جستجوی مقالات مرتبط با کلیدواژه « manufacturing » در نشریات گروه « مکانیک »

In this paper, the influence of the geometric parameters of a thrust measurement stand in mN level and for electrical thrusters on its performance is investigated. To measure the thrust of the electrical thrusters, a system must be used that separates the thrust force from the weight force. Thus, thrust measurement systems are designed based on a pendulum. The geometric parameters of a thrust measurement stand, such as the length of arms, the mass of different parts, and the stiffness of pivots affect the overall performance of the system, including its dynamic and static response (for example, displacement, natural frequency and stabilization time of oscillations). For this purpose, primarily, the analytical model for the behavior of a thrust measurement stand with an inverted pendulum configuration is obtained. Then, using the obtained results, the optimal design of several stands is carried out based on the specified physical requirements and using the Genetic Algorithm method. Finally, an experimental thrust measurement stand with a maximum measuring thrust of 100 mN is developed based on obtained specifications from the optimization and by validating the results of the analytical model, the error of the model is estimated to be less than 6 percent.

In recent years, linear electromagnetic actuators have gained special attention in small robot actuation and calibration of milli newton thruster stands. In this paper, a linear electromagnetic actuator with a force range of milli newtons is designed and manufactured. In this regard, first the analytical relationships of the magnetic field and Lorentz force were derived and then, based on the desired design criteria meaning high force sensitivity, low heat loss and minimum geometric dimensions and weight, the appropriate design parameters of the electromagnetic actuator is obtained. According to the results, the  obtained force constant is approximately 1 mN/A while the maximum power loss is 1 mW at available stroke of 10 mm. Finally, a prototype of the linear electromagnetic actuator is manufactured and experiments are performed to validate the electromagnetic actuator. For this purpose, a precision scale with an accuracy of 0.01 gr and a power supply with a resolution of 1 mA is utilized. The results showed that the maximum difference between the calculated and measured force was 2.5%. Therefore, there is a good correlation between the experimental data and the corresponding analytical values.

Non-circular gears for their ability to create cyclic changes in the velocity and torque of the gears in each revolution employed for various purposes such as robotics, textile, and packaging industries. In this paper, the design methodology of a similar pair of plastic square gears is investigated. The design of gear profiles was performed according to complex mathematical calculations and the three-dimensional model of the gears was designed. Then the assembly of the gears was performed in CAD software and their motion was simulated. The laser cutting process was utilized to manufacture square gears. Examination of the results and the absence of special errors such as the gear's inappropriate meshing during rotation, improper backlash, or the impossibility of assembly due to incorrect dimensions design, indicate the accuracy of the design methodology. Moreover, the use of thin plastic sheets as raw material in the laser cutting process has prevented the laser beam from diverging and technical faults of gear samples. Comparing the angular speed of the driver gear with the lobe number also shows the accuracy of the square gear simulation process.

Process planning and management is a decision that uses limited resources to achieve a specific goal. Therefore, production management can be considered as a decision-making process in the field of production issues, planning, organizing, controlling, directing, or motivating human resources. Because in the industry, to ensure product responsiveness, they first act as a single production and workshop and then as mass production. In the present study, a CAD computer model and a fixture were made for the Peugeot 405 brake pump shell. According to the geometric shape of the sample, casting and machining methods are considered in the production of the product. The restraint was designed and made for the final-machining operation. With the help of planning tables and operations sheets, important product specifications, important process specifications, design plans were controlled and reviewed. The results show high compatibility between the production sample and the prototype of Iran Khodro (IKCO) Company. Due to the high compatibility, it can be claimed that the product produced is at a better level in terms of quality, manufacturing and ultimately cost.

In this research, a transparent PEM fuel cell is designed and manufactured to visualize the anode and cathode side flow channels and study flooding phenomenon in them. Manufacturing challenges are found, and cell design is simulated prior to manufacturing. Restrictions are expressed in the first place and then practical solutions are presented to cope with them; materials and dimensions are then determined accordingly. As the second step, the cell’s operation is simulated and the polarization curve is extracted using a steady-state two-phase computation fluid dynamics model. After the manufacturing of all components, due to the high influence of the torque of the bolts on the leakage, lifetime and operation of the cell, this parameter is optimized using polarization curves. A torque of 1N.m for the bolts is found to be optimum. In order to validate the numerical model, the polarization curve of the model is compared with that of the experiment. An error of 6.76% demonstrates the suitable accuracy of the numerical model. Finally, the accumulated water on the cathode side is detected using direct visualization and image processing technique.

The bobbin tool is a new design of the friction stir welding tool that provides the opportunity of the simultaneous double sided welding. The present research aims to design and manufacture a floating bobbin tool; the capability of which is examined through welding aluminum alloy 6061. The results indicated that the high quality and defect-free butt welds can be produced via this tool. Moreover, the strength of the welds is similar to the strength of welded samples done by the conventional friction stir welding method. Regarding the quality and strength, the obtained samples were investigated by mechanical tests including tensile strength test and hardness test. Obtaining 60.7% joint efficiency is indicative of success in the friction stir welding process; and, thus the efficiency of the designed tool. Besides, the second major characteristic of welding is the hardness, which is due to the dissolution of sediments, is decreased in the stirred area. This finding is confirmed by the behavior reported by the other investigators in the literature.

Parallel manipulators are mechanisms with closed kinematic chains which have been developed in different forms, but these manipulators have several drawbacks such as small workspace, existence of singular points in their workspace, and complex kinematics and dynamics equations that lead to increase of difficulty in their control. In spite of this, this mechanism has been being conventionally used in many different industrial applications such as machining, motion simulators, medical robots, etc. To overcome these drawbacks, design and manufacturing of a manipulator with three translational degrees of freedom are provided. Design of this manipulator was based on the possibility of three translational motions for its end-effector. The manipulator degrees of freedom are obtained via screw theory. Basic features, consisting of forward and inverse kinematics, workspace and singularity analyzes and also velocity analysis, are considered in this paper. A numerical algorithm is implemented to determine the workspace regarding applied joint limitations and the design parameters were extracted based on to achieving to the desired workspace. The robot motion is created by using of pneumatic actuators which receive their command from a pneumatic servo valve. After design steps, the required elements were provided and assembled in a robotic lab. Finally, the simulation results have transparently approved the improved robots.

Although Pulsed Plasma Thruster (PPT) has first been utilized in a space mission in 1964 but after more than four decades, it is still a space rated technology which has performed various propulsion tasks from stationkeeping tasks to three-axis attitude control for a variety of former missions. With respect to the rapid growth in the small satellite community and the growing interest for smaller satellites in recent years, PPT is one of the promising electric propulsion devices for small satellites (e.g. CubeSats) as the following advantages: simplicity, lightweight, robustness, low power consumptions, low production costs and small dimensions. In spite of the fact that the issues relating to 􀈝PPT scaling have been investigated to a certain degree in recent years, it is felt that for an application on CubeSats this topic has to be investigated in greater detail for even smaller dimensions and better performance. Therefore a laboratory benchmark rectangular breech-fed pulsed plasma thruster (PPT) was designed, developed and successfully tested in a bell-type vacuum chamber at 10-6 mbar for the first time in west Asia (Iran). The PPT has been tested while the main capacitor, which is a 35 􀈝F, 2.5 kV oil-filled capacitor, has been charged with a wide range of voltage, ranging from 250 V to 1750 V making the system stored energy range from less than 1 J to 60 J, producing the impulse bit varying from 30 􀈝N-s to 1.3 mN-s. This work initiated a research program in Iran for working on PPTs and miniaturization of PPTs while increasing the performance parameters. The present paper reviews the PPT design and the development briefly.