scholarly journals Application of Selective Induction Heating for Improvement of Mechanical Properties of Elastic Hinges

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2543
Author(s):  
Paweł Muszyński ◽  
Przemysław Poszwa ◽  
Andrzej Gessner ◽  
Krzysztof Mrozek
Keyword(s):  
Mechanical Properties ◽  
Injection Molding ◽  
Induction Heating ◽  
Polymer Melt ◽  
Mold Temperature ◽  
Polymer Processing ◽  
Mechanical Tests ◽  
Engineering Industry ◽  
Shear Rates ◽  
Molded Part

Injection molding is a polymer processing technology used for manufacturing parts with elastic hinges. Elastic hinges are widely used in FMCG (Fast Moving Consumer Goods) packaging (e.g., bottle closures of shampoos, sauces) and in the electrical engineering industry. Elastic hinge is a thin film that connect two regions of the injection molded part, where significant shear rates are present, which can lead to the degradation of polymers and the decrease in mechanical properties. Selective induction heating is the method that improves the flow of the polymer melt through thin regions by the local increase in mold temperature. In this study, selective induction heating was used to improve mechanical properties of elastic hinges by the reduction of material degradation due to high shear rates. To verify the change of shear rates, selective induction heating simulation and injection molding simulations were performed. The linear relation between mold temperature and maximum shear rate in the cross-section was identified and the mechanical tests showed significant differences in hinge stiffness, tensile strength and elongation at break.

scholarly journals Investigation of the Strength of Plastic Parts Improved with Selective Induction Heating

Polymers ◽  
2021 ◽  
Vol 13 (24) ◽  
pp. 4293
Author(s):  
Przemysław Poszwa ◽  
Paweł Muszyński ◽  
Krzysztof Mrozek ◽  
Michał Zielinski ◽  
Andrzej Gessner ◽  
...  
Keyword(s):  
Induction Heating ◽  
Mold Temperature ◽  
Engineering Industry ◽  
Shear Rates ◽  
High Shear Rates ◽  
Injection Molded ◽  
Thin Plastic ◽  
Number Of Cycles ◽  
Plastic Parts ◽  
Positive Effect

The use of selective induction heating of molding surfaces allows for better filling of molding cavities and has a positive effect on the properties of molded products. This is particularly important in the production of parts that include flexible hinges, which are thin plastic layers connecting two or more parts of the product. By using hinges, it is possible to expand the use of injection molding products and their capabilities. They are widely used in the production of parts for the electrical engineering industry and for packaging Fast Moving Consumer Goods (FMCG). The use of hinges also entails specific reductions in wall thickness. Increases in the shear rate can be expected, which can lead to the degradation of polymers and deterioration of mechanical properties of materials. This paper investigates injection molded flexible hinge parts manufactured with selective induction heating to improve their properties. To verify the efficiency of reduction of material degradation due to high shear rates, open/close tests of elastic hinges were performed. The linear relation between the number of cycles the hinges can withstand, mold temperature and injection time was identified, where mold temperature was the more significant factor.

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.

scholarly journals Prediction of the maximum flow length of a thin injection molded part

2020 ◽  
Vol 40 (9) ◽  
pp. 783-795
Author(s):  
Sara Liparoti ◽  
Vito Speranza ◽  
Annarita De Meo ◽  
Felice De Santis ◽  
Roberto Pantani
Keyword(s):  
Injection Molding ◽  
Maximum Flow ◽  
Mold Temperature ◽  
Complete Characterization ◽  
Rheological Parameters ◽  
Injection Molding Process ◽  
Spiral Flow ◽  
Molding Process ◽  
Molded Part ◽  
Flow Length

AbstractOne of the most significant issues, when thin parts have to be obtained by injection molding (i.e. in micro-injection molding), is the determination of the conditions of pressure, mold temperature, and injection temperature to adopt to completely fill the cavity. Obviously, modern computational methods allow the simulation of the injection molding process for any material and any cavity geometry. However, this simulation requires a complete characterization of the material for what concerns the rheological and thermal parameters, and also a suitable criterion for solidification. These parameters are not always easily reachable. A simple test aimed at obtaining the required parameters is then highly advantageous. The so-called spiral flow test, consisting of measuring the length reached by a polymer in a long cavity under different molding conditions, is a method of this kind. In this work, with reference to an isotactic polypropylene, some spiral flow tests obtained with different mold temperatures and injection pressures are analyzed with a twofold goal: on one side, to obtain from a few simple tests the basic rheological parameters of the material; on the other side, to suggest a method for a quick prediction of the final flow length.

Product Strength and Orientation Manipulation via Vibration-Assisted Injection Molding

2002 ◽  
Author(s):  
David C. Angstadt ◽  
John P. Coulter
Keyword(s):  
Thermal Conductivity ◽  
Tensile Strength ◽  
Injection Molding ◽  
Molecular Orientation ◽  
Polymer Melt ◽  
Polymer Processing ◽  
Shear Yielding ◽  
Processing Methods ◽  
Improve Product

This investigation focuses on determining why polystyrene ASTM specimens exhibit an increase in tensile strength when processed by vibration assisted injection molding (VAIM) while polycarbonate parts do not. VAIM is one of several polymer processing methods that attempt to improve product properties via manipulation of the polymer melt. Observation of birefringence patterns in VAIM processed polystyrene samples show a significant impact on molecular orientation. The same studies were conducted on opaque polycarbonate and were unable to determine the degree of molecular orientation via birefringence measurement. It was theorized that VAIM did not produce significant orientation due to its higher thermal conductivity and stiffer backbone. It has been determined by this investigation that VAIM processing does impart significant molecular orientation in polycarbonate specimens but still does not increase its UTS. It is proposed that increased molecular orientation induced by VAIM processing inhibits crazes from growing into cracks. VAIM therefore favors polymers that fail by crazing (e.g., polystyrene) rather than those that fail by shear yielding (e.g., polycarbonate).

Research on the Flow Characteristics of Polymer Injection Molding under Ultrasonic Vibration and Plastics’ Mechanical Strength

2010 ◽  
Vol 37-38 ◽  
pp. 1092-1100
Author(s):  
Ji Bin Li ◽  
Ke Ke Xu ◽  
Xin Bo Lin ◽  
Xiao Yu Wu ◽  
Guo Li Gao
Keyword(s):  
Mechanical Properties ◽  
Injection Molding ◽  
Ultrasonic Vibration ◽  
Flow Characteristics ◽  
Mechanical Tests ◽  
Impact Testing ◽  
Melt Flow Rate ◽  
Polymer Injection ◽  
Molding Method ◽  
The Impact

In this paper, ultrasonic vibration is adopted and exerted on injection molding in order to improve plastics’ forming ability, and the impact testing is used to analyze different injection parts’ mechanical properties. On the one hand, experiments prove that ultrasonic vibration can increase polymer’s melt flow rate, decrease melt viscosity, and improve injection flowing in mould cavity. On the other hand, the mechanical tests prove that the ultrasonic vibration can improve plastics’ tensile strength, elastic modulus and other mechanical properties. As a result, a weldless ultrasound-assisted injection molding method is recommended.

Influence of Injection Molding Parameters on Mechanical Properties of Low Density Polyethylene Filled With Multiwalled Carbon Nanotubes

2011 ◽  
Author(s):  
Catalin Fetecau ◽  
Felicia Stan ◽  
Daniel Dobrea ◽  
Dan Catalin Birsan
Keyword(s):  
Mechanical Properties ◽  
Carbon Nanotubes ◽  
Injection Molding ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Flow Direction ◽  
Mold Temperature ◽  
Low Density Polyethylene ◽  
Low Density ◽  
Melt Temperature

In this paper, we investigated the effect of injection molding parameters such as melt temperature, mold temperature, injection speed and holding pressure on the mechanical properties of low density polyethylene reinforced with 2.5 wt% multi-walled carbon nanotubes. The Taguchi methodology with four factors and two levels was used for the design of the injection molding experiments. The mechanical properties were evaluated by tensile tests in the flow direction at room temperature (23 °C) at crosshead speeds of 1 and 5 mm/min. It was found that the mechanical properties can be modified by manipulating the injection molding parameters. The Young’s modulus of the LDPE-MWNTs composite decreased as the melt temperature increased, while mold temperature, injection molding speed and holding pressure have a moderate influence on the Young’s modulus.

Influence of Processing Parameters in Reaction Injection Foam Molding for Multi-Layer Parts on Foam Structure and Mechanical Properties

2015 ◽  
Vol 805 ◽  
pp. 131-138
Author(s):  
Martin Löhner ◽  
Dietmar Drummer
Keyword(s):  
Mechanical Properties ◽  
Injection Molding ◽  
Chemical Reaction ◽  
Reactive Systems ◽  
Mold Temperature ◽  
Processing Parameters ◽  
Foam Structure ◽  
Blowing Agents ◽  
Reaction Injection Molding ◽  
Plastic Processing

Reaction injection molding is a plastic processing method to produce net shape parts using reactive systems. By integrating semi-finished products as inserts, complex multi-layer parts can be generated in highly integrative and energy efficient processes. The material by far mostly used is polyurethane, a polymer which results from the reaction of isocyanate and polyol. By adding blowing agents, like for example water, to the polyol component, foamed parts can be realized. In contrast to thermoplastic injection molding a chemical reaction takes part during molding within the cavity. Therefore the processing parameters have a significant effect on this chemical reaction and on the properties of the finished part.In this work the influences of different processing parameters like for example mold temperature and injection volume on the resulting foam structure are investigated for reaction injection foam molding. Therefore multi-layer parts based on polyurethane materials (thermoplastic and reactive) were molded varying relevant processing parameters. The foaming took place within an open cavity. The resulting foam structures were characterized using scanning electron microscopy (SEM). Additional the multi-layer parts were characterized mechanically to reveal the resulting effects on the mechanical properties of parts containing a foamed reactive polyurethane component.

Dynamic Mold Temperature Control Using Gas-Assisted Heating and Its Effect on the Molding Replication Qualities of Micro Channels

2008 ◽  
Author(s):  
Shia-Chung Chen ◽  
Yaw-Jen Chang ◽  
Jen-An Chang ◽  
Hsin-Shu Peng ◽  
Ying-Chieh Wang
Keyword(s):  
Injection Molding ◽  
Surface Temperature ◽  
Temperature Control ◽  
Heating System ◽  
Mold Temperature ◽  
Mold Surface ◽  
Water Heating ◽  
Molded Part ◽  
Micro Channels ◽  
Gas Heating

Dynamic mold surface temperature control (DMTC) has the advantage of improving molded part qualities without significant increases in cycle time. A gas-assisted heating system combined with water cooling was developed to achieve DMTC for injection molding. With gas-assisted heating, it takes 2s for the mold surface temperature to vary from 60 °C to 120 °C whereas it requires 186s using water heating. Further, it takes 21s and 84s for the mold surface to cool to 60 °C under gas heating and water heating, respectively. The gas-assisted heating system also shows excellent efficiency for micro injection molding of biochips to achieve high replication accuracy of the micro channels.

Application of a multilayer injection molding process for thick-walled optical components

2016 ◽  
Vol 36 (6) ◽  
pp. 557-562 ◽  
Author(s):  
Christian Hopmann ◽  
Malte Röbig
Keyword(s):  
Optical Properties ◽  
Injection Molding ◽  
Mold Temperature ◽  
Injection Molding Process ◽  
Molding Process ◽  
Optical Components ◽  
Considerable Potential ◽  
Cycle Times ◽  
Molded Part ◽  
Injection Molded

Abstract Nowadays, the injection molding of optical components is becoming more and more important. A process which constructs the injection-molded part in layers offers considerable potential for productivity increases in the manufacturing of thick-walled optical components. The so-called multilayer injection molding, also known as overmolding technology enables a considerable reduction of the normally long cycle times and improves the optical properties. It is even possible to increase the molding accuracy due to the lower shrinkage potential of the single layers. Contrary to experience, the influence of the mold temperature on the bonding strength is very low. So, the temperature control of the mold can be adapted to the process consideration in regard to optical characteristics.

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