Cooling channel design in the plastic injection moulding process is of paramount importance to the performance of the mould, influencing the quality of the parts being produced and productivity of ...the process. However, cooling channel design is usually limited to relatively simple configurations as well as conventional machining processes, such as straight-line drilling, and milling, etc. The cooling performance may not meet the expectations of the mould engineers.
This paper proposes an alternative design method for a conformal cooling passageway with multi-connected porous characteristics based on the duality principle. The proposed method can provide a more uniform cooling performance between the mould plate and the conformal cooling passageway than the existing conformal cooling channel design. Injection mould defects like warpage or hot spots can be avoided.
In this study, a 3D mould plate model was offset negatively and the location of the proposed multi-connected porous cooling passageway was identified. The negatively offset model was decomposed into a finite number of cubical cells via the sub-boundary spatial enumerated cell decomposition. Then a duality relationship between the primal and the dual graphs was developed. This provided the preliminary layout of the multi-connected porous passageway for the coolant flow in multiple directions. The cooling channel axis design of the multi-connected porous passageway, illustrated by the skeleton from the dual graph, was created. Following a Boolean difference operation, the proposed multi-connected porous cooling passageway inside the mould plate was able to be generated and fabricated with the aid of rapid tooling technologies. A real-life case study for the design of a multi-connected porous cooling passageway was implemented and examined. The effects of coolant flow and cooling performances, analyzed by computational fluid dynamics simulation, were validated.
► Traditional cooling channel design in injection moulding is usually limited to relatively simple configurations. ► The cooling performance may not meet the expectations of the mould engineers. ► A conformal cooling passageway with multi-connected porous characteristics based on the duality principle is proposed. ► The multi-connected porous cooling passageway design is formed by sub-boundary spatial enumerated cell decomposition. ► The proposed design provides a more uniform cooling performance than the existing conformal cooling channel designs.
Vacuum forming is one of the simplest means of manufacturing thin plastic parts wherein a heated plastic sheet is sent through the mould by creating a vacuum between part and mould to get the desired ...shape. The mould used in vacuum forming process gets heated upon continuous production which has to be cooled continuously to produce parts without affecting quality. In this paper, the currently available techniques to cool the mould viz. Chill plate attachment method, straight drilled cooling channels are studied. Finite Element Analysis is carried out on various methods of mould cooling. Temperature distribution is the criteria considered to evaluate the results of each case. The results have demonstrated that the straight drilled cooling channels are better in comparison with the chill plate attachment method of mould cooling. The concept of conformal cooling channels designed based on part shape has also been introduced and studied to reduce the cooling time of the mould which is found to have a fair temperature distribution amongst the three mould cooling methods.
During an injection moulding process, it is very difficult to achieve efficient and balanced cooling. It is also difficult to generate an optimal cooling design for industrial parts automatically. In ...this paper, a milled groove insert method in mould cooling was proposed for cooling of medium and large plastic parts. The advantages of this method include a better cooling effect, ease and flexibility of design, characteristics of auto-design and considerable savings on the coolant flow rate. A household iron part was studied and the assemblies were modelled. The cooling analyses of the mould assembly and thermal stress analysis of plastic parts were performed using ABAQUS/Standard to compare the proposed method to the most popular straight-drilled cooling channel method. The thermal stress analysis was run, consequently, based on the result of the cooling analysis. Simulation results have confirmed the merits of the milled groove insert method.
One of the basic problems in the development and production process of moulds for injection moulding is the control of temperature conditions in the mould. Precise study of thermodynamic processes in ...moulds showed, that heat exchange can be manipulated by thermoelectrical means. Such system upgrades conventional cooling systems within the mould or can be a stand alone application for heat manipulation within it.
In the paper, the authors will present results of the research project, which was carried out in three phases and its results are patented in A686\2006 patent. The testing stage, the prototype stage and the industrialization phase will be presented. The main results of the project were total and rapid on-line thermoregulation of the mould over the cycle time and overall influence on quality of plastic product with emphasis on deformation control.
Presented application can present a milestone in the field of mould temperature and product quality control during the injection moulding process.
The quality of spin cast products and mould life are critically dependent on the thermal conditions they are exposed to. An investigation was carried out on the effect of air-cooling induced by the ...spinning of the mould and its consequences on the thermal process. A system was developed to optimise the thermal process during casting, utilising a theoretical analysis of the air-flow characteristics in a cooling tube submerged in a silicon mould and the characteristics of convection heat transfer associated with the mould and cast part. A numerical simulation of the casting process was also used in this process. The effect of the developed system on the thermal process was determined experimentally and it was found that a system of air-cooling, automatically induced from the spinning of the mould, is feasible in optimization of the thermal process.
Abstract
In the injection moulding process, productivity and part quality depend largely on the cooling system of the injection mould. Several cooling methods are being adopted by the mould industry, ...with the straight-drilled cooling channels method being the most popular. Many reported research activities have been based on this method, but the method has several limitations that prevent it from achieving efficient and uniform cooling. In the present work, a U-shape milled groove method was proposed for large and complicated parts, especially for parts with large free-formed surfaces. Simulations were made to compare the cooling effect of U-shape milled grooves with that of straight cooling channels using COSMOS/DESIGNSTAR, an analysis software based on the finite element method (FEM). The heat flux was calculated on a cycle-averaged basis and the natural convection between ambient air and the exterior mould surface was ignored. A mouse cover was used as a case study. The U-shape milled grooves were found to have better temperature control than straight cooling channels. The temperature distributions of the core and cavity with U-shape milled grooves were more uniform than with straight cooling channels. Moreover, the U-shape milled grooves removed the heat efficiently; the mould temperature was lower than that with straight cooling channels. The U-shape milled grooves method has demonstrated its advantages in mould cooling. Although U-shape milled grooves need to be machined using computer numerical control (CNC) machines and more machining time is required, making them more expensive than straight cooling channels, their potential benefits will be explored for practical applications.
The control and management of heat in injection mould tools is a vital requirement for obtaining optimum production processing conditions. This paper describes an investigation that compared ...conventional mould cooling methods with a relatively new technique called 'pulse cooling technology' (PCT). The principle of PCT is the use of an intermittent flow of the cooling medium in the mould tool with accurate control of the mould cavity surface temperature during the injection moulding cycle.
A mould tool instrumented for cavity pressure, cavity surface temperature and mould background temperature measurements was constructed for the study. Results showing the effectiveness of PCT compared with conventional cooling are presented for polypropylene (PP), polycarbonate and filled PP with talc and aluminium powders. A reduction of up to 22% of the conventionally cooled moulding cycle time for unfilled PP has been recorded when pulsed mould cooling was used.
Cooling in the continuous casting mold is the essential process of the molten steel solidifying into a slab shell. The synergistic relationship of casting state, process operation, continuous casting ...equipment, and other factors is complex and has a significant influence on thermal transfer in the mold. Therefore, a concept of "process thermal dissipation rate" defined by mold system thermal input and output was proposed in this work. The thermal input of molten steel was calculated through the casting temperature, and the slab residual thermal at the outlet of the mold was calculated by the solidification heat transfer model. Consequently, the thermal dissipation rate was calculated to quantify the multi-factor cooperative relationship of mold. The industrial case reflected that the thermal dissipation rates of three stable castings were 12.5%, 14.3%, and 18.8%, respectively, and all of them were obviously abnormal in unsteady casting such as start casting, changing tundish, and end casting. The results above indicated that the thermal dissipation rate could characterize the mold cooling target under the cooperation of complex factors and provide a new method for the dynamic evaluation of the mold system cooling effect with different casting states. Accordingly, the correlation analysis between superheat, casting speed, cooling water flow, and thermal dissipation rate revealed the synergistic influence law of multi-operation on mold cooling effect, which provided a new idea for the precise control of multi-process collaboration in continuous casting.
Energy use by thermoplastics injection molding machines is estimated to result in global CO2 emissions in the order of 80 million metric tons annually. Shortening the molding cycle time is a key ...factor in improving energy efficiency and since cooling occupies a major part of the cycle, effective design and operation of cooling systems is essential. While guidelines exist, there is a lack of quantitative generic information to complement these. To provide this, a parametric study of mold tool cooling is carried out using numerical simulations, examining coolant channel layout, coolant flowrate and temperature, and tooling thermal properties. Briefly, some findings for representative cases include:
Within recommended guidelines for coolant channel layout (channel diameter, pitch and distance from the cavity) cooling time for the worst case was found to be 70% longer than for the best.
Reduction of coolant temperature by 5 °C (35 °C to 30 °C) allows reduction of coolant flowrate by a factor of more than two while keeping the cooling time unchanged.
Use of an aluminum tooling alloy reduces cooling time, as compared with tool steel, by about 30% (15 s–10 s in an example) across a range of coolant flowrates and temperatures.
If the maximum plastic temperature variation on ejection is to be no more than 5 °C, coolant channel pitch should be less that 50 mm when the channels are 10 mm from the cavity, and 80 mm when at 20 mm.
A coolant heat transfer coefficient of 5,000 W/m2K is recommended. This corresponds to a Reynolds number of 10,000 in a coolant channel of 10 mm diameter.
The effectiveness of higher heat transfer coefficients is limited by the thermal resistance of the tool and rapidly increasing pumping costs.
Cooling times can be collapsed onto a single line when plotted against an overall thermal resistance that takes into account the coolant channel layout, tooling thermal conductivity, and coolant heat transfer coefficient.
A widely promoted formula for cooling time is found to be inadequate and an improved formula incorporating this overall thermal resistance provides better estimates.
The need for careful balancing of opposing effects to optimize energy use in cooling is emphasized. The present results will assist with this in the early-stage design, with the aim of shortening cycle time to better amortize base loads. Furthermore, insights gained will be valuable in providing better estimates of cooling time for predictions of productivity, energy use and environmental impacts.
In this contribution, the effectiveness of helical static mixers in different arrangements and flow configurations/regimes is explored. By means of a thorough numerical analysis, the application ...limits of helical static mixers for the heat transfer enhancement inside cooling channels of machine tools are provided. The numerical simulations were processed with the commercial finite volume Computational Fluid Dynamics (CFD) code, ANSYS Fluent 2020 R2. This study shows that there exists an optimal range of application for static mixers as heat exchange intensifier depending on the flow speed, the transmitted heat flow and the thermal conductivity of the tool. The investigations of this contribution are restricted to single-phase flow in circular cross-sections and straight channel geometries. As a representative application example for a machine tooling, the cooling of a simple injection mold is investigated. The research carried out reveals that the application of static mixing elements for enhancement of heat transfer is very effective, particularly for fluid flow with low to medium Reynolds numbers, close-contour cooling, high values of heat fluxes, and high thermal conductivity of the tooling material.
