Evaluating the Effects of Milling Speed and Screen Size on Power Consumed During Milling Operation

This study was conducted to evaluate the effect of rotor speed and screen size on power consumed during milling operation. The milling system was tested using three fish feed ingredients; bone meal, groundnut cake and maize. The moisture contents of the ingredients bought from the market are 13.1%, 14.7% and 17.5% dry basis, respectively. The milling machine was evaluated with the 3 kg of each feed ingredient and was replicated three times for each of the experimental parameters. The machine parameters varied during the experiment includes four screen sizes (1.5 mm, 2.0 mm, 2.5 mm and 3.0 mm) and five rotor speeds (1500 rpm, 1800 rpm, 2100 rpm, 2400 rpm and 2700 rpm). Regression analysis was carried out on the data collated. The analysis was used to develop a model which is capable of predicting the electrical energy (kJ) consumed. There was no significant effect of screen size on the average power consumed during milling since there is no linear relationship between power consumed and screen size. However, there is a significant effect of speed on average power consumed, the power consumed increases as speed decreases therefore making milling operation at higher speed to be cost effective since it doesn’t require much power to achieve the required output. The P-Value depicts that screen size has no significant effect on the electrical energy consumed during the milling operation while speed has a significant effect on the electrical energy used at 95% confidence level.

Design and fabrication of low-cost micromachining system for prototyping printed circuit boards

Printed circuit boards (PCBs) have a portentous position in constructing modern electronic equipment. Currently, chemical etching is the process used to produce PCBs at huge volumes, which is not suitable for preparing prototypes. The working environment is also not an encouraging one. There is no economical way to manufacture PCBs in low volumes, which is the basic requirement for Small and Medium Scale Enterprises (SMEs). Prototyping the desired circuit boards, prior to the mass production, is essential to avoid major losses by producing faulty designs. Developing a low-cost machine for prototyping PCBs may overcome these drawbacks. Hence, in this work, a machine capable of performing PCB mechanical milling operation on wide range of materials like copper/epoxy boards and flexible substrates has been developed. The machine developed is capable of milling lines that are 0.3 mm in width and 0.46 mm in depth. The performance of the machine reveals that it can mill any complex shapes and designs with expected accuracy. Selection of hardware components according to the needs would reduce the cost and programming snag further, which makes it affordable to SMEs.

Comparative studies of variation in cutting conditions and cutter nomenclature on the surface morphology and the integrity of slot milled nimonic 263 alloy

Cutter nomenclature and machining conditions has invoke critical impact on the machining behavior and surface integrity of machined samples. In this investigation, the slot milling operation has been performed under various cutter terminology or nomenclature (cutter with the RRA of −7°, 0° and 7°) and cutting conditions (spindle speed, table feed and MQL flow rate) to analyze its resulting outcome on the surface morphological features such as surface roughness (Sa), skewness (S sk ) and kurtosis (S ku ), etc Because the examination of these characteristics are important and significant to analyze the behavioral changes of asperities such as decohesion, wear resistance and adhesion, etc during in its relative motion. Additionally, the plasticity index and surface morphology of machined samples are helps to predict the variation in surface morphology under various machining behavior and through this study, it is found that the interactive effect of MQL flow rate and table feed offer higher and significant impact over the surface characteristics followed by the MQL flow rate during slot milling process.

Optimising Depth Selection on Section Milling Operation to Secure Sustained Casing Pressure During Plug and Abandonment Operation

D-01 was an exploration well requiring a Plug-and-Abandonment (P&A) procedure with sustained casing pressure up to 2,000 psi on the B annulus. The presence of Sustained Casing Pressure (SCP) is one of the major technical challenges to decommission and abandon the well safely. Several attempts to secure the well using the perforation-and-squeeze method were performed – but failed. It was decided to perform section milling operations to create a viable rock-to-rock barrier. In this operation, the key factor in determining success, is selecting the correct depth to mill safely and secure the annular pressure source. A comprehensive approach was taken to determine the optimum depth for the section milling by evaluating existing open-hole and cased-hole data. Additionally, triple-detector Pulsed Neutron Log (PNL) was also performed prior to the section milling operation. The triple-detector PNL tool offered not only behind casing porosity (TPHI) and sigma (SIGM) measurement, but also a relatively new measurement in the oil and gas industry called Fast Neutron Cross Section (FNXS), which were expected to provide more accurate gas detection and gauge the condition near the borehole. By combining all the logs and reservoir data, the milling interval was selected and the section milling and subsequent cement plug operations were performed. Evaluation of existing open-hole and cased-hole logs provided geological and petrophysical insights which were useful in determining the hydrocarbon source charging the B-annulus. Further analysis on PNL data provided indication of possible gas pockets in the B-annulus. This information was used to distinguish between shallower formation sources or gas pockets that were not yet bled off. The operation on D-01 successfully resolved the B-annulus issue and the well was properly abandoned per regulatory requirements. Considering the complexity and high cost of section milling operations, a thorough review of data and pre-job logging increases the probability of selecting the optimum intervals needed to successfully complete P&A operations on SCP wellbores.

Failure mechanics analysis of AISI 4340 steel using finite element modeling of the milling process

A slot cutting operation is studied in this paper using a rotating/translating flat end milling insert. Milling operation usually comprises up-milling and down-milling processes. These two types of processes have different behaviors with opposite trends of the forces thus making the operation complex in nature. A detailed Finite Element (FE) model is proposed in this paper for the failure analysis of milling operation by incorporating damage initiation criterion followed by damage evolution mechanism. The FE model was validated with experimental results and good correlations were found between the two. The failure criteria field variable (JCCRT) was traced on the workpiece to observe the amount and rate of cutting during the machining process. It was found that the model was able to predict different failure energies that are dissipated during the machining operation which are finally shown to be balanced. It was also shown that the variation of these energies with the tool rotation angle was following the actual physical phenomenon that occurred during the cutting operation. Among all the energies, plastic dissipation energy was found to be the major contributor to the total energy of the system. A progressive failure analysis was further carried out to observe the nature of failure and the variation of stress components and temperature occurring during the machining process. The model proposed in this study will be useful for designers and engineers to plan their troubleshooting in various applications involving on-spot machining.