Posted by Kashyap Vyas on August 31st, 2016
Classic or heritage cars are always fascinating; the history it has seen & the places it has been and the people it has seen, moves most of us and imbibe a desire to have at least one of this vintage human invention in our garage. But, maintaining the glory of these unique classics isn’t easy. People who own classic vehicles have their own set of problems and challenges in maintaining them, both in terms of bodywork as well as mechanical components. The rarity of these heritage vehicles makes it difficult to find replacement parts that keep the vehicle functional. For some older models, the original manufacturer may not even exist.
Thankfully, tools like CAD, reverse engineering and CAE (Computer Aided Engineering) combined with traditional engineering principles helps in resolving these challenges.
Reverse engineering is helpful in reproducing obsolete parts for classic vehicles. The process usually involves taking an existing part, measuring it, 3D CAD Model in tools like SolidWorks or Inventor, and later developing manufacturing drawings for reproduction. There are numerous technologies used for the reverse engineering process depending mainly on factors like, the required level of accuracy and tolerances, part complexity, manufacturing process and materials involved. Reverse engineering also largely depends on the accuracy in the physical appearance required to ensure that the new part replicates all the features, imperfections and fine details apart from budget constraints.
Manual measurements can be performed on parts where accuracy and tolerances are not crucial. A 3D CAD model can be easily prepared through the measurements taken. However, for a complex part with critical internal features which cannot be dismantled, measuring manually is not possible. It is the reason why other measuring techniques are employed to recover design information from complex parts with greater level of accuracy. Let’s look at them in detail:
3D scanning is one of the widely used and the most accurate method to capture design data for reverse engineering parts. Scanning is usually done through light or laser sources, which impinges on part surface and capture an image in the form of ‘point clouds’. This point cloud data forms a mesh made up of millions of points, which can then be transferred to any CAD software to convert it into a solid model. Once the model is created, manufacturing drawings can be extracted easily. The scan data however can also be utilized to keep a check on accuracy by comparing the new CAD model developed with the original scan.
The accuracy of scanning however is largely dependent on the scanner. Some scanners have the ability to replicate the part to tolerance values of +/- 2 microns, provided the scanning is performed in a controlled environment.
The problem with scanning however is it can capture only the surfaces that are visible to the scanner. This problem can be solved by combining other processes, such as reconstructing missing features directly on to the CAD model from data collected through manual measurement.
CT scanning is the preferred method to scan parts with internal details that are not accessible through dismantling. The process of CT scanning is similar to the one carried out in hospitals and extremely useful in capturing internal as well as external features of the part, in order to develop detailed 3D CAD model and 2D manufacturing drawings. CT scanning has its limitations too; the accuracy of scanning is largely dependent on size of the part and its thickness. Scanning a too large or thick part might not yield accurate results. Also, the cost of CT scanning is more, which nullifies its use for low value parts.
The ideal way is then to combine these two technologies to ensure that the accuracy is maintained and the cost of reverse engineering remains within the budget.
Mechanical parts have the tendency to wear with time, and with classic vehicles this is even worse. Now, you may create an exact replica of the replacement part through reverse engineering, but when assembling, you might not achieve the perfect fit. This is due the fact that other interconnected parts have worn out and have caused an increase or decrease in clearances and tolerances, preventing the new part from fitting perfectly. Reverse engineering however creates 3D CAD model, and it is editable, allowing you to adjust the dimensions to ensure that the new part fits with the interconnecting parts perfectly. Gear is an excellent example for this. Being mechanical in nature, gears often wear out with time. Modeling a new worn part, so that it fits with other gearing arrangements perfectly can be achieved easily by simply modifying the dimensions in the gear CAD model.
Applying reverse engineering to restore part information for classic vehicles requires understanding the importance of tolerances. While today’s engineers have the tools and machines to work with tighter tolerances, the issue is that the original parts developed years back would have not developed considering such accurate tolerances. Thus, tolerances are no longer a challenge, but the concern is how accurate the tolerances have to be? In cases of classic vehicles, usually the demand is to reproduce the part accurately to fully represent the original part with all the defects.
Having digital design information for parts brings along several benefits. While it not only helps in performing design modifications, the digital model can be used to perform virtual tests to optimize the design and improve the performance of the part. Performance optimization is critical for classic parts to ensure that the part is durable and sustainable for longer operating cycles as well as it is reliable enough to perform well even during the extreme conditions.
The use of virtual simulation tools like Computational Fluid Dynamics (CFD) or Finite Element Analysis (FEA) can be utilized to perform virtual tests to identify the design intent, part behavior and performance characteristics. Based on the results, the design can be modified to optimize the material usage or improve the performance, and the same can be validated through physical tests.
Digital 3D design data for rare, obsolete parts is a valuable asset and it becomes even more important when there is no technical or manufacturing information available. Digital design data can be easily archived and used whenever required, preserving all the details of a classic vehicle right from body panels to critical engine components.
Here are few important benefits of digitizing your classic vehicle design data:
Rapid prototyping is increasingly used to connect the design and manufacturing of products. If used correctly, it can significantly reduce the design and manufacturing time. In case of a classic vehicle restoration, if there is a part that is expensive to manufacture and you are unsure about its accuracy and tolerances, rapid prototyping can be of help. A plastic part can be first developed quickly through rapid prototyping to match the design and dimensional requirements, and once the design is finalized, actual manufacturing can be initiated. Thus, reviewing the part design becomes easier and is less costly.
Creating a 3D CAD model has numerous benefits over utilizing traditional 2D drawings:
Modern design and manufacturing tools as such prove significantly helpful in preserving the unique engineering masterpieces developed years ago. These technologies have not only helped in saving time and cost, but have opened number of opportunities to improve the design further, so that classic vehicles can be maintained in their original condition for generations to come.
So car clubs and car studios specializing in well finished and restoration of most rare and sought after classics and luxury automobiles, can visit us to know more about on how we can help them with their restoration projects.
About Author: Kashyap Vyas is an Engineer at Hi-Tech and holds a Master’s degree in Thermal Engineering with several research papers to his credit. He covers CAD and CAE topics for the engineering industry. His contributions are primarily focused on encouraging manufacturers and suppliers to adopt virtual product development tools to build efficient products with reduced time-to-market.
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