1. Scope and purpose
This practical guide defines the schedule for preventive maintenance (PM) of multi-axis industrial robots (articulated type, payload 50-210 kg) on production enterprises in Ukraine. The procedure covers critical operations such as measuring mechanical play in the J1-J6 axis reducers, detailed inspection of cable bundles for internal and external sheathing for damage, as well as full replacement of plastic grease in the reducers and drives in accordance with industrial standards.
Maintenance is performed during planned equipment shutdowns according to operating hours (every 10 000 hours of operation or 2 years of service) or upon detection of signs of deterioration in positioning accuracy of the robot, appearance of unusual noise in the gearboxes or vibrations during trajectory movement.
2. Safety Precautions
ПОПЕРЕДЖЕННЯ: НЕБЕЗПЕКА УРАЖЕННЯ ЕЛЕКТРИЧНИМ СТРУМОМ ТА РУХОМИХ МЕХАНІЗМІВ
Перед початком будь-яких робіт виконайте процедуру Lockout/Tagout (LOTO) згідно з ДСТУ EN 1037 та ДСТУ EN ISO 12100. Повністю вимкніть живлення контролера робота та зовнішнього силового щита, заблокуйте вхідний автоматичний вимикач навісним замком та встановіть попереджувальну табличку. Зачекайте мінімум 5 хвилин після вимкнення живлення для розрядження конденсаторів проміжного контуру перетворювача частоти. Завжди використовуйте засоби індивідуального захисту (ЗІЗ): захисні окуляри згідно з ДСТУ EN 166, маслостійкі захисні рукавички та захисне взуття з металевим носком згідно з ДСТУ EN ISO 20345. Забороняється знаходитися під піднятими або незакріпленими елементами руки робота без використання механічних опорних стійок (спеціальних домкратів або фіксаторів положення).
3. Required Tools and Materials
| Найменування інструменту / матеріалу | Technical specifications | Quantity |
|---|---|---|
| Clock-type (IR) indicator with magnetic stability | Scale division 0.01 mm, range 0-10 mm | 1 pc. |
| Digital Vernier Caliper | Range 0-150 mm, accuracy 0.02 mm | 1 pc. |
| Torque wrench | Range 5-50 Nm and 20-200 Nm | 2 pcs. |
| Digital Multimeter | True RMS, category CAT III 1000V / CAT IV 600V | 1 pc. |
| Grease pump (plunger type) | Capacity 400 ml, with flexible hose | 1 pc. |
| Gear oil | Synthetic (for example, Kyodo Yushi or Harmonic Grease SK-1 / Mobilgrease XHP 222 depending on the unit) | 1-3 kg |
| Deoiling filter (non-aggressive to plastic) | Fast-drying aerosol | 2 cylinders |
| Technical non-woven wipes | Packaging 100 pcs. | 2 packages |
| Set of hex keys (Imbus) | Sizes from M3 to M12 (metric) | 1 set |
4. Pre-inspection Checklist
| Element of view | What to check | Acceptance / Rejection Criterion | Notes |
|---|---|---|---|
| Robot Body and Mechanical Connections | Presence of cracks, oil leakage traces on the hub flanges. | Acceptable: dry surfaces, no cracks. Defect: any oil leakage, cracks in the casting. | Pay special attention to the J2 and J3 axis reducers. |
| External cable distribution unit | Condition of protective corrugated pipe, fittings, absence of kinks. | Acceptable: intact housing, reliable connector retainers. Defects: abrasion to screen, corrugation cracks. | Check in areas of maximum bending (axis J2-J3). |
| Stopping Accuracy (Zero Marks) | Calibration mark overlap on robot axes. | Acceptable: marks perfectly match (error < 0.1 mm). Defect: displacement of marks more than 0.5 mm. | It is performed via the operator panel (Teach Pendant). |
5. Step-by-step procedure for performing the work
- Preparation of the work zone and energy isolation (LOTO)
- Translate the machine into a safe service position (usually vertical extended position or maintenance position, recommended by OEM).
- Turn off the main power switch of the controller.
- Install the LOTO lock on the power switch and hang the sign "Do not turn on! People are working".
- Check for residual voltage on the power connectors using a digital multimeter (DC voltage measurement mode, the value should be 0.0 V on the power supply bus).
Common error: Starting service without fully releasing residual pressure in the pneumatic system (if a balance valve or pneumatic tool is installed). Always release the pressure in the pneumatic system to 0 bar. - Measurement of mechanical play of the axes (J1 - J6)
- Mount the magnetic stand with a dial indicator on the stationary part of the robot's body near the axis to be checked (for example, the J1 axis base).
- Install the indicator tip as close as possible to the output flange of the reducer on the movable part.
- Lock the axis in the locked position (brake engaged or mechanical lock). Apply a preliminary tension of 1-2 mm to the indicator arrow and set the scale to zero.
- Apply manual force (without impacts and exceeding the normal use of levers) in two opposite directions of the shaft rotation and fix the maximum deviation of the pointer.
- Compare the obtained play value with the permissible limits (for axes J1-J3, the permissible play is no more than 0.08 - 0.12 mm on the measurement radius; for J4-J6 — no more than 0.05 - 0.08 mm). If the value exceeds the nominal by 30%, note the necessity of replacing the reducer.
Common error: Too strong pressure on the robot's hand during measurement, leading to elastic deformation of the structure, rather than determining the play in the gear itself. - Cable Harness Inspection
- Remove the protective covers and housings of the cable channels on the robot's arm and body.
- Visually and by touch, check the internal cable harnesses (motor power cables, feedback/encoder cables, pneumatic lines).
- Check the insulation condition for signs of rubbing against metallic edges or adjacent cables. Measure the insulation resistance of power cables relative to ground using a megohmmeter (test voltage 500 V DC, permissible value not less than 20 MOhm).
- Check the reliability of the connections (bayonet connections and screw clamps). Tighten the connector screws with a torque of 1.5 - 2.0 Nm.
Common error: Leaving the damaged outer sheath of the cable without replacing it with the usual insulation tape winding. In production conditions, this is inevitably leading to short circuit or encoder failure. - Заміна пластикового мастила в редукторах
- Знайдіть зливні та заливні пробкові отвори на редукторі конкретної осі згідно з технічною документацією виробника робота.
- Clean the area around the plugs using a brush and lint-free wipes to prevent abrasive material from entering the reducer.
- Remove the filler plug, then the drain plug. Place a measuring container for collecting the used oil. For acceleration of draining and reduction of viscosity, it is permissible to heat the reducer by short-term idling of the shafts (no more than 5 minutes), if the temperature does not exceed +40°C.
- After complete draining of the old oil (wait no less than 15 minutes), screw in the drain plug with a new sealing ring, tightening it to the torque value according to the torque table (usually for M8 thread — 15 Nm, for M10 thread — 30 Nm).
- Through the filling port, use a plunger syringe to fill the exact volume of new recommended manufacturer grease (for example, for shaft J3, usually between 350 and 500 ml depending on the model). Overfilling the reducer is prohibited.
- Tighten the filler plug with a torque similar to the drain plug.
Common error: Mixing different types of lubricating greases (for example, those based on lithium and polyurea thickeners). This leads to the destruction of the grease structure, loss of lubricating properties and gear reducer seizure.
6. Post-maintenance Check-list
| Тест / Перевірка | Expected result | Actual result | Status (Passed / Failed) |
|---|---|---|---|
| Checking for absence of oil leaks | Flanges and corked holes are dry, without signs of grease leakage during testing. | [ ] Yes / [ ] No | [ ] Pass / [ ] Fail |
| Insulation Resistance Test | Resistance of power circuits and signal cables > 20 MOhm (at 500 V). | [ ] Yes / [ ] No | [ ] Pass / [ ] Fail |
| Low-speed test motion (T1 mode) | Smooth motion of all axes (J1-J6) without jerks, noise, and vibrations. | [ ] Yes / [ ] No | [ ] Pass / [ ] Fail |
| Reducer Heating Check | The temperature of the reducer housings after 15 minutes of operation does not exceed +65°C. | [ ] Yes / [ ] No | [ ] Pass / [ ] Fail |
7. Troubleshooting Guide
| Symptom | Likely cause | Correction action |
|---|---|---|
| External metallic noise (humming or rattling) in the axle reducer during movement. | Tooth wear of gears, damage to bearing separator or presence of metallic chips in the used lubricant. | Stop the machine immediately. Conduct a re-inspection of the lubricating oil for the presence of wear particles. Disassemble the reducer and carry out its major repair or replacement of the assembly unit. |
| Robot controller error «Overload» (drive overload) on one of the axes. | Too large an amount of lubricating oil (hydraulic resistance) or bearing seizure. | Check the amount of grease filled, drain the excess through the drain hole. Check the free rotation of the engine shaft manually with the brakes disengaged. |
| Periodic loss of communication with the encoder or safety error (Safety Stop). | Damage or abrasion of the internal cable braid in the elbow bend area. | Perform localization of the damaged section using a multimeter. Replace the damaged cable harness segment with a new original set. |
8. Recommended Maintenance Schedule
| Завдання | Frequency | Estimated duration | Qualification Level |
|---|---|---|---|
| Checking of bearing clearances | Every 5 000 hours or 1 year | 2 years | Reliability Engineer / Senior Technician |
| Cable Harness Inspection | Every 2 500 hours or 6 months | 1.5 years | Maintenance Technician |
| Lubricant Replacement in Reducers | Every 10 000 hours or 2 years | 4 years | Senior Mechanic |
| Torque check of fastening screws | Every 5 000 hours | 1 year | Maintenance Technician |
9. Spare Parts Catalogue
| Description of the part | Typical specification | Category UNITEC |
|---|---|---|
| Cable harness assembly | Original flexible cable (power + signal) for axes J1-J6 | Electrical components and cables |
| Reducer assembly (Harmonic Drive / Planetary) | Precision reducer for industrial robot with gear ratio according to OEM | Mechanical transmissions and reducers |
| Grease for reducers | High pressure synthetic lubricant in package 1 kg | Lubricants and Technical Fluids |
| Sealing rings and glands | Oil-resistant fluorocarbon rubber (FKM) of different diameters | Seals and glands |
Are you looking for original spare parts for industrial robots or certified consumables for scheduled maintenance? Go to our electronic catalog UNITEC-D for selection by part number or contact our technical support.
10. References
- DSTU EN 1037:2019 Machinery safety. Prevention of unexpected start-up.
- DSSTU EN ISO 12100:2016 Machinery Safety. General Principles of Design. Risk Assessment and Risk Reduction.
- DSTU EN ISO 20345:2016 Personal protective equipment. Safety footwear.
- Technical documentation and maintenance manuals of industrial robot manufacturers (KUKA, ABB, Fanuc, Yaskawa).
