GW ran its own iron foundries for decades, which is a useful background when your job is to decide which iron foundries deserve a customer's work. Foundries do not differ much in what they say. They differ enormously in what they do on a Tuesday afternoon when the melt chemistry drifts. Here is what separates the ones we use.
Control of the melt
Iron is unforgiving of sloppy chemistry. Carbon equivalent, silicon, manganese, sulphur, and the magnesium treatment for ductile grades all have to land in a window on every heat. A good foundry checks chemistry at the furnace, not after the fact, and keeps the records. When we audit, we ask to see the last month of spectrometer results for a grade like ours, and we look at how often they had to correct.
Discipline in the sand
Most iron casting defects start in the mould: sand that is too wet, too dry, poorly compacted, or contaminated with old binder. The foundries we keep test their sand every shift and can show us the log. Their patterns and core boxes are stored, inspected, and repaired before every run — including the customer-owned tooling GW places with them.
Honesty about capacity
Every foundry says it can take the work. The good ones tell you when they cannot. A realistic schedule is worth more than an optimistic one, and a foundry that pushes back on a date is usually a foundry that will hit the date it agrees to.
Inspection before shipment
Dimensional checks against the print, test bars for mechanical properties, visual and, where the part warrants it, non-destructive testing — done at the foundry, documented, and available before the parts leave. Finding a defect on your receiving dock is the expensive way to find it.
How GW qualifies a foundry
Before a foundry joins the network it is evaluated on quality systems, manufacturing capability, technical expertise, delivery performance, reliability, and continuous improvement. Joining is the beginning. Staying in requires meeting GW's standard on every order — production oversight while parts are being made, verification before they ship, ongoing performance monitoring, and corrective action when required.
Foundries treat us as peers rather than paperwork because we have stood where they stand. The benefit of that relationship — fair pricing, honest capacity, priority when it matters — lands on your order.