In-House Precision Surface Finishing Lines · Turnkey Surface Engineering

Precision Metal & Plastic Surface Finishing Services

Q: How do you mathematically account for coating thickness during CNC machining?

For additive coatings like Type III Hard Anodizing (25–50 µm) or Electroless Nickel Plating (5–30 µm), dimensions undergo predictable physical growth. Our CAM engineers apply pre-machining offset compensation: for hardcoat anodizing adhering to the 50/50 penetration-to-buildup rule, we intentionally machine external diameters undersized and internal bore diameters oversized by 50% of the target coating thickness per side (equal to 100% of coating thickness on diameter) before processing. Critical bearing registers and interfaces tighter than ±0.01 mm are masked or precision ground post-coating.

Q: How is color consistency guaranteed across different anodizing production batches?

Anodizing dye absorption depends heavily on aluminum alloy purity, temper, grain orientation, and electrolyte temperature. To ensure maximum color consistency across multiple batches, AS Prototypes strictly sources traceable domestic mill-run alloy plates (6061-T6 or 7075-T651) from identical batch lots. We calibrate anodizing acid concentration, electrical current density, and dye bath temperatures under closed-loop digital control, inspecting parts against approved master color swatches under standard D65 daylight inspection lamps.

Q: How do you protect critical internal threads and tight bores during hardcoating or plating?

Critical internal threads (M2 to M24) and reamed dowel pin holes are protected using custom high-temperature tapered silicone plugs, silicone masking caps, precision die-cut Kapton tape dots, and chemical-resistant masking liquid before immersion in treatment baths. For critical threads that must be coated for corrosion defense, we machine with specialized 6G/6e oversized taps or run a calibrated post-treatment re-tap cleanout. Zero-growth conversion coatings like SurTec 650 are recommended when full conductive protection is required without masking.

Q: What is the primary difference between Chemical Passivation and Electropolishing for stainless steel?

Chemical passivation (ASTM A967) is a non-destructive chemical immersion in nitric or citric acid that selectively dissolves exogenous free iron from machined surfaces, developing an ultra-thin chromium oxide passive film without altering machined dimensions or baseline surface roughness (0 µm shift). Electropolishing (ASTM B912) is an electrochemical subtractive process that removes 5–15 µm of microscopic surface peaks, eliminating burrs, leveling micro-cracks, and producing a mirror-like finish (Ra under 0.2 µm) engineered for sterile surgical tools and cleanroom fluid handling.

Q: What is the realistic turnaround time for finished prototype and production parts?

Turnaround schedules are realistically calibrated to account for multi-step processing, chemical bath cycling, and stringent quality inspection. DFM engineering feedback and detailed quotes are provided within 24 hours. Rapid functional prototypes requiring standard surface finishes (such as Type II anodizing, bead blasting, or passivation) ship within 7 – 12 business days. CNC batch production runs (10 to 1,000+ pieces) involving complex multi-step finishes typically require 7 – 30 business days depending on geometry and batch volume. Factory completion schedules are strictly separated from international air express transit (3–5 business days via DHL/FedEx).

Industrial Surface FinishingMIL-A-8625 Type II & III HardcoatHigh-Phosphorus ENPASTM A967 PassivationSPI A-1 Optical PolishASTM B117 1,000h+ Salt Fog

Enhance mechanical wear endurance, environmental corrosion resistance, and cosmetic surface elegance for prototypes and production parts. AS Prototypes delivers comprehensive, mil-spec compliant metal and plastic surface finishing with strict pre- and post-treatment dimensional tolerance control (critical registers masked or ground to ±0.005–0.010 mm / ±0.0002″–±0.0004″), precision thread masking, and Coordinate Measuring Machine (CMM) verification (available upon request). From rugged hard anodized robotic components to mirror-polished optical mold cavities, our in-house finishing division guarantees flawless batch-to-batch consistency.

Type II & III

Anodizing Standards

MIL-A-8625 clear, black, colored & custom hardcoat

1,000+ Hrs

Corrosion Barrier

ASTM B117 neutral salt fog continuous chamber testing

Ra < 0.025 μm

Optical Mirror Polishing

SPI A-1 diamond hand-lapped & optical clarity

±0.010 mm

Tolerance Control

CAM growth offset (ISO 2768-mK general); ±0.005 mm only for ground or zero-growth registers

Upload CAD for Finishing Quote (Within 24h) →
View Finishing Specs Matrix ↓

Four CNC-machined 6061-T6 aluminum blocks comparing as-machined, bead-blasted clear, black Type II, and Type III hard anodizing

Figure 1: Side-by-side comparison of four identical CNC-machined 6061-T6 aluminum stepped housing blocks: As-Machined (Ra 1.6 µm), Bead-Blasted + Clear Type II Anodized, Deep Satin-Black Type II Anodized, and Dark Titanium-Grey Type III Hardcoat Anodized.

1. Metal & Plastic Surface Finishing Specifications Matrix

Comparative engineering benchmarks across layer thickness, surface roughness (Ra / µin standards), dimensional tolerances, salt fog corrosion endurance, and recommended substrate pairings:

↔ Swipe horizontally to inspect layer thickness, tolerances & corrosion standards

Surface Finish Selection & Engineering Specification Matrix (CNC Machined & Fabricated Parts)
Finishing Process	Compatible Substrates	Coating Thickness	Surface Roughness (Ra)	Corrosion & Hardness	Key Engineering Applications
Anodizing Type II (Sulfuric)	Aluminum (6061, 7075, 5052)	5 – 25 μm (0.2–1.0 mil) (50% in / 50% out)	Ra 0.8 – 1.6 μm (32–63 μin)	336+ hrs Salt Spray (ASTM B117)	Consumer electronics enclosures, robotics brackets, colored architectural trims.
Hard Anodizing Type III (Hardcoat)	Aluminum (6061-T6, 7075-T651)	25 – 50 μm (1.0–2.0 mil) (Heavy wear layer)	Ra 1.2 – 2.4 μm (48–95 μin)	450–550 HV0.05 (ASTM E384), 1000+ hrs Salt Spray	Aerospace hydraulic manifolds, sliding wear tracks, military-grade rugged enclosures.
Electroless Nickel Plating (ENP)	Steel, Stainless Steel, Copper, Aluminum	5 – 30 μm (0.2–1.2 mil) (Uniform internal bores)	Ra 0.4 – 0.8 μm (16–32 μin)	HV 900–1000 (after bake), 1000+ hrs	Precision valve spools, pump shafts, semiconductor fittings, fluidic manifolds.
Electrostatic Powder Coating	Carbon Steel, Sheet Metal, Aluminum	40 – 120 μm (1.6–4.7 mil) (Thermoset film)	Ra 2.0 – 4.5 μm (Smooth/Textured)	Extreme impact, chip & UV endurance	Precision sheet metal enclosures, telecom server racks, machine chassis.
Abrasive Bead Blasting	Aluminum, Stainless Steel, Titanium, Brass	0 μm (Subtractive micro-texture)	Ra 1.2 – 3.2 μm (48–125 μin, #80–#150)	Uniform satin matte, anti-glare	Tooling cutter mark removal, optical instrument housings, medical device chassis.
Chemical Passivation (ASTM A967)	Stainless Steel (303, 304, 316L, 17-4PH)	0 μm (Atomic Cr₂O₃ passive film)	Preserves baseline Ra	Eliminates free iron, ASTM B117 tested	Surgical medical instruments, food machinery, cleanroom hardware.
Black Oxide (MIL-DTL-13924)	Carbon Steel, Alloy Steel, Stainless Steel (Class 4)	< 1 μm (True zero dimensional change)	Preserves ground Ra	Anti-reflective, oil-retentive	Optical lens barrels, CNC fixtures, spline shafts, precision gears, fasteners.
Precision Zinc Plating & Galvanizing	Carbon Steel, Alloy Steel, Sheet Metal	5 – 25 μm (Electro) / 45 – 85 μm (HDG)	Ra 1.6 – 3.5 μm	Cathodic sacrificial zinc barrier	Outdoor structural brackets, chassis frames, heavy machinery mounting plates.
Optical Mirror Polishing (SPI A-1)	Hardened Mold Steels (S136), Acrylic, PC	0 μm (Subtractive diamond lapping)	Ra 0.012 – 0.025 μm (0.5–1.0 μin) (SPI A-1 Mirror)	Ultra-high reflectivity & mold release	Injection mold tool cavities, optical reflectors, clear light pipes.
Hard Chrome Plating (AMS 2460)	40Cr, 4140, Tool Steels, Cast Iron	20 – 100 μm (Industrial thick layer)	Ra 0.2 μm (Precision ground OD)	Rockwell C 65–70 (HV 850–1050)	Hydraulic cylinder piston rods, severe sliding pins, wear bushings, roll shafts.
Chemical Vapor Smoothing (3D Nylon)	HP MJF & SLS PA12, PA11, TPU	0 μm (Surface remelt levelling)	Ra drops from 8.0 to < 1.5 μm	100% Water & Gas Impermeable	Automotive ducts, fluidic manifolds, functional wearable orthotics, enclosures.
Chemical Vapor Polishing (PC & ABS)	Polycarbonate (PC), ABS	0 μm (Controlled vapor smoothing)	Ra < 0.05 μm (Water-clear clarity)	Annealed (60–80°C Constant-Temp for PC)	Microfluidic analytical chips, transparent fluid manifolds, medical sight glasses.

2. In-House Surface Finishing Capabilities & Texture Gallery

Inspect macro surface textures, layer thicknesses, and specific engineering applications across our comprehensive in-house and validated chemical processing lines:

Precision CNC Machined 6061 and 7075 Aluminum Parts with Type II and Type III Hardcoat Anodizing and Coating Thickness Inspection

MIL-A-8625 Type II & III

Precision Anodizing (Type II & Type III Hardcoat)

Al 6061, 7075, 50525 – 50 μm Film400–550 HV

Electrochemical conversion creating a durable aluminum oxide barrier. Type II Sulfuric (5–25 μm) provides vibrant cosmetic color dyeing and 336h salt spray protection. Type III Hardcoat (25–50 μm) delivers extreme abrasive wear resistance reaching 400–550 HV.

Tolerance Control: 50% penetration / 50% buildup. CAM pre-machining offset holds ISO 2768-mK general tolerances; critical bearing registers tighter than ±0.01 mm are masked or precision ground post-coating.

Precision CNC Machined Flange Housings with Uniform Electroless Nickel Plating Inspected with Height Gauge

ASTM B733 High-Phos ENP

High-Phosphorus Electroless Nickel Plating (ENP)

Steels, Copper, Aluminum5 – 30 μmHV 900–1000

Autocatalytic chemical reduction depositing 100% uniform layer thickness across internal cross-drilled channels, deep blind bores (aspect ratio 1:4), and precision threads without edge buildup. High-phosphorus (10–13% P) is non-magnetic with 1,000h+ salt spray endurance.

Bake Hardening: 400°C post-bake on steels precipitates Ni₃P crystals, elevating hardness to HV 900–1000 (HRC 65+); aluminum alloys are baked at 180–200°C to preserve T6 core temper.

Custom Sheet Metal Electronic Enclosure with Matte Textured Powder Coating Finish

40 – 120 μm Thermoset

Electrostatic Powder Coating Services

Sheet Metal, Carbon Steel, AlRAL / PantoneClass 5B Adhesion

Finely atomized thermoset polymers cured under 200°C heat. Superior impact resistance, chip resistance, and UV stability for sheet metal enclosures, brackets, and robot chassis. Available in fine texture, sand grain, smooth satin, and heavy wrinkle.

Multi-Stage Pretreatment: Iron phosphating and chromate conversion bath ensure ASTM D3359 Class 5B cross-hatch adhesion.

Mechanical Bead Blasting & Hairline Brushing

Aluminum, Stainless, BrassRa 0.4 – 3.2 μmSubtractive

Calibrated #80 to #150 glass and ceramic beads eliminate CNC cutter marks, micro-deburr sharp edges, and produce a uniform satin matte finish. Precision linear and circular brushing (#180 to #400 grit) creates distinctive directional hairline graining for front bezels.

Surface Roughness: Calibrated profilometer checks guarantee Ra 1.6 μm (blasting) and Ra 0.4 μm (fine hairline brushing).

Custom CNC Machined Black Anodized Aluminum Control Panel with Precision Laser Engraved Scales and Knobs on ESD Mat

0.01mm Precision Fiber Laser

Precision Silk Screen, Pad Print & Laser Engraving

Anodized Al, Painted Metal, PC±0.1 mm Align2D Data Matrix

High-definition graphics, regulatory CE/FCC legends, dial graduations, and traceability barcodes. Industrial 2-component epoxy inks withstand chemical wipes (ASTM D3359 5B). Fiber laser ablation generates crisp white high-contrast legends and permanent serialized codes.

Traceable Micro-Markings: Fiber lasers engrave micro 2D Data Matrix codes down to 2 mm x 2 mm for automated scan verification.

Cleanroom Passivated and Electropolished 316L Stainless Steel Surgical and Medical Components ASTM A967

ASTM A967 & AMS 2700

Chemical Passivation & Electropolishing

SS 303, 304, 316L, 17-4PH0 μm ShiftCr₂O₃ Passive Film

Nitric or citric acid decontamination selectively removes exogenous free iron from machined stainless steel, accelerating the formation of a dense, corrosion-resistant chromium oxide film (Cr₂O₃) for medical device hardware with zero dimensional shift.

Electropolishing Option: Microscopic peak leveling (ASTM B912) removes 5–15 μm, achieving Ra under 0.2 μm sterile cleanability.

Precision Black Oxide Conversion Coating

Carbon Steels, 4140, Stainless (Class 4)< 1 μm Zero GrowthOil-Retentive

Hot alkaline conversion coating transforming surface iron into black magnetite (Fe₃O₄). Delivers deep non-reflective optical absorption with anti-galling lubrication retention for spline shafts, drive gears, tooling fixtures, and optical mounts with zero dimensional growth.

Zero Dimensional Growth: Layer thickness is < 1 μm, completely safeguarding precision ground ±0.005 mm bearing registers.

Precision Zinc Plating & Galvanizing Services

Carbon Steels, Stamped Sheet5 – 25 μm ElectroEVA Tray Packaging

Sacrificial zinc coatings offering robust outdoor atmospheric rust defense. Electro-galvanizing (5–25 μm blue-white, yellow, or black zinc) preserves fine thread engagement, while hot-dip galvanizing (45–85 μm) provides decades of outdoor structural barrier protection.

Export Packaging: Finished parts packed in CNC-milled anti-static EVA foam trays and heavy-duty export cartons for damage-free transit.

Hardened Tool Steel Injection Mold Core with SPI A-1 Diamond Mirror Polish

SPI A-1 / Ra 0.012 – 0.025 μm

Optical Mirror Polishing (SPI A-1 / A-2)

S136, NAK80, Tool SteelsSubtractive < 3 μmDiamond Lapped

Multi-stage diamond paste hand-lapping eliminating microscopic tool marks and EDM recast layers down to Ra 0.012 – 0.025 μm (SPI A-1). Engineered for injection mold tooling cores, acrylic light pipes, and laser mirror surfaces with zero orange peel.

True Optical Clarity: Flawless specular reflection guarantees effortless molded plastic part release and distortion-free optical transmission.

Heavy-Duty Industrial Hard Chrome Plating

40Cr, 4140, Hydraulic Rods20 – 100 μmHV 850–1050

Functional hard chrome electrodeposition depositing a dense, micro-cracked chromium structure. Offers extreme surface hardness (65–70 HRC), low coefficient of sliding friction (0.12), and exceptional galling resistance for hydraulic piston rods and pins.

Cylindrical Grinding: Chromed shafts undergo precision cylindrical grinding to Ra 0.2 μm, maintaining strict concentricity and runout.

Industrial 3D Printing Chemical Vapor Smoothing

MJF / SLS PA12, PA11, TPUZero GrowthRa < 1.5 μm

Automated vapor chamber processing that selectively liquefies and reshapes polymer micro-pores. Transforms rough, powdery HP MJF and SLS nylon components into smooth, semi-gloss, injection-molded quality parts that are 100% airtight and watertight (rated 2–3 bar).

Sealed Micro-Pores: Eliminates bacteria traps for medical orthotics and enables seamless fluidic duct and manifold operation.

Optical Diamond Flycutting (PMMA) & Solvent Vapor Polishing (PC)

PMMA (Diamond Milled)Polycarbonate (PC), ABSRa < 0.05 μmAnnealed 60–80°C (PC)

Specialized optical finishing combining ultra-precision diamond flycutting for PMMA with controlled solvent vapor smoothing for PC and ABS. PMMA (Acrylic) is machined using Single-Point Diamond Flycutting (SPDT) and multi-stage diamond buffing to achieve SPI A-1 optical clarity without chemical solvents. Polycarbonate (PC) and ABS undergo controlled solvent vapor smoothing (DCM/acetone vapor reflow) for complex internal cross-drilled channels, followed by mandatory 60–80°C constant-temperature stress-relief annealing to eliminate micro-crazing.

Mandatory Annealing (PC): 60–80°C oven annealing for 2–4 hours to completely relieve DCM solvent stress | PMMA: Pure mechanical SPDT diamond milling and buffing (zero solvent contact).

3. Surface Finishing DFM & Dimensional Tolerance Compensation

Achieving post-finishing dimensional perfection requires exact coordination between CAM cutter toolpaths and chemical bath buildup characteristics:

50/50 Growth Rule

Type III Hardcoat (CAM Pre-Compensation)

Type III hardcoat builds up 50% on the exterior surface and penetrates 50% into the aluminum substrate. A 50 μm total coating adds 25 μm outward per surface (+50 μm on outer diameter, -50 μm on inner bore diameter).

Real-World Engineering Practice: Because chemical bath coating tolerances (±5–10 μm) and blind bore Faraday cage effects exceed ultra-tight bearing tolerances, critical bearing journals tighter than ±0.010 mm (e.g., Φ 20.000 +0.010/0 mm) are masked with custom silicone plugs during anodizing or precision diamond reamed/ground post-coating to ensure exact nominal press fits.

Precision Masking

Custom Silicone Thread & Bore Masking

Because 60° thread flank geometry displaces radially by 2t (1/sin 30°), diametral pitch diameter clearance reduces by 4t (4× additive coating thickness). For 100% additive plating (such as 25 μm ENP), pitch diameter shrinks by ~100 μm, locking standard fasteners unless masked or tapped with 6G/6e clearance taps.

Protection Standards: We utilize tapered high-temperature silicone plugs (M2 to M24), pull-through cords, and precision die-cut Kapton tape dots to shield blind threaded holes, reamed dowel pin registers, and electrical grounding pads. Threads remain 100% clean, paint-free, and pass Go/No-Go thread gauge inspection immediately.

Zero Growth

True Zero-Growth Chemical Finishes (< 1 μm)

When ultra-precise mating tolerances (±0.005 mm) cannot accommodate additive coating thickness, zero-growth chemical conversion processes are ideal.

Available Processes: Chemical Passivation (ASTM A967, < 0.1 μm), Black Oxide (MIL-DTL-13924, < 1 μm), and Chromate Conversion (SurTec 650 / Alodine 1200S, < 0.8 μm) convert surface metallurgy without adding measurable dimensional shift, ensuring zero interference in tight assembly stacks.

8-Point Surface Finishing Dimensional Growth Compensation, Thread Masking & Pre-Machining DFM Matrix
Surface Finish / Coating	Total Film Thickness	Net Outward Growth per Surface	Impact on External OD / Internal Bore ID	Mandatory CAM & Masking DFM Protocol
1. Type II Sulfuric Anodizing (MIL-A-8625)	8 – 20 μm	+4 to +10 μm per side (50% in / 50% out)	OD grows +8–20 μm; Bore ID shrinks –8–20 μm	Plug H7 bearing bores and M2–M6 fine threads with tapered silicone plugs; pre-bead-blast (#120) to hide milling cutter marks.
2. Type III Hardcoat Anodizing (MIL-A-8625)	25 – 50 μm	+12.5 to +25 μm per side (50% in / 50% out)	OD grows +25–50 μm; Bore ID shrinks –25–50 μm	Apply CAM pre-machining offset or mask tight registers (≤ ±0.010 mm); radius sharp external edges (R ≥ 0.2–0.5 mm) to prevent corner flaking.
3. Electroless Nickel Plating (ASTM B733)	5 – 30 μm	100% additive buildup (+5 to +30 μm/side)	OD grows +10–60 μm; Thread pitch diameter shrinks 4 × t	Deposits 100% uniformly inside blind bores; tap threads with oversized 6G/6e taps or mask threaded holes prior to chemical bath immersion.
4. Chromate Conversion (Alodine / SurTec 650)	0.2 – 0.8 μm	< 0.5 μm (True Zero-Growth Conversion)	Zero measurable shift on ±0.005 mm fits	Ideal for EMI/RFI electrical grounding lands and tight dowel/bearing bores where insulating anodized layers are prohibited.
5. Chemical Passivation (ASTM A967) & Black Oxide	< 0.1 – 1.0 μm	Zero dimensional growth (0 μm shift)	Preserves exact CNC machined & ground tolerances	Requires zero masking; specify on 304/316L/17-4PH surgical stainless steel and 4140 alloy steel spline shafts.
6. Electropolishing (ASTM B912)	–5 to –15 μm (Subtractive)	Removes 5–15 μm of surface peaks per side	OD shrinks –10–30 μm; Bore ID enlarges +10–30 μm	Micro-deburrs external thread crests and levels surface roughness down to Ra < 0.2 μm for cleanroom and UHV manifolds.
7. Electrostatic Powder Coating	60 – 120 μm	100% additive thermoset film (+60–120 μm/side)	Adds 0.12–0.24 mm across mating sheet metal edges	Mask all PEM self-clinching nuts, studs, grounding pads, and sliding chassis rails with high-temp silicone caps and die-cut Kapton dots.
8. PC Solvent Vapor Polishing vs. PMMA SPDT	0 μm (Reflow / Lapping)	Ra drops to < 0.05 μm optical clarity	Preserves microfluidic channel geometry	PC/ABS requires mandatory 60–80 °C constant-temp oven annealing to prevent solvent stress crazing; PMMA must be mechanically diamond-milled/buffed (never solvent-fumed).

4. Coating Metrology, Environmental Reliability Testing & Packaging

Every surface treatment batch is validated against rigorous international test standards in our quality inspection laboratory:

±1 μm

Digital Eddy-Current DFT

Non-destructive digital coating thickness gauges measure anodize, electroplate, and powder film depth across 3D profiles.

Class 5B

ASTM D3359 Adhesion

Cross-hatch lattice scribing and pressure-sensitive 3M tape tests confirm zero flaking or peel delamination on all coated parts.

1,000+ Hrs

ASTM B117 Salt Spray

Continuous neutral salt fog chamber testing verifies galvanic and environmental corrosion barrier resistance prior to shipment.

CNC EVA

Custom Protective Packaging

Precision-machined parts nested in CNC-milled anti-static EVA foam trays and heavy-duty corrugated cartons for safe global air freight.

5. Production Turnaround Schedules & Logistics

1. DFM & Quote

Within 24 Hours

Full manufacturability review, coating thickness tolerance analysis & transparent itemized quote.

2. Rapid Prototype

4 – 8 Business Days

Single-part CNC milling/turning or 3D printing with baseline as-machined or bead blasted finish.

3. Finished Surface

7 – 12 Business Days

Complete functional prototypes with Type II/III anodizing, plating, powder coat, or vapor polish.

4. Batch Production

7 – 30 Business Days

Low-to-mid volume manufacturing (10 to 1,000+ units) with full batch inspection and FAIR documentation.

Turnaround Terms: All schedules represent factory completion and quality inspection sign-off (Ex-Factory Production & Inspection Turnaround). International priority air express delivery (via DHL, FedEx, or UPS) requires an additional 3 – 5 Business Days depending on destination customs clearance.

6. Frequently Asked Questions (FAQ)

How do you mathematically account for coating thickness during CNC machining?+

For additive coatings like Type III Hard Anodizing (25–50 μm) or Electroless Nickel Plating (5–30 μm), dimensions undergo predictable physical growth. Our CAM engineers apply pre-machining offset compensation: for hardcoat anodizing adhering to the 50/50 penetration-to-buildup rule, we intentionally machine external diameters undersized and internal bore diameters oversized by 50% of the target coating thickness per side (equal to 100% of coating thickness on diameter) before processing. Critical bearing registers and interfaces tighter than ±0.01 mm are masked or precision ground post-coating.

How is color consistency guaranteed across different anodizing production batches?+

Anodizing dye absorption depends heavily on aluminum alloy purity, temper, grain orientation, and electrolyte temperature. To ensure maximum color consistency across multiple batches, AS Prototypes strictly sources traceable domestic mill-run alloy plates (6061-T6 or 7075-T651) from identical batch lots. We calibrate anodizing acid concentration, electrical current density, and dye bath temperatures under closed-loop digital control, inspecting parts against approved master color swatches under standard D65 daylight inspection lamps.

How do you protect critical internal threads and tight bores during hardcoating or plating?+

Critical internal threads (M2 to M24) and reamed dowel pin holes are protected using custom high-temperature tapered silicone plugs, silicone masking caps, precision die-cut Kapton tape dots, and chemical-resistant masking liquid before immersion in treatment baths. For critical threads that must be coated for corrosion defense, we machine with specialized 6G/6e oversized taps or run a calibrated post-treatment re-tap cleanout. Zero-growth conversion coatings like SurTec 650 are recommended when full conductive protection is required without masking.

What is the primary difference between Chemical Passivation and Electropolishing for stainless steel?+

Chemical passivation (ASTM A967) is a non-destructive chemical immersion in nitric or citric acid that selectively dissolves exogenous free iron from machined surfaces, developing an ultra-thin chromium oxide passive film without altering machined dimensions or baseline surface roughness (0 μm shift). Electropolishing (ASTM B912) is an electrochemical subtractive process that removes 5–15 μm of microscopic surface peaks, eliminating burrs, leveling micro-cracks, and producing a mirror-like finish (Ra under 0.2 μm) engineered for sterile surgical tools and cleanroom fluid handling.

What is the realistic turnaround time for finished prototype and production parts?+

Turnaround schedules are realistically calibrated to account for multi-step processing, chemical bath cycling, and stringent quality inspection. DFM engineering feedback and detailed quotes are provided within 24 hours. Rapid functional prototypes requiring standard surface finishes (such as Type II anodizing, bead blasting, or passivation) ship within 7 – 12 business days. CNC batch production runs (10 to 1,000+ pieces) involving complex multi-step finishes typically require 7 – 30 business days depending on geometry and batch volume. Factory completion schedules are strictly separated from international air express transit (3–5 business days via DHL/FedEx).

Elevate Your Machined & Fabricated Parts with Production-Grade Finishes

From rapid prototype color matching to mil-spec hard anodizing, precision chemical plating, and optical polishing, AS Prototypes delivers turnkey surface engineering with zero quality compromise. Upload your 3D CAD models for an instant DFM manufacturability and coating thickness review.

STEPIGESX_TDWGPDFMax 100MB

Request an Instant Quote (Upload CAD) →
Factory Equipment List →

• Strict NDA Confidentiality• Pre-Compensated CAM Machining• Coordinate Measuring Machine (CMM) Inspection (Available Upon Request)• Export-Grade EVA Packaging