Dosing Furnaces for Foundries
Equipment advances help to improve foundry operations as does using the best equipment.
Nine Westomat dosing furnaces from StrikoWestofen underpin die-casting operations at Lenaal’s industrial aluminum and zinc parts manufacturing facility in Radom, Poland. The plant installed its first furnace in 2007.
When the company decided to evaluate how future investments could be maximized, Lenaal (the company) had the perfect opportunity to gauge current levels of efficiency and explore whether it would be better to switch to pump-based dosing technology.
A pump-based dosing furnace was installed at the foundry for real-life assessment against the Westomat (the furnace). The evaluations determined that they should stay the course, and they replaced the pump-based dosing furnace with a new Westomat to meet current needs and achieve future goals.
Spotlight on Reliability
The company’s die-casting machines are rarely at a standstill. With the foundry running a three-shift system to cast parts for the automotive and construction industries, each die-casting machine has an output of roughly 250 kg/hour.
With live operations, genuine demands and actual customer orders to be fulfilled, all dosing technologies met the same conditions and faced the same challenges. Company experts rated the dosing equipment based on system stability, melt quality and process reliability. Metal quality was of particular importance because it directly impacts product quality and scrap rate. Observations of live operations proved the technology to be the superior candidate for dosing reliability and metal quality.
Theodoor van der Hoeven, head of research and development at StrikoWestofen, said, “When liquid aluminum meets air, oxides are formed, making it important not to rupture the protective oxide layer on the surface of the melt during dosing. So for systemic reasons, the Westomat removes melt from below the surface of the bath. In a dosing pump system by contrast, the liquid metal flows over an edge into the pump and is exposed to the atmosphere again. A transfer process into a pump is not necessary with the Westomat.”
One Chamber, Numerous Advantages
Heating efficiency was a critical measure in the company’s performance analysis. Process observations highlighted that the metal heating elements used in furnaces with pump systems are susceptible to damage from splashes of molten metal, whereas the three SiC heating rods used in Westomat dosing furnaces are extremely robust.
Cleaning and maintenance are also huge day-to-day challenges of many foundries. On all fronts, the furnace’s simple one-chamber structure simplifies these challenges. The design means the furnace has no pump inlet valve that meets liquid metal. As well as reducing machine wear, this means it is not necessary to clean additional chambers or pump pots, while all areas are easy to access.
“Minimal maintenance requirements, low wear and tried-and-tested components give machines a 98% availability rate,” van der Hoeven said. “Plus, if you compare the cleaning requirements for dosing pump and riser tube, the downtime for the furnace is considerably lower at around 0.043% compared with 0.7% for the dosing pump system.”
The furnace’s one-chamber system also allows temperature differences to be virtually ruled out, which was an advantage to the company. On the flipside, differences of 1-10 degrees can occur in an additional pump pot. These temperature variations affect the flow characteristics of the melt, impacting dosing precision and the filling of the mold.
Tomasz Marcela, process engineer at Lenaal, added, “As part of our efforts to test, refine and optimize our processes, we tested technologies with a pump system, but the Westomat is the best solution for us. The dosing precision and the lower fluctuations when starting up after the complete cleaning of the furnace were very convincing for us. These properties allow the scrap rate to be reduced too.”
When comparing the dosing furnaces, the company was not only interested in technology and performance but also in the support services. StrikoWestofen’s repair and maintenance packages and rapid spare-parts supply provided a great deal of additional assurance.
Marcela concluded, “Not only does Westomat deliver on technology and reliability, the knowledgeable technicians (see sidebar) at StrikoWestofen run a service so efficient that we can plan our maintenance to minimize downtime, which leaves us free to focus on delivering quality parts to our customers.”
For more information: Contact StrikoWestofen Group, Katharina Seidler; tel.: +49 (0)22 61 – 70 91 108; e-mail: firstname.lastname@example.org; or Sina Kasper, dako pr corporate communications; tel.: +49 (0)2 14–20 69 1-0; e-mail: email@example.com.