How to determine the process for purchasing aluminum alloy castings between low-pressure casting and die-casting?
There is a significant difference in the forming paths between low-pressure casting and die-casting, with boundaries for yield, cost, and airtightness. Xinfeng Machinery has organized and compared dimensions to facilitate overseas procurement in determining suitable processes.
1、 Differences in Filling Principles and Efficiency between Two Processes
Die casting relies on high pressure and high speed to fill aluminum liquid into the mold cavity, and the single piece molding cycle can be compressed to within 45 seconds, suitable for large quantities of thin-walled shell parts. Low pressure casting relies on the slow rise of liquid level low pressure for filling, with a typical cycle time of 2-5 minutes. The filling process is smooth and the probability of gas entrapment is significantly reduced. Aluminum alloy parts with an annual output of less than 50000 pieces and high air tightness requirements have a more prominent advantage in the comprehensive quality of low-pressure processes.
2、 Internal quality and defect tendency of castings
Die cast parts are prone to air entrapment inside, and bubbles expand and bulge during heat treatment. Industry statistics show that the airtight pass rate of conventional die cast parts is about 76%. The filling sequence of low-pressure casting is from bottom to top, making it easier for the gas in the mold cavity to be discharged. The pass rate of airtightness testing for A356 castings of the same material can reach 94%. As a load-bearing safety component, alloy wheels are mostly prioritized for low-pressure casting technology by overseas OEMs.
3、 Comparison of mold investment and single piece cost sharing
The cost of opening a low-pressure mold for an alloy wheel mold of the same specifications is about 18% lower than that of a high-speed die-casting mold, but the single piece cycle is slower and the labor energy consumption is shared more. When the annual demand for orders exceeds 120000 pieces, the high efficiency of die-casting will offset the premium of molds, and the production cost per piece will exceed the low pressure solution. Many small and medium-sized buyers only look at the mold quotation, ignoring the cost difference caused by the long-term production pace.
4、 Applicable product boundary division
Die casting is more suitable for aluminum castings with simple structures and no strict airtight requirements, such as motor housings, valve housings, and heat dissipation shells. Low pressure casting is commonly used for wheel hubs, hydraulic valve bodies, and new energy water-cooled chambers. These parts require continuous pressure, and internal porosity is a fatal defect. Metal injection mold does not participate in the forming of large aluminum alloy parts and is only used for small powder metallurgy parts. When purchasing, it is necessary to distinguish between die and mold definitions.
5、 Differences in customer preferences in overseas markets
The European and American automotive supply chains have strict control over wheel hub airtightness, with a higher proportion of low-pressure casting inquiries; The Southeast Asian two wheeler market pursues low prices, with a larger volume of die-casting wheel hub orders. In B2B platform searches, "low pressure casting vs die casting" is a high intention comparison term, and visitors are mostly procurement engineers with a close conversion distance. An independent website can build a special page for the comparative word to receive Google Q&A traffic.
FAQ
Can low pressure castings undergo T6 heat treatment? Sure, it has fewer internal pores and is less prone to bubbling after heat treatment, making it a preferred option for safety components.
Can the porosity of die-casting parts be solved by later infiltration? Micro pores can be infiltrated and sealed, while the infiltration effect of large volume pores is unstable, and there is a risk of leakage under long-term pressure.
Can die-casting molds be changed to low-pressure molds? The amount of structural modification is large, and the logic of pouring, exhaust, and ejection is completely different. The cost of modification is close to that of opening a new mold.
Why is the die-casting process for aluminum alloy wheels less commonly used? Wheel hubs are subjected to alternating loads, and internal porosity defects in die-casting can easily lead to fatigue fracture, resulting in many restrictions on the entry of host manufacturers.
What is the typical pressure for low-pressure casting? The liquid level pressure rise is usually controlled at 0.02-0.06MPa, and the pressure parameters need to be matched with the cavity height.
Is there a significant difference in surface roughness between the two processes? The surface formed by die-casting is smoother; The surface of low-pressure castings will have more flow patterns, and there will be more subsequent polishing processes.
Is low-pressure casting suitable for thin-walled parts? Thin walled parts below 2mm have high filling difficulty and insufficient flow capacity, so die-casting technology is preferred for thin-walled parts.
Is the maintenance frequency of low-pressure casting molds high? The thermal shock is gentle, the crack development is slow, and the annual maintenance frequency is reduced by about 40% compared to die-casting molds.
Copyright © Zhejiang Xinfeng Machinery Co., Ltd. All Rights Reserved.