In fact, hot runner systems are very complex and include all aspects of mechanical action, heating technology and precision manufacturing. The successful application of hot runner systems in the moulding environment requires detailed analysis of the inlet, cavity geometry, resin and moulding machine design.
During the initial application analysis, the following issues should be evaluated:
(1) Is it possible to mould this part?
(2) Is the pressure of the press sufficient to form the 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.
- 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. mould designers often use these programs to predict the injection pressure, flow path, porosity, shrinkage, and warpage of a part.
In the initial stage, as much as possible, computer-aided analysis is applied to the mould production project. Even a rough analysis performed at the initial stage may address important issues such as the possibility of injection moulding, production cycle time, pressure requirements and streamlined forecasts.
Computer engineering design software makes it easy to repeat simulations for different scenarios, helping to reduce production costs and test time.
Flow model programs are commonly used for part analysis, but the addition of hot runner manifolds during analysis has only recently appeared. Modeling the geometry of the manifold melt channels will help more accurate predictions. These software programs are also useful when you need to balance moulds with multiple cavity sizes.
The resin test is used to evaluate the processability of a resin composed of a certain component. Resin testing can be performed in practical applications. Only a small portion of these resins have been treated with hot runners or have not been treated at all.
The purpose of the resin test is to evaluate the process window for 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 of the 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 experimentally, and use the excellent inlet size and quality to determine the benchmark required for part production;
(4) Evaluate the sensitivity of the resin to the dwell time;
(5) Optimize each mould parameter and evaluate the entire application cycle.
In addition to standard test procedures, special tests can be performed to evaluate special processing parameters or requirements.
Prior to completing the mould design, resin testing allows customers to obtain the actual process data required before conducting the initial mould test and then provide samples of the moulded parts.
3.Design concept of hot runner system
Another important step is the design concept of the hot runner. Detailed design concepts, including manifolds and platens, will be an important part of the mould review.
Hot runner is a complex and excellent mould part. In mould production projects, hot runner system suppliers can complete CAE computer-aided engineering analysis, resin testing, and design concepts. At the beginning of the 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 are arranged in the most efficient manner. Ideally, the melt channels are designed symmetrically, with all downstream channels having the same flow length and turns. In the case of multi-cavity moulds or asymmetric moulds, the melt channel may contain artificial lengths and turning points to properly balance the system. This concept helps mould designers and hot runner designers 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 whether the inlet and cooling of the injection port can meet the requirements of the hot runner manufacturer.
The main factors for evaluating a hot runner system include: the flow balance and heat distribution of the manifold; and the channel size; the strength of the manifold material in high pressure applications; the size of the injection port; the distance between the coolant and the injection port; composition.
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