Hi,

I am trying to simulate the drilling process of Aluminium material using Abaqus, I am having a problem in getting reasonable cutting force diagrams Fz vs time or thickness, I keep getting zero or below zero force values every time an elements layer is being deleted from the material, the normal situation would be having a constant cutting force though the workpiece thickness till the cutting tool exits the workpiece, however as you can see from my images, the cutting force values keep fluctuating with every element layer, from my understanding it seems that because an element layer is deleted my cutting tool for a short instance of time is drilling air/empty space which I believe is causing the zero/very low cutting force results, I tried changing many parameters but nothing seems to fix my problem, the image in blue color is for one layer of elements only, as you can see initially everything seems to be going well but at some point when the element is losing stiffness and getting degraded the cutting force starts fluctuating very much,

any suggestions on how to fix this problem? 

Thank you very much :-)