08/10/2025 By CNCBUL UK EDITOR Off

Technical Evaluation Guide: How to Identify a Quality Used, Secondhand, Pre-Owned, Surplus Nakamura Tome Super-Mill WY-250L CNC Dual Turrets Twin Spindle Multi-Axis Turning/Milling Center made in Japan

1) Machine Overview & Reference Specifications

Before visiting, obtain the original spec sheet or catalog for that exact machine unit. Below are key published specs and features for the WY-250L as a baseline.

Feature	Published Spec / Capability
Max turning diameter	225 mm
Max turning length	910 mm
Distance between spindle noses	Up to 1,200 mm (max)
Bar capacity (L / R spindles)	L: 65 mm ; R: 51 mm (standard)
Spindle speeds	L / R up to ~4,500 / 5,000 rpm
Spindle motors (standard)	L: 18.5 / 11 kW ; R: 15 / 11 kW
Turrets / Tooling	Two turrets, each a 24-station dodecagonal drum turret; ~24 driven tool positions total
Y-Axis travel on turrets	±50 mm (upper), –50 / +20 mm (lower)
Driven tool spindle	Up to 6,000 rpm, motor ~7.5 / 3.7 kW
Machine footprint / weight	Floor dimensions ~ 4,900 × 2,580 × 2,395 mm (L×W×H), weight ~13,000 kg

These specs set your expected tolerances. Any candidate machine should be reasonably close unless documented modifications exist.

2) Pre-Inspection Document Request

Before going on site, ask the seller to supply:

Original specification / build / configuration sheet
Serial number, year of manufacture, and internal option history
Maintenance / repair logs (spindle rebuilds, turret servicing, drive maintenance)
Calibration / accuracy / metrology / alignment records
CNC parameter backups, compensation tables, tool offsets
Electrical / hydraulic / pneumatic / pneumatic / wiring diagrams
Tooling and accessories list (live tooling, chucks, holders, steady rest)
Any reports of crashes, collisions, retrofits or modifications
Work history (typical parts machined, duty cycle)

This documentation helps you evaluate how far the machine may have drifted and what risk it carries.

3) Static / Visual Inspection (Power Off)

Walk around and carefully inspect all major structures and assemblies:

Bed, frame & base: check for cracks, weld repairs, distortions, sagging, settling, or evidence of impact.
Spindle housings / barrel / nose: inspect for corrosion, dents, wear on taper surfaces, cracks.
Turret assemblies: open turret covers and check indexing cams, gripper fingers, pocket faces, backlash play.
Guideways, slideways, rails: examine for scoring, pitting, rust, polished zones, uneven lubrication.
Y-axis saddle / slide components: check for looseness, binding or wear in Y-actuation parts.
Drive motor, gearbox, couplings: inspect for signs of wear, backlash, loose fasteners.
Cable chains, harnesses, hoses: examine insulation, chafing, repairs, aging, broken links.
Electrical cabinet: open and inspect wiring, burned insulation, capacitor bulge, dust; examine components’ condition.
Coolant, lubrication lines & pumps: look for leaks, corrosion, cracked hoses, blocked lines.
Safety doors, covers, interlocks: verify the presence and condition of guards, interlock switches.

Document all anomalies with photos; take close-ups of suspect areas (wear, rust, repair work).

4) Installation & Alignment Checks

If the machine is already mounted:

Check machine leveling and foundation anchor points for settlement or shifting.
Mount a reference test bar or indicator in one spindle in neutral turret position and measure radial runout at different positions along the carriage or turret reach.
Jog X / Z / Y axes small increments to detect binding, sticky zones, or deviations.
Perform turret indexing (upper & lower) and measure deviation of indexed tool carriers relative to spindle centerline.
Check that Y-axis travel on both turrets is symmetrical and smooth, with no binding or tilt.
If the machine has a B-axis (or rotary indexing), test its mechanical integrity and axis alignment.

5) Power-On & Motion / Functional Tests

With power and safety in place, perform these dynamic tests:

Warm-up jogging: move axes (X, Z, Y) for ~20–30 min to stabilize lubrication and temperature.
Homing / reference cycles: repeat referencing and ensure consistent return without limit trips or errors.
Axis stroke test: jog X, Z, Y at various speeds (slow, medium, high) and listen / feel for irregular motion, binding or jerk.
Turret indexing cycles: repeatedly index upper and lower turrets, check for mis-index, hesitation, or alarm errors.
Spindle ramp-up / rotation: gradually accelerate both spindles (L & R) to operating RPM, monitor vibration, noise, smoothness, current draw.
Simultaneous machining simulation: run a sample program using both spindles / turrets in tandem (if safe) to test synchronization and interference.
Driven tool testing: spin the driven tools at rated speed (6,000 rpm) with light load, check for vibration or instability.
Coolant / lubrication systems: engage coolant pumps, flush lines, check for leaks, stable pressure.
Control / alarms: inspect alarm history, simulate minor fault conditions (e.g. limit switches) to ensure correct error detection.
Encoder / feedback integrity: during motion, observe position feedback signals or readouts—check for dropouts or anomalies.

6) Accuracy, Repeatability & Metrology Tests

These tests distinguish whether the used machine is still precise enough:

Use a laser interferometer or precision gauge to test linear positioning / straightness on X, Z, and Y axes.
Perform backlash / reversal error tests: small ±0.01 mm moves in each axis and measure the difference when reversing direction.
Repeat to a target position (e.g. 10×) and assess repeatability error.
Repeatedly index turrets to the same tool station and measure tool location repeatability relative to spindle.
Run a combined contour / interpolation test (turn + mill + Y-axis motion) and measure deviation from programmed path.
After prolonged operation (≥1 hour), re-check reference positions to evaluate thermal drift.
Conduct a hysteresis test: move to a position, dwell, return, and measure offset from original position.
For long spindle reach / turret overhang positions, check accuracy near extremes, not just near center positions.

7) Spindles, Tooling & Wear Checks

Mount a precision test bar and measure radial runout of each spindle nose / taper.
Use vibration analysis or careful listening for bearing noise / hum at intermediate RPM.
Run spindles continuously at moderate RPM for ~30 minutes and measure temperature rise.
If internal spindles have drawbars or clamping, test retention / pull-out force.
Validate taper or seating surfaces using dye / “blue” contact tests for even contact.
Cycle tool changes (for live tool / turret tools) and verify tool offset repeatability.
If milling heads or additional rotary / B-axis attachments exist, test their performance similarly (runout, vibration, repeatability).

8) Lubrication, Cooling, & Auxiliary Systems

Confirm lubrication / oil / grease systems supply to all axes, turrets, spindles—check for blockages or leaks.
Activate coolant systems, verify flow, pressure, filtration condition, and absence of leaks.
Inspect coolant tanks, filters, piping for corrosion, sludge, or contamination.
Operate chip conveyors, swarf removal, guarding and check for smoothness and no jamming.
Test any hydraulic / pneumatic actuators (e.g. turret locking, tailstock clamps) for pressure stability and leak-free performance.
Verify control cabinet ventilation, fans, and that electronics remain cool during continuous operation.

9) Common Wear Modes & Red Flags

Turret indexing wear, backlash or creep
Y-axis mechanism play or binding
Spindle bearing fatigue, vibration or runaway noise
Tool change / gripper wear, inconsistent offsets
Drive train backlash or nonuniform torque response
Loss of lubrication, contamination of slides / rails
Coolant leakage into critical mechanical areas
Control / drive electronics aging: overheated components, failed boards
Encoder feedback errors or dropout under motion
Cable chain fatigue, insulation breakdown, connector failures

If multiple such issues are observed, the machine risk is high.

10) Acceptance Criteria & Benchmark Tolerances

Use this sample tolerance table as your “go / no-go” thresholds (tweak based on actual spec sheet and required precision):

Parameter	Target / Acceptable Range
Linear axis accuracy (X, Z, Y)	± 0.005 mm over moderate stroke
Backlash / direction reversal error	≤ 0.01 mm
Repeatability (multiple cycles)	± 0.005 mm or better
Turret / tool station repeatability	≤ 0.01 mm
Spindle radial runout	≤ 0.005 mm
Thermal drift (after 1 hr)	≤ 5–10 µm shift
Tool offset consistency	≤ 0.01 mm variation
Drive / servo current stability	Smooth curves, no spikes
Noise / vibration at rpm	Minimal, no bearing whine peaks
Coolant / lube stability	No significant drop under load

If the machine fails several key benchmarks (especially spindle, turret repeatability, accuracy), it becomes a risky candidate or will require full refurbishment.