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SPINDLE FOR THE ROBOT CELL Passenger to freighter retrofitting aircraft

Sep 27, 2021

The robust demand for converted freighters has been driven by a strong cargo market, a silver lining for the airline industry during the coronavirus pandemic. The scarcity of passenger-jet belly size and flourishing e-commerce has furthered the freighter market. However, an aircraft conversion is technically very complex. Reinforcing the floor structure of passenger aircraft to accommodate heavier payloads is one such labour-intensive process that involves drilling thousands of holes. This case study talks about how the spindle for the robot cell that comes from Zimmer Group came to the rescue of Helios Applied Systems and also supplied a storage station for the wooden shank tapers.

The coronavirus pandemic has disrupted supply chains worldwide, paralysed production lines and led to metropolises worldwide being in lockdown. The economy has been in a state of emergency for over a year. The airline industry has been hit particularly hard. Thousands of flights have been cancelled, in some cases entire fleets of aircraft have been parked and mothballed – air traffic has been affected worldwide on an unprecedented scale due to the corona crisis.

The measures to contain the corona pandemic are affecting not only passenger traffic but also airfreight (including airmail), because passenger aircraft actually transport a large proportion (about 50%) of airfreight. Profiteers of the current crisis are cargo airlines/mixed carriers (freighters and PAX aircraft) and charter airlines, which are very likely to look back on record results in these times. Driven by the air cargo boom and the growth of online trade, the need to convert unused passenger aircraft into freighters is, thus, increasing. This is described by the term ‘Passenger to Freighter’ (P2F). Based on the current market, analysts expect growing demand in this area. In addition to opportunities for aircraft manufacturers, maintenance companies, airlines and leasing companies also benefit from the conversions.

Complex aircraft conversion

However, an aircraft conversion is technically very complex. It requires highly skilled technicians and a multitude of parts whose processing must be synchronised to ensure a smooth process and timely completion. Only a few years ago, many work steps were carried out manually, but today, even in the aircraft industry, more and more so-called Maintenance/Repair/Operation (MRO) processes are being automated. Reinforcing the floor structure of passenger aircraft to accommodate heavier payloads, for example, is one such labour-intensive process that involves drilling thousands of holes. This is where the aerospace division of Singapore-based ST Engineering Aerospace, an aircraft conversion specialist, relies on the support of a robotic cell. For this purpose, the company has been working with Helios Applied Systems, also based in Singapore, since 2019 to automate such complex processes.

Colleague robot helps

The robotic cell drills dozens of holes in the floor grilles of Boeing’s 767-300ER aircraft at STE Engineering’s plant at Paya Lebar, Singapore to convert it into a cargo plane in accordance with Boeing’s STC*. To do this, the robot cell moves along the floor structure so that the robot can drill the corresponding holes according to a predefined plan. The cell is located in a hangar that is conveniently adjacent to the converted aircraft. The robotic cell consists of a hydraulically liftable, movable platform, a Yaskawa robot with a payload of 180 kg, a special image processing system developed by Helios and a high-frequency spindle with six kilowatts and a hollow shank taper (HSK) for fast automatic tool change.

One spindle makes the difference

The air-cooled spindle of the HFL145 series, which has a nominal torque of 4.9 Nm and a maximum speed of 24,000 rpm, was supplied to Helios, complete with all the necessary cables and with a frequency converter. This is particularly suitable for precise positioning tasks with integrated safety technology (STO) and for operations at low or high speed. In addition, the inverter offers optimum performance or power yield with perfect matching of spindle and frequency inverter.

In order to be more flexible for future applications, the spindle was mounted directly on a semi-standard tool changer (ROB000117 - also from Zimmer Group). The HSK tapers and tools themselves were provided on site by Helios. Helios uses the Zimmer spindle with a fieldbus connection (EtherCAT) and also received the complete parameterisation from the automation expert from Rheinau.

Successful cooperation

“Due to the rigid construction and the very smooth running of the spindle, even at higher speeds, the drilling result is very good. You have to consider that these parts are light and not completely flat, so the vision recognises the position and angle of each hole,” says Sunil Raibagi, Project Manager & Vice President – Business Development & Strategy, Zimmer Group. The customer, Helios is also satisfied: “We appreciate Zimmer Group as a long-standing partner and are convinced of the qualities of the spindle. The smooth, no-vibrating spindle we could mount a camera on EOAT which is a success of a project.

Busy in the future

While the robot is currently focused on drilling floor grids, the STE Engineering team is working with Helios to program the machine so that it can also be used to set countersunk rivets. “We believe the robots can handle these types of processes well,” said Hui Fung Lee, SVP and Head of innovation & continuous improvement, ST Engineering Aerospace.

In the coming months, the robot will also be programmed at STE Engineering to perform other functions and work on other aircraft models, including Airbus freighter conversions. “We know that the P2F process is very complex, and many people are needed for the whole conversion process,” Lee explains and adds, “Therefore, we are constantly looking for ways to improve our productivity.” Tasks that lend themselves to automation tend to be standardised and very repetitive, he further conveys. Starting next year, ST Engineering plans to automate the drilling of floor grilles for the A321-200P2F conversion programmes it owns through EFW, a joint venture with Airbus.

Courtesy: Zimmer Group

Image Gallery

  • The robot cell moves along the floor structure so that the robot can drill the corresponding holes according to a predefined plan

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