“Precision casting” is often used as a marketing phrase, so it is worth being concrete. In practice it means a casting process that holds tight dimensional tolerance and a fine surface without relying on machining afterwards — typically ISO 8062 CT4–CT6, linear tolerance around ±0.1 mm on a 25 mm feature, and surface roughness Ra 1.6–6.3 µm. Two processes deliver that in our plant: investment (lost wax) casting and shell mould casting.
Dimensional tolerance: ISO 8062 CT4–CT6 for investment casting, CT6–CT8 for shell mould.
Minimum wall thickness: 1.5–2 mm for investment casting, 3–4 mm for shell mould, depending on section length.
Surface roughness: Ra 1.6–3.2 µm as cast for investment, Ra 6.3–12.5 µm for shell mould.
Draft angle: 0–1° for investment (a split wax die can often avoid draft), 1–2° for shell mould.
Typical part weight: a few grams to about 20 kg for investment, 0.5–100 kg for shell mould.
Investment casting builds the mould around the part. A wax pattern is injected, assembled onto a tree, dipped in ceramic slurry and stucco several times until the shell is thick enough, then dewaxed and fired. Molten metal replaces the wax, and breaking the shell releases a part that already carries fine detail and thin sections. It suits stainless and carbon steel parts where machining would cost more than the casting.
Shell mould casting (precoated sand) is the iron foundry answer to the same demand. A resin-coated sand shell is blown over a heated metal pattern, cured, and stripped as a rigid half-mould. The result is a smoother surface and better dimensional control than green sand, at a lower tooling cost than investment casting — which is why it is the usual route for ductile iron valve bodies, pump housings and brackets. More detail sits in lost wax casting: process, tolerances and cost and resin sand casting.
The economics turn on how much machining is removed. A part with a complex internal passage, a thin wall and several machined faces can lose 30–50% of its cost when it is redesigned as a precision casting, because the operations that used to remove material disappear. Below a few hundred pieces the tooling rarely pays back; between 500 and 50,000 pieces a year it usually does. Above that volume, die casting or a dedicated automation line becomes the better answer — the trade-off is set out in investment casting vs die casting.
A precision claim is only as good as the measurement behind it. First-off parts go to a CMM for full dimensional report against the drawing; in-process checks use go/no-go gauges and callipers at a fixed frequency; material is verified by spectrometer on every heat, with tensile and hardness results from the same heat’s test bar. Where a face still needs finishing, it goes to our CNC machining section, so the casting and the machined feature are held to one datum rather than two.
Five items decide the price, and a quotation without them is a guess: a drawing with the critical dimensions and any GD&T callouts marked, the alloy grade and its standard, the annual quantity and release size, the faces that must be machined after casting, and the inspection or certification level required. Send those five and a foundry can come back with a process route — investment or shell mould, pattern count, machining allowance — instead of a number pulled from a price list. Where the drawing is still open, we will quote both routes so the cost of the extra precision is visible.
Send your casting requirement — material grade (EN-GJS-500-7 / ASTM A536 65-45-12), drawing, annual volume and target price — through our RFQ form. A foundry engineer replies within one business day with a quotation, material certificate draft and production lead time.
Professional technical research and development team to provide customers with the best solution.
Jimo District, Qingdao City, Shandong Province, China
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