I. Tabernero

Stability Lobes in Turning of Low Rigidity Components

An accurate prediction of the dynamic stability of a cutting system involves the implementation of tool geometry and cutting conditions on any model used for such purpose. This study presents a dynamic cutting force model based on the collocation method by Chebyshev polynomials taking advantage from its ability to consider tool geometry and cutting parameters. In the paper, a simple 1DOF model is used to forecast chatter vibrations due to the workpiece and tool, which are distinguished in separate sections. The proposed model is verified positively against experimental dynamic tests.

Polishing of Ductile Cast Iron with Scan-Head Guided Fiber Laser

Present work deals with laser polishing process on GGG70L spheroidal cast iron, which is widely used in die making for the automotive industry. Free graphite in the structure of GGG70L makes difficult the polishing and surface roughness reduction because the high melting temperature. In this work a complete study is presented, where main process parameters are identified and free graphite is eliminated from surface. The quantification of surface improvement is presented in terms of resulting surface roughness, hardness, and heat affected layer thickness. Thus, using optimal parameters, laser polishing with 2D scan head gives satisfactory results on GGG70L cast iron with roughness reduction rates up to 80% and minimum mean roughness Ra of 0.5 μm.

Laser hardening model development based on a semi-empirical approach

The present research paper deals with laser surface hardening applied to medium carbon alloy steel AISI 1045. In order to control as much as possible the process, two different models were developed: a semi-empirical and a numerical model. To validate the results several experimental tests were carried out with a high power diode laser, measuring surface temperature with a two colour pyrometer. The process parameters considered in the study have been the laser power, from 1,700 to 1,900 Watt, and the interaction time, from 1 to 4 seconds, for a beam spot diameter of 10.2 mm. The results obtained in hardness value and heat affected zone depth show that the methodology explained is acceptable to evaluate laser hardening effects in an industrial application.

Influence Of The Laser Cladding Strategies On The Mechanical Properties Of Inconel 718

This work presents different experimental results of the mechanical properties of Inconel® 718 test parts built‐up by laser cladding. Recently, turbine manufacturers for aeronautical sector have presented high interest on laser cladding processes. This process allows building fully functional structures on superalloys, such as Inconel® 718, with high flexibility on complex shapes. However, there is limited data on mechanical properties of the laser cladding structures. Moreover, the available data do not include the influence of process parameters and laser cladding strategies. Therefore, a complete study of the influence of the laser cladding parameters and mainly, the variation of the tensile strength with the laser cladding strategy is presented. The results show that there is a high directionality of mechanical properties, depending on the strategies of laser cladding process. In other words, the test parts show a fiber ‐like structure that should be considered on the laser cladding strategy selection.

2D Scan-Head Motion Characterization and Machine-Tool Integration

This work is focused in the integration of a scan-head in a machine tool for laser processing of large areas. The scan-head is a device typically used for marking operations and provides very high linear speeds. Despite scanners present high accuracy for marking speeds below 5,000 mm/s, over this limit, accuracy problems were found. In this kind of device the motion is controlled using high precision actuators but there is no positioning closed-loop and workspace area is typically limited to small working areas. On the other hand, the positioning error varies also with working area plane positioning. This becomes a problem for processing complex shape surfaces. The work presented deals with characterization of the scan head, to identify the parameters affecting the error, the influence of the error with working plane positioning and with the integration of fast rotary axes of the scan head with conventional linear axes of a machine-tool. The proposed solution is based on a NC parent program controlling the linear axis of the machine-tool with integrated subprograms that control rotary axes of the scan-head.

A methodology for process parameter selection in five axis laser cladding

Laser cladding industrial development is becoming an important target for high added value parts manufacturing sectors. Aeronautical or automotive industries are accomplishing great investments in order to understand the process and minimise tuning step costs now paired with. At the moment, the process is applied to three axis or 3 + 2 axis strategies, being numerous works focused on the obtainment of process parameters. All of them try to minimise the number of experimental tests necessary to optimise the great variable involving the process. These variables increase when using laser cladding on five axis kinematics in order to accomplish new targets of industrial sectors which include complex parts with complex surface to clad. The work presents a methodology which helps to choose optimal parameters for five axis laser cladding. A weighted criterion is used in order to discern between different parameters taking into account process requirements. The methodology has been used on two materials and differ...

Quality Training and Research around the Machine Tools

The best is to read these instructions and follow the outline of this text. The text area for your manuscript must be 17 cm wide and 25 cm high. The High Performance Manufacturing Group of the Faculty of Engineering of Bilbao has a workshop fully-equipped. In this way, these machine tools are valid both to support research carried out by the Group and also to improve teaching lessons, both theoretically and practically. In this paper, the case of a five-axis milling machine was presented and analyzed. Each year, the new students are taught to design various systems of the machine and they are also encouraged to make some practical tests. This dual use of machines is very useful since it allows to carry out high level researches, as well as to train new students in theoretical and practical issues.

Development of a Laser Hardening Simulation Method Including Material Characterization for Rapid Heating Rates

The main disadvantage for industrial application of new processes based on laser surface treatments, such as laser hardening, quenching or precipitation hardening, is the prior experimentation needed to determinate the optimum conditions for processes. The presented work is focused on the development of a tool based on a semi-empirical model to predict accurately the thermal field and thickness of the head affected zone in laser surface treatments in order to avoid the previous experimental setups of this processes. The conventional thermal models are focused on solving the differential equation of temperature field, considering the laser as heat source and thermal properties of each material. However, during the rapid heating treatment processes of metal surfaces are some unknown heat sinks such us metallurgical transformations or a changeable material absortivity that must be taken into account. The model has been adjusted and validated with experimental data for AISI 1045.

Geometry Modelling of Clads Generated by Laser Cladding

The laser cladding process is based on the generation of a melt-pool in a substrate where a filler material is injected, generating a high quality clad with a minimum heat affected zone. This process is industrially used to generate coatings over wear or damaged surfaces, being an alternative to traditional deposition techniques. One of the most important aspects for its industrial application is to know the clad geometry in order to calculate the deposited layer thickness. This work presents a model in which, starting from the concentration of injected material and the melt-pool geometry, clad height is finally estimated. Both input variables are obtained by two previous validated models. On one hand, the melt pool is estimated by a thermal model based on the finite difference method, and on the other hand, concentration of injected material is provided by a particle concentration CFD model. This data is used in a mass balance over melt-pool area in order to estimate the deposited clad height.

Parameter Study on Laser Surface Finishing with 2D Scan Head

In recent years laser polishing is becoming an alternative for automated surface finishing of dies and molds. This process involves melting and subsequent solidification of the material. Depending on the initial topography, the energy density necessary to reduce surface asperities can cause excessive heat damage, and thus, limit the applicability of the process. The work presented here focuses on the use of a high quality laser beam, with a spot diameter below 50 microns driven by a 2D scanner for processing of materials typically used in dies and mold manufacturing. So, the highly focused beam ensures minimal thermal damage, and the scan head allows high productivity rates. A new processing strategy based on two stages surface processing was developed to process topographies with strong directionality.