Behrokh Khoshnevis

Integration of process planning and scheduling— a review

In recent years, a few researchers have addressed the need for the integration of process planning and scheduling functions in order to achieve superior overall system performance. Many of these researchers have discovered that the potential savings are substantial when process planning and scheduling are integrated. It has been reported that typical scheduling objectives, such as minimizing makespan, maximizing equipment utilization, etc, can be significantly improved as the result of integration of these two important manufacturing system functions. In this paper, we present a review of the reported research in this area, discuss the extent of applicability of various approaches, and suggest directions for future research.

Integration of process planning and scheduling functions

Automated process planning (APP) has received a considerable amount of attention in recent years. This has mainly been due to APP allowing for the bridging of the gap between design and manufacturing, and for its automation of the related tedious human task. While there have been several efforts in developing interfaces between computer-aided design (CAD) and APP, little attention has been given to the integration of APP and scheduling, which is likely to be of even higher importance. This paper addresses the basic issues involved in the integration of the two functions, demonstrates a methodology and the potential benefits of the integrated approach by an example, and presents directions for future research.

Mega-scale fabrication by Contour Crafting

Contour Crafting is a mega scale layered fabrication process which builds large scale three-dimensional parts by depositing paste materials layer by layer at unprecedented speed and with superior surface quality. This paper presents an overview of related research activities and the progress aimed at extending the technology to construction of residential housing units and civil structures.

Digital material fabrication using mask‐image‐projection‐based stereolithography

Purpose – The purpose of this paper is to present a mask‐image‐projection‐based stereolithography (MIP‐SL) process that can combine two base materials with various concentrations and structures to produce a solid object with desired material characteristics. Stereolithography is an additive manufacturing process in which liquid photopolymer resin is cross‐linked and converted to solid. The fabrication of digital material requires frequent resin changes during the building process. The process presented in this paper attempts to address the related challenges in achieving such fabrication capability.Design/methodology/approach – A two‐channel system design is presented for the multi‐material MIP‐SL process. In such a design, a coated thick film and linear motions in two axes are used to reduce the separation force of a cured layer. The material cleaning approach to thoroughly remove resin residue on built surfaces is presented for the developed process. Based on a developed testbed, experimental studies we...

Generation of alternative process plans in integrated manufacturing systems

The availability of alternative process plans is a key factor for integration of design, process planning, and scheduling functions. The availability of alternative process plans can speed up the process of incremental process plan generation which can help in providing real time cost feed back to the designer after each design modification. Also alternative process plans relax the constraints in the optimization of production schedules, which in turn results in more efficient use of production resources and better delivery schedules. This paper describes a methodology for generation of alternative process plans in the integrated manufacturing environment. The procedure consists of: selection of alternative machining processes, clustering and sequencing of machining processes, and generation of a process plan network. Each of these steps is explained in detail. The result of the procedure is the process plan network that provides all alternative process plans for the given part. Methods for the selection of an optimal process plan are also described. Computational complexity of the procedure is discussed and experimental results on several realistic examples are shown.

Lunar Contour Crafting: A Novel Technique for ISRU-Based Habitat Development

As the nation prepares to return to the Moon, it is apparent that the viability of long duration visits with appropriate radiation shielding/crew protection, hinges on the development of Lunar structures, preferably in advance of a manned landing, and preferably utilizing in-situ resources. Contour Crafting is a USC-patented technique for automated development of terrestrial concrete-based structures. The process is relatively fast, completely automated, and supports the incorporation of various infrastructure elements such as plumbing and electrical wiring. This paper will present a conceptual design of a Lunar Contour Crafting system designed to autonomously fabricate integrated structures on the Lunar surface using high-strength concrete based on Lunar regolith, including glass reinforcement rods or fibers fabricated from melted regolith. Design concepts will be presented, as well as results of initial tests aimed at concrete and glass production using Lunar regolith simulant. Key issues and concerns will be presented, along with design concepts for an LCC testbed to be developed at MSFCs Prototype Development Laboratory (PDL).

Process planning knowledge representation using an object-oriented data model

The issues involved in forming proper knowledge representation for process planning are discussed. Following a brief review of knowledge representation schemes used in existing reported CAPP systems, the process planning function and its required knowledge are described. Then an object-oriented knowledge representation scheme is presented that allows both upstream and downstream integration of CAPP and makes it easily adaptable for interfacing with other computer integrated manufacturing CIM modules. Descriptions of machining process entities and their relationships with features, machines and tools are provided. The network representation of the process plan that allows for alternative plans is explained. The application of the scheme within a working process planning system prototype is briefly explained and supported with an example. The benefits of the proposed representation, which include connection with geometric model, reduced search space, and alternative plan generation, are discussed. These new...

Scheduling with flexible process plans

Abstract When a process planning module is embedded into the scheduling paradigm, the solution space of the scheduling problem is expanded due to possible generation and use of alternative process plans, i.e. the combined system of process planning and scheduling is equivalent to scheduling with flexible process plans. This flexibility provides a potential for obtaining improved schedules, but it increases the complexity of the structure of the scheduling problem. This paper describes a solution approach for the integrated system and analyses the performance of a new algorithm under various simulated scenarios.

An integrated process planning system using feature reasoning and space search-based optimization

In this paper we describe the architecture of a new integrated process planning system, called 3I-PP, which is comprised of three modules: feature completion, process selection, and process sequencing. We have applied a knowledge-based approach to feature completion and process selection, and the space search algorithm for process sequencing. The resulting process planning system provides for both upstream and downstream integration of CAPP with CAD and scheduling systems, respectively. Description of the methodologies and procedures is provided and some experimental results that demonstrate the system performance are presented.

Experimental investigation of contour crafting using ceramics materials

This paper presents research about the adaptation of Contour Crafting, a novel prototyping process, for two carefully chosen uncured ceramic materials. The details of the construction and operation of the fabrication machine, as well as procedures and results from our preliminary experimentation are concisely presented.