Making large individual products with precision and accuracy; that is the challenge facing Finland-based company Wärtsilä. The company designs and produces controllable pitch propellers for the commercial, military and super-yacht market. These are unique products, the first design of which dates back to 1903. Controllable pitch propellers are custom-designed for each ship and in turn they form part of a custom-designed propulsion system that includes the rudder, gearbox, and engine. It's a solution tailor-made for each vessel, that starts with the control system on the bridge and ends with the propeller.
ABB IRB 6600 robot milling and grinding propeller blades for Wartsila.
The manufacturing process is very demanding. It starts in the foundry where a block of high-density Extruded Polystyrene (EPS) is milled using a large ABB industrial robot (IRB 6400). This profile is then used to produce a sand copy of one half of the propeller blade.
The two halves are then clamped in a metal frame, into which “cunial” — a copper-nickel-aluminum bronze is poured and the casting is left to cool for several days.
The individual blades are then transported to another part of the factory where they are ground and polished using two ABB robots on linear tracks. The previous manual grinding was tedious and it was difficult to ensure that the requisite amount of material was consistently removed.
Robotic automation is ideal for customized design. The blades are curved, so a 5-7 axes robot has to be employed. Robots are ideal for these types of application since no two solutions are the same.
The grinding process automatically accommodates progressive reductions in the depth of the grinding material. The pressure is controlled, together with the robot feed or speed. This process is complex because of the different angles and material stock. The milling process will typically take six hours. Grinding cycles depend on size, but eight hours is a typical figure. In addition some manual work is needed. The grinding process is done two-up so the robot line will typically produce four blades a day.
Robots crucial to keep production capacity. The IRB 6400 robot has been operational since 1999 and the second robot (IRB 6600) was added in 2008.
André Janssen, Manager Manufacturing Technology & Tools at Wärtsilä: says “We gained a lot of automation experience with the first robot and the second was needed to increase our production capacity. The new model employs an electric high-frequency motor instead of hydraulics and this allows tools to be changed using a standard HSK tool adaption system, as in a CNC (computer numerical control) system.
An additional robot (IRB 6640) was installed for manufacturing EPS patterns. Blade profiles are generated automatically and translated into instructions for the robots. A computer system is used to take inputs from the CAD/CAM system and translate them into robot instructions. The robots can be programmed to grind and polish the same blades or those of different propulsion solutions. The process complies with ISO-484 manufacturing tolerances.
“Because of the complexity of the blade shape robots are the only way we can meet our production schedules,” says André Janssen. “Our order book is full and to meet the demands of our worldwide customers we run the production line 24 x 7 with minimal downtime.”
Wärtsilä is a Finnish company whose roots date back to 1903. The company offers reliable, cost-effective solutions for all marine power and propulsion needs. The company markets power plants and ship power systems with propulsion solutions having controllable and fixed pitch propellers. Wärtsilä has 130 locations in 75 countries around the world. There are 900 employees at the Delivery Center Propulsion factory in Drunen and a total of 17,500 worldwide.
They have delivered more than 10,000 propulsion solutions and are the market leader in this sector. Wärtsilä works closely with the owner of the ship and the yard in order to ensure that the propeller delivers the optimum performance in all operating conditions.
ABB (abb.com) is a leader in power and automation technologies that enable utility and industry customers to improve their performance while lowering environmental impact. The ABB Group of companies operates in around 100 countries and employs about 175,000 people.
About ABB Robotics
ABB Robotics (abb.com/robotics) is a leading supplier of industrial robots – also providing robot software, peripheral equipment, modular manufacturing cells and service for tasks such as welding, handling, assembly, painting and finishing, picking, packing, palletizing and machine tending. Key markets include automotive, plastics, metal fabrication, foundry, electronics, pharmaceutical and food and beverage industries. A strong customer focus helps manufacturers improve productivity, product quality and worker safety. ABB has installed more than 175,000 robots worldwide.