The Definitive Guide
Last updated June 12, 2026
|18 min read
|Reviewed by Wes Parker, President & CEO
±0.010″
Linear tolerance
A356 · 319
Primary alloys
1oz–100lb
Part size range
150 psi
Leak / pressure test
3° min
Draft angle
On this page
Custom aluminum castings are net- or near-net-shape metal parts produced by pouring molten aluminum alloy into a reusable steel mold. At ProCast, parts are made by the permanent-mold (gravity) process, which yields denser, stronger, and more dimensionally consistent components than sand casting — typically holding linear tolerances of 0.010″–0.025″ on parts from ounces to 100 pounds.
Custom castings differ from catalog or off-the-shelf parts because the tooling is engineered around your geometry, alloy, and end-use requirements. The decision to cast — rather than machine from billet or fabricate — is driven by part complexity, annual volume, weight, and the structural properties the application demands.
This guide walks through every decision in that journey: how the process works, the tolerances and alloys available, the design rules that keep tooling costs down, what drives price, and how North American permanent-mold sourcing compares to offshore die casting.
Permanent mold casting pours molten aluminum by gravity into a preheated, reusable steel (H13) die. Because the metal solidifies against a metal mold rather than sand, it cools faster and more directionally — producing a fine grain structure, superior mechanical properties, and excellent repeatability across high-volume production runs.
The permanent mold aluminum casting journey
As-cast permanent-mold parts typically hold linear tolerances of 0.010″ to 0.025″, with the tighter end achieved on smaller features and across the parting line held to roughly 0.015″. Where drawings call for tighter control, critical features are finished by in-house CNC machining to as low as 0.0005″.
Design for a preferred wall thickness of 0.180″, a minimum draft angle of 3 degrees, and uniform sections that promote directional solidification. Following these rules keeps tooling simple, reduces shrinkage defects, and lowers per-part cost. Parts run from one ounce up to 100 pounds.
0.180″
Preferred wall thickness
Uniform walls feed evenly and minimize hot-spot shrinkage. Thinner sections are possible but raise scrap risk.
3°
Minimum draft angle
Draft on all vertical walls lets the part release cleanly from the steel mold without galling or distortion.
ProCast pours 3xx.x-series aluminum casting alloys — principally A356 and 319 — with T5 and T6 heat-treatment options. These silicon-based alloys are chosen for their excellent fluidity and castability: A356-T6 is the workhorse for structural and pressure-tight parts, while 319 suits higher-temperature and wear applications. Heat treatment dials in the required strength, ductility, and dimensional stability.
ProCast is a single-source supplier: castings ship fully finished. In-house capability spans up-front solidification analysis, CNC machining, pressure and leak testing up to 150 psi, impregnation, and finishing — so a casting arrives as a validated, ready-to-assemble component rather than a raw part.
Casting simulation up front to predict shrinkage and optimize gating before tooling is cut.
Multi-axis machining of critical features to print, all under one roof.
Leak and pressure testing up to 150 psi for hydraulic and fluid-handling housings.
Seals micro-porosity for pressure-tight castings that must hold fluids or gases.
Shot blast, powder coat, anodize, and plating through qualified partners.
Inserts, fasteners, and sub-assembly so parts ship ready for the line.
Permanent-mold tooling costs roughly one-tenth that of pressure die-cast molds — typically from a few thousand to tens of thousands of dollars depending on part size and complexity. That makes it the economical choice for medium production volumes of about 500–50,000 parts per year. Per-part price is then driven by alloy weight, machining content, secondary operations, and annual quantity rather than by the casting pour itself.
Because the up-front tooling investment is a fraction of die casting, the break-even volume is far lower — programs that would never justify a die-cast mold are profitable in permanent mold. The main cost drivers:
one-time die cost spread across the program volume.
pour weight including gates, at current aluminum index.
number of finished features, testing, and finishing.
larger releases lower setup cost per piece.
North American permanent-mold casting wins on total landed cost, not just piece price. Domestic sourcing removes ocean freight, customs delay, and 8–14 week lead times, while keeping tooling, IP, and engineering support in-house — so revisions take days, not months, and there are no hidden quality or logistics surcharges.
Choosing a process is a trade-off between tooling cost, volume, and part quality. Permanent mold sits in the sweet spot between low-volume sand casting and high-volume die casting.
Proof, not marketing
Each capability on this page follows a Capability · Mechanism · Evidence · Scope formula so it can be independently verified: