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In fact, the hot runner system is very complicated, inc […]
In fact, the hot runner system is very complicated, including all aspects of mechanical action, heating technology and precision manufacturing. The successful application of the hot runner system in the moulding environment requires a detailed analysis of the design of the injection port, cavity geometry, resin, and mould workers.
During the initial application analysis, the following issues should be evaluated:
(1) Can this part be moulded?
(2) Is the pressure of the press sufficient to press-mould this part?
(3) Is the entire moulding process reliable?
Application Analysis of Hot Runner System
The three main steps involved in application analysis include: computer-aided engineering analysis, resin testing, and design of the hot runner concept.
1.Computer Aided Engineering (CAE) Analysis
Computer-aided engineering analysis tools, including mouldFlowTM analysis software, can be used to analyze the flow of molten plastic in mould systems. These programs are often used by mould designers to predict part injection pressures, flow paths, porosity, shrinkage, and warpage.
Whenever possible, apply computer-aided analysis to mould production projects at the initial stage. Even the rough analysis done at the initial stage may solve some important problems, such as the possibility of injection moulding, production cycle time, pressure requirements, and prediction of flow lines.
With the help of computer engineering design software, it is easy to repeat simulation demonstrations for different scenarios, which is beneficial to reducing production costs and test time.
It is very common to use a flow model program for part analysis, but the addition of hot runner manifolds during analysis has only recently emerged. Modeling the geometry of the manifold melt channels will facilitate more accurate predictions. Moreover, these software programs are useful when you need to balance a mould with multiple cavity sizes.
The resin test is used to evaluate the processing performance of a resin configured with a certain composition. Resin testing can be carried out in practical applications. Only a small part of this type of resin has been treated with hot runners or has not been treated at all.
The purpose of designing the resin test is to evaluate the process window of the resin and each component combination. The basic steps of the test are as follows:
(1) Evaluate the injection speed and corresponding pressure, and determine the injection time for this test;
(2) Establish the temperature window of the hot runner system, which is conducive to the production of parts that meet the requirements;
(3) Change the holding time and pressure in the form of experiments, use the excellent size and the quality of the injection port to determine the baseline required for the production of parts;
(4) evaluate the sensitivity of the resin to dwell time;
(5) Optimize each mould parameter and evaluate the total application cycle.
In addition to standard test procedures, special tests can be performed to evaluate special processing parameters or requirements.
Before completing the mould design, the resin test allows the customer to obtain the actual process data required before the initial mould test, and then provides samples of the moulded parts.
3.Design concept of hot runner system
Another important step is the design concept of the hot runner. A detailed design concept, including manifolds and platens, will be an important part of the mould review.
Hot runner is a kind of complex and superior mould parts. In mould production projects, CAE computer-aided engineering analysis, resin testing, and design concepts can be completed by the hot runner system supplier. At the beginning of a project, if hot runner suppliers are involved, the mould designer can further optimize the final product.
The manifold is used to ensure that the melt channels can be arranged in the most efficient manner. In the ideal case, the melt channel is designed in a symmetrical manner, and the flow length and the number of turns of all the downflow channels are consistent. In the case of multi-cavity moulds or asymmetric moulds, the melt channel may include artificial lengths and turning points to properly balance the system. This concept is helpful to both mould designers and hot runner designers to ensure excellent manifold design.
In addition, pressure plate technology is used to ensure that the closing height and key characteristics required by the customer can be designed. Since the hot runner nozzle is included in the nozzle, the mould designer also needs to confirm that the access and cooling of the injection port can meet the requirements of the hot runner manufacturer.
The main factors for evaluating the hot runner system include: the flow balance and the heat distribution of the manifold; the channel size; the strength of the manifold material in high pressure applications; the size of the injection port; the proximity of the cooling and the injection port; Composition of corrosive resin.
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