Premium CNC Machining Part Polishing Services
Achieve Ra < 0.05µm mirror finishes with Dimensional Integrity Polishing. We remove tool marks while strictly maintaining tolerances for metals and optical-grade plastics. Learn more about our process or contact us for details.
Premium CNC Machining
Part Polishing Services
From seamless tool mark removal to optical-grade mirror finishes (Ra < 0.05µm). We combine master craftsmanship with automated technology to ensure unmatched surface clarity without compromising your critical dimensional tolerances. Learn more about our about page.
The Science of Controlled Polishing
Precision engineering that focuses on protecting every micron of your design intent.
Dimensional Integrity
Standard buffing risks undersized parts. ProtoBatch employs strictly limited material removal to ensure precision shafts and bearing seats remain within their specified tolerance zones.
Geometric Fidelity
Avoid the "soap-bar" effect. By utilizing custom rigid abrasives, we preserve crisp edges and geometric profiles, preventing assembly failures caused by unintended edge rounding.
Repeatable Surface Ra
We eliminate surface waviness through multi-stage grit refinement. Whether you need a satin brush or a Ra 0.05µm mirror finish, our results are consistent across every batch.
Precision Polishing Standards: From Brushed to Mirror
Level 1: Machining Mark Removal
Eliminate visible tool paths and burrs to achieve a uniform Ra 0.8 - 1.6µm base. This smoothing stage is essential for industrial functional parts and optimal coating adhesion, especially after CNC machining.
Level 2: Satin & Brushed Finish
Achieve a sophisticated, low-glare aesthetic with consistent directional grain. Targeting Ra 0.4 - 0.8µm, it is the standard for high-end consumer hardware and electronic housings.
Level 3: Fine Polish & Buffing
Multi-stage refinement to remove all visible scratches, resulting in a smooth sheen. Reaching Ra 0.2 - 0.4µm, this finish enhances corrosion resistance for medical and food-grade components.
Level 4: Mirror & Optical Polish
Our highest "Super Finishing" level, delivering a distortion-free, reflective surface at Ra 0.02 - 0.05µm. Engineered for SPI A-1 mold cavities, optical light pipes, and aerospace trim.
Metal Polishing Techniques:
Engineering High-Performance Luster
Mechanical Polishing & Buffing
We utilize precision abrasive wheels, belts, and diamond pastes to eliminate CNC tool marks. Our multi-stage process transitions from heavy stock removal to fine buffing, achieving Ra levels down to 0.1µm on Aluminum, Stainless Steel, and Brass while maintaining strict dimensional integrity.
Electropolishing & Passivation
By electrochemically removing microscopic peaks, we achieve a burr-free, "sanitary finish" on 304 and 316L Stainless Steel. This process maximizes corrosion resistance and provides a mirror-like shine in complex internal geometries where mechanical tools cannot reach.
Precision Flat Lapping
For components requiring extreme flatness and sub-micron tolerances, our lapping services utilize fine-grain abrasives to produce ultra-smooth, uniform surfaces. It is the preferred method for high-pressure seals, valves, and optical-grade mating parts.
Mirror Finish & SPI Standards
Our hard luster finishing (SPI A-1/A-2) delivers a distortion-free, high-gloss surface with Ra values as low as 0.02µm. Essential for medical implants and injection mold cavities, this technique ensures a premium aesthetic and superior wear resistance.
ProtoBatch CNC delivers expert metal finishing solutions customized for precision manufacturing. Achieve technical excellence and surface perfection with our advanced, data-driven polishing technologies.
Advanced Plastic Polishing for Optical-Grade Transparency
Vapor Polishing Services
Vapor polishing utilizes specialized solvent vapors to chemically liquefy the surface of plastics like Polycarbonate (PC) plastic, Ultem, and Polysulfone. This process creates a "water-clear" finish without the risk of mechanical scratches or stress.
It is the preferred method for achieving internal channel transparency and clarifying complex geometries in medical manifolds, light pipes, and high-performance fluidic components.
Acrylic Flame Polishing
Flame polishing employs a high-temperature hydrogen-oxygen torch to melt the surface layer of Acrylic (PMMA) parts. The resulting surface tension creates a glass-like, high-gloss finish that eliminates haze and machine marks.
Ideal for flat surfaces and external edges, this technique provides a cost-effective solution for rapid prototyping of optical lenses, displays, and decorative CNC plastic components.
Mechanical Buffing & Compounding
Mechanical buffing uses multi-stage rotary wheels and specialized polishing waxes to smooth machined plastic surfaces. We transition through grit levels to remove CNC tool marks and restore a brilliant, haze-free luster.
Suitable for a wide range of materials including Acrylic and PC, buffing allows for precise manual control to achieve Ra 0.1–0.4 finishes while preserving critical part dimensions.
Material Mastery: Tailored Polishing for Peak Performance
Achieving a perfect mirror finish requires a deep understanding of material metallurgy and polymer science. ProtoBatch adapts polishing parameters—from abrasive grit to heat management—to the unique properties of each substrate, ensuring Ra consistency and dimensional integrity.
Aluminum & Stainless Steel
We achieve Ra 0.05 mirror finishes on Aluminum 6061/7075 while preventing oxidation. For Stainless Steel 304/316L, we combine mechanical buffing with electropolishing to reach sanitary, medical-grade standards without compromising critical tolerances.
Titanium & Brass
Titanium polishing utilizes specialized diamond pastes and strict thermal control to avoid surface hardening. For Brass and Copper decorative components, we deliver high-reflectivity, blemish-free surfaces ready for clear coating or plating.
Copper & Transparent Plastics
We specialize in optical-grade clarity for PC, PMMA, and PSU. Utilizing vapor polishing and specialized buffing, we eliminate machining haze and internal tool marks to achieve water-clear transparency for light pipes and lenses.
Substrate-Specific Compounds
We use material-matched abrasives to prevent pitting and ensure uniform surface roughness across batches.
Thermal & Pressure Control
Precision monitoring during the buffing process prevents part warping and "orange peel" surface defects.
Optical Quality Assurance
Rigorous inspection under specialized light boxes guarantees zero haze and maximum light transmission.
Precision Masking & Ultrasonic Cleaning
Protecting critical dimensions is as vital as achieving the perfect shine. ProtoBatch employs advanced masking techniques and multi-stage cleaning to ensure that polishing only occurs exactly where it is intended. Learn more about our company background and commitment to quality.
- Specialized masking to protect threads, bearing seats, and mating surfaces
- Custom-engineered fixtures to prevent edge rounding on sharp geometries
- High-frequency ultrasonic baths to eliminate all polishing compound residue
- Ensures a "Ready-to-Assemble" state for medical and optical components
Integrated Protection & Decontamination Process
Residue Removal
Our multi-stage ultrasonic cleaning strips away polishing waxes and abrasive pastes from blind holes and internal channels.
Tolerance Shielding
Using precision tapes and custom 3D-printed masks, we isolate critical features to maintain ±0.005mm dimensional integrity.
Purity Verification
inspection under high-intensity lighting ensures zero haze, no scratches, and a contamination-free surface finish.
Mastering Surface Roughness:
The Science of Ra Values & Finishing Standards
In precision polishing, Ra (Roughness Average) is the definitive metric for functional performance. ProtoBatch provides data-driven finishing to ensure your parts meet exact friction, seal, or optical requirements.
What is Ra Surface Roughness?
Ra represents the arithmetic average of profile height deviations. Our technicians use Ra measurement to quantify the transition from "machined" to "mirror-like", ensuring zero "orange peel" or surface waviness.
ProtoBatch CNC Finish Grades
Optical-grade clarity for lens molds, surgical tools, and SPI A-1 finishes.
High-performance finish for aerospace components and decorative consumer electronics.
Standard industrial finish that eliminates tool marks for improved fatigue resistance.
The baseline CNC surface suitable for non-mating parts and general industrial use.
Micro-level texture profiling ensures consistent Material Removal Rates (MRR) while maintaining critical dimensional integrity.
Data-Driven Quality: Verifying Ra, Gloss, and Geometric Precision
At ProtoBatch, "shiny" is not a specification—Ra is. We validate every polished surface through quantitative metrology, ensuring aesthetic brilliance never compromises the technical integrity of your precision components. Our quality assurance processes guarantee that every detail meets the highest standards.
Gloss Meter Verification (GU)
We quantify specular reflection using digital gloss meters, ensuring batch-to-batch consistency for consumer electronics and optical housings where reflectivity is a critical performance metric.
Ra Profilometry & Visual Grading
Using contact-stylus profilometers, we certify surface roughness down to Ra 0.02µm. Every part undergoes rigorous cosmetic inspection under standardized light boxes to eliminate haze, pits, or orange peel.
Post-Polishing CMM Dimensional Verification
Because mechanical polishing involves controlled material removal, we integrate CMM inspection to verify that critical dimensions—such as bearing seats and mating surfaces—remain strictly within the specified tolerance zone.
Industry Applications
Medical & Healthcare
Delivering electropolished surgical instruments and implants with Ra < 0.2µm. Our process ensures sanitary, biocompatible surfaces while strictly preserving critical dimensional integrity, meeting the highest medical industry standards.
Aerospace & Defense
Precision polishing of leading edges and engine components for drag reduction. We control material removal rates to within 5µm to meet stringent aerospace performance and safety standards.
Tooling & Mold Making
Achieving SPI A-1 mirror finishes in mold cavities to ensure high-gloss plastic injection parts. Our edge retention techniques prevent rounding, maintaining perfect tool geometry for high-precision manufacturing.
Consumer Electronics
Flawless mirror and satin finishes for aluminum housings and decorative trim. We provide batch-to-batch cosmetic consistency for premium, high-visibility consumer electronic components.
Optical Clarity Vapor Polishing
Experience superior transparency and surface finish with our advanced vapor polishing solutions. This process significantly improves optical clarity by smoothing surface irregularities, making it ideal for high-precision inspection hardware and polycarbonate components.
Automotive & Transportation
Enhancing powertrain efficiency and interior aesthetics through precision surface finishing. Our polishing solutions reduce friction in transmission gears and deliver showroom-quality shine for decorative automotive trim.
Precision Polishing Gallery: Surface Excellence & Dimensional Integrity
Explore the ProtoBatch standard of finish. From mirror-polished medical implants to vapor-polished optical components, we deliver superior Ra values without compromising your part's critical tolerances. View more in our
Expert Insights on Precision Polishing & Dimensional Integrity
Addressing the technical challenges of achieving optical-grade mirror finishes while maintaining strict engineering tolerances for medical and optical components.
Does Polishing Affect Part Dimensions?
Yes. Mechanical polishing typically removes 0.005mm to 0.02mm of material. Without precision control, "Edge Rounding" can occur, compromising the fit of mating surfaces.
ProtoBatch CNC Expert Tip:
We utilize Dimensional Integrity Polishing, compensating for material removal during CNC machining to ensure tolerances remain within ±0.01mm post-finish.
How Do You Polish Internal Cavities & Channels?
Internal geometries require specialized techniques. We use Abrasive Flow Machining (AFM) or manual micro-polishing to remove tool marks from manifold interiors and deep bores.
ProtoBatch CNC Expert Tip:
For transparent PC or Ultem, Vapor Polishing is the gold standard for achieving "Water-Clear" internal fluid paths where physical tools cannot reach.
Ra Value vs. Visual Mirror Finish
A low Ra (roughness average) doesn't guarantee a cosmetic mirror look. We distinguish between "Engineering Polish" for function and "Cosmetic Polish" for flawless visual reflectivity.
ProtoBatch CNC Expert Tip:
For optical clarity, specify an SPI-A2 finish. We use diamond paste polishing to remove micro-scratches that standard abrasive pads often leave behind.
Achieve the Perfect Mirror Finish
From optical-grade prototypes to mass production, ProtoBatch combines precision CNC machining with expert polishing and advanced surface finishing. Upload your drawings and specify your target Ra values to get an Ra-certified quote from our ISO 9001 facility.
