The stage amounts to the servo application on CNC engraving tool
- source:NEWRGY CNC Machining
System of feed of engraving tool of CNC of brief introduction of 1 feed system is main the task is will slip (workbench or active head, pillar) along slideway, according to the motion with instruction stable rate. Outside the feed system design besides component of consideration machinery drive, return drag in to decide position control issue to servo. Say so, substantially feed system is Electromechanical unifinication compositive system, the system makes process work or cutting tool can depend on the fixed rate, position, shift that makes high accuracy, refer to a graph 1. Graph 1 control flow chart and systematic frame and a good CNC engraving tool should have stability good, precision is tall and the character that answers quickly. So, want to realize such condition, wanting considered important segment is: Inertia matchs and problem of feed system tigidity. 2.
2 mechanical inertia and able-bodied (rash club) control drive inertia is right the precision of servo, stability, trends is answered influential, inertia is big, mechanical constant of the system is big, answer slow, can make systematic natural frequency drops, easy generation is syntonic, restricted servo bandwidth consequently, affected servo precision and answer speed. Accordingly, below the condition that systematic stiffness is not affecting when mechanical design, should reduce mechanical inertia as far as possible and notice inertia to match, choose electric machinery of appropriate inertia size thereby, reach inertia is compared. Feed system place needs angular acceleration θ of × of J of inertia of drive of system of pitching moment T= ; The whirl of the electric machinery of servo of ＝ of total inertia J of feed axis is inertial the laden and inertial JL of conversion of axis of JM ＋ electric machinery. So is inertia of system of feed of CNC engraving tool how match? When the trends that measures mechanical system is characteristic, inertia is smaller, dynamic and characteristic response of the system is better; Inertia is bigger, motor load is bigger also, jump over difficult control, but the inertia of mechanical system needs and motor inertia photograph matchs ability travel. Different orgnaization, match a principle to have different choice to inertia, and have different action show. When CNC engraving tool makes high speed cutting through servo electric machinery, when laden inertia increases, can produce following situations: (1) when control instruction is changed, motor needs to cost more time ability to achieve the speed of new statement to ask; (2) carry out arc type curve along 2 axes when machine stage when fast cutting, can produce bigger error. And normally the state issues general servo electric machinery, when JL ≦ 3JM, criterion the question above won't happen; When JL ≧ 5 × JM, motor can accuse a gender to be able to drop apparently, when cutting of high speed curve expression is highlighted. To this, the stage amounted to servo to introduce able-bodied (rash club) control, can patient very big inertia changes, the requirement that compares to inertia is reduced greatly. 2.
The tigidity of 3 Electromechanical tigidity and system of able-bodied control feed is to point to get when load, ability of metabolic of feed system resistance. Tigidity of system of numerical control feed can divide the servo tigidity of the mechanical tigidity that is mechanical system and servo. (1) mechanical system is rigid. Tigidity of feed system machinery is the active force that shows the mechanical component such as screw produces an unit to be out of shape place needs, reflected ability of metabolic of mechanical component resistance. Mechanical (static) rigid definition: K=F/ △ X (Kgf/um) the F in; type: Active force (Kgf) ; △ X: Deflection (Um) (2) servo tigidity points to whole feed servo, come out to resist laden interference brings the capacity of positional deviation to workbench expression with controller namely. Servo is rigid more it is important to show, and the stage amounts to servo to use able-bodied (rash club) control, resist ability of laden change interference is highlighted. 3 amount to the stage of 3 loop compose that servo application graph amounts to servo 2 times to amount to servo to be formed by structure of 3 closed circuit, comprise the annulus in positional outer shroud, speed and voltaic core, refer to a graph 2. What the stage amounts to servo is able-bodied model low-cost die type becomes a stage to amount to technical characteristic. 3.
1 able-bodied type is controlled (rash club is controlled- - Robustcontrol) able-bodied type control makes the laden inertia that the stage amounts to CNC to face rapid change still retains good performance. Able-bodied type controls the contemporary control law that patient oneself mutates. Secure the controller is not PI of make choice of, hold able-bodied stability and property. In big range load inertia changes, the system still retains excellent performance. Have different compensation control to command and interference; Damp tigidity is admirable, low speed rotate speed uses character admirable; Stability assures completely; Amount exceeding tone is very small. 3.
2 tall answer frequency wide needle to be opposite at low rotate speed tall gain set is brought tall torsional but easy cause oscillation, and small gain set is met again the contradiction that motor peristalsis runs, the stage amounts to CNC to use tall sampling to lead (> 15KHz) is obtained tall answer frequency wide, make the moving effect that low rotate speed has fast rigid and very steady movement. 3.
The 3 gain that amount to CNC to go up in engraving tool are debugged (1) JOG mode. JOG mode is used at breaking away from test run of the machine on superstratum pilot test and preliminary and inertial measure than appraise, refer to a graph 3. Test of graph 3JOG inertia controls flow chart (2) automatic gain mode. Automatic gain mode is used at be being adjusted continuously, refer to a graph 4. Graph mode of 4 automatic gain controls flow chart (3) the hand moves gain to adjust (positional mode) refer to a graph 5. Graph 5 hands move gain to adjust control flow chart (4) debug an attention to want a place: After · feed rate rises, the follow error of servo meets those who follow rate rise increase, the influence is mobile dynamic precision (all set the gain of each axis servo into same size commonly, especially X, y axis) , the servo that the stage amounts to works calm time short, utmost protects dynamic precision. Component of · machine stage has its natural frequency, when generation is syntonic, noise, oscillatory, noisy merit is restricted. Use a software that amounts to servo to confirm syntonic point, set software trap to eliminate mechanical resonance, promote a machine tool respondent sex. · chooses appropriate inertia electric machinery, machine tool and electric machinery inertia match, the stage amounts to servo to have able-bodied sex control, match a requirement to be reduced greatly to inertia, and take inertia appraise to measure a function oneself, dispense with is complex computational process. · traditional hand is moved debug wait deputy take parameter, experience sex is strong, and debug groove hard, the stage amounts to servo to offer special debug software, not only the operation is simple and debug the effect admirable. 4 last words are current the proportion that holds on industry of CNC engraving tool is in every year stable rise. The good quality that systematic place has and good stability and powerful control function make the stage amounts to servo to there is wide applied perspective on industry of high-end engraving tool. CNC Milling CNC Machining