Micro Machining Titanium: EDM, CNC and Precision Manufacturing Methods

Executive summary: Micro machining of titanium — producing features with dimensions below 0.5 mm — requires process selection based on feature geometry, aspect ratio, and surface integrity requirements rather than on material removal rate alone. CNC micro milling with carbide end mills as small as 0.1 mm diameter can produce three-dimensional micro features with surface finishes below Ra 0.4 µm, but tool deflection and breakage risk limit the achievable aspect ratio to approximately 3 to 1. Micro EDM, both wire and sinker, can produce features with aspect ratios above 10 to 1 and internal corners below 0.05 mm radius, but the surface recast layer becomes a larger fraction of the feature size. For medical implant features, microfluidic channels, and aerospace sensor components where titanium is specified for biocompatibility or corrosion resistance, the practical limit of each process must be understood before committing to a manufacturing method, because micro-scale titanium machining behaves differently from macro-scale machining in ways that are not always obvious from standard machining guidelines.

CNC micro milling of titanium: capabilities and limitations

CNC micro milling of titanium uses carbide end mills with diameters from 0.1 mm to 0.5 mm to produce slots, pockets, and three-dimensional micro features. The process works well for features with aspect ratios up to 3 to 1 — a 0.2 mm diameter end mill can reliably cut a slot 0.6 mm deep. Beyond this aspect ratio, tool deflection becomes significant, and the risk of tool breakage increases sharply. The practical depth limit for a given tool diameter is determined not by the machine capability but by the column strength of the end mill under cutting load.

The cutting parameters for micro milling titanium differ substantially from macro-scale parameters. Cutting speeds are higher in terms of spindle RPM — typically 30,000 to 60,000 RPM — but the actual cutting speed at the tool periphery is low because of the small diameter. A 0.2 mm end mill at 40,000 RPM has a cutting speed of only 25 m/min, which is at the lower end of the recommended range for Ti-6Al-4V. Feed rates must be scaled to maintain chip loads at the micron level. A typical feed per tooth for micro milling titanium is 2 to 8 µm, compared to 30 to 80 µm for conventional diameter end mills.

The practical production reality is that micro milling of titanium is slower and more process-sensitive than micro milling of aluminium or brass. Tool life is shorter — a 0.2 mm carbide end mill may machine 100 to 300 mm of cut length in titanium before the edge degrades measurably, compared to several metres in aluminium. Tool wear monitoring becomes critical because a worn micro tool produces oversized features and burred edges before it breaks. In-process probing or optical measurement after each tool change is often necessary to maintain dimensional control.

Burr formation is a persistent problem in micro milling of titanium. The burr size, typically 10 to 50 µm, can exceed the feature tolerance for micro-scale parts. Deburring of micro features is difficult because standard deburring tools are larger than the features themselves. Electrochemical deburring or abrasive flow machining are sometimes used for titanium micro parts, but these processes add cost and cycle time. In many cases, the design must accommodate the expected burr rather than attempting to remove it entirely.

Micro EDM for high-aspect-ratio titanium features

Micro EDM addresses the aspect ratio limitation of micro milling. Small-diameter electrodes, typically 0.05 to 0.3 mm, can produce holes and cavities with depth-to-diameter ratios of 10 to 1 or higher because there is no cutting force to cause deflection. A 0.1 mm diameter electrode can drill a hole 1.5 mm deep in titanium, which would be impossible with a CNC end mill of the same diameter because the tool would break from cutting force.

Micro wire EDM, using wire diameters of 0.02 to 0.10 mm, cuts through-thickness micro contours with corner radii down to the wire radius. A 0.05 mm wire can produce an internal corner radius of 0.05 mm, which is smaller than any standard end mill. The surface finish after multiple skim cuts on micro wire EDM is typically Ra 0.6 to 1.2 µm, comparable to micro milling for many applications.

The limitation of micro EDM is the recast layer. At the microscale, the recast layer thickness of 2 to 15 µm represents a larger fraction of the feature size than in macro-scale EDM. For a 0.5 mm diameter micro hole, a 10 µm recast layer reduces the effective diameter by 4 percent. For fatigue-loaded micro features, the recast layer is a larger concern because the ratio of surface area to volume is higher and any surface defect has a greater effect on fatigue life.

Electrode wear in micro EDM is also more significant. The electrode wears during erosion, and at the microscale, the worn volume represents a larger fraction of the electrode geometry. Electrode compensation strategies — where the machine automatically adjusts the electrode position to account for measured wear — are essential for maintaining dimensional accuracy in micro EDM of titanium.

Process selection for micro titanium features

The choice between micro CNC and micro EDM for a titanium component depends on the feature geometry, the required surface integrity, and the production quantity. The following decision logic is used in production planning for micro titanium parts.

For micro features with aspect ratios below 3 to 1 and accessible geometry, CNC micro milling is the preferred process. It produces a recast-free surface, achieves the best surface finish, and has the highest material removal rate among micro machining methods. This includes micro slots, shallow pockets, and three-dimensional micro contours on accessible surfaces.

For micro holes and cavities with aspect ratios above 5 to 1, micro EDM is the only practical option. Micro drilling by EDM produces holes that cannot be produced by any mechanical drilling or milling method at this scale. The surface recast layer must be accepted or removed by secondary processing such as electrochemical polishing if the fatigue requirement demands it.

For micro features that require both precision and fatigue integrity — such as micro holes in titanium medical implants or aerospace sensor components — a hybrid approach is common. Micro EDM drills the hole or cuts the contour, and a subsequent electrochemical or abrasive finishing step removes the recast layer. The additional finishing step adds cost but is necessary when the service load requires high fatigue resistance at the microscale.

For very small quantities — one to twenty prototype or development parts — laser micro machining is sometimes used for titanium micro features. Laser cutting produces no cutting force and can achieve fine features, but the thermal affected zone at the cut edge presents similar surface integrity concerns as EDM. For production quantities above fifty parts, micro EDM and micro CNC are generally more economical than laser processing because the faster cycle time and lower per-part cost offset the initial programming and setup investment.

Inspection challenges for micro-machined titanium features

Inspection of micro features in titanium components presents challenges that differ from macro-scale inspection. Optical measurement systems with magnifications of 50× to 200× are typically required for features below 0.5 mm. The reflective surface of titanium can cause glare and measurement variation unless the lighting and measurement angle are controlled. Contact probing is not practical for features below 0.3 mm because the probe tip diameter is larger than the feature.

The inspection bottleneck in micro titanium production is often not the machining cycle but the measurement cycle. A component with twenty micro features may require 20 to 40 minutes of optical measurement time, depending on the feature density and the measurement system capability. This inspection time affects production scheduling and cost. For procurement teams evaluating micro titanium component quotes, the inspection time is a real cost driver that should be visible in the quotation breakdown.

Surface roughness measurement of micro features is also constrained by the feature size. A stylus profilometer requires a minimum surface length for a valid measurement, typically 0.5 to 1.0 mm. Micro features smaller than this cannot be measured by contact profilometry. Optical surface measurement methods such as confocal microscopy or white light interferometry are required, and these methods are sensitive to titanium surface reflectivity and local geometry variation.

For design engineers and procurement teams planning micro-machined titanium components, early consultation on feature geometry, inspection method, and acceptance criteria is more important than for macro-scale parts because the manufacturing and inspection constraints at the microscale are more restrictive and less widely understood. Submit your micro titanium component drawing through the engineering RFQ portal for a process-specific assessment. The titanium CNC machining services page provides capability details for conventional and micro-scale CNC work, and the wire EDM machining page covers micro EDM capabilities.