08/10/2025 By CNCBUL UK EDITOR Off

Technical Evaluation Guide: How to Identify a Quality Used, Secondhand, Pre-Owned, Surplus COMEV CDR 20 CNC Lathe made in Italy

1) Machine Overview & Benchmark Specifications

Before your inspection, request the original spec sheet or brochure for the exact CDR 20 unit under consideration. Below are typical or representative specs based on listings and COMEV product lines for a CDR-20 series lathe:

Feature	Typical Value / Published Spec
Maximum turning diameter (over bed)	~ Ø 400 mm (varies by version)
Maximum turning length (Z-axis)	~ 500 mm or more (depending on model)
X-axis travel (cross slide)	~ 200 mm
Z-axis travel	~ 500 mm (or model variant)
Spindle bore / bar capacity	~ Ø 60 mm or specified value
Spindle speed	Up to several thousand rpm (e.g. 4,000–5,000 rpm)
Spindle motor power	~ 11 – 22 kW (depending on variant)
Tool turret / tool post	Some versions may have turret with driven tools or B-axis
Rapid feed rates	As per control / drive limits
Control type	Fanuc / Siemens / Fagor / COMEV’s own integration

These reference values help calibrate your expectations and guide acceptance thresholds. If the used machine deviates significantly without documented modifications, treat that as a red flag.

2) Document Request Before Visit

Ask the seller to supply:

Serial number, manufacture year, and full configuration / build sheet
Maintenance / service logs (major repairs, spindle rebuilds, axis servicing)
Calibration or test / geometry reports (ballbar, straightness, runout tests)
CNC control and software version, parameter file backups
Electrical, hydraulic, pneumatic, and wiring schematics
Tooling list (turret, driven tools, holders)
Modification or retrofit records
Alarm / fault history logs

These help you judge how far the machine may have drifted from original specs or whether modifications have introduced unknown risks.

3) Static & Visual Inspection (Machine Off)

Conduct a thorough visual inspection before powering up:

Frame & base / casting: inspect for cracks, weld repairs, distortion, or impact damage
Way covers / bellows / guards: examine for tears, signs of chip damage, missing sections, hardened residue
Turret / tool post area: check for wear, play, misalignment, gripper damage
Spindle nose / taper / barrel: look for corrosion, scratches, pitting, surface wear
Guideways / slides / cross slide: inspect for scoring, pits, uneven lubricant traces
Tailstock or steady rest (if equipped): assess alignment surfaces, mounting, wear
Coolant / hydraulic / pneumatic lines: check for leaks, brittle hoses, repaired sections
Cable carriers / wiring harnesses: inspect for insulation damage, signs of chafing, repair patches
Electrical cabinet / wiring: open panels and inspect for burnt marks, discolored wires, modifications, dust/dirt buildup
Safety covers / interlocks / doors: test fit, check switch mechanisms, hinges

Photograph all concerning areas for documentation and later negotiation.

4) Installation & Alignment Checks

If the machine is already partially installed:

Check machine leveling and tightness of foundation bolts
Use a dial indicator or test bar to measure spindle radial runout in neutral configuration
Jog X and Z axes through small motions and check for smooth movement without binding
Index turret (if applicable) and measure deviation in tool position relative to spindle axis
If tailstock or steady rest are present, align them and check them relative to spindle axis

5) Power-Up & Functional Motion Tests

Once powering and safety checks are done:

Warm-up jogging: move axes continuously for ~20–30 minutes to stabilize system
Home / zero return cycles: ensure consistent referencing and no limit / reference errors
Axis travel test: move X, Z at various speeds (25 %, 50 %, 100 %) and listen / feel for binding or irregularities
Turret / tool change cycles: if the lathe is equipped with turret, exercise indexing, tool changes, check for mis-index or alarm
Spindle ramp-up test: gradually accelerate the spindle through its rpm range while monitoring vibration, current draw, noise, and temperature behavior
Coolant / lubrication systems: activate coolant pump, verify flow, test for leaks, confirm lube to axes
Controls & alarms: review alarm history, provoke mild fault scenarios to test error detection capability
Encoder / feedback test: move axes and verify no encoder dropouts or fault messages during motion

6) Accuracy, Repeatability & Metrology Tests

These tests separate a high-quality used machine from one with excessive wear:

Use a laser interferometer or precision gauge to measure linear positioning error on X and Z axes
Perform backlash / reversal error test: ±0.01 mm commanded moves, measure the direction reversal error
Execute repeatability test: return to a point 10× (or more) and measure deviation
For turret-equipped units, index repeated times and measure tool location repeatability
Perform a combined turning + milling test (if machine supports live tools or driven tools) and compare actual part dimensions to intended program
After prolonged operation (1 hour), remeasure reference features to detect thermal drift
Move to a point, dwell, return, and measure offset for hysteresis / drift

7) Spindle, Tooling & Wear Evaluation

Mount a test bar in spindle and measure radial runout
Use vibration analyzer or listen for bearing noise at intermediate — high rpms
Run spindle under continuous operation for 30 minutes and watch temperature rise
Test tool retention or tool holding mechanism (pull-out or torque test)
Use blue / dye test to check taper contact uniformity
Cycle tool changes and verify tool offset repeatability
If live tool features exist, test for runout, vibration, and repeatability

8) Lubrication, Cooling & Auxiliary Systems Inspection

Ensure lubrication lines deliver oil / grease to all axes; check for blockages, leaks, or dry spots
Run coolant pump; verify flow, pressure, cleanliness, and leak points
Check filters, tubing, tanks for corrosion, clogs, or debris
Operate chip conveyor if present; check for smooth motion, alignment, and no jamming
Test hydraulic / pneumatic systems (if used) to confirm stable pressures and responsiveness
Inspect electrical cabinet cooling fans, vents, and cooling performance during prolonged operation

9) Common Wear / Failure Modes & Red Flags

Guideway wear or scoring, especially in mid-travel zones
Turret indexing play or mis-index
Spindle bearing fatigue or vibration
Tool changer or gripper wear or slop
Coolant leaks into structural or mechanical areas
Loss of lubrication, clogged lube circuits
Encoder or feedback errors / dropouts
Electrical / servo drive aging, heat stress, component failure
Cable harness fatigue or damage, connector corrosion

If multiple such signs appear, the machine carries higher risk.

10) Acceptance Criteria & Benchmark Tolerances

Here is a sample table of tolerances to compare against (modify per spec sheet):

Parameter	Target / Acceptable Tolerance
Linear positioning accuracy (X, Z)	± 0.005 mm
Backlash / reversal error	≤ 0.01 mm
Repeatability (X, Z)	± 0.005 mm or better
Turret / tool offset repeatability	≤ 0.01 mm
Spindle radial runout	≤ 0.005 mm
Thermal drift over 1 hour	≤ 5 µm
Tool change / offset repeatability	≤ 0.01 mm
Coolant / lubrication stability	No significant pressure drop
Servo / current stability	Smooth traces, no spikes
Vibration / noise at rpms	Minimal — no bearing noise spikes