Fifty million tubes of toothpaste are made every month at Liuzhou LMZ Co., Ltd.’s new production facility. Three vacuum mixing lines for manufacturing two different toothpastes have to be fed for this purpose. Azo received an order to develop an ultra-modern and future-proof system integrating the highest possible level of automation. Transparent production in all process steps was a top priority for LMZ.
Walter Sonntag
Liuzhou LMZ Co., Ltd. was founded in China in 1941 and has been listed on the Shanghai stock exchange since 2004. The company provides a very wide range of products, including body care articles such as shampoo, liquid soaps and toothpaste, household cleansers, homeopathic medicine, sanitary items and cosmetics. Its headquarters are in the South Chinese metropolis of Liu Zhou. With approximately 2000 employees, LMZ recorded a turnover of 150 million euros in 2007. According to a consumer study, LMZ is the most trusted brand in China. One of the flagships of its product portfolio is LMZ’s herbal toothpaste. This product is very well-known in China and is based on herbal ingredients.
LMZ planned to make two types of toothpaste on three vacuum mixing lines in the new production facility. The challenge was to integrate all components into the automatic process sequence, from larger components such as calcium carbonate and silica through additives and filling materials to liquid components such as flavourings, colours and medical ingredients. The correct components are to be fed to the mixer below liquid level at the right time and in the right quantities. The complete production process needed to be traceable, clearly documented and extremely flexible. Due to their importance within LMZ’s company philosophy, there were also high requirements for cleanliness and hygiene. Quality assurance was another very important aspect in the call for tenders. Process-optimised mixer feeding in the following order was therefore of top priority for this system, as this is decisive for premium quality:
- Provision of fluids in large volumes such as sorbitol and distilled water
- Addition of exactly weighed additives such as saccharine, fluoride etc.
- Addition of CMC binding agents
- Mixing of these components in the vac-uum mixer
- Admixture of the larger components such as filler or abrasive particles, either silica or calcium carbonate
- Feeding of liquid aromas
- Start-up of the mixing process
- Addition of soap
In the last step foaming had to be avoided at all costs. The vacuum mixing process is continuously deaerated to ensure this. Furthermore, the liquids must not boil.
Transparent production
As early as the project stage, the Azo team tried to achieve an optimum feeding of all dry and liquid components tailored to the mixing process. The larger components, medium-sized components and liquids are therefore all fed to the vacuum mixer below liquid level. The toothpaste produced in the vacuum mixers is filled into mobile containers. These are then docked onto the filling system, where the toothpaste tubes are automatically filled and packaged. The showcases, which allow production staff to view all parts of the system at all times, are particularly impressive. The process control station, at which the operator can permanently monitor the entire automation process, is another real highlight. Colour graphics, recipe lists etc. are projected onto the wall by a beamer, allowing the current situation to be monitored by everyone.
Precise dosing of all components
“Right at the start of the project it was clear that liquid components also had to be measured exactly when they are integrated into the automation process. It was really important for us that the additives are weighed correctly to the gramme and then automatically made available to the mixing process,“ says LMZ Works Manager Zhang Tao.
The liquids used include distilled water and sorbitol. They are the first components to be sucked into the vacuum mixer. They are stored in large tanks and fed below liquid level to the mixing process by additive weighing systems designed as fluid scales.
The additives are supplied in bags and are fed in the linear Azo Componenter by means of bag dump hoppers. Mobile scales collect the special additives needed for the recipe (accurately to the gramme) and pass them on to a collection container. From there the individual components are fed pneumat-ically onto intermediate containers in the form of scales. These additives, balanced optimally to the mixing process, are subsequently added to the liquids below liquid level. “Both when filling and during delivery, controlled sifting of all materials ensures that no impurities contaminate our toothpaste. This allows us to comply with the strictest quality requirements,“ the Works Manager continues.
Calcium carbonate, a main ingredient of toothpaste, is filled into interior silos via feeding hoppers which can be loaded on both sides after safety screening. These large components are then picked up by the Azo suction weighing system. As there are several lines to be fed, reliable vibration bottoms are used for discharge. Distribution to the individual lines is done by means of dosing screws. The second large component type in the recipe is silica. The interior hoppers for this component are likewise filled by feeding hoppers that can be loaded on both sides. Reliable vibration bottoms are used again to ensure the first in, first out principle. All extracted raw materials are fed through screeners before reaching the conveying scales.
The small-sized, automatic Azo vacuum weighing systems suck the powdered large components from the interior silo into the conveying scales according to the recipe specifications, weigh them exactly and then feed them below liquid level to the vac-uum mixers. Since large quantities are involved, partial amounts are fed during the vacuum mixing process to ensure optimum mixing with the liquid components already in the mixer. “Right from the start, we were really excited by the possibility of drawing in the raw materials without introducing air into the vacuum mixer. This makes the mixing process much faster and more effective, and it also avoids foaming,“ Zhang Tao reports. In the sensitive area of aromas, it was decided not to use volumetric feeding because this method is not precise enough to meet the customer’s special requirements. All liquids (flavour additives) are weighed exactly and fed to the mixing process below liquid level, accurate to the gramme, using negative weighing systems.
Positive overall impression
All parts of the Liu Zhou plant correspond to the highest pharmaceutical standards. The raw materials are precisely documented from the initial delivery to the end product. Optimal quality is guaranteed. The LMZ operating personnel were involved in the planning phase at a very early stage and coped easily with the system after a short training period only. Communication on site between the central process control and visualisation system and the operator terminals is extremely efficient. This additionally rules out operator errors and ensures precise, documented production. “We were fascinated already at the project stage by the close interaction of the feeding and mixing processes and the process control system. It was clear to us that this is the key to successful process implementation,“ says Zhang Tao finally.
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