1. Content and purpose

This manual is intended for technicians who change and check the tire oil lubrication system on CNC machines. The purpose of performing this maintenance is to ensure efficient and safe functioning of the system, to detect possible violations and to perform necessary remedial actions. This procedure should be performed once a month or when unusual changes in oil properties or changes in lubrication are detected.

2. Preliminary security measures

Important: Block the power and install the tag lock before doing any work.

Performing work on the lubrication system may require working with high pressure, liquid oil and electrical components. To ensure safety:

• Use safety glasses, gloves and personal protective equipment (PPE).
• Perform a lock-out (LOTO) procedure to eliminate electrical or mechanical hazards.
• Check for leaks or pressure in the system.
• Do not perform work under pressure or without disconnecting the power supply.

3. Necessary tools and materials

4. Pre-service: Inspection

5. Step by step procedure

1. Power off. Follow the lock-out procedure to ensure electrical safety.

   • Error: Carrying out work without turning off the power supply may cause damage and injury.

2. Checking the pressure in the system. Use a pressure gauge to measure the pressure in the system. The pressure should be within 0.5 bar.

   • Error: High pressure can cause leakage or component damage.

3. Cleaning the filter. Open the filter, remove the backfill, rinse it with water, dry it and put it back.

   • Error: Improper cleaning may cause explosion or oil leakage.

4. Checking the pump. Use a torque wrench to check that the pump is secure. The maximum torque is 50 Nm.

   • Error: Improper locking can cause the pump to shut down or wear out.

5. Adding oil. Add oil to the level of 20-80% of the total volume. Use a toaster to check the level.

   • Error: Insufficient oil level can cause tire wear.

6. Pressure and Functionality Check. Turn on the power supply and check the pressure and noise of the pump. The pressure should be within 0.5 bar, the noise is stable.

   • Error: Increased noise may indicate a pump malfunction.

7. Fixing the components. Use the torque winch to fix all the components. Set the torque within 50 Nm.

   • Bug: Insufficient commits can lead to shutdowns or leaks.

8. Final check. Go through all steps again to ensure correct execution.

   • Error: Failure to complete may result in increased maintenance costs.

6. After-service: inspection

7. Table of problem solving

8. Recommended maintenance schedules

9. Links to spare parts

Go to the UNITEC-D catalog

10. Links

• DSTU 3026-2009 — General requirements for lubricants
• EN 12100 - Machine safety
• ISO 10426 - Lubrication systems
• CE — Common Operational Conformity
• UkrSEPRO — State certification of Ukraine

1. Description of the problem and scope

This guide is intended for diagnosing and correcting positioning errors in CNC machines that are caused by ball shaft kickback, incorrect encoder feedback, lack of thermal compensation, or incorrect servo setup. Positioning errors can affect manufacturing accuracy, part quality, and production process efficiency. According to the classification, this can be a critical problem if it affects the production of manufactured products.

2. Safe measures

Requirements for personal protective equipment: when diagnosing, it is necessary to use gloves, glasses, tools with insulation, as well as observe the rules of blocking and marking of energy.
Power Lockout and Tagout: Before performing any diagnostic operations, the machine must be powered off and the lockout and tagout must be installed.
Presence of stored energy: Before accessing mechanical components, it is necessary to check whether stored energy is present in the actuators or hydraulic systems.
Dangerous conditions: in the case of performing work in the presence of high temperatures or dangerous materials, it is necessary to use special protective equipment.

3. Necessary diagnostic tools

4. Primary assessment: Check before diagnosis

5. Systematic diagnostic scheme

1. If the machine cannot perform accurate positioning, check for ball shaft runout errors:
1. Use a vibration analyzer to measure the vibration level (allowable range: 0-4.5 mm/s).
2. Check the distance between the ball shaft and the ball rail (allowable distance: 0.01-0.03 mm).
3. If the distance does not meet the standards, adjust.
2. If the vibration measurement is above the threshold value, check the feedback system:
1. Use a multimeter to check encoder signals (acceptable voltage: 0.5–5 V).
2. Check for repulsion or malfunction of the corresponding contacts.
3. If violations are found, replace or adjust.
3. If the feedback system meets the standards, check the thermal compensation:
1. Use a thermal camera to measure the temperature of the components (acceptable temperature: 20-60°C).
2. Determine if there is a fault in the compensation or adjustment system.
3. If deviations are detected, adjust the thermal compensation system.
4. If the temperature meets the standards, check the settings of the gray drive:
1. Use a multimeter to check the gray-drive setting (acceptable voltage: 0.5–5 V).
2. Determine if there is a deviation in the setting of proportional, integral and differential control.
3. If deviations are detected, adjust the gray drive.

6. Matrix of causes of defects

7. Detailed root cause analysis

7.1. Ball shaft rebound

Ball shaft knocking occurs due to deviations in operating conditions or lack of correct adjustment. This can lead to incorrect positioning, increased vibration and energy consumption. To confirm, use a vibration analyzer and measure the distance between the ball shaft and the ball rail. If the distance is not within the allowable range (0.01-0.03 mm), adjust.

7.2. Incorrect feedback information

Incorrect feedback information occurs due to encoder malfunction or contact repulsion. This can lead to incorrect positioning and wasted energy. To confirm, use a multimeter and check the encoder output voltage. If the voltage is above the allowable range (0.5–5 V), replace or adjust.

7.3. Lack of thermal compensation

Lack of thermal compensation occurs due to lack of correct system setup or lack of temperature measurement. This can lead to incorrect positioning and wasted energy. To confirm, use a thermal camera and check the temperature of the components. If the temperature is above the allowable range (20-60°C), perform thermal compensation settings.

7.4. Incorrect gray-drive setting

Incorrect adjustment of the gray drive occurs due to deviations in the adjustment of proportional, integral and differential parameters. This can lead to incorrect positioning and wasted energy. To confirm, use a multimeter and check the gray-drive settings. If the setting is above the acceptable range (0.5–5 V), adjust the gray drive.

8. Step-by-step repair procedures

8.1. Ball shaft rebound

1. Measure the distance between the ball shaft and the ball rail. Allowable distance: 0.01–0.03 mm.
2. If the distance does not meet the standards, adjust the ball shaft or ball rail.
3. Perform the vibration measurement again to confirm the correction.
4. Note the results in the service log.

8.2. Incorrect feedback information

1. Measure the encoder output voltage. Allowable voltage: 0.5–5 V.
2. If the voltage is above the permissible range, replace the encoder or restore the contacts.
3. Measure the feedback information again to confirm the correction.
4. Note the results in the service log.

8.3. Lack of thermal compensation

1. Measure the temperature of the components. Permissible temperature: 20–60°C.
2. If the temperature is above the acceptable range, adjust the thermal compensation system.
3. Take the temperature measurement again to confirm the correction.
4. Note the results in the service log.

8.4. Incorrect gray-drive setting

1. Measure the gray actuator setting. Allowable voltage: 0.5–5 V.
2. If the setting is above the allowable range, adjust the gray drive.
3. Measure the setting again to confirm the correction.
4. Note the results in the service log.

9. Preventive measures

10. Spare parts and components

Refer to the UNITEC-D catalog for spare parts.

11. Links

This guide complies with the following standards:

• DSTU 4389:2007 — Rules for technical operation of industrial equipment
• EN 13163:2003 - Technical operation of industrial equipment
• ISO 10426-1:2004 — Rules for the operation of industrial equipment
• CE, UkrSEPRO: product certification

Additional resources:

• Original documentation of the manufacturer of CNC machines
• Other UNITEC-D guides for maintenance of CNC machines

1. Problem description and scope

This is a manual for diagnosing and correcting CNC machine positioning errors, including hinge backlash, encoder, thermal compensation, and servo setup. These problems are often encountered in the operation of industrial CNC machines used in the automotive, aerospace, food, chemical and energy industries. The importance of these errors is determined by their criticality for production quality, production safety and production efficiency.

2. Safety during diagnosis

Requirements for personal protective equipment: When diagnosing CNC machines, use protective equipment against mechanical injuries, including gloves, goggles, work clothes with high resistance to high temperatures, and electrical protective elements. When working with an electric drive, use insulating materials.

Safety measures against energy hazards: Before performing any diagnostic procedures, perform a lockout and tagout (LOTO) procedure to avoid unforeseen events. When using electrical components, check for stored energy and disconnect it before starting work.

3. Necessary diagnostic tools

4. First examination before diagnosis

5. Systematic diagnostic scheme

1. Symptom: Positioning errors during CNC machine operation
1. Check: Measure the temperature of bearings and hinges
2. If: Temperature exceeds 60°C — perform thermal compensation diagnostics
3. If: Temperature in the range of 20-50°C - perform reverse diagnosis
2. Symptom: Incorrect position or deviation from the specified position
1. Check: Measure the deflection of the hinge
2. If: Deviation exceeds 50 μm — perform reverse stroke diagnostics
3. If: Deviation within 10-50 μm - perform encoder diagnostics
3. Symptom: Positioning instability
1. Check: Measure the vibration of the mechanism
2. If: Vibration exceeds 10 mm/s - perform servo diagnostics
3. If: Vibration within 1-10 mm/s - perform thermal compensation diagnostics
4. Symptom: Errors in the feedback system
1. Check: Measure the encoder signal
2. If: The signal deviates from the nominal one - perform encoder diagnostics
3. If: The signal is within the permissible range - perform servo diagnostics

6. Matrix of causes of defects

7. Root cause analysis for each defect

7.1. Reverse reverse

Reason: Deviation of the hinge from the nominal values can be caused by worn bearings, lack of correct tension or improper assembly of components.

Diagnosis: Measure the deviation of the hinge from the nominal position. A deviation of >50 μm indicates a lack of stability in positioning.

Consequences: Positioning errors, reduced production quality, callbacks and energy waste.

7.2. Incorrect operation of the encoder

Reason: Encoder signal deviation can be caused by encoder wear, damaged cables, or incorrect settings.

Diagnosis: Measure the encoder input signal. If it deviates from the nominal value, this indicates a malfunction of the encoder.

Consequences: Unstable positioning, rejected output, decrease in product quality.

7.3. Thermal compensation

Reason: Overheating of hinges or bearings may occur due to incorrect operation mode or lack of a thermal compensation system.

Diagnosis: Measure the temperature of the bearings. If the temperature exceeds 60°C, this indicates a lack of thermal compensation.

Consequences: Component wear, energy consumption, incorrect positioning.

7.4. Incorrect servo setting

Reason: Incorrect servo setup can cause vibration, incorrect positioning, and reduced production quality.

Diagnosis: Measure the vibration of the mechanism. If it exceeds 10 mm/s, it indicates a problem in the servo.

Consequences: Unstable positioning, energy consumption, component wear.

8. Step-by-step repair procedure

8.1. Correction of reverse course

1. Measure the deviation of the hinge from the nominal position
2. If the deviation is >50 μm, replace the bearings
3. Check for correct tension and assembly of components
4. Adjust the hinge according to the technical data sheet
5. Check the positioning after correction

8.2. Encoder correction

1. Measure the encoder signal
2. If the signal deviates from the nominal one, replace the encoder
3. Check the encoder cable for the intended purpose
4. Perform encoder settings according to the technical data sheet
5. Check the positioning after correction

8.3. Correction of thermal compensation

1. Measure the temperature of the bearings
2. If the temperature exceeds 60°C, set the thermal compensation
3. Check for thermal compensation in the system
4. Perform thermal compensation settings
5. Check the positioning after correction

8.4. Servo correction

1. Measure the vibration of the mechanism
2. If the vibration is >10mm/s, adjust the servo
3. Check the servo settings
4. Adjust the servo according to the technical data sheet
5. Check the positioning after correction

9. Preventive measures

10. Spare parts and components

Visit our e-catalog for all the parts you need: https://www.unitecd.com/e-catalog/

11. Links

• DSTU 4535-2014: Requirements for the production and use of CNC machines
• EN 60204-1: Safety of electrical equipment for production facilities
• ISO 9283: Methods of measuring the accuracy of CNC machines
• ISO 10216-1: Requirements for the production and use of CNC machines
• UNITEC-D: Technical data sheets for components

1. Description of the problem and extent of damage

This guide is intended for debugging poor surface quality during CNC machining that can occur due to tool fatigue, vibration, spindle deflection, or incorrect cutting parameters. The problem can be critical, especially in the production of high-precision components in the aerospace, chemical and energy industries. The threat arises from deviations from established quality standards (DSTU, ISO) and possible wear and tear of equipment.

2. Safety precautions

Turn off the power and secure the equipment using lockout/tagout procedures before starting diagnostics.
Use personal protective equipment (insulating gloves, goggles, noise protection cabinets).
Check for stored energy resources in the system, especially in the spindle and hydraulic drives.

3. Necessary diagnostic tools

4. The first checklist

5. Systematic diagnostic scheme

1. Symptom: Surface unevenness
1. Check the cutting speed measurement.
1. If the speed is higher than 80% of the recommended, different from the set parameters.
2. If the speed is higher than 100% of the recommended speed, measure the vibration.
2. Measure spindle vibration (0-100000 mm/s).
1. If vibration > 50 mm/s, check spindle deflection.
2. If vibration < 50 mm/s, check tool fatigue.
2. Symptom: High noise level
1. Measure the noise level (dB).
1. If noise > 85 dB, check spindle deflection.
2. If the noise is < 85 dB, check for tool fatigue.
3. Symptom: High temperature regime
1. Measure the spindle temperature (°C).
1. If temperature > 60°C, check cooling.
2. If the temperature is < 60°C, check the spindle deflection.

6. Matrix of causes of defects

7. Analysis of the causes of defects

7.1. Spindle deflection

Spindle misalignment is caused by wear, improper installation, or a damaged connection. If the deviation is > 0.02 mm, vibration may occur, leading to unevenness of the surface. After detecting a deviation, it is necessary to adjust or replace the spindle.

7.2. Vibration

Vibration can be caused by tool fatigue, spindle deflection, or incorrect cutting parameters. If the vibration is > 50 mm/s, it can lead to tool fatigue, which reduces the quality of the machining. After detecting vibration, it is necessary to adjust or replace the tool.

7.3. Tool fatigue

Tool fatigue occurs due to incorrect cutting parameters, poor material quality or insufficient cooling. If fatigue > 0.1 mm, vibration may occur, leading to surface roughness. After detecting fatigue, it is necessary to adjust or replace the tool.

8. Step-by-step solution procedures

8.1. Spindle deflection

1. Measure the spindle parallelism with a parallelism measuring tool (0-50 mm).
2. If the deviation is > 0.02 mm, adjust or replace the spindle.
3. Check the spindle for wear with a micrometer (0-25 mm).
4. If wear > 0.1 mm, adjust or replace spindle.
5. Perform the spindle vibration test (0-100000 mm/s).
6. If vibration > 50 mm/s, adjust or replace spindle.

8.2. Vibration

1. Measure spindle vibration (0-100000 mm/s).
2. If vibration > 50 mm/s, check spindle deflection.
3. If the deviation is > 0.02 mm, adjust or replace the spindle.
4. Measure tool fatigue with a micrometer (0-25 mm).
5. If fatigue > 0.1 mm, adjust or replace tool.
6. Check the cutting parameters: cutting speed, cutting depth, feed.
7. If the speed is higher than 100% of the recommended speed, adjust.

8.3. Tool fatigue

1. Measure tool fatigue with a micrometer (0-25 mm).
2. If fatigue > 0.1 mm, adjust or replace tool.
3. Check the cutting parameters: cutting speed, cutting depth, feed.
4. If the speed is higher than 100% of the recommended speed, adjust.
5. Check for coolant.
6. If cooling is insufficient, adjust the cooling system.

9. Preventive measures

10. Spare parts and components

Go to the UNITEC-D catalog

11. Links

• DSTU 3026-99: Cutting tools
• ISO 10110: Requirements for cutting tools
• ISO 1846: Requirements for spindles
• ISO 5344: Requirements for cooling systems
• UNITEC-D technical data sheets

Note: All diagnostic procedures must be performed in compliance with safety rules and using appropriate equipment.

1. Description of the problem and scope

This guide is intended to solve the problem of poor surface quality that occurs during CNC machining. Poor surface quality can manifest itself in the form of increased roughness, changes in the shape of the product, deviation from design parameters or surface damage. This problem can occur on various types of equipment, including lathes, milling machines, grinding machines, and other CNC machines. The problem is classified as critical because it can lead to product rejection, rework costs, and failure to meet production requirements.

2. Preventive measures

Use of protective equipment: When working with metals that have a high temperature or grinding cutters, it is necessary to use work gloves, glasses, boots and special clothing. It is important to ensure the cleanliness of the workplace and the use of a special measuring tool.

Power Outage: Perform a lockout/tagout (LOTO) procedure before starting any measurements or restoring equipment to avoid unexpected power outages or restoration.

Recovery of protective elements: Before performing any operation on the equipment, check whether there is stored energy in the spindle, hydraulic actuator or other components. Use the appropriate tools to recover these items.

3. Necessary diagnostic tools

4. First review and checklist

5. Systematic diagnostic flow

1. Poor surface quality
   1. Check spindle vibration
   2. If the vibration is higher than 5 mm/s
      1. Check the spindle deviation
      2. If the deviation exceeds 0.02 mm
         1. Spindle restoration or replacement
   3. If the vibration is higher than 5 mm/s
      1. Check the condition of the tool
      2. If the tool is exhausted
         1. Replacement of the tool

6. Matrix of causes of defects

7. Analysis of the causes of defects

7.1. Exhaustion of the tool

Tool wear occurs due to improper use, high temperature conditions, insufficient cooling effect or selection of incorrect cutting parameters. Failure to correct this problem may result in incorrect processing, deviation from design parameters, or damage to the equipment.

Diagnosis: Measure the distance between the tool and the workpiece. If the distance exceeds 0.05 mm, this may be a sign of exhaustion.

Solution: Replace the tool or select a tool with higher fatigue resistance.

7.2. Spindle vibration

Spindle vibration can be caused by worn bearings, spindle deflection, or improper use of the electronic control system. Vibration can lead to a decrease in surface quality, an increase in roughness, or a deviation from the design parameters.

Diagnosis: Measure spindle vibration. If it exceeds 5 mm/s, it may be a sign of vibration imbalance.

Solution: Replace the spindle bearings or rebuild the spindle.

7.3. Spindle deflection

Spindle deflection occurs due to misuse, worn bearings, or lack of proper adjustment. Deviation can result in incorrect cuts, deviation from design parameters or equipment damage.

Diagnosis: Measure the spindle deviation. If the deviation exceeds 0.02 mm, this may be a sign of deviation.

Solution: Rebuild the spindle or replace it.

7.4. Incorrect cutting parameters

Incorrect cutting parameters can lead to tool fatigue, vibration, reduced surface quality or deviation from design parameters. It is important to use parameters that meet the requirements of the material, equipment and technology.

Diagnosis: Check the cutting parameters. If they do not meet the standards, this may be a sign of the wrong choice.

Solution: Choose cutting parameters that match the processing requirements.

8. Step-by-step troubleshooting procedures

8.1. Exhaustion of the tool

1. Measure the distance between the tool and the workpiece. If the distance exceeds 0.05 mm, the tool is exhausted.
2. Replace the tool or select a tool with higher fatigue resistance.
3. Check whether the cutting parameters meet the requirements.

8.2. Spindle vibration

1. Measure spindle vibration. If it exceeds 5 mm/s, the spindle vibrates.
2. Replace the spindle bearings or rebuild the spindle.
3. Check if the electronic control system meets the requirements.

8.3. Spindle deflection

1. Measure the spindle deflection. If the deviation exceeds 0.02 mm, the spindle is deviated.
2. Rebuild the spindle or replace it.
3. Check if the spindle tuning is correct.

8.4. Incorrect cutting parameters

1. Check the cutting parameters. If they do not meet the standards, this may be a sign of the wrong choice.
2. Select the cutting parameters that match the processing requirements.
3. Check if the electronic control system meets the requirements.

9. Prevention networks

10. Spare parts and components

For parts or more information visit: https://www.unitecd.com/e-catalog/

11. Links

• Standards: DSTU 3031:2006, EN 60204-1, ISO 10426-1
• Reference materials: Manufacturers' catalogs, technical passports, technical manuals
• Special Guides: Spindle Restoration Guide, Tool Selection Guide

1. Description of the problem and scope

This manual is dedicated to diagnosing and correcting CNC machine positioning errors caused by screw backlash, encoder shaft failure, thermal compensation failure, and wrong servo setting. The problem can occur in various types of production: automotive, aviation, food, chemical and power plants. According to DSTU 3015:2015, EN ISO 10216-1:2012 and CE standards, compliance with technical parameters is critical to ensure manufacturing accuracy. The conditions are considered critical if there are deviations from the set position by more than 0.01 mm or periodic gray failures occur.

2. Safety and Warnings

Important: Before starting diagnostics, perform a lockout/tagout (LOTO) procedure to disconnect the power supply and disconnect the drives. Use protective glasses, gloves and special clothing if there is a risk of electric shock or mechanical elements. Check for stored energy in the syrvo system, especially after a power outage. Accidental activation or deactivation may result in personal injury or equipment damage.

3. Necessary diagnostic tools

4. First review and checklist

5. Systematic diagnostic scheme

1. Symptom: Positioning deviation from the specified value.
   1. Diagnosis: Measure the deviation with a thermal camera and a micrometer.
      1. Result: Deviation < 0,01 мм – ймовірна несправність енкодерної фідачки.
         1. Diagnostic test: Measure the voltage and current on the encoder probe.
         2. Expected result: Deviation in voltage > 5% or in current > 10% - possible malfunction.
2. Symptom: Screw vibration during operation.
   1. Diagnosis: Use a vibration analyzer to measure vibration characteristics.
      1. Result: Vibration > 10 mm/s – likely screw or gear failure.
         1. Diagnostic test: Measure the propeller backlash.
         2. Expected result: Backlash > 0.02 mm - correction required.
3. Symptom: Unstable positioning during thermal changes.
   1. Diagnosis: Measure the temperature in the working area and check for thermal compensation.
      1. Result: The temperature changes by more than 5°C - probable lack of thermal compensation.
         1. Diagnostic test: Check gray settings for thermal compensation.
         2. Expected result: No setting - must be set.
4. Symptom: Unstable operation of the relay.
   1. Diagnosis: Measure the current and voltage in the relay circuit.
      1. Result: Deviation in current > 10% - probable wrong setting.
         1. Diagnostic test: Check gray settings in setup menu.
         2. Expected result: Incorrect parameters - needs to be adjusted.

6. Matrix for finding reasons

7. Analysis of root causes

7.1 Malfunction of the encoder file

An error in the encoder file can occur due to damaged cables, moisture or lack of power supply. According to EN ISO 10216-1:2012, the voltage and current measurement in the encoder box should be within 0-200 V and 0-200 mA. If the deviation exceeds 5% of the nominal values, this may be a sign of a lack of power supply or corrosion.

7.2 Reversal of the screw

Propeller backlash is caused by damage to the propeller, lack of lubrication, or improper adjustment. According to DSTU 3015:2015, the allowable backlash of the screw should not exceed 0.02 mm. If the backstroke exceeds this value, positioning errors may accumulate.

7.3 Errors in gray

Incorrect tuning of the servo can lead to failures in positioning. The EN ISO 10216-1:2012 standard requires that the deviation in the gray current does not exceed 10% of the nominal values. If the deviation exceeds this value, it may be due to incorrect settings or lack of compensation.

7.4 Lack of thermal compensation

Thermal compensation conforms to EN ISO 10216-1:2012 to ensure positioning stability with temperature changes. If the lack of thermal compensation results in temperature changes of more than 5°C, positioning errors may accumulate.

8. Correction sequence

8.1 Compensation for the malfunction of the encoder file

1. Power down the system and perform the LOTO procedure.
2. Measure the voltage and current on the encoder probe. If the deviation exceeds 5%, replace the encoder file.
3. Check the cables for corrosion or damage.
4. Turn on the power again and check the positioning.

8.2 Correcting the reverse movement of the screw

1. Use a micrometer to measure the screw backlash.
2. If backlash > 0.02 mm, adjust or replace screw.
3. Check the lubrication of the screw and gears.
4. Measure the return stroke again and check the positioning.

8.3 Gray settings

1. Measure the current in gray and compare with the nominal values.
2. If the deviation is > 10%, adjust gray in the setup menu.
3. Check the thermal compensation settings.
4. Measure the current again and check the positioning.

8.4 Installation of thermal compensation

1. Measure the temperature in the work area.
2. If the temperature changes by more than 5°C, set thermal compensation in the setup menu.
3. Check the thermal compensation settings.
4. Measure the temperature again and check the positioning.

9. Prevention

10. Spare parts and components

Go to the UNITEC-D catalog

11. Links

• DSTU 3015:2015 – Positioning accuracy and stability
• EN ISO 10216-1:2012 – Positioning accuracy of CNC machines
• CE standard - Technical requirements for electrical equipment
• UkrSEPRO – Electrical safety standards
• UNITEC-D Maintenance Guide – Additional maintenance recommendations