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What Doesn't Fit Will be Made to Fit

The demands made on screening technology solutions that are integrated into production systems can be very varied. In addition to greater economic efficiency and performance capacity, the conditions which exist on-site when constructing and completing the machines need to be considered. The example of a current project being carried out by J. Engelsmann AG screening-technology experts shows how elaborate adaptations and operating costs can be saved through machine solutions when they are customized to the operative needs.

The client, a global full-service provider for the surface-processing of metals and other materials, produces machines and processing technologies for vibratory finishing, among other things. This also includes processing materials such as ceramic grinding media, so-called vibratory finishing media that are produced in numerous different qualities and shapes, and are used in particular in wet machining. Grinding media bound with ceramic are characterized by their high grinding performance at high grinding pressure. They also have long service lives and can be produced in a wide variety of forms.

The high quality of the raw-materials is also decisive for the production of the grinding media. The granulation determines the appearance of the surface following grinding so that the processing of oversized or undersized grains which might possibly be present, have a direct influence on the grinding quality of the media. As a consequence of this, an integrated separation of oversized or undersized grains by means of machine screening is carried out during the production process of the ceramic granulate. This not only involves the percentage of grains outside the wanted grain spectrum being screened out, but also the bound granulate so-called multiples. Only the so-called good grain can be used for manufacturing the grinding media. The screened out undersized grains are fed back into the production process, the oversized grains on the other hand are not used any further.

The specific demands of operation determine the layout of the machines

For the separation of oversized or undersized grains, a vibration screening machine that was integrated into the production facility was used up until now, whose grade of screening – the so-called degree of selectivity – no longer met the increased quality demands of the vibratory finishing media manufacturer. A further reason to replace the machine was the long downtimes that were required in order to adapt the screening machine to the different batches of product. The purchase of two new machines involved the condition that no extensive retrofitting or adaptation work would be required on the inlets which exist on the machine in order to be able to integrate the upstream and downstream system components.

Following an initial consultation meeting with Engelsmann, the next step in the problem-solving process was to go to the technical college to test the screening ability of the granulate in order to determine the required throughput performance and to convince the customer that the selected machine solution will then function without any problems later in actual operation. On the basis of the test results, the Engelsmann design engineers decided on the use of a vibration screening machine of the type JEL VibSpeed, that can be used as protection, control or classification screen for free-flowing, dry bulk goods due to its high grade of screening (degree of selectivity of up to 99%) and adaptability in all areas of the producing industry. In addition to the higher grade of screening for the optimization of the product quality aimed for, a central requirement on the part of the customer was the minimization of the downtimes by means of a simple and fast retrofitting.

Modular design: Adaptability to the screening product and location

As a result of the fact that the various granulate specifications on the machine are screened, the screening machine used must be easily accessible and easy to disassemble because the screen inserts with different mesh sizes will need to be changed for each changing product batch. As a consequence of the large variety of products to be screened, the frequent changing of the screens results in downtimes that can be shortened through simpler machine handling. The flexibility and the simpler handling of the JEL VibSpeed are provided in particular with the hinged cover of the machine. This saves the user a very significant amount of time and effort when it comes to assembly and cleaning. Thanks to the quick-changeover version, the screen inserts can be removed from the VibSpeed model by lifting them upwards in just a few steps once the cover has been removed and the clamping device on the front has been loosened. The open access to the screen inserts in addition to their simple disassembly makes it possible to be able to quickly clean the product chamber in a way in which it can be ensured that absolutely no residues remain. By means of the altered stimulation of the screen mesh, the conveying speed and the trajectory parabola onto the granulate product to be screened can be set. The direction of the vibration is changed in this case by changing the arrangement of the vibration motors. The set-up range can be changed in intervals of 15°. The vibrators of the JEL VibSpeed screening machine arranged along the screening direction are connected to each other rigidly; synchronies themselves independently when in operation and so ensure a smooth and quiet machine operation. The inclination of the screening deck can also be set (2° to 5°) and can be adapted to the requirements of the respective screening product. An adjustable inclination of the screening deck influences the product's flowing speed and, as a consequence, the dwell times on the screen mesh.

For the screening out of undersized grains and oversized grains, the VibSpeed machines that have been ordered in the double-decker version were fitted with two screening decks and each with a screen insert with a surface area measuring 0.5 m² in total. The screening process goes from coarse to fine, where the portion of the oversized grains of the granulate is separated on the upper screen deck and the portion of the undersized grains that are too fine on the lower second deck. The mesh width of the screen meshes are either 5 or 1 mm. They are permanently cleaned by means of a ball-cleaning system installed underneath the mesh on a corrugated-wire mesh, in which case impact-rubber balls bounce against the mesh as a result of the vibration of the machine and keep the mesh permeable during the screening process.

The last challenge remaining is the adaptation to the individual on-site conditions. In order to be able to use the inlets which are present on the front of the machine without expensive retrofitting being required, the diameter and the positions of the inlet sockets and the coarse-goods outlet were customized to meet the mechanical conditions of the system. In order to reduce the downtimes, both screening machines are to be equipped with a lockable undercarriage on wheels, with which they can be quickly and easily rolled out of the system.

Mobile machine application thanks to undercarriage and on-board control

The undercarriage allows the machine to be easily moved from one location to another, because the screening machines are also needed in other production areas for protective screening. In order to allow for their mobile application, both machines are each equipped with a ready-to-mount control, which has an emergency-off function and with which the vibrators are synchronized. If one of the vibrators malfunctions, the machine turns off automatically. The screening machines can be quickly and simply put into operation by means of its power connection.

The Engelsmann screening machines supplied have the CE marking and have confirmed the results of the tests carried out in the technical college in practical operations; this allowed the client to increase the grade of screening by 24% and the product quality of the ceramic granulate could also be improved as planned. The downtimes experienced up to now could also be reduced by almost 40% through the use of new VibSpeed vibration screening machines and the productivity of the entire system significantly increased in conjunction with improved economic-efficiency.

The models of the JEL VibSpeed series are available with a maximum screening surface of 7.5 m². In the case of the single-deck version, the bandwidth is 0.25 to 3.75 m², and in the case of the double-decker version 0.50 to 7.5 m². Depending on the necessity, the JEL VibSpeed with stationary or mobile undercarriage can be supplied in 10 size variants.