Drill Bit Characterization with 3D Optical Microscope

Bruker’s NPFLEX 3D Optical Microscope is being used by a major hand and electric tool company in its drill bit production for product quality control and R&D purposes.

It is well known within the industry that the surface roughness of critical tool surfaces influences the ultimate effectiveness of the tool. The company was seeking a solution capable of measuring the surface roughness conveniently, quantitatively, and repeatedly.

The Challenge

Previously, the company had used 3D stereo microscopes to image the drill bits at differing angles, performing a simple image analysis to find metal burrs and damage caused to the drill bits.

This approach was very user-dependent, being susceptible to subjective user analysis and varied component positioning. Surface roughness and its influence on the quality of the production grade product remained ambiguous.

Moreover, the company was finding it difficult to compare new data with previous measurements because of these variables and lack of gauge capability. Positioning larger samples or capturing images of drill bits from an end-on perspective is a challenge with smaller optical microscopes.

Bruker’s Solution

Figure 1. NPFLEX 3D Optical Microscope.

Bruker’s NPFLEX 3D Optical Microscope addresses this problem with a large gantry that can hold a 1 foot cubed component weighing up to 150lbs (Figure 1). This system allows convenient component loading and manipulation.

With optimized long working distance objectives, the NPFLEX enables focusing the component being imaged at a distance of 33mm from the objective (Figure 2). This facilitates imaging of components with complex geometries.

Figure 2. Drill bit.

The combination of the long working distance and a crash mitigation device provides a large margin of error and avoids crashing of the objective, thus making the NPFLEX operator friendly.

With these features, the NPFLEX can make repeatable multiple measurements on several drill bits from even end-on angles. Metric surface dimensional data was delivered easily into standard reports (Figures 3 and 4). This provided the company a metric measurement capability that is objective and can be compared through time.

Figure 3. New drill bit off production line.

The NPFLEX minimizes the issue of user dependence, thereby allowing the manufacturer to concentrate on its metrology issues instead of the metrology process.

They configured a testing regime to determine parameters to ascertain production was within specified parameters.

Figure 4. Same drill bit post drilling sequence tribology test.

Analysis with NPFLEX 3D Optical Microscope

The NPFLEX enabled the R&D group of the tooling manufacturer to use the instrument for comprehensive material and tribology analysis.

Studies were performed on high-speed steel drill bits for drilling anodized aluminum plates. Data was acquired from three distinct regions of the drill bits (Figure 5).

Figure 5. Image showing points of data collection (head, forward surface, and inside surface) from various drill bits.

From the results, no change was observed in the radii of curvature and edge quality, but the bearing ratios and Str parameter changed after certain usage amounts (Figure 6). This showed that although the use of drill bits usage smoothed the surface initially (Figures 3 and 4), their prolonged usage caused reduced smoothing.

The images acquired illustrated the re-deposition of significant material upon prolonged test periods (Figure 6). The prolonged usage displaced the drill bit material, resulting in the roughening of the surface.

Figure 6. Surface texture analysis of drill bits with increasing usage.

Furthermore, a cross-material analysis was conducted on several drill bits differing in either materials or coatings before and after usage. The drill bits used were High Speed Steel (HSS), Titanium CarboNitride (TiCN), Titanium Nitrite (TiN) coated drill bit, and Silicon Carbide nano-composite drill bit.

The post usage results acquired for these bits are illustrated in Figure 7, showing that the Silicone Carbide composite drill bit experienced the minimum level of material re-deposition after usage.

Figure 7. Cross-material characterization of drill bits post-tribology testing.

Conclusion

The convenient and user-friendliness of the NPFLEX 3D Optical Microscope in conjunction with critical measurement capabilities facilitated this large tool manufacturer to analyze drill bit performance, improve tool quality economically, and increase its speed to market.

This information has been sourced, reviewed and adapted from materials provided by Bruker Nano Surfaces.

For more information on this source, please visit Bruker Nano Surfaces.