Sand Castings — Complex Geometry, Scalable Tooling, and Foundry Discipline You Can Count On
Simulation-led rigging, engineered sand systems, controlled melts, heat treatment, and machining—so your castings solidify cleanly, machine predictably, and pass inspection the first time.
🧭 Why Sand Casting (and When It’s the Right Hammer)
Sand casting is the most flexible route to complex metal shapes across sizes from palm-sized housings to multi-hundred-pound structures. With engineered sand systems, gating/risering science, and post-cast machining, you can achieve excellent cost per shape without surrendering dimensional control. At SanCo, we place sand casting with foundries that run process discipline first—so your castings solidify cleanly, machine predictably, and pass inspection on the first run.
- Choose sand casting when: you need organic 3D surfaces, internal cavities via cores, and tooling that tolerates design changes; volumes from tens → mid-thousands/year; broad alloy access; machining only where it pays back.
- Consider alternatives when: very thin walls or cosmetic faces at rate → die casting / permanent mold; micro features or fine as-cast holds → investment casting; low count weldments do the job → fabrication + machining; porosity must be near-zero as-cast → consider investment casting or machining from solid.
We’ll show the crossover math—tooling + piece price + machining + finishing—so you buy the right process for cost, volume, mechanicals, and schedule.
🧰 What We Deliver (End-to-End)
- DFM & Solidification Planning: pattern shrink, draft, fillets, wall transitions, cored features; simulation-driven gating/risers, chills, feeders to control porosity/shrink.
- Tooling: CNC patterns, coreboxes (cold-box, shell, no-bake), matchplates, rigging hardware—designed for maintainability.
- Molding: green sand for rate, no-bake for large/complex, shell/sodium silicate when geometry demands.
- Melting & Pour: controlled chemistry and temperature; inclusion control; documented degassing/slag practice.
- Heat Treatment: T5/T6 for aluminum; normalize/anneal/Q&T for iron/steel; age harden certain bronzes.
- Post-Cast Ops: burn-off/shot-blast, gate/runner removal, heat-straightening as required.
- Machining: turn/mill/drill/ream on stable datums; leak testing, thread gaging, functional checks.
- Finishing & Protection: powder/paint/anodize (Al), zinc/nickel plate, passivation (SS), phosphate/oil (ferrous); corrosion protection for pack/ship.
- QA & Docs: chemical certs, mechanicals, X-ray/UT when required, dimensional layouts, PPAP/FAI on request.
🧾 Materials & Typical Applications
Aluminum: A356, 319, 535, 713, sand-cast 6061 variants → housings, pumps, manifolds, structural castings (T6 for strength/machinability).
Gray & Ductile Iron: Class 20–60, 65-45-12 / 80-55-06 / 100-70-03 → machine bases, housings, brackets with damping/toughness.
Carbon & Low Alloy Steel: levers, yokes, hubs with wear/toughness via HT.
Stainless: CF8/CF8M/CF3M, 17-4PH castable → corrosion service valve bodies, food/chemical housings.
Copper Alloys: C836/C954/C955, brass/bronze → bearing housings, fluid fittings, wear components.
We lock melt practice, incoming chemistry, and heat treat early—and state the spec level (ASTM/ASME/SAE) and test bars we’re quoting.
🧠 DFM for Sand Castings — Where Money Is Won or Lost
- Draft & Fillets: 1–3° draft typical; fillets ≥ 1–2× wall to ease fill and cut stress.
- Wall Uniformity & Transitions: keep walls uniform; step or taper changes; avoid knife edges.
- Radii at Junctions: enlarge T/L junction radii to mitigate hot spots and shrink porosity.
- Core Strategy: use cores where they reduce machining; avoid fragile, deep-set cores if a straight bore is cheaper to machine.
- Machining Allowance: stock per alloy/size (e.g., 0.06–0.12″ on datum faces/bores on medium castings).
- Datum Planning: define as-cast datums that survive shakeout and HT; ensure stable fixturing surfaces.
- Leak Paths & Pressure: identify pressure faces; place chills/gates appropriately; plan impregnation if risk is non-zero.
- Surface Class: specify as-cast surface (~250–500 µin Ra typical) and which faces are cosmetic vs machined.
- Tolerances: use CT-class cast tolerances sensibly; push tight holds to machined features.
Bring your model and CTQs; we’ll return a rigging plan + simulation notes + machining datums before any chips or sand fly.
📏 Capability Snapshot (Directional)
| Area | Directional Capability |
|---|---|
| Size range | Palm size to ~400+ lb per casting (cell/flask dependent) |
| Wall thickness | Al: ~0.18–0.35″ typical; heavier for iron/steel (thinner possible with tradeoffs) |
| As-cast tolerance | CT8–CT10 typical; CTQs tightened by machining |
| Surface finish | ~250–500 µin Ra as-cast; finer with shell; cosmetic faces ground/machined |
| Mechanicals | As-cast vs HT per alloy; verified on separate bars or integral coupons |
If you need bearing seats, seal lands, or O-ring grooves, we schedule the machining. Full stop.
🧪 Quality, Documentation & Lead Times
- Quality chain: ISO 9001; melt records; spectrometer chemistry; sand control (AFS properties, LOI, moisture); travelers; dimensional layouts; capability on machined CTQs; gage R&R as needed.
- NDE: radiography, UT, MPI/LPI to your class; pressure/leak tests; hardness and tensile per heat/lot.
- Lead times: quotes 1–3 business days; tooling 2–5 weeks; sample castings typically 2–3 weeks after tooling prove-out; production matched to your releases.
- Packaging: corrosion inhibitors, caps, crate/foam, and barcode/labels to your receiving plan.
Need bridge parts? We can machine from billet or use temporary tooling while production tools ramp.
💵 Cost Model — What Moves the Needle
- Tooling complexity: pattern/corebox count, loose pieces, and rigging complexity drive NRE.
- Yield & melt loss: gating/risering and alloy density affect poured vs net weight.
- Scrap risk: porosity/inclusions mitigated via simulation and process control—cheap insurance vs rework.
- Machining minutes: datum strategy, stock allowances, and fixture access dominate piece price after casting.
- Heat treat & NDE scope: T6/Q&T recipes, loads per furnace, and X-ray/UT levels add time/cost.
- Lot size: larger pours amortize setup and stabilize price; kanban releases keep flow predictable.
We’ll present a clean break-even vs investment and die casting, including machining and finishing—not just foundry price.
⚠️ Common Pitfalls (and Our Fix)
| Pitfall | Impact | Our Fix |
|---|---|---|
| Thin walls / knife edges | Misrun, cold shuts, broken edges | Thicken or taper; adjust gating; shell molds where justified |
| Abrupt section changes | Hot spots → shrink porosity | Fillet/ramp transitions; chills/risers via simulation |
| Over-tight as-cast tolerances | Cost/lead blow-up | Shift CTQs to machined surfaces; realistic CT class |
| Deep, fragile cores | Core breakage, scrap | Split cores; mechanical supports; redesign to machine |
| Vague machining datums | Stack-up, rework | Define as-cast datums; fixture strategy pre-quote |
| Unplanned pressure sealing | Leaks/rejects | Chills, impregnation plan, pressure testing, surface class |
🏭 Typical Use Cases & Part Families
- Pump & Valve Bodies: cored passages; pressure faces; T6 aluminum or stainless/ductile iron with machined sealing lands.
- Gearbox & Motor Housings: aluminum/iron; machined bearing seats and dowel datums; powder-coated cosmetics.
- Manifolds & Elbows: complex internal geometry with leak-tested passages.
- Structural Brackets & Arms: steel/ductile iron with generous fillets; post-cast machining on pins/bores.
- Machine Bases & Guards: gray iron for damping or aluminum for weight; cosmetic faces designated.
📋 RFQ Checklist — What to Send
- 3D model + prints with CTQs/GD&T; as-cast vs machined features; cosmetic faces identified.
- Alloy & properties (hardness, tensile/yield, pressure rating) and expected heat treat.
- Volumes & cadence, size/weight targets, and SOP date with gates (EVT/DVT/PVT, FAI/PPAP).
- NDE/pressure test scope (X-ray level, UT coverage, leak spec) and acceptance criteria.
- Finish spec (powder/anodize/plate/paint), masking, conductivity/ground points.
- Packaging/label needs; any impregnation or corrosion protection requirements.
We’ll return a DFM + rigging simulation snapshot, tooling plan, heat treat, machining router, and a calendar you can book.
Related Services: Investment Castings, Die Castings, Precision Metal Fab, Machining
❓ Sand Castings FAQs
What tolerances can I expect as-cast?
CT8–CT10 is typical in sand; we machine critical features to drawing. For tighter as-cast holds, we may use shell molds or switch to investment casting.
How do you control porosity?
Simulation-led gating/risers, chills, filtered gates, melt practice (degassing/inclusion control), and targeted impregnation for pressure parts when required.
Can sand castings be pressure tight without impregnation?
Often—if geometry allows ideal feeding and short leak paths—but we’ll call out risk and a test plan. Impregnation is a proven backstop for critical programs.
How do cosmetic requirements fit with sand?
Set realistic as-cast expectations; we machine and finish cosmetic faces. Powder/paint and post-grind produce saleable surfaces.
What’s the fastest path to first articles?
Quick-turn tooling and no-bake cores with machining on essential features only. We parallel path simulation and fixture design to collapse the calendar.
Do you support PPAP/FAI and APQP?
Yes—ISO QMS with FAI/PPAP where required, control plans, capability on CTQs, and gage R&R on critical gaging.
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