Renyi Castings
RFQ@renyicastings.com
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Ningbo city
China 315137
Fast Response Email Support
GMT+8
China 315137
Superior surface finish and tighter tolerances through the silicon sol (silica sol) investment casting process. Specialists in stainless steel, carbon steel and alloy steel — serving global OEMs since 2005.
Lost wax casting — also known as investment casting — is a precision metal forming process in which a wax pattern is coated with ceramic shell material, the wax is melted out, and molten metal is poured into the hollow mould. The result is a near-net-shape part with exceptional surface finish and dimensional accuracy.
At Renyi Castings, we use the silicon sol (silica sol) process — the premium variant that uses a silicone-based binder with green wax and quartz sand. Compared to the older water glass process, silicon sol delivers a significantly smoother surface, finer detail reproduction, and tighter tolerances — making it the preferred choice for stainless steel and high-precision applications.
Our fully automated wax injection machine and robotic ceramic shell coating system eliminate the two biggest sources of human variance in the process — ensuring every pattern and every shell is produced to the same standard, batch after batch.
Water glass (sodium silicate) is a lower-cost binder used in simpler casting applications. Silicon sol uses colloidal silica — a finer, more stable binder that produces a denser, smoother ceramic shell. The result: surface roughness improves from Ra 6.3–12.5µm (water glass) down to Ra 1.6–3.2µm (silicon sol), with better tolerance consistency across production runs.
Austenitic stainless steels (SS304, SS316, 17-4PH) require higher pouring temperatures and are more sensitive to shell quality than carbon steel. Silicon sol’s denser shell withstands the thermal shock of high-temperature pours without cracking — preventing surface defects and metal penetration that are common failure modes with water glass moulds.
The precision of the silicon sol process means many features can be cast to final dimension without secondary machining — holes, threads, undercuts and thin walls that would otherwise require costly CNC operations. This reduces material waste, machining time, and per-part cost for moderate-to-high volume programs.
Eight controlled stages from wax pattern to finished part — all performed in-house for full quality ownership and shorter lead times.
Green wax injected into aluminium tooling by CNC automatic injection machine — consistent pattern geometry every shot
Wax patterns welded to a central sprue to form a tree cluster for batch pouring efficiency
Automated silicon sol slurry dipping — 5–7 ceramic layers applied with consistent speed and immersion time
Steam autoclave removes the wax pattern, leaving a hollow ceramic mould cavity
Ceramic mould fired at 900–1000°C to strengthen shell and eliminate residual moisture
Molten stainless steel or alloy steel poured into the pre-heated shell under controlled conditions
Ceramic shell broken away; parts cut from tree by vibration or abrasive wheel
Grinding, heat treatment, CNC machining, surface treatment and dimensional QC
Two critical automation investments that set our lost wax casting quality apart — eliminating human variance at the wax pattern and shell coating stages.
Our CNC automatic wax injection machine delivers precise, repeatable wax patterns every cycle. Controlled injection pressure, temperature and timing ensure uniform wall thickness and eliminate sink marks — the foundation of dimensional accuracy in investment casting.
Introduced in 2019, our robotic shell coating arm applies each silicon sol ceramic layer with programmed consistency — same dip angle, same immersion time, same withdrawal speed. The result: uniform shell thickness, lower defect rate, and predictable per-part cost.
Understanding which process is right for your application — a quick reference guide.
Silicon sol investment casting delivers near-net-shape accuracy. Key achievable specifications for standard production conditions.
Per 12.7mm of dimension. Tighter premium tolerances available at ±0.08mm for critical features.
Silicon sol process typical. Significantly finer than water glass (Ra 6.3–12.5µm). Many surfaces require no secondary finishing.
Standard achievable range. Walls as thin as 0.5mm have been achieved on limited surface areas, alloy-dependent.
Typical production range. Most lost wax castings fall between 50g and 10kg for optimum process efficiency.
Silicon sol lost wax castings are specified wherever tight tolerances, smooth as-cast surfaces, and corrosion resistance are required — from fluid-handling equipment to precision structural components.
What sets Renyi Castings apart — for precision buyers across Europe, North America and Southeast Asia.
Our silicon sol process consistently achieves Ra 1.6–3.2µm as-cast surface roughness — finer than water glass castings and comparable to light machining. Many surfaces require no secondary finishing.
Automated ceramic shell application eliminates the human variance that causes shell defects and blow-outs — delivering uniform thickness, lower scrap rate, and predictable cost across every batch.
CNC-controlled wax injection machine ensures every pattern is produced at identical pressure, temperature and timing — the foundation of dimensional consistency before a single drop of metal is poured.
Design consultation, tooling fabrication, casting, CNC machining, surface treatment and assembly — all handled in-house. No supplier handoffs, no coordination delays.
Every quotation is broken down by mould cost, casting cost and shipping cost. You know exactly what you’re paying for — no bundled pricing, no surprises at invoice stage.
Prototype runs from 1 piece to serial production of 50,000+ units per year. No rigid minimums — we size our capacity to your program, not the other way around.
Quality control is embedded at every stage of our lost wax casting process — not added at the end. Our in-house QC laboratory covers incoming material verification, in-process shell inspection, and outgoing dimensional checks before any order leaves the factory.
Inspection documentation — including material test reports, dimensional records, and NDT results — is available on request and provided based on your order requirements. Talk to us about what your application needs.
OES spark analysis confirms alloy grade on every heat charge before pouring. No unverified metal enters production.
Non-destructive internal inspection for porosity, shrinkage and cold shuts. Applied to critical castings as required by the customer or part specification.
First article and in-process dimensional verification against customer drawings. CMM for 3D geometry; VMS for fine features and 2D profiles.
Every casting is checked for surface defects, finish consistency, and correct marking before packing. Non-conforming parts are held and reviewed.
Send drawings (STEP / DXF / PDF) to us — response within 12 hours.