Dimensioning of the intermediate states of the machined phases “DISMP” approach

In manufacturing practice for each machining operation, transfer techniques are extensively used for the allocation of manufacturing specification tolerance type and value. This paper focuses more on tolerance type which is the basis for a coherent and complete tolerancing process. We developed an algorithmic method called “DISMP” in order to generate the necessary types of manufacturing specifications that guarantee the respect of the functional requirements. A geometric variation model, based on the invariants degrees of freedom (DOFs) of the datum reference frames (DRF) and the toleranced surfaces serves to specify the two extremities of the tolerance chain. The identification of the controlled DOFs (Cont-DOFs) of the positioning reference frames in each machining phases and also the constrained DOFs (Cons-DOFs) of each machined surface contributes to the development of the way linking between the functional toleranced surface and its functional DRF. To generate the appropriate manufacturing geometric specifications, our method can be divided in five steps. We started by the translation of the ISO functional specification using the topologically and technologically related surfaces rules “TTRS” (Step 1: M1). Mapping the manufacturing process (Step 2: M2 and M3) requires the identification of the Cons-DOFs of the machined surfaces and those controlled by the positioning surfaces “Cont-DOFs” in each phase. The search of all chain links, which constitute the tolerance chain, is realized on Step3 (M4 and M5). Then, in step 4 (M6), we generate ISO standardized manufacturing specification. The fifth step (M7) draft technological constraints related to the manufacturing process, i.e., the case where there are inversion in the order between the toleranced surfaces and its DRF. Finally, we present the manufacturing process phases with ISO standards requirements.