Low Pressure as an Example of a Sustainable Process
To produce in a sustainable manner is becoming increasingly important in our society. The main reasons are the effects of the climate change, such as severe weather disasters as well as the global rise in sea temperatures. New laws are enacted to ensure sustainable business practices and also set the rules for future production processes. Developments regarding "clean" technologies are necessary and promoted, and they are replacing previous standards in many sectors.
Lightweight construction plays an important role in the aviation as well as the automotive sector. An aircraft or a vehicle optimized for lightweight construction will have a reduced energy and fuel requirement. For aluminum cast parts, which are often used, the following requirement applies: the same or even yet a greater stability of the parts with reduced weight. This can be achieved either by saving material or by using hollow casting technology via sand cores and after de-coring of the cores.
The continuing development towards minimizing component weight and therefore reducing CO2 emissions still drives this trend. The Kurtz low pressure process can make a significant contribution to saving resources. Not only thin-walled parts of 3 mm or even thinner are feasible, but also parts in combination with material accumulation and in connection with high mechanical properties and with reduced recycled material.
Key factors for a successful casting:
- Perfect mold filling
- Cooling technology
- Furnace technology
- Intelligent and flexible machine design
KEY FACTOR
Perfect Mold Filling
The heart of the low pressure process is the turbulence-free filling of mold. The aluminum melt is protected from environmental influences inside of the furnace. By pressurizing the furnace in the range of millibar up to a maximum of 1 bar, the aluminum melt is poured into the mold cavity, usually a permanent die-cast mold, by means of a riser tube. After filling of the mold, the edge shell starts to solidify, whereas the feeding pressure is increased again to densify the cast part.
Compared to gravity casting, it is not uncommon to save up to 70% on recycling material (depending on the size of the part) and to achieve a higher output of cast parts as well as fewer scrap. As air is the most expensive medium in the foundry, there is also great potential for savings here. The Kurtz pre-pressure technology reduces the air consumption required for the casting process to a minimum and at the same time optimizes the cycle time for mold filling by always maintaining the same casting starting point. The furnace is not completely vented after a casting, which leads to energy savings of approx. 80% and at the same time shortens the cycle time and improves the quality of the melt.
KEY FACTOR Cooling Technology
Air is also used in cooling technology, although air cooling is increasingly being avoided due to its lower efficiency and high costs. Instead, focus is more and more placed on water cooling. In addition, the cooling of the process should be temperature and/or time-controlled in order to activate the cooling only when actually required. This prevents incorrect or excessive cooling. To ensure consistent quality of cooling, regulated cooling circuits are also used for this purpose, not just controlled ones. With this process-optimized cooling concept and controlled solidification a fine-grained structure of the cast part is achieved. Water cooling not only improves casting quality and shortens cycle times, but also reduces energy costs by approx. 64%.
Low pressure casting is a very good solution for making the casting process more sustainable. Production costs are noticeably reduced, while maintaining the greatest possible flexibility. The low pressure casting process not only saves production costs, but above all it conserves valuable resources such as energy and water – a win-win situation!

KEY FACTOR Furnace Technology
A further key factor is the suitable furnace technology. The use of large and highly insulated crucible furnaces with a capacity of 600 to 4,000 kg not only ensures long, continuous casting, but also enables the use of multiple riser tubes thanks to a large pitch circle. The different riser tubes can then be positioned exactly where they are needed for mold filling and feeding in case of large or multiple cavities.
Complex gating systems or expensive feeder boxes can be avoided by direct gating using a riser tube. As a result, the recycled material and downstream process steps such as sawing, grinding etc. are reduced to a minimum. The furnace is changed at the same time as the cast part solidifies to ensure a stable and consistent mold temperature. Start-up parts to get the mold up to right temperature is therefore not necessary.
The filling of the furnaces and subsequent the melt treatment in the furnace takes place outside of the casting machine using an exchange furnace concept which reduces the machine downtime to a minimum and benefits the overall equipment effectiveness (OEE). The preferred solution of "in-line" filling from the melting furnace directly into the crucible furnace (casting furnace) significantly reduces internal forklift traffic. In addition, the melt temperature in the "in-line" melting furnace can be reduced by up to 40°C, as no further intermediate transport is required. This has a positive effect on energy savings. After the filling process, the melt is treated directly in the crucible furnace - which is also the casting furnace. This achieves the best melting quality. Closing the crucible furnace with the riser tube cover not only ensures that the processed melt is under a kind of protective atmosphere, but at the same time saves energy costs.
KEY FACTOR Intelligent and Flexible Machine Design
Ribbing not only enables lightweight constructions for cast parts, but also in mechanical engineering. Moving masses are reduced. In combination with an intelligent control system maximum efficiency is achieved. According to the principle „better data – better decisions“, the machine control system enables the operator to intervene more quickly and achieves a high level of efficiency in series production thanks to controllable processes. Interacting with the data management, the quality management for the documentation of each individual cast is carried out. Recording of this data is not only the „birth certificate“ of the cast part, but also a reflection of the results which are used for process optimization. This type of intelligent data handling makes it possible to reduce the scrap rate and to achieve a higher OEE.

Would you like to receive information about the key factors “furnace technology” and “intelligent and flexible machine design”? Find out more about the two key factors online or send an email to info@kurtz.de