What happens when a company suffers a production breakdown and scheduled maintenance measures can no longer be carried out on time? This is the case, for example, if the required spare parts are no longer available or the manufacturer has completely disappeared from the market. Particularly where special or customized systems are used, companies often face major challenges when individual parts or even entire segments start to wear out.

If spare parts are no longer available in the event of a defect, design engineers require drawings or 3D models of the segments to be reconstructed. Reverse engineering is recommended to make these available. In this process, users create precise CAD data sets based on the existing object, saving time and money, which are then used to manufacture the prototypes. For this purpose, a 3D scanner is used to precisely reproduce the component. Even severely damaged or incomplete objects can be reconstructed in this way, as the process digitally prepares irregular geometries. Reverse engineering is always carried out in the same way, regardless of the machine type, and is used in particular for objects with free-form surfaces.

3D scanner in use

The process used provides precise data records in several stages, which serve as the basis for production. All design-relevant features of an existing original component are extracted using a hand-held 3D scanner. Thanks to its sensitive sensors, it offers flexible application options and captures objects and their surroundings from different angles.

The laser sensor of the hand-held 3D scanner records 88,000 points per second.

© Norrenbrock

Aimed at the component to be scanned, material properties as well as structures can be recorded at the touch of a button. With a repeat accuracy of less than 0.02 millimetres, the laser sensor records up to 88,000 points per second. In order to record the geometry of the component in question as precisely as possible, this process can be carried out both optically and tactilely. The process is not limited to individual parts, but is also used to reproduce larger segments. The scanning process digitally prepares irregular geometries. Subsequent reverse engineering generates precise CAD data records, which are later transferred to a coordinate system and used to manufacture the prototype.

By using the scanner together with a tablet or laptop during the entire process, it offers real-time visualization of the so-called point cloud data. This allows the captured areas to be checked in parallel with the scan to ensure that important information is not lost during data capture. The captured 3D data is saved directly to a PC for further processing. Here they are available in STL format, for example, for further processing in various CAD programs. It is also possible to combine an already captured point cloud with another one. Clouds are available for the effective and internal exchange of processed scan data.

Making data tangible

Creating the necessary CAD data sets lays the foundation for developing a new, identical component from the original model. At the same time, this step marks the start of the actual reverse process. It forms the interface between the point cloud generated by the scanner and the creation of a CAD model with specific object and surface properties. In order to serve as an optimal production basis, the data is displayed as a simplified 3D representation in the form of interactive CAD models.

The generation of these geometric features is divided into two categories. In parameterized traceability, simple geometry elements are placed on the point cloud and combined to form a whole. This method is mainly used for spheres, circles and second, third and fourth degree surfaces. In contrast, non-parametrized traceability is used for objects that have no explicit geometric properties. To display these in CAD, the entire object is covered with a type of virtual mesh stocking. The meshes of the stocking form the surfaces of the CAD model. These are subdivided by a large number of smaller segments, so-called grids, and no longer have any actual geometry elements. In this way, objects with complex and irregular structures can be represented in detail in the CAD system with the help of reverse engineering.

In addition to geometric properties, this virtual model also simulates physical aspects such as the density or thermal expansion coefficient of the component. It also takes into account the surface, structure and optical material properties of the original. The body described in this way can be virtually weighed and deformed. This means that even complex questions about production can be answered directly on the screen with just a few clicks using the virtual image. This procedure saves important time resources and also helps to avoid production errors. The prototype of the reconstructed component is then manufactured on the basis of the CAD model created in this way.

No time to lose

The process also allows companies to cover all strategic considerations regarding the process of returning to a reproducible initial model. Reverse engineering also takes into account the points of interaction with corresponding elements so that the component and machine function without restriction after reconstruction. Companies save time and money by manufacturing the required component and maintaining the machine. Here is an example of the process for the reconstruction of a gearwheel: At around 45 minutes, the scanning process takes the shortest amount of time in the overall process. The design takes just under 90 minutes and includes the creation of the CAD data sets and their detailed representation.

The captured 3D data is saved directly to a PC for further processing and is then available in STL format for further processing in various CAD programs.

© Norrenbrock

Reverse engineering is completed by manufacturing the component, which takes another two hours or so for the gear wheel.

Depending on the application properties, it is necessary to react and adapt the manufacturing process to the corresponding conditions. In the case of original parts that were produced as castings in the past, for example, and are now sent for reverse engineering, modern processes are used to achieve optimum results. This means that even small quantities can be produced without any problems. The use of alternative processes such as machining or the combination of several production methods reduces the amount of work involved. In addition, a newly adapted production method saves costs. With this process, the user ultimately generates a milled part, as shape and position tolerances can be produced much more accurately.

The turnover of many companies stands and falls with the functioning of the machines. Consequently, production downtimes mean that orders cannot be completed. Operators therefore aim to keep their systems in good working order. Processes such as reverse engineering help to repair machines in the event of defects in a cost- and time-efficient manner. The method is particularly suitable for reconstructing components that move or cause friction. These have the highest risk of damage. If the process comes to a standstill, avoidable costs are incurred. Thanks to the fast processing of the procedure, downtimes are short and production can be resumed quickly. This is how maintenance managers react to unforeseen breakdowns in particular.

Author: Robert Norrenbrock is Managing Director of Norrenbrock Technik.