comil logo01

Comil Ônibus Reduces Distortion by 75% Using Weld Planner Simulation Software

Welding & Assembly
Ground Transportation

Simulating the steel welding sequence using Weld Planner software significantly reduced manufacturing cost and time. The simulation results allowed us to control the dimensions of critical parts and avoid rework in our assembly line.

André Luis Petry
Engineering Supervisor/ Comil



Comil Ônibus S.A., a Brazilian company, manufactures buses that can be seen on the streets of more than 30 countries. It has a complete line of vehicles that include coach, urban, micro, and special buses.

One particular Comil bus design incorporated a front door with an inner structure made of steel; a configuration intended to be compliant with the ABNT NBR 7008 standard. The different components of the door were to be assembled and welded by Gas Metal Arc Welding (GMAW). Comil’s prototyping department was in charge of developing the welding device and the welding sequence.

Fig. 1: Comil’s Versatile vehicle and its door frame.

In order to develop the welding process, the prototyping team had to perform physical tests and use trial-and-error to optimize the welding device and welding sequence. Such iterations were both time consuming and costly. Moreover the tests consistently revealed excessive welding distortion (up to 20mm) and consequentially led to the rejection of the bus’ front door inner structure on the basis of inadequate quality. The absence of a Computer Aided Engineering (CAE) tool capable of predicting the behavior of the assembly during the welding process prevented a structured corrective approach to design improvement. Through trial and error, Comil could only rely on experience to modify the welding sequence and clamping positions; a method too costly to sustain. In addition, the only way to deal with distortions out of design tolerances was to perform mechanical operations – applying forces and displacements in such a way as to compensate for welding distortions.

Fig. 2: Local deformation of the welding assembly. Before the use of Weld Planner (left) and after the use of Weld Planner (right).

Comil implemented Weld Planner in three phases

  • In the first phase, ESI developed a benchmark for Comil to demonstrate Weld Planner capabilities and show the correlation between numerical and test results. The correlation was impressive enough to convince Comil to acquire the software and start deployment.
  • In the second phase, Comil became familiar with the software through a formal training program and launched their first project and the task of integrating CAE simulations into their welding process development workflow. Comil started to simulate a family of welded assemblies and compared the numerical results with existing physical tests. Through a process of progressive calibration they reached satisfactory correlation.
  • The third and most significant phase required full integration of Weld Planner in Comil’s workflow, and consistent use throughout their welding process development. Quickly, Comil was able to make decisions based on numerical results.

Before initiating the new process the welded bus door frame was distorted by as much as 18.9 mm. It was so bad that it was not possible to assemble the door panels without mechanically reworking the structure. After the optimization of their welding plan, using Weld Planner, the maximum distortion was reduced to 4.7 mm; a 75% reduction. Comil was then able to trim the welded bus door structure without any compensation or rework.

Based on success in the first study, Comil started to implement a standard methodology that integrated the use of Weld Planner to support the design of mockups for welded components and to define welding sequences. Integrating simulation has empowered Comil to reach its targets for cost, quality and product launch timing.

Weld Planner brings great benefit in dimensional distortion control of welded structures, allowing the study of different welding sequences. Results are fast and highly accurate, ensuring significant technological improvement for our company, and consequently reducing costs previously spent on prototypes and materials that were just scrapped when they didn’t meet specifications.



Thiago Sotilli
Corporate Engineering/ Comil



About Comil Onibus

OMIL Ônibus S.A. is a major bus manufacturer in Brazil and present on the streets and roads of more than 30 countries. It has a complete line of vehicles that includes coach, urban, micro, and special buses produced through careful market research. Over 28 years on the road, COMIL has worked to improve the everyday life of people with transparency, integrity, and much passion. And this is our main motivation: passion in doing, innovating, and growing. New processes and technologies are constantly being implemented. Specific models are developed according to market needs. Attention to every detail makes COMIL vehicles stand out as unique. With solid technical expertise and periodic evaluations of products and services, we work with a total focus on quality and because of this we invest in people. We believe that the joining of competencies, talents, experiences, and knowledge result in a quality product, and ensure the satisfaction of passengers, drivers, and fleet owners.

All this because our primary goal, besides producing buses, is to offer intelligent, profitable, perfect fit transportation solutions for our customers.

For more information visit Comil