Stitching(new) (better)
Industrial stitching and stapling are similar operationsinvolving the use of U-shaped metal fasteners.Stitching is a fastening operation in which a stitching machine is used to form U-shaped stitches one at a time from steel wire and immediately drive them through the two parts to be joined.The parts to be joined must be relatively thin, consistent with the stitch size, and the assembly can involve various combinations of metal and nonmetalmaterials. Applications of industrial stitching include light sheet-metal assembly, metal hinges, electrical connections, magazine bindig, corrugated boxes, and final product packaging. Conditions that favor stitching in these applications are high-speed operation, elimination of prefabricated holes in the parts, and fasteners that encircle the parts are desired.
(Fundamentals of modern manufacturing:materials,models and systems 4th edition, P.Groover, p.775)
2)Tee Joint (welding) (manufacturing method) (better)
Joints where the pieces come together at right angles to each other are called tee joints.A tee joints has welding surfaces areas (fusion faces) in close proximity to each other and more area for heat to dissipate to than any other basic joint.That is why tee joints require more heat for proper fusion and good welding than the other joints.Turn up your heat when appliying a fillet weld to a tee joint.
There are joints that needs as much heat as a tee joint, such as theroot pass of a V-groove weld with a 1/4-inch root opening and backing plate.Welding this first pass requires more heat for the same reason a tee joint does- the close proximity of multiple fusion faces on the joint.
( Todd Bridigum, How To Weld, p.47)
Tee Joint(new)
The tee joint is made by tack welding one piece of metal on another metal at a right angle. After the joint is tack welded together, the slag is chipped from the tack welds. If the slag is not removed, it cause a slag inclusion in the final weld.
The heat is not disturbed uniformly between both plates during a tee weld. Because the plate that forms the stem of the tee can conduct heat away from the arc in only one direction, it will heat up faster than the base plate. Heat escapes into the base in two directions. When using a weave pattern, most of the heat should be directed to the base plate to keep the weld size more uniform and help prevent undercut.
A welded tee joint can be stong if it is welded on both sides. Even without having deep penetration.The weld will be as strong as the base plate if the size of the two welds equals the total thickness of the base plate. The weld bead should have a flat or slightly concave appearance to ensure the greatest strength and efficiency.
(Welding: principles and applications, Larry F. Jeffus, p.94)
The capacity bill procedure is a rough-cut method providing more-direct linkage between individual end products in the MPS and the capacity required for individual work centers. It takes into account any shifts in product mix. Consequenty, it requires moredata then the CPOF procedure. A bill of materials and routing data are required, and direct labor-hour or machine-hour data must be available for each operation.
(Vollman, Berry, Whybark, Jacobs; Manufacturing Planning and Control for Supply Chain Management; pg 341)
Bill of Capacity(new)(better)
A bill of capacity indicates total standart time required to produce one end product in each work center required in its manufacture. The capacity requirements at individual work centers can be estimated by multiplying the capacity bills by the MPS quantities. Estimates obtained from the OF method are based on an overall historical ratio of work between work centers, whereas capacity bill estimates reflect the actual product mix planned for each period.
(Encyclopedia of production and manufacturing management, Paul M. Swamidass, p.74)4)Due Date Tightness (scheduling)
Due Date Tightness(new) (better)
In order to obtain good schedules, the value o K (also called the look-ahead parameter) must be appropriate for the particular instance of the problem. This can be done by first performing a statistical analysis of the particular scheduling instance under consideretion. There are several statistics that can be used to help characterize scheduling instances. The due date tightness factor θ1 is defined as:
Where d is the average of the due dates. Values of θ1 close to 1 indicate that the due dates are tight and values close to 0 indicate that thhe due dates are loose. The due date range factor θ2 is defined as:
A high value of θ2 indicate a wide range of due dates, while a low value indicates a narrow range of due dates. A significant amount of experimental research has been sone to establish the relationships between the scaling parameter K and the θ1 and θ2.
(Planning and Scheduling in Manufacturing and Services,Michael Pinedo, p.446)
5)Accelerometer (sensor)
An accelerometer uses the inertia of a mass to measure the difference between the kinematic accelaration with respect to inertial space and the gravitational acceleration. There are several principles that can form the basis for the design of an accelerometer. One of the first successful accelerometers used a rate gyro mounted as a pendulum mass. In more recent versions a rate gyro is used with a mass offset on the float. Another design is based on the inertia of a proof mass inside a low friction case, and a third is based on the difference in vibration of two thin metal tapes suspended inside a case with a proof mass suspended between them. In later designs the proof mass is suspended from double tuning forks fabricated on quartz substrara. Each type of accelerometer is described in terms of its fundamental component parts and a simplified version of its output equation.
(Fundamentals of High Accuracy Inertial Navigation, Chatfield, Volume 174, p68)
Accelerometer(new) (Better)
Accelerometers measure acceleration using a mass suspended on a force sensor, as shown in Figure 23.12. When the sensor accelerates, the inertial resistance of the mass will cause the force sensor to deflect. By measuring the deflection the acceleration can be determined. In this case the mass is cantilevered on the force sensor. A base and housing enclose the sensor. A small mounting stud (a threaded shaft) is used to mount the accelerometer.
Accelerometers are dynamic sensors, typically used for measuring vibrations between 10Hz to 10KHz. Temperature variations will affect the accuracy of the sensors.Standard accelerometers can be linear up to 100,000 m/s**2: high shock designs can be used up to 1,000,000 m/s**2. There is often a trade-off between a wide frequency range and device sensitivity (note: higher sensitivity requires a larger mass). Figure 23.13 shows the sensitivity of two accelerometers with different resonant frequencies. A smaller resonant frequency limits the maximum frequency for the reading. The smaller frequency results in a smaller sensitivity. The units for sensitivity is charge per m/s**2.
(Automating Manufacturing Systems with PLCs, Hugh Jack,p.546)
No comments:
Post a Comment