Silica Sol Investment Casting
Near-net-shape precision - complex geometry, superior finish, minimal machining.
Silica sol investment casting (lost-wax) produces near-net-shape metal parts with intricate detail and excellent surface finish across a wide range of alloys.
Overview
Investment casting (silica-sol precision casting) uses the lost-wax process to produce near-net-shape castings: wax patterns are assembled into a tree, the ceramic shell is built, the wax is removed and metal is poured to form the part. It can produce internal cavities, deep holes and complex curved surfaces, with a smoother surface and better dimensional accuracy than sand casting. It is economical even at low volumes and is an ideal alternative for parts that are difficult to produce by CNC machining or forging.
How the Process Works
Die and wax pattern making - a master pattern is made for the part and wax is injected to produce the wax pattern (one pattern per part; pattern accuracy determines casting accuracy);
Tree assembly - multiple wax patterns are welded onto a sprue rod to form a "wax tree", allowing several parts to be poured at once (the photo shows wax trees / shells on the rack);
Shell building - the wax tree is repeatedly dipped in silica-sol slurry and stuccoed with sand to build up a multi-layer refractory shell - the number and evenness of the layers determine casting surface quality;
Dewaxing and firing - steam or high-temperature dewaxing (the wax is recovered and reused) and high-temperature firing of the shell to strengthen it;
Pouring - molten metal is poured into the hollow shell and solidifies to form the casting;
Knockout and finishing - the shell is broken away, castings are removed, gates are cut off and surfaces ground; parts are inspected and delivered.
Key Advantages
- Internal cavities, deep holes and complex curved surfaces can all be cast - almost no shape restrictions
- Superior surface finish - the fine silica-sol shell produces high-quality casting surfaces
- Near-net shape - castings are close to final form, greatly reducing machining
- High dimensional accuracy - wax patterns plus precision shells give tolerances better than sand casting
- Wide material range - carbon steel, alloy steel, stainless steel, aluminium, copper and more can be poured
- Low-cost pattern reproduction - no expensive forging or die-casting dies required
- Complex parts that are difficult to machine or forge can be cast in a single operation
Materials We Process
Stainless steel and carbon steel
Alloy steel and tool steel
Aluminum and aluminum alloys
Copper alloys and other non-ferrous metals
Typical Applications
- Pump, valve and fluid-handling components
- Hardware, locks and precision fittings
- Automotive and machinery parts
- Medical and surgical instrument components
- Precision instrument and aerospace-related fittings
- Complex brackets, housings and linkage parts
Capability at a Glance
|
Parameter |
Details |
|
Typical surface finish |
Ra 1.6–3.2 µm, part- and alloy-dependent |
|
Typical dimensional tolerance |
±0.1–0.5% of nominal dimension, part-dependent |
|
Typical minimum wall thickness |
1.5–2 mm, geometry-dependent |
|
Part weight |
From small grams to tens of kilograms |
|
Alloys |
Steels, stainless steels, aluminum and copper alloys |
|
Post-processing |
Heat treatment, machining, surface treatment available |
Frequently Asked Questions
Q: What is the surface finish like?
A: Superior surface finish, close to final surface requirements.
Q: What accuracy can you achieve?
A: Investment casting offers better tolerances than sand casting, with good dimensional consistency.
Q: What materials can you cast?
A: Common castable materials: carbon steel, alloy steel, stainless steel, aluminium, copper, etc.
Q: Are there size limitations?
A: Limited by pattern making and shell capability; generally suited to small and medium precision parts
Q: Do castings still need machining?
A: Near-net shape greatly reduces machining; critical mating surfaces and threads still require finishing to drawing.
Work With Us
Send your casting drawings and alloy requirements for a free process review. Our engineers will confirm achievable tolerances, finish and the most economical tooling strategy for your part.