Use the computed tomography for the automatic tool correction of the mould injection process

摘要

Currently many iterations and an experienced operate are necessary to achieve a high product quality for injection moilding parts. Therefore a partly automatic mould correction is needed which is intimately connected with metrology in order to reduce correction loops dramatically. Several different methods are used to attain high product quality in injection moilding. The basic method is the design of the moild under consideration of the production parameters, for example the shrinkage of the plastic can be taken into account. An alternative method uses modification of the production parameters based on simulation processes (for example a mould flow analysis). Despite such complex simulations the required product quality is not always reached. Further improvements can be attained by iterative modification of the moulds. The mould correction consists of three major sub-processes: the design of the mould, the injection moulding process and the quality control of the workpieces and / or moulds. All three areas are tightly interconnected. Both the moulds and the production parameters directly influence the quality of the workpiece. The workpiece measurement data defines the process quality which then influence the correction process. The process begins with the design and production of a moulding injection tool based on the nominal geometry of the workpiece. The first produced workpiece is measured using computed tomography. The difference between the measured geometry and the nominal geometry is calculated using the measurement results. These are mirrored around the nominal geometry. A new corrected CAD surface is generated using the mirrored measurement points. Complicated manual methods to correct surfaces are not necessary. Errors emanating from the operator are almost eliminated. This guarantees the high quality of the CAD model and results in a correction process with only a few iterations. The methods allow the different processes to be carried out at geographically different sites. Data Exchange of CAD models and point clouds can be done via Intranet or Internet. This is Industry 4.0 in practice.