Buy used core shooters

Core shooter design: To select the right machine, it is worth taking a look at the basic functionality of core shooters. These machines are part of a foundry’s core shop and are used to produce the sand cores for cavities in the casting. Typically, a core shooter consists of a storage container for the ready-to-core sand (mixed with binder), a shooting chamber and the mould itself – the core box. The core box forms the negative mould of the sand core to be produced.

During the core shooting process, the prepared moulding sand is pressed (shot) into the closed core box at high speed. This is done with a short, powerful blast of compressed air – usually in the range of 2 to 6 bar. The sand completely fills the cavity of the core box and forms the desired core mould. The sand core must then be hardened so that it remains stable when it is later inserted into the mould. A distinction is made depending on the process:

Cold box process: The cold box process works with unheated (cold) core boxes. Immediately after the sand-binder mixture is injected, a gaseous hardener (usually amine) is passed through the filled box. The chemical reaction between the binder and the gas hardens the core within seconds. Advantages: very fast curing at room temperature, high dimensional accuracy and suitable for complex or large cores. Cold box cores have high strength, but the amine gases produced during gassing must be extracted and treated in an environmentally friendly manner.

Hot box process: In the hot box process, the core boxes are heated. The sand is mixed with a thermoset resin (e.g. phenolic or furan resin), which polymerises due to the heat in the core box. After the sand has been shot into the hot box, it remains in the mould for a short time (a few seconds to minutes, depending on the core size) so that the heat hardens the core completely. The resulting cores are immediately dimensionally stable and can be removed. Advantages: no additional gassing agent required, good core strength. However, the energy required is higher and the process is more suitable for medium core sizes or special applications (e.g. if certain resins or coatings are to be used).

Other processes: In addition to cold box and hot box, there are also special core production processes. One example is the CO2 process (water glass process), in which the moulding sand is mixed with water glass as a binder and hardened after casting by introducing CO2 gas. Another is the croning process (shell moulding process), in which sand coated with synthetic resin is blown into heated core box halves and hardened – ideal for thin-walled shell moulds. These processes sometimes require modified machines or additional equipment, but are also widely used in foundry practice.

Horizontal vs. vertical core boxes: Core shooters also differ in the design of the mould holder. There are systems for horizontal core boxes (the core box is closed from above and below) and for vertical core boxes (the halves close sideways, i.e. left/right). Which version is selected depends on the core geometry and the desired shooting direction. Vertical core shooters, for example, enable an even more even filling of certain complicated cores, as the sand flows in horizontally. Many modern machines (e.g. from Laempe or Loramendi) can be flexibly adapted to both core box variants. It is important that the core box dimensions and weight match the machine – manufacturers provide precise specifications for this (maximum mould dimensions, clamping force, etc.). TCT Tesic will advise you on this so that your chosen used core shooter harmonises perfectly with your existing core boxes and moulds.

All in all, core shooters – whether cold box or hot box, horizontal or vertical – enable automated, precise and fast core production. They are a key factor for productivity and quality in casting production. By understanding how they work, you can better assess which used machine fulfils your needs.