Replacement gears withstand high loads in use

• What was needed: Resilient special gears for repairing servomotors in the roof-mounted water cannons of airport fire engines 
• Manufacturing method: Laser sintering
• Requirements: Cost-effective, highly resilient
• Material: iglidur® i3
• Industry: commercial vehicles
• Success through collaboration: The gears cope with the high levels of stress and were used to repair additional vehicles. The company managed to avoid the cost-intensive work that replacement of the complete servomotors would have required.

Fraport AG's on-site fire brigade ensures fire safety at the Frankfurt am Main airport. Its airport fire engines have roof-mounted water cannons that use a servomotor to change the spray nozzle angle. Because the angle also changes while water is being sprayed, the load on the servomotor is considerable. After ten years of use, the gears in the cannon became worn so the roof-mounted cannons had to be repaired.
 

For repair of the roof-mounted cannons of airport fire engines, the on-site fire brigade of Fraport AG needed individual gears that could withstand the high loads.

Problem

The machined polymer gears used in the servomotor of the roof-mounted water cannon had become worn after ten years of use and had to be replaced. The manufacturer recommended replacing the entire servomotor but this was very cost-intensive. The manufacture of special gears with conventional manufacturing methods is often uneconomical and, due to the complex geometry, not always possible. 

Solution

The maintenance technicians from the on-site fire brigade of Fraport AG found an ideal solution in the SLS polymer iglidur I3: as a manufacturing method, 3D printing makes it possible to produce individual and special parts cost-effectively and quickly. Specially developed for demanding applications in machines, iglidur polymers contain solid lubricants that make them more durable and reduce maintenance work/expenditure. The printed iglidur gears fulfilled the expectations and are now used in other vehicles at the airport.  

The gears are fitted in a servomotor in the roof-mounted water cannon. This motor changes the angle of the spray nozzle.

Roof-mounted water cannons of airport fire engines must cope with intensive stress when spraying water.

Frankfurt airport is the largest airport in Germany.  Internationally as well, it is one of the leading airports in Europe for passengers and cargo traffic.  With around 81,000 employees in approximately 450 companies, the biggest local worksite in Germany and a magnet for other companies in the economically important Rhine Main area.  Given the high density of aircraft, utility vehicles and private cars, there is always something for the airport fire brigade to do. In order to comply with the legally prescribed response times, the fire brigade must be able to reach anywhere on the apron within three minutes. The personnel and technical equipment of the three fire stations on the airport grounds are correspondingly important.
 
The more than 115 fire brigade vehicles on the grounds of the airport include fourteen fire-extinguishing vehicles.  With their roof-mounted water cannons, they can spray at least 5,300 litres of water over a distance of 80 metres in a single minute. Accordingly, the load on the servomotors of these cannons is very high as they control the height of the water jet by changing the angle of the nozzle.  

As the height is changed while water is still being sprayed, the load on the gears is considerable.

Printed gears made of iglidur I3: being successfully used in airport fire-extinguishing vehicles

Two special gears made of robust plastic are built into the servomotor. After ten years of use, they were worn that required maintenance on the roof-mounted water cannons. The vehicle manufacturer suggested to the maintenance technicians that the entire servomotor be replaced but this would have been costly. Instead of replacing the complete servomotor, which was otherwise fully functional, the design engineers decided to try out a new approach: after internet research, they discovered the option of durable gears made by igus with the 3D printing method and decided to test the wear-resistant iglidur I3 plastic. Gear design was done with the freely available online CAD configurator. This allows templates for 3D printed gears to be created quickly and easily.

Manufacturing with the SLS method took less than three days, which meant that the fire brigade could quickly start testing the new gears. The tests showed that the iglidur I3 gears were well able to withstand the high loads placed on them. The maintenance technicians were then able to order gears for additional vehicles. Extremely pleased with the material quality and the fast service, they immediately asked that an additional component to control the pneumatic airport fire engine doors be printed and tested. This printed application also fulfilled the requirements and is now being used by the fire brigade fleet at Frankfurt airport.

For the 3D printing of gears, there are hardly any restrictions as regards the geometry. With our 3D printing service, gears in quantities from 1 to 10,000 can be printed cost-effectively in 1 to 3 days.

Why print gears made of iglidur I3?

The iglidur materials specially developed for the manufacture of moving machine parts are characterised by very high abrasion-resistance and the solid lubricants they incorporate. They are used for the production of components by means of injection moulding, additive manufacturing and machining of bar stock. iglidur I3 was developed as polymer powder for manufacturing parts with the laser sintering method and is characterised by its high wear-resistance and strength. It is not for nothing that this material is the undisputed best seller among the igus 3D printing materials.
 
Thanks to its mechanical properties, iglidur I3 is especially suitable for spur gears and helical-bevel gears as well as for all other gear shapes. iglidur l6 is only recommended for 3D printed worm wheels, as this polymer was developed for enhanced sliding ability. How long a printed gear made of iglidur I3 will last according to the application parameters entered can be determined online in the gear service life calculator quickly and easily. The very long service life of gears made of iglidur I3 compared to normal plastic gears has been tested and proven in our test laboratory.  
 
One of the great advantages of 3D printing as a method of manufacturing gears is the flexibility regarding the geometry of the tooth root. The tooth root radius can be optimised and the service life of the gear improved. In the case of mechanical manufacture, such optimisation is not usually possible due to the tool size. In order to design gears directly with the optimised tooth root, we recommend our free CAD configurator.