E-gearbox for trucks … and E-sports-cars
The multinational FPT Industrial is a renowned manufacturer of gearboxes especially for trucks and agricultural equipment. In 2023, the company expanded its portfolio to include the drive train of an all-electric sports car at its plant in Turin. The components are finish-ground on a KX 300 P gear grinding machine from KAPP NILES. The KNM 5 X measuring machine utilized to monitor and confirm part quality was also supplied by the Coburg-based KAPP NILES group.
Is a company specialising in drive trains for utility vehicles also capable of developing and producing gearboxes for an all-electric sports car? Absolutely, FPT Industrial is proof of that. "After all, motion transmission always takes place between shafts and gears", explains Roberto Di Geronimo, Competence Leader Gears & Gauges. Over the years, he has seen many gearboxes developed and helped them progress to serial production, but the gearbox for an all-electric Italian sports car was new territory both for him and FPT Industrial.
from left to right Chiara Crosta, Roberto Di Geronimo and Frank Holzheid
The company belongs to the Iveco Group and specialises in drive train solutions for on- and off-road vehicles as well as marine and power generating applications. In addition to six engine platforms, the product range includes gearboxes with a maximum torque of 500 Nm, along with front and rear axles of a gross axle load up to 32 t – sophisticated technical solutions, to be sure, but designed for utility vehicles.
What FPT does have experience in is e-mobility: The company's own ePowertrain business unit is devoted to electric drive trains, battery packs and battery management systems. Manufacturing the sports car gearbox presented requirements which could not be met with their existing machines. After evaluating multiple suppliers, FPT decided to go with their trusted partner, KAPP NILES.
Microscopically small but crucially important: Surface structures
FPT has been working with KAPP NILES for a long time. Locally, KAPP NILES is represented by our Italian subsidiary Bitek. Eight KAPP NILES KX 1 machines are used for non-dressable generating grinding at the Torino location. For the sports car gearbox, the company decided to purchase a KX 300 P generating grinding machine.
The KX 300 P grinds workpieces with a dressable corundum grinding worm but can also be used with non-dressable CBN grinding worms or profile wheels. Parts can be loaded manually or automatically. At the Torino plant, they decided to minimise loading times with an automatic version equipped with a ring loader. Another special advantage of this machine is topological profile grinding, which requires a bit of explanation.
First, why the switch to ceramic generating grinding? "Surface has a different structure, in conjunction with KAPP NILES structural shifting on the KX 300 P, I believe the gearbox will be much quieter", explains Di Geronimo. For electric utility vehicles like Iveco Daily trucks, noise emission standards are less strict. The effect is also less noticeable, since the transmission input speeds only reach about 6,000 rpm. The sports car gearbox, however, will experience speeds of up to 18,000 rpm – three times as fast.
Even better than generating grinding: topological generating grinding
Compared to profile grinding, generating grinding offers much faster grinding speed, combined with excellent quality. As a rule, gears are ground with crowning. Due to the process, small deviations from the theoretically required tooth flank geometry occur. In technical jargon this is called bias. For technological reasons, conventional generating grinding produces gearing in which the profile is only perfect in the middle of the face width.
Frank Holzheid, Manager Sales & Service at Bitek, provides some background information: "Typically, with conventional combustion engine transmissions, only the profile in the middle of the gear was relevant as a quality criterion. The natural bias produced by this method at the ends of the gear face can cause the gearbox to be somewhat noisier. This is masked by the much louder noise of the engine, so it makes no difference, but electric vehicles are a different story. At slow speeds, the transmission noise is much more noticeable. So, the gear and counter gear must be precisely adapted to one another, even in the bias. The way we achieve this is with topological profile grinding.”
Di Geronimo goes on: "Normally, we only check the involute in the middle of the tooth width. For the sports car, there are three planes: the profile in the middle and two others at the start and at the end of the face width, as well as three planes for the flank line of the gear.”
Collaborative development
Various suppliers offer well-developed and reliable machines. For Di Geronimo, this was not the only factor to consider. He explains: "What is equally important is service, spare parts availability and how well the manufacturer understands our processes". Chiara Crosta, Administration Manager Sales & Service at Bitek, adds: "For FPT, it was important to have a turn-key solution.” Di Geronimo also closely analysed the manufacturing process itself. This includes grinding and dressing times as well as the fastest possible retooling between two different workpiece types. All of this has to be considered when calculating the cost per workpiece.
Another key criterion: development. KAPP NILES assisted FPT from prototype to series production. Di Geronimo: "We put the gearbox through long trial runs with the Development Department. Based on these tests, there were requests for changes to the process and the tools which always had to be implemented as quickly as possible. To help me with this, KAPP NILES provided me with a contact person that I could reach any time, even weekends when it was urgent. In no time at all, we had a new batch of prototypes ready to take to the test bench. KAPP NILES helped us a great deal during the prototype phase of our project to develop an all-electric super sports car gearbox. They were a perfect partner to work with throughout.”
Holzheid adds: “Mr. Di Geronimo also paid multiple visits to our main plant in Coburg. We have a machine there that we've set aside for tests and a specialist from the Technology Department who is assigned to work with FPT.”
The process was optimised down to the most minute detail, – for example, the helical gearing. Normally, the coast and driving flanks have the same helix angle; in this case, 30°. When we tested the combination, though, it was too loud. Adjusting the coast flank angle by a mere 0.08° made a significant improvement. Holzheid: “This requirement came up in the prototype phase. We adjusted the technical data, and it had the desired effect on the test bench. Differing helix angles on both flanks are nothing out of the ordinary with EV transmissions, and our machines can handle that with no problem.”
As important as production: the measuring equipment
In addition to the generating grinders, FPT also uses a KAPP NILES measuring machine, the KNM 5X. The machines of this series are specially developed for medium-sized workpieces. Wear-free and friction-free air bearings in linear and circular axes, large bearing gaps and wide guideway cross-sections ensure precision, maximum accessibility and extreme durability. Linear motors are used in all the feed axes. Rotary tables with air or hydrostatic bearings are equipped with direct drives. Controlled air springs under the base plates absorb shocks and vibrations and allow the measuring machines to be used close to production.
The final argument in favour of the purchase was the closed loop process: The measuring and correction data are automatically transmitted directly to the gear grinding machine via the GDE interface. No need to waste time manually transferring them with a measurement log from the metrology lab. This makes it possible to very quickly obtain insights into the stability of the process during series production. In particular, it makes it possible to spot trends (i.e. very gradually increasing deviations) early on and make corrections as necessary. This is especially advantageous with gears for electric drives, which have extremely tight tolerances. Crosta: "Mr. Di Geronimo immediately saw that he could also use this for other products. That's what sold him".
In fact, this was an investment in FPT's production as a whole: The largest gears of the sports car gearbox have an outside diameter of 250 mm. But the product range also includes drives for an electric truck, a joint venture between FPT and a manufacturer of electric commercial vehicles. It features gears with an outside diameter of 600 mm. The measuring machine is designed for diameters of up to 650 mm.
On the subject of metrology, Di Geronimo brings up another feature he finds useful: "In addition to our closed-loop technology, it is also possible to measure directly in the generating grinding machine; that saves additional time, especially when we're changing the machine over to a new component.” A measuring probe can be used immediately after tooling and grinding the first part to check whether the profile and lead are correct. This saves a trip to the metrology lab and cuts down on wait times. Holzheid explains: "It's not a replacement for a measuring machine, since there is always oil or small particles in the working area that can cause deviations of a few microns. But for set-up, the precision is absolutely good enough, and it saves us a lot of time.”
Zero-error tolerance
The combination of the right machine, grinding method and measuring method create ideal conditions for smooth production, but human error can still occur. That’s why KAPP NILES has provided very effective measures against operating errors. Besides the closed loop mentioned above, RFID tagging of tools and accessories is another one of them.Di Geronimo enjoys this feature, as he explains: "In the machine control system, there is a list of accessory parts for each workpiece. If I want to set the machine up for this product, I can identify each part with a scanner. The error rate drops to zero.” Accessory parts can include cylindrical worms, dressing tools, clamping fixtures, tailstock centres, cooling lubricant nozzles and gripper jaws for the ring loader. If the operator makes a mistake, the machine detects that there is a part which does not match the workpiece and will not start.
Holzheid adds: "We can do even more with this system. The built-in RFID chip – the one on the dressing roll, for instance – lets you monitor how many dressing cycles this tool has completed so far. The machine warns you if the tool is approaching the end of its service life and needs to be replaced soon.”
Finally, the safety concept also incorporates the poka yoke principle. This is based on the idea that, while errors can never be excluded entirely, most of them can be avoided with simple technical preventive measures. For example, a contour screen is installed at the inlet of the ring loader to check the outer contour of the workpiece.
However, this simple precaution is not effective for workpieces which have the same basic geometry, just with opposite helix directions. The grinding process would start, and the machine could potentially be damaged. Di Geronimo did not want to take this risk and asked for a solution. Holzheid describes what KAPP NILES came up with: "Normally, just one alignment sensor is used to identify a gap in the gearing in order to position the workpiece correctly in relation to the grinding worm. We simply installed two sensors in order to make certain that the machine could correctly identify the helix direction.”
Cutting-edge technology for a hightech car
The Italian super sports car has been on the market since the summer of 2023. Three permanent magnet motors built into the front and rear electric axles provide the car with up to 761 PS and accelerate it from 0 to 100 km/h in 1.9 s; the top speed is 325 km/h. It's a technological achievement that would not have been possible without the excellent collaboration between FPT and KAPP NILES.