CNC Milling Machine Internship Safety Operating Procedures

CNC milling machine internship safety operating procedures

When entering the CNC workshop, the first reaction of many students is excitement, and they can't wait to start the machine immediately and start operating. However, every year, there are accidents in which students' fingers are amputated due to operation problems, and workpieces fly out and penetrate their chests. Safety is not a slogan posted on the wall, but a painful lesson learned with blood.

Go through the safety exam before entering the workshop

Many schools stipulate that before students enter the CNC milling machine workshop, they must first pass the two theoretical assessments of safe and civilized production and machine tool operating procedures. In 2025, statistics from a vocational and technical college in Guangzhou showed that if students have not received system security training, the likelihood of making operational errors during the internship stage is seven times higher than that of students who have received training. This exam covers the location of the emergency stop button, the operation process of tool replacement, and the range of machining parameter settings. The full score of the exam is 100 points, and a score of 90 points is required to be considered passed.

There is a yellow safety line painted on the workshop floor, and students are not allowed to cross it without permission. Before each computer is turned on, the instructor will randomly check 5 safety knowledge points. Students who answer incorrect questions will not be able to operate the computer that day. Among the interns accepted by a manufacturing company in Dongguan in 2024, half of them failed the first exam and were only allowed to enter the workshop after taking a make-up exam.

Not even one piece of labor protection equipment will be enough

The four standard items for CNC 铣削 machine operation are a safety helmet, goggles, anti-smash shoes, and work clothes. The safety helmet must be fastened with a chin strap, and the safety goggles must be able to prevent side splashes. In March 2026, in a school in Shenzhen, a student did not wear goggles because he thought it was troublesome. Chips flew into his left eye, causing corneal damage.

The condition of the machine tool must be checked before operation. After the protective door is opened, first check whether there are residual chips around the spindle, and use a brush to clean it to a clean state. Then check whether the clamp is loose, and pull the tool handle to confirm whether it is locked. After the workpiece is clamped, it needs to be tightened again with the help of a wrench, in order to prevent it from flying out during the processing. If you find abnormal oil leakage or abnormal noise, you must report it to the teacher immediately, and you are not allowed to repair it yourself.

Specify the camera position, do not move around, and remember the boot sequence.

Each student can only operate the machine tool assigned by the teacher, and is not allowed to skip work. In 2025, an accident occurred at a vocational school in Hangzhou. Student A did not turn off the machine when leaving. Student B pressed the start button out of curiosity. The tool directly hit the workpiece, causing it to break. The teacher will fix the machine position according to the student number and post the operator's name on the front of each machine tool.

The sequence of turning on the machine is as follows: first close the main electronic control blade, then turn on the CNC system power supply, and finally press the servo start button. When shutting down the machine, the sequence is reversed. First, turn off the servo, then turn off the system, and finally pull on the main switch to cut off the power supply. It is absolutely forbidden to directly pull the main switch to forcefully cut off the power supply, because this will cause damage to the control system. If you encounter other people asking questions while operating, you must first stop the program temporarily before you can answer it, and don't be distracted by doing other things while processing.

Only after passing the graphics simulation can you start the knife

Before performing milling operations, it is necessary to run the graphics simulation function in the CNC system to observe whether there is overcutting or collision in the tool trajectory. During the simulation process, the color of the workpiece needs to be set to a translucent state, and the tool path needs to be displayed in red, focusing on checking the entry and exit points and cutting depth. In 2024, an intern from a company in Suzhou discovered that the tool path would hit the pressure plate during the simulation. Due to timely corrections, the accident was avoided.

When the simulation is confirmed to be error-free, you need to raise your hand to inform the teacher to come to the site for re-checking. The teacher will use a special inspection program to run it again, and at the same time check whether the extended length of the tool is reasonable and whether the clamping of the workpiece is stable and reliable. Only after obtaining verbal consent from the teacher can the button to start the cycle be pressed. If you do not go through this step and carry out processing operations without authorization, you will be directly disqualified from the internship for that day.

Don’t touch the emergency stop button when running

When the machine tool is in normal processing status, it is not allowed to press the emergency stop button or reset button casually. The emergency stop button appears red. Once pressed, the spindle and feed will be locked immediately. However, a sudden stop may cause the tool to break and may also cause the workpiece to be scrapped. The reset button will clear the current program segment from the CNC milling safety regulations . When restarting, coordinate misalignment is prone to occur. Only in the three situations of tool chipping, loose workpiece, smoke and fire, can you press the emergency stop.

During the processing process, it is absolutely forbidden to touch the workpiece or tool with your hands, regardless of whether the machine seems to have stopped. After the spindle of the CNC milling machine stops, the tool may still be rotating by inertia. If you touch it with your hands, you will be cut. What's even more dangerous is that the program may be in a suspended state and suddenly start when you reach in, and the consequences are simply unimaginable. To observe the processing situation, you need to pass through the plexiglass window of the protective door.

Shut down before leaving if you have something to do

During the machining process, you are not allowed to leave the machine tool without any reason. If you need to go to the toilet or pick up tools, you must first press the feed hold button to put the program in a paused state. After the spindle has completely stopped rotating, you can press the emergency stop button to lock the machine tool. Before leaving, a sign with the words "Processing suspended, please do not operate" needs to be hung on the operation panel. In 2025, a student in a school in Chengdu ran to answer the phone while processing a large workpiece. When he returned, he was shocked to find that the tool had been burned.

If you encounter an emergency, such as workpieces flying out, coolant gushing out, smoke and fire, press the red emergency stop button immediately. Don't think about catching the flying workpieces yourself, and don't put out the source of the fire. First retreat to a safe area at the door of the workshop, and then call the teacher loudly. The teacher will cut off the main power supply and use a carbon dioxide fire extinguisher. After the fault is eliminated, the teacher will calibrate the coordinate system again, and students are not allowed to resume processing on their own.

Machine tool parameters must not be changed

Students are not allowed to modify or delete confidential parameters and system files in the CNC system, including tool compensation values, feed speed override upper limit, soft limit range, servo drive parameters, etc. In early 2026, in a school in Shanghai, a student arbitrarily adjusted the upper limit of the feed rate from 100% to 150% in order to speed up the processing speed. Eventually, the tool broke due to overload and the spindle bearing was also damaged.

System files must not be touched at will, such as ladder diagrams, PLC programs, and macro libraries. Once deleted or incorrectly modified, the machine tool is likely to be completely paralyzed, and the cost of repair will be as high as tens of thousands of dollars. The teacher will set a password in the system to prevent students from entering the parameter setting interface. If there is a need to modify the tool compensation, the modification must be completed under the supervision of the teacher, and after the modification is completed, it must be recorded and written into the machine tool logbook.

Clean and maintain before get off work

After completing the processing, be sure to clean the machine tool. Use a brush and vacuum cleaner to remove the chips on the workbench, and then use a rag to wipe away the oil on the guide rails and protective cover. When cleaning, be aware that the chips are very sharp. Wear thick rubber gloves instead of wire gloves when cleaning. Then add lubricating oil to the guide rail and screw, and operate according to the oil amount and cycle specified in the machine tool manual. In 2025, an intern in a certain factory failed to clean the iron filings on the guide rails, causing the guide rails to be strained when the machine was turned on the next day. The final repair cost 30,000 yuan.

Return tools and gauges to their designated locations. After using precision measuring tools such as vernier calipers and micrometers, they must be wiped clean, coated with anti-rust oil, and then placed back in the wooden box. Tools, including wrenches, screwdrivers, etc., need to be hung back on the tool board and not left on the workbench or machine tool. Once a tool is found to be damaged or lost, it must be reported to the teacher immediately. Failure to report it will be considered intentional damage.

Compensation for damaged equipment according to the price is not a threat

In the field of engineering, once measuring tools and equipment are damaged, they need to be compensated according to their actual value. This is a mandatory regulation formulated by the workshop. In 2025, there was a school in Guangzhou. A student of the school accidentally bent the edge finder during operation and was compensated 680 yuan. Another student broke the claw of the spindle tool handle, and the cost of replacing the claw was as high as 4,200 yuan. The school will ask every student to sign a safety commitment when they enroll to clarify the compensation standards.

Compensation is not the purpose, but to make students have awe of the equipment. Spend three minutes to check the tools and workpieces before each operation. Only by concentrating on the process of processing and not playing with mobile phones can most forms of damage be avoided. Assuming that an accident does occur and proactively acknowledges it and analyzes the relevant reasons, the school may reduce part of the compensation based on the actual situation. However, if the concealment is not reported and is verified, not only will full compensation be made, but also a demerit will be recorded.

Which school or factory are you in? Have you ever encountered students who did not cooperate during CNC milling machine safety training? You are welcome to share your own experiences in the comment area. If the number of likes exceeds 1,000, I will compile a list of common violations in the workshop for everyone.