Abstract
This article proposed a two-phase design scheme of Stephenson six-bar working mechanisms for servo mechanical presses with high mechanical advantage. In the qualitative design phase, first, a Stephenson six-bar mechanism with a slide was derived from Stephenson six-bar kinematic chains. Second, based on the instant center analysis method, the relationship between mechanical advantage and some special instant centers was founded, and accordingly a primary mechanism configuration with high mechanical advantage was designed qualitatively. Then, a parameterized prototype model was established, and the influences of design parameters toward slide kinematical characteristics were analyzed. In the quantitative design phase, a multi-objective optimization model, aiming at high mechanical advantage and dwelling characteristics, was built, and a case design was done to find optimal dimensions. Finally, simulations based on the software ADAMS were conducted to compare the transmission characteristics of the optimized working mechanism with that of slide-crank mechanism and symmetrical toggle mechanism, and an experimental press was made to validate the design scheme. The simulation and experiment results show that, compared with general working mechanisms, the Stephenson six-bar working mechanism has higher mechanical advantage and better dwelling characteristics, reducing capacities and costs of servo motors effectively.
Highlights
Servo mechanical presses are novel metal forming equipments utilizing servo drive technology
The most common working mechanism for traditional mechanical presses is the slide-crank mechanism (SCM) with a heavy flywheel mounted on the highspeed shaft
The purpose of this study is to propose a two-phase design scheme, qualitative and quantitative, to obtain a Stephenson six-bar working mechanism with high mechanical advantage for 1 degree-of-freedom servo mechanical presses, reducing the required PMSM capacity and improving the controllability, without decreasing the production efficiency
Summary
Servo mechanical presses are novel metal forming equipments utilizing servo drive technology. They can offer the flexibility of hydraulic presses and productivity of mechanical presses, being propitious to improve the forming limit, product accuracy, and working environment.[1]. The most common working mechanism for traditional mechanical presses is the slide-crank mechanism (SCM) with a heavy flywheel mounted on the highspeed shaft. For most servo mechanical presses, flywheels have to be removed and the forming forces are supplied totally by servo motors (usually, permanent magnet synchronous motors (PMSMs)). When common SCMs with low mechnical advantage are adopted as working mechanisms of servo presses, the capacities of PMSMs would have to been increased greatly, which raising manufacturing costs and hindering development and popularity of servo mechanical presses, especially the large-tonnage ones
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