1,721,044 research outputs found
Reducing rubber-plastic friction in syringes through microstructured surface design and manufacturing
Full text linkPlastic syringes often rely on silicone oil lubrication to reduce plunger-barrel friction, leading to potential issues like oil droplet release and drug aggregation. This study explored an alternative approach combining two-photon polymerization, laser machining, and microinjection molding to manufacture micro-dimpled structures for low friction. Plastic microdimples with high area density and low aspect ratio significantly reduced the coefficient of friction against rubber, while the dimple profile proved crucial in facilitating replication and demolding. The results of this study provide valuable insights into reducing friction between rubber and plastic, particularly in applications like syringes. (c) 2024 The Author(s). Published by Elsevier Ltd on behalf of CIRP. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/
Using analytical and data-driven methods to develop a soft-sensor for flow rate monitoring in tube extrusion
Full text linkIn manufacturing polyvinyl chloride (PVC) tubes, the required thickness and weight depend on the extruder flow rate. The extruder setup can be very time-consuming and inefficient since it requires adjusting the screw rotational speed by trial & error, as the relation between the flow rate and the rotational speed is not known a priori. Furthermore, it is also affected by the material properties, the melt temperature, and the pressure drop in the die. Direct measuring the flow rate or the tube thickness would require expensive gravimetric dosers or X-ray systems, respectively. Therefore, a soft-sensor was developed to monitor tube thickness and its weight per unit length. Two alternative approaches are proposed to predict the extruder flow rate under wall slip conditions: one is based on a developed analytical model and one on data-driven algorithms. Results show that machine learning regression models can achieve high predictive performance (a relative error of 1.2% using a Support Vector Regressor)
A new approach to the evaluation of ejection friction in micro injection molding
No full textThe ejection phase influences the quality and integrity of micro injection molded parts. The successful design of robust micro mold ejection systems requires studying the tribological interactions at the mold/polymer interface. At the micro-scale, the tooling topography can have a significant impact on the ejection friction. Here we propose a novel approach to the evaluation of ejection friction in micro injection molding. The two main contributors to the ejection force are the normal force due to shrinkage and the static friction coefficient. The former is addressed by developing a procedure for shrinkage characterization at the micro-scale. The latter is studied using experimental measurements of the ejection force in micro injection molding. Comparing the numerical and the experimental results allows identifying the friction coefficient as a function of polymer, process parameters, and mold surface roughness
Influence of the artefact material on the metrological performances of X-ray computed tomography systems
No full textThe advantages offered by X-ray computed tomography (XCT), e.g. the capability to inspect and measure complex geometries and non-accessible or internal features in a non-destructive way, are at the basis of its rapid diffusion in the field of manufacturing metrology. However, a large number of influence factors affect the metrological performances of XCT systems. One of the main variables is the material of the inspected object. In this work, the influence of the material of the artefact used for testing the XCT system is addressed. A reference object was developed, consisting on a hole plate which can be made out of different materials and used to evaluate the performances of a metrological XCT system. The position and the diameter of the holes were specifically designed to match with a ball plate that can be used together with the hole plate in a combined way. Experiments were carried out using the objects separately and combined
Superhydrophobic surfaces for polymers with micro and sub-micro scale structure via Two-Photon Polymerization
No full textOn the correlation between surface quality and tool wear in micro–milling of pure copper
No full textMicro-milling is a material removal – based manufacturing technique that allows fabrication of three-dimensional features in a direct manner, unlike photolithography which relies on expensive masks to print two-dimensional features onto a substrate. However, the inadequate surface quality of micro-milled features, which could be due to improper selection of process parameters and/or tool wear, can hamper the functionality of products. This is specially critical for soft materials such as commercially pure copper. To preserve the surface integrity of such materials, this study proposes a correlation between tool wear and surface quality when micro-milling commercially pure copper. The experiments included full-immersion cutting with 200 μm micro-endmills with an axial depth of cut of 20 μm. The variation of surface roughness and burr formation with wear progression is also studied. The surface quality was investigated on the basis of the surface roughness and burrs geometrical characteristics, as well as in terms of nano-hardness. For doing that, firstly, different micro-milling parameters, namely the feed per tooth and cutting speed, were applied to manufacture a series of slots on a pure copper workpiece. Then, the best and the worst conditions in terms of surface quality were adopted for the tool wear campaign to find the correlation between the tool wear and surface quality
TENSILE AND COMPRESSIVE QUASI-STATIC BEHAVIOUR OF 40% SHORT GLASS FIBRE - PPS REINFORCED COMPOSITES WITH AND WITHOUT GEOMETRICAL VARIATIONS
No full textIn this work, a comprehensive experimental investigation was carried out to characterise the quasi-static tensile
and compressive behaviour of notched and plain specimens made of 40% wt. glass fibre-Polyphenylenesulphide
(40GF-PPS) short fibre reinforced composite.
To this end, plain and notched specimens (with notch radius ranging from 0.25 mm to 10 mm) were manufactured
with two different fibre orientation angles (0◦ and 90◦) and tested under tension and compression,
allowing to observe the effect of the notch root radius and the notch geometry. In addition, a careful analysis was
carried out both at the macroscopic and microscopic level to compare the fracture behaviour of plain and
notched specimens. Finally, a Generalised-Stress-Intensity-Factor-based approach was adopted to correlate the
tensile strength of notched specimens. On the contrary, the compressive strength of the notched samples was
rationalised in terms of the nominal net-stress, thanks to the limited notch sensitivity exhibited by the material
during the compression tests
Investigation of the inflow effect on weld lines morphology and strength in injection molding of short glass fiber reinforced polypropylene
No full textIn parts manufactured by injection molding, the regions affected by the presence of a weld line show worse mechanical properties, especially in the case of fiber-reinforced thermoplastics. This is mainly due to the unfavorable reinforcement orientation in the proximity of the weld line. The position and shape of a weld line, which develops where two different flows converge during the mold filling phase, can be modified by generating a pressure unbalance between flow fronts during the packing phase. This phenomenon is also known as “inflow” in the literature. In this work, the inflow phenomenon was obtained using side features located near the weld line. Its effect on weld line morphology and fibers orientation was investigated. The experimental results show that the inflow can modify the weld line position and shape. Furthermore, it can reorient the fibers in the weld line region, increasing the load at break and stiffness of the weld line by 19% and 15%, respectively. These effects were numerically modeled with a maximum error of 4%
A reference artefact to evaluate the metrological performance in the quantification of raising surface defects on manufactured surfaces
No full textModeling of the ultrasound-assisted ejection in micro injection molding
No full textIn this paper, an ultrasound-aided ejection system was designed and tested for various polymers and mold topographies. The use of ultrasound vibration aims at decreasing the ejection friction by reducing its adhesion component, which is controlled by the real contact area developed in the filling phase of the injection molding process. The experiments indicate that the ultrasound vibration reduces the ejection friction up to a maximum of 16%. The effect depends on the polymer used and it increases for rougher mold surface. Moreover, the dependence of ejection friction on mold surface roughness, melt viscosity and elastic modulus at ejection was modeled using the experimental data
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