From computer-aided to intelligent machining: Recent advances in computer numerical control machining research

The aim of this paper is to provide an introduction and overview of recent advances in the key technologies and the supporting computerized systems, and to indicate the trend of research and development in the area of computational numerical control machining. Three main themes of recent research in CNC machining are simulation, optimization and automation, which form the key aspects of intelligent manufacturing in the digital and knowledge based manufacturing era. As the information and knowledge carrier, feature is the efficacious way to achieve intelligent manufacturing. From the regular shaped feature to freeform surface feature, the feature technology has been used in manufacturing of complex parts, such as aircraft structural parts. The authors’ latest research in intelligent machining is presented through a new concept of multi-perspective dynamic feature (MpDF), for future discussion and communication with readers of this special issue. The MpDF concept has been implemented and tested in real examples from the aerospace industry, and has the potential to make promising impact on the future research in the new paradigm of intelligent machining. The authors of this paper are the guest editors of this special issue on computational numerical control machining. The guest editors have extensive and complementary experiences in both academia and industry, gained in China, USA and UK

Advanced Process Planning for Subtractive Rapid Prototyping

This paper presents process planning methods for Subtractive Rapid Prototyping, which deals with multiple setup operations and the related issues of stock material management. Subtractive Rapid Prototyping (SRP) borrows from additive rapid prototyping technologies by using 2½D layer based toolpath processing; however, it is limited by tool accessibility. To counter the accessibility problem, SRP systems (such as desktop milling machines) employ a rotary fourth axis to provide more complete surface coverage. However, layer-based removal processing from different rotary positions can be inefficient due to double-coverage of certain volumes. This paper presents a method that employs STL models of the in-process stock material generated from slices of the part along the rotation axis. The developed algorithms intend to improve the efficiency and reliability of these multiple layer-based removal steps for rapid manufacturing.Mechanical Engineerin

A novel haptic model and environment for maxillofacial surgical operation planning and manipulation

This paper presents a practical method and a new haptic model to support manipulations of bones and their segments during the planning of a surgical operation in a virtual environment using a haptic interface. To perform an effective dental surgery it is important to have all the operation related information of the patient available beforehand in order to plan the operation and avoid any complications. A haptic interface with a virtual and accurate patient model to support the planning of bone cuts is therefore critical, useful and necessary for the surgeons. The system proposed uses DICOM images taken from a digital tomography scanner and creates a mesh model of the filtered skull, from which the jaw bone can be isolated for further use. A novel solution for cutting the bones has been developed and it uses the haptic tool to determine and define the bone-cutting plane in the bone, and this new approach creates three new meshes of the original model. Using this approach the computational power is optimized and a real time feedback can be achieved during all bone manipulations. During the movement of the mesh cutting, a novel friction profile is predefined in the haptical system to simulate the force feedback feel of different densities in the bone

Hybrid manufacturing of complex components: Full methodology including laser metal deposition (LMD) module development, cladding geometry estimation and case study validation

To optimize and satisfy current industrial requirements, during the last decade new alternatives to conventional manufacturing processes are implemented into conventional machines, leading to multitasking machines. Especially hybrid machines combining additive and subtractive technologies (AM/SM), have become a potential solution for manufacturing and repairing operations in terms of material waste reduction, time consumption and flexibility. Nevertheless, this technology has implications for the machine and the auxiliary elements as well as other challenges: digitalization, process parameterization or CAD/CAM solutions. Thereby, this work proposes a new methodology for hybrid manufacturing systems, a programmed interface to interact between additive and subtractive technologies within the same environment. The developed application programming interface (API) offers a CAM module oriented to AM with appropriate laser metal deposition (LMD) parameters, with three different options of strategy programming: Planar LMD, 3-axis LMD and 5-axis LMD. Additionally, the value of this work stems from the implementation of an algorithm to estimate the cladding geometry, so, the full resulting geometry can be considered as the new blank for SM. A height measuring laser sensor was implemented in the LMD machine to obtain the real height of the generated clad, critical for the next machining step. Finally, to validate the methodology, a blisk made of Hastelloy (R) X was built-up on Inconel (R) 718 with LMD and milled to the final size. Dimensional deviation was measured after each process.This work is based on the grant number [BES-2014-068874] of the Spanish Ministry of Economy and Competitiveness. Also, this work has been sponsored by the H2020-FoF13 PARADDISE Project [Grant Agreement No. 723440]

Fabrication of a Small Scale Model of Chancellor Award Trophy using CAD/CAM and CNC Milling Machine

The Final Year Project (FYP) is to manufacture a small scale model of Chancellor Award Trophy using Computer Aided Design (CAD)/ Computer Aided Manufacturing (CAM) and Computer Numerical Control (CNC) milltng. The main purpose of the project is to manufacture the model by utilizing the tools and machine provided in UTP. The objectives of this project are to create 2D and 3D model (CAD) drawing of the model, to define tool path for NC codes development (CAM) and to fabricate the model using CNC milling machine (CAM). Clear and sufficient understanding of CAD/CAM process and software is needed in order to create 2D and 3D drawing thus to generate NC codes for manufacturing. The methodology involve in this project are studying and research on CAD/CAM component and familiarization on Unigraphics NX software. Next is to come up with the 2D drafting and 3D solid model drawing of the model using Unigraphics NX software. Then, overall shape and dimension of the part from the drawing will be used to define tool path to allow the Unigraphics NX software to generate the coding for CNC machining. The end results of this project are; i) 2D drafting and 3D solid model drawing, ii) Tool path, iii) NC codes, iv) Small scale model of the trophy

A certification method for the milling process of free-form surfaces using a test part

International audienceIt is generally admitted that the manufacturing of free-form surfaces requires the use of a CAD-CAM system. The toolpath accuracy and the dimensional quality of the final shape have to be in accordance with the geometrical specifications. But most of the time, the final parts present deviations from the expected shape. These deviations may be due to either the toolpath calculation (CAM system) or the cutting process itself. In the paper, we propose an analysis of the whole milling process to point out the possible sources of errors. These errors generally lead to geometrical deviations and the final part does not meet the required specifications. As the errors can be linked to geometrical particularities of the shape, we propose a test part associated with check means to bring out problems. The milling of this part using two different techniques of toolpath generation shows that obviously both toolpaths are not error-free and that errors result from different geometrical particularities of the part surfaces

Performance improvement of the LM device and its application to precise measurement of motion trajectories within a small range with a machining centre

In order to apply the LM device previously developed to precisely measuring small motion trajectories located on the different motion planes, three major improvements are successfully performed under the condition of completely maintaining the advantages of the device. These improvements include 1) development of a novel connection mechanism to smoothly attach the device to the spindle of a machining centre; 2) employment of a new data sampling method to achieve a high sampling frequency independent of the operating system of the control computer; and 3) proposal of a set-up method to conveniently install the device on the test machining centre with respect to different motion planes. Practical measurement experiment results with the improved device on a machining centre sufficiently demonstrate the effectiveness of the improvements and confirm several features including a very good response to small displacement close to the resolution of the device, high precision, repeatability and reliance. Moreover, based on the measurement results for a number of trajectories for a wide range of motion conditions, the error characteristics of small size motions are systematically discussed and the effect of the movement size and feed rate on the motion accuracy is verified for the machining centre tested