| Cheap overseas manufacturing has long asked | | | | pay-back period to a minimum, using second and |
| searching questions of the UK manufacturing industry | | | | possibly a third shift. This strategy has the effect of |
| which has struggled to compete on price. The | | | | lowering the hourly machine rate drastically, or to put |
| economics of CNC machining has pushed us towards | | | | it another way, these systems are |
| an emphasis on specialist precision CNC machining like | | | | over-compensated by more intensive utilisation, so |
| the manufacture of aircraft gears, Gleason System | | | | that despite the higher amount invested, a better |
| bevel gears, tight meshing involute splines and gear | | | | utilisation and in most cases higher machine |
| hobbing to international standards. | | | | performance will achieve a reduction in costs. |
| Feasibility Study | | | | It is precisely in this area that the largest amount of |
| It is normal for a company to embark on a feasibility | | | | manoeuvring space for entrepreneurial decisions |
| study prior to the purchase of any capital equipment | | | | occurs. In the early 1980s, a review regarding |
| such as a CNC machine tool. This study fulfils many | | | | machine tool utilisation was conducted and the results |
| functions, such as determining the capacity and | | | | showed that on average only approximately 700-800 |
| power required together with its configuration - | | | | hours per annum were spent actually doing "cutting" |
| horizontal/vertical spindle for a machining centre, or | | | | work. If one refers this to the theoretically available |
| flat, or slant bed for a turning centre. Many other | | | | annual loading time for the machine tool of 364 x 24 |
| features must also be detailed in the study, | | | | hours per day, this time will represent approximately |
| encompassing such factors, in the age of 5-axis | | | | 8%. Obviously, improvements during the last 20 |
| machining, as the number of axes required and | | | | years in the cutting capability of machine tools and |
| whether the machine tool should be loaded manually, | | | | their performance have shown increases averaging |
| by robot, or using pallets. An exhaustive list is drawn | | | | 500% and further drastic savings of time have been |
| up of all the relevant points to be noted and others | | | | achieved in the area of idle times - where higher rapid |
| that at first glance seem rather esoteric, but will | | | | traverse rates and automatic tool and |
| affect the ability of the company to manufacture its | | | | workpiece-changing equipment have been developed. |
| products. It has been shown time and again that | | | | It nevertheless remains a fact, that even though |
| many mistakes have been made in the past when | | | | these are impressive productivity gains, they are a |
| companies rush into the purchase of new equipment | | | | "drop in the ocean" when seen from the overall view |
| without considering all of the problems, not only of | | | | of the plant utilisation throughout the year. |
| the machine tool itself, but of the manning and | | | | So much for the likely problems that face a company |
| training requirements together with its effect on the | | | | embarked on a feasibility study for the purchase of |
| rest of the machine shops productive capability. | | | | new equipment. Just what are the advantages to be |
| Often the fact that an advanced, highly productive | | | | gained from the purchase of the "correct" plant? One |
| machine is now present in the shop could affect the | | | | of the main purposes in using a CNC machine tool is |
| harmonious flow of production, causing bottlenecks | | | | to increase the productive throughput with this |
| later, when the purpose of purchasing the machine | | | | equipment. Although high volume production can |
| was to overcome those problems at an earlier | | | | occur using CNC equipment, it is not alone in this area |
| production stage. Aerospace machine tools have | | | | and under certain conditions can be surpassed by |
| even been purchased in the past without due regard | | | | using more conventional technologies, such as, single |
| for the components they must manufacture, or | | | | and multi-spindle lathes, or plug board machine tools. |
| without correct assessment of future work. | | | | The major feature of a CNC machine tool is its ability |
| This latter point is not often considered, as many | | | | to cut down drastically the lead times for similar |
| companies are all too concerned with today's | | | | components manufactured by a different plant. Even |
| production problems rather than those of the future. | | | | complex doublecurvature component geometries can |
| Taking this theme a little further, in a volatile market | | | | be quickly and successfully programmed by a trained |
| a feasibility study should perceive not only the short | | | | employee using on- or off-line programming methods. |
| and medium term productivity goals, but also the long | | | | The real advance in machine tool design and |
| term ones, as it is often the long term trends of | | | | monitoring systems has meant that accuracy and |
| productive capability which are the most important if | | | | repeatability of a component's dimensional |
| a company is tc amortise their costs. When highly | | | | characteristics can be confidently predicted, thus time |
| sophisticated plant such as an FMS is required, it can | | | | and again uniform work results. |
| be several years from its original conception before | | | | This repeatability has the added bonus of reducing |
| this is a reality on the shop floor, and a company's | | | | inspection, assembly and fitting costs by the virtual |
| production demands may have changed considerably | | | | elimination of re-work and scrap. Storage of the part |
| in the meantime. If, for any reason, the wrong | | | | program and its retrieval also has the effect of |
| machine has been purchased, or more likely, | | | | decreasing the lead times over the more conventional |
| something has been overlooked during the feasibility | | | | manufacturing methods still further. As a |
| study, then the "knock-on effect" of this poor | | | | consequence of this feature, the skill level is retained |
| judgement is that it will have cost the company | | | | by the company and does not leave when the |
| dearly and, at the very least, any future study will be | | | | employee moves on, or retires. Other indirect, but |
| looked on by the upper management with disdain and | | | | crucial advantages accrue through the application of |
| scepticism. | | | | CNC technology and include: the precise processing of |
| A company should plan and discuss their products | | | | changes to the part with the minimum of disruption |
| and systems to be implemented in the future with an | | | | of production, improved planning and scheduling |
| eye on the production equipment of the present. | | | | results, repeat orders are easily undertaken, plus |
| This is relevant, as any responsible production | | | | many more attractive benefits. The results of these |
| engineering company will invest in manufacturing | | | | improvements of reduced tooling requirements and |
| equipment which has reached a reliable level of | | | | inventories together with the administration benefits |
| maturity, yet at the same time allow for further | | | | can be summarised graphically by the simple profit |
| growth over a foreseeable time, and in such a | | | | and loss statement against time. Any machine tool is |
| manner, maintain and strengthen the competitiveness | | | | only making money when it is cutting material and it |
| of the enterprise. Sophisticated technologies - | | | | is important to maximise this fact by improving the |
| although they create conditions for optimum utilisation | | | | machine's utilisation over second/third shifts and by |
| of the plant - mean that capital equipment is more | | | | other non-productive machining time advances. |
| costly to purchase. Whenever high cost equipment is | | | | Positive advantages occur when a company |
| purchased it is usually the intention of a company to | | | | embraces the current CNC machining technology, but |
| maximise their financial outlay by reducing the | | | | only, hopefully, after an exhaustive feasibility study. |