Leon Lobo

The effect of laser processing parameters on the particulate generated during the cutting of thin mild steel sheet

Abstract Monitoring of the particles formed during carbon dioxide laser cutting of thin (2 mm) mild steel plate was undertaken to investigate the effect of processing parameters and melt removal mechanisms on the cut quality. The airborne particles (< 40 μm) formed during cutting were captured and the particle diameter distribution was measured using a laser diffraction method and examined using scanning electron microscopy (SEM) analysis. The particles formed were spherical and found to range from micrometres to millimetres in diameter with a monomodal distribution for the airborne fraction. It was found that the airborne micrometre particle diameter range had a mean particle diameter that was directly related to the process quality measurands of cut edge surface finish, cut width and heat-affected zone (HAZ) width.

An optical method for automated roadside detection and counting of vehicle occupants

Abstract The monitoring and control of traffic volume is becoming a constant social, economic, and environmental pressure in the UK and elsewhere, because of landmass and current infrastructure strain under a swelling and increasingly mobile population. The viability of high-occupancy vehicle (HOV) lanes for easing traffic congestion, and hence maximising traffic flow, has been proven in countries worldwide. The USA, Australia, and Canada have had HOV installations for some time, controlling the flux of traffic into their most densely populated areas. Experience in these cases has dictated that it is enforcement which is crucial to the successful implementation of such a traffic policy. To date, all enforcement has been manual, i.e. a police officer counting the occupants in a vehicle as it passes by. Studies have concluded that manual enforcement is typically only 65 per cent accurate and, considering the pressures which one individual is put under in these circumstances, this statistic is not surprising. Lighting and environmental conditions, skin tone, and location of the occupants and the alertness of the officer are all variables affecting the accuracy of manually collected data. Hence there is the need for an autonomous detection system to count the occupancy within a vehicle. This could provide the basis of an enforcement or congestion strategy.

The use of laser induced processing fume as a process measurand in the feedback control of laser cutting

An investigation of the particulate generated during high power CO2 laser cutting of mild steel sheet was undertaken. The ejected particulate was analysed for particle size distribution, shape, and surface features. The particles ranged in size from sub-µm to millimeters across. Many are spherical, hollow and thin-walled causing a significant fraction to remain airborne. The investigation of the concentration of the airborne fume and its correlation with process parameters such as laser power, cutting velocity and assist gas pressure was studied. It was found that the concentration of airborne particulate is at a maximum at the optimum value of power-to-velocity ratio for a particular workpiece thickness. Essentially, the concentration of the airborne particulate increases with increasing cut quality. This relationship can provide a basis for a process control system.An investigation of the particulate generated during high power CO2 laser cutting of mild steel sheet was undertaken. The ejected particulate was analysed for particle size distribution, shape, and surface features. The particles ranged in size from sub-µm to millimeters across. Many are spherical, hollow and thin-walled causing a significant fraction to remain airborne. The investigation of the concentration of the airborne fume and its correlation with process parameters such as laser power, cutting velocity and assist gas pressure was studied. It was found that the concentration of airborne particulate is at a maximum at the optimum value of power-to-velocity ratio for a particular workpiece thickness. Essentially, the concentration of the airborne particulate increases with increasing cut quality. This relationship can provide a basis for a process control system.