Creaform, a company specializing in the development and manufacturing of portable 3D measurement technologies as well as in 3D engineering services, completed this project. The customer was Nova Bus, a major urban transit bus manufacturer in the North American market.
The project consisted in inspecting the actual state of a vehicle rear chassis, and comparing it to the mounting points of the radiator. The task at hand additionally involved assessing the extent of deformations the chassis was going through during the installation phase.
Nova Bus was looking for a reliable and efficient metrology solution that could seamlessly integrate with its own process. The buses needed to be inspected directly at the Nova Bus premises, on the assembly line, which raised the challenge of setting up a stable measurement system. This requirement eliminated systems such as laser trackers and digital measurement arms from the start, since these were too sensitive to movement, vibrations, or temperature changes. Some key elements further complicated the project: for instance the inspection had to be done above the ground, with the help of lift platforms, due to the fact that one of the measuring zones was located on the roof of the bus. Additionally, the assembly line had to be stopped during measurements.
The selected measurement device thus had to be portable and compact (since the only available space was on the lift platform), as well as capable to acquire data very quickly, in order to minimize the assembly line downtime.
TRUaccuracy Technology and Creaform Dynamic Measurement Function
Because of all the specific requirements of this project, the Creaform team –consisting of metrologists and application engineers- suggested that Nova Bus used a system including a HandyPROBE portable armless CMM and a MetraSCAN 70 portable optical CMM scanner, among other things because it offered dynamic measurement as an undeniable benefit. This crucial feature would make it possible to obtain the bus chassis measurements directly from the assembly line, without impacting accuracy whatsoever, even in the presence of vibration or changes in the environment.
As such, the dynamic reference mode makes it possible to lock the coordinates system directly on the part to be measured, in order to maintain the part alignment throughout the probing and scanning process.
Key Steps – Bus Rear Chassis Inspection
- Defining the mandate (general and local reference systems, surfaces to be inspected, results formatting);
- Installing the measurement system on the vehicle, on the assembly line (outside of production hours);
- Taking measurements with the HandyPROBE portable CMM and the MetraSCAN 70 optical CMM scanner;
- Repeating the measurement process on five vehicles;
- Analyzing the data in three steps:
- Analyzing variations related to the radiator mounting points hole pattern (relative localization tolerance [FRTZF] according to the ASME Y-14.5M standard);
- Through colorimetry, assessing the geometric variations of the rear chassis according to the mounting points of the radiator (CAD model, adjusted on the radiator mounting points only);
- Through colorimetry, assessing the distortion of the installed rear chassis, when compared to its theoretical form, but without taking the impact of the radiator mounting points into consideration (local alignment assisted by the rear chassis CAD model).
In this specific case, the Creaform technologies enabled Nova Bus to complete its inspection phase (including scanning and data processing) in only two weeks. This way, the manufacturer was able to meet the predefined deadline for the project, and to continue development without incurring measurement-related delays.
Nova Bus stated that “the Creaform technologies proved to be efficient, quick, versatile and flexible. Moreover, the Creaform expertise made it possible to optimize the response time, and the deliverables (measurement and colorimetry reports) were entirely satisfactory. I also want to underline the support and availability demonstrated by the Creaform team, which greatly helped us define our actual needs”.