Study of the heat transfer and analysis of the surface characteristics of robot spray painting by using Taguchi method and ANOVA analysis

In this investigative research work, the surface characteristics of normal paint and multiwall carbon nanotube (MWCNT) paint-coated substrates are studied. The experiments are conducted using ABB IRB 1410 Robot and the end effector of the robot is retrofitted with a high-volume low-pressure atomizer paint spray gun. The nanopaint is prepared by ultrasonication by placing 1 gram of MWCNT in a polyurethane commercial base paint (500 ml). Taguchi design of experiments is used to identify the most efficient use of procedure parameters using the L9 orthogonal array table. Heat transfer of the substrate is found by temperature measurements of the convective heat transfer through extended surfaces. Surface morphology is studied by scanning electron microscope and upright microscopy. Analysis of variance technique is used to find the most influencing input parameters and contribution of values to maximizing surface finish and minimizing the heat transfer effect. The study shows that there is an enhancement in surface finish and minimization of heat transfer in the nanopaint coated substrate when compared with normal paint application using the ABB robot.

Toluene and Heavy Metals in Small Automotive Refinishing Shops and Personal Protection of the Workers in Nakhon Si Thammarat, Thailand

Chemical contamination and safe work practices of workers in automotive refinishing shops have been extensively studied in industrialized countries, but the evidence in developing countries is limited. This study aimed to evaluate chemical contamination and the use of personal protective equipment (PPE) of workers in local small-scale automotive refinishing shops in Nakhon Si Thammarat, Thailand. Airborne toluene and heavy metals, i.e., lead, chromium, and cadmium, were measured in 3 automotive refinishing shops. Toluene exposure assessed by urinary hippuric acid (n = 27) and metal contamination on workers’ hands (n = 24) were also determined. Information on the use of PPE and personal hygiene practices of the workers was collected by questionnaires. Average ambient levels of toluene (0.04–18.26 ppm) and the metals (Pb: ND-26.34, Cr: 0.02–4.46, and Cd: ND-1.44 µg/m3) in all sites did not exceed the national standard levels of 200 ppm for toluene (1998) and 50, 12, and 5 µg/m3 for Pb, Cr, and Cd, respectively (2017). The mean ambient levels of these chemicals were highest in paint spray booths followed by nonpainting areas and office rooms, respectively. The highest level of urinary hippuric acid (1.13 g/g creatinine) was found in a painter but did not exceed the recommended biological exposure index of 1.6 g/g creatinine (2014). In contrast, the highest levels of lead and chromium detected on the workers’ hands were found in body repair technicians. Direct hand contact without using gloves was suggested as a primary cause of metal contamination.

Filtration Performance Characteristics of Sticky Aerosol Using Calcium Hydroxide

This study examined the performance of removing aerosol upon a flow rate variable by agglomerating sticky aerosol with calcium hydroxide and removing cohesive aerosol through an experimental apparatus, simulating an actual painting booth. As a result of examining the performance of the filter by fixing the paint spray quantity, the calcium hydroxide input and the filtration area under variable flow rates of 5, 10, and 15 Nm3/min, we confirmed that the filter performance has long average aerosol removing intervals at the 5 Nm3/min flow rate. At the 5 Nm3/min flow rate, there is a low residual pressure drop trend and high fractional collection efficiency, and a high level of total collection efficiency is maintained at 99.42%. When the flow rate is less than 5 Nm3/min, the aerosol settling and experimentation was impossible. With this research, the optimal conditions for the use of sticky aerosol have been examined.

Effects of automotive paint spray technology on the paint transfer efficiency – a review

Automotive spray painting is among the most sophisticated and controlled industrial painting operations currently performed. Nevertheless, improvements in it are still sought in efforts to minimize the costs, the energy use and the environmental impacts. One compelling aspect of improvement is the paint transfer efficiency, i.e. the amount of paint that remains on a vehicle relative to the amount supplied to the paint applicator during coating operations, because currently it has been estimated that the overall paint transfer efficiency in the automotive industry is between 50% and 60%. Hence, this review assesses current automotive spray coating technologies with respect to their transfer efficiencies and discusses the fundamental and operational parameters that influence it. A comprehensive characterization of paint spray applicators (air sprayers, high-volume low-pressure sprayers, airless sprayers, air-assisted airless sprayers, rotary bell atomizers, electrostatic sprayers, and effervescent atomizers) is included. Some problems associated with evaluating and improving their paint transfer efficiencies are discussed. Also, the potential of and the technology needs for developing these applicators are considered.