Aluminum casting & mold design services

For executives in the manufacturing industry, as well as procurement and purchasing managers, stabilizing the quality, cost, and delivery times of aluminum casting (especially die casting) is a critical issue that can shake the very foundations of business. It is no exaggeration to say that 90% of a product’s quality is determined by its “mother,” the mold. However, when these molds encounter troubles such as “wear,” “deformation,” and “breakage,” production lines stop, mountains of defective products pile up, and it directly leads to delivery delays and massive cost increases. This article will unravel the serious mechanisms behind why these troubles are unavoidable in aluminum molds. Furthermore, it will provide practical hints for solving this deep-rooted problem from new perspectives: the limitations of conventional measures and supply chain diversification (especially overseas procurement).

Before considering countermeasures for aluminum mold troubles, we must first grasp the current situation of our domestic mold industry using objective data. Japan’s mold industry, which boasted the world’s highest level of technology and production value during the bubble economy period, is now facing a major turning point.

According to statistics from the Japan Die & Mold Industry Association (JDMIA), Japan’s mold production value hit a record high of 1.9575 trillion yen in 1991 (Heisei 3). However, due to the subsequent long-term economic slump and the rise of overseas manufacturers, it fell to 1.4004 trillion yen in 2021 (Reiwa 3), a decrease of about 28% from its peak (Source: Japan Die & Mold Industry Association).

Behind this lies not only the hollowing out of domestic manufacturing but also structural problems within mold manufacturers. A survey by the Ministry of Economy, Trade and Industry (METI) shows that Japan’s mold industry is an aggregation of small enterprises, with 90% of businesses having 20 or fewer employees (Source: METI). While these companies possess high technical capabilities, they suffer from a shortage of successors, delays in capital investment, and intensifying price competition. As a result, the number of business establishments has decreased by 64% compared to 1986 (as of 2021) (Source: Japan Die & Mold Industry Association).

Looking at Japan’s mold production value by demand industry, the share for “automobiles” is overwhelmingly large, accounting for 73.7% (Source: JDMIA “Mold Statistics”). While this is proof that Japan’s mold technology has evolved alongside the development of the automotive industry, it also harbors the structural risk of relying on a specific industry.

In recent years, the automotive industry has been facing a once-in-a-century transformation known as “CASE” (Connected, Autonomous, Shared, Electric). With the advancement of electrification (EVs), conventional engine-related parts are decreasing, while the demand for large, high-precision aluminum die-cast parts related to motors and batteries is rapidly increasing. This change demands a different level of durability and precision from molds than ever before, and there are increasing cases where existing technologies and equipment cannot cope. For procurement managers, this change in industrial structure directly impacts them as capacity shortages and rising costs from domestic suppliers.

Molds are often written off as “consumables,” but the way they wear out (= troubles) is not uniform. In particular, die-casting molds for aluminum (melting point approx. 660°C) are exposed to an extremely harsh environment of high temperature, high pressure, and high speed. Understanding the physical and chemical mechanisms behind the troubles is the first step toward appropriate countermeasures.

“Wear” is a general term for the phenomenon where the mold surface is worn down or gouged. In aluminum molds, wear mainly occurs in three forms:

In a short cycle of just tens of seconds, the mold withstands the impact of molten metal over 600°C being injected at high pressures of tens to 100 MPa (Megapascals). Due to the stress from this heat and pressure, if the mold material exceeds its yield point (the limit beyond which it cannot return to its original shape), “plastic deformation” occurs.

A particular problem is the “setting” (Hetari) of the mold. Repeated exposure to high temperatures causes the mold material’s hardness (high-temperature strength) to decrease, and deformation gradually progresses. This not only worsens the dimensional accuracy of the product but also creates gaps on the mold’s mating surfaces (parting line), causing burrs (excess aluminum extruding from the product’s edge).

The most fatal trouble is “breakage,” namely cracks. There are two types, large and small:

Various countermeasures are taken on-site against these troubles. However, procurement managers in the manufacturing industry may feel the dilemma that troubles are still not eradicated.

The root cause of heat checking is the “repetition of heating and cooling,” but this is absolutely unavoidable in producing products. The more productivity is increased (higher cycle times), the more severe this thermal shock becomes. In other words, productivity improvement and mold life are in a trade-off relationship.

Furthermore, mold release agents are indispensable for making it easier to remove products from the mold, but spraying a water-based release agent onto a hot mold is like “splashing (room temperature) water onto boiling water” for the mold, and it is one of the biggest factors that promotes heat checking.

Many mold troubles can be preempted and their life extended through regular maintenance (cleaning, inspection, welding repair of fine cracks, etc.). However, as the domestic mold industry becomes fatigued, the number of suppliers who can maintain an adequate maintenance system is decreasing.

According to a survey by the Small and Medium Enterprise Agency, regarding mold price payments, about 80% of “installment payments” and about 60% of “add-ons to the product unit price” require 13 months or more for the payment to be completed (Source: Small and Medium Enterprise Agency). In this way, the commercial practice where maintenance costs are not included in the “price” of the mold and only the initial cost is focused on, consequently makes proper maintenance difficult and, in turn, drives up the total cost (life cycle cost).

So, are there no options? No, there are three points where the ordering party (procurement manager) can also be actively involved to maximize mold life and optimize total costs.

Many troubles are “built in” at the mold design stage. For example, if there are sharp edges in the product design, stress will concentrate on that part of the mold, dramatically increasing the risk of “gross cracks.” Procurement managers collaborating with the design department to promote “mold-friendly design” (for example, providing R (fillets/rounds) as much as possible) is directly linked to improving mold life.

The selection of mold material is also important. It is necessary to select a material with a balance of cost and performance according to the product’s shape and required shot count, such as materials with high high-temperature strength or high toughness (ductility).

The “operational know-how” of the supplier who manufactures the mold is also a point to be strictly checked. For example, “minimal application technology” that keeps the release agent to the necessary minimum and the proper design and management of cooling channels inside the mold are extremely effective in slowing the progression of heat checking. Whether they digitally manage casting conditions (injection speed, pressure, mold temperature) and constantly optimize them is also an indicator for identifying a reliable supplier.

Currently, one of the most effective measures to extend mold life is “surface treatment.” In particular, nitriding (chikka) treatment is a technology that forms a hard nitride layer on the mold surface. This layer has low reactivity (wettability) with molten aluminum, so it dramatically suppresses “erosion” and “seizure.” Furthermore, because it imparts “compressive residual stress” (a force that tries to shrink in advance) to the surface, it has the effect of offsetting the “tensile stress” (the cause of heat checking) during casting and delaying the occurrence of cracks.

In addition to this, various surface modification technologies such as PVD coating and CVD coating exist, and advanced know-how is required to use them properly according to the type of trouble.

Faced with the reality of an aging domestic supplier base, the risk of business closures, and soaring costs, many Japanese companies are turning to overseas, especially Southeast Asia, as a source for molds and aluminum cast products. Among them, Vietnam is one of the most noteworthy production bases today.

In the past, procurement from Vietnam might have had an image of “cheap but poor quality.” However, that is in the past. Currently, in Vietnam (especially for Japanese-affiliated companies like ours that have expanded there), a system is being put in place to simultaneously achieve high quality, low cost, and stable delivery for the following reasons:

“Wear, deformation, and breakage” of aluminum molds are not just technical problems on-site; they are issues directly linked to cost, quality, delivery, and business strategy itself. As the domestic mold industry undergoes a structural transformation, continuing to rely on conventional suppliers itself becomes a risk. Deeply understanding the mechanisms of troubles (such as heat checking, erosion), taking measures that delve into everything from the design stage to the supplier’s operation, and at the same time, collaborating with excellent overseas partners, including Vietnam, to rebuild the supply chain. This is the procurement strategy for winning in the global competition ahead. Why not take the first step now to fundamentally solve your company’s mold troubles and drastically review your cost structure?