Reverse engineering works best with a rapid 3D prototype
For missing or critical parts, 3D printing helps verify form, fit and tolerances prior to production. This reduces the risk of expensive or hard-to-find parts.
- For prototyping, start from 3D printing to order.
- For functional materials take a look industrial filaments and filaments.
- For your own workshop compare 3D printers.
When a small detail has no alternative
When restoring classic cars, there often comes a point where compromises simply aren't possible. Although at first glance some parts seem interchangeable, in reality they work in strict interdependence with the other components. A change in material, shape or geometry can lead to assembly problems, unwanted vibrations and a host of other problems. That was exactly the case in this project.
The part is a special adapter between the exhaust gas outlet from the engine head and the exhaust system of VW Beetle – a car loved for generations with its boxer engine and distinctive sound. The customer was working on restoring the engine to a completely authentic look and was unable to find this part for a long time. No newly manufactured replacement was available, and a used part in good condition is practically impossible to find. Attempts to replace with improvised substitute materials proved unsuccessful because the part is both small – approximately 7 × 7 × 7 cm – and critically important. Usually, the smaller the size of a part, the higher the complexity of the work.
From a worn original to an accurate 3D model
The original part was in poor visual condition - corrosion, scale and traces of long-term use. However, it served as the basis for precise 3D scanning, through which we were able to capture its real geometry. The resulting point cloud was imported into SolidWorks, where a complete solid CAD model was built step by step. During this process, wear defects were eliminated and the geometry was restored to the way it was originally designed.
The comparison between the scanned part and the created CAD model showed an extremely high degree of matching except in the areas of intense wear. This was a key point because any deviation would lead to problems with the installation or operation of the exhaust system. The model created was not just a visual reconstruction, but an accurate engineering basis for the next, significantly more complex phase.
Tooling for sand-casting a grey cast-iron part
For the specific detail, the choice of material was unambiguous – grey cast iron. It meets the requirements for operation at temperatures up to 700°C, the ability to absorb vibrations, thermal cycling and long-term reliability. In addition, the material is characterized by good castability in thin sections and a relatively low cost, which makes it suitable for mass production.
The main work in this case was the design of the tooling for casting in sand moulds. A pattern for the part and a 3D-printed core box for forming the sand core were designed. Particular attention was paid to the design of the core box, dividing it into two parts (halves) along the parting line, which in this case is complex and broken. This enabled the sand core to be removed smoothly after moulding. The necessary draft angles and allowances were also added to the model to suit its parting line. In addition, in the construction of the equipment, the necessary allowances for machining, as well as the shrinkage of the metal after casting, were incorporated.
By omitting any of the above steps, the part could not be manufactured to meet the originally set dimensions and geometric requirements. The end result is a fully functional part meeting all technical requirements, as well as tooling enabling repeatable and reliable production. Of course, the good end result is a consequence of the joint work between design, casting and subsequent machining. This project clearly shows that through a combination of 3D scanning, CAD engineering and modern equipment manufacturing methods, even the rarest and most critical components can be restored in a short time and at a low cost. For the customer, this means not just another part, but an opportunity for the VW Beetle to run as it was designed decades ago – authentically, reliably and without compromise. The part was subsequently produced in a short run and supplied to other enthusiasts of this iconic car.
Article source and partner – dsc-labsolutions.com
