TY - JOUR 
A1 - Gil Cano, Jesús
T1 - Method of measuring the water jet diameter : Método de medida del chorro de agua
Y1 - 2013
UR - http://hdl.handle.net/10317/3483
AB - Abrasive Water Jet (AWJ) machining is one of the manufacturing technologies with highest market growth. It is a process in which material is removed from a work piece using mineral abrasive particles. Due to this principle, AWJ machining technology produces significant amount of waste products that consists mainly on the mineral abrasive. It is possible to cut softer materials with pure water jet (WJ), but efficiency is then reduced. In order to increase the efficiency of the WJ machining and to make the process more sustainable than AWJ, the Ice Jet (IJ) technology was developed. The IJ technology aims to supplement the currently used AWJ technology in several applications. Unfortunately addition of liquid nitrogen to a high-speed water jet can cause dispersion of the jet and consequently reduction of cutting efficiency.
Previous experiments in the field of jet diameter measurement have been done by different research groups. In this thesis these methods and the results from the studies based on them, were described and analyzed. This state of the art analysis gave us the knowledge to begin the research on our new method. It also showed that due to possible implementation in industry applications, a quick, easy and affordable technique would be useful. For this reason the phenomenological analysis method to measure the diameter of the water jet was explored. The new method combines digital image acquisition and processing with digital manipulation of the photography. The main advantages of such method are that the equipment can be cheap and as the method is contactless, it doesn‟t get destroyed over time. The analysis of the jet can be automatized and the time of the analysis is short. This means that the method could be applied in the production line to measure the wear of the nozzles during the production cycle without causing any delays. This would increase the lifetime of the nozzles, decreasing the production costs and through online modification of the process parameters also its quality.
During the experiments several process parameters such as water pressure, water temperature and diameter of the water nozzle were modified. In order to verify of the new measurement method, the results were compared with results from another method that has already been established before. Therefore the results from gained from this method served as the reference used to evaluate the new method. The reference method measures the jet diameter through the measurement of the jet force. The experimental setup was built in order to evaluate new measurement method and to compare the novel photographic method with the method which makes use of the load cell to measure the WJ diameter. Setup was built on the machine for ice jet experiments. To illuminate the jet, two high performance light emitting diodes (LED) were used and a consumer digital single lens reflex (DSLR) camera was used to capture the images. In order to make the image acquisition as constant as possible a microcontroller was used to control the LEDs and to trigger the DSLR. Simultaneously a measurement set of WJ force has been made with the load cell. The focus of this work has been on the photographic method. Measurements with load cell were used for validation of the novel method only.
During the experiments two water nozzles were used, five different standoff distances, three different water pressures and three different water temperatures. Regarding photography two different shutter speeds were used throughout all the experiments. Preliminary several combinations of shutter speed and light intensity has been tested in order to obtain optimal experimental conditions. Evaluation of results was performed in the Matlab software package. More than one thousand images were processed by fitting a custom function to the specific rows of image. Function was Gaussian with additional quadratic, linear and constant term. Function was fitted to five image rows which correspond to five different standoff distances from the water nozzle. At the precisely same distances also radial dependence of WJ force was measured. It was found, that the method using digital camera and computer evaluation of image can yield good results which are in good correspondence with measurements of WJ diameter obtained by the load cell.
KW - Organización de Empresas
KW - Abrasive water jet
KW - Manufacturing technologies
KW - Chorro de agua
KW - Método de medida
LA - eng
ER -