| Ice skates are key tools of ice sports, whose quality is one of the critical factors that determine whether the skaters can get good grades in the match. In China, only few commodity manufacturing unit can make easy knife board and knife machine and the ice skates are developing mainly by hand, which is not only of low efficiency but also can not ensure the consistency of grinding quality of different ice skates. Therefore, it is imperative under the situation to exploit a new well behaved NC ice skates grinding machine that have independence intellectual property rights. With the development of virtual manufacturing, VP(virtual prototyping)technology is being applied more and more widely. the application of VP technology simplifies the R&D(research and development)process of mechanical products, shortens the period of products development significantly, reduces the R&D cost and improves the products quality obviously from the view of application results. According to this practical situation and current research development, based on investigation of in and out home, we researched a NC grinding machine which can grind the ice skates with any arc for speed skating and short tracks speed skating automatically according to the parameters we set or the shapes of ice skates. With some design parameters, we carried out the movement simulation and rigid dynamics simulation of main shaft bearing system of grinding wheel, and get a satisfied simulation result which further validates the reasonableness of parameters and overall arrangement of prototype machine components. It will play some key role in practically realizing the NC grinding machine.In this paper, starting from the current research in home with definite research goal and content, in virtue of VP technology software, we build up the prototype modeling of NC grinding machine with some design parameters and then successfully simulated the prototype movement. The detailed content about my research includes:1.Investigation of the main technical requirements of ice skates grinder: Based on analyzing the characteristics of grinding motion of the ice skates and the demands for different movements in the grinding process, the overall configuration and concrete components design of the ice skates grinding machine was designed. The grinder I designed is a vertical-shaft-type one which consists of the feed actuation systems in X, Y and Z direction, fixtures and grinding wheel setup. The overall size of the grinder is 800×400×440 mm. The strokes of feed system in X, Y and Z direction are 550 mm, 60 mm and 20 mm respectively. We adopted the ball screw pair with nominal diameter 20 mm, nominal lead 6 mm, and outer diameter 20.3 mm as the motion transmission device of the feed system. The effective lengths of the screws in X, Y and Z axis are determined as 600mm, 90 mm and 48 mm respectively according to the strokes of the grinder in corresponding directions. The stiff of the main spindle is K = 1.15×10 6N /mm calculated by the equation concerned. The grinding force also can be figured out, when the average of grinding depth is 0.005 mm, the tangential force Ft and the normal force Fn correspond to 25 N and 75 N respectively, when the average of grinding depth is 0.020 mm, the tangential force Ft and the normal force Fn correspond to 96 N and 288 N respectively.2.Modeling, virtual assembly and interference analysis: CATIA software was used to draw the 3-D model of each part, assembly them to be a virtual machine, analyze the interference between the parts after assembling finished and successfully construct the VP of the grinder in the end, which is the foundation of motion simulation and dynamic analysis using ADAMS software. When modeling in CATIA, I overleaped or simplified the components that hardly affect the simulation accuracy, for example, I overleaped installation holes, screws and motors, and simplified the structure of fixtures and grinding wheel holder, whereas, I substituted virtual restriction and for the real components in order to decrease the time consumed by modeling and calculation and keep simulation from failure.3.Introduction to the principle of kinematic and dynamic simulation in ADAMS software: In order to fully recognize every component upbuilded in CATIA and ensure their fitting positions, I used the STEP mode with import instruction to import the 3-D model of the grinder drawn by CATIA into ADAMS, added restriction and load to the machine and completed the construction of VP model of the ice skates grinder finally.4.Kinematic simulation: The working process of the grinder is that grinding wheel moves to the starting point, grinds the edge of the ice skates automatically along the curve of the edge and moves back to the starting point waiting for the next machining. The driving function of the feed systems in X, Y and Z directions can be set according to the shape of the ice skates and the grinding time. Before the real grinder is fabricated, the VP model can simulate the working condition of the machine so as to demonstrate the reasonability of the effective length of the screw and determine the rotate speed of each screw at any time and the range s of rotate speed, from which the rotate speed of the motors connected to the three screws.5.Dynamic analysis of the main spindle: The stiffness of main spindle is the ability to counteracting the bend and related to deflection Y of the spindle end with grinding force or driving force applied. Generally speaking, the maximum deflection y max much be small than 0.0002l under the rated load,in this design, if l = 60mm, then y max≤0.012mm. Based on the stiffness of the spindle and grinding force, the simulation parameters can be set. In addition, through measuring the deflection Y of the main spindle end, the stiffness can be demonstrated.Finally, we can come to the conclusion: It is valuable to use the VP technology in the design and development of ice skates grinder. In addition, by the motion simulation and dynamic analysis, the rotate speed of the motors driving the screws in X, Y and Z axis respectively is determined to be 2000 rpm. In the end, we demonstrate that the effective length of the screw is reasonable and the stiffness of the main spindle connected to the grinding wheel can meet the requirement.
|
PDF Full Text Request