Why should CNC system have electronic gear to compare?

001mm. After reference axis enters the position to control, CNC outputs instruction pulse according to the smallest mobile increment, real position is detected by the position device (like pulse coder, pulse Coder) by its resolution gives out feedback pulse. The displacement amount that correspondence of pulse of a feedback produces is called detect pulse equivalent or detect unit. Actually, detect pulse equivalent often as abhorrent as instruction pulse equivalent. For example, some coder and coaxial of servo electric machinery are installed, every turn 1 turn detect 2500 pulse (call coder resolution 2500 pulse / turn) , if electric machinery turns 1 change the line of production the linear and mobile distance of unripe 10mm, criterion a pulse of coder is represented 0.

004mm. Apparent, with 0 of the instruction.

001mm is abhorrent. Both abhorrent consequence is an axis actual displacement and screen show displacement is abhorrent, bring about treatment namely dimension is incorrect, and to this kind of breakdown, the system does not have any calling the police to hint, jockey often is at a loss. Accordingly, closed circuit system can undertake correct error relative premise is: The CNC output that either shift measures a correspondence dictates pulse number and actual feedback pulse are counted must equal, the both pulse equivalent when entering comparator namely must agree. And in applying actually, detect as a result of mechanical drive structure and position of device different, instruction pulse equivalent and detect actually the unit always is abhorrent. To make both matchs, undertake comparative computation thereby, numerical control system provided software set function. This is like machinery to match for speed in main transfer machinery and be added like holding gear wheel, scale of this software set also calls friend electronic gear is compared (Electronic Gearing) . Electronic gear is more different than having in the CNC in different brand make a way, the electronic gear that FANUC system says below is compared. CMR and DMR are make CNC dictates pulse and detect pulse equivalent photograph is comfortable match, the statement was used in FANUC 0i system times by than (CMR) and detect times by than (DMR) , before entering the position to compare accordingly, pulse all is passed times by processing. The graph is shown 1 times for feed axis motion is controlled times by processing block diagram. The symbol explains as follows related ‍ : ·‍CMR: Dictate times by than (Command Multiplying Ratio) , to make CNC dictates pulse and detect pulse equivalent photograph is comfortable the constant ·DMR that match: Detect times by than (Detection Multiplying Ratio) , to make CNC dictates pulse and detect pulse equivalent photograph is comfortable the constant ·C that match: The smallest mobile increment (Least Movement Increment) , CNC interpolation output dictates to the shift of the machine tool most subsection (Mm/ pulse)·D: Detect unit (Detection Unit) , can detect the smallest mobile unit of the machine tool that give (Mm/ pulse)·I: Increment of the smallest input (Least Input Increment) , the instruction that the program inputs most subsection (Mm/ pulse)·N: Of positional detector every turn pulse is counted (pulse / turn)·T: Servo electric machinery 1 change the line of production the shift of mobile component measures unripe machine tool (Mm/ turns)·P: Guide screw pitch (Mm/ turns)·I: Transmission decelerate is as follows than the relation between above parameter: Pass CMR, can increment of a the smallest input (like 0.

001mm) fractionize undertakes outputting for many pulse. For example, in system of accept rice CNC, the position that sends digital servo controller dictates the unit is 1nm, far input an unit than process designing (0.

001mm) careful, can gain the treatment face of high accuracy, right now the ‍ of system of accept rice CNC passes DMR, can be fractionize of pulse of a feedback output of many feedback pulse. For example, some instruction unit of linear axis is 1μm, pitch of ball guide screw is 10mm, direct link (transmission decelerate compares I ∶ 1 for 1 ∶ 1) , pulse coder is 2500 lines (N=2500 pulse / turn) , the requirement detects the unit is 1μm, criterion basis (type 3) , manufacturer of appropriate machine tool (MTB) when production machine tool, the lead of chosen ball guide screw (pitch) it is different, want to achieve resolution 1µm, use a certain coefficient with respect to need. The F·FG in FANUC system (Flexible Feed Gear, flexible feed gear compares) action is: The positional feedback pulse that comes from serial pulse coder through making is alterable (the line that does not need coder of make choice of is counted) , can be compared at the pitch of guide screw of of all kinds ball, decelerate relatively and easy to do set detects unit. If pursue,3 are shown. Resolution of system of half closed circuit matchs graph 3 FANUC graph CMR=Cmd Unit/Detect Unit. F·FG is equivalent to DMR, just DMR is used at one's early years the set of collateral output coder, present pulse coder uses serial output, and servo electric machinery every are rotational 1 week from coder of βi serial pulse (the outfit inside electric machinery) return 1000000 pulse, reason uses F·FG. For example, receive the ball guide screw of pitch 5mm/r one after another continuously, detect when the unit is 1µm, electric machinery every are rotational 1 week (5mm) wants pulse number is 5000, because of this basis (type 3) , note: CNC interior is automatic coder every turn convert of pulse number N becomes 1000000 pulse / turn (the actual resolution that takes no account of coder) . F·FG is in SERVO SETTING picture (if the graph is shown 4 times) in install with the form of element and denominator (=N/M) , also can be in parameter PRM No.

2084 with No.

2085 in part set N and M. Friendship reminds ‍ : The N in SERVO SETTING picture and M represent element and denominator only, with (type 3) medium N (those who point to coder every turn pulse is counted) it is two things, cannot promiscuous. F·FG is servo initialization set (SERVO SETTING) the most important parameter in the picture, if F·FG installs a mistake, the machine tool cannot walk out of correct displacement, affect spare parts measure directly. Electronic gear is compared is the parameter with numerical control the mainest machine tool, relation a move in chess or a movement in wushu accuses the machinery on the machine tool and match electricly. The friend that have fun at, or it is foreign vermicelli made from bean starch can watch the video that compares about electronic gear below CNC Milling CNC Machining