Direct Numerical Control Research Articles

Delayed Orbital Floor Reconstruction Using Mirroring Technique and Patient-Specific Implants: Proof of Concept.

Enophthalmos is a severe complication of primary reconstruction following orbital floor fractures, oncological resections, or maxillo-facial syndromes. The goal of secondary orbital reconstruction is to regain a symmetrical globe position to restore function and aesthetics. In this article, we present a method of computer-assisted orbital floor reconstruction using a mirroring technique and a custom-made titanium or high-density polyethylene mesh printed using computer-aided manufacturing techniques. This reconstructive protocol involves four steps: mirroring of the healthy orbit computer tomography files at the contralateral affected site, virtual design of a customized implant, computer-assisted manufacturing (CAM) of the implant using Direct Metal Laser Sintering (DMLS) or Computer Numerical Control (CNC) methods, and surgical insertion of the device. Clinical outcomes were assessed using 3dMD photogrammetry and computed tomography measures in 13 treated patients and compared to a control group treated with stock implants. An improvement of 3.04 mm (range 0.3-6 mm) in globe protrusion was obtained for the patients treated with patient-specific implants (PSI), and no major complications have been registered. The technique described here appears to be a viable method for correcting complex orbital floor defects needing delayed reconstruction.

Application of Lean Six Sigma for Improve Productivity at The Mechanical Plant. A Case Study

This study focuses on performing the analysis of manipulator operations on the machining line of precision mechanical products using the Human-Machine correlation analysis tool through images collected from the camera, wasteful operations incurred in machining according to Lean Six Sigma (LSS) standards to control fluctuations in the machining line, improving the overall productivity of the line (OEE). Specifically, contributing to improving productivity, quality, and competitiveness of the company in the market, create a good product image for consumers. This paper proposes a 7-step quality control (QC) cycle improvement model, called 10 step QC cycle. In step 5, use Man - Machine correlation analysis tool from video images to identify wasteful activities. In step 6, we propose a Direct Numerical Control (DNC) model to call the machining program for MC machines using a barcode system and a computer vision model for human identification at each processing line according to a controlled fixed layout. The right people have been trained enough to operate the line; the specific result is eliminating the occurrence of accidents in processing from 7 cases to none. A model of a product dimensioning system implemented for fully automated product quality control combined with redesigned machining jig with a vapor sensor system eliminating the reliance on human manipulation Specifically, the result from this improvement activity is the increase in productivity from 115 products per 8 hours to 155 products per 8 hours and the handling time has decreased from 1.3 hours per day to 0.36 hours per day (reduce 0.94 hours per day). The Partial Least Squares Structural Equation Modeling (PLS-SEM) is used to analyze the results of the survey of employees' opinions about the usefulness, convenience, and technical factors after the operation. The results from improvement activities show that user loyalty is highly appreciated in terms of usefulness and convenience. However, in terms of technical factors, it is still necessary to improve the quality of the information network system, the barcode scanning system and the quality of barcodes in the oil environment

AN OVERVIEW OF DIRECT OR DISTRIBUTED NUMERICAL CONTROL IN COMPUTER NUMERICAL CONTROL APPLICATIONS

Direct numerical control is also known as distributed numerical control (also abbreviated DNC), is a common manufacturing term for networking CNC machine tools. On some CNC machine controllers, the available memory is too small to contain the machining program (for example machining complex surfaces), so in this case the program is stored in a separate computer and sent directly to the machine, one block at a time. If the computer is connected to a number of machines it can distribute programs to different machines as required. Usually, the manufacturer of the control provides suitable DNC software. However, if this provision is not possible, some software companies provide DNC applications that fulfill the purpose. DNC networking or DNC communication is always required when Computer-Aided Manufacturing (CAM) programs are to run on some CNC machine control. Wireless DNC is also used in place of hard-wired versions. Controls of this type are very widely used in industries with significant sheet metal fabrication, such as the automotive, appliance, and aerospace industries. A DNC system has to fulfill two basic tasks such as first guaranteeing secure, timely data transfer from and to the CNC controllers, secondly administering many thousands of NC programs.

HydraX, a 3D printed robotic arm for Hybrid Manufacturing. Part II: Control, Calibration & Programming

This part of the study focuses on programming, control and calibration aspects of HydraX, a low cost 6-axis 3D printed robotic arm that performs both Additive and Subtractive Manufacturing. G-code was implemented as the programming language for HydraX, after proper process CAM modeling and code extraction. CAM software post-processor was developed as a Finite-State Machine (FSM), so that NC output files are automatically adjusted, when software input variable values change. Arduino Mega microcontroller has been connected in parallel to the motion controller board of HydraX for expansion of system functionality and enabling the hybrid manufacturing concept. Custom commands (M codes) have also been developed to establish the connection between CAM post-processor and Direct Numerical Control (DNC) software. With these additions, the automatic end effector changer controls the CNC milling spindle, hot end with temperature measurement, filament extrusion and cooling fan speed adjustment, thus leading to successful hybrid manufacturing processes.

A Method of Generating Spiral Tool Path for Direct Three-Axis Computer Numerical Control Machining of Measured Cloud of Point

Smooth continuous spiral tool paths are preferable for computer numerical control (CNC) machining due to their good kinematic and dynamic characteristics. This paper presents a new method to generate spiral tool paths for the direct three-axis CNC machining of the measured cloud of point. In the proposed method, inspired by the Archimedean spiral passing through the radial lines in a circle, 3D radial curves on the cloud of point are introduced, and how to construct the radial curves on the complex cloud of point is discussed in detail and then a practical and effective radial curve construction method of integrating boundary extraction, region triangulation, mesh mapping, and point projection is proposed. On the basis of the radial curves, the spiral tool path can be generated nicely by interpolating the radial curves using a spiral curve. Besides, the method of identifying and eliminating the overcuts and undercuts in the spiral tool path resulting from the interpolation error is also presented for good surface quality. Finally, several examples are given to validate the proposed method and to show its potential in practical applications when quality parametric models and mesh models are not available.

Computer Aided Drafting and Manufacturing Lab Manual - CAD/CAM

Computer-aided design (CAD) involves creating computer models defined by geometrical parameters. These models typically appear on a computer monitor as a three-dimensional representation of a part or a system of parts, which can be readily altered by changing relevant parameters. CAD systems enable designers to view objects under a wide variety of representations and to test these objects by simulating real-world conditions. Computer-aided manufacturing (CAM) uses geometrical design data to control automated machinery. CAM systems are associated with computer numerical control (CNC) or direct numerical control (DNC) systems. These systems differ from older forms of numerical control (NC) in that geometrical data are encoded mechanically. Since both CAD and CAM use computer-based methods for encoding geometrical data, it is possible for the processes of design and manufacture to be highly integrated. Computer-aided design and manufacturing systems are commonly referred to as CAD/CAM.

A Graphics Processor Unit-Accelerated Freeform Surface Offsetting Method for High-Resolution Subtractive Three-Dimensional Printing (Machining)

Machining is one of the major manufacturing methods having very wide applications in industries. Unlike layer-by-layer additive three-dimensional (3D) printing technology, the lack of an easy and intuitive programmability in conventional toolpath planning approach in machining leads to significantly higher manufacturing cost for direct computer numerical control (CNC)-based prototyping (i.e., subtractive 3D printing). In standard computer-aided manufacturing (CAM) packages, general use of B-rep (boundary representation) and non-uniform rational basis spline (NURBS)-based representations of the computer-aided design (CAD) interfaces make core computations of tool trajectories generation process, such as surface offsetting, difficult. In this work, the problem of efficient generation of freeform surface offsets is addressed with a novel volumetric (voxel) representation. It presents an image filter-based offsetting algorithm, which leverages the parallel computing engines on modern graphics processor unit (GPU). The compact voxel data representation and the proposed computational acceleration on GPU together are capable to process voxel offsetting at four-fold higher resolution in interactive CAM application. Additionally, in order to further accelerate the offset computation, the problem of offsetting with a large distance is decomposed into successive offsetting using smaller distances. The performance trade-offs between accuracy and computation time of the offset algorithms are thoroughly analyzed. The developed GPU implementation of the offsetting algorithm is found to be robust in computation, and demonstrates a 50-fold speedup on single graphics card (NVIDIA GTX780Ti) relative to prior best-performing algorithms developed for multicores central processing units (CPU). The proposed offsetting approach has been validated for a variety of complex parts produced on different multi-axis CNC machine tools including turning, milling, and compound turning-milling.

Two different techniques of manufacturing TMJ replacements – A technical report

IntroductionPresently, during the surgical treatment of the patients in maxillofacial surgery, one can use various medical implants. Moreover custom made implants are being used. Replacements may be fitted to the structure and shape of the human skull owing to CAD/CAM (custom aided design/manufacture) called customized implants. This study was aimed to report for the first time clinical material from which custom implants, using two different techniques, were manufactured to reconstruct the temporomandibular joint (TMJ). Material and methodsIn this study, eleven patients with an average age of 54 years were included. All of the patients underwent TMJ reconstruction using direct metal laser sintering (DMLS) or computer numerical control milling (CNC) techniques for implant manufacture. Four of the eleven patients had a malignancy diagnosis, and seven had a benign diagnosis. Patients complained of hypomobility of the TMJ, facial asymmetry, pain and swelling of the preauricular region. Treatment included 7 CNC milled implants and 4 implants in DMLS. ResultsMore metallic implant parts with a rough surface were associated with the DMLS technique. Post operational, uneventful healing was observed in all clinical cases during an average of 26.8 months of follow-up. Three months post-operation, facial nerve palsy, swallowing disturbances and pain were not observed. Infections, allergic reactions to materials and re-ankylosis were also not observed. Replacements received correct forms and functions owing to the CAM techniques. Post-operational maximal interincisal opening improved (p < 0.01) and was not significantly related to preoperational opening, age, sex, diagnosis or adjuvant radiotherapy. ConclusionConsidering both methods, the feature that differentiates the manufacture technique is the more subtractive surface finishing required for the DMLS implant than the CNC implant. Both techniques resulted the same clinical outcomes and can be used successfully in patients with neoplastic lesions and other TMJ disorders. Unfortunately, DMLS is more vulnerable to fracture.

The System Software for Automatic Jam Detection and Recovery on Manufacturing System

In manufacturing system, around the year 1950’s, computer aided design (CAD) and developments of NC resulted which led to the evolution of systems like computer numerical control (CNC) and direct numerical control (DNC). Today, computer integrated manufacturing is a reality. The advent of computer integrated manufacturing system has got an efficiency and high performance for production. And manufacturing system operating ratio was related by cost-efficiency of the factory operation and increasing good production. However it has still problem that the system engineer who is in the factory hard to keep watching the manufacturing system always in order to recover the manufacturing system when it has system error. In this paper, we propose system jam detection and recovery process for manufacturing system. For this process, we make and use system Jam Database and Jam Recovery Process Sequence.

Age models and the Younger Dryas Impact Hypothesis

Israde-Alcantara et al. (1) drew on interpretations of a core from Lake Cuitzeo, Mexico to support the Younger Dryas (YD) Impact Hypothesis. A key aspect of their study was identifying and dating the YD interval in the sediments. The authors stated that they recovered impact indicators from a 10-cm-thick zone dating to 12.9 kcal BP but provided no direct numerical age control or chronological uncertainties for this interval. Depending on the carbon sources, 14C ages of bulk lake sediment can be offset by several centuries (2). However, even though the study used bulk 14C dates, no offset was quantified. Dating of the section was accomplished by interpolating through >1 m of undated sediment, because the six dates in that interval were rejected. Even so, the rejected dates were in stratigraphic order, and there seems no a priori basis to exclude them. Their age model was anchored by a tephra layer identified as the Cieneguillas rhyolitic tephra, dated elsewhere as ∼31 kcal BP (3), but no geochemical evidence was provided to support this tephra identification.

Direct Numerical Control (NC) Path Generation: From Discrete Points to Continuous Spline Paths

Spline paths in NC machining are advantageous over linear and circular paths due to their smoothness and compact representation, thus are highly desirable in high-speed machining (HSM) where frequent change of tool position and orientation may lead to inefficient machining, tool wear, and chatter. This paper presents an approach for calculating spline NC paths directly from discrete points with controlled accuracy. Part geometry is represented by discrete points via an implicit point set surface (PSS). Cutter location (CL) points are generated directly from implicit part surfaces and interpolated by B-spline curves. A computing procedure for calculating maximum scallop height is given. The procedure is general and suitable for part surfaces in various surface representations provided that the closest distance from a point to the part surface can be calculated. Our results affirm that the proposed approach can produce high-quality B-spline NC paths directly from discrete points. The resulting spline paths make it possible for directly importing discrete points into Computer Numerical Control (CNC) machines for high-speed machining.

Shop floor manufacturing technology adoption decisions

Purpose – The purpose of this paper is to identify key factors that influence the decision to adopt computerized numerical control (CNC) and direct numerical control (DNC) machines, material working lasers and robots (specific advanced manufacturing technologies – AMT) using the theory of planned behavior (TPB) as the underlying framework.

Shop floor manufacturing technology adoption: an adaptation of the technology acceptance model

This research examines the decision process for adopting a specific subset of advanced manufacturing technologies: computerised numerical control (CNC), direct numerical control (DNC), material working lasers, and robots, a subset of AMT collectively referred to as shop floor manufacturing technology (SFMT). A modified technology acceptance model was developed to test the proposed relationships in the decision process. Survey responses from 124 managers who recently invested in an SFMT were analysed using structural equation modelling. The modified model provides a framework for examining SFMT adoption processes, though not all hypotheses were supported. For example, supplier support did not have a significant influence on perceived behavioural control, suggesting that technology suppliers remain an untapped resource. SFMT performance outcomes suggest that adopters are making good decisions, though there is room for improvement.

Application of DNC Communication System Based on Network Manufacturing Technology

DNC is referred to as the Direct Numerical Control, Intended for direct digital control. It means a number of numerical control equipment directly connected to a computer, and the central computer in charge of the NC program’s management and transfer. At present, DNC system includes not only the NC program, but also the manufacturing data of the specific tasks required for the production, such as cutting tools data, scheduling, configuration information of machine tools, and so on, and part of the DNC system also has the functions of machine tool state acquisition and remote control.

Installation for Belt Transmission Testing

Installations enabling experiments at modern level were required for perfection of the theory of V-belt transmissions and designing recommendations. The article considers features of experimental installation of Machine Parts and Elevating Transport Mechanisms Department of the Moscow State Technical University MAMI where modern demands are considered, particularly raise of accuracy of measured parameters, transmission type, a direct numerical control and machining of experimental data.

Study on Key Technologies of DNC System Oriented Networked Manufacturing

As one of major methods to meet information integration of numerical control machines in workshop, DNC (Direct Numerical Control or Distributed Numerical Control) oriented networked manufacturing (Web-DNC system) differs dramatically from conventional ones by having: (1) concurrently supporting networked manufacturing; (2) sharing the numerical control machines via network; (3) optimizing the configuration and reorganization of numerical control resources. This paper deals with the key technologies of Web-DNC system, including: the implementing architecture model with four layers (user layer, service layer, agent layer and facility layer) and the topology architecture. The BL2000 SCM is selected as a COM server to meet the required capabilities of DNC controller. Compared with the communication architecture with fieldbus, a simpler function model of DNC communication technology based on Ethernet technology is presented. A Web-DNC system prototype is developed and proved to be effective in information integration of numerical control machines in injecton workshop.

Direct tool-path generation from massive point input

The paper presents an algorithm and methodologies for the direct numerical control (NC) cutter path generation from a point cloud. Different from the existing approach, it will generate the cutter path without any reconstruction of the surface patch. Based on the scanned data, a ball nose cutter is assumed to move over the points with a specific cutter diameter. A sphere (shape of cutter) with a specific radius is formed by two or more digitized points. The approach combines point pairs to form rows of spheres. By joining the centre of spheres with are splines, the preliminary tool path is calculated. Finally, the exact tool path is found by means of a general compensation algorithm.

A tool for the interactive 3D visualization of electronic structure in molecules and solids

This paper presents the Vienna ab initio simulation package (VASP) data viewer, a desktop 3D visualization application for the analysis of valence electronic structure information derived from first-principles quantum-mechanical density functional calculations. This tool allows a scientist to directly view and manipulate the calculated charge density or electron localization function (ELF) from an electronic structure calculation, providing insight into the nature of chemical bonding. Particular attention was given to the design and implementation of the user interface (UI) for the data viewer. It provides for expert and novice usage, and both natural direct manipulation and precise numerical control. The data viewer has proven useful to chemical scientists for understanding the results of electronic structure calculations.

DNS-based predictive control of turbulence: an optimal benchmark for feedback algorithms

Direct numerical simulations (DNS) and optimal control theory are used in a predictive control setting to determine controls that effectively reduce the turbulent kinetic energy and drag of a turbulent flow in a plane channel at Reτ = 100 and Reτ = 180. Wall transpiration (unsteady blowing/suction) with zero net mass flux is used as the control. The algorithm used for the control optimization is based solely on the control objective and the nonlinear partial differential equation governing the flow, with no ad hoc assumptions other than the finite prediction horizon, T, over which the control is optimized.Flow relaminarization, accompanied by a drag reduction of over 50%, is obtained in some of the control cases with the predictive control approach in direct numerical simulations of subcritical turbulent channel flows. Such performance far exceeds what has been obtained to date in similar flows (using this type of actuation) via adaptive strategies such as neural networks, intuition-based strategies such as opposition control, and the so-called ‘suboptimal’ strategies, which involve optimizations over a vanishingly small prediction horizon T+ → 0. To achieve flow relaminarization in the predictive control approach, it is shown that it is necessary to optimize the controls over a sufficiently long prediction horizon T+ [gsim ] 25. Implications of this result are discussed.The predictive control algorithm requires full flow field information and is computationally expensive, involving iterative direct numerical simulations. It is, therefore, impossible to implement this algorithm directly in a practical setting. However, these calculations allow us to quantify the best possible system performance given a certain class of flow actuation and to qualify how optimized controls correlate with the near-wall coherent structures believed to dominate the process of turbulence production in wall-bounded flows. Further, various approaches have been proposed to distil practical feedback schemes from the predictive control approach without the suboptimal approximation, which is shown in the present work to restrict severely the effectiveness of the resulting control algorithm. The present work thus represents a further step towards the determination of optimally effective yet implementable control strategies for the mitigation or enhancement of the consequential effects of turbulence.

Intelligent 3D CAD Data Extraction System.

In this study, an intelligent 3D surface-data extraction system which integrates a Laser Displacement Meter(LDM), a CNC Machining Center(CNC), and a Personal Computer(PC)-486 is developed. In this intelligent system, LDM, CNC, and PC play the roles of distance-measuring sensor, measurement-frame, and main control device, respectively. By enforcing the Direct Numerical Control(DNC)technique, the CNC can be controlled to carry the LDM to measure specified objects or parts automatically. In addition to the effective measurement of thin and complex objects, a new process which combines the contacting and noncontacting methods is established to handle those objects with larger height differences. Furthermore, the Medium Filter technique is applied to filter out the impulse like measuring noise which always occurs in the sharp edges between surfaces. Moreover, a new algorithm is also proposed to efficiently eliminate redundant measured data points. This algorithm enables the users to minimize computing time and reduce memory space during surface reconstruction. Experimental results show that the Medium Filter can successfully wipe out impulse like noise and the proposed redundant data eliminating algorithm can significantly reduce the redundant measured 3D surface data without losing the characteristics of the target surface.