25 research outputs found
5-axis double-flank CNC machining of spiral bevel gears via custom-shaped milling tools -- Part I: modeling and simulation
A new category of 5-axis flank computer numerically controlled (CNC) machining, called \emph{double-flank}, is presented. Instead of using a predefined set of milling tools, we use the shape of the milling tool as a free parameter in our optimization-based approach and, for a given input free-form (NURBS) surface, compute a custom-shaped tool that admits highly-accurate machining. Aimed at curved narrow regions where the tool may have double tangential contact with the reference surface, like spiral bevel gears, the initial trajectory of the milling tool is estimated by fitting a ruled surface to the self-bisector of the reference surface. The shape of the tool and its motion then both undergo global optimization that seeks high approximation quality between the input free-form surface and its envelope approximation, fairness of the motion and the tool, and prevents overcutting. That is, our double-flank machining is meant for the semi-finishing stage and therefore the envelope of the motion is, by construction, penetration-free with the references surface. Our algorithm is validated by a commercial path-finding software and the prototype of the tool for a specific gear model is 3D printed.RYC-2017-22649
BERC 2014-201
Efficient 5-axis CNC trochoidal flank milling of 3D cavities using custom-shaped cutting tools
A novel method for trochoidal flank milling of 3D cavities bounded by free-form surfaces is proposed. Existing 3D trochoidal milling methods use on-market milling tools whose shape is typically cylindrical or conical, and is therefore not well-suited for meeting fine milling tolerances required for finishing of benchmark free-form surfaces like blades or blisks. In contrast, our variational framework incorporates the shape of the tool into the optimization cycle and looks not only for the trochoidal milling paths, but also for the shape of the tool itself. High precision quality is ensured by firstly designing flank milling paths for the side surfaces that delimit the motion space, in which the trochoidal milling paths are further computed. Additionally, the material removal rate is maximized with the cutter-workpiece engagement being constrained under a given tolerance. Our framework also supports multi-layer approach that is necessary to handle deep cavities. The ability and efficacy of the proposed method are demonstrated by several industrial benchmarks, showing that our approach meets fine machining tolerances using only a few trochoidal paths.RYC-2017-2264
Reparameterization of ruled surfaces: toward generating smooth jerk-minimized toolpaths for multi-axis flank CNC milling
This paper presents a novel jerk minimization algorithm in the context of multi-axis flank CNC machining. The toolpath of the milling axis in a flank milling process, a ruled surface, is reparameterized by a B-spline function, whose control points and knot vector are unknowns in an optimization-based framework. The total jerk of the tool's motion is minimized, implying the tool is moving as smooth as possible, without changing the geometry of the given toolpath. Our initialization stage stems from measuring the ruling distance metric (RDM) of the ruled surface. We show on several examples that this initialization reliably finds close initial guesses of jerk-minimizers and is also computationally efficient. The applicability of the presented approach is illustrated by some practical case studies.RYC-2017-2264
Manufacturing Processes of Integral Blade Rotors for Turbomachinery, Processes and New Approaches
Manufacturing techniques applied to turbomachinery components represent a challenge in the aeronautical sector. These components are commonly composed of high resistant super-alloys; in order to satisfy the extreme working conditions, they have to support during their useful life. Besides, in the particular case of Integrally Bladed Rotors (IBR), they usually present complex geometries that need to be roughed and finished by milling and grinding processes, respectively. Thermoresistant superalloys present many challenges in terms of machinability what leads to find new alternatives to conventional manufacturing processes. In order to face this issue, this work presents a review of the last advances for IBR manufacturing and repairing processes.We are grateful to Basque Excellence university Groups IT IT1337-19, and Ministry of economy project IBRELIABLE (DPI2016-74845-R), and Elkartek PROCODA KK 2019-004
Super Abrasive Machining of Integral Rotary Components Using Grinding Flank Tools
Manufacturing techniques that are applied to turbomachinery components represent a challenge in the aeronautic sector. These components require high resistant super-alloys in order to satisfy the extreme working conditions they have to support during their useful life. Besides, in the particular case of Integrally Bladed Rotors (IBR), usually present complex geometries that need
to be roughed and finished by milling and grinding processes, respectively. In order to improve their manufacturing processes, Super Abrasive Machining (SAM) is presented as a solution because it combines the advantages of the use of grinding tools with milling feed rates. However, this innovative technique usually needed high tool rotary speed and pure cutting oils cooling. These
issues implied that SAM technique was not feasible in conventional machining centers. In this work, these matters were tackled and the possibility of using SAM in these five-axis centers with emulsion coolants was achieved. To verify this approach, Inconel 718 single blades with non-ruled surfaces were manufactured with Flank-SAM technique and conventional milling process, analyzing cutting forces, surface roughness, and dimension accuracy in both cases. The results show that SAM implies a suitable, controllable, and predictable process to improve the manufacture of aeronautical critical components, such as IBR.FEDE
Optimisation of tool life through novel data acquisition and decision making techniques
Variations in the operation and management of machine tool cutting processes will cause deviations in
the quality of the manufactured parts. Current process management approaches combat these variations using combinations of pre- and/or post- process operator centred actions. The experience of the
Author, and indications from involved industry partners, indicates that the associated ”conservative”
approaches to tool life management is costing between five and ten percent of the money spent on
cutting tools, here amounting to two million pounds per annum. The additional cost of quality arising
from process related variations cannot be accurately assessed.
This research enables the real time assessment of CNC milling cutting processes and the management
of process variations. Innovative systems, programs and algorithms are developed through the course
of this research project for the on-line monitoring of cutting tool health. These innovations include: the
development of a cross-section area model to indicate variable metal removal in milling processes, the
conversion of limited load data into process energy consumption, the engineering of an embedded tool
wear data acquisition program, the application of an offline cubic change-point detection algorithm
to quantitatively identify changes in cutting tool wear behaviour, the implementation of the density
evaluation and separation algorithm to enable the separation of cutting and non-cutting process control
signals, the development of novel Dispersion Plots, and the development of novel 3D process plots for
illustrating instantaneous cutting tool condition.
In support of these innovations specially defined methods of signal analysis are deployed to acquire
information for the assessment of enabled and complex health features. The approach is autonomous
and based upon learning from the acquisition and analysis of information directly from the machine
controller. This approach limits the impact on the operation and availability of the machine tool and
mitigates any further impact on the capacity of the machine tools in question.
Decision making is enabled within the deployed diagnostic techniques. This provides the opportunity
for plant-wide tool condition status monitoring and data visualisation. The deployed approach enables
researchers to engineer machine systems that can provide more accurate, reliable and repeatable
machine operations, with less waste and better managed processes.
It is shown that there is significant value in the process control data that was acquired throughout this
study. The data is used to show the deployed cutting tool condition based on current and imminent
machining requirements. It is also deployed to estimate the expected end of useful life for specific
cutting tools and to generate innovative models of the cutting process. These models will enable
Engineers to improve the cutting processes and to optimise the assessment of cutting tool condition
and life