Die casting and investment casting are two common metal casting processes used in manufacturing. Both have their own advantages and disadvantages in terms of cost, quality, design flexibility and suitable applications. This article analyzes and compares them in detail.
The key differences lie in that die casting is faster and cheaper but less design flexibility, while investment casting is slower and more expensive but better for complex geometries. Die casting produces good dimensional accuracy and surface finish for high volume production. Investment casting allows intricate shapes, thinner walls and finer details, ideal for small to medium volumes.
In applications, die casting suits parts with simple,moderate precision requirements like housings, brackets, gears, whereas investment casting is better for impellers, turbocharger wheels requiring complex internal design. The optimal choice depends on production volume, geometry,surface finish, strength needed and cost targets.
Die casting has much lower tooling/setup cost than investment casting
The die casting process uses reusable steel tooling – die blocks – to form mold cavities for molten metal to be injected under high pressures. The steel tooling leads to very high upfront costs ranging from $5000 to even $100k depending on part size and complexity.
In contrast, investment casting uses disposable wax patterns embedded into ceramic slurry to create mold cavities. The wax and ceramic mold only costs a few thousand dollars even for intricate parts. No expensive steel tooling is needed, making investment casting more economical than die casting for low volume production.
However, when production volume ramps up, the high upfront tooling cost gets amortized over more parts produced by die casting. Per piece cost drops rapidly for die casting due to fast cycle times of 15-90 seconds. Investment casting with its longer process remains higher cost per piece due to manual labor steps. Therefore die casting becomes preferred choice for mass production volumes above 10,000-20,000 pieces.
Investment casting allows finer details and thinner walls vs die casting
The injection pressure and rapid cooling in die casting places design limitations – minimum wall thickness of 2-4mm is needed for most alloys. Rapid cooling can also create internal voids and porosity in the casting.
Investment casting can produce very intricate geometries, thin walls down to 0.5mm, complex inner contours and precise dimensions unattainable by die casting. This gives more design freedom. Stereo lithography allows any 3D part geometry to be transformed easily into investment castings.
The slower solidification in investment casting results in less internal porosity and a more dense, higher integrity metal structure. This allows higher possible strength levels to be attained.
Die casting has higher dimensional accuracy and productivity rate
For high volume production, die casting offers faster cycle times – as low as 15-30 seconds, leading to very high productivity rates over one million pieces per year achievable on a single machine. This high production rate lowers cost per piece significantly.
Investment casting cycle times range from hours to days depending on part complexity, drying/firing, melt and cooling rate. Yearly production volumes max out at 200,000 pieces for investment casting.
The stability of steel tooling and precision die machining enables die cast parts to achieve good dimensional tolerance around 0.2% of nominal value. This allows minimal secondary machining. Investment cast surfaces have slightly lower accuracy due to inherent process variability.
Die casting generally has better mechanical properties for most alloys
The high pressure injection and faster cooling rates of die casting leads to fine-grained microstructure for most alloys like aluminum and zinc. This lends higher yield strength, tensile strength and hardness properties.
The slower solidification of investment casting results in coarser grains for similar alloys. Strength levels are hence generally lower, only 65-70% of die casting strengths for aluminum. However some superalloys like IN718 nickel alloy can match or exceed strength of die cast IN718 due to hot isostatic pressing applied.
Lower cost die casting applications vs investment casting uses
Typical applications where die casting is the optimal process choice due to its cost-effectiveness and productivity advantages:
– High volume housings, enclosures, brackets, gears or pulleys made of aluminum, zinc or magnesium
– Up to moderate precision requirements, simple external shapes without complex inner contours
– Minimal secondary machining
Investment casting applications where its flexibility and quality offsets higher price points:
– Low/medium volume batches up to 20,000 pieces per year
– Intricate shapes, thin walls and fine details
– Turbine blades, impellers, valves, turbocharger wheels
– Alloys requiring high integrity like stainless steel and superalloys
So in summary, for low cost, high volumes and simple geometries – die casting excels. For lower volumes but complex shapes demanding precision – investment casting is superior.
In metal casting processes, die casting vs investment casting presents distinct cost-quality tradeoffs. Die casting offers lower cost tooling and per piece cost for high volume runs above 20k pieces/year along with good mechanical properties and accuracy. Investment casting suits lower quantities under 20k pieces/year with flexibility for complex, high precision designs but incurs more expense.