High temperature of the material

In die casting in particular, the combination of high temperatures and heavy mechanical stress results in requirements that cannot be met by belt conveyors. Wire belts are usually the best solution, especially when increasing conveyor distances require the use of cleats.

The steel hinge plates, which are chain-guided on both sides, have a continuous temperature resistance of 300°C and are therefore ideal for use in cooling sections. The design of MTF steel hinge plate conveyor belts features integrated spring tensioners that ensure that the chain tension is always maintained. This allows temperature fluctuations and the resulting effects of longitudinal expansion to be optimally compensated.

Hinge plates in standard steel and stainless steel as well as many different surfaces enable solutions for a wide range of applications.

 

Wire belt conveyors

Wire belts are particularly suitable for transporting hot parts when a strong air flow is required along the conveyor line to cool components. The open structure of the wire belts allows the conveyed goods to be cooled by air in the best possible way.

This makes such wire belt conveyors particularly suitable for transporting hot hollow parts that would not be adequately ventilated on a smooth belt or steel hinge plates. Additional fans can be installed below and/or above the conveyor belt to provide additional cooling.

The wire belts can be used for the highest temperature ranges. The contact temperatures of the conveyed material can exceed 1,000°C (only for wire belts without chain guides). However, in such extreme temperatures, the specific application must be examined in each individual case. The conveyor belt dimensions, belt load, function, etc. play a major role here.

At very high temperatures, the upper belt is usually supported by a perforated stainless steel plate. At lower temperatures or if sufficient cooling is possible, plastic slide strips (high-temperature plastics if required) can also be used.

Depending on the task at hand, very hot parts can also be cooled/quenched in a liquid bath.

For this application, MTF Technik offers water conveyor belts in various designs. If the parts are heavier than water, these conveyor belts are usually designed in an angled form. For floating parts, a combination of two straight conveyor belts can also be used. This ensures that the parts are pressed under water for a definable period of time if necessary – this plays an important role in so-called conditioning conveyor belts, for example. Here, in addition to cooling, a defined water absorption of the components is also desired.

The water tank is often connected to the cooling circuit of a production machine so that the waste heat is dissipated accordingly and a constant cooling result is achieved. Whether such a solution is suitable often depends on the specific customer requirements or the material properties of the conveyed material.

 

Fans on conveyor belts

Fans are an extremely effective and energy-efficient means of cooling parts. Large quantities of parts are produced within very short cycle times, particularly in the production of mass-produced parts such as closure caps, etc. The parts are often still very warm and soft when they are removed from the mould. They must be cooled quickly so that they do not deform under their own weight in the collection container.
Fans can simply blow away the insulating "air cushion" around the parts during transport on the conveyor belt. The movement of the air creates a kind of "wind chill effect" that allows the parts to cool down much faster than in still air.In the test on the right, it can be seen that when a standard room fan is used, the part temperature drops from 105°C to 70°C (ΔT = 35°C) one minute after demoulding, while in "calm" conditions the temperature only drops by 14°C.

When these measurements are plotted on a graph, the difference is clear. A fan has a particularly strong effect immediately after demoulding. For this reason, MTF Technik usually equips conveyor belts in such cases with belt covers on which fans are mounted as close as possible to the belt inlet. This reduces the temperature of the parts and protects the belt – even with very hot parts, standard belts can often be used, as the high temperature only affects the running surface for a very short time.

The example on the right shows a conveyor belt with several fans integrated into the belt cover. The belt cover forms a kind of tunnel, which ensures that the parts are surrounded by air over a longer distance and can therefore dissipate their heat more effectively.

Similar to fans, but with controlled temperature control, additional air conditioning units or heat exchangers can reduce the cooling time of components. For this purpose, devices are connected to the conveyor belt, usually via appropriate pipes. The cold air is then blown under a belt cover. The heat exchangers can be connected to existing machine cooling circuits, for example, and thus utilise existing infrastructure.

This solution has a significant advantage over fans in that the temperature of the air blown in can be better regulated or even kept constant. Fans only draw in ambient air, which means that the cooling result also depends on the ambient temperature. This can cause problems in the summer, for example, in production halls that are not temperature-controlled. This is where air conditioning units or heat exchangers come into their own.

Separate air conditioning units (so-called spot coolers) have the disadvantage that they produce many times more waste heat than cooling power. When this is blown into the production hall, the temperature there rises accordingly and the air conditioning unit has to work harder – this creates a risk of the units icing up. It is therefore better if the waste heat can be dissipated outside the production area.

Due to the relatively high cost of air conditioning units and heat exchangers, MTF Technik generally recommends conducting trials with fans first. These are significantly less expensive and often achieve almost equivalent results. Particularly with thick-walled plastic parts, it must be taken into account that plastics are poor heat conductors. This means that the core temperature is not significantly cooled even when cooled air is applied. Careful consideration must be given to whether the investment in an air conditioning unit or heat exchanger and, above all, the ongoing energy costs are justified.