Until today approximately 500 to 600 sand coolers of the Multi-Cooler type from various manufacturers have been fitted worldwide with Michenfelder systems (e.g. Simpson, Künkel-Wagner, Webac, Hidea, Sinto and Savelli).
By linking, for the first time, the mixer-integrated moisture measuring and control system to a sand testing system located at the moulding machine, a modular system combination was established by means of which the compactability of the moulding sand is being stabilised for the first time fully automatically within close fluctuation limits directly at the moulding machine.
Since that time Michenfelder guarantees with ±2%* an accuracy of compactability control of which other manufacturers with systems at the mixer, i. e. far away from the place where it matters (the moulding plant ) can only dream.
In daily foundry practice values are achieved which, with ±0.8-1.6%*, are even far better.
*1st Standard deviation
When developing the computer-controlled moisture measuring and control systems our technicians discovered an interesting side effect. By means of continuous monitoring of moisture value development in the mixers during the full mixing process of the individual batch – from material entry to discharge – it became possible for the first time to produce a “preparation curve” for each individual batch.
By means of monitoring the mixing dynamics, as a standard function of the MICOMP system series for batch mixers, it became now possible to evaluate the performance of mixers (inclusive of their capability of homogeneous mixing of sand, additives and water during period X). The comparison of reference curves with current as-is curves is used by the user today in daily routine as an indicator, for instance for defective, offset or worn mixing tools, or other changes in the preparation process, which have to be investigated. Since that time the mixer-integrated moisture measuring and control systems by Michenfelder deliver as a standard significantly more than just a correctly and reliably controlled output moisture level.
Till that time fluid-bed coolers were operated with straight temperature controlled water addition. From this typical problems arose, for instance the classic “Monday problem” (cold sand – no water addition). New findings about partly grave effects of lacking or insufficient moisture in the used sand on all subsequent processing stages and the development of the sand quality during transport to the moulding machine called for action. But lacking water was not the only problem. An additional negative effect resulted from the loss of fine dust parts in the dry sand due to cooler´s exhaust air, changing fundamentally the character of the sand. Consequently, Michenfelder integrated a fully automatic moisture measuring and control system by means of which it was possible to ensure in each production stage a precise output moisture level when discharged from the cooler.
The comprehensive approach for monitoring and controlling moulding sand quality is put into practice. From individual systems used separately until that time in sand plants for moisture measurement and control, mechanical sand testing and process data monitoring an higher level networked system of interlinked and inter-reacting modules for centralised control and monitoring of moulding sand quality, from shakeout grid to moulding machine, called FoMaSys, was created.
The MOULDING SAND MATRIX as an extension of process control system MiPro generates automatically requests for taking suitable counter measures in the sand preparation process when a previously defined quality window is left. In this connection the user benefits greatly that the corresponding “adjusting point” is clearly pointed out to him which he must use in the process. The economical advantage for the foundry is the time gained by means of the valuable findings about process interactions presented in real time and the action requests resulting from this.
In a compact automatic testing unit ONLINE-SANDLAB for conveyor belt installation, an advancement of the VEDIMAT, there are several devices combined for the determination of a so far unequalled multitude of quality-relevant variables for sand preparation. For the first time, also permeability testing has been relocated away from the laboratory into the sand preparation process. This relocation allows action and reaction based on an enormously enlarged and directly at the moulding planted generated data basis in real time.
The demands on fully automatic measuring and control systems in the sand preparation process will increase in response to the extent specialist knowledge regarding the details of moulding sand preparation becomes lost. The industry is just experiencing this process. There is a tendency of process-related know-how to deteriorate in the foundries as well as at the plant constructors. Old hands, having a feeling with regard to sand preparation, who can judge moulding sand quality by how it feels in the hand, will no longer be available. Due to the high degree of automation a different type of employees develops. This is characterised by a number of responsible highly skilled specialists, mainly engineers and technicians with a mechanical, process or electrical engineering background, a few plant operators and the servicing personnel. These are normally in a position to run the plant and machinery without any problems and to keep the processes running. This cannot be said without reservation with respect to controlling sand quality. In spite of good mechanical design of sand preparation plant, there is still too much sand related costly castings scrap. In addition one becomes more and more aware that the sluggishness of only lab-supported sand quality control does no longer meet today’s requirements. It can no longer correspond to current changes of cycle times and production technology of vital importance for the foundries appropriately and will in future perform a support function only. Strict control of sand quality directly at the moulding machine is an important factor for low foundry scrap. The system designs of the future will have to comply with this. This includes optimally in the sand reconditioning process between the knock-out grid and the moulding plant integrated and interlinked measuring, testing and control systems, providing in real time information about the sand condition at the moulding machine and issuing – in order not to lose any time – targeted action requests for taking suitable counter measures (or in future act independently with automated solids correction) if quality-relevant parameters are leaving a prescribed corridor. Already today, the modular Moulding Sand Management System FoMaSys is contributing to this aim substantially. What we have achieved until today will not satisfy us in the future, we always know what can be improved and secondly we look ahead and envisage the challenges of the future. But, of course, we already are having several new ideas …