Reverse Engineering - Spritzgusswerkzeug mit kleinen Hakenkavitäten

injection mould


Spinning components for ring spinning machines

Very high speeds are achieved when processing yarns in spinning machines. The guidance of these yarns through the ring and runner during winding onto the spindles is considered a critical point in the manufacturing process. Accordingly, rings and runners are of extraordinary importance as individual components in the composite of all components of a spinning machine. To take this into account, the manufacturer is constantly pushing the development of these components. Investigations showed that the operational reliability and availability of the spinning machines could be further increased by optimising the rotor area. The intelligent use of existing resources finally made it possible to integrate existing materials into the design of the advanced rotor tools. The existing tools only had to be changed in a few places to meet the new requirements. However, since these tools represented the latest state of a practically oriented development, it was first necessary to generate the corresponding CAD data.


In the specific case, the customer commissioned the measurement of an injection mould and the parametric design of the associated CAD model. The CAD model should become fully parametric and further processable for the customer to enable the production of the advanced tool.

Injection moulds usually consist of two halves, which must fit together exactly. In order to simplify production and injection, the tools are designed so that the contact surfaces between the halves represent the centre plane of the subsequent part.

For the spraying process, both halves are pressed against each other with great force by two holders. The cavities between the halves form the shape of the later part. Hot plastic is now introduced into these cavities under high pressure. After the plastic has solidified, the halves are separated and the part can be removed. In the present case, there were twelve cavities per mould, which were arranged in a circle around the plastic feed.

Since the previous tool served as the basis for further development, reverse engineering as a method of data generation was established for the required precision. In individual customer meetings sigma3D explained its performance performance and the achievable measurement results.

The generated 3D model based on the existing tool is a fully-fledged design result. The component geometry can then be modified by the parametric structure of the CAD data. In addition, the 3D model offers the preference of optimally matching the design of the new injection mold to the required functionality.

Method of measurement:

ScanKamera - strip light projection

The tool is measured with a scan camera. The measuring system consists of a measuring camera, uncoded measuring marks and evaluation software. The uncoded measurement marks are the basis for the orientation of the individual measurement images of the scan camera. The strip light projection system is an optical measuring machine based on the triangulation principle. Two cameras observe projected stripe patterns. With the help of the two cameras, the object to be measured is recorded from different directions so that all relevant object areas are covered. 3D coordinates are calculated with high precision for each camera pixel. An evaluation software generates a polygon mesh of the object surface. The polygonal model is the basis for the following reverse engineering process.


For the parametric construction of the CAD model, the polygonal model is imported into the construction software. An essential design aid is the alignment of the tool over the contact surface and the main bore. The plane and axis thus defined describe the coordinate system and simplify the design process.

The construction plane is selected according to the one with which the polygonal model is intersected. The section contours are displayed on the selected construction plane. This reflects the shape of the cylindrical outer contour. In this construction plane, the section contour is constructed from individual construction elements (straight line, circle, spline). The construction elements are then assigned the corresponding dependencies (horizontal, vertical, fixed, concentric, tangential, etc.). For the full definition, the sketch is dimensioned last. Parallel to the design process, a deviation visualization indicates compliance with the tolerance specifications for the measurement data. The result of a sketch is a closed profile for a surface or volume function.

For the design of the cavities, which form the actual production parts, an averaged cavity is calculated from the 12 cavities. A surface function is used to place splines on the surface of this cavity. These splines form a curve network, which is transformed into a coherent area network. This surface bond represents one half of the surface of the production part. The second half is obtained by reflecting the surface bond on the middle plane. Both surface composites are connected and transferred into a solid body which reflects one of the twelve production parts.

Since the production parts and the channels are each available in twelvefold design in the injection moulding tool, the volume body created for this purpose is duplicated twelvefold via a circle pattern function. These volume bodies are removed from the main body by a Boolean function so that the tool with the functional geometries remains.


The result is a parametric 3D solid model and the basis for creating a 2D manufacturing drawing.


"Our requirements for optimizing the injection mold require a precise 3D model based on scan data. With the solution offered by sigma3D GmbH this has been optimally achieved".

- Reiners + Fürst GmbH u. Co. KG, Jürgen Smekal, Project Manager