Outsource metal casting with the right process and supplier
Metal casting is not one process. The correct route depends on alloy, annual volume, part size, wall thickness, complexity, tolerances and surface requirements. TOS Outsourcing helps you choose between sand casting, gravity die casting, high-pressure die casting and investment casting, then selects a qualified manufacturer from our international network.
Send us your 3D model, 2D drawing, material requirements and expected quantities. We review manufacturability, tooling concept, casting allowances, datums, critical dimensions and any risk of porosity, distortion or leakage. When functional surfaces require tighter control, we integrate CNC machining, finishing and inspection into one supply route.
You work with one Dutch technical point of contact while we coordinate tooling, samples, serial production, quality control, documentation and logistics. Share your casting project for process advice and a quotation.
Why choose TOS Outsourcing?
Significant cost savings
A broad supplier network
European quality standards
One Dutch point of contact
Expertise in labour-intensive manufacturing
Casting process overview: when to use each method
Every casting method has a practical sweet spot. Selecting the process first on part price can create expensive problems later, so we compare tooling, quality capability, machining allowance and total programme cost.
Sand casting
Sand casting is flexible for larger parts, complex shapes and low-to-medium volumes. Tooling is relatively economical, but surface finish and dimensional repeatability are generally less precise than permanent-mould routes.
Gravity die casting
Gravity die casting uses a reusable metal mould and is often selected for aluminium parts in recurring medium series. It offers better repeatability and surface finish than sand casting, with tooling investment below typical high-pressure die casting.
High-pressure die casting
High-pressure die casting is suited to high volumes, thin walls and fast cycle times, particularly in aluminium and zinc alloys. Tooling costs are higher, so stable geometry and forecast volume are important.
Investment casting
Investment casting, or lost-wax casting, can produce detailed, complex parts with a good surface finish in steel, stainless steel and other alloys. It is valuable when geometry would otherwise require extensive machining.
TOS assesses the complete part, not just the casting. We include machining, surface treatment, testing, packaging and logistics in the recommended route.
From concept to serial castings
Initial consultation
We discuss your drawing, material, quantities, critical dimensions and delivery requirements, and identify the main technical risks.
Method and supplier selection
We compare suitable casting routes and manufacturers on capability, tooling, unit cost, quality and lead time.
Quotation and approval
You receive a clear quotation covering tooling, samples, serial parts, machining, finishing, inspection and logistics.
Samples and approval
We arrange tooling and samples or a pilot batch, followed by dimensional and visual approval before serial production.
Quality control and delivery
We coordinate production, inspection, documentation, packaging and delivery to your agreed location.
From raw casting to assembly-ready component
Industrial castings often require more than a foundry operation. Fits, sealing faces, bearing seats, threaded holes and accurately positioned interfaces may need CNC machining. We define machining datums and allowances during the casting review so that tooling, workholding and inspection follow the same functional logic.
TOS can coordinate drilling, tapping, milling, turning, deburring, blasting, polishing, heat treatment, passivation, powder coating and electrolytic zinc plating. Combining these operations under one technical scope reduces transfers between suppliers and makes responsibilities clearer.
Quality requirements are agreed before tooling. Depending on the application, this can include material certificates, dimensional reports, visual acceptance samples, first article inspection, leakage or pressure tests and batch traceability. Our supply chain service then covers packaging, consolidation, transport, customs and delivery.
The result is a controlled route from casting concept to a finished part that is ready for your assembly line.
FAQ – Outsourcing metal casting
When is outsourcing metal casting the right choice?
Outsourcing is attractive when a part has ribs, curves, cavities or other geometry that would waste significant material if machined from solid. It can also reduce unit cost for repeat volumes. The business case depends on tooling investment, annual demand, material, secondary machining, quality requirements and expected product life.
Which casting process suits my part: sand, gravity die, high-pressure die or investment casting?
The choice depends on volume, alloy, part size, wall thickness, detail, tolerances and surface finish. Sand casting suits larger parts and lower tooling budgets; gravity die casting offers repeatability for medium series; high-pressure die casting suits high volumes and thin walls; investment casting is strong for complex, detailed shapes.
Which metals and alloys can be cast?
We source castings in aluminium, carbon and alloy steel, stainless steel and, where appropriate, zinc and copper alloys. Alloy selection is based on strength, temperature, corrosion, weldability, machinability, weight and applicable standards. Material certificates and traceability can be included.
What tolerances can I expect and when is CNC machining required?
As-cast tolerances depend heavily on the process, alloy, size and geometry. Non-critical surfaces can often remain as cast, while fits, sealing faces, flatness requirements and accurately positioned holes usually need CNC machining. We define machining allowances, datums and inspection points before tooling is released.
Which factors determine the price of custom castings?
Total cost normally consists of patterns or dies, sampling, unit price, machining, finishing, inspection, packaging and transport. High-pressure die casting has higher tooling cost but can deliver a low unit price at volume. Sand and investment casting may be more economical for lower volumes or complex geometries. We compare total landed cost over the expected programme volume.
What is the minimum order quantity for metal castings?
MOQ varies by process, alloy, part weight and supplier. Sand casting and some investment-casting routes can support small series, while high-pressure die casting normally requires higher volumes to justify the die. Share prototype, order and annual quantities so we can select the right route.
What does the process from drawing to serial delivery look like?
The typical route is: drawing and STEP review, process and alloy advice, supplier selection and quotation, tooling design, samples or pilot batch, approval, serial production, inspection and delivery. TOS remains your technical and commercial point of contact throughout the project.
What information is needed for a quotation?
Please provide a STEP model and 2D drawing, preferred alloy or performance requirements, quantities, annual forecast and target delivery date. Mark critical dimensions and specify porosity, leakage, surface finish, certificates, testing, machining, coating and packaging requirements. This avoids assumptions and produces a more reliable quotation.
How is the quality of cast parts assured?
We define critical-to-quality characteristics and the inspection method before production. Depending on the risk, controls can include incoming material verification, process checks, dimensional reports, first article inspection, visual acceptance standards, leakage or pressure testing and batch traceability. See our quality control service.
Which secondary operations and surface treatments can be included?
Castings can be delivered with drilling, tapping, milling, turning, deburring, blasting, polishing, heat treatment, passivation, powder coating or electrolytic zinc plating. TOS coordinates these steps so the final part arrives ready for assembly.
Can TOS support DFM and cost optimisation?
Yes. Early design-for-manufacture review often reduces cost through more consistent wall thickness, suitable draft angles and radii, better parting and core strategy, realistic tolerances and efficient machining datums. Proposed changes are documented and submitted for your approval before tooling.
What are common mistakes when sourcing cast parts?
Common mistakes include treating every dimension as critical, choosing a process before confirming volume and alloy, leaving machining and inspection planning until after tooling, and comparing only the casting unit price. A complete RFQ and early technical review prevent costly tooling changes and quality disputes.