What Size of Burrs Can Be Removed by Burnishing Process?

1. Clarify Two Distinct Types of Burrs

Do not confuse these two categories during process evaluation:

1. Filamentous / thin micro burrs (CNC sharp edges, stamping roll-over burrs) Thin cross-section with narrow root; easy to break under friction. Burnishing can remove them relatively easily.
2. Thick flash / bulky parting lines (residual casting gates, heavy casting burrs) Wide root and large solid volume. Removing such features requires substantial stock removal. If beyond burnishing capacity, pre-machining is mandatory.

Universal industry evaluation rule: burr root thickness is the core indicator, rather than only the outward extension length.

2. Stable Removable Burr Reference Range for Different Burnishing Equipment

2.1 Dry Compartmentalized Drum Burnishing (Most Widely Used)

Characteristics: No liquid cooling, flexible dry friction with limited material removal. Suitable for finishing and surface leveling.

• Zinc alloy, aluminum alloy, copper: Stably remove burrs with root thickness ≤0.03 mm; extreme short trial run upper limit 0.04～0.05 mm (not recommended for continuous mass production).
• 304/316 stainless steel: Stably remove ≤0.02 mm root burrs; extreme limit 0.03 mm.
• TC4 titanium alloy, nickel / cobalt-based superalloys: Stably remove only micro sharp edges ≤0.01 mm. Do not process flash thicker than 0.015 mm, otherwise surface overheating, work hardening and discoloration will easily occur.

⚠️ Critical Limitations: Without water lubrication and cooling, processing thicker burrs requires long grinding cycles, leading to accumulated friction heat. Soft metals risk deformation; titanium and superalloys face oxidation and thermal burns. Process Positioning: Only for finishing stage to eliminate micro sharp edges and fade shallow tool marks. Not for heavy removal of thick flash.

2.2 Wet Tumble Burnishing (With water & polishing fluid cooling; higher cutting capacity than dry burnishing)

Liquid provides buffering, allowing high-cut ceramic abrasives and longer processing cycles.

• Soft alloys (zinc, aluminum, copper): Stably remove burrs ≤0.05 mm root thickness; extreme limit 0.06～0.07 mm.
• Ordinary stainless steel: Stably remove ≤0.03 mm; extreme limit 0.04 mm.

Disadvantages: Risk of water stains; unsuitable for post-PVD or post-electroplating rework. Tiny holes tend to trap contaminants.

2.3 Drag-Type / Horizontal Fixture Burnishing (Individually clamped, no workpiece collision)

Free from stacking interference; rotating speed and immersion depth are adjustable to moderately raise grinding intensity. Removal capacity sits between ordinary dry drum and wet tumble burnishing. Material thresholds remain consistent: Aluminum / zinc alloy ≤0.03 mm; stainless steel ≤0.02 mm; titanium alloy ≤0.01 mm. Core advantage: No mutual collision damage even with extended processing time, ideal for thin-walled and long parts.

3. Hard Process Red Line – Do Not Rely Solely on Burnishing Beyond These Sizes

• Soft alloy flash root thickness ＞0.05 mm
• Stainless steel flash root thickness ＞0.03 mm
• Titanium / superalloy flash root thickness ＞0.015 mm

If processed solely by burnishing, three major consequences appear: ① Processing time multiplies and production capacity drops sharply ② Abrasives passivate rapidly, raising consumable costs ③ Continuous edge abrasion leads to out-of-tolerance dimensions; thin-walled deformation risk rises significantly

✅ Standard Mass Production Workflow: Pre-treatment by robotic force-controlled sanding / manual belt grinding → Burnishing finishing for micro deburring & brightening

4. Five Major Factors That Change Deburring Capacity

For burrs of identical thickness, removability varies greatly based on the following conditions:

1. Abrasive Selection High-cut triangular ceramic abrasives deliver the strongest stock removal; medium-soft spherical ceramics come second. Resin abrasives and plant-based abrasives (walnut shell) are only for light finishing and barely remove solid flash.

Plant-based abrasives cannot be used for solid flash removal, only for surface brightening and fine dust cleaning.

2. Burr Location Exterior planar and outer-circle burrs are easy to remove. Burrs inside grooves, gaps and hole openings are far more difficult. Burnishing is generally ineffective for internal deep-hole burrs; assign such work to magnetic polishing.

3. Workpiece Structure Solid thick-walled parts tolerate longer grinding cycles. Thin shells (wall thickness ＜1.2 mm) require reduced grinding intensity even with tiny burrs.

4. Compartment Design & Loading Ratio Effective compartment separation and reasonable loading (60%～70%) ensure good abrasive flow. Overloaded, non-compartmentalized drums cause stagnant material movement and drastically lower deburring efficiency.

5. Rotating Speed & Segmented Process Higher speed raises grinding force. However, speed cannot be increased arbitrarily in dry processing to avoid thermal oxidation. For thicker burrs, segmented processing with intermediate cooling performs better than one continuous long cycle.

5. Frequently Asked Production Scenarios

Q1: Can dry burnishing remove 0.01～0.02 mm micro sharp edges after CNC machining?

✅ Fully feasible. This is the standard application of dry burnishing, achieving both edge breaking and texture refinement in one step.

Q2: Can dry burnishing directly handle 0.06 mm zinc alloy die-casting parting lines?

❌ Not recommended. Processing time will be extremely long, causing uneven edge over-polishing and inconsistent gloss. The correct workflow: pre-grind to reduce parting lines below 0.03 mm before dry burnishing.

Q3: Can wet burnishing remove continuous filament stamping burrs of 0.04 mm on aluminum parts?

Wet burnishing with high-cut ceramic abrasives can achieve this in trials. Stable mass production via dry burnishing is difficult; prefer pre-tumble rough grinding.

Q4: Can burnishing remove 0.02 mm burrs inside holes and threads?

❌ Abrasives struggle to continuously enter narrow inner cavities. Use burnishing for outer surfaces and magnetic polishing for residual internal hole and gap burrs.

6. Conclusion

1. Burnishing is a micro-finish tumbling process. Its strength lies in eliminating micro filamentous sharp edges and leveling shallow textures. It is not designed for heavy stock removal of thick solid flash.

2. Safe mass production threshold (measured by burr root thickness):

• Dry compartmentalized drum burnishing: Al / Zn / Cu ≤0.03 mm; Stainless steel ≤0.02 mm; Titanium / Superalloy ≤0.01 mm
• Wet tumble burnishing: Al / Zn / Cu ≤0.05 mm; Stainless steel ≤0.03 mm

3. If raw blank burrs exceed the material corresponding safe limit, pre-rough machining must be arranged. Extending burnishing time alone inevitably results in losses in yield, efficiency and cost.

4. Optimized Process Chain: Robotic / belt rough grinding (remove thick flash) → Burnishing (outer surface micro deburring, leveling & brightening) → Magnetic polishing (residual burrs in inner holes and gaps)