The first production car using aluminium unibody had an impressive 500 pounds weight savings over steel construction. Since that time aluminium became a dominant construction material of the car industry which, in fact, consequently requires specificity of the ELV recycling process.

Car wheels are a significant part of the total weight of Al dominant cars. They historically can be made from Fe, Mg, and wrought Al alloys. However the number one constituent in automotive wheels are cast Al based material. Cast Al wheels can vary in Si content from 5-6% up to 14-15%. This variation makes the recycling process expensive as the addition of, or dilution using lower concentration Si additives, requires a lot of incremental furnace time. Austin AI’s (AAI) patented automated LIBS based sensor-sorter has solved this issue.

LIBS technology is well documented. It has the capabilities of other outer-shell electron spectroscopy such as arc/spark which are commonly used to certify—or advise—on the quality of any melt. Several key advantages of LIBS are non-contacting, very quick analysis time, and a full range of major/minor/trace elements. If whole, used car wheels are desired to be sorted by alloy type, then commonly hand-held devices such as LIBS and XRF guns are used. Even in the best of cases the wheels need some pretreatment for cleaning the analytical surface and seconds per analysis. It is possible to run up to 1-2 wheels per minute in this manner optimally yeilding 1.5 tons per hour, per person. 

The AAI LIBS based wheelsorter system automatically cleans, tests, and determine the whole car wheel to pass or be rejected based on its chemistry. This can be done, as follows:

1. The first step is an automated infeed stage where wheels are loaded into the sensor-sorter in a nose to tail fashion. This ensures maximum throughput. 
2. The next stage is the wheel registration phase that places the edge of each wheel in a predictable position for the subsequent stages. A leverage arm pushes each wheel against a left or right rail that puts the wheel in the proper position.
3. Next, to ensure the upcoming analytical phase is performed on a clean surface, an abrasive wheel is gently pushed against the wheel rim. This is truly only necessary where wheels are powder coated in thicknesses greated than 3 mm due to the power of the solid state, metal cutting laser itself. For most cases dirt, paint, grease and oil have no detrimental impact on the LIBS analysis. However to make sure that each wheel is cleaned to the same level this section is applied to all wheels. This stage is designed with dual wheel usage thus allowing an operator to easily replace worn wheels while the system is fully functional.
4. The subsequent segment is the analysis stage where the cleaned section of the wheel is pulsed at 50,000 hertz by the laser. At this rate the cleaned portion yields a fine chemistry of the substrate wheel alloy. Each LIBS crater blast is connected to its predecessor thus creating a fully connected line that generates full chemistry on each wheel.
5. Following analysis the wheels are accelerated to the diversion stage. Here, based upon the user’s requirements wheels are diverted into one or more outputs or allowed to pass as per the client’s specifications. Used whole car wheels, thus sorted, are capable of directly entering the wheel shredder followed by secondary furnace in-feed. 

This wheelsorter technology easily yields about 10 times the throughput of hand sorting and there is no human interface. The footprint is reasonable and adaptable outside of the infeed and output limits of the system itself. Austin AI has direct and 90 degree input/output designs. Also regarding the diverter stage we have options for pneumatic pushers to outflow belts, bins, or bunkers. Accepted wheels can, as previously mentioned flow directly to the shredder or storage bunkers.

The control panel is outfitted with input/output wiring to allow control from the overall line management while controlling those aspects under the sensor-sorter stage. 

Make no mistake about the power of LIBS as an analytical tool. This technology is far superior to other sorting techniques such as X-ray (transmission or fluorescence), color sorting, or others; when considering sensitivity and timing. The sorting process can be quite stringent. For example, some users have requirements beyond the Si content, such as very low Fe +/-0.15%, and Cu at +/-0.10%. When you imagine the wheels are moving along on a conveyor, for most applications using LIBS, this is a very impressive statement with regard to the latest advancement of the art.

Moreover, the program(s) allowed by the LIBS module itself are easily adapted and afford quick changeover if the client has multiple allowable outputs based on their client’s chemistry demands; or if changes from infeed wheel specifications should change from time to time.

The savings in fuel consumption per ton of output is a major savings by itself. Labor, turnaround time, and tonnage throughput all dramatically feed to the bottom line of the secondary smelter. In addition this generates a significant green impact to the smelter’s operations. It truly is this last point that reflects upon the sustainable nature for any secondary processor.