Trendgineering
Stability for the spin cycle
| Jens Fiedler
Europe's largest manufacturer of washing machines relies on MX machines from KraussMaffei
When a washing machine drum spins at 1200, 1400 or even 1600 rpm, the housing and counterweights must be powerful enough to counter this. With plastic components there is no room for dimensional deviations or unevenly plasticized areas. Arçelik, Europe's largest manufacturer of washing machines, uses KraussMaffei MX series injection molding machines – with APC plus and high-performance screws.
Cooperation between Arçelik and KraussMaffei
Anyone who enters a certain production hall in Cayirova near Istanbul can follow the complete development of a washing machine: from fluff filter and electronic control system through to packaging and transportation. The Arçelik Group, the third biggest manufacturer of major appliances in Europe, operates its most important washing machine production here with 3.75 million appliances per year.
Successful on the market:
Arçelik Plastic Shop Manager Alper Deniz, Tepro Marketing Executive Neslihan Demircioglu and Arçelik Plant Manager Fatih Kotan (from left).
For the large and heavily stressed components the robust and high-performance MX machine from KraussMaffei with clamping forces between 16,000 to 23,000 kN is used. Both companies have been working together since 2004.
Production Manager Fatih Kotan explains his business: "We have to differentiate ourselves on the market through high product quality and efficient manufacture and we attach huge importance to automation and availability. A production failure would be a catastrophe with our tightly scheduled production with low inventory. Thankfully our MX machines are completely reliable: The availability is at least 98.5 percent."
Stability and uniformity
The injection molding heavyweights are primarily responsible for a certain component of the washing machine: the two-part housing in which the stainless steel drum rotates. Manufactured from polypropylene with glass fiber or calcium carbonate filling, it must withstand the vibrations and at the same time maintain the connection with the counterweight. A pick & place linear handler inserts metal bushes in the mold, which are initially insert molded and to which the weight is subsequently screwed.
To avoid component weakening at any point due to uneven plasticizing, Arçelik uses the high-performance screw HPS-AT, which was developed specially for materials such as filled PP. The flight-coil design permits a very high mixing quality with fast cycle time and high throughputs. The fibers are distributed evenly and the polymer reaches the cavity stress-free. Products remain streak- and inclusion-free; they can also be easily coated.
Automation as an important factor
With each shot a housing upper part and lower part is shaped in 1+1 molds, the shot weight is 5.5 to 10 kilograms, the cycle time is approx. 65 seconds including handling. Arçelik manufactures 100 various housing types in this way; this rich variety as well as the necessary flexibility are another reason for the company's interest in smart production with a high degree of automation of 96 percent.
APC plus for cost-efficient production
With 25,000 tons of raw material, which Arcelik processes every year in Cayirova, the shot weight consistency is extremely important. A tiny difference can already give rise to huge costs and vice versa the slightest saving adds up to satisfactory amounts. The APC plus machine function helps here, which based on material data such as compressibility, measures the melt viscosity, predicts the shot weight and then readjusts the switchover point as well as the holding pressure level from shot to shot. Factors that could cause deviations in the cavity filling such as room temperature and humidity or batch fluctuations are balanced in such a manner. This results in parts that are extremely consistent in terms of weight.
"The start-up after short downtimes of up to 15 minutes is much easier thanks to APC plus and our scrap has reduced by a high single-digit percentage."Fatih Kotan, Arçelik Plant Manager
The self-optimizing machine fits Arçelik's concept perfectly and the MX machines are integrated in the company's own MES (Manufacturing Execution System). Using a graphics analysis package the production team monitors the machine parameters separately and can respond straight away to tolerance deviations.
For Turkish KraussMaffei customers the comprehensive support from the sales and service partner Tepro also plays a big role. With 24-hour service and several locations, Tepro is close to the customer, provides information on the latest technical developments and can respond quickly if a spare part is required.
Future development plans
Arçelik currently aims to raise its overall equipment effectiveness (OEE) to over 95 percent, whereby the energy requirement (target figure: 0.28 kWh/kg) and the shot weight consistency (target: 99.93%) play key roles. In both disciplines the KraussMaffei machines in the plant are the measure of all things (OEE 98.5%) – the lowest energy requirement here is 0.27 kwh/kg. The robust two-platen clamping unit of the MX also works accurately with high mold weights over long periods and with its exact form fit and the high-performance plasticizing unit delivers components that are very consistent in weight – even more with APC plus. A wide range of additional technologies is also available.
At Arçelik two development requests are already on the agenda. Firstly, one wants to achieve material savings using physical foaming and also reduce sunk spots with consistent mechanical property patterns. Secondly, it makes sense to use as much recycled material as possible for cost and environment protection reasons. The latest screw technology and APC plus are also required for this.
Arçelik will continue to grow with this forward drive. Today 18 plants for major appliances are currently in operation in seven countries and deliver products to 130 countries under brand names such as Beko, Grundig or Flavel. The high technology from KraussMaffei will contribute to the future expansion.