Cummins Emission Solutions is one of the world's leading manufacturers of exhaust aftertreatment systems for diesel engines. The solutions are used in commercial vehicles as well as in machinery. These include feed and metering units for urea solutions, which as a central element in SCR systems (SCR = selective catalytic reduction) ensure a reduction in nitrogen oxides (NOx). The feed and metering systems are produced, among others, by Cummins Juarez Emission Solutions, which was founded in 2014 and is based in Ciudad Juárez, Mexico. Decisive for the effectiveness of the SCR systems is the finest possible atomisation when dosing the urea solution into the exhaust tract. "The cleanliness of the components plays a decisive role in the optimal functioning of our metering systems," explains Hugo Perez Palomino, Manager in Manufacturing Engineering and New Product Introduction at Cummins Juarez Emission Solutions.
With the EcoCcore, they chose a cleaning system from Ecoclean that works with a non-halogenated hydrocarbon or modified alcohol. Since Ciudad Juarez is located in the Chiahuahua desert, where there is a shortage of water, it was a great advantage that the system operates without water. The integrated media treatment enables a very good regeneration of the solvent, so that it can be used for a long time without additional maintenance or renewal. The single-chamber system is characterised by extensive standard equipment with, for example, two stainless steel flood tanks for preliminary and fine cleaning, heat recovery, full-flow and bypass filtration as well as high-performance distillation. The standard pre-steam degreasing also contributes to the high cleanliness of the parts. The oil-containing condensate is not fed into the flood tank as usual, but directly into the distillation unit. This minimises oil deposits in the flood tank or oil enrichment of the hydrocarbon and thus optimises the degreasing performance. In addition to injection flood washing, the system is equipped with ultrasound, which can be used simultaneously with filtration. Removed particles are thus discharged parallel to the cleaning process and cannot be deposited in the working chamber. A frequency-controlled rotary drive enables the rotation and precision positioning of the workpiece carriers.
High throughput and short cycle times
The parts are cleaned at Cummins Juarez in three-shift operation as set goods in workpiece carriers. The large batch size allows several workpiece carriers to be combined into a stack, which contributes to the desired high throughput. Due to the variety of parts, nine different, part-specific cleaning programmes are used. This means that the various process parameters, such as times and intervals for injection flood monitoring and steam degreasing, for ultrasonic power and duration, and for drying, can be precisely matched to the workpieces to be cleaned. Depending on the programme, the cleaning times are between six and eight minutes per batch. The comparatively short cycle times also ensure that the throughput requirements are met and thus the cleaning costs per part are minimised. The cleaning system thus offers a very good combination of the essential factors of cleaning performance, throughput and cost efficiency. With dimensions of 4663 x 1938 mm (L x W), the system takes up just about nine square metres of production space.
The complete article was published in German in JOT 07/08/20.
Author(s): Doris Schulz, freelance specialist journalist, Stuttgart, Germany