research on large-scale metallographic sample cutting machine control system based on touch screen and PLC. Baoding: Hebei Agricultural University, 2007. Wang Huiqiang. Mechanical design and research of large four-axis metallographic test cutting machine. Zhangjiakou: Hebei Agricultural University, 2006. Simulation verification and optimization analysis of locust jumping principle LIU Xiaohui, HU Jinshou, LI Jiangbo, DAI Shuangshuang, WANG Xiaoyu, GAO Xu, Jin Yue (School of Mechanical Engineering, Xi'an Jiaotong University, Xi'an 710049, China) A three-dimensional simplified model was established to simulate the locust jump, and the simplified model was optimized in size to optimize the height and distance of the locust jump. Divergent thinking on the optimized model can be provided for the research of jumping robots.
The robot provides the basis for the model and principle.
2 The structure and jumping principle of aphids See the structure of aphids. The body of the locust is flat and consists of three parts: the head, the chest and the abdomen. The chest has three pairs of feet, the forefoot and the midfoot are shorter, supporting the body to balance, and the hind foot is longer, playing an important role in the jumping process.
1 Introduction In recent years, people have paid more and more attention to the application of some special structures of biology to production and life, and established bionics. Most of the robots used in the fields of rescue, detection, and off-road use wheel, crawler, and walking. They have obvious defects in the harsh conditions, and jumping robots have emerged. In nature, creatures such as locusts, kangaroos, and fleas have strong bounce ability. According to their identical structure, a large number of bionic jumping robots have been studied. Jumping robots have their own advantages in the field of robotics: (1) obstacles that can exceed several times their own size; 2) sudden and explosive nature of jumping movements help robots avoid danger; 3) with crawling and walking The combination of methods can greatly improve the range of motion of the robot.
In addition, in interstellar exploration, because the gravitational acceleration of the Moon and Mars surface is much lower than that of the Earth, the jumping movement can make full use of this advantage, saving sports energy and expanding the activity space.
The aphid hind foot can be simplified to the mechanism shown in (a), consisting of three rods of AB, CD and DE, with B and D as the fulcrum. From the structure of the hind foot of the locust, it can be seen that the connection point of the locust muscle is at the end of the scorpion. When the mites jump, the muscles of the leg joints instantaneously exert force, and the support of the sacs on the ground forms a lever structure to lift the body forward. jump. At the moment the locusts jump, the locusts have a force on the ground, using the reaction of the ground to move the mites' bodies upwards. It can be seen that the action of the leg muscles and the action of the sacs cooperate to make the mites complete the process of jumping.
Research on sample cutting machine; Chen Hui (1974-), female, associate professor, master tutor, the main research direction is material development and manufacturing.
Through the in-depth study of the structure of locusts, based on the analysis of the structure of locusts by Chen Yong et al., starting from the principle of locust jumping, the muscles of the locust thighs were driven by the kinematics and dynamics analysis. The locust kinetic model was established by using ADAMS virtual prototyping technology. The optimal height of the locust was optimized by analyzing the jumping height and distance of the locust. The optimized locust structure has greatly improved the height and distance of the locust jumping, which is provided for the research of today's jumping robots. It is a simple structure, lightweight components, and high-performance jumping Wang Qiping. Machine tool fixture design. Harbin: Harbin Institute of Technology Press, 2003. (Editor Ming Tao)
Angular contact ball bearings mainly bear large unidirectional axial load. The greater the contact angle, the greater the load bearing capacity. The material of cage is steel plate, brass or engineering plastics. The forming method is stamping or turning. It is selected according to the bearing form or using condition. Others include combined angular contact ball bearings, double row angular contact ball bearings and four-point contact ball bearings.
Angular contact bearings are able to support radial load and axial load. As single row angular contact ball bearings can only support axial load in single direction, matched bearing mounting is often adopted to them as matched parts of bearings, preload for them is more convenient. Retainers are made of brass, synthetic resins or others subject according to individual bearing features and application conditions.
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