Machined Investment Casting Parts

Machined investment casting parts combine lost-wax silica sol casting with multi-axis CNC secondary finishing. This dual-process integration delivers complex, near-net-shape geometries while meeting micron-level dimensional tolerances on critical fitment features.
• Silica Sol Investment Casting: Handles complex internal channels, draft-free thin walls, and near-net shapes (Ra 3.2 µm).
• Multi-Axis CNC Machining: Delivers tight tolerances (down to ±0.005 mm), precision bore geometry, threads, and high sealing face flatness (0.01 mm).

Core Specifications at a Glance

Every part passes through a controlled silica sol casting line followed by precision machining setups:
Wax Pattern Injection -> Tree Assembly -> Silica Sol Shell Building -> Multi-Layer Stucco Application -> Hydro-Demolding / Dewaxing -> High-Temp Shell Sintering (950°C–1100°C) -> Induction Furnace Melting -> Shell Knock-Out & Shot Blasting -> Post-Cast Heat Treatment -> 3/4/5-Axis CNC Machining -> NDT & Final CMM Inspection -> Packaging

Tooling & Wax Pattern Injection
Aluminum dies are CNC-machined from 7075-T6 aluminum to account for volumetric shrinkage rates (1.5% – 2.8%, depending on alloy grade). Modified paraffin/polyethylene wax is injected under temperature-controlled conditions (62°C – 65°C, pressure 2.5 – 3.5 MPa) to maintain pattern repeatability within ±0.05 mm.

Tree Assembly & Gating System Design
Wax patterns are mounted onto a central runner tree. Gating systems are configured using solidification simulation software (ProCAST) to establish directional solidification, eliminating internal shrinkage cavities in heavy section transitions.

Silica Sol Ceramic Shell Building
Patterns are dipped into liquid silica sol binder and slurried with refractory zircon powder (primary layer) and fused silica (secondary layers):
• Face Coat: Zircon flour (325 mesh) with silica sol binder for surface detail and thermal resistance.
• Backup Layers: 4 – 6 sequential layers of mullite sand, dried under ambient control (22°C ± 2°C, Humidity 55% – 65%).
• Shell Properties: High hot-yield strength, resisting thermal shock during pouring without cracking or reacting with molten metal.

Dewaxing & High-Temperature Shell Sintering
• Autoclave Dewaxing: Steam dewaxing at 160°C–175°C and 0.8 MPa pressure rapidly evacuates over 98% of pattern wax without cracking the ceramic shell.
• Shell Sintering: Ceramic shells are fired in rotary or box furnaces at 950°C – 1100°C for 45 – 90 minutes. This burns off residual organic matter, sinters ceramic particles, and preheats the mold to optimize metal fluidity during pour.

Induction Melting & Pouring
Metals are melted in medium-frequency induction furnaces (100 kg – 500 kg capacity). Spectrographic thermal samples are drawn from the liquid bath prior to tap to verify chemical composition. Direct bottom-pour or tilt-pour ladles transfer molten metal into preheated molds at target pouring temperatures (1480°C – 1620°C for stainless steels).

Knock-Out, Fettling, and Cleaning
After air cooling, ceramic shells are removed via pneumatic knock-out hammers and high-pressure water blasting. Gates and risers are cut via abrasive saws or plasma cutters, followed by pedestal grinding to flush the gate stubs.

Standard Material Matrix

Dimensional and Surface Capability
• As-Cast Surface: Ra 3.2 µm to Ra 6.3 µm
• CNC Machined Surface: Ra 0.8 µm to Ra 1.6 µm
• Ground Finish: Ra 0.2 µm to Ra 0.4 µm
• As-Cast Tolerance: ISO 8062-3 CT4 to CT6
• Machined Tolerance: ISO 2768-m (General) / Up to ±0.005 mm (Critical Bores)

Near-Net Complex Geometries: Internal fluid paths, undercut pockets, and thin wall profiles down to 1.5 mm are cast directly into the blank. Raw material wastage is reduced by 40% – 70% compared to fully machining parts from solid bar or billet stock.

Zero Draft Angle Capability: Unlike drop forging or die casting, investment casting allows zero-draft parallel walls on non-machined exterior faces, eliminating unnecessary component weight.

Integrated Machining Datums: Cast components are engineered with cast-in locating boss surfaces, enabling repeatable fixture clamping during post-cast 4-axis and 5-axis CNC machining steps.

Monolithic Assembly Redesign: Multi-part welded assemblies can be re-engineered into single-piece investment castings with localized CNC finishing on functional mating faces, eliminating joint leakage risks and welding inspection costs.

Flow Control & Valve Hardware
• Components: Dual-expansion valve bodies, tri-clamp sanitary valve housings, ball valve cores, butterfly valve discs.
• Key Requirements: Pressure containment under ASME B16.34, hydro-tested to 1.5x cold working pressure; zero pinhole leakage; profile tolerance on seal grooves within 0.02 mm.

Fluid Transfer & Pump Systems
• Components: Closed and open impellers, volute casings, diffuser rings, wear rings.
• Key Requirements: Dynamic balancing according to ISO 1940-1 Grade G2.5; smooth cast internal flow channels (Ra 3.2 µm) to prevent cavitation and fluid drag.

Automotive & Commercial Vehicles
• Components: Turbocharger wastegate actuators, exhaust manifold flanges, gear shifter forks, engine brackets.
• Key Requirements: High thermal shock fatigue strength (316L / 1.4848); tight pin-bore tolerances (H7 fit).

Food Processing & Pharmaceutical Equipment
• Components: Homogenizer blocks, grinding plates, sanitary pump impellers, filling nozzles.
• Key Requirements: Stainless steel grade 316L (CF3M) with electropolished surfaces (Ra ≤ 0.4 µm); non-porous structure complying with FDA / 3-A sanitary guidelines.

Machine Tooling & Capabilities
• Vertical & Horizontal Machining Centers (VMC/HMC): 10 processing centers (including 4-axis rotary indices and pallet changers for continuous production).
• CNC Lathes & Turning Centers: 20+ CNC turning stations achieving bore roundness within 0.005 mm.
• EDM & Hole Drilling: Wire EDM for complex spline profiles and high-precision internal keyways.

Available Secondary Operations
• Machining Scope: Turning, Facing, Boring, Thread Tapping (UNC/UNF/Metric/NPT), Milling, Broaching, Wire EDM, Precision Grinding.
• Heat Treatment Operations:
Solution Annealing: Stainless steels (1040°C – 1120°C followed by rapid water quench) to restore corrosion resistance.
Normalizing & Stress Relieving: Carbon/alloy steels to relieve internal casting stresses prior to finish machining.
Quenching & Tempering (Q&T): Carbon and low-alloy steels to achieve target Hardness (28 – 45 HRC).
Induction Hardening: Localized surface hardening on wear faces (up to 58 – 62 HRC).

Surface Finishing & Coatings:
• Passivation (ASTM A967) for stainless steel corrosion resistance.
• Electropolishing & Manual Polishing (up to mirror finish Ra 0.1 µm).
• Electro-plating (Zinc, Nickel, Chrome).
• Powder Coating & Epoxy Wet Paint.
• Shot Blasting & Tumbling for uniform matte finish.

Chemical & Physical Metallurgical Verification
• Direct-Reading Optical Emission Spectrometer (OES): Verifies chemistry per heat charge before pouring. Heat certificates (EN 10204 3.1) accompany every shipment lot.
• Metallographic Microscope: Analyzes microstructure phase ratios (e.g., ferrite content in duplex steels, nodular graphite distribution).
• Mechanical Testing: Universal tensile testing (yield strength, tensile strength, elongation), Charpy V-notch impact testing at ambient or low temperature (down to -46°C), and hardness testing (HBW, HRC, HV).

Non-Destructive Testing (NDT)
• Dye Penetrant Inspection (PT): Detects surface discontinuities (cracks, laps, surface porosity) in non-ferrous and stainless components (ASTM E1417 standard).
• Magnetic Particle Inspection (MPI / MT): Identifies sub-surface flaws in ferromagnetic alloy components (ASTM E1444 standard).
• Radiographic Testing (RT / X-Ray): Detects internal gas shrinkage and inclusions per ASTM E192 reference radiographs upon customer requirement.
• Hydrostatic Pressure Testing: Up to 10 MPa (100 bar) to confirm valve and pump housing seal integrity without wall weeping.

Dimensional Metrology
• Coordinate Measuring Machine (CMM): Volumetric CMM inspection verifying GD&T characteristics (True Position, Concentricity, Flatness, Runout) against 3D CAD models step files.
• Surface Roughness Testers: Digital contact stylus meters to document Ra, Rz, and Rt values on machined faces.

Workflow Overview
Engineering File Transfer (STEP/IGES/DWG) -> DFM & Casting Simulation -> Tooling Design & Sample Build -> First Article Inspection (FAI) + PPAP Level 3 -> Customer Approval -> Serial Batch Production & Continuous Machining

Tooling Ownership & Engineering Support
• Tooling Ownership: Tooling/molds built for customer projects remain 100% the customer's property. Molds are maintained, insured, and stored in climate-controlled racks at zero maintenance fee for the active program lifetime.
• Design for Manufacturability (DFM): Engineering teams review customer prints prior to mold production to suggest draft optimization, wall thickness equalization, fillet radius increases, and locating datum placement to lower overall piece-part unit cost.
• Sampling & PPAP Protocols: First Article Inspection Reports (FAIR) alongside 3D CMM data charts are supplied with initial approval samples. PPAP Level 3 documentation (including Process Flow Diagrams, PFMEA, Control Plans, and Dimensional Results) is provided for automotive and industrial program approvals.

Checklist for Sourcing Procurement Engineers
• 2D & 3D Vector Files:
3D CAD file formats: .STEP, .STP, .IGES, .X_T
2D prints with tolerances: .PDF or .DWG highlighting critical dimensions, thread classes, and surface roughness targets.
• Material Specifications:
Exact alloy standard designation (e.g., ASTM A351 CF8M, DIN 1.4408, 4140 Steel).
Specify preferred heat treatment conditions (e.g., Solution Annealed, Normalized, Q&T to 30–34 HRC).
• Volume Projections:
Initial sample/prototype quantity.
Order batch size and Estimated Annual Usage (EAU).
• Quality Control & Testing Protocols:
Certification requirements (EN 10204 3.1 material certificate, CMM dimension report, hardness log).
Non-destructive testing requirements (e.g., 100% PT inspection, random 5% X-ray inspection).
• Secondary Surface Treatment & Packaging:
Coating specifications (e.g., Electropolish Ra ≤ 0.4 µm, Zinc Plating 8–12 µm, Passivation).
Special packaging requirements (VCI anti-rust bags, custom export wooden crates, individual cell dividers).