The Top Chinese NPI solutions Partner
We Offer a Variety of Surface Finishes for Custom Parts
High-quality surface finishing services enhance both the aesthetics and functionality of your products. We offer professional surface finishing for metals, composites, and plastics — turning your prototypes or products into practical and beautiful realities.
Our finishing services cover most manufacturing processes, including CNC machining, sheet metal fabrication, 3D printing, injection molding, casting, and more.
Ready to elevate your production? Let’s go !
- RPD Provide 24/7 Engineering Support All Year Round.
- All tools and dies are engineered and produced in house
- More Than 60+ Certified Materials for Choose. Offer CoCs, Material Certifications, Inspection Reports.
- ISO 9001:2015 quality standards.
- Expert DFM & process optimization
Surface Finishing Elevate Your Design
Surface finishing refers to a series of processes applied to the surface of manufactured products, aiming to give them a distinctive or desired appearance and tactile feel. Various techniques are used to enhance industrial components in terms of aesthetics, adhesion, weldability, corrosion resistance, hardness, electrical conductivity, and many other properties.
Your design deserves the best presentation. With our wide range of surface finishing options, you can improve its durability and appeal. Surface finishing can serve both functional and aesthetic needs. Each technique comes with specific requirements regarding material, color, texture, cost, and more. Elevate the quality of your project today!
As machined
Smooth
Anodizing
Sand Blasting
Polishing
Brushing
Black Oxide
Powder Coating
Teflon Coating
Painting
DLC
Passivation
PVD
Electroplating
Mirror Polishing
Heat treatment
Electropolishing
SPI Finish
Silk Screen
Alodine
Laser Engraving
Electroless Plating
Tumbling
Knurling
Textured
Semi-Gloss
High-Gloss
Matte/Frosted
Vapor Smoothing
Color Dyeing
Nickel Plating
Standard
| Common Types of Surface Treatment Simple List | |||||
| Surface Finish Type | Description | Services | Typical Applications / Benefits | Applicable Materials | Price |
| As machined | The state of the workpiece without any additional, specialized surface finishing or deburring treatment | CNC machining, Sheet Metal Fabrication, Injection Molding, Die Casting 3D Printing, Vacuum Casting | Suitable for products or prototypes without additional requirements for surface treatment | Metal, plastic | $ |
| Smooth | Deburring treatment | CNC machining, Sheet Metal Fabrication, Injection Molding, Die Casting 4D Printing, Vacuum Casting | Suitable for products or prototypes without additional requirements for surface treatment | Metal, plastic | $ |
| Electroplating | In an electrolyte solution, metal ions are attached to the surface of the workpiece by an electric current | CNC machining, Sheet Metal fabrication, Injection Molding, Die Casting, 3D printing, Vacuum Casting | Excellent anti-corrosion & appearance. Chrome/nickel plating provides bright, wear-resistant surface. Improves hardness, wear resistance & conductivity. | Metal | $$ |
| Anodizing | Electrochemical process generates a hard and porous oxide film on the surface of metal, usually for aluminum. | CNC machining, Sheet metal fabrication，Die Casting | High corrosion & wear resistance, excellent decoration (various colors via dye adsorption), good insulation, and ideal as a coating substrate for enhanced adhesion. | Metal | $$ |
| Powder Coating | Attach dry powder coating to the workpiece through electrostatic adsorption, and then cure at high temperature | CNC machining, Sheet metal fabrication，Die Casting | Thicker, durable, wear/impact-resistant. Solvent-free, eco-friendly, recyclable. Textures: gloss, matte, sanding, wrinkles. | Metal | $$ |
| Painting | Atomize liquid coating with a spray gun and attach it to the surface of the workpiece. | CNC machining, Sheet Metal Fabrication, Injection Molding,Die Casting 3D Printing, Vacuum Casting | The colors are infinite, theoretically any color can be blended. Relatively low cost, suitable for various shapes and sizes. | Metal, plastic, ceramic, Composite materials | $$ |
| Brushing | Forms a continuous fine texture to improve appearance, slip resistance, and reduce light reflection | CNC machining, Sheet metal fabrication，Die Casting | Highly decorative, presenting a metallic texture, able to cover small scratches, and resistant to fingerprints | Metal | $$$ |
| Sand Blasting | Mechanical treatment of workpiece surface by cleaning, roughening, or finishing using high-speed sand flow impact. | CNC machining, Sheet metal fabrication，Die Casting | Obtain a uniform matte/frosted texture, clean the surface, and improve coating adhesion. | Metal, plastic, ceramic | $$ |
| Black Oxide | It is a chemical conversion process that generates a layer of magnetic iron oxide (Fe ∝ O ₄) film on the surface of steel or stainless steel. | CNC machining, Sheet metal fabrication，Die Casting | Excellent dimensional stability, rust prevention, anti-reflective, and wear resistance (with post-processing). Provides a durable matte black finish with strong adhesion, low cost | Metal | $$ |
| Teflon Coating | Fluorinated polymer material/PTFE adheres and solidifies on the surface of the workpiece through a specific method. | CNC machining, Sheet metal fabrication，Die Casting | Non-stick surface for easy cleaning. Extremely low friction — ideal for oil-free bearings, gears, rails, and ski coatings. Excellent chemical, temperature, and weather resistance. UV & climate resistant | Metal, plastic, ceramic | $$$ |
| Electrophoretic | An advanced process combining electrochemistry and coating technology, paint particles “swim” to the workpiece surface and adhere uniformly under an electric field. | CNC machining, Sheet metal fabrication，Die Casting | No dead corners covers complex cavities, gaps, and edges. Uniform, precision-controlled coating with strong adhesion and excellent corrosion resistance. Highly automated & eco-friendly. | Metal | $$ |
| Passivation | Chemically or electrochemically converts the metal surface from active to inert (passive), significantly boosting its corrosion resistance. | CNC machining, Sheet metal fabrication，Die Casting | Improving wear resistance, passivation treatment hardly changes the size and color of the workpiece, and is non-conductive. | Metal | $$ |
| Alodine | Alodine is essentially a special chemical conversion coating treatment used for aluminum and aluminum alloys, belonging to a type of chromate treatment. | CNC machining, Sheet metal fabrication，Die Casting | Unparalleled adhesion, barrier & self-healing corrosion protection, extends aluminum corrosion resistance. Ultra-thin, conductive, dimensionally neutral. Decorative colors available. Enhances structural adhesive & sealant reliability | Metal | $$ |
| Chromate | Formation of passivation film for enhanced corrosion and oxidation resistance | CNC machining, Sheet metal fabrication，Die Casting | At a lower cost, it provides a surface solution that combines excellent corrosion resistance , enhanced adhesion, decorative color, and does not affect conductivity. | Metal | $$$ |
| PVD | PVD is like “evaporating” a material (such as titanium or chromium) in a vacuum, allowing its vapor to condense on the surface of the workpiece, forming a strong thin film. | CNC machining, Sheet metal fabrication，Die Casting | Gorgeous decoration: can be plated with TiN (gold), TiC (black), CrN (bright silver), etc. Extremely high hardness and wear resistance (such as DLC diamond-like coating). High temperature resistance, oxidation resistance, extremely thin coating, does not change the accuracy of the workpiece. | Metal, ceramic, plastic | $$$$ |
| CVD | The chemical reaction forms a thin film that improves abrasion resistance, high temperature resistance and corrosion resistance. | CNC machining, Sheet metal fabrication，Die Casting | Hard alloy, high-speed steel, ceramic | $$$$ | |
| DLC | DLC is a high-performance carbon based thin film formed by vapor deposition technology, which combines the high hardness of diamond and low friction properties of graphite. | CNC machining, Sheet metal fabrication，Die Casting | Ultra high hardness and ultra-low friction. | Metal | $$$$ |
| Electroless Plating | Homogeneous deposition of metallic coatings to improve corrosion resistance, abrasion resistance and electrical conductivity. | CNC machining, Sheet metal fabrication，Die Casting | Uniform coating on any complex shape. Precise thickness, no complex fixtures. Heat treatment to HV 1000 (near hard chromium). Corrosion resistant, weldable, magnetic/non-magnetic options. | Metal, plastic，silicone, glass | $$ |
| Electropolishing | Electrolysis removes minor surface imperfections and enhances smoothness and brilliance. | CNC machining, Sheet metal fabrication，Die Casting | Smooth, corrosion-resistant, hygienic. Reaches unreachable areas. No dimensional change. Medical/Food/Semiconductor grade. | Metal | $$ |
| Polishing | Rubbing or grinding surfaces to enhance smoothness and brilliance. | CNC machining, Sheet Metal Fabrication,Injection Molding,Die Casting 3D Printing, Vacuum Casting | Beautify appearance, high gloss, reduce surface defects and frictional resistance | Metals, plastics, ceramics | $$ |
| Mirror Polishing | Refers to the highest level of polishing where the surface is treated to have a mirror like optical reflection effect, which can clearly reflect the image. | CNC machining，Die Casting | Higher requirements than ordinary polishing, almost all for beautifying the appearance and decorating the surface. | Metals, plastics, ceramics | $$$$ |
| Shot Peening/Shot Blasting | Uses round media (steel, glass, ceramic balls) to improve fatigue strength & stress corrosion resistance, or for cleaning, rust/scale removal, deburring, and surface roughening. | CNC machining，Die Casting | Generates compressive stress to boost fatigue strength & stress corrosion resistance. Cleans surface (rust/scale removal) & creates a uniform matte finish. | Metals | $$ |
| Tumbling | Rotating or vibrating container creates rolling between workpiece and abrasive to remove burrs & sharp edges. Ideal for high-volume, small, non-deformable, impact-resistant parts. | CNC Machining, Sheet metal fabrication | Boosts surface hardness, removes oil/rust/impurities. Batch-deburrs sharp edges smoothly and safely at very low cost. | Metals, Plastics, Glass | $$ |
| Silk Screen | Ink is poured over a hollow-patterned screen, leaks through onto the workpiece, then dries or cures (baking/UV) to form the final pattern or text. | CNC machining, Sheet Metal Fabrication,Injection Molding,Die Casting 3D Printing, Vacuum Casting | Almost any material such as plastic, metal, glass, wood, and shape can be printed. | Metal, plastic,glass,etc | $ |
| Laser Engraving | The laser beam heats, melts or evaporates to mark, engrave or pattern engraving. | CNC machining, Sheet Metal Fabrication,Injection Molding,Die Casting 3D Printing, Vacuum Casting | A focused laser beam instantly vaporizes material for deep carving or alters its color/structure for marking, creating permanent marks. | Metal, plastic | $ |
| Knurling | Kuurling is a plastic processing technique that forms anti slip patterns on the surface of a rotating workpiece through extrusion or cutting. | CNC machining | Provide an anti slip grip surface to enhance the bonding strength of the mating parts and improve the industrial aesthetic and texture of the product. | Metals with good ductility, like aluminum, low-carbon steel, stainless steel, etc | $$ |
Optimize Processes and Output Stability Expert-Level Technical Support
Injection Mold Surface Finishes
| Item | SPI A | SPI B | SPI C | SPI D |
| Description | Mirror finish with exceptional smoothness and reflectivity. Ideal for high-end consumer products, optical components, and applications requiring pristine surface quality. | High gloss finish with excellent surface quality and minimal visible tool marks. Perfect for automotive parts, electronics housings, and premium consumer goods. | Semi-gloss finish with good surface quality and moderate tool marks. Suitable for general purpose applications, household items, and cost-effective production runs. | Matte finish with visible tool marks and textured appearance. Ideal for industrial applications, prototypes, and products where surface finish is not critical. |
| Finishing Look | High Gloss | Semi Gloss | Low Gloss | Matte |
| SPI Finish Grades | SPI A1, A2, A3 | SPI B1, B2, B3 | SPI C1, C2, C3 | SPI D1, D2, D3 |
| Surface Roughness Ra (μm) | SPIA1: 0.012 to 0.025 SPIA2: 0.012 to 0.025 SPIA3: 0.05 to 0.10 | SPI B1: 0.05 to 0.10 SPI B2: 0.10 to 0.15 SPI B3: 0.28 to 0.32 | SPI C1: 0.35 to 0.40 SPI C2: 0.45 to 0.55 SPI C3: 0.63 to 0.70 | SPI D1: 0.80 to 1.00 SPI D2: 1.00 to 2.80 SPI D3: 3.20 to 18.0 |
Why Choose RPD?
Professional CNC Machining, sheet fabrication, Injection Molding & rapid prototyping, Professional Services, Comprehensive A-Z Solutions.
Guaranteed Quality & Rigorous Inspection
Advanced Technology & Broad Capabilities
Technical Partnership & Engineering Support
Wide Material/Project Experience
Competitive Value & Cost Optimization
Speed & On-Time Delivery
End-to-End 6D Solutions, From Concept to Mass Production. Integrated 5 Steps Quality Control Across Every Stage.
Phase 1:TR / PRD (Technical Review / Product Requirements Definition)
DFM, material selection & tolerance optimization for manufacturability. .
Concept Validation: Support rapid prototyping for functional verification; identify structural and process risks early.
Cost Engineering: Deliver cost-oriented feedback to minimize redesign cycles prior to EVT.
Phase 2: EVT (Engineering Verification Test)
Precision Engineering: One-stop solutions combining high-speed CNC machining and precision injection molding to deliver tight-tolerance parts for validation testing.
Engineering Support: Offer all-round engineering support including tolerance stacking analysis, surface treatment recommendations, and design optimization.
Phase 3: DVT (Design Verification Test)
Agile Revisions: Quick response to design modifications, ensuring rapid turnaround for the next round of prototype verification.
Visual Samples: Provide visible samples (appearance masters) for design approval.
Incoming Control: IQC (Incoming Quality Control) services to secure material quality.
Phase 4: MVT (Medium-Volume Verification Test)
Process & Fixture Validation: Verify the stability of the production process and the reliability of fixtures/tooling.
Full-Line QC: Implement IQC (Incoming Quality Control) , IPQC (In-Process Quality Control) , and OQC (Outgoing Quality Control) to monitor pilot run quality.
Phase 5: PVT (Process Verification Test)
BOM & Version Control: Identify trial production issues.
Process Standardization: Establish Golden Line production standards to ensure process repeatability and stability.
Comprehensive QC: Full suite of IQC (Incoming Quality Control) , IPQC (In-Process Quality Control) , and FQC (Final Quality Control) services.
Phase 6: MP (Mass Production)
ISO-Certified QC: Full documentation for guaranteed quality.
Lean Manufacturing: Optimize cost & quality.
Efficiency Boost: Modular fixtures for quick changeover.
Full-Lifecycle QC: Routine IQC/FQC/OQC + Post-sale CAPA for continuous improvement.
Our Manufacturing Capabilities
Aluminium
Stainless Steel
Steel
Brass
Copper
Bronze
Titanium
Zinc
Low/Mild Carbon Steel
PA/Nylon
POM
PEEK
PMMA
PEI
PPS
PC
ABS
PET
PVC
pp
Rubber/Silicone
PE
HDPE
Carbon Fiber
As machined
Smooth
Anodizing
Sand Blasting
Polishing
Brushing
Black Oxide
Powder Coating
Teflon Coating
Painting
DLC
Passivation
PVD
Electroplating
Mirror Polishing
Heat treatment
Electropolishing
SPI Finish
Silk Screen
Alodine
Laser Engraving
Electroless Plating
Tumbling
Knurling
Quality Assurance for Every NPI’s Phase
At RPD, quality is embedded in every step of the manufacturing process. We conduct rigorous inspections across all three production phases—pre-production, in-production, and post-production. Full-Line QC: Implement IQC (Incoming Quality Control) , IPQC (In-Process Quality Control) , and OQC (Outgoing Quality Control) to monitor pilot run quality.using advanced equipment such as CMMs (Coordinate Measuring Machines), XRF analyzers, and high-precision measurement tools. With over 20 specialized inspection devices, including two high-accuracy CMMs, our quality control framework ensures that every part meets exact specifications.
Our ISO-certified quality team, supported by more than 10 dedicated quality engineers, brings nearly two decades of expertise in prototyping and manufacturing excellence. We provide detailed inspection reports covering functional performance, regulatory compliance, and dimensional accuracy. This commitment to precision and transparency guarantees that every component we deliver is reliable, traceable, and ready for integration—whether for rapid prototyping or full-scale production.
Custom Parts For Different Industries
Provide CNC Machining One-Stop Services for Different Industries
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Would you like to start a project with us?
How can we work close with our client?
A – Z Assistance:
1)Our professional team will provide 24/7 Engineering Support
by one-on-one assistance.
2)Our experienced engineers will freely review and optimize your part designs (DFM), provide actionable feedback, and deliver competitive quotations, which all based on your design drawings, application requirements, and desired outcomes.
4)Throughout production, you’ll receive progress updates every 2–3 days.
5) Upon completion, we’ll share high-quality photos of finished parts and packaging, along with full documentation: inspection reports, shipping details, and material certifications.
NPI Solutions with Expert Engineering Support
What Our NPI Engineering & Support Includes?
Design Review
Analyze CAD models for manufacturability, tolerance feasibility, and material suitability
Material Selection
Recommend the optimal metal, plastic, or composite based on strength, cost, and application needs。
Design Optimization
Adjust sharp corners, deep cavities, thin walls, or hard-to-machine details for efficient production
Tolerance Analysis
Ensure critical dimensions are achievable while avoiding unnecessarily tight tolerances that drive up cost
Tool Access Check
Identify features that may require special tooling or 5-axis machining
Cost Reduction Suggestions
Propose design changes that reduce cycle time, tool wear, or secondary operations
How to work with RPD?
Upload Design Drawing
- Send 2D/3D drawing online or by email
- Design Drawing format: STEP, IGES, DWG, PDF, STL, etc
- If you have multiple files, zip them or send by email to ashley@rdpmfg.com
DFM Analysis & Quote
- Our engineer team will review & analyze every file carefully.
- Request more details or provide optimize solution.
- Offer accurate quote with 6 hours.
Order Confirmation
- Confirm order & delivery details, sign the contract.
- Arrange & start to production.
- Check and confirm all details during production, Track every steps.
Parts Delivered
- Control quality during production.
- Provide order photos,inspection sheet and other request documents.
- Pack & label orders, then shipping.
FAQs About Our NPI Solutions Services
Why Tooling?
Tooling is the foundation of high-volume, repeatable manufacturing. Tooling turns a slow, manual process into a fast, automated, high-volume production system. If you need mass production, you must be choose tooling and molding production.
What kind of equipment do you use?
The molding workshop includes EDM, wire EDM, 50+CNC machining center, 50+injection machines ranging from 80 to 1000 tons, ect to meet different production requirements. Request equipment list, contact our team: ashely@rpdmfg.com.
Do you support export mold or production?
Yes, exactly. We support both. You can either for use at your own facility or leave it with us for long-term molding production.
What is your quality control system?
We operate under a rigorous Quality Management System (QMS) aligned with ISO standards. Our 5 Steps QC process is including IQC (Incoming Quality Control) , FQC (Final Quality Control) , OQC (Outgoing Quality Control) for routine production.
QE (Quality Engineering) / CAPA (Corrective and Preventive Actions) implemented throughout the entire product lifecycle, especially during the post-sale stage, to drive continuous improvement. Simply speaking 100% inspection before shipment to ensure zero defects.
What kind of quality assurance or warranty do you offer on orders?
One of the reasons engineers purchase from RPD is that we take on all the risks for you. We guarantee you’ll love what you get. Not happy with it? We’ll either redo it or give you a full refund. Your purchase is completely risk-free.
Why injection tooling is so expensive?
Material – Hardened steel (costly but durable for high volume)
Complexity – CNC, EDM, polishing; multi-cavity, undercuts add cost
Precision – Tight tolerances require advanced equipment & skilled labor
Customization – Every mold is custom-built for a specific part
Engineering – Significant design time for cooling, ejection, and geometry
Which kind of file formats can I send for tooling& production?
We accept STEP, IGES, STL, DWG, DXF, and other common CAD formats.
What Factors will Influence Tooling Design?
1. Part Geometry – Shape, size, and complexity drive mold design. Thin walls, intricate details, and complex geometries require specialized features like additional cooling or advanced gating systems.
2. Material Selection – The plastic type affects cooling rates, shrinkage, and flow. Polypropylene shrinks more; polycarbonate needs higher mold temperatures. Abrasive or corrosive plastics also demand wear-resistant mold materials.
3. Tolerances & Precision – High-precision parts (automotive, medical) require tighter mold tolerances — which complicates design and increases cost.
4. Ejection System – Ejector pins, air blasts, or stripper plates must be carefully integrated to remove parts without damage — affecting both design and cycle time.
5. Gate Design – Gate type and location (direct, pin, edge) control how molten plastic enters the mold, impacting part quality, surface finish, and cycle time.
6. Undercuts & Parting Lines – Undercuts or complex shapes may require side actions or lifters to release the part, increasing mold complexity and cost.
Can we store the mold at your facility for future production orders? Do you provide free maintenance for the mold?
Yes, we offer two key benefits for molds set up at our facility: free storage and free maintenance.
CNC Resources
What is a CNC Machining Center?
A CNC machining center is an advanced, computer-controlled machine tool capable of performing multiple machining operations—such as milling, drilling, tapping, boring, and sometimes turning.
Ashely . March 9, 2026
How many kinds of Types in CNC Machining Centers?
There are at least 5 different CNC lathes type in Machining Centers: Vertical Machining Center, Horizontal Machining, 5-Axis Machining Center, Gantry / Bridge Mill, Turn-Mill Center (Multi-Tasking).
Ashely . March 9, 2026
What is CNC Machining?
CNC (Computer Numerical Control) machining is a subtractive manufacturing process in which pre-programmed computer software controls the movement of factory tools and machinery to remove material from a solid workpiece, creating a finished part or product.
Ashely . March 9, 2026