INTERFERENCE-FREE TOOL POSTURE GENERATION FOR 5-AXIS NC MILLING FREE-FORM SURFACES WITH CYLINDRICAL MILL

The 5-axis NC machining offers the potential of efficient and accuratemachining. However, the present CAM system for 5-axis control is still an unsolved problem due tointerference between tool and surrounding objects. A new method is presented. There are two steps inthis procedure. First, it detects the interference by calculating the shortest distance between thetool-axis and the surrounding surfaces. Then upon the maximum gouging, the interference-free toolposture for 5-axis NC cylindrical milling free-form surfaces is obtained by adjusting tool. Thevalidity of the proposed method has been confirmed by machining an impeller.

Application of digital positioning guide plates for the surgical extraction of multiple impacted supernumerary teeth:A case report and review of literature

BACKGROUND An extra tooth in the normal tooth sequence in any region of the dental arch is regarded as a supernumerary tooth(SNT).Due to the large variation in location and morphology,the extraction of impacted SNTs is an extensive and complex procedure with high risks of several complications.This report presents a rare case of seven impacted SNTs in the bilateral upper and lower arch that were successfully extracted with the use of digital positioning guide plates.CASE SUMMARY In January 2022,a 21-year-old male was referred to our department with a chief complaint of pain in relation to tooth#36.Clinical examination showed a deep carious lesion with pulpal involvement in tooth#36 and lingual swelling of the bilateral mandibular posterior area.Radiographic examination revealed seven deeply impacted SNTs in the bilateral posterior area and bilateral impacted mandibular third molars.Based on these findings,the patient was diagnosed with bilateral,multiple impacted SNTs and tooth#36 chronic pulpitis.A root canal treatment and an all-ceramic crown restoration for tooth#36 were performed.An individualized digital positioning guide plate was designed by computer-aided design/computer-aided manufacturing technology and cone-beam computed tomography for extraction of the impacted SNTs.During the operation,the digital positioning guide plate allowed rapid positioning and exposure of the SNTs while avoiding adjacent important anatomical structures.At 3-month follow-up,regeneration of bone and soft tissues was visible.CONCLUSION The application of digital positioning guide plates is useful for the individualized and minimalized extraction of impacted supernumerary teeth.

Principal Face-based Recognition Approach for Machining Features of Aircraft Integral Panels

Feature recognition aims at extracting manufacturing features with geometrical information from solid model and is considered to be an efficient way of changing the interactive NC machining programming mode.Existing recognition methods have some disadvantages in practical applications.They can essentially handle prismatic components with regular shapes and are difficult to recognize the intersecting features and curved surfaces.Besides,the robustness of them is not strong enough.A new feature recognition approach is proposed based on the analysis of aircraft integral panels＇ geometry and machining characteristics.In this approach,the aircraft integral panel is divided into a number of local machining domains.The machining domains are extracted and recognized first by finding the principal face of machining domain and extracting the sides around the principal face.Then the machining domains are divided into various features in terms of the face type.The main sections of the proposed method are presented including the definition,classification and structure of machining domain,the relationship between machining domain and principal face loop,the rules of machining domains recognition,and the algorithm of machining feature recognition.In addition,a robotic feature recognition module is developed for aircraft integral panels and tested with several panels.Test results show that the strategy presented is robust and valid.Features extracted can be post processed and linked to various downstream applications.The approach is able to solve the difficulties in recognizing the aircraft integral panel＇s features and automatic obtaining the machining zone in NC programming,and can be used to further develop the automatic programming of NC machining.

RESEARCH ON THE 3-AXES ROUGH MILLING OF MULTI-SURFACES

In particular, a fair amount of the machining time may be spent in rough cutting process when a large portion of the raw material has to be removed. Therefore, an algorithm for generating the toolpath for rough cutting is suggested in the paper. The algorithm is based on an extended tracing method for plane/surface intersection is proposed for smooth surface. A 2.5D milling or parallel offset machining is to be used to significantly improve producitvity and lead to lower production costs for the sculptured multi surfaces part rough machining..

RESEARCH AND IMPLEMENTATION OF A HOGGING ALGORITHM

Cast blanks with large-scale free form surfaces are very difficult tomanufacture because of significant casting distortions. It is concerned that the development andapplication of a hogging algorithm for preparing the blanks for an extended rough cutting. Theprocedure includes three main phases. They are the reconstruction of the free form surface withscattered points based on a special Hermite's interpolation, intersection of curved surfaces todefine the hogging areas, and the tool path planning. The result shows that the algorithm is greatlyvalid in reducing the invalid tool paths so that the work efficiency can be improved remarkably.

Slicing Recognition of Aircraft Integral Panel Generalized Pocket

To automatically obtain a machining area in numerical control （NC） programming, a data model of generalized pocket is established by analyzing aircraft integral panel characteristics, and a feature recognition approach is proposed. First, by reference to the practical slice-machining process of an aircraft integral panel, both the part and the blank are sliced in the Z-axis direction; hence a feature profile is created according to the slicing planes and the contours are formed by the intersection of the slicing planes with the part and its blank. Second, the auxiliary features of the generalized pocket are also determined based on the face type and the position, to correct the profile of the pocket. Finally, the generalized pocket feature relationship tree is constructed by matching the vertical relationships among the features. Machining feature information produced by using this method can be directly used to calculate the cutter path. The validity and practicability of the method is verified by NC programming for aircraft panels.

STEP AP 242 Managed Model-based 3D Engineering:An Application Towards the Automation of Fixture Planning

Fixture design and planning is one of the most important manufacturing activities, playing a pivotal role in deciding the lead time for product development. Fixture design, which affects the part-quality in terms of geometric accuracy and surface finish, can be enhanced by using the product manufacturing information(PMI) stored in the neutral standard for the exchange of product model data(STEP) file, thereby integrating design and manufacturing. The present paper proposes a unique fixture design approach, to extract the geometry information from STEP application protocol(AP) 242 files of computer aided design(CAD) models, for providing automatic suggestions of locator positions and clamping surfaces. Automatic feature extraction software "FiXplan", developed using the programming language C#, is used to extract the part feature, dimension and geometry information. The information from the STEP AP 242 file is deduced using geometric reasoning techniques, which in turn is utilized for fixture planning. The developed software is observed to be adept in identifying the primary, secondary, and tertiary locating faces and locator position configurations of prismatic components. Structural analysis of the prismatic part under different locator positions was performed using commercial finite element method software, ABAQUS, and the optimized locator position was identified on the basis of minimum deformation of the workpiece.The area-ratio(base locator enclosed area(%)/work piece base area(%)) for the ideal locator configuration was observed as 33%. Experiments were conducted on a prismatic workpiece using a specially designed fixture, for different locator configurations. The surface roughness and waviness of the machined surfaces were analysed using an Alicona non-contact optical profilometer. The best surface characteristics were obtained for the surface machined under the ideal locator positions having an area-ratio of 33%, thus validating the predicted numerical results. The efficiency, capability and applicability of the developed software is demonstrated for the finishing operation of a sensor cover – a typical prismatic component having applications in the naval industry, under different locator configurations.The best results were obtained under the proposed ideal locator configuration of area-ratio 33%.

Machining Robot with Vibrational Motion and 3D Printer-like Data Interface

In this paper, a vibration motion control is proposed and implemented on a foamed polystyrene machining robot to suppress the generation of undesirable cusp marks, and the basic performance of the controller is verified through machining experiments of foamed polystyrene. Then, a 3 dimensional （3D） printer-like data interface is proposed for the machining robot. The 3D data inter- face enables to control the machining robot directly using stereolithography （STL） data without conducting any computer-aided man- ufacturing （CAM） process. This is done by developing a robotic preprocessor that helps to remove the need for the conventional CAM process by directly converting the STL data into cutter location source data called cutter location （CL） or cutter location source （CLS） data. The STL is a file format proposed by 3D systems, and recently is supported by many computer aided design （CAD）/CAM soft- waxes. The STL is widely used for rapid prototyping with a 3D printer which is a typical additive manufacturing system. The STL deals with a triangular representation of a curved surface geometry. The developed 3D printer-like data interface allows to directly control the machining robot through a zigzag path, rectangular spiral path and circular spiral path generated according to the information included in STL data. The effectiveness and usefulness of the developed system are demonstrated through actual machining experiments.