Safety and Maintenance For CNC Machine
1 Safety Notes for CNC machine Operations
Safety is always a major concern in a metal-cutting Operation. CNC equipment is automated and very fast, and consequently it is a source of hazards , The hazards have to located and the personnel must be aware of them in order to prevent injuries and damage to the equipment. Main potential hazards include, rotating parts, such as the spindle, the tool in the spindle, chuck, part in the chuck, and the turret with the tools and rotating clamping devices, movable parts, such as the machining center table, lathe slides, tailstock center , and tool carousel, errors in the program such as improper use of the G00 code in conjunction with wrong coordinate value, which can generate an unexpected rapid motion, an error in setting or changing the offset value ,which can result in a collision of the tool with part or the machine, and a hazardous action of the machine caused by unqualified changes in a proven program, To minimize or avoid hazards, try the following preventive action: (1)
Keep all of the original covers on the machine as supplied by the machine tool builder (2) (3)
Wear safety glasses, gloves, and proper clothing and shoes. Do not attempt to run the machine before you are familiar with its control.
(4) Before running the program, make sure that the parts is clamped properly.
(5) When proving a program, follow these safety procedures.
? Run the program using the machine Lock function to check the program for errors in syntax and geometry.
? Slow down rapid motions using the RAPID OVERRIDE switch or dry run the program.
? Use a single-block execution to confirm each line in the program before executing it.
? When the tool is cutting, slow down the feed rate using the FEED OVERRIDE switch to prevent excessive cutting conditions. (6)
Do not handle chip by hand and do not use chip hooks to break long curled chips. Program different cutting conditions for better chip control. Stop the machine if you need to properly clean the chips. (7)
If there is any doubt that the insert will break under the programmed cutting conditions, choose a thicker insert or reduce feed or depth of cut. (8)
Keep tool overhang as short as possible, since it can be a source of vibration that can break the insert. (9)
When supporting a large part by the center, make sure that the
hole-center is large enough to adequately support and hold the part.
(10) Stop the machine when changing the tools, indexing inserts, or
removing chips.
(11) Replace dull or broken tools or inserts.
(12) Write a list of offsets for active tools, and clear (set to zero )
the offsets for tools removed from the machine.
(13) Do not make changes in the program if your supervisor has
prohibited your doing so.
(14) If you have any satety-related concerns, notify your instructor
or supervisor immediately.
2 Daily Maintenance
2.1 Checking the External View (1)
Machine oil (cutting oil, lubrication oil)has been scattered onto the servomoter, detector, or main unit of the NC , or is leaking. (2)
Damage is found on the cables of the movable blocks, or the cables are twisted. (3) (4) (5) (6)
Filter clogging.
A door of the control panel is not open. Ambient vibration.
The unit is located in a dusty location.
(7) Something that causes high frequency is played near the control unit.
2.2 Checking the inside of the control unit
Check that the following troubles have been eliminated:
(1) (2) (3) (4) (5) (6)
Cable connectors are loosened. Installing screws are loosened.
Attachment amplifier screws are loosened. The cooling fan operates abnormally. Cable damage.
Printed circuit boards have been inserted abnormally.
2.3 Fault diagnosis and Action
When a running fault occurs, examine the correct cause to take proper
action. To do this, execute the checks below: 2.3.1 Checking the Fault Occurrence Status Check the following: (1) (2) (3)
When did the fault occur?
During what operation did the fault occur? What fault?
(4) For automatic operation．．．Program number, sequence
number, and contents of Program? (5) For manual operation．．．Mode? a) Operating procedure?
b) Preceding and succeeding operations? c) Set/display unit’s screen? d) During I/O operation? e) f) g)
Machine system status? During tool change? Controlled axis hunting?
h) What fault occurred?
i) What does the alarm display of the set/display unit’s alarm
diagnosis screen indicate?
(6)
Display the alarm diagnosis screen to check the contents of alarm. (7)
What does the driving amplifier status display indicate?Check the contents of alarm based on the driving amplifier status display. (8) (9)
What does the machine sequence alarm indicate? Is the CRT screen normal?
(10) Is the control axis hunting? (11) Frequency of fault? (12) When did the fault occur?
(13) Frequency? (Did the fault occur during operation of another
machine?) If the ffrequency is too small, or the fault occurred during operation of another machine, the cause may be noises
of the supply voltage.
(14) For example, in this case, check that the supply voltage is
normal
(15) does momentary drop occur during operation of another
machine?
(16) and measures have been taken against noises. (17) In specific mode?
(18) When did the ceiling crane move? (19) Frequency for the same kind of work?
(20) Does the fault occur when the same operation is made?
(Repeatability check)
(21) Change the conditions (override, contents of program,
operation procedure, etc.) (22) Does the same fault occur?
of the supply voltage.
(14) For example, in this case, check that the supply voltage is
normal
(15) does momentary drop occur during operation of another
machine?
(16) and measures have been taken against noises. (17) In specific mode?
(18) When did the ceiling crane move? (19) Frequency for the same kind of work?
(20) Does the fault occur when the same operation is made?
(Repeatability check)
(21) Change the conditions (override, contents of program,
operation procedure, etc.) (22) Does the same fault occur?
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