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BIKE FRAME PART 3D SCANNING - Reverse engineering of frame part for bike manufacturer

LeaderFox is a reliable and well-known bike producer with wide portfolio of mountain, road, city urban, trekking and e-bikes and few more special ones.


The aim of this project was to prepare 3D data for manufacturing of new bike model, specifically the connecting element from cross-country bike. This element is used to connect the rear shock absorber and the rear structure wheels, being attached to the seat tube. Everything is then used to transmit the rear wheel suspension to increase the riding comfort of the cyclist.


For scanning of this part was used KSCAN Magic which enables us to get digital data with accuracy 0,02 mm certified according VDI/VDE 2634 Part 2 and very high resolution of 0,01 mm.


Here is the workflow which we followed in this project:


  1. Reference points (markers) placement

  2. Scanning with KSCAN Magic

  3. Postprocessing of scanned data

  4. Measurement and reporting


1. Reference points (markers) placement


As we are using portable laser 3D scanner, fistly we need to place a reference points which gives coordination to the scanning software to build a point cloud of scanned data in correct relative possitions. Reference points are actually small removable (can be also magnetic) stickers with reflective surfaces, which are shipped with each unit of the 3D scanner . There are two different sizes in each package: 3 mm and 6 mm. Because we were scanning relative small part, we decided to use the smaller diameter and placed markers with golden rule that at least 4 markers must be visible for 3D scanner in the scanning field.


Time needed: 1 minute



2. Preparation and scanning with KSCAN Magic


Scanning itself with a portable laser 3D scanner is a very fast process. The movement of the scanner occurs to gradually collect data. The scanner moves so that data is scanned from multiple angles, for their completeness. If the data is complete, the object is placed in the next position or more positions to scan the remaining parts. In this case we used small reference points (3 mm) also on sides so we could move smoothly from top side of the part to the bottom. Although the laser scanner can be easily adapted to the scanned surface, to increase the quality of the scaned data, the surface of the object was prepared by AESUB spray. This was followed by warming the room and components to a stable temperature and calibrating the scanner.


Time needed: 30 minutes




3. Data post-processing in scanning software


After scanning, the data is cleaned in scanning software ScanView. All scanned data are then joined by geometry of the object or using reference marks and then it is necessary to check the quality of the data and their completeness. The last step is to generate the resulting 3D model. The result can be exported to common output mesh formats such as .stl, .ply or or to point cloud files such as .asc, .igs or .txt. Specialized CAD software can then easily upload mesh file and generate surfaces.


Time needed: 10 minutes




4. Measurement and reporting in scanning software


Scanning and measuring software ScanView, which comes with KSCAN Magic, can directly perform CAD file comparison and generate color map with deviations report, which can be saved into pdf file. You can import CAD data that can be compared to scanned data by several methods, including setting up RPS points. It is also possible to create basic ones elements, ie surfaces that are interspersed with a 3D scan.


Time needed: 15 minutes



Extra measurement

The part was provided by the bicycle manufacturer without any technical documentation

and material information and main goal of this project was to prepare 3D data for reverse engineering. However, we selected five parameters for the additional measurement and test of KSCAN Magic, specifically the diameters of the three holes (D1 = 30 mm, D2 = 17 mm, D3 = 8.10 mm) and two pitches between them D1 - D2 (pitch L1 = 120 mm) and D1 - D3 (pitch L2= 71.07 mm). Furthermore, according to the method of mounting the component and its function, we chose to place the holes and pitch tolerances.




The external software GOM Inspect Suite was used for the measurement of the determined parameters. GOM Inspect Suite is free version of complex measuring software and ScanTech ScanView software offers direct data export by single button to GOM Inspect. For those who prefer to do measurements in GOM Inspect there is a fast and easy way how to minimalize the time in the workflow.



As the method for evaluation of parameters of scanned part has been chosen measurement by created elements (cylinder, point, line). First, cylindrical elements were created in the measured holes. These were formed by best-fit function into the scanned data. This was followed by the creation of points that intersect the upper surface of the cylinder and the central axis. By using these points are further formed two lines. The length of these lines expresses the measured distance between holes 1-2 and 1-3.


Table 1 bellow shows 10 repeated measurements of selected parameters:

Table 1: Repeated measurements

Due to the fact that the component had to be equipped by matting chalk spray, it was necessary to correct the achieved results. The value of homogeneous chalk spray injection specified by the manufacturer in a sufficient thickness for satisfactory scan quality is at least 0.015 mm. Therefore, correction of the values ​​of all measured averages

holes is 0.03 mm. Because we had only one sample of the component for measurement, the calculation of the standard uncertainty type A is performed in the standard way, as a sample standard deviation arithmetic mean of the measured values. To calculate the total expanded measurement uncertainty, we choose the expansion coefficient k = 2 with probability of coverage p = 95.45%.


Table 2 bellow shows results of calculated total expanded uncertainty of our 10 measurements on selected parameters:

Table 2: Total expanded uncertainty

As we could see from calculated outputs, none of measured values exceeded certified accuracy of ScanTech KSCAN Magic, which is 0,02 mm.


Summary


Reverse engineering is a term we meet in various industrial areas more and more often also in due to the overall digitization of production. It is a process where the technological parameters of the object are determined. In the world of 3D scanning is the concept of reverse engineering associated with the conversion of scanned 3D data of a real object to

CAD model. It is then used for the production of a new part, analysis or design modifications. Clasical manual modeling is a much slower process where time

complexity also represents higher costs. By using reverse engineering or 3D scanned data, company LeaderFox was able to prepare a CAD model for serial production of new cross-country bike in much lower time and with lower costs.


Time needed (without extra measurement): 56 minutes

Technology used: ScanTech KSCAN Magic, DELL Precision 7540 laptop

Location: Brno, Czech Republic

Lab temperature: 25 °C




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