Luft- und Raumfahrt
Innovationen und bereichsübergreifendes, synchronisiertes Programmmanagement
SDF is one of the world’s leading manufacturers of tractors, harvesters and diesel engines. Its products are distributed under the brands DEUTZFAHR, SAME, Lamborghini Trattori, Hürlimann, Grégoire and Lamborghini Green Pro. SDF has eight production plants, 13 commercial branches, two joint ventures, 141 importers and more than 3,000 dealers worldwide.
“In the future, competition will be even fiercer, so providing continuity as well as updated products will be essential,” forecasts Francesco Cassani, founder of SDF, a leading manufacturer of tractors, harvesters and diesel engines. Cassani knew of whence he spoke: With nearly 90 years of experience, it is clear SDF has learned how to adapt to changing times and environments. The cornerstone of its operations is agility in dealing with production costs and reliability.
The agricultural equipment market is cyclical, as it depends on farm income, changing interest rates and overall farm profitability. Farmers have to strike a balance between various useful capital-intensive investments. They will challenge equipment manufacturers on robustness as well as upfront cost of agricultural machinery.
Given climate and harvest period uncertainty, downtime has a price that farmers cannot afford to pay. The level of upfront investment for agricultural machinery with the latest technologies also has a strong impact on purchasing decisions. It is only natural in this context that SDF constantly revisits its design and production costs and timeline.
Further, stricter environmental regulations on carbon dioxide (CO2) and nitrogen oxides (NOx), as well as customer interest in limiting fuel consumption, confirm that manufacturers need to constantly and quickly adapt their equipment offer. The latest European (Stage IV) and United States (Tier 4) regulations require an 80 percent cut in nitrogen oxides compared with previous levels, already down 50 percent compared to Stage IIIA/Tier 3. SDF is adjusting its FARMotion signature engine technology accordingly.
“In order to give final customers new state-of-the-art tractors, concepts like time-to-market and value-for-money are becoming more and more important for our company,” says Riccardo Bonacina, who is the base engine validation and reliability lead engineer in the research and development (R&D) department at SDF. “A critical business issue for SDF is a long development cycle that could lead to high development costs.”
One of SDF’s strategies to reduce development times and costs was to front-load product development in the design phase. It selected Simcenter Amesim software from product lifecycle management (PLM) specialist Siemens PLM Software to perform vehicle dynamics simulations and mechanical simulations as well as hydraulic and thermal circuit simulations, including on its lubrication systems, for its FARMotion engine.
“If the simulation at the beginning of the process is robust, then many functional testing loops, which are meant to improve the system, can be skipped,” says Bonacina. “To find a new solution, it only requires acting on some parameters using Simcenter Amesim and validating them during the testing phase, instead of starting the complete development phase over like we did some years ago. By using Simcenter Amesim, the development phase can be reduced significantly, up to 30 percent in some cases.”
Considering that it can take up to four years to design an entire tractor engine from concept to production, it is a great leap forward in controlling product launch planning and ensuring continuously competitive pricing.
Lubrication systems are an essential component of an engine. The systems play a fundamental role in ensuring high efficiency in fuel consumption and engine emissions as well as lowering the maintenance needs of the vehicle. Therefore, SDF continuously evaluates its traditional lubrication systems to improve the general performance of its FARMotion engine.
“We need to design a robust and durable circuit in order to comply with our customers’ expectations regarding engine reliability,” says Bonacina. “Even if the circuit corresponds to a classic lubrication system, we search for ways to optimize it in order to implement the right solution for the pump, ensure that the piston cooling jets are efficient and, ultimately, avoid any engine failure.”
To complement testing and reduce development times, the SDF Engine Validation Department switched to model-based systems engineering (MBSE). MBSE enables them to considerably reduce iterations between the design and testing phases. The department started with different simulation software, but quickly decided to change to Simcenter Amesim.“At the beginning, we performed simulations with another software and collaborated with an engineering company,” says Bonacina. “We started the development phase on the prototype engines and discovered there was a very big difference in the pressure between the initial simulations and the samples that we were testing. So we decided to start again using second modeling and verification with the 1D simulation software, Simcenter Amesim.”
Using Simcenter Amesim facilitates new component and circuit modeling thanks to its conversion functionality between 3D and 1D and the extensive library of hydraulic components. With rigorous 1D modeling capabilities in place, the SDF engine validation team was able to isolate the component that did not behave in virtual simulations the way it did in real testing conditions: in this case, the hydraulic-lash adjuster. By using Simcenter Amesim, the engineers were able to apply the precise clearance data and correctly calibrate the entire model.
Using Simcenter Amesim, SDF engineers conduct assessments of lubrication system components. They are able to diagnose loss of efficiency in the system and have gained fresh insight into the circulation of oil in the lubrication circuits. It has enabled them to design a smaller, more efficient oil pump. To validate the new pump, SDF engineers ran a series of simulations with Simcenter Amesim. It enabled them to promptly evaluate how the pressure and oil flow reacted to the new equipment.
“Thanks to the calibrated and optimized model, we had already defined the final specifications,” says Bonacina. “We can have the final tool ready without any intermediate steps. The calibrated model permits you to virtually obtain results quickly for all the matrix combinations. We only have to cross-check these components on a test bench by comparing them with the simulations. If all the validations are met, we are sure that the engine is safe in all regards.”
The tests are conducted under various conditions such as temperature and size deviation. The engineering teams also take into consideration possible size deviation of other components, such as the crankshaft or the piston cooling jet. It is indeed rare in the industry that all manufactured components are exactly the same size. Slight size discrepancy is a common condition, especially at the beginning and end of the production process. To limit the quality risk, specifications are used to define the tolerance limits for each of the components according to how they will be applied.
Thanks to Simcenter Amesim, it was possible for SDF to evaluate the impact of part production deviations on system performance by simulating minimal and maximal dimensions. These limits correspond to plus/minus three sigma during production. It even opens the door to redefining part tolerances, while still maintaining system quality requirements. Loosening tolerance specifications could translate into time and cost benefits for suppliers and internal production teams.
Tractors must contend with rough terrain and harsh conditions that can affect the engine. The acute effects of the terrain and conditions on the agricultural vehicle engine can also be used as parameters to validate the engine.
“The model enabled us to optimize the oil pump and validate it in the worst conditions,” says Bonacina. “I was able to check a very critical situation that can happen in the field, in which we reach an oil temperature of 120 Celsius, the component size deviation limit is at the maximum and the oil filter suffers clogging. After 1, 2, 3, 400 working hours, the oil filer is often blocked and the pressure characteristics are different so you have to ensure that the engine will also perform well under these conditions. The simulation can help you reach a high level of confidence in advance of testing.”
SDF started using Simcenter Amesim 10 years ago to model and simulate vehicle hydraulic circuits and dynamics. Over time, other divisions have embraced the benefits of Simcenter Amesim. The engine validation division is one of them.
“Because we have Simcenter Amesim in-house, the engineering skills remain inside the company,” says Bonacina. “Starting the creation of the model and finding solutions is quick and we are then free to modify circuits and components. We do not depend on outsourced engineering companies for every simulation we need. I appreciated the user-friendly interfaces and the flexibility. You can easily design and simulate a high-complexity system by coupling different Simcenter Amesim solutions and products.”
To leverage Simcenter Amesim to its full potential, SDF engineering teams were able to rely on the cooperation developed with BSim, a partner of Siemens PLM Software in Italy. Bonacina comments: “They are helping us in many ways to model and choose the right solution for simulation in order to have a reliable model that can provide results in less time.”
Using Simcenter Amesim for hydraulic circuit simulations (specifically, the engine oil circuit and cooling system) and mechanical simulations (specifically shaft vibrations), the SDF engine validation engineering team was readily able to target and achieve lubrication circuit optimizations.
“Thanks to all the Simcenter Amesim licenses, you can build everything that you need for your analysis,” says Bonacina. “You can upload hydraulic systems, mechanical systems and electronic systems simultaneously, and from that you can generate the results you are looking for. The flexibility of Simcenter Amesim is a key feature. You can choose many different components and the mathematics behind it is very robust.”
Building on its positive experience, SDF intends to continue to extend the use of Simcenter Amesim; for example, to simulate transient conditions to study the system warmup and pressure buildup. Other models have been developed using the hydraulic component design library, such as the pressure-reducing valve for the piston cooling jet. The extensive multi-domain libraries of Simcenter Amesim are efficient assets for modeling and design. SDF aims to fully capitalize on front-loading the design of engine systems and subsystems using Simcenter Amesim so it can keep its competitive edge.
“The requirements for time-to-market, product reliability and durability have changed dramatically over the last 20 years,” says Bonacina. “And model-based systems engineering and a front-load approach are key solutions for complying with those requirements. Without modelbased systems engineering, it would be difficult to compete.”