scholarly journals Reduction of Ejection Forces in Injection Molding by Applying Mechanically Post-Treated CrN and CrAlN PVD Films

2019 ◽  
Vol 3 (4) ◽  
pp. 88
Author(s):  
Tillmann ◽  
Stangier ◽  
Lopes Dias ◽  
Gelinski ◽  
Stanko ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Injection Molding ◽  
Post Treatment ◽  
Injection Mold ◽  
Relevant Aspect ◽  
Production Rates ◽  
Surface Conditions ◽  
Roughness Profile ◽  
Coated Surfaces

In injection molding, the reduction of ejection forces is a process relevant aspect to improve the production rates. For this purpose, CrN and CrAlN films were sputtered on cylindrical and quadratic AISI H11 cores of an injection mold in order to investigate their influence on the resulting ejection forces to demold polypropylene test components. Within this context, the ejection forces of the PVD coated cores were compared to those of uncoated cores made of AISI H11. For both the cylindrical and quadratic cores, the as-deposited CrN and CrAlN films exhibit higher ejection forces than the uncoated cores due to the increase of the roughness profile after sputtering. It is known that the ejection forces are directly related to the surface roughness. In order to ensure comparable surface conditions to the uncoated surfaces, and to demonstrate the potential of PVD coated mold surfaces when reducing the ejection forces, the coated surfaces were mechanically post-treated to obtain a similar roughness profile as the uncoated cores. The combination of a PVD deposition and post-treatment ensures a significant reduction of the ejection forces by 22.6% and 23.7% for both core geometries.

A new method for quantifying the blocking of coated paperboard

TAPPI Journal ◽  
2010 ◽  
Vol 9 (5) ◽  
pp. 29-35 ◽  
Author(s):  
PAULINE SKILLINGTON ◽  
YOLANDE R. SCHOEMAN ◽  
VALESKA CLOETE ◽  
PATRICE C. HARTMANN
Keyword(s):  
Surface Roughness ◽  
Fatty Acid ◽  
Surface Energy ◽  
Film Thickness ◽  
External Factors ◽  
Additive Concentration ◽  
Pressure Surface ◽  
Fatty Acid Amides ◽  
Coated Surfaces ◽  
Definite Period

Blocking is undesired adhesion between two surfaces when subjected to pressure and temperature constraints. Blocking between two coated paperboards in contact with each other may be caused by inter-diffusion, adsorption, or electrostatic forces occurring between the respective coating surfaces. These interactions are influenced by factors such as the temperature, pressure, surface roughness, and surface energy. Blocking potentially can be reduced by adjusting these factors, or by using antiblocking additives such as talc, amorphous silica, fatty acid amides, or polymeric waxes. We developed a method of quantifying blocking using a rheometer. Coated surfaces were put in contact with each other with controlled pressure and temperature for a definite period. We then measured the work necessary to pull the two surfaces apart. This was a reproducible way to accurately quantify blocking. The method was applied to determine the effect external factors have on the blocking tendency of coated paperboards, i.e., antiblocking additive concentration, film thickness, temperature, and humidity.

scholarly journals Post-Processing Time Dependence of Shrinkage and Mechanical Properties of Injection-Molded Polypropylene

Materials ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 22
Author(s):  
Artur Kościuszko ◽  
Dawid Marciniak ◽  
Dariusz Sykutera
Keyword(s):  
Mechanical Properties ◽  
Impact Strength ◽  
Injection Molding ◽  
Accelerated Aging ◽  
Mold Temperature ◽  
Degree Of Crystallinity ◽  
Injection Mold ◽  
Secondary Crystallization ◽  
Scanning Calorimetry ◽  
Injection Molded

Dimensions of the injection-molded semi-crystalline materials (polymeric products) decrease with the time that elapses from their formation. The post-molding shrinkage is an effect of secondary crystallization; the increase in the degree of polymer crystallinity leads to an increase in stiffness and decrease in impact strength of the polymer material. The aim of this study was to assess the changes in the values of post-molding shrinkage of polypropylene produced by injection molding at two different temperatures of the mold (20 °C and 80 °C), and conditioned for 504 h at 23 °C. Subsequently, the samples were annealed for 24 h at 140 °C in order to conduct their accelerated aging. The results of shrinkage tests were related to the changes of mechanical properties that accompany the secondary crystallization. The degree of crystallinity of the conditioned samples was determined by means of density measurements and differential scanning calorimetry. It was found that the changes in the length of the moldings that took place after removal from the injection mold were accompanied by an increase of 20% in the modulus of elasticity, regardless of the conditions under which the samples were made. The differences in the shrinkage and mechanical properties of the samples resulting from mold temperature, as determined by tensile test, were removed by annealing. However, the samples made at two different injection mold temperature values still significantly differed in impact strength, the values of which were clearly higher for the annealed samples compared to the results determined for the samples immediately after the injection molding.

Effect of Surface Conditions on the Adhesion of Crystallization Fouling

2010 ◽  
Author(s):  
Yong Zou ◽  
Yida Liu ◽  
Gongming Xin ◽  
Wen Liu ◽  
Lin Cheng
Keyword(s):  
Heat Transfer ◽  
Surface Roughness ◽  
Oxide Layer ◽  
Crystalline Structure ◽  
Lattice Parameter ◽  
Hexagonal Structure ◽  
Experimental Results ◽  
Obvious Effect ◽  
Surface Conditions ◽  
Effect Of Surface

In this study, effects of surface conditions in terms of surface roughness and oxide layer, on adhesion of crystallization fouling on heat transfer surfaces were investigated. The experimental results showed that the surface roughness has no obvious effect on the adhesion of crystallization fouling. The polished sample did not present better anti-fouling properties compared to other rough samples. While the formation of Fe2O3 layer on the surface is proved to be able to accelerate the adhesion of calcite fouling with hexagonal structure, because there are similar crystalline structure and lattice parameter between the Fe2O3 and calcite fouling. Therefore, in order to improve the anti-fouling property of heat transfer surfaces, inhibiting the formation of oxide layer is more important than efforts to improve surface roughness.

Optimal Layout and Sizing of Ejector Pins for Injection Mold Design

1998 ◽  
Author(s):  
Seongjoon Kwak ◽  
Kunwoo Lee
Keyword(s):  
Wavelet Transform ◽  
Injection Molding ◽  
Mold Design ◽  
Injection Mold ◽  
Optimal Layout ◽  
Rule Based ◽  
Rule Based System ◽  
Molded Part ◽  
Injection Mold Design ◽  
Local Stresses

Abstract Injection molding is the most prevalent technology used for processing thermoplastic polymers. At the end of the injection molding cycle, the plastic molded part should be ejected when the injection mold opens. Complex moldings with bosses, ribs, or other features are generally ejected by ejector pins because they are economical and easy to be installed. However, the ejector pins can cause high local stresses and strains in the molding at the stage of ejection leading to the part deformation and damage. This paper proposes a method to determine the layout and size of the ejector pins required to eject thermoplastic moldings with minimizing the part deformation and damage. The proposed method calculates the distribution of the necessary ejecting forces to overcome the friction between the part and its mold. Then, it transforms the ejecting forces into a certain number of representative forces by the wavelet transform. Finally, we can get the location and size of the ejector pins corresponding to the discrete ejecting forces with the help of a rule-based system. The proposed method helps an injection mold designer to systematically obtain an optimum ejector design.

scholarly journals Printability and Properties of Conductive Inks on Primer-Coated Surfaces

2019 ◽  
Vol 2019 ◽  
pp. 1-8
Author(s):  
Hector R. Mendez-Rossal ◽  
Gernot M. Wallner
Keyword(s):  
Electrical Conductivity ◽  
Surface Roughness ◽  
Electrical Resistivity ◽  
Screen Printing ◽  
Good Adhesion ◽  
Laser Confocal Microscopy ◽  
Conductive Inks ◽  
Coated Metal ◽  
Coated Surfaces ◽  
Resistivity Testing

Conductive inks’ performance is affected by the printing conditions and the substrate’s properties. In this study, one graphite-, one polymer-, and two silver-based conductive inks were printed on four primer-coated metal substrates by screen printing. The compatibility and wettability between the inks and the primers were evaluated by infrared spectroscopy and surface energy measurements. The printed structures were characterized by laser confocal microscopy, peel-off tape testing, and four-point probe electrical resistivity testing. In general, silver inks exhibited the best performance in terms of printability and electrical conductivity. The graphite ink presented the worst printing, adhesion, and functional properties. The polymer-based ink revealed poor wettability but good adhesion and functionality. The surface roughness, energy, and polarity of the primer coating had no significant influence on the electrical conductivity of the printed inks.

In Vitro Evaluation of Surface Properties and Wear Resistance of Conventional and Bulk-fill Resin-based Composites After Brushing With a Dentifrice

2019 ◽  
Vol 44 (6) ◽  
pp. 637-647 ◽  
Author(s):  
CAK Shimokawa ◽  
M Giannini ◽  
CB André ◽  
BO Sahadi ◽  
JJ Faraoni ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Wear Resistance ◽  
Three Dimensional ◽  
Significant Negative Correlation ◽  
Weak Correlation ◽  
Surface Loss ◽  
Roughness Profile ◽  
Before And After ◽  
Post Hoc

SUMMARY Objectives: This study evaluated the effect of toothbrushing with a dentifrice on gloss, roughness profile, surface roughness, and wear of conventional and bulk-fill resin-based composites. Methods and Materials: Gloss and surface roughness of resin-based composites (RBCs; Admira Fusion X-tra, Aura Bulk Fill, Filtek Bulk Fill Flowable, Filtek Bulk Fill Posterior Restorative, Filtek Supreme Ultra, Herculite Ultra, Mosaic Enamel, SDR flow+, Sonic Fill 2, Tetric EvoFlow Bulk Fill and Tetric EvoCeram Bulk Fill) were analyzed before and after brushing; the roughness profile and wear were also determined after toothbrushing. Representative three-dimensional images of the surface loss and images comparing the unbrushed and brushed surfaces were also compared. Analysis of variance and Tukey post hoc tests were applied (α=0.05) to the gloss, surface roughness, roughness profile, and surface loss data. Pearson's correlation test was used to determine the correlation between gloss and surface roughness, surface loss and percentage of gloss decrease after brushing, and surface loss and surface roughness after brushing. Results: For all RBCs tested after 20,000 brushing cycles, the gloss was reduced and the surface roughness increased (p<0.05). However, the roughness profile and the amount of surface loss were dependent on the RBC brand. Admira Fusion X-tra, Aura, Tetric EvoCeram Bulk Fill, and Tetric EvoFlow Bulk Fill showed the deepest areas of wear (p<0.05). A significant negative correlation was found between gloss and surface roughness, and a weak correlation was found between the decrease in gloss and the extent of surface loss, and any increase in surface roughness and the surface loss. Conclusions: Toothbrushing with a dentifrice reduced the gloss, increased the surface roughness, and caused loss at the surface of all the RBCs tested. Considering all the properties tested, Mosaic Enamel exhibited excellent gloss retention and a low roughness profile and wear, while Admira Fusion X-tra exhibited the greatest decrease in gloss, the highest roughness profile, and the most wear.

Using geomorphology to assess contour furrowing in western New South Wales, Australia

2011 ◽  
Vol 33 (2) ◽  
pp. 153 ◽  
Author(s):  
Gresley Wakelin-King
Keyword(s):  
Surface Roughness ◽  
Best Practice ◽  
Grazing Pressure ◽  
Post Treatment ◽  
Site Location ◽  
Treatment Management ◽  
Landscape Types ◽  
New Guidelines ◽  
Treatment Design ◽  
Geomorphic Processes

This study examines landscape rehabilitation treatments installed 20–40 years ago in the Western Catchment of NSW. Treatment outcomes were assessed using geomorphic criteria, because geomorphic processes are fundamental to ecological permanence. Contour furrowing creates artificial runoff-runon sets which intercept runoff (resistance to flow by windrows microrelief and surface roughness) and promote infiltration (artificial permeability by ripping). As originally conceived, after windrows subside, flow resistance would be afforded by surface roughness under belts of vegetation. This study shows that rehabilitation treatments have a more complex relationship with the landscape than this would suggest, and that the final effect of the treatment depends on the geomorphic processes natural to the site. Treatment design should therefore be site-specific. The relevant aspects of treatment design are site location, runoff : runon ratio (expressed as furrow spacing and furrow length), furrow placement, and post-treatment management. Some long-term successes are documented. In ironstone ridge country affected by impermeable hard-setting soils, furrowing creates artificial permeability, allowing plant germination; plant material in the soil reverses hard-setting and establishes self-sustaining permeability. In stony gilgai country furrowing through vegetated patches can aid in re-establishing vegetation, but furrowing through stony runoff patches only diminishes, rather than improves, landscape function. Other landscape types will have different key attributes. In all cases, selection of appropriate sites for rehabilitation treatment is of primary importance. The 1990s NSW Soil Conservation Service best-practice included a specialised furrower, surveying techniques for accurate furrow placement along the contour, staggered gaps along each furrow line to reduce risks of gullying by windrow breakthrough, and post-treatment management of total grazing pressure. New guidelines for treatment design developed from this study include determining for each site the optimum runoff:runon ratio (which varies according to climate, gradient, vegetation, and regolith), and matching furrow spacing and furrow/gap length to local runoff:runon ratios. In stony gilgai country, furrow placement should be along the contour but within non-stony patches; elsewhere, placement should be rigorously along the contour. In ironstone ridge country, a greater runoff:runon ratio, commensurate with the area’s apparently larger patch scale, can be achieved by having more gap than furrow along each furrow line. No single rehabilitation technique will fit all landscape types, and these guidelines will ideally be developed further with investigation of other landscapes.

scholarly journals The role of atmospheric boundary layer-surface interactions on the development of coastal fronts

2007 ◽  
Vol 25 (2) ◽  
pp. 341-360 ◽  
Author(s):  
D. Malda ◽  
J. Vilà-Guerau de Arellano ◽  
W. D. van den Berg ◽  
I. W. Zuurendonk
Keyword(s):  
Sensitivity Analysis ◽  
Surface Roughness ◽  
Land Surface ◽  
Mesoscale Model ◽  
Sea Surface ◽  
Precipitation Pattern ◽  
Surface Conditions ◽  
Frictional Convergence ◽  
Coastal Front ◽  
Thermal Difference

Abstract. Frictional convergence and thermal difference between land and sea surface are the two surface conditions that govern the intensity and evolution of a coastal front. By means of the mesoscale model MM5, we investigate the influence of these two processes on wind patterns, temperature and precipitation amounts, associated with a coastal front, observed on the west coast of The Netherlands in the night between 12 and 13 August 2004. The mesoscale model MM5 is further compared with available observations and the results of two operational models (ECMWF and HIRLAM). HIRLAM is not capable to reproduce the coastal front, whereas ECMWF and MM5 both calculate precipitation for the coastal region. The precipitation pattern, calculated by MM5, agrees satisfactorily with the accumulated radar image. The failure of HIRLAM is mainly due to a different stream pattern at the surface and consequently, a different behaviour of the frictional convergence at the coastline. The sensitivity analysis of frictional convergence is carried out with the MM5 model, by varying land surface roughness length (z0). For the sensitivity analysis of thermal difference between sea and land surface, we changed the sea surface temperature (SST). Increasing surface roughness implies stronger convergence near the surface and consequently stronger upward motions and intensification of the development of the coastal front. Setting land surface roughness equal to the sea surface roughness means an elimination of frictional convergence and results in a diminishing coastal front structure of the precipitation pattern. The simulation with a high SST produces much precipitation above the sea, but less precipitation in the coastal area above land. A small increment of the SST results in larger precipitation amounts above the sea; above land increments are calculated for areas near the coast. A decrease of the SST shifts the precipitation maxima inland, although the precipitation amounts diminish. In the situation under study, frictional convergence is the key process that enhances the coastal front intensity. A thermal difference between land and sea equal to zero still yields the development of the coastal front. A lower SST than land surface temperature generates a reversed coastal front. This study emphasizes the importance of accurate prescription of surface conditions as input of the numerical weather prediction model to improve coastal front predictability.

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