How to Make Injection Molds

Advances in rapid prototyping and machining have resulted in reduced lead times for injection moulding tooling. Comparisons between aluminium and stereolithography (SL) tools are made with regard to the ejection forces required to push mouldings from the tools, heat transfer through the tools and the surface roughness of the tools. The results show that ejection forces for both types of tools are increased when a longer cooling time prior to ejection is used. The ejection forces required from a rough aluminium tool are considerably higher than those from a smooth aluminium tool. SL tools do not appear to be subjected to any smoothing as a result of moulding polypropylene parts. The rubber like nature of the tool’s surface is as a direct consequence of the low glass transition temperature and low thermal conductivity of the tool material. Further potential benefits of the low thermal properties of the tool are discussed.

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“…The ejection force is determined by a number of factors and an equation to predict it has been developed (Menges, 1986):…”

Section: Methodsmentioning

confidence: 99%

A comparison between stereolithography and aluminium injection moulding tooling

Hopkinson

Dickens

2000

Rapid Prototyping Journal

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“…This shrinkage causes stress to build up in the cross section of the part [1] and results in the generation of forces normal to the surfaces restrained from shrinking. The stresses which develop are strongly related to normal pressure and therefore to shrinkage, part stiffness and mould packing.…”

Section: Demoulding Stressesmentioning

confidence: 99%

“…Bhagavatula et al [15] compared results from the Menges and Mohren model [1], an ANSYS simulation and experimental results. A cylindrical canister with a height of 49.5, thickness of 0.5 and inner-radius of 15mm was moulded.…”

Section: Injection Mouldingmentioning

confidence: 99%

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Demoulding Force Prediction for Micro Polymer Replication: A Review of Relevant Literature

Delaney¹,

Bissacco²,

Kennedy³

2010

Proceedings of the 7th International Conference on Multi-Material Micro Manufacture

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Demoulding components without damage to either the components or tool is critical to successful replication processes. During tooling development designers strive to optimize replication tools to minimize demoulding force and resultant stress on replicated parts. A critical element of this process is an accurate demoulding force prediction model. Various models have been proposed to predict demoulding forces, each showing limitations in its applicability. This paper reviews existing demoulding force models and parameters affecting demoulding force for micro polymer replication.

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“…Ferreira et al [2] presented a framework, based on a Multidisciplinary Design Optimization Methodology (MDO), which tackles the design of an injection mold by integrating the structural, feeding, ejection and heat exchange subsystems to achieve significant improvements, they also perform multiple objective optimization simultaneously minimizing cycle time, wasted material and pressure drop, however they assumed that the value of the injection time is very small compared to the other times and they considered it as a constant value. Ramos et al [3] presented a global optimization strategy for the injection molding cycle time, covering all time steps related to the injection molding process, including a novel mathematical model to predict the ejection time, however they perform calculations of injection time in the area of the cavity assuming a constant thickness of the piece (not always the part has a constant thickness) and assuming a constant value of viscosity (when this value is variable within the cavity), moreover they calculate the packing and cooling time in an isolated manner, when it has to be noted that the real cooling time (Menges and Walter [4]) includes packing time. This paper proposes a new model to calculate cycle time and an alternative method to calculate injection time, which focuses on the mold feeding system modeling.…”

Section: Introductionmentioning

confidence: 99%

Analytical calculation model for determining the cycle time in injection molding parts applied to design optimization algorithms

Colmenero¹,

Lázaro²,

Doñate³

et al. 2016

WIT Transactions on the Built Environment

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Determining the cycle time required to perform plastic parts has an important impact and relevance along the process of mold design, as well as in the cost per part. A great number of mold dimensioning algorithms and cost estimation methods use the cycle time as a main design parameter. This paper presents the results of an analytical study aimed to determine the most representative variables of the problem and how they influence in the magnitude of the cycle time. The model has been validated comparing the numerical results with the solution provided by the software Autodesk Simulation MoldFlow Advisor in several case studies. On the other hand, analytical and numerical results have been compared with dates provided by an industrial model, showing as a result a significant improvement of the accuracy of calculations. This method is intended as a complement to the use of optimization applications that require the use of a non-numerical, analytical and low computational time calculation model for determining this parameter.

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How to Make Injection Molds

Cited by 179 publications

References 0 publications

A comparison between stereolithography and aluminium injection moulding tooling

A comparison between stereolithography and aluminium injection moulding tooling

Demoulding Force Prediction for Micro Polymer Replication: A Review of Relevant Literature

Analytical calculation model for determining the cycle time in injection molding parts applied to design optimization algorithms

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