Geometrical Reconstruction and CNC Process of Spurious Tympanic Membrane Based on Reverse Engineerin

Geometrical Reconstruction and CNC Process of Spurious TympanicMembrane Based on Reverse EngineeringLU Hong' PENG Jun' ZHOU Yongqing( 1. School of Mechanical and Elcrical Engineering , Wuhan University of Technology , Wuhan 430070 , China ,E mail 1andzh@ mail. whut. edu. cn 2. Bethune International Peace Hospital of PLA , Shijiazhuang 050082 , China )and restore audition by restoring or replacing the tympanic membrane. So，whether you can make the spurious tym panic membranesucessfilly is one of the keys to a sccessfsul operation . Utilizing CMM( Coordinate Measuring Machine ) measurement equipment.we measured tympanic membrane model precisely and digitally. We also analysed the measured data by point to surface and wehave sccessfully reconstructed the CAD model of the spurious tympanic membrane. Using the model we have got , we schemed outthe mold of spurious tympanic membrane. In addition , we utilized MasterCAM compiling CNC( Computerized Numerical Control ) codle and simulating the course of working . Ultimately ，we obtained the mold of spurious tympanic membrane. Our researchin this article has great significance to the success of spurious tympanic membrane grafting operation .Key words: reverse engineering ; spurious tympanic membrane ; geometrical reconstruction ; CNC process1 IntroductionPerforation of tympanic membrane which caused by accident or tympanitis is one of the main reasons fonboth deafness and dyssaudia. We could improve and restore audition by restoring or replacing the tympanic mem-brane. Spurious tympanic membrane which is substitute to tympanic membrane is bionic tympanic membrane.Spurious tympanic membrane substitute tympanic membrane fixing to tympanic groove. The vibration of spuri-ous tympanic membrane caused by acoustic vibration came from external auditory canal. Through ossicularchain' s acoustic mechanism，acoustical vibration drove mallet shaking incus , further transferred vibrancy kineticenergy to inner ear.In the field of tympanic membrane restoration , so far , internationally investigative emphasis right throughthe renewal of spurious tympanic membrane. In physical design and figuration of spurious tympanic membrane ,they proceed broad scale research in finding the best membrane thickness 1-5 J and measuring primary data°l. Atpresent , spurious tympanic membrane reparation success or not is in a great measure rest with doctor' s level andexternal environment. The conclusion of the authority is that sound propagation characteristic mostly affected byspurious tympanic membrane reorganization when we took the same spurious tympanic membrane material andthe operation should take spurious tympanic membrane' s mechanical stability and sound transmission character-istic for gist 77. Just depend on change stuff is difficult of realize performance requirement. Aiming at the actual-ity that the escalation of spurious tympanic membrane shape functional requirement , more and more theoreticaland practical research were taken on the tenacity and intensity of spurious tympanic membrane material. There-into the typical technology is that adopt chemical treatment to improve stability of membrane successfully , whichformed a new operation metho 81.The shape of tympanic membrane surface is unique and complicated , and it is difficulted to scheme out thesurface by yourself. Utilizing reverse engineering technique ，based on anatomical original shape of tympanicmembrane , we measured tympanic membrane model precisely and digitally , then we obtained point cloud datadirectly. We transformed the file format , input the date to homologous software and reconstructed the CAD 3D-model of tympanic membrane with C2 continuity based on NURBS. Then we scheme out the mold of spurioustympanic membrane. We used MasterCAM establishing rational process route , creating CNC code and finally weworked out the mold of spurious tympanic membrane.中国煤化工2 Geometric Reconstruction of Spurious TynYHCNMHG2.1 Surface Data Acquisition and Data ProcessingDigitalization of CAD model is the most pivotal one-step in reverse engineering technology. Only have weobtained correct measured data , we can process error analysis and surface comparison , then CAD modeling andsurface reconstruction. In reverse engineering , obtaining surface spatial data method basically divided in two cat-- 59egories : touched type and non- touched type. Touched type measurement primarily utilize three coordinates mea-suring machine obtaining three dimensional coordinate information by the contact between probe and body sur-face ; non-touched type measurement primarily utilize some kind of body surface interactive physical phenomenonsuch as sound , light , electromagnetism etc obtaining three dimensional coordinate information. Optical principleis the most widely used in non- touched type measurement such as laser trigonometry and structured light methodetd9].In consideration of the model of tympanic membrane is too small and the requirement of the accuracy ofmeasurement is too high , so in order to collect the data of the model of tympanic membrane more accurately ,wetook the measurements using HXY-1200 type three coordinate measuring machine. Its accuracy of measurementis 0.001 mm. Because CMM measurement measured point by point ,it do not like the non- touched type mea-surement equipment such as laser scanning instrument can collect large scale data point on the surface quite thickand fast. So before we measured spurious tympanic membrane , we should mark out the measure path of the sur-face reasonable，that the data we collected can be post-disposed reasonable and convenient. Therefore , in orderto obtaining exhaustive measured data of the surface , we adjusted measure step to 2 mm , that we can collect thedata point as dense as possible. Spurious tympanic membrane is monotype class surface , so we can finish the dataacquisition with one time orient and avoid the error caused by multiple bearing and multiple view syntheses. Thepoint data we measured is shown in Fig. 1. Because the data point is not large , this article adopted man comput-er interaction method deleting overt bad points though graphic display."xFig.1 The data point of the mold of tympanic membrane2.2 Tridimensional Reconstruction of the Spurious Tympanic MembraneThe typic surface modeling methods included coons curved surface method , Bezier curved surface method ,B-spline curved surface method and NURBS curved surface method. There are also many methods in surface fitting such as Multiquadric method，lamella spline method , finite element method , partial differential equationmethod , minimum energy method , nonuniform rational B- spline method etc. In these matching function , onlyNURBS curved surface method possesses hereinafter characteristics : polynomial expression ; with local control a-bility ; guarantee computational accuracy ; geometrical property undistorted ; be able to expression different kindsof curves and surfaces. Because it has C continuity and could educe the two exponent partial derivative of arbi-trary point that could made inhere geometric graph do not lose internal characteristics ，so we choose NURBSproceeding tridimensional reconstruction of the spurious tympanic membraneThere are three representation of a sheet of times NURBS curved surface which control peak isd; (0≤i≤n 0≤j≤m ): rational fraction representation ; rational primary function representation ; homogeneous coordi-nates representatiort 11]1 ) rational fraction representation之之。d;jN;s( u )N;(v)μun)=西(1 ). i=0 j=0w; ,N;A( u)N;(v)Thereinto ,control peak d; i=0 .. ,m ij=0 .. m presented topology rectangular array , and formed acontrolled grid. w; ; is weighting factor which in association with control peak d; ，. It is prescribed that theweighting factor which located in foursquare peak section is中国煤化工。,00m ,wmm>0 , therest w; j≥0.MHCNMH G .N;k ,i=0.. m and O;(v)ij=0.. m are u direction R tumes ana V Gdirection l times norm B- splineprimary function which are decided by node vector U=[ u0 ,0 r.. rm+k+1 ]and V=[ v0山1 .. /心n+l+1 ]ac-cording to de Boor-Cox recursion formula.2 ) rational primary function representation.一593一Ku山)=ggdl; ,R;kj(u心)(2)i=0 i=0Thereinto ,R; k;( u儿)is bivariant rational primary functionw;jN;( u )N;(v)R;kj(u u)=(3)22o, ,N,;(u)N,()-元=3 ) homogeneous coordinates representationP(u ,心)= H{P(u ,r)}= H{ZZD,jN;(u)N,(v)}(4)i=0 j=0Thereinto ,D; ;=[ w; jd; ,;j ] went by the name of control peak d; ;' s weight brought control peak orhomogeneous coordinates. In this way , weight brought control peak defined a tensor product not rational B-spline surface P( u山)in a higher dimension space. H{} represent central projection transform , and proectioncenter is the the origin of homogeneous coordinates. P( u儿)define a sheet of nurbs surface on the projection ofw= 1 hyperplane. We can obtain the figure of spurious tympanic membrane shown in Fig. 2 by interpolation andfitting NURBS surface.3 CNC Process of the Spurious Tympanic Membrane' s Mold3.1 Creation of the Spurious Tympanic Membrane' s MoldWe have restructured the point data above and have obtained the figure of spurious tympanic membrane.What we really want is the mold of spurious tympanic membrane , which can be used in the operation of tympan-ic membrane grafting. In the design of the mold , we proceed completely according to medically operative re-quirement. We put the model of spurious tympanic membrane in CATIA , and based on the moulding surfaceshape of spurious tympanic membrane , we designed the mold of spurious tympanic membrane inversely. We de-fined the boundary line of mold cross sectional shape as section line , and defined one of the axial direction bound-ary line as edge of regression , another as derivation strung , and finally defined the boundary line of the model ofspurious tympanic membrane as reference section line. At last , the side of the mold is completed with C conti-nuity which guaranteed the integrity of the design and the accuracy requirement of CNC process as well. Themold of spurious tympanic membrane is shown in Fig. 3.Fig.2 The spurious tympanic membraneFig.3 The mold of spuriouisfigure of fttingtympanie membraneFig.4 The CNC process of the mold3.2 The CNC Process of the Mold of Spurious Tympanic MembraneWe adopted MasterCAM proceeding CNC programme of the mold. MasterCAM is developed by CNC Soft-ware. INC corporation America which be extensive used by industrial community. It is widely used in mecha-nism mold , automobile，shipbuilding，aerospace etc. Its three - dimensional curve surface ，solid modeling ,highly active compact CNC programme and postposition dispose function realized CAD/CAM unitization thatfrom product geometric design to process. It also can make enterprise acquiring overt economic strategical andsocial benefits by improving the product quality of design and shortening production circle.MasterC AM has many surface processing method such as surface contouring , surface parallel process , sur-face streamline process , surface radiate process , surface isometry encompass process etc. Because the quality ofsurface contouring is not very well and process period is relative中国煤化工、: order to obtaining bet-er process quality , we must subsidiary homologous supple p: of surface streamlineprocess in simple non-streamline surface process is not very weMYHc N M H G in complicated surfacestreamline process , so we do not adopt it. The selection of radiate center and the distance of working point andradiate center will affect process quality and process period , so we also do not adopt it. Because surface isometryencompass process do well in different kinds of surface process and it costs a short time in process period ,so we- 59selected surface isometry encompass process in the mold process 13 .We adopted copper rod which diameter is 16 mm as raw and processed materials. The photo is shown inFig. 4.4 ConclusionsThis article finished the measurement , design and process of spurious tympanic membrane. It utilized re-verse engineering solving the medically puzzle , and also realized multidisciplinary collaborate and research. Butthere are a great many of insufficiency in this research such as acoustical stereo coupling of spurious tympanicmembrane need us do more improvement. We will solve correlation problem in our next step so that the spurioustympanic membrane will not only moulding surface similitude but also functional bionics.References[1 ] Gerard JM , Decat M , Gersdorff M. Tragal Cartilage in Tympanic Membrane Reconstruction. Acta Otorhinolaryngol Belg ,2003 57 2 ):147-50.[2] YU Lisheng HAN Chaogang. Typing and Basic Conception of aures Operation. Chinese Journal of otology. 2004 2( 4 ) 280-284 ( in Chinese).[3] Gierek T. , Slaska Kaspera A. , Majzel K. , Klimczak Golab L. Results of Myringoplasty and Type I Tympanoplasty with theuse of Fascia , Cartilage and Perichondrium Grafts. Otolaryngol Pol. 2004 58( 3 ) 529-33.[4] Dornhoffer J. Cartilage Tympanoplasty : Indications , Techniques , and Outcomes ina 1 ,00 patient series. Laryngoscope2003 ,113( 11 ):1844-56.[5] Khan I. Jan A. M. ,Shabzad F. Middle ear Reconstruction : A Review of 150 Cases. Journal of Laryngology & Otology，2002 ,116 6 ) :435-439.[6] Ikui A. Sando I. ,Haginomori S. , Sudo M. 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