What Is a Sandblasted Black Anodized Al6061 Positioning Plate?

A positioning plate made from Al6061 is commonly used in CNC fixtures, automation modules, laser equipment, optical alignment bases and robotic assemblies. When it goes through sandblasting + black anodizing, the part gains a matte-uniform appearance, stronger corrosion resistance, and better wear durability - often crucial for repeated clamping or positioning accuracy.

In our factory, this type of plate is one of the most requested components for machinery OEMs and fixture designers because it balances strength, machinability, and aesthetic quality.

Why Designers Prefer Al6061 for Positioning Plates

Based on real machining records from our workshop (2023–2024 batch data):

Property	Al6061-T6 Actual Data	Impact on Manufacturing
Hardness (HB)	95–100	Ideal for stable machining
Flatness after milling	≤0.03 mm / 200 mm	Good dimensional stability
Surface roughness before anodizing	Ra 0.4–0.8 μm	Smooth base for uniform anodizing
Anodizing layer thickness	10–18 μm	Adequate for industrial fixtures

These values come from our measurement log using Mitutoyo indicators & coating testers during three customer batches for automation fixture bases.

How Sandblasting Improves Surface Quality

Before anodizing, the plate is usually sandblasted (Bead blasting #100–#150). Based on our real workshop procedure:

Blasting pressure: 0.5–0.6 MPa

Nozzle distance: 180–220 mm

Resulting roughness: Ra 1.6–2.2 μm

Effect: Removes fine tool marks / blends corner transitions / gives matte texture

Customers choose sandblasting because it prevents the uneven gloss you get with raw CNC-milled aluminum, especially on large flat plates.

Black Anodizing Performance: Real Measured Data

We've anodized more than 8,000+ Al6061 fixture plates since 2019. Based on actual QC sheets:

Test Item	Typical Result	Notes
Coating thickness	12–16 μm	Suitable for industrial use
Color uniformity	ΔE < 1.0	When sandblasting is even
Salt spray resistance	336–480 hours	Based on customer-specific specs
Wear resistance	No visible scratch after 50 cycles	1kg load dry friction test

The black anodized layer also helps hide fingerprints and minor scratches, which is why automation equipment integrators prefer matte-black surfaces.

CNC Machining Process for the Positioning Plate (Step-by-Step)

This section matches How-To search intent.

1. Material Preparation

Raw Al6061-T6 plate verified by PMI

Saw cutting tolerance: ±0.3 mm

Stress-relief aging for plates over 8 mm thickness

2. Rough Milling

End mill Ø10 / Ø16 carbide

Feed: 1800–2200 mm/min

Depth of cut: 0.4–0.8 mm

Target: Remove 80–85% excess material

3. Precision Pocketing & Hole Machining

Tool radius compensation for tight tolerance zones

Key positioning holes kept at ±0.01 mm

Datum faces milled last to avoid stress shift

4. Deburring & Edge Processing

Robot brush or manual 800# sandpaper

Chamfer: 0.3–0.5 mm

5. Sandblasting

Matte, fingerprint-resistant finish

Ensures even anodizing tone

6. Black Anodizing

Hardness improved / anti-wear

Surface appearance becomes uniform deep black

Optional sealing: DI water sealing for better corrosion rating

Common Quality Issues & How We Fix Them

Based on real production cases.

1. Color Shade Inconsistency

Root causes:

Uneven sandblasting

Mixed batches of Al6061

Fix:
We run a batch-wise material hardness test and maintain fixed blast pressure.

2. Warping After Anodizing

Often happens on plates thinner than 6 mm.

Fix:

Pre-machining stress relief

Two-side balanced machining

Clamp-free anodizing racks

Flatness improved from 0.12 mm → 0.04 mm in a customer's 2024 order.

3. Fingerprint Marks on Semi-Gloss Surfaces

Fix:
Switch to fine sandblasting (#150 grit) + DI sealing - resulted in a 38% reduction in visible marks according to customer QC feedback.

Key Specifications Buyers Usually Ask For

This section satisfies transactional / commercial-intent queries.

Parameter	Typical Value
Material	Al6061-T6
Surface finish	Sandblasted + Black Anodized
Flatness	≤0.05 mm
Positioning hole tolerance	±0.01–0.02 mm
Plate thickness tolerance	±0.05 mm
Anodizing thickness	10–18 μm

If you need extremely tight tolerances (e.g., robotic optical calibration), we can keep holes within ±0.005 mm using reaming + temperature-controlled finishing.

Applications of Black Anodized Al6061 Positioning Plates

CNC fixture bases

Laser or camera positioning modules

Semiconductor equipment brackets

Robot calibration plates

Optical benches

Precision automation units

Our most common orders come from automation OEMs, smart equipment integrators, and R&D labs.

Pricing Insight: What Affects the Cost?

From our actual quotations in 2024–2025:

Main cost drivers

Plate size & thickness

Hole quantity and tolerance

Anodizing spec (standard / hard / matte-black)

Batch quantity (larger batches reduce cost by 18–35%)

Typical price range (reference only)

Small plates (80 × 60 mm): $4.8–$7.5 / pc

Medium plates (150 × 120 mm): $8.5–$14.0 / pc

Large plates (250 × 200 mm): $16–$28 / pc

(Prices depend strongly on drawing complexity & finishing requirements.)

FAQ About Sandblasted Black Anodized Al6061 Positioning Plates

1. Will anodizing affect dimensional accuracy?

Anodizing adds 5–10 μm per side. For tight tolerances, we undersize holes before anodizing.

2. Can the plate be made with Al7075 instead of Al6061?

Yes-Al7075 gives better strength but shows slightly less color uniformity after anodizing.

3. How to maintain a black anodized fixture plate?

Use alcohol wipes; avoid alkaline cleaners which may fade the coating.

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Processing Sandblasted Black Anodized Al6061 Positioning Plate