An image-based methodology to establish correlations between porosity and cutting force in micromilling of porous titanium foams

Porous titanium foam is now a standard material for various dental and orthopedic applications due to its light weight, high strength, and full biocompatibility properties. In practical biomedical applications, outer surface geometry and porosity topology significantly influence the adherence between implant and neighboring bone. New microfabrication technologies, such as micromilling and laser micromachining opened new technological possibilities for shape generation of this class of products. Besides typical geometric alterations, these manufacturing techniques enable a better control of the surface roughness that in turn affects to a large extent the friction between implant and surrounding bone tissue. This paper proposes an image analysis approach for optical investigation of the porosity that is tailored to the specifics of micromilling process, with emphasis on cutting force monitoring. According to this method, the area of porous material removed during micromilling operation is estimated from optical images of the micromachined surface, and then the percentage of solid material cut is calculated for each tool revolution. The employment of the aforementioned methodology in micromilling of the porous titanium foams revealed reasonable statistical correlations between porosity and cutting forces, especially when they were characterized by low-frequency variations. The developed procedure unlocks new opportunities in optimization of the implant surface micro-geometry, to be characterized by an increased roughness with minimal porosity closures in an attempt to maximize implant fixation through an appropriate level of bone ingrowth.Peer reviewed: YesNRC publication: Ye

Analysis of the process parameters affecting the bone burring process: An in-vitro porcine study

© 2019 John Wiley & Sons, Ltd. Background: A stable bone burring process, which avoids thermal osteonecrosis and minimizes harmful vibrations, is important for certain orthopedic surgical procedures, and especially relevant to robot-operated bone burring systems. Methods: An experimental characterization of the effects of several bone burring process parameters was performed. Burring parameters were evaluated by resultant bone temperature, tool vibration, and burring force. Results: An optimal combination of bone burring parameters produced minimums in both bone temperature (\u3c40°C) and tool vibration (\u3c4 g-rms). A cylindrical burr, oriented normal to the specimen, resulted in significantly higher temperatures (50.8 ± 6.8°C) compared with a spherical burr (33.5 ± 4.3°C) (P =.008). Regardless of the parameters tested, burring forces were less than 10 N. Conclusions: The recommended configuration, which minimized both bone temperature and vibrations experimentally, was a 6-mm spherical burr at 15 000 rpm with a 2 mm/s feed rate

Experimental analysis of the process parameters affecting bone burring operations

© 2017, © IMechE 2017. The experimental quantification of the process parameters associated with bone burring represents a desirable outcome both from the perspective of an optimized surgical procedure as well as that of a future implementation into the design of closed-loop controllers used in robot-assisted bone removal operations. Along these lines, the present study presents an experimental investigation of the effects that tool type, rotational speed of the tool, depth of cut, feed rate, cutting track overlap, and tool angle (to a total of 864 total unique combinations) have on bone temperature, tool vibration, and cutting forces associated with superficial bone removal operations. The experimental apparatus developed for this purpose allowed a concurrent measurement of bone temperature, tool vibration, and cutting forces as a function of various process parameter combinations. A fully balanced experimental design involving burring trials performed on a sawbone analog was carried out to establish process trends and subsets leading to local maximums and minimums in temperature and vibration were further investigated. Among the parameters tested, a spherical burr of 6 mm turning at 15,000 r/min and advancing at 2 mm/s with a 50% overlap between adjacent tool paths was found to yield both low temperatures at the bone/tool interface and minimal vibrations. This optimal set of parameters enables a versatile engagement between tool and bone without sacrificing the optimal process outcomes