1. Preliminary Checks & Documentation

Before touching the machine:

• Model verification: Confirm that the machine is indeed a Microrex Dinatec “2H CNC2” (or variant). Get the serial number, build date, any modifications done, and factory options.
• Factory specifications: Try to obtain original specification sheet (travel ranges, wheelhead capacity, spindle speeds, table size, coolant, etc.) for “as new” reference.
• Service / maintenance history: Ask for records showing repairs, overhauls, parts replaced, spindle rebuilds, etc. A well-documented history is a strong plus.
• Usage history: What type of work was done on it (high volume, heavy cuts, light finishing)? Was it a “production grinder” or for occasional use?
• Environmental conditions: Was it located in a clean, climate-controlled shop, or in a dusty, humid, or corrosive environment?
• Parts availability: Check how easily replacement parts (spindles, bearings, motors, servo drives, control modules) can be sourced.
• Spare components included: Sometimes sellers include spare spindle bearings, tooling, fixtures, scrapers, probes, cables, etc. That adds value.

If the documentation is missing or incomplete, you’ll need to put greater emphasis on hands-on inspection and measurement.

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2. Structural, Castings & Bed / Column / Base

These are the “bones” that determine rigidity, alignment stability, and long-term geometric accuracy.

• Visual inspection
  • Look for cracks, weld repairs, deformation, or modifications in base, columns, saddle, cross slide, and wheelhead casting.
  • Check that surfaces are not “dropped” or worn through re-surfacing or re-machining.
  • Inspect for corrosion, pitting, scale, or damage in cast structures.
• Flatness / straightness of guide surfaces
  • Use straightedges, precision levels, dial test indicators (DTI), or surface plates to check the flatness of ways, decks, guide surfaces, slide faces.
  • Look for wear bands, depressions, or “cupping.”
  • In many machines, the table bed ways and cross slide ways are hardened; wear here is critical.
• Rigidity & stiffness
  • Try applying a moderate force (by hand or via a test tool) at various points of movable parts (table, cross slide, wheelhead) and observe deflection or bounce. Excessive play is a red flag.
  • Check for any looseness in joint zones, bolted connections, braces.
• Fasteners / alignment bolts
  • Check that structural bolts (e.g. those securing column to base, or cross slide to saddle) are all present, properly torqued, and not stretched or damaged.

If a structural component is out of tolerance, repairing or re-scraping may be expensive or impractical.

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3. Motion, Axes, Drives, Ballscrews / Linear Guides

This section covers how accurately and smoothly the machine moves in each axis (X, Z, possibly Y or C, depending on the variant).

• Backlash / reversal errors / hysteresis
  • Use a calibrated dial indicator, test probe, or laser linear calibration tool. Move each axis back and forth and measure deviations.
  • Check over full stroke and near ends.
• Straightness / squareness / orthogonality
  • For example, move a test bar or reference cylinder, mount a test indicator, and check how straight the motion is.
  • Check squareness between axes (X vs Z) using gage blocks or square standards.
• Ballscrew / lead screw condition
  • Listen and feel for unevenness, binding, chatter, or wear along the screw travel.
  • Check for backlash between nut and screw.
  • If possible, disassemble (or inspect accessible parts) to see screw threads, nut condition, lubrication, and wear.
• Linear guide / ways / roller bearings
  • Many modern CNC cylindrical grinders use linear guides, box ways, or V/flat combinations. Check for wear, scratches, brinelling, or pitting.
  • Use feeler gauges or test indicators to check guide clearance.
• Servo / drive feedback / encoder
  • Inspect the feedback encoders, scale systems, and wiring. Any damage or error signals must be checked.
  • Verify that drive motors engage smoothly, with no jerks, hesitations, or fault lights.

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4. Spindle(s), Wheelhead, & Workhead

This is one of the most critical systems for grinding, as spindle precision largely dictates surface finish, roundness, concentricity.

• Spindle runout / radial & axial play
  • Mount a precision test bar or mandrel and measure runout relative to tailstock or fixture.
  • Check axial (thrust) play by pushing/pulling the spindle nose or wheel arbor.
• Bearing condition
  • Listen for noise when spinning the spindle (induced by hand or low-speed).
  • Feel for smoothness; any “grittiness,” rumbles, or binding are warning signs.
  • Inspect for signs of oil leakage or contamination at bearing seals.
• Wheelhead travel & infeed functionality
  • Check that the wheelhead (infeed axis) moves as expected, both coarse and fine, smoothly and without backlash.
  • Check the travel limit switches, sensors, and stops.
• Wheel arbor / flange / balancing
  • Inspect the condition of wheel flanges and arbors (wear, scoring, corrosion).
  • Check for keyways or locking features; ensure they are not excessively worn.
  • If possible, check the spindle’s balancing capability (whether it has balance ports or balancing weights).
• Wheel dressing system
  • Inspect the diamond dresser / dresser holder, travel, condition, and control.
  • Check whether the dressing is automatic and whether it still functions properly.
• Workhead / chuck / centers
  • Inspect the workhead spindle or chuck for runout, play, and bearing health.
  • If the head is capable of swiveling, check that the swivel mechanism is solid, repeatable, and has locking strength.
  • If tailstock is present (or steady rests), check their alignment, travel, locking, taper integrity, and condition.

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5. Control, CNC, Electronics, Wiring & Software

A CNC grinder’s value strongly depends on its control and electronics health.

• CNC control & drive systems
  • Power it on and see whether the controller boots without errors.
  • Check whether the machine memory, parameter storage, and user interface are working correctly (no crash logs, corrupt data, flashing errors).
  • Check motion commands: jogging, manual override, cycle start, interrupts, etc.
  • Check whether all axes respond correctly, limit switches, emergency stops, safety interlocks.
  • Test any probing, in-process measurement, or feedback loops.
• Servo drives, inverters, amplifiers
  • Visually inspect drive units, capacitors, wiring, cooling fans. Look for blown components, bulging caps, burned smell, loose connectors.
  • Check the interface between CNC and drives (communication signals: pulse streams, encoder feedback).
• Electrical panel & wiring
  • Check wire insulation, connections, cleanliness, labels, and shielding.
  • Look for signs of overheating (discoloration, burnt insulation).
  • Check condition of contactors, relays, fuses, circuit breakers.
• Sensors, limit switches, encoders
  • Confirm that all sensors, limit switches, home switches, and proximity switches function and are properly aligned.
  • Check encoder scale readings, whether any broken scale lines or damaged glass scales.
• Software & CNC program integrity
  • See whether there are hidden modifications, “hacks,” or obsolete firmware.
  • Check that interpolation, compensation (e.g. wheel wear, thermal drift compensation) functions work properly.
• Backup & diagnostics
  • Ask for any diagnostic logs, error histories, backup files, and check whether the controller allows backups or transfers.
  • Check whether the vendor / manufacturer supports the control version (e.g. spare modules, software updates).

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6. Hydraulics, Pneumatics, Lubrication, Coolant & Fluids

These “support systems” are essential for stable precision operation over time.

• Fluid system condition
  • Inspect the coolant tank, hoses, pumps, filters, and piping for leaks, rust, sludge, contamination, or damage.
  • Drain and inspect coolant (if possible) to see how dirty or degraded it is.
  • Check coolant flow rates, pressure, and whether the spray nozzles are working and well aligned.
• Hydraulic / pneumatic systems
  • Inspect hydraulic pumps, reservoirs, cylinders, hoses, seals, and lines. Look for leaks or worn seals.
  • Test hydraulic pressure (if gauge available) and ensure it’s stable and within specification.
  • Check pneumatic lines, valves, and air dryness / lubrication (if applicable).
• Lubrication / grease / oil circuits
  • Check the condition of lubrication pumps, lines, oil reservoirs, filters, and automatic lubrication timers.
  • Inspect slide way oil, screw nuts, bearings, etc., for whether they’ve been consistently fed with oil/grease.
  • Verify whether oil cleanliness is acceptable (no metal shavings or contamination).
• Cooling & temperature control
  • Confirm heat exchangers, chillers (if any), or cooling systems are functional.
  • If the machine has thermal compensation systems or temperature feedback, verify that they work.

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7. Test / Functional / Grinding Tests

Once mechanical and electrical systems pass inspection, it’s crucial to run test cuts to validate real performance.

• Warm-up & stability
  • Run the machine idle through all axes over full travel for a period (30 minutes or more) to see if anything loosens, overheating, noise appears, or drift occurs.
  • Monitor temperature of spindle bearings, drives, and motors under idle and during movement.
• “Blue & grind” test pieces
  • Use Engineer’s blue (Prussian blue) or spotting compound on a test bar or workpiece, grind it lightly, and see how uniformly the blue is removed. This gives insight into surface contact, alignment, and table/travel variation (a method used for surface grinders as well).
• Roundness / cylindricity test
  • Grind a cylindrical test bar (or reference gauge) along its length and check roundness and cylindricity using a roundness tester, high-precision CMM, or statically mounted dial indicators.
  • Compare the result versus machine’s original specification (e.g. ±2 μm, ±5 μm, etc.).
• Surface finish test
  • After grinding, measure surface roughness (e.g. Ra) and check whether the finish meets target specifications.
• Load / heavy cut test
  • Try a heavier cut or grinding on a real workpiece to verify that the machine does not chatter, deflect, or lose accuracy under load.
• Wheel dressing & repeatability test
  • Dress the wheel and then grind again; see whether setup, measurement, and repeatability hold.
• Command / servo response test
  • Change feed rates, see acceleration / deceleration performance, check for overshoot or oscillations.

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8. Alignment, Geometry & Leveling

Even a “good” machine can deliver poor results if it’s misaligned or poorly leveled.

• Machine leveling & foundation
  • Check whether the original mounting pads / leveling feet are intact and functional.
  • Inspect whether the installed leveling was properly done (use precision levels, granite surface plates).
• Axis alignment & tramming
  • Use precision squares, test bars, or dial indicators to confirm that spindle axis, table axis, tailstock, and wheelhead axes are properly aligned in terms of parallelism, perpendicularity, and coaxiality.
• Thermal drift checks
  • After long operational time, check for any drift in geometry or alignment (i.e. as machine warms up).
  • Some grinders may have thermal compensation; verify that function if present.

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9. Safety, Guards, Covers & Accessories

Don’t neglect safety, as missing or damaged guards reduce usability or may violate regulations.

• Machine enclosures & guards
  • Check that splash guards, covers, chip shields, access doors, and interlocks are in place and functioning.
• Electrical safety & grounding
  • Inspect grounding continuity, insulation resistance tests (megger test if possible), protective earth wiring.
• Emergency stop & safety interlocks
  • Confirm that E-stop, safety doors, interlocks, and limit switches operate correctly.
• Accessories & fixturing integrity
  • Inspect chucks, fixtures, centers, steady rest, and workholding devices included.
  • Check their condition (wear, alignment, damage) and whether they match your intended use.

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10. Economic, Risk & Long-Term Considerations

Finally, aside from technical fitness, evaluate the commercial viability and risk.

• Remaining life / “wear budget”
  • Based on your measurements (e.g. wear of ball screws, spindle bearings), estimate how much service life is left before a major overhaul is needed.
• Cost of refurb / repair vs new / better used alternative
  • Estimate cost to bring machine up to “good” performance (spindles, bearings, wiring, re-scraping, control module replacement) and compare to buying a better used unit or a new one.
• Obsolescence / salvage value
  • Consider whether the control, parts, or modules might become obsolete.
• Transport, reinstallation & levelling cost
  • Large grinding machines are heavy and delicate. Consider rigging costs, alignment / setup costs at your site.
• Warranty, seller reputation, return / performance guarantee
  • If possible, negotiate a conditional acceptance or a limited “run-in” guarantee period.
• Risk of hidden issues
  • Even with many checks, issues may appear only under long-term load. Be conservative in valuation and assume a margin for surprises.

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11. Checklist Summary (Quick Reference)

System	Key Checks / Red Flags
Structure / Bed / Castings	Cracks, weld repairs, warpage, wear on guide surfaces
Axes / Motion	Backlash, binding, straightness error, ballscrew wear
Spindles / Wheelhead	Runout, bearing noise, spindle play, dress mechanism
Control / Electronics	Controller health, error logs, servo response, wiring damage
Fluids & Lubrication	Contamination, leaks, pump performance, cleanliness
Test Cuts / Accuracy	Roundness / surface finish / performance under load
Alignment & Leveling	Squareness, leveling accuracy, thermal drift
Safety / Guards / Accessories	Missing guards, safety interlocks, fixturing quality
Economic Aspects	Spare parts, remaining life, refurb cost, transport risk

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Tailoring to Microrex Dinatec 2H CNC2

While I could not find publicly documented specifications for exactly a “Microrex Dinatec 2H CNC2”, you should adapt the above guide around whatever the original spec sheet says for:

• Maximum grinding diameter & length
• Spindle speed, wheel size, wheelhead travel
• Axis travel ranges, servo ratings
• Accuracy tolerances (roundness, cylindricity, surface finish)
• Type of guideways / drive system originally used
• Control type (CNC brand / version)
• Any optional features (e.g. in-process gauging, automatic dressing, tailstock capabilities)

Ask the seller for that spec sheet, and during inspection compare what you measure vs what “as new” spec tolerances are.

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Tips & “Gotchas” Specific to Grinding Machines

• Many grinding machines are used for high throughput or tough materials; they may have been run hot, with heavy thermal loads, so thermal drift or creep damage is common.
• Grinding produces fine abrasive dust; over time, this dust can infiltrate bearings, guides, hydraulics, encoders, leading to accelerated wear. Check for signs of past contamination (grinding dust inside covers, around seals).
• Spindle overhauls are expensive — if the spindle bearings are degraded, that can be a show-stopper.
• Re-scraping or re-lapping guideways is labor-intensive and costly; avoid machines with excessive wear on slide surfaces.
• Control upgrades or replacement modules may be expensive / impossible if the control is obsolete.
• After moving the machine, alignment, leveling, and tramming can shift; ensure you or your vendor has the capability to re-align at your site.