HE (Humid Environment) robot excel where others fail

100 percent humidity, 43°C ambient temperature and a pH of 9: in such conditions, the deployment of robots poses real challenges. These are the very parameters under which Stäubli TX200 HE robots are delivering reliable service on the parts cleaning line at the Nissan Dongfeng engine plant in China.

Nissan sold more than 1.2 million vehicles in China in 2018. A significant proportion of these have been manufactured in the country since 2003 when the automaker entered into a joint venture with the Dongfeng Motor Corporation.

Today, Nissan Dongfeng operates four car factories in China. The plant in Guangzhou produces various Nissan models, including the Sylphy, Sunny, Murano, X-Trail and Altima. The engines are made in Huadu, a district of Guangzhou.

Cleanliness of components, a vital factor in engine production

Component cleanliness plays an extremely important role in modern engines. Even the most minimal contamination can lead to damage with severe consequences, which is why parts cleaning is considered to be crucial.

In the automotive industry, clearly defined residual contamination criteria apply, which can only be permanently adhered to when reliable processes are in place.

On this basis, an efficient and highly automated parts cleaning line was installed in the Huadu plant. Stäubli robots have been handling the components reliably and problem-free for several years now. The plant itself started out with robots supplied by another manufacturer, however, these were not up to the tough conditions. The gruelling nature of the process resulted in excessive downtime and high maintenance costs. For the user, this was an unsatisfactory situation that could only be resolved by completely replacing all of its robots with high-performance Stäubli HE six-axis machines.

The redesign was carried out by integrator and local Stäubli partner Harbin Shimada Big Bird Industrial Co Ltd. The company’s robotics expert had to contend with some difficult challenges. The cylinder blocks and heads are manufactured across four lines; at the end of these lines are cleaning stations. These cleaning stations have one cell for precleaning and one cell for final cleaning, the cycle time per station is not allowed to exceed 65 seconds.  

A robot specifically suited to harsh environmental conditions

The Harmin Shimada Big Bird engineers opted for Stäubli TX200 HE six-axis robots. These machines were considered to be ideally suited to the task intended because  they have been developed for use under adverse conditions.

The HE suffix stands for Humid Environment, making these robots especially suited for the task. This special equipment package is particularly in demand when the robots are used for the cleaning of automotive components, including gearboxes, cylinder heads and blocks, turbocharger housings, crankcases, crankshafts and camshafts.

The HE robots have been given an exceptionally resistant surface treatment and their joints have been effectively sealed. The inside of the robot arms, which are IP 65 compliant even in the standard version, can also be subjected to slight overpressure. This prevents moisture from entering the robots and impairing their function. The wrist is IP67 rated and even able to withstand immersion in liquid media. In addition, all connections are located under the robot pedestal where they are protected from moisture.

These design features are effective even when the robots are used in cleaning operations involving a high-pressure water jet or, as is the case at Nissan Dongfeng in Huadu, when handling components on automated parts cleaning lines.

Ultra-resilient HE robots are the answer

The TX200 HE picks up the cylinder block weighing up to 30 kilos (the cylinder heads weigh up to 18 kilos) with a gripper from a roller conveyor, swings it across to a bath and lowers it until it is submerged. To ensure that any issues are reliably fixed, the six-axis robot follows a meticulously programmed motion profile.

The robot arm is immersed no further than its wrist, yet the housing is permanently wet from being splashed with cleaning fluid; this is the only way to ensure optimal cleaning results. These thoroughly cleaned parts are then passed through a drying unit.

Incidentally, not only is Dongfeng’s partner Nissan of Japanese origin, but also the system integrator who installed the parts cleaning robots at the Huadu plant. Harbin Shimada Big Bird is a subsidiary of Japanese robotics specialist Shimada Kasei Co Ltd, which has a high level of expertise in planning and designing automated deburring and cleaning systems.

Extensive experience of harsh environments

The Nissan Dongfeng management at Huadu are highly satisfied with the Stäubli robots on the inline parts cleaning lines. These large six-axis machines have operated reliably for a number of years now, despite the extremely adverse environmental conditions. Wang Meng, Divisional Head of Technology: “The robots are very precise and reliable.”

News of the positive impact has also spread to other sites: 16 Stäubli HE robots are now used in parts cleaning at the Zhengzhou plant, where Dongfeng manufactures vehicles under its own brand name. In Huadu itself, more robots from the Stäubli TX series work in other areas as well, including large TX200s and compact TX90s