Analysis Of Skull Milling Process With Variable Thickness And Establishment Of Constant Milling Force Prediction Model

The craniotomy is one of the largest operations in neurosurgery,and bone milling is a very important operation in craniotomy.Compared with ordinary milling,milling the biggest difference is that the axial craniotomy milling depth is equal to the thickness of the skull,but the larger the thickness of the skull and uneven,so in the milling process craniotomy to milling depth is changing along with the change of the thickness of the skull,is a variable thickness milling process,resulting in the milling force and milling temperature changing.Excessive milling force and mutation are easy to cause a bone crack and cutter fracture,and high milling temperature is easy to cause thermal necrosis of bone cells.In this paper,by studying the relationship between milling force and milling temperature and milling parameters(spindle speed,feed rate)and bone thickness,a constant milling force prediction model is established to control the milling force and milling temperature in a reasonable range,which is necessary to ensure the safety of the operation and reduce The patient recovery time is of great significance.The main research contents of this paper are as follows:(1)In view of the characteristic that the depth of axial milling is equal to the thickness of skull in craniotomy,the micro-element cutting force of the maximum cutting thickness of each tooth in the cutter-workpiece contact area was calculated by using classical cutting theory and cutting energy method.The theoretical model of milling force on milling parameters(spindle speed,feed speed)and bone thickness was established,and the relationship between milling force and milling parameters(spindle speed,feed speed)and bone thickness was analyzed by simulation with MATLAB software.The feasibility of prediction and control of milling force is verified theoretically.(2)A bone milling test platform was built to study the influence of spindle speed,feed rate and coolant on milling force and milling temperature through cortical bone milling test,and the results were compared with the theoretical model analysis results of milling force.Scanning electron microscope(SEM)was used to observe the bone surface morphology after milling.The effect of milling force on the bone surface crack was studied by observing the bone surface morphology.(3)Established and verified a three-dimensional bone milling finite element model based on ABAQUS.The validated finite element model was used to study the influence of cortical bone thickness on milling force,and the results were compared with the analysis results of the milling force theoretical model.(4)Design a full factor test,use the finite element model to simulate the test data,analyze the test results with gray correlation,and determine the influence of milling parameters(spindle speed,feed rate)and cortical bone thickness on the milling force.Established and verified the milling force prediction model based on artificial neural network,which provides a basis for the craniotomy robot to adjust the milling parameters(spindle speed,feed rate)in real time during the process of skull variable thickness milling,and to keep the milling force constant.