Unlike previous design procedures for parallel machine tools (PMTs), this paper first analyzes the path and posture requirements of the tools in universal processing, then proposes and constructs a new class of PMs that can provide the required path and posture. This opens up new ideas for the design of PMTs. Based on the reciprocal screw theory, a type synthesis process of asymmetrical lower-mobility PMs was proposed. Through this process, a novel class of four-limbed parallel mechanisms (PMs) providing three translations and one rotation around a horizontal axis (y-axis), denoted as 4-3T1R(y) PMs, was successfully proposed and constructed. Such PMs can be applied to the design of PMTs, especially the design of micro-electrical discharge machining (micro-EDM) PMTs. The structural design of a new 2RRC-2CRU PM, which was a member of 4-3T1R(y) PMs, was performed, and its mobility was analyzed in detail to demonstrate the efficiency of the proposed type synthesis process. The inverse, forward, and velocity kinematics problems of the 2RRC-2CRU PM were solved for further applications.
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