Department of coordinate of numerical control machine tool is those who undertake design and be machininged is fiducial, but the machine program that uses machine tool coordinate to fasten work out spare parts sometimes is no-go. The part that following plan institute show, if fasten process designing with machine tool coordinate, must calculate before process designing an A, B, C, D and E choose opposite machine tool at 0 o'clock the coordinate of M, such doing trivaller. If choose workpiece some,fixed dot is workpiece at 0 o'clock, if the W in the graph is nodded, was origin at 0 o'clock with workpiece and parallel builds a new coordinate at X of machine tool reference axis, Y, Z is, call workpiece coordinate the department. If the workpiece in the graph the coordinate between M was worth W and machine tool at 0 o'clock at 0 o'clock,be defeated by system of person numerical control, with respect to usable workpiece coordinate the department presses the dimension that tags on blueprint direct process designing, the person that give process designing is brought convenient. The work that basis of numerical control system already lost a person the coordinate of M was worth W opposite machine tool at 0 o'clock at 0 o'clock and the dimension of process designing, calculate automatically an A, B, C, D and E choose opposite machine tool each the coordinate value 0 o'clock. This kind of processing technique calls workpiece coordinate to fasten at 0 o'clock (origin) slant buy (setting) , workpiece is opposite at 0 o'clock the coordinate value 0 o'clock calls the machine tool to slanted at 0 o'clock buy value. The principle that W chose work at 0 o'clock: Workpiece coordinate fastens 0 o'clock is by handlers or process designing person of free choice, the principle that its choose is: (1) should make of workpiece at 0 o'clock the dimension datum coincide with workpiece. (The measure that 2) allows work plan is medium is easy conversion is worth into coordinate, regard coordinate as the value with blueprint dimension directly as far as possible. (W should choose 3) work at 0 o'clock searching easily, facilitate in machining a process metrical place. According to afore-mentioned principle, w chose the work of numerical control lathe normally at 0 o'clock in predestined relationship of workpiece outline right side (if plan institute is shown) on the main shaft axes of left perhaps brim. (4) world coordinate system and increment (opposite) coordinate is fastened in numerical control system, the specific feature motion that shift fastens to a coordinate can use world coordinate system or increment (opposite) coordinate is a description. When writing machine program, according to the coordinate function of numerical control system, go to the lavatory from process designing (tag by part drawing dimension namely) reach the requirement such as treatment precision to set out choosing coordinate is. World coordinate system and increment coordinate department can pass the preparative function of ISO standard and GB to dictate G90, G91 undertakes choosing. G9O states the numerical value of the size word that loses a person is absolute value, g91 states the numerical value of the size word of the input is increment size, the positional numerical value of this absolute value and increment size appointed correspondence the target seat that this coordinate fastens. In coordinate department, to the origin that coordinate fastens, give out spare parts profile nods positional distance or angle calls absolute value measure, this coordinate department calls world coordinate system. Be like the description that the Pl~P9 in the graph nods, its order form, for example the size word that P8 machines to the straight line segment of P9 can be written into: G9O G0l XO.
0. In coordinate department, the place that coordinate chooses is calculate the coordinate increment size that have to express distance or point of view by a position, and athletic way is appointed by its symbol, call increment size measure. If be outline of straight line segment, be equivalent to with sharp starting point (before paragraph the terminus of the program) the parallel that makes parallel fasten each axis at workpiece coordinate for coordinate origin builds a new coordinate is, call opposite (increment) coordinate is. If be outline of circular arc Duan Lun, be equivalent to be coordinate origin to build opposite coordinate department with the centre of a circle of circular arc. The description that like the graph medium Pl~P9 nods, its order form, for example P8 can write into to the word of size of straight line segment of P9: G91 G01 X-70.
0, was equivalent to building an opposite coordinate to fasten XP8Y in P8 dot, the coordinate value that P9 nods is X=-70.
0. The increment size dimension of system of some numerical control need not G91 instruction, the opposite coordinate that builds parallel X, Y, Z in athletic start however fastens U, V, W, its program expresses with G01 U_ V_ W_ , with with equivalent of G91 X_ Y_ Z_ . In machine program of a spare parts, can adopt absolute value measure or increment size dimension, or absolute value and increment size dimension mix use, this basically is to make process designing member can calculate conveniently when process designing the measure that gives block is numeric. Choose world coordinate system or fasten process designing relative to coordinate, tag a method to concern with the dimension of part drawing. If dimension of the spare parts in the graph is standard measure to tag a law, use absolute value measure aptly (G90) , and dimension of the spare parts in graph 2-24 is link dimension (opposite dimension) tag a law, use increment size measure aptly (G91) . CNC Milling