Aug 1, 2017 | By Tess
Poland’s first supercar, Arrinera Hussarya, has been a symbol of a rejuvenated and reborn automotive industry within Poland. As we’ve already seen, the supercar’s development has been a rigorous process, largely enabled by the adoption of new manufacturing technologies such as 3D scanning and 3D printing.
Unlike most contemporary Polish automotive projects, Arrinera Hussarya is built from the ground up. That is, the supercar’s body, engine, and interior have all been redesigned to not only meet the requirements necessary for a high-caliber car but to also represent the aesthetics worthy of a supercar.
Reverse engineering helps reduce production costs
As one could imagine, redesigning a supercar is not only time-consuming but also extremely costly, and Arrinera’s engineers have continually been searching for ways to both accelerate the development time of the car and reduce its costs. Through this effort, the team decided to use reverse engineering, the process of reconstructing the technical documentation of an existing element in order to re-design it.
To reverse engineer the car’s parts, the team used a SMARTTECH 3D scanner to precisely capture the geometry of the car parts. The 3D scans enabled them to compile comprehensive information and data about the car parts to be redesigned. Let’s take a look at how the engineers designed and manufactured a new clutch housing with the help of 3D scanning.
A sports clutch (the device that engages and disengages the car’s power transmission) is a totally different breed from a clutch in a regular car, as it is subjected to completely different types of pressure. An 810 Nm torque requires the use of not only a reliable but also lightweight clutch design. As the engineers explain, the 3D scanner made it possible to capture the technical features of an existing clutch housing, allowing them to redesign and adapt it using CAD software to meet the measurements and requirements of the supercar.
Green light 3D scanning
A MICRON3D green 3D scanner with a 10 megapixel detector was also used to capture measurements of the car parts. The scanning technology, based on a green LED light, allows for measurements 30% more precise than 3D scanners that use a white light. With a field of view of 800 x 600 mm, the 3D scanner obtains a point cloud representing the scanned shape with 0.084 mm accuracy.
In practice, these numbers mean that with a single measurement you can scan an area equal to 80 x 60 cm. Additionally, because of the scanner’s permanently calibrated measuring volume, the device does not need to be calibrated before every use.
3D scanners as metrological devices
The measurement performed by a SMARTTECH 3D scanner is based on the projection of patterns on the measured surface. The patterns deform depending on the curvature and are recorded by a detector integrated in the measuring head. The device measures only the surfaces that are visible to the detector. In order to obtain comprehensive information about the geometry from every angle, the object needs to be scanned using a rotary stage. The load capacity of the rotary stage is over 300 kg while its diameter is 50 cm, which is sufficient to perform complete measurement of most car parts.
The image from the detector is then converted into a point cloud thanks to a special software algorithm. Each of the points contains information about the geometry described in the X, Y, Z coordinates, which after post-processing can be used for quality control or—as in the Arrinera’s case—to redesign and mill the model on a CNC machine.
Depending on the resolution, the point cloud from a single measurement can consist of 5 or 10 million points for a resolution of 5 or 10 megapixels, respectively. The number of megapixels affects the extent of detail obtained from a given object. In the Arrinera’s case, a 3D scanner with a 10 megapixel detector was used since there was a need to accurately reproduce the edges of the measured object.
The clutch housing, for its part, was scanned from two sides, which allowed the engineers to obtain two point clouds. For each point cloud, there were six individual measurements. Using a rotary stage integrated with the 3D scanner the individual measurements were preliminarily aligned.
Aligning point clouds using SMARTTECH3Dmeasure software
After the scanning process was complete, it was possible to convert the point cloud into a triangle mesh using the software SMARTTECH3Dmeasure, which is provided with every SMARTTECH 3D scanner. Before the conversion, however, the team first needed to align the measurement results.
For this, they used a three-point method where three common points were selected for both point clouds. Based on this, the software automatically determined the clouds’ position to one another. The goal was to obtain a point cloud completely representing the scanned object. The use of a rotary stage significantly simplified the operation of the alignment of the results because it divided it into two groups of points representing each of the sides.
The team then used the Global alignment function, which precisely aligns all the point clouds to one another based on the position of the points. At this stage, the team also removed the overlapping areas of different measurements.
After these operations, the point cloud was then converted into a triangle mesh. For Arrinera, the STL format was chosen. The triangle mesh can also be used as a base for CAD modelling. Arrinera made and adjusted the CAD model and then sent it to software operating a CNC machine.
Scanning large objects with positioning markers
3D scanning on a rotary stage in a measurement laboratory isn’t always possible due to the size of the object. In such situations, measurements can be made on the production line thanks to an alternative method that uses positioning markers. The second example given by Arrinera uses this method.
The Arrinera engineers were faced with a challenge: the left sill of the car was adapted to optimize the structure and in order to maintain the symmetry of the vehicle, and the sill from the other side had to be made in exactly the same shape. The conventional measuring methods used by Arrinera did not allow it to obtain the full geometry and that is why it was decided that the SMARTTECH 3D technology would be used.
The geometric data of the existing sill was collected directly from the physical prototype. Arrinera Hussarya stood on a platform, but access to the sill was hindered by the car door. Because the sill’s dimensions were much larger than the field of view of the 3D scanner, it was necessary to use a scanning function with positioning markers.
The measurement method using markers relies on attaching special positioning markers on the scanned object. The SMARTTECH3Dmeasure software finds five common positioning markers between two individual measurements and then aligns them. The 3D scanner operator is provided with full view of their work and can easily add scans of the remaining parts of the sill. The sharp angle between the projector and detector enabled the Arrinera team to obtain a large amount of geometrical data.
The result of 3D scanning with positioning markers is a preliminarily aligned cloud point. The post-processing in SMARTTECH3D software is done similarly every time because of its intuitive design and ability to automate individual operations. In this case, it was also necessary to create a reference CAD model in the Geomagic Design X, which was used by Arrinera. This model is compatible with cutting and bending machines that make the car parts.
Having a CAD model of a given element also enabled the use of 3D printing technologies for rapid prototyping. For its 3D printing needs, Arrinera chose the Poznan-based company OMNI3D, whose flagship product Factory 2.0 Production System creates large format 3D prints using FFF (fused filament fabrication) technology.
OMNI3D printed parts for the Arrinera supercar including its mirror housings and intakes in the 1:1 scale. It allowed the supercar’s manufacturer to use parts made from ABS, in addition to simple rapid prototyping. Thanks to the use of the 3D printer, Arrinera was able to reduce the parts’ weight, which is particularly important in a supercar where mass is one of the crucial components when deciding whether to install a particular element.
Designing and building a race car is not only an engineering feat but also a financial challenge. The 3D technologies provided both savings in costs as well as the required precision during the data acquisition, prototyping, and production adjustments. Thanks to the use of 3D technologies, Arrinera was able to significantly accelerate the prototyping process and reduce the time required for the car’s production.
Posted in 3D Printing Application
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