As everyone is well aware, in uncertain economic times, the manufacturing of mechanical parts industry in developed countries needs to redouble its efforts in striving for productivity gains in order to ensure it maintains its competitive edge internationally. Following several years of optimisation in workshops, a very valid question would be: where could productivity gains still be found?
If we were to examine the process for the manufacturing of mechanical parts, the main achievable gains would be in the machining process itself, the handling that occurs between the successive steps in the process and the control thereof.
Historically, the instinct was to invest in ultra-rapid machine tools as the added value come from machining the part. Machine manufacturers have realised this as for years they have been competing to gain shorter and shorter machining times by designing machines that are ever faster and more versatile.
Control still relegated to the background
In terms of handling, today many different solutions exist ranging from robots to palletising systems that allow for a time saving between the manufacturing sequences. Progress made over the past few years has also allowed for undeniable gains to be achieved.
However, it is interesting to note that control remains relegated to the background. It is still too often considered as an operation whose added value is barely justifiable in terms of investment, but one that is essential nonetheless. In all likelihood, the explanation can be found in the widening gap between improving the productivity of machine tools and that of control equipment. In fact, the performance of machine tools such as machining speeds, the number of axes, tool changes and digital controls has steadily progressed, while external measuring equipment (of a multidimensional or comparator type) and three-dimensional measuring machines remain more or less limited to the same dynamic performance. The consequences of this are clear: where only a few seconds are required to manufacture a mechanical part, a few minutes or even hours are required before the outcome of the control process can be obtained!
Production bottlenecks
Faced with this observation, we can deduce that control therefore naturally becomes a bottleneck which may call into question the entire investment and expected productivity gains. In fact, owning the fastest machine tool in the world is of no benefit to its owner if it needs to be stopped too frequently while awaiting control results. Parallels could be drawn here with the economic model of “low cost” airline companies. The common theme characterising these companies is the following: “the more my plane flies, the more profitable it is, and the more added value I can pass on to my customers”. They are not looking to buy faster planes but rather to minimise the plane’s stationary time on the tarmac by optimising boarding time (reducing the number and size of luggage pieces, following a passenger boarding order according to seat number, etc.), disembarkation (opening of the front and rear doors) and even pre-cleaning of the plane during the flight. The strategy underpinning mechanical workshops must therefore follow the same logic: “the more machining my machine tool does, the more profitable it is, and the more added value I can create for my customers”. It therefore becomes a strategic issue to reduce the time required by all the steps iterated by the tool machine, including the control step. But how can the ideal solution be found allowing for a reduction in waiting time and therefore machine stoppage?
Two types of control equipment
Two types of control equipment exist for measuring dimensional and geometrical values: “external measuring equipment” (of a multidimensional or comparator type) and coordinate measuring machines (CMM). As is often the case, the advantages offered by one type are the drawbacks of the other. In fact, external measurement assemblies have the advantage of being simple to use (compared to benchmarking measurement systems), they are robust and in particular provide operators with measurement results very quickly. However, this equipment is relatively limited in terms of providing a solution for complex control (geometric dimensions) especially on materials presenting little flexibility as they are often dedicated to a specific part type. In contrast, coordinate measuring machines (CMM) precisely offer this flexibility and computational power. However, even though certain improvements have been made, they remain slow and for the most part ill-suited to the workshop environment.
A third option
However, a third option exists offering a combination of the abovementioned advantages which allows one to get nearer to optimal control. In fact, for many years ESPI has been developing and marketing its Scanflash equipment which could be referred to as “high-speed measurement centres”. The underlying principle is simple: it concerns a 3D comparison with a benchmark. This equipment is able to calculate the full range of dimensional and geometrical measurements for a particular part, in a single, high-speed and ultra-high-precision operation, with the device lying at the foot of the machine tool. The immediate availability of measurement results coupled with a Tool’sDriver CN correctors module offers digital regulation and handling of the machine tools in real time, and this is where the true added value lies. In fact, the reactivity of this technical solution referred to as DPC (Dynamic Process Control) transforms traditional control into a true driving force in the manufacturing process, while also offering significant gains in terms of profitability for a particular set of machine tools. Initial feedback from Scanflash users seems to indicate remarkable performance for medium and large series productions, with more « chip times », series change times divided by ten and more good parts leading to a reduced amount of adjustment wastage as the second part is already good. There is also greater accuracy without dispersion by machining on the targets in a centred manner, greater flexibility allowing for production in piece-by-piece mode by reducing the size of economic order quantities, which ensures greater cash flow by sharply reducing the FOR (Financial Operating Requirement) with a decrease in stock, while greater savings are realised in direct and indirect costs through reduced operator times, fewer control operations, fewer square meters of occupied space, and finally, more robustness across the machining processes with support provided to regulators.
A matter of survival
In conclusion, in today’s world, the quest for gains in productivity remains a matter of survival for the engineering industries in developed countries. However, in terms of the production of mechanical parts, these gains are not to be found in the places you’d traditionally think they’d be found, while solutions such as Scanflash DPC/Tool’sDriver offer new perspectives by ensuring control moves more towards a driver level, allowing it to become a true value-added step. So now we have a new paradigm: “Demand more from your machine tools, no longer think “control”, think “driver”!