Ultrasound-based Melt Front Velocity Measurement in Injection Moulding Moulds
Sprache des Vortragstitels:
Englisch
Original Tagungtitel:
PPS2024
Sprache des Tagungstitel:
Englisch
Original Kurzfassung:
Injection moulding is a predominant method used in the production of plastic parts. Among others, the melt front velocity (MFV) plays a pivotal role in determining the final properties of the moulded part. Accurate control and measurement of this velocity are essential for several reasons:
An optimal velocity ensures that the polymer fills the mould uniformly, reducing the likelihood of defects such as short shots, free-jet formation and air entrapment or other defects that can compromise the mechanical properties, aesthetic appearance, and functionality of the final product. Moreover, variations in velocity can lead to localized cooling or overheating, resulting in differential shrinkage and deformation of the part.
In addition, real-time measurement of MFV enables process optimization and control. This capability enhances the precision and repeatability of the moulding process, leading to improved cycle times and reduced material waste.
A state of the art method to measure the MFV in injection moulding moulds is the utilization of pressure and temperature sensors placed at various locations within the mould. Here changes in pressure or temperature as the melt front passes by are detected. By analysing the time at which these changes occur at different points, the velocity of the melt front can be calculated. However, this technique is limited since at least two sensors are needed to estimate the flow front velocity. Moreover, due to the direct contact of the sensor with melt in the cavity sensor markers are visible on the final part.
In contrast, we use ultrasonic sensors to detect both the melt front position and velocity in the mould. Therefore, sound waves are emitted into the mould and the signal reflected by the cavity wall is measured. Changes in the reflection pattern as the melt front progresses can be used to calculate its velocity. Thus; the MFV can be measured with only one sensor and without direct contact to the melt.
Forschungs-