When a casting is produced, quite a few by-products are generated. Small pieces originating from spills, gates, runners and risers are returned to the casting process as recycling material. To ensure a consistently high overall quality of the raw material, it is essential that this recycling material is perfectly clean without any sand or other residues on the surface. That is why a renowned automotive supplier decided to subject these by-products to a blast cleaning process in a Rösler multi tumbler system, before they are re-melted. This blasting process offers many advantages. Besides the resource-saving use of raw materials, the effective cleaning of the recycling material increases the uptime of the smelting furnaces by significantly reducing the amount of unwanted slag.
The globally active Federal Mogul Burscheid GmbH is an OEM company supplying parts for passenger cars, trucks and off-highway utility vehicles as well as components for agricultural, railway and aerospace equipment. The company also supplies other OEM’s active in these and other industries with premium products for maintenance and service. Among others, these include components made from steel, nodular iron, and grey iron castings.
Recycling material that is significantly cleaner!
The casting of the various work pieces takes place at various foundries, one of them located in Burscheid, Germany. To increase the company’s overall resource efficiency, the spills, gates, runners and risers are separated from the castings at the shakeout station and recycled into the casting process. Prior to re-melting, the contaminants consisting of residual sand and casting scale must be completely removed from the recycling material. For this purpose Federal Mogul is utilizing a drum shot blast machine, model RMT 70-F, in its Burscheid foundry. One key factor for investing in this type of shot blast machine was that, compared to other shot blasting systems, it produces significantly higher cleanliness of the recycling material.
Well-planned equipment concept with a focus on foundry applications
Thanks to the unique geometry of the blasting drum the customer chose the Rösler multi-tumbler for blast cleaning of the recycling material. The drum bottom contains a three-sided pyramid, and the inner drum wall is equipped with specially formed cams. The latter promotes a lateral mixing of the work pieces, while the pyramid in the drum bottom ensures an effective exchange between the upper and lower work piece layers.
The customer was also impressed by the rugged machine concept that was specially adapted to foundry applications. This includes the sturdy welding construction of the machine frame made from 10 mm thick steel and the blasting drum made from 10 mm thick highly wear resistant austenitic manganese steel. Another feature of the foundry equipment version is the special heat protection of various components. For example, transport belts, plastic components, and electronic components are all heat resistant allowing continuous operation without having to wait for the recycling material to cool down. Special vents in the blasting drum are dissipating the heat carried into the drum with the recycling material and are, thus, preventing excessive heat buildup. The special foundry equipment version also includes a large inspection platform, which is easily accessible through various stairways. For quick mounting/dismounting of the turbine and blasting drum, the machine is equipped with a loading beam with trolley consisting of an electrical lifting and lateral transport device. Both ensure easy and quick maintenance of the Rösler multi-tumbler and improve the overall uptime of the blast machine.
Special blast turbine guarantees high uptime and excellent cost efficiency
The Gamma 400-8G turbine was specially designed for the challenging operating conditions generally found in foundries. In contrast to the traditional Gamma high-performance turbines, the Gamma 400-8G is equipped with 8 instead of 6 throwing blades and contains a wear lining made from solid tool steel. This special feature reduces the wear of the throwing blades by up to 25 percent. The reduced time for maintenance contributes to higher productivity and cost efficiency. Like with all Gamma high-performance turbines the throwing blades are curved in the special “Y” design. Compared to conventional blast turbines the curved blades produce an up to 20% higher blast performance with, at the same time, lower energy consumption. Since both blade sides can be utilized, a simple turn of the blades practically doubles the expected life of the throwing blades. This is easily done with the help of a retaining bolt system and does not require disassembling the turbine.
Fully automatic shot blasting in an integrated manufacturing operation
A conveyor belt transports the recycling material from the shakeout station to an impact crusher supplied by LuT Metalltechnik GmbH, where the spills, gates, runners and risers are crushed into smaller pieces. These are then transferred to the fully automatic multi-tumbler loading station equipped with weighing cells. Once the preset weight in the loading station is reached, max. 1.8 metric tons, the conveyor belt stops, and the loading system transfer the crushed recycling material into the blasting drum. Upon completion of the loading cycle, the system returns to its base position. Alternatively, the loading system can receive the work pieces via 3 different part bins (double acting loading system).
During the shot blast cycle, the drum is hermetically sealed with a lid. This prevents any blast media from spilling to the immediate environment. While the drum rotates at a speed of up to 10 RPM, the turbine, with an installed power of 45 kW, throws up to 560 kg of blast media per minute onto the recycling material. The rotational speed of the drum and the turbine can be easily adjusted with a frequency inverter. The blast media throwing quantity adapted to the batch size, in combination with the multi-tumbling movement of the recycling material in the drum, ensures that all pieces are equally exposed to the blast media stream and all surface contaminants are completely and reliably removed. The removed contaminants in the form of scale and sand are siphoned off from the drum and discharged through a dust collector. The blast media is removed from the drum through custom-engineered screen inserts. Depending on the batch size and the density of the recycling material, the processing time can vary from a few up to maximum of ten minutes. At the conclusion of the blasting cycle the drum tilts into unload position. The shot blasted material is initially dumped onto a vibratory conveyor, from where it is transported to waiting for part bins.
The shot blasting process not only contributes to a greatly improved quality of the castings but because practically no residual contaminants in the form of scale and sand are carried back into the casting process, less slag is formed in the smelting furnaces. This reduces the wear rate of the refractory furnace lining and energy consumption. Moreover, the refractory lining must be cleaned less frequently. This improves the uptime of the smelting furnaces and increases the overall productivity of the foundry.
