New feeding box increases capacity and quality

Apart from the development and production of concrete block making machines Sedna Technologies GmbH – in short “SednaTec” – dedicates itself intensively to the world-wide support of concrete block making machines and equipments applied in the manufacturing process. In cooperation with manufacturers again and again the occasion comes up to modernize existing plants quite often with relatively low effort and expenses and increase their capacity in this way. Luiki located in Leoben (Austria) also charged SednaTec with the modernization of a plant.

Luiki is a successful family-run company with several production premises. The company considers its 60 years history as a commitment for the future. Right from the beginning, one principle of their company philosophy was to manufacture always an excellent concrete quality. For Luiki this basic principle has top priority in future, too.
Therefore, the idea of enhancing the product quality and raising the efficiency of the production has been the initial point for modernizing the board-based block machine. The definition of the project provided for a better filling of the concrete product molds. Before starting the project, the current manufacturing processes had been analyzed comprehensively. In this regard, the concrete distribution in the mold throughout the entire mold section played an important role. The uniform distribution was considered to be the benchmark for the goal to reach and the implementation of the same.
SednaTec had already developed new feeding boxes with hydraulic driven filling grid for mobile and stationary concrete block making machines. In this respect, great importance was attached to achieve better filling and more ease of maintenance. Design and development of the feeding box technique was elaborated in cooperation with the manufacturer of the block making industry. The new model has well proven itself in practice. This new kind of feeding box should as well be applied at the manufacturer Luiki. In the process, great importance was attached to the fact that all work movements from one cycle to the next are carried out precisely in the same way and are reproducible.

Hydraulic pressure sensors
An important task within the scope of the modernization was the uniform filling of the feeding box. Beside a uniform distribution of concrete in the feeding box, this above all means to achieve that the concrete quantity in the feeding box is almost ever the same. The system is controlled by hydraulic pressure sensors. In this respect, attention is paid to the minimum and maximum filling level. If any of the limit values has been under-run or exceeded, a message is given on the computer and the respective closing of the hopper is automatically controlled in such a manner that the intended filling level in the feeding box is achieved.

Frequency converter for the table vibrator
In order to achieve a uniform filling of the mold, it should be possible to regulate the intensity of each vibration during the filling process differently in the various sections. Thus, it should be possible to have a more intensive vibration in sections that are not that easy to fill than in sections that are easy to fill.
The design of the vibrating table provides a very good possibility for realizing those requirement. The parameters are versatile and thus allow, for example, following setting of the machine as a final result:
» consistently distributed vibration throughout the entire vibrating table
» more intensive vibration in the front section than in the rear section of the vibrating table
» more intensive vibration in the center section than in the outer sections of the vibrating table.

Extension of the control and operating software
The modified filling procedure was integrated in the existing S7 control system. In principle, SednaTec integrates parts of a program in such a way that the newly added options may be selected alternatively. This means that if an option is not selected, the machine is manufacturing according to the usual setting (i.e. setting of the machine before the modernization). The machine operator is enabled to apply all parameters via the PC-based operator panel. These parameters are recorded in a formulation and are activated automatically when changing the program.
It is possible to enter limit values for all parameters which lead to an automatic correction of the production process, within which changes can be realized. Furthermore, the possible degree of a corrective action can be defined. These possibilities, on the one hand, lead to the fact that an automatic correction operates within the predefined limits and “does not go off course”. On the other hand, it is also possible in this way to preset how fast the corrective target is to be attained.
All new processes are visualized on the computer, which applies in particular to a new illustration of the vibration control.

Conclusion
Before starting with the project work, specified values had been defined according to which the defined project was assessed. The weight of the blocks and the weight tolerances along the entire board section should serve as a direct indicator after retrofitting. For this purpose, the nominal value was measured with the actual value of the block before as well as after the modification. In this way it was possible to prove a uniform filling throughout the board.
The success was effectively confirmed by the following manufacturing results: Now, a better filling of the mold is achieved. In particular, in case of molds that are not that easy to fill – such as, for example, molds with quite different shapes – this outcome becomes noticeable.
An additional result, which may be mentioned here, is the fact that in the factory of Luiki the productivity in the process of manufacturing of  blasted paving stones has been increased due to a more uniform filling.
In cooperation with SednaTec Luiki has realized a modification of its board-based block machine aiming to achieve a better filling of the mold. For this purpose, partly new and in some respect perhaps even unusual solutions have been taken into account and were realized. These measures have considerably contributed to an increase in quality and capacity.
Many board-based block machines can be retrofitted by the new feeding box type K and thus help a large number of manufacturers to optimize quality and quantity.

Rüdiger Herr, Siegen