Casting and machining guides for engineers and buyers

Casting is the better route when the part has complex geometry, internal features or a shape that would waste a large amount of material if cut from bar stock. Machining from solid suits simple prismatic parts, parts with tight tolerances across the whole surface, and very low quantities where tooling cannot be justified. Many parts are a hybrid: cast close to net shape, then machine only the functional faces.

304 is the general-purpose austenitic grade and the least expensive of the three; it is fine for fresh water and mild atmospheres but can suffer chloride pitting. 316 adds molybdenum and is the usual choice for marine hardware, chemical service and coastal locations. 316L is the low-carbon version of 316: it keeps the corrosion resistance through welding instead of forming chromium carbides at the weld line, so it is the grade we quote for welded and hygienic assemblies. Choose the lowest grade that meets your corrosion and strength requirement.

ISO 8062-3 assigns a cast tolerance grade from CT1 (finest) to CT16 (coarsest). Each grade defines a total tolerance band that grows with the nominal dimension. Our investment casting process holds ±0.1 mm by process, so a 100 mm dimension is quoted inside that band unless your drawing calls for something tighter or looser; a sand casting on the same dimension typically allows several times that. Put the grade you need on the drawing, and state the machining standard for finished surfaces (for example ISO 2768-m) so the foundry and the machinist work to the same numbers.

Sampling takes 10 days from order, for both investment casting and lost foam. That window covers drawing review, wax die manufacture and the first sample casting with its dimensional report. Where a part needs a more complex die we tell you before you commit, rather than letting the date slip.

Production runs 25 days at MOQ 500 pcs, counted from sample approval and receipt of deposit, and that figure already includes casting, machining, heat treatment, finishing and inspection where the drawing calls for them. Repeat orders against existing tooling skip tooling and sampling entirely and go straight into that 25-day window.

Yes, for most parts. We can compress the schedule by adding shifts on wax injection and shell building and by prioritising your heat in the melt shop. A rush surcharge applies and the achievable date depends on current load, so raise it early — expediting is far easier before the tooling is cut than after.

Samples are not free. The first castings carry the tooling cost plus a sample charge, both confirmed in the quotation before anything is made. We do not begin series production until you approve the sample in writing, so you never pay for volume you have not accepted.

Series production starts at 500 pcs per part number, and trial or prototype batches below that are quoted as tooling trials. If you need a small trial order before committing to a forecast, say so in the RFQ. Running a small batch to prove the part is better than ordering volume against an unproven design.

Wax dies and machining fixtures are quoted as a separate line item. Once paid for, the tooling is your property. We hold and maintain it for your repeat orders, or release and ship it to you or to another supplier on written request. State your tooling ownership requirement in the RFQ so it is recorded from the start.

Yes. We sign non-disclosure agreements and return them before you release drawings. If you prefer, send a watermarked 2D drawing for the initial quotation and release the full 3D model only after the NDA is in place.

The documentation set is agreed at order stage: a material certificate traceable to the heat number, a dimensional report and the first article inspection report are the usual set. Where your drawing calls for it, we arrange radiographic, ultrasonic, magnetic particle or dye penetrant testing and issue the report against your order reference. Third-party inspectors such as SGS, BV or TÜV, or your nominated agent, are welcome on site.

Payment is by T/T, with the deposit and balance ratio agreed in the quotation. We quote EXW or FOB, and other terms can be agreed to match your logistics. Terms are reviewed after the first few orders.

We are a manufacturer, not a trading company. Casting, CNC machining, heat treatment, finishing and inspection all happen on our own site in Qingzhou, Shandong, and we retain the melt, heat-treatment and inspection records for the parts we ship. We are happy to arrange a video walkthrough or a factory visit before your first order.