Massive geared motors support largest-ever toothpaste mixers

In the hygiene and personal care industries, there is demand for ever-larger batch sizes for products such as toothpaste, as well as for a larger range of variants to be produced at each site. At the same time, many manufacturers are interested in concentrating production capacities in just a few places. Modern plants must therefore be capable of producing large volumes while at the same time providing maximum versatility. With this task in mind, Ekato Systems from Schopfheim, in the southern reaches of the Black Forest in Germany, has recently constructed a new plant for the production of toothpaste.

Ekato is a manufacturer of customised industrial agitators, and has scaled up the largest model from its UNIMIX line to more than double the size, thereby implementing the largest discontinuous toothpaste production system in the world.

The maximum capacity of toothpaste production plants is typically between 4000 and 5000 litres, with outputs of approximately 2000 to 3000 litres hourly. Continuous or batch production is possible. Continuous systems enable high throughput but are not very versatile with regard to product changes; since different ingredients sometimes require their own dispensing and blending technology, recipe changes often bring about conversions and readjustments. Moreover, toothpaste cannot easily be reworked when it is not sufficiently homogeneous. The biggest challenge with continuous plants is ensuring the uniform dispersion of active ingredients such as sodium fluoride, even after changes to the dispensing systems. On the other hand, the production rate of existing discontinuous plants cannot be significantly increased without major modifications in plant equipment. In order to meet the demands of a toothpaste manufacturer, Ekato therefore had to construct larger plants.

Ekato’s new plant has two mixers, each with 10,000 litres effective volume, more than tripling production to produce 6000 to 11,000 kg of toothpaste per hour, depending on the product concentration.

Toothpaste production systems basically consist of an evacuable vessel with an agitator, a homogeniser and various dispensing systems for the introduction of ingredients into the process. Liquid ingredients are either measured and then vacuum inserted into the vessel or dispensed by gravimetric methods. Powders and thickeners to increase viscosity can be added via the integrated homogeniser or drawn into the vessel through a valve at its base.

For larger mixer dimensions, Ekato had to determine the components’ dosage and dispersion times, blend and homogenisation times, vacuum values and the necessary agitator and homogeniser performances. The agitator and homogeniser were configured according to the mixing performance equation for mixing technology. Based on its extensive experience, Ekato determines the power coefficient ‘N_p’ (or Newton number) for each respective impeller and the product’s specific viscosity curve. This in turn specifies the force required to agitate the mixture.

As the drive supplier, NORD Drivesystems was required to configure motors and gear units with the performance according to Ekato’s calculations, and to make them as efficient and durable as possible. Since the agitator drive is installed on top of the production mixer, it should be as compact as possible despite the high performance required.

This application, which depends on homogeneous product quality, calls for speed and continuity. The radial and axial loads on the agitator shaft, which are very high due to the high product viscosity, must be taken into account for the drive configuration. NORD Drivesystems configured and supplied two 250 kW motors with industrial gear units which provide nominal output torques of 242 kNm. NORD is the only manufacturer worldwide to produce such extremely large industrial gear units in this power range in a one-piece housing. Hence, the type SK 15407 three-stage helical bevel gear units, though of an impressive size, are still relatively compact as the UNICASE design allows for larger rolling bearings which can accommodate higher forces.