The machining process is lubricated and cooled, and the workpiece is cleaned of chips. After processing, the emulsion remaining on the workpiece evaporates to a large extent, so that time-consuming cleaning of the workpieces is often unnecessary.
However, the water contained in the emulsion leads to a cooling effect of the machining area during processing by evaporation, especially if the emulsion is atomized by machining. The temperature can drop by 10°C. This has a significant impact on the axis geometry of the machine tool, because the low temperature in the machining area affects the machine structure, cooling it down and causing significant thermally induced deformations. Depending on the size of the machine, the deviations on the workpiece can be quite significant and amount to several hundredths of a millimetre. Machining tasks with very tight tolerances cannot be carried out reliably. Especially in 5-axis machining, there can be a larger offset if a workpiece is machined in different axis positions and the zero point does not fit in relation to the 4th and 5th axes.
Temperature-stable machining area during machining with emulsion
Roeders has therefore dealt intensively with the question of how, despite the cooling effect caused by evaporation of the emulsion, the machine tool can be kept geometrically stable when emulsion is used. In doing so, Roeders was able to build on the extensive previous development of PRECITEMP®, with which Roeders succeeded in keeping the RPT milling and grinding machines at very high machining accuracy even when the ambient temperature at the location of the machine fluctuates by +/- 3°C.
Despite fluctuating ambient temperatures at the installation site, the RPT machine maintains maximum precision with an almost constant zero point
Similar to PRECITEMP® for RPT machines, which are operated with minimum quantity lubrication or oil surge flushing, the concept of PRECITEMP® E for RPT machines with emulsion is not based on a single element, but on a combination of several measures. Basically, as always with Roeders machines, all heat sources such as motors etc. are thermally insulated by active temperature control, so that they cannot influence the geometry of the machine. In addition, the machine body is kept at a very constant temperature with numerous temperature control circuits. The air in the cover above the machine portal is tempered with high precision using air temperature control units. In addition, it has been possible to keep the temperature in the machining area very constant, even if emulsion is not used continuously, but the machine is left standing longer in between or machining is carried out without emulsion. The results are impressive. Even if the ambient temperature at the installation site of the machine fluctuates by +/- 3°C, it still works with μm accuracy. As a result, machining can be carried out reliably precise, which brings great advantages for productivity, especially in automated systems. Interim checks of workpiece accuracy during machining are not necessary.
On the contrary, in many applications, quality control can even be carried out directly in the machine. For this, Roeders has integrated Renishaw’s Productivity+TM software and HEXAGON’s INSPECT software into the Roeders NC control system, which can be used to inspect geometries such as roundness, distances, parallelisms, flatness, etc., just like on a coordinate measuring machine. The measuring accuracy of the machine tool can be checked at any time with the help of a gauge similar to a quality control on a coordinate measuring machine, except that no technician from Roeders has to travel for this, but the operator can do it himself. The measurement accuracy in the μm range was proven in cooperation with the Leibniz University of Hannover. This can save the detour via the measuring room in numerous applications. The measurement protocols are comparable to those of coordinate measuring machines and are stored in the NC control system or directly on the server. In automated systems, after machining and measuring in the machine, not only finished workpieces, but also machined and quality-controlled workpieces are stored in the shelf system of the automation, which can then be used directly in assembly. The emulsion dries away so completely that cleaning is usually not necessary.
Quality control directly in the machine: Measurement of a workpiece after machining
In Roeders’ own blow mould shop, many thousand blow moulds made of aluminium are machined with emulsion every year. Quality control in the machine directly after machining has been a proven practice for some time now and was an important step in keeping up with the cost pressure from competitors from countries such as Turkey, India or China. The measuring room has been shut down.
Blow mould produced and measured from the raw block on the machine with emulsion in the Roeders blow mould shop
But PRECITEMP® E was developed for the customers of the Roeders machines searching precision. In addition to aluminium, PRECITEMP® E can be used to significantly improve productivity when machining ceramics, glass, stainless steel, copper, e.g. in high-precision electrode production and in other applications, thanks to reliably high precision, including measurement protocols for quality control.
Measurement protocol with clear tolerance information, measurement of the workpiece directly in the milling machine
Incidentally, the ease of use of Roeders machines has also been improved when using emulsion. High rpm of the tool often lead to strong atomization and fogging in the machining area. It can take a few seconds for the emulsion mist to be removed from the machining area by the oil mist extraction system after processing, which is very annoying if the operator wants to open the door quickly. For this reason, the Roeders RPT machines with emulsion now have a flap in the cabin. This opens and allows ambient air to flow into the machine’s machining area, while at the same time the extraction system briefly switches to turbo mode. This quickly ensures a clear view before the operator opens the door.
The new concept for high-precision machining with emulsion will be presented for the first time at the AMB in Stuttgart, hall 7, booth C41.
