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Less of a grind

Less of a grind

Coffee is big business. It’s the most popular drink worldwide with around two billion cups consumed every day, while in the UK we drink around 70 million cups per day. In the UK we spend around £950 million on coffee and while around three quarters of all UK adults drink instant coffee, around 50% drink fresh ,or ground coffee, and this ‘premium’ sector is one of one of the fastest growing sectors of the market. Whilst there are many new coffee products available which aim to provide a premium cup of coffee more quickly, such as special powder blends and pods, for the purists it has to be real coffee beans.  

Among the key challenges facing the design of modern coffee grinders is grinding beans at the required rate, as reliably and as quietly as possible. Transmission and control specialist Rotalink has helped a premium coffee machine manufacturer based in Switzerland, by providing motors and gearboxes which have proven to be a very effective solution for their machines. 

Rotalink’s geared DC motors are ideal for this type of application for a number of reasons. First, the most effective way of reducing the noise emanating from a gearbox is to reduce the speed of the motor driving it. Furthermore, the slower the motor runs the longer it will last. At the same time, however, a motor of a given size will be more powerful the faster it runs. A trade-off must therefore be considered: should the required power be achieved by using a smaller, noisier, lower-cost and shorter life motor, or a larger, quieter, higher cost, longer-life motor? The answer will obviously vary depending on the objectives and principles of each grinding machine manufacturer. However, Rotalink has developed a range of gearboxes which are compatible with an even wider range of motors, supported by experienced engineers who can help to find the ideal combination. 

The defining feature of Rotalink’s range of gear motors is the use of gears made from engineering polymers. Whilst this is common practice in sub-10W gearboxes, the company continues to exploit the benefits of these materials in gearboxes required for coffee grinding machines. The cost advantages of polymers over metals are well established. What is more likely to be overlooked is that the self-lubricating properties of polymer will extend the life of the gearbox well beyond that of a metal equivalent which is prone to wear once grease inevitably migrates away from gear meshes. 

There are, however, other specific benefits by using these types of gearmotors in coffee grinding applications. For example, friction clutches are typically used when a gearbox can be suddenly jammed when a stray stone in a batch of coffee beans gets through. In some cases this will break the gears in a gearbox, or even the grinder blade itself, before electronic current limiting devices begin to react. A friction clutch on the output stage of a gearbox will merely start to slip which protects the gears and increases the current draw of the motor, enabling the jam to be detected. Furthermore, controlling the speed of a grinder allows powder to be ground at a precise rate, maximising the yield of a batch of beans. Rotalink’s incremental encoders are ideal for this purpose because they use capacitive sensing which makes them low cost, durable and compact compared to alternatives. 

Rotalink’s flexible, customer-focused production methods means that customised output shafts can be offered for relatively low order volumes, without impacting on lead times. This ability to customise makes it easier to incorporate Rotalink products into existing designs and was a key element in the project undertaken by the premium coffee machine manufacturer in Switzerland. The result is a quiet, compact grinder that utilises a novel mounting system on the grinding head that also minimises assembly time.

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