Die casting machine is the key equipment of die casting production. The correct selection of die casting machine is very important to ensure the quality of zinc alloy die castings, improve production efficiency, reduce production costs and ensure production safety, so it should be carefully selected.
To choose a die casting machine correctly, first of all, we should choose a die-casting machine suitable for the production of a given product from the hands of the product. At the same time, among many die-casting machine brands, choose machines with appropriate performance, specifications and prices.
(1) Select according to the alloy type of the product
Die casting machines are usually divided into two categories: cold chamber and hot chamber. The cold chamber machine is mainly used to produce die castings of copper, aluminum and magnesium (thick wall) alloys with high melting point. Hot chamber machine is used to produce die castings of zinc, tin, lead and magnesium (thin wall) alloys with low melting point.
Compared with the cold chamber machine, because the injection chamber of the hot chamber machine works directly in the alloy melt, the pouring operation can be omitted, so the working cycle is short and the working efficiency is high; Since the molten metal is added into the injection chamber from below the liquid level, it is difficult for molten slag to enter. During injection, the injection chamber is full of molten metal, which will not produce air entrainment like the cold chamber machine. Therefore, using the hot chamber machine to produce zinc alloy and other die castings, the product quality is also high.
It is common for some die-casting factories to produce zinc alloy die castings with household cold chamber machines. After careful analysis, it can be found that this is not economical. Because the production efficiency of the cold chamber machine is lower than that of the hot chamber machine, and the machine occupation time in production is much longer, the apportionment of energy consumption expenses, labor wages, site expenses, equipment depreciation, etc. will be doubled in terms of the production cost analysis of a single product; Moreover, the quality of zinc alloy die castings produced by cold chamber machine is also worse. Therefore, it is very uneconomical, and the hot chamber die casting machine should be selected as far as possible to produce zinc alloy die castings.
(2) Select by product weight
Due to the heavy weight of the product and the large amount of metal required, a die-casting machine with sufficient metal pouring volume should be selected. When selecting the die casting machine according to the weight of the product, it is recommended to control the required metal pouring amount – the sum of the product weight and the metal weight required by the overflow system within the range of 30% – 70% of the maximum metal pouring amount of the die casting machine, so as to obtain high-quality zinc alloy die castings.
For smaller products or products with a large range of weight changes, it is recommended to choose a die casting machine with larger specifications in consideration of compatibility. In this way, it can not only meet the needs of larger product production, but also adopt the mode of the first mock examination and multiple pieces in the production of small products, which greatly improves the production efficiency.
When only a few products are heavy, the production demand can be met by selecting the injection chamber (gooseneck pot) with a slightly larger inner diameter.
(3) Select according to the outline size and structure of the product
For disc and plate-shaped die castings, due to the large projection area, a die-casting machine with sufficient clamping force should be selected to ensure the safety of production.
For products with large outline size, the overall dimension of the die-casting mold is also large. Therefore, in addition to considering the mold locking force, attention should also be paid to whether the mold holding space of the die-casting machine is sufficient and whether the clearance size after mold opening is sufficient to take the workpiece out of the die-casting mold.
For products with complex shape and structure, a core pulling device should be set on the mold to greatly increase the overall size of the mold. It is necessary to check whether the mold holding space of the machine is sufficient.
(4) Select according to the quality requirements of the product
If the quality of the product is high, the die-casting machine with excellent performance should be selected.
In the process of die casting, defects such as pores and slag inclusions will inevitably occur. There are many reasons for defects, but sometimes it is caused by the insufficient performance of the die-casting machine. For products with high internal strength requirements or high external decoration requirements, if you use a die-casting machine with insufficient performance, it cannot meet the requirements.
Generally, there is no such index in the product manual of die-casting machine, but it can be compared according to the working pressure index of its hydraulic system. If the rated pressure of the die casting oil pump is high, its injection pressure can be higher, and the liquid metal may obtain a higher injection specific pressure and inner gate speed, so as to meet the needs of the die-casting parameters of high-quality die casting, so as to obtain quality and high-quality zinc alloy die casting.