The demand for small and light parts has made thin-walled injection molding the most desirable performance of injection molding machines. "Thin wall" is usually defined by lightweight electronic parts whose thickness is less than 1mm. For large automobile parts, the "thin wall" can be 2mm. In short, thin-walled products require changing the processing technology: higher pressure and speed, shorter cooling time, changing the ejection and gate arrangement of the parts. The following are requirements for injection molding machines and moulds for thin-wall injection molding.

 

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注射机

Injection machine

 

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标准的注射机可用于生产多种薄壁制品。目前新型注射机的性能大大超过了 10 年以前。材料、浇口技术以及设计的进步，进一步拓宽了标准注射机对薄壁制件充模的性能。但由于壁厚不断减少，需要一种更特殊的、具有高速和高压性能的注射机。例如，一个厚度小于 1mm 的电子制件，充模时间小于 0.5 秒且注塑压力超过 210MPa 是很正常的。

The standard injection machine can be used to produce various thin walled products. At present, the performance of the new injection machine is much better than that of 10 years ago. The development of materials, gate technology and design has further widened the mold filling performance of standard injection molding machine for thin-walled parts. However, due to the continuous reduction of wall thickness, a more special injection machine with high speed and high pressure performance is needed. For example, an electronic part whose thickness is less than 1mm is normal when the filling time is less than 0.5 seconds and the injection pressure exceeds 210MPa.

 

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用于薄壁注塑的液压式注射机设计有储压器，可频繁地驱动注塑和合模。具有高速和高压性能的全电动注射机和电动/液压式注射机也面世了。为了能经受得住新型注射机的高压，锁模力的最小值必须是 5～7 吨/英寸（投影面积）。另外，当壁厚减少注塑压力增加时，大型模板有助于减少弯曲。薄壁制品用的注射机的拉杆对模板厚度的比为 2:1 或更低。生产薄壁制品时，注塑速度和压力以及其它加工参数的死循环控制有助于在高压和高速下控制充模和保压。

The hydraulic injection machine for thin-walled injection molding is designed with a pressure accumulating device, which can drive injection molding and clamping frequently. All electric injector and electric / hydraulic injector with high speed and high pressure are also available. In order to withstand the high pressure of the new injection molding machine, the minimum clamping force must be 5~7 tons / inch (projected area). In addition, when the wall thickness decreases, injection pressure increases, large formwork can help reduce bending. The ratio of the pull rod of the injection machine for the thin wall products to the template thickness is 2:1 or lower. In the production of thin-walled products, the dead cycle control of injection speed and pressure and other processing parameters helps to control mold filling and pressure holding at high pressure and high speed.

 

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至于注射量，大直径机筒往往太大了，建议的注射量为机筒容量的 40%～70%，薄壁制品总成型周期大大缩短，有可能将最小注射量减少到机筒容量的20%～30%。用户在注塑时必须十分小心，因为对材料来说，小的注射量意味着材料在机筒内的滞留时间更长，从而会导致制品性能的下降。

As for the injection amount, the large diameter cylinder is often too large. The recommended injection amount is 40% ~ 70% of the capacity of the cylinder, and the total molding cycle of the thin-walled products is greatly shortened. It is possible to reduce the minimum injection amount to 20% ~ 30% of the capacity of the machine barrel. The user must be very careful in injection, because the small amount of injection means that the retention time of the material in the barrel is longer, which will lead to a decline in the performance of the product.

 

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模具

mould

 

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速度是薄壁注塑成功与否的关键因素之一。快速充模和高压能以高速将熔融的热塑性材料注入模腔中，从而防止浇口冷固。如果一个标准的制件在两秒钟内完成充模，那么模厚减少 25% ，有可能将充模时间减少 50% ，刚好1秒。

Speed is one of the key factors in the success of thin-wall injection. Fast mold filling and high pressure can injecting molten thermoplastic material into the mold cavity at high speed, thereby preventing the gate from being cold and solid. If a standard workpiece is completed in two seconds, the die thickness will be reduced by 25%, and the filling time can be reduced by 50%, just one second.

 

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薄壁注塑的优点之一是当厚度减少时，需要冷却的材料更少。随着厚度减少，可以将成型周期缩短一半。熔体输送装置的合理设置使热流道和浇道不会妨碍成型周期的缩短。使用热流道和浇道衬套有助于将成型周期缩短至最小。此外，还应该考虑到模具用材。P20 钢被广泛应用于传统制品的模塑，但由于薄壁注塑的压力更高，模具必须制造得十分坚固。H-13 和其它硬钢为薄壁模具增加了额外的安全系数。然而，坚固模具的成本可能高于标准模具的 30%～40% 。但增加的成本通常会被提高的生产性能所抵消

One of the advantages of thin-walled injection is that when the thickness is reduced, there is less material to be cooled. As the thickness decreases, the forming cycle can be reduced by half. The reasonable setting of the melt conveying device makes the hot runner and runner not obstruct the shortening of the forming cycle. The use of hot runner and runner bushing helps shorten the molding cycle to a minimum. In addition, the mold material should also be taken into consideration. P20 steel is widely used in molding traditional products, but because of the higher pressure of thin-walled injection, the mold must be made very strong. H-13 and other hard steels add extra safety factor to thin-walled moulds. However, the cost of the sturdy die may be 30% to 40% higher than that of the standard mold. But the increased cost is usually offset by increased production performance.