Measuring workpiece dimensions using a non-contact laser detector system

Proper process control procedures are important considerations in the optimisation of any manufacturing process. Ultimately, a continuous update on the size and quality of the products being manufactured is desirable. A non-contact laser detector system was developed to measure the dimensions of wood products in a real-time operating environment, employing a two-axis lateral effect photodiode as the sensor. Computer algorithms were developed to measure the thickness, warp, and width of wood samples (pencil slats). The effect of mechanical vibration due to slat transport was identified and when possible eliminated. The system was evaluated at different transport speeds. The results indicated that, except for width measurement which is limited by the computing speed, the system can measure thickness and warp quite accurately at feed speeds of 240 feet per minute. Although the work described is specific to certain applications, the implications for use in other industrial activities where visual sensing is required is apparent.     

激光金属沉积成形基板预热温度的控制

为了降低激光金属沉积成形过程中试样和基板间的温度梯度,减小和抑制成形过程的热应力,提高试样的成形质量,提出并设计了一种用于激光金属沉积成形的基板预热系统.其中基板预热温度的控制由智能比例微分积分控制器以及计算机串口温度采集反馈控制来完成.利用自行研制的激光金属沉积成形设备和基板预热系统进行了成形实验,实验结果表明该基板预热系统温度控制良好,可以满足实际应用的需要.     

New kind of subarea-parallel scanning mode for laser metal deposition shaping

A scanning mode is the key technology in a laser metal deposition shaping (LMDS) fabrication process. On the basis of the analysis of existing scanning modes and their influences on the fabrication efficiency and the quality of parts, some disadvantages of them are pointed out. A new kind of subarea-parallel scanning mode for LMDS based on a subdividing profiled outline into monotonous polygon subareas is presented. First, based on the principle of point visibility, inner loops are eliminated, and simple polygons are subdivided into monotonous polygons with the minimal zones. Second, the parallel scanning paths of all monotonous polygon subareas are finished, which diminishes the length of the scanning line. The practical application shows that the scanning mode can enhance the fabrication efficiency and quality. __________ Translated from Chinese Journal of Mechanical Engineering, 2006, 42(10): 170–175 [译自: 机械工程学报]     

激光等离子体软X射线光源的一种诊断方法

激光等离子体软X射线光源是脉冲式光源,对这类光源的光谱诊断有几种方法.文章介绍了一种新的、实用的测量激光等离子体软X射线光源光谱的方法.此方法以低噪声的通道电子倍增器探测来自光源的ns量级的脉冲光信号,并由低噪声、响应快的电荷灵敏前置放大器进一步将其放大,前放的输出电荷与输入的脉冲信号的峰值成正比.使用这种方法测量了铜靶激光等离子体光源和氧、氪气体靶激光等离子体软X射线源在8～30nm波段的光谱.     

Ceramic to metal joining by using 1064 nm pulsed and CW laser energy source

A novel joining method for ceramic and metallic layers is proposed using laser drilling and surface tension driven liquid metal filling. A high intensity laser beam irradiated a 500 μm thick ceramic filter, and the irradiated laser drilled the ceramic layer. The pulsed or CW laser transmitted through the ceramic layer irradiated the bottom metallic layer; the molten metallic layer then filled the drilled ceramic holes by the capillary force between the liquid metal and ceramic layer. As process variables, average laser power, pulse duration, and the number of pulses were used. The scattering optical properties were also studied for both green and red lasers. There was no significant difference between the colors and the estimated extinction coefficients were ?26.94 1/mm and ?28.42 1/mm for the green and red lasers, respectively.     

Improved signal stability from a laser vaporization source with a liquid metal target

The translating and rotating rod or disk of a conventional laser vaporization cluster source is replaced by a liquid metal target. The self-regenerating liquid surface prevents cavities from being bored into the sample by laser ablation. The laser beam strikes a near pristine surface with each pulse, resulting in signals with much better short and long term stabilities. While this approach cannot be used for refractory metals such as tungsten and molybdenum, it is ideal for studies of bimetallic clusters, which can easily be prepared by laser vaporization of a liquid metal alloy.     

A non-contact method for detecting on-line industrial robot position errors using a microwave Doppler radar motion detector

To be useful, industrial robots must meet positioning accuracy requirements for their given applications. Off-line calibration generally improves robot positioning accuracy to levels needed for open-loop use in most industrial applications. Applications that require greater accuracy with respect to external assemblies generally turn to closed-loop control or passive compliance. However, industrial robot systems do not generally monitor in-process robot position to detect machine faults that can lead to product faults, scrap, machine damage, and additional costs. To achieve greater operational efficiencies, new non-invasive, non-contact methods for monitoring robot position are needed. The investigators developed a low-cost method for in-process industrial robot position monitoring using a Doppler motion detector and a statistical position error measure. The method detects position errors at robot repeatability levels.     

A non-contact method for detecting on-line industrial robot position errors using a microwave doppler radar motion detector

To be useful, industrial robots must meet positioning accuracy requirements for their given applications. Off-line calibration generally improves robot positioning accuracy to levels needed for open-loop use in most industrial applications. Applications that require greater accuracy with respect to external assemblies generally turn to closed-loop control or passive compliance. However, industrial robot systems do not generally monitor in-process robot position to detect machine faults that can lead to product faults, scrap, machine damage, and additional costs. To achieve greater operational efficiencies, new non-invasive, noncontact methods for monitoring robot position are needed. The investigators developed a low-cost method for in-process industrial robot position monitoring using a Doppler motion detector and a statistical position error measure. The method detects position errors at robot repeatability levels.     

Experimental analysis of sheet metal micro-bending using a nanosecond-pulsed laser

Laser shock bending is a sheet metal micro-forming process using shock waves induced by a nanosecond-pulsed laser. It is developed to accurately bend, shape, precision align, or repair micro-components with bending angles less than 10°. Negative bending angle (away from laser beam) can be achieved with the high-energy pulsed laser, despite the conventional positive laser bending mechanism. In this research, various experimental and numerical studies on aluminum sheets are conducted to investigate the different deformation mechanism, positive or negative. The experiments are conducted with the sheet thickness varying from 0.25 to 1.75 mm and laser pulse energy of 0.2 to 0.5 J. A critical thickness threshold of 0.7-0.88 mm is found that the transition of positive–negative bending mechanism occurs. A statistic regression analysis is developed to determine the bending angle as a function of laser process parameters for positive bending cases.     

A starting device for a metal plasma source

An explosion of a thin self-renewable carbon film is used for initiating an arc in a vacuum-arc metal plasma source, which makes operation of the device independent of the operating mode of the plasma source and allows the circuit of the setup to be simplified, since there is no need for generating high-voltage triggering pulses. The service life of this device in vacuum is more than 10⁵ triggering pulses.     

Nd:YAG激光器金属零件激光快速成型工艺研究

利用Nd:YAG1.1kW激光器和同轴送粉方式进行了金属零件激光快速成型工艺实验研究.叙述了激光快速成型制造系统的基本组成和实验方法;分析了主要工艺参数如:激光功率、扫描速度、送粉量以及Z轴增量对成型质量和形貌的影响.给出了在最佳工艺参数下得到的激光成型实例.     

A method for forming a single metal nanowire using track membrane templates

A new electrochemical method for forming single metal nanostructures (nanowires) is described. A standard track membrane with statistically distributed etched high-density channels is used as a template. A few track membranes are stacked in a multilayer sandwich and tightly pressed to each other and to a metal substrate-cathode. Metal is electrochemically deposited into the through etched channels of the track membranes. Since the probability of statistically distributed etched through channels in a sandwich of track membranes being butted together is rather low, etched channels with electrochemically deposited metal decrease in number in each subsequent track membrane, beginning with the substrate-cathode, until a single nanostructure is formed in the top track membrane.     

A study of H+ production using metal hydride and other compounds by means of laser ion source

A laser ion source can provide wide variety of ion beams from solid target materials, however, it has been difficult to create proton beam efficiently. We examined capability of proton production using beeswax, polyethylene, and metal hydrides (MgH(2) and ZrH(2)) as target materials. The results showed that beeswax and polyethylene could not be used to produce protons because these targets are transparent to the laser wavelength of 1064 nm. On the other hand, the metal hydrides could supply protons. Although the obtained particle numbers of protons were less than those of the metal ions, the metal hydrides could be used as a target for proton laser ion source.     

High speed milling, electro discharge machining and direct metal laser sintering: A method to optimize these processes in hybrid rapid tooling

Prototype injection moulds for plastic parts must face two constraints: be designed and manufactured as quickly as possible and have a short lead time. Moreover, moulds have to evolve in the same way as the part does, to provide either a new functionality or a variant of this part. The current approach is based on a multi component tooling (hybrid rapid tooling) in order to more easily manufacture each component of the mould and to have a greater reactivity to each product evolution. In this paper, we propose a method to manufacture the mould in multi components. This approach is based on process capability criteria (i.e. topological and geometrical criteria). An industrial example is presented. We will focus on the choice between three processes mainly used in hybrid rapid tooling: high speed machining (HSM), electro discharging machining (EDM) and direct metal laser sintering (DMLS).     

Shot-to-shot reproducibility in the emission of fast highly charged metal ions from a laser ion source

The generation of fast highly charged metal ions with the use of the sub-nanosecond Prague Asterix Laser System, operated at a fundamental wavelength of 1315 nm, is reported. Particular attention is paid to shot-to-shot reproducibility in the ion emission. Au and Pd targets were exposed to intensities up to 5 × 10(16) W∕cm(2). Above the laser intensity threshold of ～3 × 10(14) W∕cm(2) the plasma is generated in a form of irregular bursts. The maximum energy of protons constituting the leading edge of the fastest burst reaches a value up to 1 MeV. The fast ions in the following bursts have energy gradually decreasing with the increasing burst number, namely, from a value of about 0.5 MeV∕charge regardless of the atomic number and mass of the ionized species.     

复杂轮廓表面的线式扫描单目成像测量方法

采用单摄像机和线式激光源,通过使被测物体连续旋转,实现了对复杂轮廓表面的三维非接触测量,并详细说明了数据处理过程.该方法可使测量效率显著提高,测量精度主要取决于被测物体的旋转控制精度和摄像机的分辨率.     

Prototypes using metal, carbon fiber and composite field emission sources modulated by a laser beam.

Field emission of electrons from a variety of metallic, carbon fiber and composite metal-insulator micropoint cathodes was employed in this study. Tungsten, carbon fiber and ZrC tips, were studied using a field emission microscope. These cathodes were characterized and the current-voltage (I-V) characteristics were determined. A variety of surface treatment procedures were carried out to increase the stability of emission. These electron sources were mounted in sealed prototype field emission tubes, while others were tested under medium, high and UHV conditions. The emission current switch-on phenomenon was found with all non-metallic cathodes. The emitters were then subjected to a square wave-modulated, maximally focused laser diode beam (lambda = 658 nm, 30mW). The beam impedance (approximately 1 Gohms) and the anode capacitance (approximately 10 pF) act as a low-pass filter.     

Statistical analysis of a method for monitoring fibre outside diameter using dual beam of edge diode light

Results of studies of the metrological feasibilities of an optical method of filament diameter measuring are presented. The analysis is based on statistical approximation of the experimental results. Systematic and random contributions to the total measurement error are estimated, and are equal to −0.15 μm and +0.15 μm, respectively, in the acceptable range of fibre lateral displacement equal to about 1 mm. Resolution of the method is about 0.05 μm.