Computer-controlled machines

In order to use the stopped-flow technique, the reaction under study must have a convenient absorbance or fluorescence that can be measured spectrophotometri-cally. Another method, called rapid quench or quench-flow, operates for enzymatic systems having no component (reactant or product) that can be spectrally monitored in real time. The quench-flow is a very finely tuned, computer-controlled machine that is designed to mix enzyme and reactants very rapidly to start the enzymatic reaction, and then quench it after a defined time. The time course of the reaction can then be analyzed by electrophoretic methods. The reaction time currently ranges from about 5 ms to several seconds. 

The most advanced machine vision systems typically involve acquisition and interpretation of three-dimensional information. These systems often require more sophisticated illumination and processing techniques than one- and two-dimensional systems, but their results can be riveting. These scanners can characterize an object s shape three-dimensionally to tolerances of far less than a millimeter. This allows them to do things such as identify three-dimensional object orientation (important for assembly applications), check for subtle surface deformations in high precision machined parts, and generate detailed surface maps used by computer-controlled machining systems to create clones of the scanned object. 

Automated manufacturing is the general term for computer-controlled machine tools and robots in manufacturing. 

The scenario of the entire computer controlled machining system is shown by Figure 6-11. The machine tool and machining process are described in a model space with coordinates Ym, and Zm- For programming, a local coordinate system is applied with coordinates Xp, Yp, and Zp. The machine tool has five simultaneously controllable axes X, Y, Z, Q. Part coordinates are transformed into controlled coordinates automatically. The... 

Computer controlled machines allow the precise placement of tapes of prepreg and eliminate problems associated with hand operations. 

The mask image is transferred to the wafer using a computer-controlled machine known as a stepper. It has a sophisticated lens system to reduce the pattern on the mask (millimetres-centimetres diameter) to the microscopic dimensions of the chips circuitry. The wafer is held in place on a positioning table below the lens system. UV light from an arc lamp or a laser (or X-ray irradiation or electron beam radiation) shines through the clear spaces of the mask s intricate pattern on to the photoresist layer of a single chip. The stepper table then moves the wafer the precise distance required to position another chip under the light. 

Machinery should be built in such a way as to minimise the exposure of workers to the cutting fluids. Manual feeding of workpieces, oil contact when machines are shut off and hands are placed into the machines, and the need to hold workpieces under the flow of oil when it is being machined are machine-design problems which will increase the risk of development of dermatitis. Increasing automation with computer-controlled machines which are enclosed to prevent oil contact will reduce the incidence of dermatitis. 

Basically the CMM is a mechanical system that moves a measuring probe to determine the co-ordinates of points on the surface of a workpiece. The CMM comprises the computer controlled machine itself, the measuring probe, the control system and the measuring software. 

Below are summarized the main steps of the sequence to follow when using these computer-controlled machines ... 

In modern molding practice, these concepts are used, but in a somewhat different fashion. The modern computer controlled machine may have many different stages... 

In computer-controlled machines, sensors continuously monitor the three parameters— rotational speed, axial pressure, and weld time—in addition to the weld penetration, weld or penetration veloeity, and interfacial torque. For reprodueible results and eonsistent weld strength, proeess monitoring is reeommended. Figure 14.24 is a sensor output traee obtained during welding ofpolyvinylidene fluoride (PVDF). Axialpressure and rotational speed were set at 4.3 MPa and 3500 rpm, respectively. 

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