The need to produce small and light parts has made thin-wall injection molding the most desirable performance of injection molding machines." "Thin-wall" is usually defined by lightweight electronic components with a wall thickness of less than 1mm. For large automotive components, "thin wall" can be 2mm. In short, thin-walled parts require changes in machining processes: higher pressures and speeds, shorter cooling times, changes in ejection and gate alignment. The following are the requirements of thin-wall injection molding for injection machines and molds.

Standard injection machine can be used to produce a variety of thin-wall products. At present, the performance of the new injection machine is much better than that of 10 years ago. Advances in materials, gate technology and design have further broadened the ability of standard injection machines to fill thin-walled parts. However, due to the decreasing wall thickness, a more special injection machine with high speed and high pressure performance is needed. For example, for an electronic part with a thickness of less than 1mm, it is normal for the filling time to be less than 0.5 seconds and the injection pressure to exceed 210MPa.

Hydraulic injection machines for thin-wall injection molding are designed with a pressure reservoir to drive the injection molding and the mold frequently. An all-electric injection machine with high speed and high pressure performance and an electric/hydraulic injection machine are also available. In order to withstand the high pressure of the new injection machines, the minimum clamping force must be 5 to 7 tons/inch (projected area). In addition, the large formwork helps to reduce bending when the wall thickness reduces injection pressure increases. Injection machines for thin-walled products have a tie rod to formwork thickness ratio of 2:1 or less. Closed-loop control of injection speed and pressure, as well as other processing parameters, helps to control mold filling and pressure retention at high and high pressures when producing thin-walled products.

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

Mold

Speed is one of the key factors for the success of thin-wall injection molding. Fast mold filling and high pressure can inject the molten thermoplastic material into the mold cavity at high speed, thus preventing the gate from cold setting. If a standard part is filled in two seconds, then a 25% reduction in mold thickness has the potential to reduce mold filling time by 50%, to exactly 1 second.

One of the advantages of thin-wall injection molding is that less material needs to be cooled when the thickness is reduced. As the thickness is reduced, the molding cycle can be cut in half. The reasonable setup of melt conveying device makes hot runner and runner not hinder the shortening of molding cycle. The use of hot runner and runner bushing helps to shorten the molding cycle to a minimum.

In addition, mold materials should be taken into account. P20 steel is widely used in the molding of traditional products, but because of the higher pressure of thin wall injection molding, the mold must be made very strong. H-13 and other hard steels add an extra factor of safety to thin-walled molds. However, the cost of a strong mold can be 30 to 40 percent higher than a standard mold. But the increased cost is usually offset by the improved production performance.

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