About PUWIN
Chengdu Puwin Precision Machinery Co, Limited was established in 2009, and specializes in customized machined parts and components. We devote to provide the most superior quality products with the best prices to assist our customers' competence in their markets. Over the last 16 years, Puwin has grown and developed into a manufacture with own foundry, machining, and inspection capabilities.
We can offer to our customers a wide range of products of high precision turned and milled parts, machined hot forged parts, machined lost wax investment castings, machined aluminium and zinc die castings. Our products gained recognition for their good quality and strict compliance with international standards, The range of the Components we produced includes parts for Pumps, Valves, Hydraulic parts, housings for actuators and gear boxes, cable glands, and other General mechanical parts from various industries. Our most common used materials are stainless steel, steel, brass, carbon steel, aluminium, Titanium Alloy, ect.
By combining advanced CNC machining technologies with comprehensive sub-assembly processes, we deliver complete, ready-to-install custom metal parts directly to your production line. Our end-to-end integration eliminates assembly bottlenecks and reduces your overall supply chain risk.
China's Manufacturing & Supply Chain Dominance
Unlocking Cost Efficiency, Advanced Technical Craftsmanship, and Complete Ecosystem Integration
Ecosystem Synergies
Chinese manufacturing hubs consolidate casting, forging, plating, and anodizing suppliers. This clustering minimizes internal logistics, allowing complex custom metal parts to transition from raw stock to finished assemblies rapidly.
Cost-Effective Scale
High-volume raw material procurement, highly optimized automated setups, and competitive labor for complex manual assembly stages dramatically lower the unit cost of multi-component custom metal parts.
Advanced Tech & Tooling
Continuous reinvestment in capital equipment means Chinese manufacturers deploy the latest 5-axis CNC machining centers, automated inspection systems, and precision assembly fixtures to guarantee quality.
Evaluating Assembly Expertise vs. Simple Machining
Why a Great Machining Shop Isn't Always a Great Assembly Partner
Many manufacturers excel at producing individual components using high-speed CNC machining. However, when those individual parts must be fitted together with tight tolerances, standard machine shops often struggle. Sourcing a partner for fully assembled custom metal parts requires verifying specific assembly capabilities.
Assembly is not just about tightening bolts; it is an engineering discipline. It involves managing tolerance stack-up, designing custom assembly fixtures, and performing functional tests to ensure the finished mechanism operates correctly. When vetting a Chinese manufacturer for assembly work, look beyond their rows of CNC machining centers and evaluate their dedicated assembly lines, testing equipment, and assembly-focused quality control staff.
Assembly Verification Checklist
- Do they perform formal tolerance stack-up analysis before production?
- Do they design and build custom assembly jigs and fixtures in-house?
- What testing capabilities do they have (e.g., pressure, leak, torque, or electrical tests)?
- Do they have dedicated dust-free assembly environments if required?
- Are their assembly operators trained specifically on torque limits and thread-locking compounds?
Tolerance Stack-Up Analysis
A critical step in assembling complex custom metal parts. Even if every single component passes inspection, minor variations within allowable tolerances can add up, causing the final assembly to bind or fail. A qualified assembly partner uses specialized software to simulate these variations before starting CNC machining.
Custom Jigs & Fixtures
Consistent assembly requires standardized processes. Top-tier suppliers design dedicated assembly fixtures to hold components in precise alignment during fastening, press-fitting, or adhesive bonding. This ensures that every assembled batch of custom metal parts meets identical dimensional specifications.
Functional Testing
An assembly partner must verify the performance of the finished product. This may include pressure testing for valve housings, torque testing for gearboxes, or load testing for structural brackets. Ensure your supplier's testing protocols match your operational requirements before starting volume CNC machining.
Our Factory & Production Capacities
Together with our established suppliers we can also offer you a choice of different surface finishes, like plating, coating, galvanizing etc., thus offering you a high production depth from one single supplier.
If needed, we can offer assembling according to your requirements – due to our wide production range also for parts consisting of components of different materials.
Quality Control & Communication Protocols
Ensuring Perfect Alignment on Technical Drawings, Prototypes, and Inspection Standards
Successful outsourcing of custom metal parts requires strict quality control systems. Miscommunication regarding 2D/3D drawings, tolerances, or surface requirements can result in costly scrap. Establishing a clear communication channel and quality protocol before starting production is critical.
We recommend aligning on geometric dimensioning and tolerancing (GD&T) standards, such as ISO 2768 or ASME Y14.5, during the initial RFQ stage. The manufacturer must verify that their CNC machining equipment can consistently hold these tolerances. Furthermore, a formal sample approval process, including First Article Inspection (FAI) reports or Part Submission Warrant (PSW) documentation, must be completed before starting volume production.
Using advanced coordinate measuring machines (CMM), optical comparators, and non-destructive testing (NDT) equipment ensures that every batch of custom metal parts matches the approved prototype.
1. Technical Drawing Alignment
Always provide fully detailed 2D drawings alongside 3D CAD models. Specify critical dimensions, surface roughness (Ra), heat treatment requirements, and threads. Never assume standard tolerances apply to critical mating interfaces.
2. First Article Inspection (FAI)
Before starting volume CNC machining runs, request a full FAI report. This report documents every dimension on the engineering drawing, confirming the supplier's setup is correct.
3. Standardized Inspection Criteria
Define clear Acceptable Quality Limits (AQL) for cosmetic and functional defects. Specify inspection methods, light levels, and go/no-go gauges to ensure objective quality assessments.
Logistics, Packaging, and Trade Terms
Navigating Incoterms, Protecting Delicate Assemblies, and Optimizing Customs Clearance
Incoterms Selection
Understand the differences between FOB, CIF, DDU, and DDP. For complex custom metal parts assemblies, DDP (Delivered Duty Paid) or CIF (Cost, Insurance, and Freight) are common options to manage shipping risks and customs clearance.
Customs & Tariffs
Classify your products correctly under the Harmonized System (HS) codes. Correct classification prevents clearance delays and ensures accurate duty calculations for your CNC machining assemblies.
Anti-Rust Packaging
Long sea transits expose metal to high humidity. Your supplier must use Vapor Corrosion Inhibitor (VCI) bags, desiccant packs, and protective oils to prevent oxidation on raw or machined steel surfaces.
Structural Protection
Heavy or delicate custom metal parts require custom-designed packaging, including foam inserts, divided crates, or reinforced pallets, to prevent transit damage.
Certification & Compliance
We manufacture to a very high standard, have strict quality controls and excellent service, which all benefits our customers. We have obtained ISO 9001, EN9100, TS16949, PED, AD 2000 W0 and ISO 14001 certification.
Customized for You
We are glad to welcome you on our website. Here, in brief, you will find important information about our company and our production capacities. If you would like to find out more, then do not hesitate to contact us and we will respond to you promptly.