Research on rigid flexible coupling dynamic characteristics of clamping unit in injection molding machine（b）

Date：2014/11/3 16:52:30

The 2.2 locking mechanism of rigid flexible coupling dynamic modeling

The establishment of a flexible body in 2.2.1 ADAMS

The establishment of a flexible body in ADAMS there are two main methods: one is to use ADAMS/autoflex module to convert the existing model of arigid flexible body; another is the use of finite element analysis software will be rigid body discrete grid units, modal calculation after the formation of the flexible body modes in the MNF file, and then read in ADAMS modal neutralthe file will soften, rigid body. The modal neutral file contains a flexible bodyquality, centroid, moment of inertia, frequency and mode of vibrationinformation. In the choice of softening method, according to the rigid structure and geometry to determine. If you want to soften the rigidstructure simple, regular shape, can use the first method, namely automaticsoftening method; on the contrary, the selection of the second methods,namely the method of modal neutral file to import.

The establishment of 2.2.2 rigid flexible coupling model

The working process of compound die mechanism, due to the presence ofopening mould shock and locking elastic deformation, fully to the model asrigid system to process and can not achieve the accuracy requirements.Therefore, based on the rigid body model, the pull rod, clampingmechanism stiffness at relatively small toggle, toggle, before the small connecting rod and crosshead flexible treatment, the other parts are stillconsidered as rigid body. Because of the shape of parts is relatively simple rules, first flexible body method of establishing complete from rigid to flexible body transformation is adopted in this paper.

2.2.3 die contact force parameter setting

In the model, by setting the mould clamping force contact force simulationmode locking process when the elastic modulus of deformation produced by the system. ADAMS software for contact defines the interaction between objects collision free motion simulation of contact between objects in the process of. ADAMS/solver uses two methods to calculate the contact force(normal force): regression method (restitution) and the method of impact function. Relatively speaking, regression parameters are difficult to be set up, so more of the latter choice to calculate the contact force. The impact function method is to calculate the contact force between the two components based on the impact function, the contact force is composed of two parts: one is between the two components are cut into the elastic force is generated, the other is a damping force due to the relative movement of the two member. This paper uses the impact function to calculate thecontact force, parameter settings are as follows: the stiffness coefficient(Stiffness) 1 * 105N/mm, collision coefficient (ForceExponent) in 1.5, the maximum damping coefficient (Damping) from 50N s/mm, the depth of cut(PenetrationDepth) 0.1mm.

Analysis of 3 clamping mechanism and dynamic simulation results

Taking the mould clamping mechanism of a piston push rod a constantspeed of v=100mm/s, the simulation time is t=2.92s, the simulation step number 100, respectively on the mould clamping mechanism of rigid model and rigid flexible coupling model simulation analysis. Get the rigid model and rigid flexible coupling model of clamping mechanism model andkinematics and dynamics of each component of mode-locked conditionresponse curve by simulation. In mode locking when clamping mechanismpull rod pull, toggle compression, the maximum displacement occurred inbar and toggle respective hinging, the simulation result is consistent with the expected. The following will be to force motion template and crossheadfor example analysis of rigid flexible coupling simulation results.

Analysis of 3.1 dynamic template movement speed

The center of mass velocity curve of rigid flexible coupling model and template for rigid body model is basically similar, are moving characteristics of slow fast slow. The difference is the rigid flexible coupling model dynamic template speed in opening mould stage (0 ~ 0.2S) since the opening mouldinertial impact velocities exist great fluctuation, and the rigid body model does not consider the vibration phenomenon caused by the elastic deformation of components caused by the short time speed. This indicates that the rigid flexible coupling model of a rigid body motion model of motioncan be more truly and accurately reflect the actual movementcharacteristics of locking mechanism.

Dynamic stress analysis of 3.2 cross head

Locking mechanism in the mold closing and locking condition should becross head dynamic equivalent instantaneous stress distribution nephogram and cross head and the cylinder rod units near the hinge point of the response of stress time history. As can be seen in the opening mouldstage 0 ~ 0.2S period of time, because the opening mould shock caused by the element stress appear larger fluctuation, the maximum equivalent stress reached 18.1MPa. The locking phase, with the mold closing unit gradually,stress decreases, the maximum stress reached 29.4MPa. This is because the deformation force when the mode locking mechanism is growing faster than the amplification mechanism after unclamping force increases speed,cross head thrust is required to overcome the deformation resistanceincreases gradually; and when the mould moving force is greater than thegrowth rate of the amplified deformation force increases speed, cross headthrust required decreases gradually.

Thus, compared with the static stress analysis and simulation calculation of stress distribution can get not only the components of the instantaneousrigid flexible coupling, and can track the time history analysis, so as to lay the foundation for the fatigue life of components.

4 Conclusion

1) ADAMS double toggle dynamics simulation provide more clamping mechanism based on rigid flexible coupling, respectively to move the template and the cross head analysis, dynamics simulation results canreasonably reflect the real double toggle clamping mechanism, explain thefeasibility of simulation and research for locking mechanism of double toggle the application of rigid flexible coupling model.

2) the rigid flexible coupling technique can be FEM and multi-body dynamicstechnique together, not only can the kinematics and dynamics performanceparameters for solving mechanism, and can provide structural performance analysis for the structure design, to provide dynamic load forecasting data for fatigue life of component analysis after.

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