Efficient De-Coring Process at BMW Landshut, Germany

The following options are offered by CEC:  

1. The Sand Lion Roller Hearth Furnace (RHF) used for high quantity running production in continuous operation mode. 

2. The Deep Fluidized Bed (DFB) Furnace used for small and medium-sized production in batch-type operation mode.

The foundry management of the BMW Group at Landshut, Germany, decided to use the DFB furnace for their de-coring operation. The parameters set by BMW to de-core their special castings in aluminum alloy in a DFB furnace prove to be advantageous as the core sand is reclaimed simultaneously (similar to the Sand Lion roller hearth furnace).

During the test phase, carried out at the CEC R&D facility, trials were made with castings having complex and complicated geometry of hollow chambers. After processing in the DFB Furnace the castings were completely de-cored and core sand was fully reclaimed.

The size of the core packages to be treated exceeds the ones from similar operating systems. Others build even larger units for cleaning lacquer, paint and plastics from parts. For the foundry industry it was the first unit of such dimensions and a new technical challenge, which was solved by CEC with excellence.

Having concluded these trials with great success, the client decided to award CEC the order for this effective but gentle treatment in the DFB furnace for de-coring their specialty motor parts.

The Fluidized Bed process is a highly engineered thermodynamic technology that can be applied to heat-treatment, thermal cleaning of complex machine parts and tools as well as tempering. The furnace chamber for foundry applications is filled with a fine-grained heat-transfer medium (foundry sand), which is fluidized with hot air or gas. The resulting hot Fluid Bed provides excellent heat-transfer properties and high-accuracy temperature control. Furthermore, the vast amount of heat accumulated in the Fluid Bed leads to extremely fast and uniform heat-up of the load.

The DFB furnace consists of an insulated rectangular sheath (retort) of 2.650 x 1.600 x 1.500 mm and contains approximately 10 metric tons of sand as fluidizing medium. DFB furnaces can be gas-fired or electrically heated. Operating temperatures can be selected depending on treatment parameters of material charged. As an example, for aluminum the operating range is 450 - 480C.

The DFB furnace is covered by a lid, which is only opened for loading and unloading of the charged material. Handling of the charging baskets is done by means of overhead or jib crane. De-coring cycle time is between one (1) and five (5) hours per charge depending on complexity and weight of castings as well as quantity of core sand. Castings in core packages are placed into a charging basket and submerged into the fluidized sand bed. Usually, air preheated by a heat exchanger is introduced into the retort from the bottom through a nozzle system for fluidization. Thus, this hot air transfers the heat energy into the bed and simultaneously fluidizes the sand.

After submerging the core packages into the bed, binder is thermally attacked and dissolved, thus the casting is cleaned. This process continues until all organic matter is dissolved and the casting(s) as well as the sand are completely clean. By introducing core packages into the bed, additional sand is brought in and the sand volume in the furnace increases. Loose sand, which is already reclaimed, flows via overflow device into a buffer silo. After cooling and screening, sand will be used in the core shop again.

The very advantageous facts of this system are:

• Gentle treatment of the castings by controlled thermal process No mechanical forces, therefore no damaging of castings High flexibility because of thorough and gentle cleaning of complex cored castings
• Technical progress, since cleaning is executed independent of design of castings and, in addition, very complex shapes can be de-cored

Market and client response for this new and innovative de-coring technique is very positive and future projects are under consideration.