Investment casting compared with other manufacturing processes

Comparison matrix

Qualitative orientation only, on a scale of 1 to 5 where 5 is most favourable. Ratings summarise general industry experience; individual suppliers, alloys and part sizes can deviate substantially.

Reading the matrix

The matrix compares typical industrial practice. It does not rank the processes overall, because the factors have different weight for every part. A part of simple shape in a large series will weight tooling cost and material utilisation very differently from a complex prototype.

Process by process

• Sand casting has the widest size range and low pattern cost, with coarser tolerances and surface. It is the natural choice for large, heavy parts.
• Shell mould casting uses resin-bonded sand shells against heated metal patterns. Accuracy and surface lie between sand and investment casting; it suits medium series of moderately complex iron and steel parts.
• Gravity die casting and high-pressure die casting use permanent steel moulds and are limited to lower-melting alloys such as aluminium, zinc and magnesium. Pressure die casting is unrivalled for thin-walled parts in very large series but requires high tooling investment and limits undercuts.
• Centrifugal casting produces dense rings, bushes and tubes; shapes are essentially rotational.
• Lost foam casting allows complex shapes without cores, mainly in iron and aluminium, with a surface and accuracy below investment casting.
• Forging gives wrought structure and high fatigue strength. Shapes are simpler, draft and flash are required, and substantial machining usually follows.
• CNC machining from solid needs no tooling and gives the highest accuracy; material waste and cycle time rise steeply with complexity and with difficult alloys.
• Metal injection moulding makes very small, complex parts in very large numbers; part mass and section thickness are limited and tooling is expensive.
• Sheet metal fabrication and welded fabrication are flexible for low quantities and large structures; accuracy depends on fixturing, and welds introduce distortion and inspection effort.
• Additive manufacturing offers the greatest freedom of shape without tooling, at high cost per part and with surface and property considerations of its own. It also complements investment casting by providing printed patterns.

Total cost view

A meaningful comparison follows the part to its finished state:

1. tooling and its amortisation over the expected quantity;
2. the blank (casting, forging, bar) including material yield;
3. machining time and tooling, which depend on how close the blank is to final shape;
4. heat treatment, surface treatment and testing;
5. assembly or welding operations that a one-piece design would avoid;
6. quality risk and logistics.

Investment casting typically wins when steps 3 and 5 dominate the cost of the alternatives.

Combining processes

Processes are often combined: an investment casting with machined functional faces, a casting welded into a fabricated structure, or printed patterns for the first batch followed by a wax die for series production. Through Modulus Metal, alternatives such as sand casting, die casting and machining from solid can be evaluated for the same component; see capabilities.