Wire Arc Additive and High-Temperature Subtractive Manufacturing of Ti-6Al-4V

We investigated the fabrication and finishing of wall-profile machining by wire and arc additive manufacturing (WAAM) employing plasma welding with Ti-6Al-4V wire. We fabricated and integrated a local shield and a cover for the area below the local shield to achieve higher shielding ability. The tensile strength of the fabricated object met the forging standard for Ti-6Al-4V, but elongation was about 7%. We also focused on the possibility of reducing the cutting force and increasing the efficiency of the finishing process by cutting workpieces softened by high temperature immediately after the deposition process. We investigated the cutting force and tool wear of the fabricated objects heated to 300 °C using ceramics tools. Results showed that although the cutting force was reduced at high temperature, the wear rate of the tools was high, and the increase in cutting force due to wear was significant.

In-Process Monitoring of Changing Dynamics of a Thin-Walled Component During Milling Operation by Ball Shooter Excitation

During the milling of thin-walled workpieces, the natural frequencies might change radically due to the material removal. To avoid resonant spindle speeds and chatter vibration, a precise knowledge of the instantaneous modal parameters is necessary. Many different numerical methods exist to predict the changes; however, small unmodelled effects can lead to unreliable results. The natural frequencies could be measured by human experts based on modal analysis for an often interrupted process; however, this method is not acceptable during production. We propose an online measurement method with an automatic ball shooter device which can excite a wide frequency range of the flexible workpiece. The method is presented for the case of blade profile machining. The change of the natural frequencies is predicted based on analytical models and finite element simulations. The measurement response for the impulse excitation of the ball shooter device is compared to the results of impulse modal tests performed with a micro hammer. It is shown that the ball shooter is capable of determining even the slight variation of the natural frequencies during the machining process and of distinguishing the slight change caused by different clamping methods. An improved FE model is proposed to include the contact stiffness of the fixture.

Hybrid Edge–Cloud-Based Smart System for Chatter Suppression in Train Wheel Repair

The contact profile of a train wheel has a key role in its operation performance. Rolling smoothly and with reduced resistance results in an increase in the efficiency and safety of rail transport. The original shape and dimensions of the profile of the wheel are altered under operation of the train, especially due to braking events and the presence of external objects between the wheel and the railway. With the purpose of recovering the optimum contact profile, train wheels are periodically machined using special lathes. This repair operation is particularly critical in freight trains, which are only reshaped a few times throughout their service life and, therefore, high depths of cut are required to recover the wheel in a productive way. As the presence of chatter vibrations limits the productivity of these operations, a hybrid edge–cloud computing approach has been developed for chatter vibration suppression. An expert system based on automatic chatter detection and suppression has been developed in the edge. The expert system is based on continuous real-time vibration monitoring and combines continuous spindle speed variation (CSSV) and cutting speed reduction to suppress chatter. Cloud computing is used to extract wheel profile machining fingerprints and obtain insights from multiple aggregated machined wheels. An industrial implementation of the system is described in the present work.

Motion Accuracy Enhancement of Five-Axis Machine Tools by Modified CL-Data

The motion trajectories of machine tools directly influence the geometrical shape of machined workpieces. Hence, improvement in their motion accuracy is required. It is known that machined shape errors occurring in numerical control (NC) machine tools can be compensated for by modifying the CL-data, based on the amount of error calculated by the measurement results of the machined shape of the workpiece. However, by using this method the shape errors cannot be compensated accurately in five-axis machining, because the final machining shape may not reflect the motion trajectory of a tool owing to the motion errors of the translational and rotary axes. In this study, a modification method of the cutter location (CL)-data, based on the amount of motion errors of the tool center-point trajectory during the machining motion, is newly proposed. The simulation and experiment of a wing profile machining motion is performed, to confirm the effectiveness of the proposed method. From the results, we confirm that the motion accuracy can be significantly improved by applying the proposed method.

Experimental Study on Profile Machining of Titanium Alloys with Superabrasive Tools

Electroplated profiled superabrasive grinding wheels which integrate both advantages of grinding and profile milling have been widely used in the machining process the wide chord hollow fan blade rabbets made of Ti-6Al-4V alloy. However, the employment of these tools has been impeded by drastic forces and thermal damage. In order to investigate the variation regularities of grinding forces and temperature with different machining parameters, experiments were carried out with single layer electroplated CBN grinding wheels. Grinding forces and temperature were measured and analyzed. Meanwhile, tool life and metallography of workpiece were studied. The results showed that higher spindle speed leads to lower forces and higher temperature. With the increase of feed rate and radial cutting depth, forces and temperature increase. Strong adherence of chips makes abrasives grits blunt which results in the increase of grinding forces after a great deal of tests. Metallographic structure of the machined workpiece is almost identical with the original sample.

Design and implementation of a new statically balanced mechanism for slider-type desktop monitor stands

A desktop monitor stand is a device that supports the weight of a desktop monitor. The statically balanced mechanism within the stand can help the monitor travel to and stop at any different positions, i.e. in a state of static equilibrium at any position. The current statically balanced mechanisms used in the slider-type desktop monitor stands can be classified into two types. The first type integrates a cam and a spring as a statically balanced mechanism for which the cam profile machining could be costly. On the other hand, the second type utilizes a constant-force spring for balancing the weight of the monitor, but the springs must be tailor-made, which costs more. In this paper, a new statically balanced mechanism for slider-type desktop monitor stands is presented. The shown design uses common links and general spring only, which introduces a breakthrough advantage for reducing the manufacturing cost of the monitor stands. Furthermore, the kinematic and force analyses of the proposed design are carried out, and the mechanism dimension is determined via optimization technique. A prototype of the design is made up, and the experimental test in a practical monitor stand is done. As a result, the proposed mechanism can allow the monitor to remain statically balanced at any working position, which proves that the presenting design is practically workable.

Rolling Disk Model and its Application to Tool Path and Envelope Generation for Profile Machining

Tool cutting envelope (TCE) and tool path (TP) for planar profile machining are calculated at the same time in the presented work, using a novel motion method called Rolling Disk Motion (RDM) method. RDM method employs a rolling disk (RD) as the manufacturing tool, and considers the disk running around profile boundaries as cutting process. During this RD motion, RD center locus is just TP for profile or contour-parallel manufacturing strategy. Also, the track of point on RD contracting with the profile is just TCE. Furthermore, the RDM technique can find a further application in the study for uncut areas in machining domains. As well, the calculation of TCE, TP and uncut areas, based on RDM, are finished only by simple point transformations and arcs creation. Finally, an example is included to illustrate TCE and TP computation by means of RDM, and the result shows that the approach is implemented and tested successfully on real-world data.