Manufacturing of human knee by cryogenic machining: Walking towards cleaner processes

Abstract Nowadays, medical manufacturing sector has to deal not only with economic and environmental issues but also with providing cleaner processes in comparison with other sectors such as aeronautical or automotive. In case of prosthesis manufacturing, this issue is critical due to afterwards they are introduced inside human bodies and it is needed avoiding pathogenic transmission related with dirty coming from oil emulsions used to assist machining processes. It should be noted that in Spain the rejection cases are stablished in 350-450 times only in knee and hip substitutions. Besides, the use of oil emulsions supposes expenses from 17% to 30% of the part cost and its disposal is not efficient at 100% due to almost 8% of oil emulsions are lost as leakages. Therefore, it is needed suppress its use to reduce the number of prosthesis rejections, economic expenses and environmental footprint. In line with this, CO2 cryogenic machining is presented as ECO2 coolant (ecological+economic) and is used as cleaner fluid in other sectors. Then, the joining of these two features to medical manufacturing sector can open a new line of researching in which obtain clean workpieces without the needed of subsequent aggressive cleaning processes. Consequently, in this work a knee manufacturing processes with CO2 cryogenic machining is presented in order to evaluate the suitableness of this technology in this type of components.