The Serial Peripheral Interface (SPI) is a synchronous serial bus developed by Motorola. The SPI bus is a 4-wire serial synchrous communication interface, set up as a master/slave interface. The SPI is primarily used for serial communication between a host microcontroller and peripherals. Several microcontrollers now privode SPI bus. Wide varieties of peripheral devices such as, converters (ADC and DAC), memories (EEPROM and Flash), Real Time Clocks (RTC), sensors (temperature, pressure) and controllers (LCD controller, USB controller, CAN controller, etc.) support SPI interface. SPI enables direct interface of peripheral devices to microcontrollers. The data transfer rate of SPI is 1 Mbps or 2 Mbps depending upon yhe master or slave configuration.
The SPI bus specifies two control lines Chip Select (CS) and Serial Clock (SCLK), and two data lines Serial Data In (SDI) and Serial Data Out (SDO). The SPI devices communicate using master/slave relationsship, in which the SPI master initiates data transfer. The master generates clock signal on SCLK line and selects a slave by asserting CS line for data transfer. The CS and SCLK are outputs in master and input in slave. The data transfer in either or both directions simultaneously.
(Mathivanan, PC-Based Instrumentation: Concepts and Practice, p.494)
HSK Toolholder (18.04.2011-00.19)
The TSK toolholder is made with a thin wall so it can collapse rather than force the spindle to
expand. The TSK toolholder is pulled back against a face which means it cannot move further back
into the spindle and cannot 'wobble' and become eccentric. With high clamping force against the
face there is greater torque capacity. For low speed high torque application (where balancing is
not critical anyway) a positive drive key is used.
The main benefits are;
* High speed does not change tool position. Conventional tapers expand at high speed and tool
moves back into taper - hard to remove and changes tool reference.
* More accurate location - using the face keeps the tool square. This is especially important with
longer tools.
* HSK allows higher spindle speeds - and therefore can require tighter balancing tolerances.
(D. Norfield, Practical Balancing Of Rotating Machinery, p.210)
Gear Skiving (18.04.2011-00.52)
Skive hobbing is finish hobbing of hardened gears. This process removes the inaccuracies in the gear flanks and profile which occur during heat treatment. The result is improved gear accuracy. It is possible to hob hardened gears in the range up to 63 HRC using tungsten carbide hobs. This gear-finishing process is capable of achieving gear quality levels of up to DIN class 6 or AGMA class 11 in standars module ranges of 1 to 6 mm. Gear skiving has gained in recent years a considerable reputation among gear producers and is nowadays a powerful alternative to traditional grinding and hard hobbing.
(J. P. Davim, Machining of Hard Materials, p. 26)
Polymorphic Transformations (18.04.2011-01.19)
Depending upon thermodynamic state, materials can exist in a number of different physical phases (e.g., solid, or gas). Under certain conditions of temperature and pressure, it is possible (for solids) to transition from one crystalline structure to another. Such transformations in solid materials are referred to as polymorphic transformations. Polymorphic transformations, melting and evaporation of solids are first-order phase transitions. Shock waves can be used to produce a wide range of material states (P, V, T) and establish the conditions for proceeding from one phase to another.
(M. V. Zhernokletov, B. L. Glushak, Material properties under intensive dynamic loadin, p. 191)
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