Shell mold casting, also referred to commonly as shell molding, is comparatively a new casting technique, developed in Germany in the 1940s.
It’s a type of metal casting process that involves pouring molten metal(ferrous or non-ferrous) or alloy into sand and resin which is further heated and shaped to build a mold.
Shell mold casting offers improved surface finish and higher precision compared to other metal casting methods, and suitable for small parts that require complex shapes and high dimensional accuracy.
Shell mold casting is applied to various industries such as aerospace, lékařský, a automobilový průmysl.
It is especially popular in the automotive industry and is often employed to manufacture camshafts, gearboxes, klikové hřídele, hlavy válců, bearing housings, lever arms, and valve bodies.
Two matching metal pattern halves—typically machined from steel or iron—are produced to the exact geometry of the desired casting (plus allowances for shrinkage and shell thickness).
Each pattern half is heated (≈180–250 °C), lightly sprayed with a release agent, then dipped into a “dump box” containing fine sand coated in a thermosetting resin.
The hot pattern cures a uniform shell layer (6–12 mm thick) as excess sand is shaken off.
The two cured shell halves are carefully stripped from their patterns.
If internal cavities are required, resin‐bonded sand cores are placed inside one shell half.
The cope (top) and drag (bottom) shells are then clamped together in a flask, and the gating system (sprue, běžci, vents) is attached.
Molten metal or alloy (např., železo, ocel, hliník) is heated to its liquidus temperature and poured by gravity into the sprue.
The metal fills the shell cavity, replicating fine details and thin sections.
The thin, ceramic‐like shell conducts heat away rapidly.
After an appropriate cooling interval—often just a few minutes at ambient temperature—the metal has solidified into a robust casting.
The flask is opened and the shell fragments are broken away to free the casting.
The part is then freed of any gating or core material and undergoes any required trimming, broušení, or surface finishing before inspection.
Shell molding accommodates most ferrous and non-ferrous alloys, například:
| Alloy Family | Typical Grades | Key Properties & Applications |
|---|---|---|
| Gray Iron | ASTM A48 Class 20–40 | Excellent machinability & vibration damping; used for engine blocks, pouzdra. |
| Tvárná litina | ASTM A536 60-40-18, 65-45-12 | Higher strength & toughness than gray iron; ideal for gears, klikové hřídele, ventily. |
| Uhlíková ocel | AISI 1018, 1020, 1045 | Good strength and weldability; used for shafts, závorky, konstrukční díly. |
| Legovaná ocel | 4140, 4340, H13 | Enhanced hardness, houževnatost, a odolnost proti opotřebení; used in dies, nářadí, těžké stroje. |
| Nerez | 304, 316, 17-4PH, 2205 (Duplex) | Corrosion resistance and strength; used in chemical, jídlo, lékařský, and marine parts. |
| Hliníkové slitiny | A356, A357, ADC12 | Lehký, good fluidity; used for automotive brackets, pouzdra, aerospace fittings. |
| Slitiny mědi | C905 (Cínový bronz), C836 (Hliníkový bronz), C230 (Cartridge Brass) | Excellent wear and corrosion resistance; používané v ložiskách, průchodky, námořní hardware. |
| Nickel-Based Alloys | Inconel 625, Hastelloy C276 | Outstanding high-temperature strength and corrosion resistance; used in aero-engines, chemické zpracování. |
| Slitiny hořčíku | AZ91D, AM60 | Very lightweight; used in electronics housings and automotive components. |
| Zinc Alloys | Zamak 3, Zamak 5 | Low melting point and excellent detail reproduction; used for small, složité části (hardware, kování). |
1. Proprietary Resin‐Sand Formulations
2. High-Speed, Automated Shell Production
3. Expert Pattern & Tooling Design
4. Broad Alloy Capability
5. Tight Dimensional Control
6. Lean, Green Operations
7. Comprehensive Quality Assurance
8. Dedicated Technical Support
| Průmysl | Typical Shell Mold Castings | Typical Products |
|---|---|---|
| Automobilový průmysl | Camshaft and crankshaft housings, gearbox and transmission cases, hlavy válců, bearing carriers, and linkage arms—benefit from tight tolerances and fine surface finish, reducing or eliminating post-machining. |  |
| Aerospace & Defense | Actuator brackets, fuel-system fittings, small turbine stator segments, control-surface hinges, and structural brackets—leveraging weight-sensitive, high-precision parts where repeatability and fatigue resistance are critical. |  |
| Lékařská zařízení | Surgical instrument handles and housings, implant-fixture bushings, orthopedic bracketry, and fluid-control valves—requiring complex internal passages, biocompatible alloys, and sterilizable finishes. |  |
| Industrial Valves & Pumps | Precision valve bodies, oběžná kola, volutes, and pump housings cast in stainless or duplex stainless steels—resisting corrosive media while maintaining exacting dimensional requirements for reliable sealing and flow control. |  |
| Oil & Gas / Petrochemický | Chemical-service fittings, filter housings, manifold blocks, and instrumentation flanges—taking advantage of exotic alloys (např., Inconel, Hastelloy) with minimal surface porosity and high dimensional fidelity. |  |
| Consumer & Decorative | Ornamental door handles, osvětlovací tělesa, sculpture components, and architectural accents—shell-cast in brass, bronz, or aluminum to capture fine textures and crisp edges. |  |
| Renewable Energy & Power Generation | Small hydraulic turbine nozzles, control-valve bodies, and generator accessory brackets—benefiting from rapid turnaround and the ability to cast heat-resistant alloys with tight wall-thickness control. |  |
| Same side of parting line: | ± .020 for 1st 3″ | Add ± .003 / inch over 3″ |
| Across parting line: | ± .030 for 1st 3″ | ± .003 / inch over 3″ |
| Draft: | Typically 1° | Certain applications at 0° draft. |
| Typical Finish Stock: | .060″ maximum | |
| Hole size cast into part: | DIAMETER | DEPTH |
| Less than 0.5″ | Equal to diameter | |
| 0.5″ – 1.0″ | Equal to 1.5 times diameter | |
| Greater than 1.0″ | Equal to 2 times diameter |
Shell mold casting is a precision sand-based process in which a heated metal pattern is coated with fine, resin-bonded sand to form thin “shell” halves. Once cured and assembled, these shells serve as the mold into which molten metal is poured.
Almost any alloy is suitable—including gray and ductile irons, carbon and alloy steels, nerezové oceli, slitin hliníku, copper-based alloys, and even nickel-based superalloys—thanks to the shell’s heat resistance.
Typical dimensional tolerances reach ±0.3 mm per 100 mm, and surface finishes are in the Ra 3–6 µm range. This precision often eliminates or minimizes secondary machining.
Shell molding excels at small to medium components (from a few grams up to about 50 kg). Shell halves larger than this become difficult to handle and may crack under their own weight.
Each shell half cures in roughly 10–30 seconds on automated dip-and-shake equipment. This quick turnaround supports fast prototyping and moderate production volumes.
Intricate details—thin walls (down to 1.5 mm), podříznutí, fine ribs, and internal passages—are readily achieved. Cores can be inserted for complex internal cavities.
Select shell molding when your parts require small- to medium-size, vysoká dimenzní přesnost, fine surface quality, and complex detail.
| Kritéria | Odlévání do písku | Odlévání formy skořápky | Investiční lití |
|---|---|---|---|
| Materiál formy | Green sand (oxid křemičitý + clay) | Resin-bonded fine sand shell | Keramická skořepina (wax patterns dipped in slurry) |
| Náklady na nástroje | Very low | Mírný (heated patterns + resin sand) | Vysoký (wax tooling + multiple shell dips) |
| Mold Reuse | Žádný (sand broken each pour, but sand is reclaimable) | Žádný (each shell single-use, sand reclaimable) | Žádný (each ceramic shell single-use) |
| Part Size Range | Very small to very large (> several tons) | Small to medium (up to ~50 kg) | Very small to small (obvykle < 10 kg) |
| Dimensional Tolerance | ± 0.5 mm per 100 mm | ± 0.25–0.35 mm per 100 mm | ± 0.15–0.25 mm per 100 mm |
| Povrchová úprava (Ra) | 6–12 µm | 3–6 µm | 1–2 µm |
| Tloušťka stěny | ≥ 6 mm | ≥ 1.5–2 mm | ≥ 1 mm |
| Složitost & Detail | Mírný (cores required for internal features) | Vysoký (Tenké stěny, fine features easily achieved) | Velmi vysoká (podříznutí, intricate geometries) |
| Doba cyklu | Pomalý (mold prep, Shakeout) | Rychle (shell cures in seconds) | Slowest (multiple coating and dewax steps) |
| Objem výroby | Nízká až střední | Nízká až střední | Nízká až střední (100–1,000s parts) |
| Typical Alloys | Železo, ocel, hliník, bronz, atd. | Železo, ocel, stainless, hliník, slitiny mědi | Stainless, Supermiony, bronz, hliník |
| Post-processing Needs | Often heavy machining and surface cleanup | Minimal machining; light finishing | Minimal machining; often ready to final shape |
| Best For | Velký, heavy, cost-sensitive parts | Precision small/medium parts with moderate volume | Extremely intricate, thin-walled, high-accuracy parts |
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