Study of thickness distribution on a robotic rotational moulding system by experiment and simulation

Abstract

<ns3:p>Background Rotational moulding, despite its competitiveness, has historically been regarded as a low-technology process, mainly due to limited process control and reliance on inexpensive, simple moulds. A recent innovation—the robotic rotational moulding system—addresses these limitations by combining a 6-axis robot arm for direct motion control with an electric-heated mould, offering improved capability to achieve desired wall thickness distribution. Methods This study investigated and compared the thickness distribution of moulded parts using this novel Robomoulding system through both experiments and simulation. A full-factorial experiment examined the effects of three key motion parameters—robot feeding rate, rocking angle, and number of rotations per rocking movement—on final wall thickness. Concurrently, a simplified motion-based Finite Element Analysis model, scripted in MATLAB, simulated polymer powder movement and predicted thickness distribution trends. Results &amp; Conclusion Statistical analysis revealed that robot feeding rate and the interaction between rocking angle and number of rotations are the principal factors influencing wall thickness distribution, while shot weight had a negligible effect. Similar to traditional machines, thickness distribution in robotic rock-and-roll moulding is governed by mould rotation speed and two-axis speed ratio, with higher feeding rates favouring better uniformity. The simplified simulation proved valuable for rapidly predicting distribution patterns for known geometries and prescribed motions.</ns3:p>