Below is a Technical Buyer’s / Due-Diligence Handbook / Inspection Checklist tailored for evaluating a pre-owned / used / surplus KRAFT VM3018A (Double Column / Planer-type / large CNC milling / gantry style machine). Use this as a structured guide; you’ll need to adapt tolerances, priorities, and weighting to your shop’s part size, accuracy requirements, and maintenance capability.

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I. Reference / Benchmark Specifications (KRAFT VM3018A)

Before arriving, assemble the nominal / expected specs (or the seller’s spec sheet) for comparison. From the listing we saw:

Parameter	Quoted / Typical Value
X-travel	3,200 mm
Y-travel	2,000 mm
Z-travel	1,000 mm
Distance spindle nose to table	200–1,200 mm
Distance between columns	1,820 mm
Table size	3,200 × 1,600 mm
Table load capacity	10 tons
Spindle taper / nose	BT 50
Spindle speed (direct drive)	6,000 rpm
Spindle motor power	22 kW
Rapid traverse (X/Y/Z)	20 / 20 / 12 m/min
Positioning accuracy	0.025 mm
Repeatability	0.02 mm
Total power requirement	60 kVA
Approximate weight	26 tons
Footprint / dimensions	~ 8,927 mm length × 5,535 mm width × 4,650 mm height

These serve as a baseline. If the unit you’re evaluating deviates significantly (e.g. much slower spindle, reduced travel, lower load rating), you’ll need to understand why (wear, modifications, motor downgrade) and factor the risk.

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II. Pre-Inspection / Remote Preparation

Before going to inspect on-site, do as much preparation as possible:

1. Request documentation
    - Manufacturer’s mechanical, electrical, hydraulic (if any) manuals
    - Wiring diagrams, control wiring / I/O drawings, axis drive schematics
    - CNC / controller parameter backups (e.g. offsets, compensation tables)
    - Maintenance / service logs: breakdowns, part replacements (spindles, linear guides, screws)
    - Calibration / alignment / geometric measurement reports
    - Modification / retrofit records (e.g. controller upgrade, spindle changes)
    - Spare parts / BOM list
2. Obtain photos & videos
    Ask the seller for high-resolution images or short video clips showing:
    - Entire machine (front / back / side)
    - Table surface and underside
    - Linear guides, column faces, reference surfaces
    - Spindle head and nose, tool change area
    - Control cabinet interior, wiring, drive modules
    - Motion videos (X, Y, Z axis jogging, spindle run) if machine is operational
3. Ask key clarifying questions
    - Year of manufacture, serial number
    - Total running hours / duty cycle
    - Usage profile (type of parts, loads)
    - Reason for sale / decommission
    - Known defects, accident history, repairs
    - Is the machine currently operational / powered?
    - What spare parts / tooling / fixtures are included
    - Which controller (Fanuc, Siemens, etc) and version
4. Bring inspection / measurement tools
    - Dial indicators, test bars, micrometers, straight edges
    - Laser alignment tools (if available)
    - Vibration sensor / accelerometer
    - Thermography / infrared camera
    - Torque wrenches, feeler gauges
    - Tools for opening panels, measuring wiring continuity, etc
5. Check logistics & facility constraints
    - Weight and rigging / crane access, lifting points
    - Foundation / floor bearing capacity, flatness
    - Power supply, voltage, phase, capacity
    - Cooling, ventilation, exhaust, auxiliary services
    - Room / clearance for movement, service, and access

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III. Visual & Structural / Static Inspection (Power-Off)

Once on-site, before powering, perform a thorough structural and mechanical inspection.

3.1 Frame, Columns & Base

• Inspect base, bed, columns, cross beams for cracks, weld repairs, distortion, bending
• Look for signs of rework, leveling shims or alignment repairs
• Check for corrosion, pitting, surface degradation in coolant / chip areas
• Inspect covers, guarding, way covers, bellows, seals for damage or missing parts
• Use a straight edge to spot obvious large-scale twist or misalignment

3.2 Linear Guides, Rails, Carriages, Ball Screws

• Inspect guide rails / ways for scoring, nicks, wear, spalling
• Check carriages for play, looseness, side movement
• Examine ball screws or drive screws / nuts for backlash, wear, pitting
• If possible, manually slide axes (light push) to sense binding, stick-slip behavior
• Check lubrication system: oil / grease lines, fittings, blockages, leaks

3.3 Spindle Head, Nose, Tool Interface

• Inspect the spindle nose / taper / clamping surfaces for wear, damage, burrs
• Check spindle head housing, bearings, seals for leakage, discoloration
• If possible, insert a test bar (without spinning) to measure static run-out
• Inspect cooling / lubrication lines to spindle, check for leakage or blockage

3.4 Tool Changer, Magazine (if applicable)

• Inspect tool changer arms, grippers, slides, indexing mechanisms for wear, slack
• Check sensors, mechanical limit switches, wiring, actuator hardware
• Inspect magazine pockets and interface alignment

3.5 Electrical Cabinets & Drive Hardware

• Open control / drive cabinets (if allowed) and inspect wiring, terminal blocks, connectors
• Look for signs of overheating: discolored wires, melted insulation, corrosion
• Check drive modules, power modules, control boards for obvious damage or dust buildup
• Inspect cooling fans, filters, ventilation pathways
• Inspect cable carriers / drag chains for damage / abrasion

3.6 Safety Systems & Interlocks

• Confirm presence and mechanical integrity of emergency stop (E-stop) buttons
• Inspect guard doors, interlock switches, safety covers
• Verify that safety circuits are not bypassed
• Check limit / home switches for axes

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IV. Power-Up & Functional / Dynamic Testing

Once static checks pass (or are acceptable with caveats) and safety is assured, proceed with controlled power-up and dynamic tests.

4.1 Control & Diagnostic Check

• Power on the CNC / control; observe boot, error messages, alarms
• Verify that CNC parameters, offsets, compensation tables load correctly
• Check I/O input states: limit/home switches, safety interlocks, sensors
• Jog axes at low speed; confirm correct direction, smooth motion, no binding

4.2 Homing / Referencing / Return-to-Zero

• Execute homing / referencing cycles on X, Y, Z axes
• Repeat homing multiple times to test repeatability of reference position
• Test limit switches / soft limits to see if axes stop or retract properly

4.3 Axis Travel & Motion Behavior

• Traverse axes across full available travel (within safe limits); watch for jerk, binding, vibrations
• Command known distance moves (e.g. 100 mm, 200 mm) and measure with a dial gauge or reference
• Reverse direction and check for backlash / dead-zone
• Execute simultaneous multi-axis moves (e.g. diagonal) to test coordination, if control supports

4.4 Spindle / Rotation Test

• Start spindle at low RPM; observe behavior, noises, vibration
• Ramp up to higher rpm (within spec) and monitor stability
• If possible, measure dynamic run-out with a test bar during rotation
• Monitor spindle motor current and temperature
• Confirm spindle cooling / lubrication works under motion

4.5 Tool Change / ATC (if present) Test

• Execute multiple tool changes; observe timing, sensor detection, indexing accuracy
• Cycle tool changes many times to test reliability and repeatability
• Try changes with different tool sizes / weights (within safe limits)

4.6 Test Cut / Machining Simulation (if allowed)

• Run a light machining test on a soft material (e.g. aluminum)
• Compare part geometry vs programmed geometry, inspect surface finish
• Let the machine run for some time (30–60 min) to observe drift, thermal effects
• Monitor power draw, vibration, deviations over time

4.7 Safety / Fault Behavior Tests

• Press E-stop during axis motion or spindle run; machine must stop safely
• Trigger limit switches or home switches to test safe behavior
• Simulate sensor failures (if safe) to see how control handles errors
• Open guards or safety doors during motion (if system supports) to see if inhibition / interlock works

4.8 Stability / Endurance / Thermal Testing

• Run repeated cycles or idle operation for long duration (30–60 min) to let temperature stabilize
• After warm-up, re-check key positioning, backlash, repeatability to detect shift
• Monitor drive / motor / control cabinet temperatures
• Use thermography or vibration analysis to find hot spots or developing issues

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V. Precision, Calibration & Accuracy Testing

Once the machine is thermally stable, conduct precision tests to assess whether performance meets your tolerances.

• Repeatability test: move to a point, retract, return, measure deviation
• Grid / mesh test: command an array of positions (X–Y) and measure resulting positional errors
• Squareness / orthogonality check: move in X then Y and Y then X, compare positional differences
• Spindle alignment / overlay: test whether spindle center line aligns with axes over travel
• Under load or offset part positions, observe whether deflection or deviation occurs
• If you have high-precision tools (laser interferometer, alignment fixtures), use them for error mapping
• Compare measured deviations vs acceptable tolerances (based on application or machine specs)

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VI. Documentation & Maintenance History Review

Once mechanical and dynamic tests are done, review the documentation and service history carefully.

• Service / maintenance logs: major repairs, overhauls (spindle, guides, drive modules)
• Calibration / alignment / compensation reports
• Upgrade / refurbishment records
• CNC / controller software / version history, backups
• Spare parts inventory included (bearings, screws, electrical modules)
• Tooling, fixtures, accessories supplied

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VII. Risk Assessment, Life-Remaining Estimate & Cost Projection

Using your inspection and test data, build a risk / cost forecast model.

• Wear-critical subsystems: linear guides, ball screws, spindle bearings, tool changer
• Spare part availability / cost: for KRAFT or OEM parts, electrical modules, drive units
• Calibration / re-adjustment cost post relocation / installation
• Transport / installation risk (misalignment, shock, packaging damage)
• Commissioning / ramp-up downtime cost
• Control / electronics obsolescence: drive boards, controller modules aging
• Fallback / salvage value: structural parts, frames, non-wear components

You may assign weights to subsystems (structure, axes, spindle, control, tooling) to derive a condition score that guides your maximum acceptable price or repair buffer.

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VIII. Contractual Safeguards & Negotiation Clauses

Use your due diligence to negotiate protections in the purchase agreement.

• Acceptance / test clause: tie final acceptance to passing performance tests after installation
• Price adjustment clause: allow deductions if key metrics deviate from agreed tolerances
• Warranty / latent defect clause: e.g. 3–6 months on hidden failures (e.g. spindle, drives)
• Spare parts package: require inclusion of critical wear parts (bearings, screws, seals, electrical modules)
• Documentation handover guarantee: all manuals, wiring, parameter backups, calibration records
• Transport / insurance clause: specifically assign responsibility for damage during transit / unloading
• Installation / commissioning support clause: seller or OEM technician support first alignment / calibration

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IX. Post-Purchase / Installation & Commissioning Checklist

Once the machine is delivered and installed in your facility, follow a careful commissioning process:

1. Prepare and level the foundation, anchor points, vibration isolation
2. Clean, flush, and refill lubrication / coolant systems; replace filters as needed
3. Reconnect and verify wiring, grounding, and safety systems
4. Power up and repeat the acceptance / functional / precision test suite
5. Perform alignment, geometry calibration, compensation (straightness, squareness, backlash)
6. Run test parts using your materials to confirm real-world performance
7. Capture baseline metrics (repeatability, drift, backlash)
8. Train operators & maintenance staff on machine idiosyncrasies
9. Establish preventive maintenance schedule (e.g. periodic alignment checks, lubrication audits)
10. Monitor performance in early weeks: drift, alarms, deviations