4-Axis CNC Machine Tool for Relief Grinding Sphere Gear Hob
A new 4-axis machine tool, which is used for relief grind of sphere gears hob including spherical hob, elliptic hob and arc surface hob, is developed. The principle of relief machining of spherical hob is introduced first. Transmitting system, numerical system and some key techniques are then introduced. The machine tool can be reconfigured in machining of arc worms and spatial cams beside of machining of spherical hob. Four forms of the machine tool for machining different workpiece are also introduced. DOI: http://dx.doi.org/10.11591/telkomnika.v10i7.1557
Design of Lighting System for Surface Mine Projects
Indian mining illumination standard is based on incident light without mentioning about uniformity ratio. But CIE (International Commission on Illumination, Austria) stresses upon uniformity ratio as well. In a mine because of low surface reflectance, the surrounding illumination level is much lower than the minimum lighting standard, as specified by various regulatory bodies. The surface brightness further reduces in wet surface condition, resulting in poor visibility. In the present study, design has been made both in mineral and overburden benches based on minimum acceptable reflected light and reflected uniformity ratio. For the sake of comparison of various types of lighting systems, a stretch of 1.0 km long haul road was considered and design was attempted with five different types of luminaries. Lamp mounting heights have been varied at five steps, namely 8, 10, 12, 14 and 16 m. Design under wet condition would incur an excess cost of about 9.4 % for mineral bench and about 50 % for overburden bench haul roads under study. Thus designing under wet surface condition would ensure minimum light level even under worst condition of surface reflectivity, with marginal increase in cost.
Failure analysis for poor solderability of Au surface of PCB
Nonwetting is one of the common problems and is always rejected in electronic assemblies. ENIG pads of a PCBA exhibited nonwetting after lead-free reflow soldering. With the aid of stereomicroscope, SEM&EDS and XRF, a series of analysis was performed. And after visual inspection, surface and cross section analysis, thickness measurement and solderability test, it can be inferred that oxidation of plating surface was the main reason for nonwetting, and corrosion in Ni plating caused an adverse impact on solderalibity.