Theoretical Research On The Intersected Polishing With Free-form Surfaces And It's Track Programming

1. IntroductionWith the fast development of computer technique and modern control theory,The number control machining for represent gentle process has already nearperfect.It can realize the automation for the machining of free-formsurface.However, these subsequent processes of precision machining still dependmainly on the handwork of skilled mechanists presently. The light finishingmachining for large free-form surface is the weak tache for the productiond ofmold. It also can become the bottleneck for the development of the moldmanufacturing industry. The international community competitively developautomation light finishing machining technology and regard computer techniqueas the support in order to overcoming the lower efficiency problem inside the largefree-form surfaces. The aim is developping to realize the automation for themachining of free-form surface, and the necessary furnishment and pivotaltechnique in the whole process.The robot is one of the important tools to realizing the automation lightfinishing machining for free-form surfaces. But in the process of machining largefree-form surface,it not only need the polishing tool gesture function accuratelyalong the preconcerted track.but also need keep the particular carriage and stablepressure at the same time. Keep particular carriage, certanly will sacrifice theworking-space.For increasing the working-space but length the arm of the robotwill cause the accuracy or rigid shortage of the robot .So it exsits the antinomybetween the accuracy and rigidity that realizing the automation for the machiningof free-form surface only by robot.In ordor to solving the antinomy above and enhancing the accuracy andrigidity on the machining of the large free-form surface, We analyze the polishingprocess of handwork at the first time ,and putting forward the thought of dividingthe free-form surface into different parts for programing according to the calculatorsketch information structure characteristics. it can divide the large free-formsurface into some districts ,then programing the polishing track and optimizing thepolishing pose in these areas.2. The arithmetic how to distill the boundary of NURBS curved surface andthe intersected thought Through researching the character of the curved face , one normal curvature ofthe the curved face is aways correspond to one specifically direction.But thedirections of this point is numberless, Among them there always exsits one biggestand one minimum normal curvature. Suppose k1 ,as the biggest one, Suppose k2as the minimum one, Then they are called the main curvature. Their directions iscalled the main direction. Comparing the main curvature with the gauss curvatureand the average curvature,The main curvature is a effective descriptive sign.Analyzing k1,k2 has the same result as analyzing the Gauss curvature and theaverage curvature . The different pieces of the curved surface have the differentcharacters,and the Gauss curvature and the average curvature also have thedifferent numerical value. This paper through computing the Gauss curvature theaverage curvature as the judgment how to distill the boundary of NURBS curvedsurface.Through this method the big curved surface can be divided into differentpieces that have the specifically characteristic.such as : the plane group, thecylinder group, the cone surface, the sphere surface, the generic similar spheresurface etc.it establish the academic elements for the later machining of the curvedsurface. When processing the free-form surface ,even it achieve the perfect state thateverywhere of the curved surface has the common character.For processing a planefield, it Sometimes will be restricted by the deficient homework space or thepolishing pose of the machine tool. So this paper combines the JDYP51 typepolishing machine made by the Jilin University to divide the big piece field that hasbeen divided again. Namely "the second time intersected"thought. it mainlyconsiders the restrict of the working space of machine tool,the principle is basingon the geometrical partition and optimize problem on the math. It requests the parts intersected are more little more good under the limit. Theidiographic implementary method is as follows: ⑴To Make sure the biggest artifactitious journey of the 'z'direction of thecurved surface is whether be restricted by the working space in the plumb linedirection of the shunt-wound platform and deal with the curved surface in the 'z'direction,then go on the step ②. ⑵According to the stipulation of working space in the level parameter areaof the curved surface to divide it ulteriorly. The completely agility working spacein the level parameter area is composed by three circular arcs,but it is notcontrolled freely. So this paper Makes use of the biggest circle inside as therestriction of the level working space for the division.It discusses some normalshapes (rectangle, triangle, circular, free shape) in the level parameter area of thecurved surface,and gives the resolvent.3. The content of the track programming for the machining of NURBScurved surface ●The research for processing the single NURBS curved surface. Speakingtheoretically, when polishing one NURBS curved surface, Its polishing path can bechoosed arbitrarily, But the nonstandard polishing path will increase thecalculational quantity. Under the normal condition, The NURBS curved surfacehas the unit rectangle well-defined area. The valuex of (u,v )is intersectantvertically,This characteristic can be used to make certain the polishing path.theactual artifactitious direction can choose one of them, and the other one as theartifactitious row-process direction. ●The research for processing the combinatorial NURBS curved surface. Sayingto the rubbing, the primary influence factors for the result and efficiency are that:the polishing tools,the rotate speed of principal axis and the row-process speed.But in once process, the polishing tool is one of the main factors that influencesthe efficiency greatly. Speaking to the glancing polishing:the efficiency of the flatgrinding wheel is good for the plane field; the efficiency of the chapiter grindingwheel is good for the cylinder; the efficiency of the roundness is good for thegeneric curved surface. So it can be seen that the efficiency can be improvedgreatly if dividing the combinatorial NURBS curved surface into some different...