Safety in machining center maintenance work

⚠What laws and standards require

• Industrial Safety and Health Regulations (Japan), Article 107 (Stopping operation during cleaning, etc.)

  When cleaning, lubricating, inspecting, repairing, or adjusting a machine (excluding the cutting part) involves danger, stop the machine and prevent others from operating it, for example by locking the starting device or attaching a sign. Work that can only be done while the machine is running is an exception, provided measures such as covering the hazardous areas are taken.

  Cleaning, lubricating, inspecting, and repairing a machining center are in principle done with the machine stopped. This is the basis for lockout/tagout. Hurco requires lockout/tagout for maintenance inside the machine, and Makino also includes lockout/tagout in its spindle lubricating oil refill procedure.^{[1][2][3][4][5]}

• Industrial Safety and Health Regulations (Japan), Article 108 (Stopping operation during cleaning of cutting parts, etc.)

  Clean, inspect, repair, replace, and adjust the cutting part with the machine stopped, and take measures such as a lock and sign on the starting device. When clearing chips or applying cutting fluid at a running cutting part, have workers use a tool such as a brush.

  Stop the machine to change tools, check cutting edges, and clear chips. There is a fatal case in which, on a vertical milling machine, a worker was clearing chips around the vise by hand while the spindle rotated and a work glove was caught by the cutter.^[1][6](1 source, for reference)

• Ordinance on Industrial Safety and Health (Japan), Articles 28 and 29 (Keeping safety devices effective)

  Employers must inspect and maintain safety devices, covers, and enclosures so that they work effectively. Workers must not remove them or disable them. When one is removed temporarily, get permission and restore it as soon as the work is finished.

  Never modify a machine to defeat the door interlock. On a machine with the interlock defeated, a worker trying to pick up a part under the table was caught between the table and the frame and died (case 101204). Haas includes door interlock operation in its daily inspection.^[1][7][8]

• Industrial Safety and Health Regulations (Japan), Article 111 (Prohibition of gloves)

  Do not allow gloves where a hand could be caught by a rotating cutting tool, as on drilling machines and chamfering machines

  The MHLW (Japan) cases say that on machine tools with rotating cutters, such as milling machines, gloves easily catch on the cutter and get drawn in, and they call for a ban on working with gloves and on working while the machine is running. The regulation's examples are drilling machines and chamfering machines. Makino writes to wear protective gloves when clearing chips with the machine stopped or handling parts with fins (think of it separately: rotating or stopped).^[1][6](1 source, for reference)

• Industrial Safety and Health Regulations (Japan), Article 110 (Wearing work caps, etc.)

  If hair or clothing could be caught in a powered machine, require work caps and work clothes

  Hurco requires safety glasses and safety shoes in the machining area.^[1][3]

• Ordinance on Industrial Safety and Health (Japan), Article 101 (covers for rotating shafts, etc.), Article 103 (power cut-off devices), Article 104 (signals for starting operation)

  Cover hazardous parts such as rotating shafts, gears, pulleys, and belts. Provide a power cut-off device for each machine. If starting operation is dangerous, set a signal and have it given.

  Always put the spindle head cover back after inspection. Being able to lock the main power is a precondition for lockout. After maintenance, call out to the people around before moving the machine (Makino's procedure has the same caution).^[1][9]

• Industrial Safety and Health Regulations (Japan), Article 105 (Flying workpieces, etc.) and Article 106 (Flying cutting chips, etc.)

  Where flying workpieces or chips could be dangerous, provide covers or enclosures; where that is difficult, have workers use protective equipment.

  Doors and windows protect against flying objects. Hurco says polycarbonate windows lose up to 10% of their impact resistance per year and recommends replacing them within 3 years.^[1][3]

• Cautions for maintenance inside the machine (Makino procedure manual)

  When working inside the machine with the power on, the worker removes and carries the door switch release key (the key is controlled by the person in charge), carries a manual pulse generator, and attaches warning tags to each operation panel and the main power so that others do not operate them. Call out to the people around before moving anything. For work with the power off, confirm that the unit has stopped completely.

  Even for work that enters the machine with the power on, such as greasing HSK collets, put the machine in a condition in which no one other than yourself can move it.^[9][5][10](1 source, for reference)

• Work inside the ATC magazine

  Haas warns that before replacing the sprockets of a 100-tool side-mount magazine, the carousel must be tied to the frame with a chain or belt so it cannot turn on its own (serious injury risk if it is not tied).

  The magazine can turn under its own weight even with the power off. Block it from turning before putting your hands in.^[11](1 source, for reference)

• Door interlock inspection

  Hurco explains that on its machines the doors and auxiliary doors are locked when the power is off or during automatic operation, and that opening a door disconnects the ATC's electrical circuit from the power supply. Haas checks door interlock operation daily.

  Check every day that automatic operation is not possible with a door open and that the door does not open during operation. Hurco writes that the safety circuit should be checked periodically, especially after parts are replaced.^{[3][8][7][12]}

• Guidelines for Comprehensive Safety Standards for Machinery (Japan; July 31, 2007, Notification Kihatsu No. 0731001)

  Maintenance and inspection should be possible, in this order of preference: (1) without removing guards or entering the hazardous area, (2) with the machine stopped if removal or entry is needed, (3) in a dedicated operating mode if it cannot be done with the machine stopped. All power sources must be able to be switched off, locked in the off state, and any residual energy released safely.

  On machining centers, in addition to locking the main power, check residual energy such as air, hydraulic, and counterbalance pressure, the weight of the spindle head, and magazine rotation.^[13][14](1 source, for reference)

• Lockout/tagout procedure

  MHLW (Japan) material shows, with diagrams, a method in which each person working applies their own lock. OSHA requires that locks and tags be removed only by the person who applied them, and that the people around be notified before restarting.

  When several people do maintenance, each person applies their own lock^[4][2]

• Accident case: electric shock during machine repair

  A person left a machine under repair with the power on and hung only an "Under repair" tag. Another person assumed it was not energized, touched it, and received an electric shock (lathe case).

  A tag alone is not enough. When you leave, turn the power off and lock it out.^[15](1 source, for reference)

• ISO 16090-1:2022 (Machine tools safety — Machining centres, Milling machines, Transfer machines — Part 1: Safety requirements)

  Covers everything from manual milling machines to CNC milling machines, machining centers, and transfer machines, including tool magazines, tool changers, workpiece transport, power clamping, chip conveyors, and power doors, and sets out the hazards and safety requirements, including situations such as cleaning, maintenance, and troubleshooting.

  A framework for checking, after maintenance, that safety functions such as interlocks and guards are back to normal. The 2017 edition was revised in 2022 (per the ISO bibliographic record). Safety JIS standards exist for lathes (JIS B 6031) and drilling machines (JIS B 6034), but none was found for machining centers or milling machines in a JSA search. Hurco refers to ANSI B11.23, EN 12417, and ISO/DIS 16090-1.^{[12][16][17][18][3]}

• ISO 14118:2017 (Safety of machinery – Prevention of unexpected start-up)

  Specifies design measures to prevent unexpected start-up caused by electric, hydraulic, or pneumatic power, or by energy stored by gravity or springs.

  The international standard on the design side of lockout/tagout^[19](1 source, for reference)

• Share of occupational accidents caused by machinery (MHLW pamphlet)

  About one quarter of casualties involving 4 or more days of lost work, and about one third of fatal accidents, are caused by machinery, and 80% of the causes are insufficient machine safety measures (Japan, 2014 statistics).

  Both machine safety measures and safe use of machines are important^[20](1 source, for reference)

The legal provisions are summarized in Kezuriba's own words. Check the exact wording against the original text in e-Gov Law Search.