Abstract: Motion analysis of negative-rear angle clamping toggle mechanism was carried out, the stationary, rear, and moving plate structure were modeled and analyzed. The speed ratio of moving plate to clamping cylinder of the injection molding machine was related with the clamping mechanism parameters. There was no self-locking of negative-rear angle in the opening mold process, and the clamping process followed a slow-fast-slow mode. In the high-pressure clamping area，the speed of moving plate dropped very quickly. The structure of three plates was optimized through limited element analysis.

Key words: clamping mechanism, motion analysis, template modeling, stress analysis