Optimal process plans for manufacturing and tolerance charting

Abstract

A graph theoretical approach is presented that permits the calculation of optimal process plans from datum hierarchy trees, which are elegant representations of tolerance charts. The theory is developed for a cost function that minimizes machine and datum changes. Restrictions on the sequence of machining operations arising from technical constraints or the layout of a group cell are taken into account. The process plans are optimal with respect to a specified datum hierarchy tree, manufacturing constraints and cost function. It is shown that the number of possible plans for real industrial trees is very large, and therefore this kind of optimization is beyond the ability of a human process planner. Trial runs with industrial parts indicate that optimization can be performed by a computer within a time period that is acceptable for industrial use.

A graph theoretic approach linking design dimensioning and process planning

“…However, the reverse is not true. A specified datumhierarchy tree represents a set of process plans; the size of these sets can be enormous [36]. These plans can be ranked in terms of production cost or any other criteria, though all plans result in the same part tolerances.…”

“…Another way of viewing this is to consider a datum-hierarchy tree as a constraint on possible process plans. Once a (valid) datum-hierarchy tree and other manufacturing constraints are established, a process plan can be generated automatically [36].…”

“…Given the concept of an ideal tree that can be directly mapped from a design dimension tree, it is possible to automatically generate and optimise process plans [36,37]. The basic idea is to start with an initial tree, which should be the ideal tree, and then check this against manufacturing constraints.…”

Design analysis and redimensioning of prismatic parts for manufacturability

“…As addressed in , a specified process plan has one and only one datum-hierarchy graph representation. However, the [Thimm et al, 2001].…”

“…The limitation of the system depends only on the logic stored. Because this manufacturing logic is compiled from experiences (know-how of the process planners) and from relevant [Huang and Zhang, 1996;Huang et al, 1997;Huang, 1998;Chu et al, 2000;Qiao et al, 2000;Thimm et al, 2001;Zhou et al, 2002]. Nevertheless, the system can offer automated planning without or little human intervention.…”