1.tool post breakdown
1.1 breakdown 1: each cutter spacing on electric tool post keeps revolving
| breakdown causes | solutions |
| no 24v in system; com output | use multimeter to measure system line end and check whether output voltage between the two points are normal or exists, it is system breakdown if there is no voltage. and it is necessary to change mainboard or sent to the manufacturer for maintenance |
| there is 24v;com output in system, but short circuit occurs after it is connected with the transmitting plate on tool post; or 24v vs com ground short circuit | use multimeter to check if there is short circuit between 24v, com ground on tool post and system wiring; check if 24v is short circuited to com ground, lower 24v voltage |
| there is 24v;com output in system, normal connection, broken circuit between 24v on transmitting circuit board of transmitting plate and com ground circuit | the fact that transmitting plate is in humid environment for a long time leads to oxidation of broken circuit. use soldering tin or wire to reconnect |
| low 24v voltage on cutter spacing, pull-up resistor is open circuited | use multimeter to check if the voltage of every cutter spacing is normal, if low, then check pull-up resistor, if open circuit, then change 1/4w2k pull-up resistor |
| system ioc signal tl - no output | use multimeter to measure system line end and check whether output voltage between the two points are normal or exists, it is system breakdown if there is no voltage. and it is necessary to change mainboard or sent to the manufacturer for maintenance |
| system ioc signal tl - output, but there is a problem with circuit among tool post motors | check if there is broken circuit among all intermediate wiring, check if all touch points are connected well, check if dc relay and ac contactor in high-voltage electric cabinet are damaged |
| level signal parameters of cutter spacing are not set up. | check system parameter, high and low level of cutter spacing, check if parameters are normal. if not, then modify the parameters |
| hall components damaged | in case that corresponding cutter spacing is not in broken circuit, if there is low level output for corresponding cutter spacing line, then hall components are not damaged, otherwise they are damaged. it is necessary to change the transmitting plate on tool post or other hall components. there are small chances that four hall components are damaged at the same time |
| magnetic block breakdown, non magnetism or weak magnetism | change magnetic block or enhance magnetism. if magnetic block is in high position when lifting tool post, then change its position and make it align with hall components |
1.2 breakdown two: electric tool post does not rotate
| breakdown causes | solutions |
| tool post three-phase motor phase reversal or phase loss | intermodulate two motor wires on tool post or check exterior power supply |
| no output of forward control signal tl | use multimeter to measure system end line, measure 24v and tl , change the tool manually to see if there is 24v output voltage. if no, then it’s system breakdown, it needs to be sent to the manufacturer for maintenance or change relevant ic components |
| normal output of forward control signal tl , but broken circuit of control signal or damaged components | check if forward control signal is in broken circuit, check if all touch points of the circuit are well contacted; check if there is damage of dc relay or ac contactor |
| no power supply for tool post motor | check if power supply circuit for tool post motor is broken, check if all touch points of the circuit are well contacted, if electrical components of heavy current are damaged; if the fuse is fused |
| no access to pull-up resistor | connect the input signal of cutter spacing with 2k pull-up resistor. if not, the tool post doesn’t seem to revolve, but actually it rotates forward and then reversely at once, making itself look like static |
| mechanical stuck | revolve tool post manually. judge whether it is stuck by tightness. if so, dismantle tool post, adjust the device and add some lubricant |
| mechanical stuck by long period of counter lock | loose tool post on the device, then adjust counter lock time for tool post through system parameters |
| tool post motor damaged | dismantle tool post motor, revolve tool post to see if the motor moves. if not, change tool post motor when the circuit runs well |
| motor short circuit caused by water damage to tool post motor | dry motor, take insulation measures of protection |
1.3 breakdown 3: loose tool post lock
| breakdown causes | solutions |
| non alignment of transmitting plate position | dismantle tool post cap, rotate to adjust transmitting plate position so that hall components of tool post aligns with magnetic block and cutter spacing stays in exact position |
| not enough time of system counter lock | adjust the parameter of counter lock time |
| mechanical locking mechanism breakdown | dismantle tool post, adjust the device, check if locating pin is broken off |
1.4 breakdown 4:certain tool number cannot move but other cutter spacing can move
| breakdown causes | solutions |
| hall components of this tool damaged | check which cutter spacing makes tool post cannot move, rotate this tool in system, use multimeter to measure if the signal touch point of this cutter spacing experiences any voltage change to 24v touch point. if no change, then it is because hall components of this tool are damaged. transmitting plate or hall components should be changed |
| the signal line of this tool is broken circuited, making it impossible for the system to detect in place signal | check if this cutter spacing signal and system wiring are short circuited |
| circuit receiving failure of cutter spacing signal | when it is confirmed that hall components of this cutter spacing and the signal wiring with this cutter spacing run normally, change the mainboard |
1.5 breakdown 5: uncontrollable adoption of row tool post
| breakdown causes | solutions |
| 928tc system adopts row tool post. if use t11, t22, t33, t44 to program, then it may cause control failure of hydraulic chuck, or tool post control error and further interpolation failure | commonly used t11, t22, t33, t44 program should be changed into: t01, t02, t03, t04 program, which is decided by internal software programming |
| 980t system adopts row tool post, if use t11, t22, t33, t44 program, it may cause tool post control error and interpolation failure | commonly used t0101, t0202, t0303, t0404 program should be changed into: t0101, t0102, t0103, t0104 program, which is decided by internal software programming |
1.6 breakdown 6: tool post cannot revolve occasionally
| breakdown causes | solutions |
| control signal of tool post is interfered | system reliable grounding, pay special attention to the grounding of frequency converter, connect with anti-interference capacitor |
| mechanical breakdown inside tool post cause occasional stuck | repair tool post, adjust the device |
1.7 breakdown 7: tool post in 928ta system gives e38 alarm during tool changing
| breakdown causes | solutions |
| inadequate time for tool descending on tool post | adjust system parameter, increase tool descending time |
| system error during interpolation, wrong program format | in program, don’t put t instruction and g0 instruction into the same program segment |
1.8 breakdown 8: tool post can revolve by inputting tool number but not directly pressing tool changing key
| breakdown causes | solutions |
| hall components deviate from magnetic block and they are in front of magnetic block. when change tool manually, tool post in-place signal is detected once revolving tool post, then reverse tool post | check if the hall components on transmitting plate of tool post deviates from the position. if so, adjust transmitting plate position to align the hall components with magnetic block |
| malfunction of manual tool changing key | change manual tool changing key |
2.spindle breakdown
2.1 breakdown 1: spindles without frequency converter don’t revolve
| breakdown causes | solutions |
| caused by mechanical transmission failure | check if there is fracture on belt drive or neutral gear on machine tool |
| phase loss or phase reversal of three-phase spindle power supply | check power supply, exchange any two power lines |
| wrong circuit connection | carefully read circuit connection manual and ensure correct connection |
| no corresponding spindle control signal output | use multimeter to measure system signal output. if no spindle control signal output, then change ic components or send to the manufacturer for maintenance |
| there is corresponding spindle control signal output in system, but power supply and control signal output are broken circuited or components are damaged | use multimeter to check if there is broken circuit between power supply circuit of system and spindle motor and control signal circuit; if all touch points are well connected; if ac contactor and dc relay are damaged; if thermorelay is with overcurrent; if the fuse is burned down |
2.2 breakdown 2: spindles with frequency converter don’t revolve
| breakdown causes | solutions |
| caused by mechanical transmission failure | check if there is fracture on belt drive or neutral gear on machine tool |
| phase loss of three-phase spindle power supply | check power supply, exchange any two power lines |
| the control parameters of cnc frequency converter are not activated | read system instruction, know parameters of frequency converter and change them |
| wrong connection of system circuit and frequency converter circuit | read the manual of system and frequency converter connection and ensure correct connection |
| abnormal analog voltage output | use multimeter to check if analog voltage output is normal; if analog voltage signal line are connected correctly or connected well, if the received analog voltage matches the frequency converter |
| broken circuit in heavy current control part or components damaged | check if all touch points of spindle power circuit are connected well, if there is broken circuit, if dc relay are damaged, if the fuse is burned down |
| frequency converter parameters are not set up | frequency converter control modes include panel control spindle and nc control spindle. if nc control mode is not selected, then it’s impossible for the system to control spindle and modify this parameter; check if relevant parameter is set up reasonably |
2.3 breakdown 3: spindles with electromagnetic coupler don’t revolve
| breakdown causes | solutions |
| no voltage supply for electromagnetic clutch coil makes transmission gear cannot close and further makes spindle cannot revolve; coil short circuit and broken circuit may cause spindle malfunction as well | check if power supply of the clutch coil is normal; if power fuse is damaged; if clutch coil is damaged. if so, change to standard components |
2.4 breakdown 4: spindles with contracting brake coil don’t revolve
| breakdown causes | solutions |
| spindle’s frequent start and stop causes brake’s frequent start and stop, making ac contactor of control brake damaged, brake coil containing spindle motor and stopping spindle from revolving | change ac contactor for controlling contracting brake |
2.5 breakdown 5: spindle speed controlled by frequency converter is not under control
| breakdown causes | solutions |
| the used mainboard has no function of frequency conversion | change the panel with frequency conversion function |
| no analog voltage output or broken circuit in connection with frequency converter | check if there is analog voltage output. if no, then it’s system breakdown. if there is, then check if there is broken circuit |
| wrong connection between system and frequency converter | read connection instruction and check circuit |
| system parameters or frequency converter parameters are not set up | activate frequency converter parameters and adjust them |
| wrong display of spindle speed caused by software | when frequency converter is changed from s500 to s800, it is still displayed with s500. it is necessary to adopt g04 delay during programming and improve system software |
| spindle speed stays the same in 928tdc system, resulting from improper programming | during programming, s, m, t instructions shouldn’t be programmed into the same program segment. instead, put t instruction alone in one another program segment. otherwise, spindle speed will be constant by default. sometimes there is display of invariable speed value when s and t are in the same segment, but the actual speed has already changed. it is suggested that these two instructions shouldn’t be in the same segment |
2.6 breakdown 6: speed of spindle without frequency conversion (gear shift spindle) is out of control
| breakdown causes | solutions |
| no s01-s04 control signal output in system | check if there is signal output of gear shift control. if no, then it’s system breakdown. it’s necessary to change ic or send it to the manufacturer for maintenance |
| connection circuit breakdown | if there is signal output of gear shift control in system, check if there is broken connection circuit or bad connection, if dc relay or ac contactor are damaged |
| spindle motor damaged or short circuit | check spindle motor |
| the device is not in the gear | put into gear |
2.7 breakdown 7: no spindle brake
| breakdown causes | solutions |
| brake circuit anomaly or heavy current components damaged | check if bridge rectifier, fuse and ac contactor are damaged; if heavy current circuit is broken |
| inadequate time for brake | adjust brake time parameter for system or frequency converter |
| no brake signal output in system | change internal components or send to the manufacturer for maintenance |
| frequency converter control parameters are not set up | read frequency converter operating instruction and set up correct frequency converter parameter |
2.8 breakdown 8: spindle stops immediately after start-up
| breakdown causes | solutions |
| inadequate time for pulse output | adjust m code output time |
| the frequency converter is in inching state | read frequency converter operating instruction and set up parameter |
| control components of spindle circuit are damaged | check if all circuit touch points are connected well, if dc relay, dc contactor are damaged and further stops contactor from self-hold |
| spindle motor short circuit cause thermorelay protection | find out short circuit cause and reset thermorelay |
| no self-hold circuit for spindle control and setting parameter as pulse signal output stops spindle from normal revolving | change start and stop parameter of system control to that of level control |
2.9 breakdown 9: spindle revolving cannot be stopped
| breakdown causes | solutions |
| ac contactor or dc relay are damaged for they are closed for a long time and out of control | change ac contactor or dc relay |
2.10 breakdown 10: spindle revolves immediately once the system is powered on
| breakdown causes | solutions |
| system internal ic2803 breakdown | change ic2803 or system mainboard |
3.unstable machining dimension breakdown
3.1 classified by components causing unstable breakdown:
eliminate or narrow down breakdown range by the method of exchange and find out the components causing unstable breakdown
3.1.1 breakdown 1: dimension change unstable caused by system
| breakdown causes | solutions |
| unreasonable setting of system parameter | check if the fast mode speed, acceleration time, spindle speed, cutting speed are reasonable, if the modification of the operator’s parameter changes the system performance |
| unstable working voltage | install voltage stabilizer |
| external interference makes system step out | make sure the ground wire is reliably connected and anti-interference capacitor is installed on the touch point of driver pulse output; in general, frequency converter brings big interference, please judge in the situation of adding payload. larger load will cause larger load current for frequency converter and larger interference |
| capacitor already added, but resistance between system and driver doesn’t match, losing useful signal | select proper capacitor model |
| signal transmission error between system and driver | check if the signal connection wire between system and driver is shielded, if the connection is reliable, if there is any change of pulse generating signal amount |
| system damage or internal failure | send it to the manufacturer for maintenance or change the mainboard |
3.1.2 breakdown 2: driver cause unstable dimension
| breakdown causes | solutions |
| loss of signal sent by the driver makes the driver step out | make sure which one is used, step driver or servo driver. if step driver is used, use phase lamp or dial indicator to judge the situation. if servo driver is used, refer to pulse amount displayed on the driver or dial indicator |
| improper setting of gain index on servo driver | modify gain index referring to da98 specification |
| driver signal interference makes it step out | install shielded wire and anti-interference capacitor |
| the drivers is in high temperature without heat dissipation device, which causes unstable dimension and inner parameter change and further mechanical breakdown | guarantee good heat dissipation and ventilation. appropriate temperature is an important factor to ensure machining performance |
| inadequate torque for driver or motor | change driver or motor, and make appropriate torque |
| inadequate driver current | change the driver if it still doesn’t meet requirements after turning up the driver current |
| the driver is damaged | send the driver to the manufacturer for maintenance |
3.1.3 breakdown 3: unstable machining size caused by mechanical reasons
| breakdown causes | solutions |
| damping sheet of step motor is too tight or too loose. | adjust damping plate, keep the motor in non-resonance state |
| water damage in motor plug reduces its insulativity and ruins the motor | change motor plug and make good protection or change the motor |
| improper workpiece reducer and clamping | check if large or fast feed causes overload, make sure the workpiece clamping doesn’t reach out the chuck too long and avoid cutter relieving |
| oval workpiece | check spindle throbbing, spindle overhaul, change bearings |
| large screw backlash | check screw backlash with dial indicator, if the backlash has been added from the system or the backlash is too large after adding it. |
| tight installation of mechanic screw rod | check if the screw rod moves and responds slowly |
3.2 classification based on unstable breakdowns:
3.2.1 breakdown 1: tiny differences between workpiece size and actual size (0.01mm~0.10mm)
| breakdown causes | solutions |
| machine tool friction and wear for a long time enlarges screw rod backlash, further makes machining dimension unstable, so workpiece error changes within the backlash range | when machine tool wear enlarges backlash, adjust screw nut and tighten wire or get backlash value by dial indicator (less than 0.15 mm generally), then add it to computer, compensate the missing backlash so as to make the workpiece meet requirements |
| wrong machining tool, easily wearing, wrong tool clamping or not in place | different tool materials change workpiece size, so select tool properly. as for tool clamping not in place, select tool angle and jig properly |
| in processing craft, select appropriate spindle speed, cutting feed speed and cutting amount based on workpiece material | when it’s processing craft issue, based on material attribute, properly select spindle speed, cutting feed speed and cutting amount for processing craft |
| related to machine tool balance and steadiness | if caused by machine tool resonance, then place machine tool smoothly, install steadily, lay the foundation if necessary |
| caused by cnc step-out or deficient drive power and small torque | as for cnc size change, first check if the program is compiled based on drawing size, then according to the selected configuration, check if parameters are reasonable (e.g. g0 fast positioning speed and acceleration and deceleration constants for cutting). first consider if there is intentional change, then if the selected driver power is reasonable, judge if the driver pulse sent by computer steps out by phase lamp |
| if the tool post locks after changing the tool | check if the reversing time for tool post is sufficient after changing the tool, if there is sufficient time to lock the tool post, if tool post positioning and screw are loose |
| if there is spindle bounce and tailstock axiality tolerance | check if there is spindle bounce and tailstock axiality tolerance |
| in some special machining environment, backlash cannot be added, causing machining error | eliminate backlash with programming techniques |
3.2.2 breakdown 2: several millimeters difference between workpiece size and actual size or great change in axial direction
| breakdown causes | solutions |
| fast positioning speed is too fast, leaving no time for the driver and motor to respond | fast positioning speed is too fast. properly adjust g0 speed, speed and time for cutting acceleration and deceleration so as to make the driver and motor normally run within rated operating frequency |
| mechanical screw and bearing are too tight after long-time friction and wearing | if the planker, screw rod and bearing are too tight and stuck, adjust and repair them again |
| loose tool post after changing the tool | if tool post is too loose after changing the tool, check if there is sufficient reversing time for tool post, if the turbine and endless screw inside tool post are wearing, backlash too large and installation too loose |
| program editing error, non-corresponding program header and end or end without canceling interpolation | if caused by program, then modify program. improve and select proper processing craft according to workpiece drawing, compile correct program based on the instructions on the manual |
| electric gear ratio or stepping angle error | if the size difference is too large, then check the system parameter setting, especially electric gear ratio and stepping angle. measure them with dial indicator |
3.2.3 breakdown 3: incremental or decremental machining process
| breakdown causes | solutions |
| programming error | check if program instructions are executed based on the requirements on the manual, measure it with dial indicator. put dial indicator at program starting point, check if the planker goes back to the starting point at the end of program, repeat such operation and observe and grasp the rules |
| improper parameter setting | check if system parameters are properly set up or modified manually |
| improper configuration setting | if relevant machine tool configuration meets the requirements of connecting coupling parameter, if pulse equivalent is correct |
| regular and periodic breakdown of mechanical transmission parts | check if machine tool transmission parts are damaged, whether gear coupling are even and if there is periodic and regular breakdown. if so, check key parts and eliminate breakdown |
3.2.4 breakdown 4: phase lamp on the driver runs normally, but the machined workpiece size is not stable
| breakdown causes | solutions |
| machine tool runs at high speed for a long time, wearing screw rod and bearings | put the dial indicator at the bottom of tool post, edit one fixed cycle program in system, check the planker’s repetitive positioning precision, adjust screw backlash, change bearings |
| repetitive positioning precision of the tool post causes deviation during the long-time operation | check the tool post’s repetitive positioning precision, adjust the machine or change tool post |
| the planker returns exactly to the machining starting point every time, but the machining size is not stable. it is caused by spindle generally. spindle’s high speed revolving wears the bearing and causes changes of machining size | check if it can returns to the program starting point after workpiece machining with dial indicator; if so, check and repair the spindle, change bearings |
3.2.5 breakdown 5: one machining process change (cutting arc and thread), correct size for other processes
| breakdown causes | solutions |
| if the parameters of this program segment are reasonably set, if they are within predetermined track, if programming format meets the requirements on the manual | non-alignment of screw program segment and pitch error are usually related to the screw’s peripheral configuration (encoder) and other objective factors, such as spindle speed, the relation between screw lead and feed speed (928tc match dy3, spindle speed x screw lead ≤1700mm/min), check if encoder line amount conforms to computer setting; if there is size error of disk program segment, then check if arc programming track is in the same arc, if there is processing craft programming among special circles |
3.2.6 breakdown 6: workpiece taper reducer
| breakdown causes | solutions |
| machine tool is not placed well, one side high and one side low | use gradienter to adjust the levelness of machine tool, lay solid foundation, fix the machine tool, improve its toughness |
| while turning long axis, workpiece materials are hard, tool is taken a deep cut, causing tool relieving | select proper process and cutting feed to avoid tool relieving |
| the tailstock centre and the spindle are not concentric | adjust tailstock |
3.2.7 breakdown 7: occasional workpiece out of tolerance during volume production
| breakdown causes | solutions |
| when one workpiece is machined with different size in volume production, it recovers without modifying any parameter | check jig carefully, taking operator’s operating method and the reliability of clamping; due to size change by clamping, improve process equipment and avoid misjudgement caused by negligence |
| when one workpiece is machined with wrong size, it is still with substandard size after continuous machining, but it shows the correct size after realignment. | cnc system may automatically generate disturbing pulse after power fluctuation or external interference, and then transmit the pulse to the driver, making the driver receiving extra pulse and the motor motion unstable; grasp the rules, adopt some anti-interference measures, e.g. separate the high voltage cable in strong electric field and signal line of weak current, install anti-interference capacitor and use shielding wire. in addition, check if the ground wire is tightly connected, closest to grounding contact. if so, adopt any anti-interference measures to keep the system from interference |
3.2.8 breakdown 8: correct workpiece size but poor surface smoothness
| breakdown causes | solutions |
| tool tip damaged, not sharp | tool gets blunt after damage or wearing, sharpen the tool again or select better tool and realignment |
| machine tool resonance and non-smooth placement | adjust the levelness, lay the foundation and fix machine tool |
| the machine crawls | the machine crawling caused by severe wearing of guide rail, wearing or looseness of ball screw. pay attention to machine tool maintenance, timely add lubricating oil to reduce friction |
| poor machining process | select the suitable coolant for workpiece machining; select relatively high spindle speed on the condition of meeting the requirements of other process machining |
3.2.9 breakdown 9: non-ideal arc machining size and effect
| breakdown causes | solutions |
| overlapping of vibration frequency causes resonance | find out the resonance part and change its frequency to avoid resonance |
| machining process | consider workpiece machining process, properly compile program |
| inappropriate parameter setting, over-large feed speed makes arc machining step out | don’t set up the machining rate f too large as for step motor |
| large screw backlash causes smoothness or tight screw causes step-out machining | if machine tool is installed firmly, placed smoothly, if the planker is too tight after wearing, if backlash increases of the tool post gets loose |
| synchronous belt wearing | change synchronous belt |