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result(s) for
"Pramuanjaroenkij, A. (Anchasa)"
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A Standard Procedure for Development Performance Map of CNC Machining Centers by Using Double Ball-Bar
Currently, CNC machining centers have been designed to provide flexibility for a wide range of applications. They are widely used in the metal cutting industry with many advantages; their accuracy, reliability, repeatability, and productivity are the important factors. Generally, for CNC machining centers, the working area of the machine table is larger than the size of the workpiece. In case of machining small workpieces, the operators can produce several workpieces at the same time by setting several fixtures at different positions on the table. This can reduce setup time for cutting a new set of workpieces. However, the performance of a machine varies throughout the workspace. It is thus possible that two finished parts produced from the different positions of the table will have different values in geometric dimensioning and tolerance (GD&T). Therefore, in this study, the researchers developed a new procedure for establishing the performance map of CNC machines. As a result, the operators are able to know which area can produce workpieces with positional tolerances that do not exceed a given threshold. By using a CNC model DMC 635V DECKEL MAHO together with double ball-bar model Renishaw QC10 ball-bar as a case study, experimental results indicated that this procedure can provide a performance map of the machining centers efficiently.
Journal Article
A New Procedure for Determining Minimum Sampling Points for Tolerance Evaluation of High Precision Mechanical Parts
In geometric and dimension tolerance investigations, especially for high precision mechanical parts, the accuracy of measurement is very important. The major equipment for the measurement is the coordinate measuring machine (CMM). However, the recommended strategies for evaluating tolerance values of geometric and dimension cannot be applied with high precision mechanical parts. Hence, in this research, the researcher introduced a new procedure that could evaluate geometric and dimension tolerance values of high precision mechanical parts accurately. This new procedure can determine the minimum sampling point for evaluating geometric and dimension tolerance values by using some performance information on the mechanical parts of the machine. This information was the waviness of the production machine’s motion. In order to evaluate the potential of new procedure, the flatness of test piece was made according to the ISO 10791-7-A160 standard as a case study. This test piece was made from the CNC milling machine (Chevalier 2040 VMC), and the waviness of the CNC milling machine’s motion was counted from the performance testing result measured by the double ball-bar model Renishaw QC10. By comparing flatness obtained by recommended and new procedures, experimental results indicated that the new procedure showed its potential in estimating the flatness.
Journal Article
The Study of Turbulent Nutrient Solution Flows in Difference Hydroponics System Arrangements
This work studied the turbulent flow of the nutrient solution which affected the growth of plants in four hydroponic systems; the horizontal (traditional), the vertical cup-grown, the ladder and the droplet systems, which were connected with individual solution pumps which submerged in only one nutrient solution tank to supply the turbulent nutrient solution flow to all systems. Two experiments were done by planting Red Oak lettuce, fluid and ambient temperatures, fluid pH and sunlight intensity were measured 2 times a day from 4 systems placed in the same area and environment during 20 days of the experimental periods. From both result sets, the lower ambient and solution temperatures in the 2nd experiment yielded more productivity. The results also showed that adjusting pipe and hose sizes did not cause the nutrient solution overflow out of the systems, the turbulent flow occurred and the horizontal system could produce the highest productivity. However, the higher pump power was required to produce the turbulent solution, the higher pump power higher heat transfer from the pump to the nutrient solution in the tank since all pumps were placed in the same solution tank, this heated solution caused the lower productivity in this work.
Journal Article
The Study of Fluid Flows in Difference Hydroponics System Arrangements
This work studied fluid flow in the hydroponics systems to create 4 prototypes of the hydroponics systems; horizontal (traditional), inclined-flow, vertical-droplet and vertical-bowl systems, for a household application with initial conditions as low investment cost and easy installation. Red Oak was used to plant in all prototypes to investigate the prototype productivity. Fluid in the experimental investigation was the plant nutrient solution. All variables; fluid and ambient temperatures, fluid pH and sunlight intensity were measured 2 times a day from 4 systems placed in the same area and environment during 15 days of the experimental period in July 2013,. From results, the solution temperatures affected the productivity less than the fluid flow patterns did. The vertical-droplet system could not be used to grow Red Oak because the plants died during the experiment period. The vertical-bowl system could provide the highest productivity. We noticed that the fluid in the vertical-bowl system flowed transitionally while the flow in the other systems was laminar. Therefore, the fluid flow patterns could affect the productivity in the hydroponics systems.
Journal Article
Mathematical analysis of planar solid oxide fuel cells
The mathematical analysis has been developed by using finite volume method, experimental data from literatures, and solving numerically to predict solid oxide fuel cell performances with different operating conditions and different material properties. The in-house program presents flow fields, temperature distributions, and performance predictions of typical solid oxide fuel cells operating at different temperatures, 1000°C, 800°C, 600°C, and 500°C, and different electrolyte materials, Yttria-Stabilized zirconia (YSZ) and Gadolinia-doped ceria (CGO). From performance predictions show that the performance of an anode-supported planar SOFC is better than that of an electrolyte-supported planar SOFC for the same material used, same electrode electrochemical considerations, and same operating conditions. The anode-supported solid oxide fuel cells can be used to give the high power density in the higher current density range than the electrolyte-supported solid oxide fuel cells. Even though the electrolyte-supported solid oxide fuel cells give the lower power density and can operate in the lower current density range but they can be used as a small power generator which is portable and provide low power. Furthermore, it is shown that the effect of the electrolyte materials plays important roles to the performance predictions. This should be noted that performance comparisons are obtained by using the same electrode materials. The YSZ-electrolyte solid oxide fuel cells in this work show higher performance than the CGO-electrolyte solid oxide fuel cells when SOFCs operate above 756°C. On the other hand, when CGO based SOFCs operate under 756°C, they shows higher performance than YSZ based SOFCs because the conductivity values of CGO are higher than that of YSZ temperatures lower than 756°C. Since the CGO conductivity in this work is high and the effects of different electrode materials, they can be implied that conductivity values of electrolyte and electrode materials have to be improved.
Dissertation