Search results

The use of high quality or exotic materials such as heat resistant alloys, high strength steels, stainless and aluminium alloys provide many answers to designers requiring solutions to specific problems, especially in the aerospace industry. However, the downside is that they are often difficult and costly to machine and can pose tremendous problems to production engineers due to their machining characteristics. Machineability, swarf control, work‐hardening and surface finish are a few of the prime headaches facing the production people with drawn‐out cycle times, high tooling bills, low machine utilisation and constant attention geneate concern for management.

THE METAL‐WORKING industry is firmly established as one of the foundations of a modern industrial society. In Britain, which may be taken as fairly representative of such a society, it constitutes the country's largest manufacturing industry employing nearly 3¾ million workers in over 16 theusand plants. Furthermore, apart from the steel industry, which supplies its basic raw material, its anticipated rate of growth is larger than any other industry.

NEW INDUSTRIAL MATERIALS, the demand for higher productivity and the requirements for ever smaller tolerances have resulted in great advances in machine tool design and in cutting tool materials. Cutting fluids have a significant part to play in this story but they can only play their full part if they are correctly chosen and if their proper functions are understood. Increased rates of metal removal can then be achieved and problems associated with difficult or hazardous machining operations reduced or even eliminated.

The purpose of this paper is to investigate the efficiency of cutting fluids when end milling AISI 304 stainless steels.

Two groups of cutting tests were conducted, one with the application of a coolant (wet machining) and the other – without (dry cutting), using multilayer coated carbide inserts. The findings of tool life and tool wear mechanisms are compared.

Coolant application proves to be efficient at low‐cutting speeds. With increasing the cutting speed, the coolant effect on improving tool life becomes less significant. Built‐up edge and nose wear are the dominant failure mechanisms in dry machining, while in wet machining, the dominant mechanisms are found to be notch wear and cutting edge grooving.

This paper provides useful information for manufacturing engineers dealing with end milling of stainless steel components. It helps select beneficial cutting conditions for dry and wet end milling operations.

Change of machine layout is often required for small quantity and diversified orders in the apparel manufacturing industry. The purpose of this paper is to use a hierarchical order‐based genetic algorithm to quickly identify an optimal layout that effectively shortens the distance among cutting pieces, thereby reducing production costs.

The chromosomes of the hierarchical order‐based genetic algorithm consist of the control genes and the modular genes to acquire the parametric genes, a precedence matrix and a from‐to matrix to calculate the distance among cutting pieces.

The paper used a men's shirt manufacturing as an example for testing the results of a U‐shaped single‐row machine layout to quickly determine an optimal layout and improve effectiveness by approximately 21.4 percent.

The manufacturing order is known. The machine layout is in a linear single‐row flow path. The machine layout of the sewing department is independently planned.

The advantage of the hierarchical order‐based genetic algorithm proposed is that it is able to make random and global searches to determine the optimal solution for multiple sites simultaneously and also to increase algorithm efficiency and shorten the distance among cutting pieces effectively according to manufacturing order and limited conditions.

Machining fixtures must fit exactly the work piece to support it appropriately. Even slight change in the design of the work piece renders the costly fixture useless. Substitution of traditional fixtures by a programmable multi‐robot system supporting the work pieces requires a specific control system and a specific programming method enabling its quick reconfiguration. The purpose of this paper is to develop a novel approach to task planning (programming) of the reconfigurable fixture system.

The multi‐robot control system has been designed following a formal approach based on the definition of the system structure in terms of agents and transition function definition of their behaviour. Thus, a modular system resulted, enabling software parameterisation. This facilitated the introduction of changes brought about by testing different variants of the mechanical structure of the system. A novel approach to task planning (programming) of the reconfigurable fixture system has been developed. Its solution is based on constraint satisfaction problem approach. The planner takes into account physical, geometrical, and time‐related constraints.

Reconfigurable fixture programming is performed by supplying CAD definition of the work piece. Out of this data the positions of the robots and the locations of the supporting heads are automatically generated. This proved to be an effective programming method. The control system on the basis of the thus obtained plan effectively controls the behaviours of the supporting robots in both drilling and milling operations.

The shop‐floor experiments with the system showed that the work piece is held stiffly enough for both milling and drilling operations performed by the CNC machine. If the number of diverse work piece shapes is large, the reconfigurable fixture is a cost‐effective alternative to the necessary multitude of traditional fixtures. Moreover, the proposed design approach enables the control system to handle a variable number of controlled robots and accommodates possible changes to the hardware of the work piece supporting robots.

A review is made of existing and likely future aircraft materials and their choice for use on airframes is discussed in relation to the problems of advanced aircraft design. Both technological and production problems arc included and it is finally suggested that urgent governmental action is required to remedy Great Britain's grave lack of suitable capital equipment.

THAT the United States should have taken speedy steps to bolster the dollar was to be expected. The fall was dramatic and laden with dire possibilities for American pride. That it would have helped considerably in their export field had perforce to take second place.

A Yamazaki H22 power centre has reduced overall lead time for the production of certain aero engine components from 20–24 weeks using conventional methods, to just six weeks.

WELLS Krautkramer has introduced a new range of British designed and built ultrasonic immersion testing systems for detecting minute flaws in large, safety‐critical components such as aero engine turbine discs and rings.