Machining of large-sized parts at Pilatus Flugzeugwerke: Medium-sized structural components made of aluminum are machined on a flexible manufacturing system (FMS) from the Starrag Group equipped with two Ecospeed F machining centers. Production capacity could be increased by about a third.
The final assembly hall of Pilatus Flugzeugwerke AG in Stans, Central Switzerland: There, you can feel the fascination of flying much more than when you are sitting in an "ordinary" passenger aircraft. Between the latest models of the PC-12 single-engine multi-purpose turboprop aircraft sold almost 1,600 times, some representatives of the ultra-modern training aircraft PC-21 and the three prototypes of the twin-engine business jet PC-24, which was certified in 2017 and has already been ordered over 80 times, the desire to take the joystick in hand and take off is growing. No wonder that Pilatus has conquered various niche markets with these relatively small aircraft. Because they know how to convince buyers with high quality, individual equipment and performance features as well as a global customer service worldwide that won multiple awards. With a 33 % share in sales in 2016, Europe was the largest sales market for the Swiss company, followed by America with 29 % and Asia with 20 %.
Additional capacities for machining of large parts
Sales and order intake have been rising steadily for years, and the required production capacity will reach a new peak with the market launch of the PC-24, known as the Super Versatile Jet. Since neither the premises nor the number of employees can be increased indefinitely, the decision was made reorganize the machining and to create additional capacities. After all, the new business jet, like all other Pilatus aircraft, consists of numerous aluminium structural components — from nose to the tail fin and the wing tips. "Machining these parts is one of our core competencies," explains Walter Duss, Head of the Mechanical Machining Department. "With walls of only 1.2 mm thick in some cases, these parts are extremely delicate compared to those of other aircraft manufacturers. Accordingly, the degree of chipping is usually well above 90 %." In order to increase productivity in this know-how-intensive core segment, a flexible manufacturing system should be installed for components from 750 mm to 4,000 mm in size, which enables a largely automated production process. Other important prerequisites in the specifications were the possibility of retooling during machining with a work buffer in the pallet magazine and an overall reduced retooling effort in order to be able to handle the parts range of over 200 Pilatus items of this size economically.
Comprehensive know-how and a convincing, powerful solution
Beat Müller, project manager for equipment procurement and responsible for the investment in the flexible manufacturing system, included all suppliers known in the aerospace industry in his tender. They had to undergo an intensive benchmarking process, which focused on numerous trial operations. Eventually, the Starrag Group was awarded the contract to supply a flexible manufacturing system with two identically equipped Ecospeed F 2040 machining centers.
"The comprehensive know-how in the systems business and the successful handling of complete turnkey projects that has been practiced for many years spoke in favor of the Starrag Group", argues Beat Müller. Concerning the machine, the Starrag solution was particularly convincing due to the performance of the Ecospeed F machining centers, which are specially designed for machining aluminium structural components and achieve a chip volume of up to 160 l/min. Beat Müller describes the parallel kinematic machining head Sprint Z3 as particularly innovative: "We were very impressed by the different angles of work that could be realized for pocketing. Another decisive factor was the spindle with its maximum speed of 30,000 rpm and an output of 120 kW. It offers a diagnostic function — "a must for us", adds the project manager. "This enables us to optimize the process, also in terms of maintenance and other operational costs."
Optimum chip fall due to vertical arrangement of the machine pallet
The project manager also mentions the optimum chip fall of the Ecospeed F as an important fact that spoke in favor of the machine: "We assume that the plant processes almost 700 t of raw material annually, of which over 90 % is chipped. This is an enormous volume of chips that must be removed from the machine and the production area." The vertical arrangement of the machine pallet ensures that the chips fall directly into the centrally arranged chip conveyor. It delivers the chips to a cross conveyor located in the basement, which finally transports them into a silo with four briquetting presses. After pressing, the briquettes are conveyed out of the hall into a container.
The Starrag Group's scope of supply included project planning and engineering for the entire FMS, which includes not only the machining centers but also pallet handling. A total of 16 pallets measuring 2,000 mm x 4,000 mm are included in the system, of which one each is in the machines while 14 are stored in storage stations. The system also includes two set-up stations with tilting tables for horizontal loading. A production control computer, also developed and supplied by the Starrag Group, supports highly automated production by controlling the interaction of the machine duo with the pallet and set-up stations.
High process reliability enables unmanned night shift
The Starrag FMS has been in operation since autumn 2016. Production Manager Walter Duss is satisfied: "On a similar production area and with the same number of employees, we now generate around a third more capacity. This has also made our production significantly more economical, which helps us to succeed in the tough international competition at our expensive production site in Switzerland". Project manager Beat Müller also considers a major goal achieved: "Until now, we had a shift model in which our machine operators worked continuously 300 days a year from 5 a.m. until 1 a.m. at night. This was followed by four hours of unmanned operation. Thanks to the reliable operation of the plant, we can now run unmanned shifts from 10 p.m. until 5 a.m. in the morning, thus reducing the work load on our employees and allocate them to other tasks."
Another benefit he mentions is the set-up during machining, which is done manually because of the large variety of parts. The pallets are loaded during the day shifts. In order to save time, Pilatus integrated a raw material warehouse opposite the set-up station, which provides the required raw parts for each order. The equipped pallets are stored in the magazine. From there, the Starrag production control computer automatically sends them to the machines for processing and ensures that they are subsequently returned to the magazine. Beat Müller points out that about twelve manufacturing jobs run simultaneously through the system. This ensures that the pallets are stored again even between individual work steps. Beat Müller sums up: "The buffering effect of the pallet magazine ensures that we achieve higher capacity utilization. As soon as processing is completed and capacity for unloading is available, the finished pallet moves to the set-up station, where it is manually unloaded and reloaded.”
This article was first published by Schweizer MaschinenMarkt