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Injection-molded rubber parts are widely used in automotive, aeronautical, and industrial engineering applications Therefore, such rubber parts are often critical to the safe operation of the entire system, and part failure can result in significant human or environmental damage. To avoid shipping any parts of subpar quality, manufacturers need to continuously monitor the quality of their product, xln this work, we apply a principal component analysis (PCA) based process monitoring method. This method is able to detect process fluctuations (faults) in real-time solely from sensor data features, only requiring pretraining on data from about 10 in-control cycles. Specific faults were set to critically affect the dynamic performance of the manufactured NBR rubber parts. Fisher discriminant analysis (FDA) was employed to automatically cluster individual molding cycles into those of being in control, those of defectives caused by unfavorable raw material storage and those of out-of-tolerance induced by an overheated mold, again solely from sensor data. Both PCA fault detection and FDA fault identification decisions were validated by oscillatory rheology and dynamic compression testing of the manufactured parts. This combined method approach is scalable, transferable, and can be implemented on standard industrial injection molding equipment. KEYWORDS injection molding, process control, process monitoring, processing, rubber, 1 | INTRODUCTION Injection-molded rubber parts are widely used in and industrial engineering applications whenever excellent damping, sealing, and resistance to harsh environments are needed. Therefore, such rubber parts are [...]

Fiber-reinforced polymers allow for the implementation of plastic materials in structural components. However, increasing incorporation of fibers up to 50 wt% causes accelerated component wear in injection molding machines. In particular, the barrel and screw in the compression zone suffer from increased wear. The abrasive fibers of the compacted polymer pellets in the solid bed protrude from the surfaces of the resin having an abrasive, brush-like behavior. A modified pin-on-disk testing system with specially designed polymer pins was used to emulate the described tribological system in laboratory scale. Through varying contact pressure, temperature, and surface modifications of the counterparts (blank or coated powder-metallurgical steel), abrasive wear as observed in industrial-sized extruder screws could be successfully simulated on a laboratory-scale testing system. Detailed investigations of the pins and disks highlighted that the glass fibers plow and cut the surface leading to abrasion as observed in the real field application. Temperature has been proven to be the most decisive driving force. Surface modifications such as protective physical vapor-deposited CrN coatings are effective against abrasive wear, clearly outperforming untreated steels. The presented pin-on-disk-test setup will improve screening of materials for extruders, thus enhancing the durability of injection molding machines., INTRODUCTION The invention of composite polymers has led to an increase of potential applications for plastic materials due to improved mechanical properties, including their use in high-performance structural components. High [...]

Highly filled rubber compounds exhibit a unique rheological behavior, which is affected by its filler-filler and filler-matrix interactions leading to pronounced nonlinear viscoelasticity. The necessity to consider these characteristics in rheological testing and modeling, adds further complexity providing universally valid numerical descriptions. In the present study, the pressure driven contraction and capillary flow of a carbon black filled hydrogenated acrylonitrile-butadiene rubber compound is studied both experimentally and numerically. Rheological testing indicates no pronounced slippage at the wall but a shear sensitive plug flow at the centerline. The viscoelastic Kaye-Bernstein-Kearsley-Zapas/Wagner, the viscoplastic Herschel-Bulkley and the viscous power-law models are used in computational fluid dynamic simulations aiming to predict measured pressure drops in an orifice and various capillary dies. Viscoelastic modeling is found of particular importance describing contraction flow dominated areas, whereas viscous models are able to predict pressure drops of capillary flows well., INTRODUCTION Industrially produced rubber compounds consist of one or more synthetic or natural-based polymers (gum), reinforcing fillers (silica, carbon black), and several additives such as plasticizers, processing aids, and a [...]

In this study, polymer nanocomposites (PNCs) based on polypropylene (PP), organoclay (used as nanoclay), and compatibilizer were prepared by a masterbatch (MB or two-step) as well as by a one-step process. These compounds were then injection molded into tensile test specimens and rectangular plates using conically and hyperbolically shaped nozzles. The use of these nozzles in the injection unit was to enhance intercalation and exfoliation in the PNCs by means of elongational flow. The pressure loss and temperature rise in the compound induced by this flow were characterized in temperature and pressure measurements. An additional calculation using a new analytic model showed good correlation with the measured values for the conically shaped nozzles whereas the pressure drops in the hyperbolically shaped nozzles were underpredicted. Mechanical as well as rheological characterizations were performed on the produced test specimens. The compounds from the MB process showed good intercalation and exfoliation and improved mechanical properties without any special elongational flow treatment. Similar properties were achieved with the one-step process and elongational treatment using a short hyperbolically or conically shaped nozzle. These results indicated that it was possible to eliminate one complete compounding step and achieve the same mechanical properties in polypropylene nanocomposites when elongational elements were used. POLYM. ENG. SCI., 58:3-12, 2018., INTRODUCTION During the last 50 years' polymers have become one of the most important material groups in modern industry. Further developments in materials and major innovations are achieved by modifying [...]

The standard application‐oriented test for abrasive wear of polymers on plastic mold steels is the platelet wear tester method in which two steel specimens form a thin wear slit. The glass fiber‐reinforced polymer melt is injected through the wear slit, and the surface of both specimens is abraded. In the injection molding process, similar conditions often occur in thin‐walled parts or film gates. Drastic loss of the hardness of a powder metallurgical steel (PM steel) is discovered after approx. 200 injection cycles while performing platelet wear tests. For experimentally analyzing the reason for the loss of steel hardness during injection molding, a new platelet wear testing apparatus is developed, which can be used to measure the increase in temperature inside the steel specimen while testing. The first results show and support the hypothesis that a temperature increase above the annealing temperature occurs inside the steel due to viscous dissipation at the steel surface. In cooperation with the company voestalpine BÖHLER Edelstahl & Co KG, tests on the PM steel in a dilatometer are performed to simulate the cycle‐by‐cycle heat pulses occurring in the injection molding process. With the results of those tests, it is possible to state a hypothesis for the reason of this hardness loss. [ABSTRACT FROM AUTHOR]

This study aimed at optimizing the injection molding process of an automotive oil filter housing made from PA6.6. Mass accumulations in its design intensely increased the cooling time. In a first successful approach, a copper alloy mold insert (λ = 106 Wm−1 K−1) that contains two externally cooled heat‐conducting copper pins (λ = 310 Wm−1 K−1) was installed. We hypothesized that a biomimetic cooling channel structure in a steel mold insert would even perform superior. Using simulation software Sigmasoft® v5.0, the mold insert materials (steel Bohler X20Cr13, Ampcoloy® 83), the plastics grade PA66‐GF35 (λ = 0.27 Wm−1 K−1 or λ = 0.40 Wm−1 K−1), and three cooling designs were evaluated for their impact on cooling the hot spots in the part: the copper pin‐system, a conformal cooling channel, and blood‐vessel like channels. In the latter, the major artery branches into two sub‐arteries, which further divide into two capillary tubes each. The capillaries merge into two sub‐veins and those fuse in the major vein again. As expected, the plastics heat conductivity dominates the cooling. The biomimetic (blood‐vessel) channels, as hypothesized, cooled the major hot spot more efficient than the conformal channel and the copper pin system do. In detail, compared to the heat‐conductive insert, the cycle time may be reduced by 10 s, in spite of the lower heat conductivity λ (23.5 Wm−1 K−1) of the steel insert. Using the biomimetic (blood‐vessel) structure in a heat‐conductive mold insert would reduce the cycle time by a further second. However, raising the heat conductivity of the plastics would save another 15s. Experimental tests proved the cooling efficiency. Nevertheless, cooling channels only perform well, if they are close enough to the mass accumulation. In conclusion, transferring biologic cooling structures to injection molding seems to be promising. Ongoing advances in Additive Manufacturing will help to efficiently implement these structures into mold inserts for injection molding. POLYM. ENG. SCI., 59:E180–E188, 2019. © 2018 The Authors. Polymer Engineering & Science published by Wiley Periodicals, Inc. on behalf of Society of Plastics Engineers. [ABSTRACT FROM AUTHOR]

In injection molding wear of components is pronounced in positions with high flow rates of melt. The platelet‐wear‐test is an established method for comparative assessment of wear resistance of tool materials in such regimes. Within this study three metal matrix composites: two hard metals and one powder metallurgical steel were investigated. Results show non‐linear wear rates with increasing amount of plastic melt processed. The reasons were found in the viscous dissipation, which is based on high volumetric flow rates and the small wear gap, leading to a temperature rise, which are detrimental especially for the PM‐steel. Analysis of the processed glass fiber‐filled polymer showed dramatic decrease of fiber length due to the processing through the wear gap. This entails a high amount of free fiber ends, resulting in higher load for the surfaces through micro chipping. POLYM. ENG. SCI., 59:E302–E311, 2019. © 2018 The Authors. Polymer Engineering & Science published by Wiley Periodicals, Inc. on behalf of Society of Plastics Engineers. [ABSTRACT FROM AUTHOR]