Case Studies

Case Study: Hybrid Precision Manufacturing of Mu-Metal Components for a World-Class Audio Equipment Manufacturer
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1. Executive Summary
A globally recognized high-end audio equipment manufacturer engaged Qualitetch Components to resolve a critical manufacturing issue affecting a new line of studio-grade amplifier enclosures. The component in question was a mu-metal diaphragm plate, 1.00 mm thick, requiring 128 micro-drilled holes of 0.65 mm diameter, with asymmetric tolerances of +0.05 mm / –0.01 mm.
This component served a dual function:
• Electromagnetic shielding to prevent signal interference
• Acoustic airflow control within the sealed enclosure for resonance tuning
Traditional manufacturing methods—such as punching, laser cutting, and chemical etching—failed to meet tolerance and quality requirements. The client experienced inconsistent hole sizes, thermal damage to the mu-metal (affecting its magnetic permeability), and unacceptable burr levels.
Qualitetch proposed a hybrid solution:
1. CNC Micro-Drilling to achieve precise, thermally clean hole features
2. Wire EDM Profiling to cut the external profile stress-free, burr-free, and to tight tolerance
The result: high-yield production of high-integrity components with minimal scrap, no post-processing, and full compliance with tight mechanical, acoustic, and electromagnetic specifications.
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2. Application Context
About the Client
The client designs and manufactures some of the world’s most respected audiophile equipment, including analog amplifiers, phono stages, DACs, and studio monitor systems. Their brand is synonymous with signal clarity, noise isolation, and meticulous mechanical design.
Component Function
This custom component was a shielding diaphragm installed within the amplifier housing, responsible for:
• Shielding sensitive signal circuitry from internal and external EMI
• Modulating internal air pressure and flow to reduce resonance effects
• Acting as a grounded mechanical interface between internal subassemblies
Specification Summary
• Material: Mu-metal (nickel-iron alloy), 1.00 mm thick
• Hole Count: 128 holes per plate
• Hole Diameter: 0.65 mm
o Tolerance: +0.05 mm / –0.01 mm
• Hole Positional Accuracy: ±0.02 mm
• Burr Height: ≤10 µm (target: <5 µm)
• Hole Roundness: ≤5 µm
• Surface Finish: Ra ≤ 0.25 µm
• External Profile: Complex shape with locating notches, tabs, and edge transitions
• Shielding Effectiveness: No loss in magnetic permeability after processing
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3. The Problem
What Was Going Wrong
The client attempted to manufacture the plate using several conventional methods:
• Laser drilling caused overheating and warping
• Punching and stamping resulted in excessive burrs and edge distortion
• Chemical etching produced inconsistent hole dimensions and rough edges
• Post-annealing was required in all cases, adding 48+ hours of lead time
These issues led to:
• Distorted hole diameters outside tolerance
• Audible degradation in acoustic testing
• Loss of magnetic shielding performance
• High scrap rates (~30%)
• Missed launch timelines
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4. Qualitetch’s Hybrid Manufacturing Solution
To resolve both the dimensional and functional challenges, Qualitetch designed a dual-stage cold machining process tailored specifically for mu-metal and the component’s dual-role design.
Stage 1: CNC Micro-Drilling
Why Drilling?
At 0.65 mm diameter, with a tight –0.01 mm tolerance, drilling offered superior control over both the hole size and edge quality—without the heat damage associated with lasers or the stress of mechanical punching.
Key Parameters:
• Drill Tooling: micro-drills, Ø0.65 mm ±0.002 mm
• Spindle Speed: 38,000 RPM
• Pecking Strategy: Micro peck with coolant burst
• Clamping: Vacuum chuck + precision pins (flatness tolerance ±2 µm)
• In-Process QC: Optical verification every 10 holes
• Burr Control: Exit speed reduction + backing plate support
Results:
• Hole diameter: 0.650 mm ±0.02 mm
• Roundness: ≤2 µm
• Burr height: <5 µm, no deburring needed
• No thermal damage → shielding performance preserved
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Stage 2: Wire EDM Profiling
Why Wire EDM?
The external geometry of the plate featured tabs, slots, and curved transitions that required high dimensional fidelity, burr-free edges, and zero mechanical distortion—ideal for stress-free wire EDM.
Key Parameters:
• Wire Type: 0.25 mm Tungsten
• Cut Path Tolerance: ±0.01 mm
• Profile Accuracy: Maintained across full perimeter
• Cooling Strategy: Fully submerged dielectric bath
• Edge Finish: Ra ≤0.3 µm, no recast layer
Results:
• Edge fidelity: 100% profile match to CAD
• No burrs or sharp transitions
• Component flatness: ≤10 µm
• No distortion → perfect assembly fit
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5. Technical Results
Metric Target Spec                                            Achieved Result
Hole Diameter 0.65 mm (+0.05 / –0.01)            0.650 mm (+0.05 / –0.01)
Hole Roundness ≤5 µm                                     ≤2 µm
Positional Tolerance ±0.02 mm                          ±0.010 mm
Burr Height ≤10 µm <5 µm
Magnetic Shielding Integrity No degradation     Fully preserved
Profile Tolerance (Wire EDM) ±0.02 mm            ±0.01 mm
Scrap Rate <5%                                                 <2%
First-Pass Yield ≥95%                                         98%
Annealing Requirement Avoid if possible            Not required
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6. Client Feedback & Product Impact
“Qualitetch delivered exactly what we needed. Every other process caused heat damage or distortion—this hybrid method hit every tolerance and kept the shielding performance fully intact.”
— Lead Mechanical Engineer,
“We saw measurable improvements in audio clarity during system tests. Cleaner transients, less hum, and no mechanical tuning issues during assembly.”
— QA Lead
Product Benefits:
• Improved acoustic performance in enclosures
• Reduced EMI noise floor in phono and analog stages
• Faster assembly times due to perfect mechanical fit
• Higher first-pass QC acceptance rates
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7. Lessons Learned
1. Micro-drilling outperforms thermal and etching methods for hole sizes ~0.65 mm with asymmetric tolerances
2. Wire EDM is ideal for precision profiling of heat-sensitive metals like mu-metal
3. Cold machining avoids heat-affected zones that degrade magnetic properties
4. Real-time QC and adaptive tool monitoring significantly reduce defects
5. Hybrid processes, when sequenced correctly, can outperform single-step production for complex components
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Conclusion
Through a combination of CNC micro-drilling and wire EDM profiling, Qualitetch Components delivered a repeatable, scalable manufacturing solution for a technically demanding mu-metal component.
This solution enabled a world-class audio manufacturer to overcome tight tolerance, material sensitivity, and performance integration issues—delivering better sound, improved shielding, and higher production efficiency.

chemical etching of component