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News Release from: Mike Page - editor's feature articles | Subject: Lean manufacturing
Edited by the Manufacturingtalk Editorial
Team on 12 October 2007
Lean manufacturing and 'one-hit'
machining
Lean manufacturing and 'one-hit' machining techniques are ways of retaining machine shop activity at European plants instead of letting the work go abroad, writes Mike Page.
There are many arguments for not letting machining jobs go abroad It is well known that overseas low cost labour advantages can be offset by communications and cultural problems, and quality control and quality assurance difficulties
There is also the problem that with the supplier being hundreds or thousands of kilometres/miles away, solving problems in 'real time' can be difficult.
US and European machine shops are finding two key strategies that will help to keep the work 'at home'.
One is 'lean' manufacturing and the other is 'one hit' machining.
On lean manufacturing, ask how is your machine shop organised? Your survival as a stand-alone company or a division inside a big operation may be questionable if you still have an 'operation' focussed plant layout.
By that, I mean a 'milling' department, 'turning' section, 'grinding bay', 'deburring bench', and so on.
Such a layout slows up work through the plant.
You have stacks/stores of 'work in progress' (WIP) or 'production inventory' lying about the place waiting for the next operation or intermediate inspection.
It adds to costs - not just WIP but associated labour time too.
Depending on the type of work, some jobs may have longer set-up times than actual machining time.
Lean manufacturing is seen by some machine shops as a way of reducing or eliminating 'added value'.
A tool setter's or deburrer's time is adding to the product costs, and you have to ask whether the existing practices are serving the customer properly.
Some years ago, I was astounded by the productivity gains a tractor plant - near Moline, Illinois, USA - achieved through simply reorganising its machining/sheet metal working/ancillary operations into 'cells'.
The general idea was that cells were set up to produce similar 'families' of products.
Each cell carried out all the operations to finish a component ready for assembly.
The cells also carried out inspection and any re-work, ensuring that components were ready for assembly.
In turn, the practice saved time in the assembly shops.
That was in the late 1980s.
Like many companies that have followed the 'cell' idea, it was before the advent of truly multi-function/multi-tasking machine tools.
Certainly there were three-axis milling machines, three-axis lathes and CNC punching and laser profiling machines to include in the cells.
Perhaps even more intriguing, four years ago, was to observe the reorganisation at a manufacturer of turbine engines.
The production lead-time - from raw materials in the door to finished product, ready for testing - was about 100 days.
Some components barely saw one day of actual machining during that time.
The machine shop was largely traditional - separate turning, milling, grinding, deburring, broaching, hand finishing sections.
Many parts had to queue up between operations for inspection in separate departments.
Now, components are produced in cells and the latest multi-function/multi-tasking machine tools have replaced traditional 2/3-axis lathes, machining centres and grinding machines.
The dream of producing a turbine engine within 40 days is now real.
Having machine tools that can turn, mill, drill and even broach hole profiles and hob splines in one set-up bring enormous gains.
Probing systems for tools and in-progress checking for the work also reduce inspection needs away from the machine tool.
There are machines that include grinding cycles as well as turn-mill.
The buyer has to be sure that the machine tool is fully protected against grinding grit.
There are machining centres that will machine stock from a bar feeder, instead of accepting sawn billets.
Four- or five-axis machine tools (not necessarily continuous path) will save multi-machine operation.
A 3+2 axis machining centre might also not only avoid progressing work through two or three 3-axis millers, as different tooling attitudes can be called up, but also on fixturing.
Often special fixturing needs to be made to present a work piece in a particular attitude on a 3-axis machining centre, while a 3+1 or a 3+2 axis machining centre might do the work in standard 'off-the-shelf' workholding equipment in one set-up.
If much of the work is in 'medium batch' sizes and can be held in a chuck, then consider the 'hanging spindle' or 'pick-up spindle' turning or mill-turn centres.
These machines can do the work unmanned, and are fed by relatively simple conveyor systems.
To keep machining work 'at home' it is time to evaluate your existing machine shop strategies.
Look at the shop layout, the amount of WIP, machine downtime for setting up, and all the associated job 'waiting times'.
Introducing cells could be the first step towards improving productivity.
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