Auto Clean: Turning Performance

Courtesy of acp

In the face of increasing cost pressure for automotive suppliers, functional surface cleaning, such as with the CO₂ snow jet process, provides a viable approach to saving time and money.

Equipment and media options for cleaning automotive parts.

Component cleanliness is a quality criterion in the automotive industry. Requirements are becoming stricter with each vehicle generation, which increases cost pressures on auto parts manufacturers. Therefore, they must optimize parts cleaning.

With the global emphasis on reducing CO₂ emissions and fuel consumption, there is need for smaller engines that run more efficiently with high power output. These engines require tight-tolerance components capable of withstanding extreme loads.

However, precision components have an increased sensitivity to contamination. Even particles as small as 100µm can cause operating problems or component failures. This is why the automotive industry has started defining particle-size distributions for certain parts in functional modules, such as the power train, steering system and brakes. For example, the requirement might state there can be no more than 500 particles on the part ranging in size from 200µm to 400µm.

To fulfill and document these requirements, large investments in industrial parts cleaning equipment are sometimes required. For example, the cost for cleaning technology that meets a specification of “no particles larger than 1,000µm” is two to three times higher than for systems designed to meet less stringent standards. This article focuses on cleaning equipment and media available to achieve new, more stringent standards.

Minimizing Contamination

One approach to parts cleaning optimization is component design, because workpiece geometry; the individual steps of the manufacturing process, such as turning, milling and assembly; and cleanability are determined during the design stage. The latter consideration usually plays no role in the design process, but it can cause major problems during the production process: Some parts have internal corners, edges or holes from which manufacturers can only remove particles and processing residues with considerable effort—or not at all.

Because machining removes material in the form of chips, contamination can never be entirely avoided. The quality of coolant and other metalworking fluids influences the quantity of chips, burrs and particles on workpieces. Suitable filtration matched to particle size prevents previously removed contaminants from returning to the component. To assure continuous particle removal, the cleaning equipment must employ a gentle but continuous bath motion.

In addition, a special rinsing step while the tool is in the machining center—perhaps with more finely filtered fluid from a separate tank—can reduce the level of chip contamination. At first glance, this represents an additional expense, but it typically pays for itself through shorter cleaning times, longer bath service life and higher component quality. Removing residues after machining by means of mechanical precleaning—such as vibrating, shaking, spinning or vacuum blasting part surfaces—also minimizes contamination and reduces the load on the cleaning agent.

For applications requiring multistage machining processes, intermediate cleaning steps prevent contaminants from accumulating, mixing or drying on the workpieces.

System Design

Modern cleaning systems can fulfill high demands for component cleanliness, assuming the cleaning process has been matched to the contaminants to be removed, part geometry, workpiece material and the cleanliness specification.

The particle limit value of “smaller than 1,000µm” for engine and gearbox components, for example, can only be achieved with a cleaning process designed specifically for the respective part. State-of-the-art cleaning systems use a multistage procedure to achieve this.

Courtesy of LPW Reinigungs Systeme

Modular cleaning systems, which can be integrated into a parts production line, offer flexibility. In this example, diesel injection system parts are transferred from a cleaning chamber to a vacuum dryer.

The workpieces are mechanically cleaned, such as via spinning or vacuum blasting, during the first step, which removes some of the metalworking fluid. The second step involves immersion flooding, where water is injected at 145 to 220 psi into the cleaning chamber below the surface of the bath. The resulting whirlpool rinses chips and contamination out of hollow spaces, such as threaded blind-holes. Waterjets aimed at openings in the component and lances advanced into holes quickly optimize results. Lances allow users to inject cleaning fluid at a high pressure into drilled holes and remove contaminants while also deburring. A drying process then follows rinsing.

The growing number of engine and gearbox variations, as well as ever-shorter product life cycles, requires significant cleaning system flexibility—even for individual part cleaning operations. This can be accomplished with robotic cleaning systems, which are integrated into production lines. Thanks to simple reprogramming options, these systems assure levels of flexibility comparable to those offered by machining centers.

Large numbers of vehicle parts can be cleaned at the same time in batch processes. Single- and multiple-chamber systems, which can be integrated into the production line, are also available for these batch cleaning tasks.