Modeling cutting edge geometry for plane and curved needle tips

Hollow needles are commonly used in many areas of medicine, yet there has been limited research on needle tip geometry. A better understanding of needle tip geometry can lead to the creation of an optimized needle tip geometry design which would greatly benefit the procedure of biopsy, where a needle is used to cut and remove tissue from the body. The present research develops mathematical models to calculate the inclination and rake angle along the cutting edges of needle tips generated by curved surfaces. The parameters of needle insertion length and inner needle tip surface area are also examined. Needle insertion force is predicted based on needle geometry and calculated for curved and flat plane tip needles. A concave needle produced lower cutting forces than the convex and bias bevel needles. It is found that utilizing curved surface needle tip geometry, as opposed to flat plane geometry, allows for greater control in varying rake and inclination angles on the needle. This greater flexibility allows for more control in designing an optimized needle tip.