Grinding Machine Safety: Essential Tips for Operators

I. Safety guidelines for using universal cylindrical grinding machines

1. Prerequisite conditions for machine installation, commissioning, and use

(1) AC power supply

Stable voltage value should be 0.9 to 1.1 times the rated voltage; frequency should be 0.99 to 1.01 times the rated frequency.

(2) Ambient temperature

The normal working room temperature of the machine should be controlled between 10 and 30°C.

(3) Ambient humidity

The normal working relative humidity of the machine should be controlled between 30% and 90%.

(4) Pollution

The machine should not be used in severely polluted environments.

(5) Personnel

Personnel responsible for machine installation, commissioning, use, and maintenance should receive pre-job technical training and pass assessments, as well as carefully read the machine operation manual.

2. Preparation before starting and precautions for shutting down

(1) Preparation before starting

1) Wear appropriate work clothes and shoes for safe operation, and wear protective equipment when necessary.

2) Ensure that all protective covers and guards are installed and in place.

3) Confirm that there are no obstacles in the work area, and consider that the grinding wheel carriage advancement and worktable movement will not interfere with the workpiece, headstock, tailstock, etc.

4) Set all electrical switches to the zero position, place the worktable speed adjustment handle at the lowest speed, and position the operating handle to the left rear (close to the machine) position.

5) Ensure that the clamping devices used are in good condition, and check if the workpiece is securely and reliably clamped after installation.

(2) Shutting down

1) Shutting down during external cylindrical grinding. Move the operating handle to retract the grinding wheel carriage (coolant stops at this time), let the grinding wheel idle for more than 5 minutes to spin off water, then turn off the grinding wheel motor. After the grinding wheel has completely stopped rotating, turn off the oil pump motor, and finally turn off the machine power.

2) Shutting down during internal grinding. Retract the grinding wheel from the workpiece to a safe position, turn off the grinding wheel motor, turn off the oil pump motor, and turn off the machine power.

3. Prevention of accidental starting and misoperation

1) Operators should read and understand the machine operation manual, concentrate during work, and avoid operational errors.

2) Before starting the oil pump, place the operating handle in the left rear (close to the machine) position.

3) When grinding, loading/unloading, or measuring workpieces, operators should be careful to avoid their limbs or clothing from touching or catching buttons, handwheels, or handles to prevent accidental starting or misoperation.

4) Turn off the machine power when leaving the machine for an extended period.

4. Precautions during machine operation and workpiece grinding

1) The machine’s electrical cabinet has an interlock function for power-on when closed and power-off when opened. The door must be closed, and it is not allowed to open during the grinding process.

2) No one should stand directly in front of the grinding wheel when it is rotating.

3) When the worktable is moving back and forth longitudinally, there is a risk of finger pinching between the worktable stop and the reversing lever. Operators should avoid the contact area between the worktable stop and the reversing lever.

4) The relationship between the rotation direction of the cross-feed handwheel and the feed direction of the grinding wheel carriage: When the cross-feed handwheel rotates clockwise, the grinding wheel carriage advances (feeds in); when the cross-feed handwheel rotates counterclockwise, the grinding wheel carriage retracts (feeds out).

5) When the machine is running, avoid the motion areas of its movable parts, and set up protective barriers around the area when necessary.

6) When the grinding wheel is rotating, objects should not come into contact with it, and especially do not touch it with your hands.

7) When starting the grinding wheel, repeatedly and briefly alternate between pressing the “start” and “stop” buttons. At the beginning of each workday, let it idle for more than 1 minute, and only proceed with other operations after confirming there are no abnormalities.

8) When grinding the end face of a workpiece, the feed amount and speed should be within the range that the grinding wheel strength can withstand to prevent the grinding wheel from breaking.

9) When switching from external to internal grinding, the screw under the operating handle must be tightened after moving the grinding wheel carriage to the front end. Do not move the handle back and forth during subsequent operations.

10) Dry grinding should be avoided for workpieces made of general materials, and it is prohibited for workpieces made of aluminum, magnesium, and other flammable materials to prevent fire.

5. Precautions for loading and unloading workpieces

1) Confirm that the grinding wheel has retracted to a safe position and all machine components have stopped moving before loading or unloading workpieces.

2) For complex workpieces that are difficult to load/unload or those with large mass and unstable center of gravity, turn off the grinding wheel motor and wait for it to completely stop before loading or unloading.

3) When using center grinding, adjust the tailstock to a suitable position to firmly support the workpiece and lock it in place.

4) When using chuck grinding with self-centering chucks, single-action chucks, or other fixtures with wrenches, remove the wrench immediately after clamping the workpiece.

5) It is prohibited to clamp workpieces that exceed the mass range specified in the machine’s operation manual.

6. Precautions for measuring workpieces

(1) Measuring external diameters

Confirm that the grinding wheel has retracted to a safe position and all machine components have stopped moving before taking measurements.

(2) Measuring internal diameters

Confirm that the grinding wheel has completely stopped rotating and has retracted to a safe position (ensure there is enough space for measuring instruments and operations), and all moving parts of the machine have stopped before taking measurements.

7. Precautions for using grinding wheels

(1) Grinding wheel selection

Select grinding wheels according to the linear speed and wheel specifications specified in the machine’s operation manual. The linear speed of the grinding wheel is related to the diameter of the wheel and drive pulley; prevent errors in selection.

(2) Grinding wheel replacement

1) Check the grinding wheel for cracks and damage; it is strictly forbidden to use cracked or damaged wheels. A method to check is by tapping the wheel with a wooden hammer and judging it as qualified if it produces a clear, crisp sound.

2) When installing the grinding wheel, ensure that the gap between the wheel’s inner hole and the flange is not too large; otherwise, use paper shims.

3) Place 1-2mm thick paper or plastic gaskets between the grinding wheel and flange contact surfaces (two places). When tightening the screws, use a diagonal tightening method, gradually tightening in several steps with even force.

Note that the tightening torque for the screws should be: M8 screws: 19.3-22.5 N·m; M10 screws: 31.4-39.2 N·m; M12 screws: 49-58.8 N·m.

4) The grinding wheel must undergo static balancing before use. New wheels usually undergo two static balancing procedures, with a second balancing after dressing.

5) After replacing the grinding wheel, let it idle for more than 5 minutes during startup. During this time, no one should stand directly in front of the wheel.

(3) Grinding wheel stopping

In any situation, to stop the grinding wheel, first turn off the coolant pump and let the wheel idle for more than 5 minutes to spin off water before turning off the grinding wheel motor.

After turning off the grinding wheel motor, wait until the wheel has completely stopped before turning off the machine power to prevent damage to the wheel shaft due to lack of lubrication while rotating under inertia.

(4) Grinding wheel protection

Before starting the grinding wheel, close the wheel guard, secure the front movable shield, and adjust the gap between the movable shield and the wheel to less than 5mm. Readjust the movable shield when the wheel wears down to maintain a gap of less than 5mm. Only open the wheel guard and/or front movable shield after the wheel has stopped rotating.

(5) Grinding wheel dressing

Use a wheel dresser to dress the grinding wheel; manual dressing is not allowed. Stop the wheel rotation when installing or removing the wheel dresser. Wear protective goggles when dry dressing the wheel.

(6) Installing and removing grinding wheel flanges

Use special tools to install and remove grinding wheel flanges; do not strike the wheel.

8. Precautions for using coolant

• Only turn on the coolant to flush or pour over the grinding wheel when it is rotating.
• The coolant used in the machine should meet the requirements specified in the coolant standards, and its bacterial and toxic substance indicators should comply with relevant standards.
• It is prohibited to use flammable liquids as coolant.
• Replace coolant in a timely manner to prevent deteriorated coolant from being harmful to human health.
• Do not touch your mouth, eyes, or nose with hands that have come into contact with coolant during work. If contact occurs, rinse immediately with clean water.

9. Machine noise

The machine’s idle running noise pressure level at factory inspection should not exceed: 83dB(A) for standard precision machines; 75dB(A) for high-precision machines. The method for checking noise pressure levels should comply with GB/T 16769-2008. If the machine’s idle running noise pressure level exceeds the factory inspection index during use, promptly inspect and eliminate the issue.

10. Methods for responding to emergencies

1) When the machine experiences an abnormality, immediately press the “Emergency Stop” button to stop the machine’s operation, and place the operating handle in the left rear position (close to the machine). If in grinding state, manually retract the wheel head to a safe position.

2) In case of sudden power failure, immediately press the “Main Stop” button and place the operating handle in the left rear position (close to the machine). If in grinding state, manually retract the wheel head to a safe position.

11. Precautions during machine maintenance

1) The machine’s electrical cabinet has an interlock function that powers on when closed and powers off when opened. However, areas marked with a lightning bolt symbol and the low-voltage circuit breaker side remain energized when the door is open. If power is needed while the door is open during maintenance, professionals can manually override this, but please note that all areas without the lightning bolt symbol will be energized.

2) The machine should generally be in a stopped state during maintenance.

3) After cutting off the power using the circuit breaker in the electrical cabinet, high voltage remains on the primary terminal wires and connection posts of the circuit breaker. Please be careful not to touch them.

4) When disassembling components of the hydraulic system, even if the machine is stopped, wait until the pressure in the hydraulic system returns to zero before loosening any components to prevent hydraulic oil from spraying out.

5) Avoid letting oil, water, or cutting fluid enter the electrical cabinet, control box, or junction box.

6) All protective covers and safety devices must be restored to their original positions after maintenance and maintain their original effectiveness.

II. Safety Guidelines for Using CNC Grinding Machines

When using CNC grinding machines, in addition to following the above general safety knowledge for grinding machines, the following issues should also be noted.

1. Machine Start-up

After the machine has been securely installed, check all electrical connections, oil line connections, normal levels of lubricating oil and cutting fluid, normal operation of all speed change gears, and the secure fastening of all covers. The operator should thoroughly read the machine’s user manual and CNC programming manual before starting the machine.

1) Turn on the power switch of the electrical cabinet (machine is powered), the ventilation fans in the electrical cabinet and control panel start working, and the machine work light illuminates.

2) Press the NC start button on the control panel. The NC alarm indicator light flashes. Wait until the NC start indicator light is on before pressing the oil pump start button.

After the oil pump starts working, check the motor’s rotation direction and the normal working pressure of the hydraulic system. When the working pressure is abnormal, adjust the relief valve of the oil supply device to ensure the pressure is within the specified range.

After the cutting fluid pump starts working, check for normal operation of the cutting fluid pump.

The CNC system performs a self-check. When the status is normal, it provides the operation screen. Note that while the CNC system is working, always pay attention to whether there are alarm signals on the operation screen, and strictly follow the prompts for operation (refer to the operation manual’s alarm resolution guide).

3) Press the grinding wheel start button to start the external cylindrical grinding wheel motor (generally, do not start it at once, but continuously and quickly “start” and “stop” multiple times before it starts up). Check for normal rotation of the grinding wheel spindle.

Note: Before starting the grinding wheel motor for the first time after initial installation, the drive belt must be removed first. Run the motor without load to check the rotation direction. Only after confirming it’s normal should you install the drive belt and start the grinding wheel spindle. The grinding wheel spindle is strictly prohibited from reverse rotation. If there’s an abnormal sound during operation, stop the machine immediately.

4) Start the headstock motor. Select the “handwheel” mode, press the “water pump start/stop” button, and observe the normal rotation and stopping of the spindle dial.

2. Grinding Operation

• Grinding can only be performed after completing the machine start-up and pre-grinding preparation operations.
• Balance the grinding wheel before dressing it.
• Pay attention to adjusting the mechanical zero point to ensure the correctness of each axis coordinate.
• Adjust the tailstock spring pressure and the taper position of the work table according to the workpiece.
• Select “handwheel” or “MDI” mode for grinding operations (refer to the relevant CNC system programming manual and operation manual for programming and operation mode selection and operation steps).
• Grinding quality. It is related to the operator’s experience and factors such as grinding parameters (worktable speed, headstock speed, feed rate), grinding wheel material (structure, grain size, hardness), grinding wheel balance state, and cutting fluid.