A Mazak QT-8 with T2 control reports axis-drive alarms 13 and 14 while idle or jogging, even though repeated program runs may complete normally. Replacing both X- and Z-axis resolvers did not correct the fault, so use the control’s servo diagnostics to separate a stationary following-error problem from gain or feedback-phase behavior.
Reported Symptoms and Evidence
| Item | Observed or reported condition | Diagnostic implication |
|---|---|---|
| Alarms | 13: signal lost or out of range; 14: position error out of range | These descriptions are reported in the evidence; verify their official definitions in the applicable machine documentation. |
| Affected axes | X axis first, then Z axis approximately one week later | Record diagnostic values for both axes rather than assuming one isolated resolver failure. |
| Operating state | Fault appears while idle or jogging; a program reportedly ran 10 consecutive times without a fault | Prioritize stationary and manual-motion observations. |
| Resolver replacement | Both resolvers were replaced without resolving the alarms | Do not treat another resolver replacement as the next confirmed corrective action. |
| Idle DROOP | Both axes fluctuated from approximately -3 to -5 | The stated diagnostic target is 0 with no motion, making the idle reading the clearest abnormal observation. |
Open the T2 Servo Diagnostics
- On the display, select pages until DIAGNOSIS appears.
- Press the button below DIAGNOSIS.
- Locate the page containing DROOP, GRID, GAIN, PHASE, and VERSION for the X, Z, and C axes.
- With each tested axis stationary, record its DROOP value and whether it remains steady or fluctuates.
- Move the axis manually at approximately 1 m/min and record GAIN. The cited recommended reading is 33.
- Record PHASE as an observation only; the evidence identifies no phase adjustment.
The available evidence does not establish whether an MDI move can be used while viewing these diagnostics. Set the manual jog rate before entering the diagnostic page if the control cannot change or command motion from that page.
Interpret DROOP, GAIN, and PHASE
DROOP represents following error and should read 0 when the axis is not moving. The evidence states that a servo-PCB variable resistor adjusts DROOP, but it does not confirm the resistor identifier. It may be labeled VR, while the board marking and applicable T2 documentation must determine the actual component before any adjustment.
GAIN should be checked during manual motion at approximately 1 m/min; the cited target is 33, with adjustment attributed to VR2 on the servo-amplifier PCB. Treat this as a measurement-first decision: record the reading before changing anything. PHASE represents the difference between the CNC reference signal and resolver feedback, and the evidence provides no adjustment for it.
Diagnostic Decision Path
If idle DROOP is not 0, confirm the correct DROOP adjustment component from the board markings or applicable documentation before changing it, then recheck both axes at rest. If DROOP is 0 but GAIN differs from 33 during the specified manual move, verify VR2 identification before adjustment and remeasure under the same motion condition. If both readings meet their stated targets but alarms 13 or 14 remain, preserve the DROOP, GAIN, and PHASE readings from the alarm-prone idle and jogging states for further service diagnosis; the evidence does not identify another confirmed root cause.
After any documented adjustment, verify that each stationary axis holds DROOP at 0, that GAIN reads 33 during manual motion at approximately 1 m/min, and that idle and jogging no longer reproduce the alarms. Also repeat normal program operation, since successful automatic cycles alone did not expose the reported fault.
FAQ
What should Mazak T2 DROOP read when the axis is idle?
DROOP, described here as following error, should read 0 with no axis motion. The reported X- and Z-axis values fluctuated from approximately -3 to -5.
What GAIN value should I check on a Mazak T2 servo?
Check GAIN while moving the axis manually at approximately 1 m/min. The cited recommended reading is 33, and the evidence associates its adjustment with VR2 on the servo-amplifier PCB.
Do new resolvers require a PHASE adjustment on this T2 control?
The evidence describes PHASE as the difference between CNC reference and resolver feedback and specifies no adjustment. Because replacing both resolvers did not stop alarms 13 and 14, measure DROOP and GAIN before assuming the new resolvers need adjustment.