Efficient Distribution and Buffering of Material

Bunker conveyor belts are suitable for the short-term storage of bulk goods, as well. These are usually belt conveyors or steel hinged plate conveyors that are equipped with a large feed hopper. The hopper volume is then designed according to the part geometry and task. Hoppers with a volume of up to approx. 1.5m3 are not uncommon.

Such dosing conveyor belts are primarily used to feed material into subsequent processes. They are often used, for example, to fill vibrating bowls on assembly systems or to feed separating drums in a centralised separating task.

As a rule, either speed-controlled or intermittent drives are used to enable metered feeding. Depending on the task, feeding systems in combination with fill level sensors can also be realised in a relatively simple way.

When designing the hoppers for the hopper conveyors, careful attention must be paid to the part geometry in order to avoid any jamming or bridging processes.

The basic version of the sliding buffer consists of a stainless steel sheet base body with an integrated pneumatic sliding mechanism. Two to usually a maximum of three empty containers are placed on the base body, which are then pushed forward by means of a sliding arm in order to realise a container change.

In the simplest version, no additional control system is required for this; instead, a 24V signal can be sent from an existing machine control system to a spring-loaded pneumatic valve, for example, which only needs to be activated for as long as is necessary to move a container. However, for more complex tasks with more than two containers or intermediate positions - e.g. to avoid dumping cones - a more complex control system must be used.

The main advantage of the sliding buffers is their minimal height. The containers stand virtually directly on the floor, supported only by the sheet metal base, which is only a few millimetres higher. This makes these buffers particularly suitable for tasks where parts are fed in via low chutes or machine chutes, for example.

The sliding buffers are extremely low-maintenance, simple and comparatively inexpensive. They are the ideal solution for realising low filling heights and require little space.

Multi-level conveyor belts are generally used as a multi-layer storage area for individual parts. In most cases, this involves short-term buffering of small load carriers at a production plant, e.g. where components are deposited by a robot and transported out of a safety fence. The conveyor belts are usually installed offset one above the other at the belt infeed in order to provide storage areas for crates at all levels, which can be reached from above by a robot.

These conveyor belts often serve to decouple the production process from a manual process, i.e. an operator removes the components from the delivery side. For example, a level can be completely filled over a longer period of time and the operator then clears the conveyor belt in correspondingly longer cycles.

The conveyor belts are customised in terms of length, width and number of levels depending on the task and desired buffer period. Depending on the existing control technology on the production system, the multi-level conveyor belts can be equipped with different electrical interfaces.

The advantage of the multi-level conveyor belts is that the components can be deposited in a defined manner and transported as piece goods. This is gentle on parts, prevents damage and can also be used very well for cooling processes, for example (also with additional fans or cooling equipment).

If production machines are positioned next to each other in parallel, for example, there is often very little space between the machines in terms of width for a buffer solution. In addition, there is usually the requirement that the machine must be accessible for set-up processes. In these cases, MTF Technik conveyor belts can often be used as linear buffers.

Several containers (cartons, boxes etc.) are placed on a conveyor belt, which are then moved to the respective filling position in a controlled manner. The cleats on the conveyor belt ensure that there is always a small gap between the containers, which can be easily monitored by a sensor. This means that each container can be clearly positioned at the filling position.

In more complex systems, pneumatic separating stations can also be used as an option in order to be able to move containers to the accumulation position. This is particularly important if, for example, different container sizes are used and fixed cleat compartments are therefore not suitable or containers are to be pre-accelerated into a protective fence to the filling position.

The linear buffers can be set up very flat so that feeding situations from low chutes are also possible. The disadvantage of these systems is the relatively large amount of space required, as the empty containers must first be stored and then buffered as full containers after the filling process. With a buffer solution for three containers, there must be space for at least five containers in total (the last container then remains in the filling position and the two already filled containers are pre-buffered in the two free spaces).

Optionally, the linear buffers can also be designed in two parts, i.e. the empty containers are fed to the filling station via a conveyor belt and the filled containers are removed via a roller conveyor. This is useful if, for example, filling takes place inside a safety fence or if, for space reasons, the filled containers can only be removed at the front discharge position. In this case, the combination with a roller conveyor offers the advantage that the removal of the filled containers can be realised independently of the feeding of the empty containers.

As the linear buffers can be designed to be mobile, they can be easily removed from the production machine if necessary, so that, for example, mould changes or similar are possible.

Förderbänder mit Querschiebevorrichtung kommen zum Einsatz, wenn die Aufgabe leerer Behälter und die Abnahme gefüllter Behälter an einer Stelle erfolgen soll.

Bei dieser Pufferanlage werden die Behälter in einem U-förmigen Ablauf transportiert, d.h. der Bediener setzt leere Behälter auf einem Förderband auf. Diese werden vorgefahren und am Bandende an einem Anschlag auf dem Gurt aufgestaut. In der Anschlagsposition erfolgt dann üblicherweise die Befüllung des Behälters. Ist der Behälter gefüllt, schiebt ein pneumatischer Arm den Behälter im 90°-Winkel zum Förderband auf eine parallel zum Förderband verlaufende Rollenbahn, die gegen die Förderrichtung des Zuführbandes geneigt ist. Dadurch laufen die gefüllten Behälter nach dem Querschiebeprozess auf der Rollenbahn zurück in Richtung Aufgabeposition.

Dieser Ablauf empfiehlt sich insbesondere, wenn die Befüllung z.B. durch ein Robotersystem o.ä. erfolgt, welches in einem Schutzzaun angebracht ist. Dabei befindet sich der Bediener außerhalb des Schutzzauns und kann immer leere Behälter nachschieben und auf der Rollenbahn im gleichen Zyklus gefüllte Behälter entnehmen, ohne in den Zyklus der Produktionsmaschine eingreifen zu müssen.

Nachteilig an der Kombination aus Förderband und Rollenbahn ist dabei die schlechtere Flächennutzung, die maximal 50% beträgt, da das Förderband mit leeren Behältern gefüllt wird und der gleiche Platz als Leerplatz für die später gefüllten Behälter auf der Rollenbahn vorgesehen werden muss. Um diesen Nachteil zu beheben, kann statt der Rollenbahn ein zweites Förderband mit einem weiteren Querschieber eingesetzt werden. Hier ist es lediglich erforderlich, dass ein Behälterplatz leer gelassen wird, um den ersten Querschiebevorgang zu ermöglichen. Wenn die Förderbänder z.B. Platz für jeweils zwei Behälter bieten, so muss ein Platz freigelassen werden, d.h. 75% Nutzungsgrad. Bei Platz für jeweils 10 Behälter auf einem Förderband, muss ebenfalls nur ein Platz freigelassen werden, d.h. 19 von 20 Plätzen und somit 95% der Förderbandfläche können genutzt werden. Dabei können die Behälter einen kompletten Umlauf fahren, d.h. sie kommen im befüllten Zustand dort wieder an, wo sie als Leerbehälter aufgegeben worden sind.

As with the concept of the linear conveyor belt, containers can also be filled using a conveyor belt with multiple outfeeds. In this case, a conveyor belt is mounted above the containers to be filled. The side guide of the conveyor belt is then removed at each container position and a diverter is installed there instead, which diverts the flow from the conveyor belt to the side. Once all the diverters are closed, they serve as side guides and the goods are mounted to the end of the conveyor belt.

In this way, virtually any number of discharge points can be defined, which can be either very close together or far apart. The solution can therefore be used for space-saving applications in which the containers to be filled can be placed directly next to each other. However, this concept can also be used to supply larger containers or different storage bunkers to automatic assembly machines, for example.

As with the linear conveyor belts, only the goods are transported here, not the containers. The system can therefore be used flexibly for different container types.

Most buffer systems require the use of a control system, especially if, for example, a certain quantity of components is to be stored and transported in a container.

Depending on the complexity of the systems and the desired functionalities, the buffer systems can be controlled via existing control systems on production machines, etc. This would be the simplest and cheapest case. This would be the simplest and most favourable case.

In most cases, however, the buffer system is controlled separately, which is then connected to the production system and possibly other transport systems, etc. via an interface. As a rule, the following basic functions are covered:

1. Counting Function, i.e. a container change should take place after a certain number of components or machine cycles. For this purpose, a corresponding target quantity per container is entered in the control system. The counting function usually also includes an input option for a cavity number, i.e. a multiplier for how many parts are produced per machine cycle or per signal.

2. Time Function - as alternative to counting can be useful in certain cases, i.e. the container change takes place after a certain time. This function is required, for example, if there is no signalling evaluation of the production quantity or no connection to the production machine.

3. Follow-Up Time, as there is always is a certain distance between the place where the product is created (e.g. in the mould of a machine) and the container to be filled. This means that the counting pulse takes place before the product arrives in the desired container. If, for example, the component lands on a conveyor belt after the production process and is only then transported into the container, the time required for the transfer must be determined. Once the target quantity has been reached, the conveyor belt must therefore first run continuously for this time until the counted part has been transported into the container.

Other possible control functions include counting the components using a weighing system, which is connected to the control system depending on the product and the required accuracy. Reference weights are stored for each item and a desired target number of items or a target weight per container is requested.

There are also functionalities in which different components are entered with their corresponding parameters (keyword: recipe management). This simplifies operation when different, recurring items are to be produced and buffered.

Depending on customer requirements, various displays, connectors, interfaces, cable lengths, control cabinet designs, signal lights, acoustic elements, operating elements, etc. can be integrated.

Do you have any further questions about our buffer systems? We are available for you at any time via telephone on +49 2261 9431-0 or e-mail or simply use our contact form.