A Hardinge CHNC retrofit must resolve three interfaces before hardware selection: the unidentified DC axis motors, ballscrew feedback, and the pneumatic turret. The available machine evidence suggests a 90 V DC axis system, a 1/4-inch feedback shaft, and a four-input absolute turret encoder, but several critical ratings and signal mappings remain unverified.
Establish the Axis Hardware Baseline
The original axis motors have missing nameplates. One retrofit report identifies them as 90 V DC motors protected by a 7 A fuse. Treat 90 V as a reported nominal voltage and 7 A only as the fuse rating; neither value establishes continuous motor current, peak current, power, torque, or required drive capacity. Verify motor winding resistance, insulation, polarity, current under controlled operation, and the existing drive documentation before selecting replacement drives.
| Interface | Evidence | Engineering decision |
|---|---|---|
| Axis motor | Reported as 90 V DC with a 7 A fuse | Confirm electrical and mechanical ratings before drive sizing |
| Original feedback | Tachometer and resolver driven from the ballscrew | Retain compatible feedback electronics or replace the assembly |
| Feedback shaft | Observed as 1/4 inch | Measure actual diameter, runout, and mounting clearance |
| Replacement encoder | Suggested 2000-line hollow-shaft quadrature differential encoder | Confirm controller input type, voltage, direction, and maximum frequency |
| Turret position | Absolute encoder using four controller inputs | Record the code for every physical station |
Select and Validate Axis Feedback
The available space reportedly permits a hollow-shaft encoder on the end of the ballscrew without a shaft coupling. A 2000-line quadrature encoder produces 8000 count edges per revolution when the controller uses four-edge decoding: 2000 lines/rev × 4 = 8000 counts/rev. Do not describe these edges as motor steps; they are feedback counts at the measured shaft.
Calculate linear resolution only after measuring ballscrew lead. Use linear distance per count = ballscrew lead / 8000. Confirm whether the controller accepts differential quadrature signals and verify the encoder's electrical interface before wiring. The evidence also describes an axis-control architecture using a ±10 V analog command; select drives and a motion controller that support the same command and feedback architecture if that approach is retained.
Integrate the Pneumatic Turret
The turret encoder is described as an absolute device that represents position in base two across four inputs. Four bits can represent up to 16 codes, but the evidence does not provide station count, bit order, active polarity, or the code assigned to each station. Capture the four input states at every mechanically confirmed position instead of assuming a standard binary sequence.
The pneumatic mechanism uses two solenoid outputs: one raises and indexes the turret, and the other fires the stop pin. One retrofit required an additional exhaust-brake output, commanded one turret position before the stop pin, because opening the exhaust adjustment enough to start indexing made stop-pin timing unreliable. Treat that as a machine-specific workaround; first inspect the pneumatic mechanism and verify indexing behavior before adding control logic or converting the index mechanism to a motor.
Commission the Retrofit
- Record motor resistance, insulation condition, polarity, fuse arrangement, shaft dimensions, ballscrew lead, and all existing wiring before removal.
- Mount the hollow-shaft encoder without loading the ballscrew shaft. Rotate the axis slowly and confirm stable A/B quadrature signals, correct direction, and 8000 decoded counts per shaft revolution.
- Jog each axis at reduced command and verify that commanded motion, encoder direction, and control-loop polarity agree. Stop if feedback drives the axis away from the commanded position.
- Manually place the turret at each station and build a table of its four input states. Flag duplicate, unstable, or missing codes as wiring, encoder, or mechanical faults.
- Test turret raise/index and stop-pin outputs at controlled speed. Add exhaust braking only if testing confirms the reported conflict between reliable index start and stop-pin timing.
FAQ
What encoder can replace the Hardinge CHNC tach and resolver?
The evidence supports evaluating a 2000-line hollow-shaft quadrature differential encoder for the reported 1/4-inch ballscrew feedback shaft. Measure the shaft and confirm the controller's signal interface before ordering.
Are the Hardinge CHNC axis motors rated for 7 A?
No continuous motor-current rating is established. The evidence reports 90 V DC motors with a 7 A fuse, but the fuse value must not be used alone to size the motor drive.
How is the Hardinge CHNC turret controlled?
The reported turret uses four absolute-position inputs and two pneumatic solenoid outputs: raise/index and stop pin. Record the four-bit code at every station because bit order, polarity, and station mapping are not provided.