Emerald Group Publishing Limited
Copyright © 2004, Emerald Group Publishing Limited
Assembly – unplugged
Assembly – unplugged
Keywords: Assembly, Simulation
Ernest Appleton is with the Manufacturing Group, School of Engineering, University of Durham, South Road, Durham, DH1 3LE. Tel: 0191 3342000; Fax: 0191 3747316; E-mail: firstname.lastname@example.org
Many readers will be familiar with the fashion in modern music for established stars to forgo their electric instruments and complex recording techniques in favour of a simpler, more natural sound using acoustic instruments. It seems that the aim is for the performer to display musical skill rather than their use of technology.
I experienced a similar “unplugging” when I abandoned the use of the computer as an aid to Design for Assembly and instead developed an approach based on a multi-discipline team, working through a loose framework of systematic design assessments and design modification.
Let me start by giving proper credit. I believe that Geoff Boothroyd, a man familiar to most of you, has had an impact on modern manufacture comparable to Whitworth or Ford in the past. He laid a foundation for the understanding of assembly, based on a scientific approach that has impacted both automatic and manual assembly alike. Through a couple of generations he has taught engineers to design everyday products so that they are simpler and easier to assemble and he has influenced very many of the everyday products we find in our homes and workplaces.
As with many things in life his work can be summed up in simple guidelines.
Make the number of parts in an assembly as small as possible.
Make it as easy as possible to get the part in the right orientation.
Make the part as easy as possible to insert into its place.
Those who followed him, including myself, used his tables and charts to score the assemblability of products. Later, Geoff with his colleague Peter Dewhurst removed the tedium of form filling and calculation by embedding their method into a computer programme. After years of teaching the use of that software directly or using authorised consultants I began to realise that the use of a computer in this instance was a step too far. The computer approach moved my students away from the redesign task. The process became one of battling to tell the computer about the parts and the assembly task, usually a frustrating experience. I found that they could get a score for assemblability, but no insight into how to improve the design. With my colleague John Garside we decided to put away the keyboard, unplug the computer and devise a method based upon teamwork and some post-it pads. We kept the Boothroyd rules and guidelines and we kept his disciplined structured approach, but we moved the redesign of the product to the focus of the process.
Instead of asking the computer about the difficulty of each assembly task we asked the team members to give subjective scores. They proved remarkably reliable. The results of applying this approach have been quite staggering. First the process is fun, it allows and encourages commitment and the results can be seen within a relatively short time. Improvements in assemblability have been significant as measured by part count reduction and ease of orientation and insertion. It has also proved to be effective at bringing design and manufacturing departments closer together. This unplugged approach does not wring out ever penny of cost, as would be expected from the rigorous application of the Boothroyd/ Dewhurst software, but for lower volume products it is a simple and effective way of making significant cost savings. Of course we still use the computer to record our process, but in this way the computer is the servant of the designer rather than the master.
My conclusion, from this experience and an observation of manufacture over the last 30 years, is that we do not always have to totally automate a process and often the fusion of the best of the machine and the best of human skill and ingenuity produces the most effective solution. I welcome this special edition of Assembly Automation and encourage the contributors to continue to look for the best ways to combine man and machine.