CNC Machining Case Studies

This page presents real-world CNC machining projects completed by Emitech for medical, automotive, and electronics customers. Each case study explains the customer's challenge, the material and process solution we applied, and the measurable results achieved. Use these examples to evaluate how our CNC milling and CNC turning capabilities can support your next precision metal part program.

Case Study 1: Miniature Stainless Steel Housing for a Medical Endoscope

Miniature 316L stainless steel housing for a handheld medical endoscope — Medical Device Industry. The customer, a medical device OEM based in Europe, needed a thin-wall metal housing that protected delicate optics while surviving repeated autoclave sterilization cycles. The program started as a development project for a next-generation handheld endoscope and was expected to move quickly from clinical validation into low-rate initial production.

Customer challenge

The original design called for a cylindrical housing with wall thickness down to 0.3 mm, multiple internal channels for cable routing, and a sealed front flange that interfaced with a polymer lens barrel. Tolerance requirements were tight: critical bores had to hold ±0.02 mm, and the internal surface needed Ra 0.4 μm or better to allow cleaning and sterilization without bacterial retention. The part geometry was not suitable for casting or forging due to the thin walls and internal features, so machining from solid bar stock was the only practical route.

Beyond geometry, the customer faced three commercial constraints. First, they needed a first-article batch of 50 units within two weeks to keep a regulatory filing on schedule. Second, every lot required full material certification, passivation validation, and a dimensional report traceable to the raw material heat number. Third, because the device was Class IIa under MDR, any process change would trigger re-validation, so the manufacturing route had to be stable from first article through production.

Emitech solution

Our engineering team selected 316L stainless steel for its corrosion resistance, biocompatibility, and stable machinability in the austenitic condition. We used a 5-axis CNC milling center to machine the housing from solid bar in a single fixture, reducing stack-up error from multiple setups. A custom vacuum fixture held the thin-wall part without deformation during finishing passes. Toolpaths were optimized with low radial engagement and through-tool coolant to minimize heat and deflection on the 0.3 mm walls.

Process planning followed a three-stage approach: roughing removed 85 percent of the stock at high feed rates, semi-finishing left 0.05 mm stock on critical surfaces, and finishing used diamond-coated end mills at controlled spindle speeds to achieve the Ra 0.4 μm internal finish. Threaded features and the front flange seal groove were machined in the same setup to maintain concentricity. After machining, parts were deburred under microscope inspection, passivated per ASTM A967, and inspected on a CMM. Surface roughness was verified with a profilometer, and dimensional reports were included with each first-article shipment.

For customers who combine metal injection molding with machining, this same housing concept can be produced as a near-net MIM blank with final CNC finishing to reduce material waste and unit cost at volumes above 10,000 pieces per month. Our MIM CNC secondary operations team handles these hybrid programs with dedicated fixtures that protect as-sintered surfaces during final machining.

Results — representative project

• Critical bore tolerance: ±0.02 mm
• Internal surface finish: Ra 0.4 μm
• Minimum wall thickness: 0.3 mm
• First-article lead time: 2 weeks
• Production volume: 5,000 pieces per month
• Inspection: CMM dimensional report + surface roughness certificate
• First-pass yield in production: 98.5%
• Passivation compliance: ASTM A967, citric acid based

Case Study 2: Precision Aluminum Sensor Bracket for Automotive Assembly

6061-T6 aluminum sensor bracket for ADAS module mounting — Automotive Industry. A Tier-2 automotive supplier serving a major OEM needed a lightweight, high-volume bracket that could be mounted directly to a chassis rail without secondary adjustment. The bracket was part of an advanced driver-assistance system module and had to maintain sensor alignment over the vehicle lifetime.

Customer challenge

The bracket combined thin ribs, threaded mounting holes, and a contoured base that had to mate flush against a cast aluminum housing. The customer required ±0.05 mm positional tolerance on the two M6 threaded holes and a stable supply of 50,000 pieces per month. Delivery had to align with a just-in-time assembly schedule, with shipments released weekly against a rolling 13-week forecast. Any dimensional drift would cause assembly line stoppages, so consistent first-pass yield was more important than the lowest possible unit price.

Surface finish and corrosion resistance were also specified. The bracket needed Ra 0.8 μm on the mounting face to ensure repeatable bolt preload, and a clear anodized finish to survive salt spray testing per OEM specification. Lot traceability was mandatory: every box had to link back to the raw material certificate, machine operator, and inspection record. Finally, the supplier was required to maintain six months of production capacity in reserve tooling to avoid disruption during demand spikes.

Emitech solution

We selected 6061-T6 aluminum for its strength-to-weight ratio, stable machinability, and excellent response to Type II anodizing. Production was split across 3-axis roughing machines and 4-axis CNC mills for the contoured base and angled holes, allowing each operation to run on the most efficient equipment. Roughing removed material in high-speed adaptive toolpaths, while 4-axis finishing completed the angled mounting face and threaded holes in a single setup.

Process control was built around tool-life management and in-process inspection. All cutting tools were tracked by tool-life counters and replaced at 80 percent of predicted wear to avoid unexpected breakage. In-process inspection was performed every two hours using bore gauges, height stands, and a shop-floor CMM on five critical dimensions. SPC data was recorded for hole position, bracket height, and thread depth. After machining, brackets received a clear Type II anodize finish through one of our certified finishing partners, providing corrosion protection without changing critical dimensions. Full lot traceability was maintained from raw material certificate to final shipment.

For programs that start with MIM or powder metallurgy, we can supply comparable bracket geometry through automotive MIM parts when volumes and shapes justify the tooling investment. If additional corrosion protection is required, we can also coordinate surface treatment options such as chromate conversion or powder coating.

Results — representative project

• Positional tolerance on threaded holes: ±0.05 mm
• Monthly production volume: 50,000 pieces
• Standard lead time: 3 weeks
• First-pass yield: 99.2%
• Surface finish: Ra 0.8 μm, clear anodized
• Inspection: First article report + in-process SPC data
• Lot traceability: Material certificate to shipment
• Reserve tooling capacity: 6 months

Case Study 3: Hybrid MIM + CNC Hermetic Connector Body for Aerospace Electronics

Kovar electronic package with hermetic connector pins — Aerospace & Electronics Industry. A defense subcontractor needed a miniature metal shell that could be sealed around glass-sealed connector pins and survive thermal cycling from −55 °C to +125 °C without leakage. The geometry included internal threads, a precision shoulder, and a flat sealing face that could not be produced economically by machining alone.

Customer challenge

The connector body was originally designed as a fully machined part from Kovar bar stock. While machining achieved the required tolerances, material utilization was below 15 percent and cycle time was long due to the internal threads and thin walls. At a projected annual volume of 120,000 units, the customer needed a process that could hold ±0.03 mm on the sealing face and thread pitch while reducing unit cost by at least 30 percent.

The part also had to meet hermeticity requirements of 1 × 10⁻⁸ atm·cc/s helium leak rate after nickel and gold plating. This meant the base material could not contain internal porosity that would open during plating or thermal cycling. Any secondary machining operation had to preserve the sintered density in sealing areas while removing allowance from functional surfaces.

Emitech solution

We proposed a hybrid route starting with metal injection molding to produce a near-net Kovar blank, followed by CNC finishing on critical surfaces. The MIM feedstock was formulated with gas-atomized Kovar powder and a wax-polymer binder system optimized for thin sections. After injection molding, blanks were debound in a solvent and thermal two-stage process, then sintered in a hydrogen atmosphere to reach 97.5 percent theoretical density.

The sintered blanks were then transferred to MIM CNC secondary operations. We machined the sealing face, internal threads, and shoulder in a single 4-axis fixture using carbide inserts at low depths of cut to avoid pull-out of hard particles. Each part was inspected for density using the Archimedes method, and a sample from each lot was cross-sectioned and examined for porosity. After machining, parts received electrolytic nickel under gold plating through an approved aerospace plating line. Final hermeticity testing confirmed leak rates below the specified limit.

Results — representative project

• Sealing face tolerance: ±0.03 mm
• Sintered density: ≥ 97.5% theoretical
• Material utilization improvement: from 15% to 78%
• Unit cost reduction: 34%
• Hermeticity: ≤ 1 × 10⁻⁸ atm·cc/s
• Annual volume: 120,000 pieces
• Plating: Nickel + gold per MIL-G-45204
• Lot verification: Density, cross-section, and helium leak test

Project Summary Table

Attribute	Medical 316L Housing	Automotive 6061-T6 Bracket	Hybrid MIM + CNC Connector
Industry	Medical devices	Automotive	Aerospace electronics
Material	316L stainless steel	6061-T6 aluminum	Kovar
Process	5-axis CNC milling	3-axis + 4-axis CNC milling	MIM + 4-axis CNC finishing
Key tolerance	±0.02 mm	±0.05 mm	±0.03 mm
Surface finish	Ra 0.4 μm, passivated	Ra 0.8 μm, clear anodized	Nickel + gold plated
Production volume	5,000 pcs/month	50,000 pcs/month	120,000 pcs/year
Lead time	2 weeks (first article)	3 weeks	4 weeks (pilot)

Note: The data above are representative of typical Emitech projects. Exact results depend on part geometry, material, and quantity. All quality inspection reports are available on request.

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