1) Overview

• Manufacturer: TOS Kuřim / TOS Olomouc / TOS Group (Czech Republic)
• Model: FSS 80 CNC A / A3
• Machine Type: CNC Bed-Type Milling Machine
• Table Size: Approx. 3000 × 800 mm
• Design Concept: Heavy-duty, fixed bed and movable column design with precision box or linear guideways, high rigidity, and large work envelope for heavy and long workpieces.
• Typical Applications: Precision machining of dies, molds, base plates, heavy castings, and machine structures.
• Key Strength: Czech-engineered castings, precision scraping, and long-term geometric stability.

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2) Documentation & Pre-Purchase Checklist

Request from the seller before physical inspection:

• Machine serial number & build year.
• CNC Control type: Heidenhain TNC 426/430, Siemens 840D, or Fanuc 0i-M.
• Original build sheet with spindle power, table travel (X/Y/Z), feed rates, and rapid traverse speeds.
• Maintenance & calibration records: ball-screw replacement, spindle rebuild, linear guide inspections.
• Geometry inspection reports (ISO 230-2 or VDI/DGQ).
• PLC parameter backups and control software versions.
• Tooling and accessories: universal milling head, rotary table, coolant tank, chip conveyor, guarding.

Avoid units without geometry certificates or those with partial control retrofits and missing ladder backups.

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3) Bed, Column & Table Assembly Inspection

Bed & Ways

• Examine bed casting for cracks, repairs, or epoxy fillers — especially near mounting bolts.
• Check flatness of X-axis bedways with straight edge and dial gauge (< 0.02 mm deviation per 1000 mm).
• Inspect guideway lubrication lines — oil must reach both saddle and table areas.
• Confirm bed leveling pads are intact and evenly loaded.

Table

• Inspect for dings, scoring, or warping.
• Measure table parallelism with granite straight edge and test indicator — ≤ 0.01 mm per 300 mm ideal.
• Move the table fully in X-direction to test smoothness and backlash.

Column & Saddle

• Move Y-axis through full stroke — ensure uniform motor sound and smooth hydraulic damping.
• Check for column twist or sag by measuring spindle axis alignment to table (≤ 0.02 mm per 500 mm).
• Inspect ball-screw supports and couplings for vibration or play.

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4) Spindle & Headstock Evaluation

Spindle Condition

• Check radial runout using a test bar:
  • ≤ 0.005 mm (near nose)
  • ≤ 0.01 mm (300 mm out)
• Verify spindle taper condition (ISO 50 or BT 50): no fretting, pitting, or discoloration.
• Measure drawbar force with gauge — should meet OEM spec (usually 15–20 kN).
• Run spindle at 500, 1500, 3000 rpm — listen for bearing rumble, temperature rise < 10°C.
• Check spindle chiller or oil lubrication system flow and cleanliness.

Head Tilting / Swivel (A or A3 Variant)

• Inspect the swivel mechanism for mechanical backlash or hydraulic leakage.
• Confirm smooth rotation and precise indexing angles (±0.005° tolerance).
• Operate head tilt via control panel — check servo synchronization and encoder feedback.

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5) CNC Control & Electronics

• Identify the control system (Heidenhain, Fanuc, Siemens).
• Verify boot-up without alarms.
• Test all axes’ manual jogs and reference homing.
• Check axis error history and servo diagnostics.
• Confirm data backup and network or RS-232 communication works.
• Inspect electrical cabinet:
  • Clean filters and operational fans.
  • No burnt connectors or loose terminals.
  • Stable 24VDC control supply and grounding continuity.

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6) Ball Screws, Servo Drives & Feed Systems

• Jog all axes at 25%, 50%, and 100% feed rates — check for vibration or lag.
• Inspect ball screw nuts for backlash (≤ 0.02 mm).
• Run a static backlash test using a 0.001 mm dial indicator.
• Listen for servo resonance or encoder noise.
• Verify lubrication system cycles automatically (manual test override if available).

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7) Hydraulic, Lubrication & Cooling Systems

• Hydraulics: inspect pressure (approx. 45–55 bar), hoses, and cylinder seals.
• Lubrication: ensure metering valves deliver oil to each lubrication point.
• Coolant System: check tank cleanliness, pump performance, and coolant flow at spindle and table wash.
• Way Covers: inspect seals for leaks and debris ingress.

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8) Geometry & Accuracy Tests

Test Item	Method	Acceptable Value
Table flatness	Straight edge & dial	≤ 0.02 mm / 1000 mm
Spindle to table squareness (Y/Z)	Indicator sweep	≤ 0.02 mm / 300 mm
Axis backlash (X/Y/Z)	Dial test	≤ 0.02 mm
Positioning accuracy	Laser or ballbar	≤ ±0.005 mm
Repeatability	Laser	≤ ±0.003 mm
Spindle runout	Test bar	≤ 0.005 mm
Thermal drift (1 h)	Probe test	≤ 0.01 mm

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9) Functional Performance Tests

• Dry run program: execute rapid traverses to verify full-stroke travel and limit switches.
• Circular interpolation test: perform with 100 mm radius; deviation ≤ 15 µm ideal.
• Cutting test: mill a 200 × 200 mm square pocket and measure side taper (< 0.01 mm).
• Vibration test: monitor spindle and table during heavy cut — check amplitude ≤ 1.5 mm/s RMS.
• Spindle load test: run full-speed with load — no overload alarms.

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10) Wear & Maintenance Indicators

Component	Typical Service Life	Signs of Wear
Spindle bearings	15,000–20,000 h	Noise, heat
Ball screws	25,000 h	Backlash, drift
Servo couplings	10,000 h	Vibration
Way covers & seals	5,000 h	Oil leaks
Coolant pump	8,000 h	Cavitation
Tilting head worm gears	20,000 h	Indexing error

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11) Acceptance & Run-Off Checklist

Test	Target	Result
X/Y/Z backlash	≤ 0.02 mm
Spindle runout	≤ 0.005 mm
Positioning accuracy	≤ ±0.005 mm
Squareness	≤ 0.02 mm
Head swivel repeatability	≤ 0.005°
Coolant flow	Adequate
Control alarms	None

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12) Common Weak Points in Used FSS 80 Machines

• Y-axis ball screw wear (especially on long-travel 3 m versions).
• Head tilting hydraulic seal leaks on A/A3 variants.
• Spindle chiller failure leading to thermal drift.
• Way lubrication clogging due to dried oil or improper maintenance.
• Electrical cabinet overheating if filters neglected.
• Old Heidenhain encoder drift or display flickering on aged TNC 426 units.

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13) Summary of Evaluation Criteria

Category	Excellent	Acceptable
Bed Casting	No cracks, perfect geometry	Minor cosmetic marks
Spindle	< 0.005 mm runout	Slight hum, < 0.01 mm
Axis Backlash	≤ 0.01 mm	≤ 0.02 mm
Head Swivel	±0.003°	±0.01°
Control & Drives	Error-free	Minor encoder warnings
Coolant & Lube	Clean, active	Minor leak
Accuracy	ISO 230-2 compliant	Slight deviation acceptable

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14) Final Verdict

A TOS FSS 80 CNC A/A3 3-Meter Bed Type Milling Machine, proudly made in the Czech Republic, stands as a benchmark in European precision engineering — built for longevity, rigidity, and high-load capacity.

With proper maintenance and verified geometry, a well-kept FSS 80 CNC can deliver:

• Exceptional accuracy for heavy-duty jobs
• Thermal and structural stability for long workpieces
• Smooth CNC operation with Heidenhain or Siemens controls

A verified machine with documented calibration, tight spindle tolerance, and healthy lubrication system remains one of the best European heavy bed mills in the secondhand market.