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Safety precautions for injection molding machines

August 29, 2022

Latest company news about Safety precautions for injection molding machines

Safety precautions for injection molding machines

1.1 General safety rules

Maintenance, repair and maintenance of the machine must be carried out by an adequately qualified specialist with extensive experience in the field of injection moulding machines. They should be familiar with industrial longevity and safety standards, and should be familiar with the construction and function of required machine safety equipment.


The safety device installed on the machine is designed to ensure the safety of the operator's life and to ensure that the product is not damaged.

The machine must ensure that all safety equipment is in normal working condition before it can be operated.

Do not remove any safety device arbitrarily.

The security facility also includes the program in the software, and no modification of the program is allowed.

If any accident or error occurs in the safety device, the machine must be shut down immediately;

Emergency stop key The main power switch turns off the cooling water supply after about 20 minutes, and the person in charge must be notified immediately

The fault must be eliminated before restarting the machine

1.1.1 Machine Safety Labels

Please pay attention to all safety signs during production, use Chinese and English, and be sure to follow the "safety first" principle.

1.1.2 Precautions during maintenance


All maintenance work must be carried out when the main power switch of the injection molding machine is set to "0", and if necessary, lock it with a padlock.

It is the employer's responsibility to make the operator aware of the construction and function of the safety facility and to take personal health and safety seriously.


Any work that would damage the safety features of the machine should be stopped.

Employers must ensure that operators are experienced and qualified operators.

Safeguards should not be detached from the machine or inoperative under any circumstances. If a safety device does need to be removed to service the machine, safety must be ensured. After the repair work is finished, put back the safety device as it is and check the effect.

Any modification of safety equipment without permission is not allowed!

1.1.3 Exclusion of toxic fumes

Some plastics emit toxic fumes when overheated, mainly polytetrafluoroethylene (PTEE), polyoxymethylene (POM) and polyvinyl chloride (PVC).

If these toxic fumes cannot be eliminated by the emergency mechanical device, it is recommended to install an exhaust fan to eliminate harmful fumes, and the exhaust fan switch is required to be locked with the power switch of the injection molding machine.


If the fume extraction device is installed directly on the machine, we recommend installing it on the fixed formwork.

1.1.4 Prevention of plastic decomposition

Some plastics will decompose and explode when heated for a long time. The plastics are mainly polyoxymethylene (POM) and polyvinyl chloride (PVC).

When processing this type of plastic, pay attention to the nozzle should be withdrawn from the mold when the injection pressure increases, so that the gas generated by decomposition can escape from the nozzle.

Accidents are prevented by the following measures:

The process and parameters are set strictly according to the material properties of the plastic, especially the heating temperature and residence time in the barrel. When processing heat-sensitive plastics, the residence time of the plastic in the barrel should be shortened, and when the production is interrupted or the material is denatured, it is cleaned with polyethylene (PE) (the barrel of the heat-sensitive plastic has been used), and then the heating is stopped.

1.1.5 Prevent over-pre-molding from causing accidents

Generally, it is more appropriate to set the pre-plastic amount to exceed about 15% of the weight of the product. If the pre-plastic amount is too large, there will still be too much high-temperature and high-pressure melt in the barrel and hot runner after injection molding; After the molding is completed, the molten material in the barrel still has a high residual pressure. When manually cleaning the mold cavity or repairing the mold, this energy may be released suddenly, which may cause the high temperature material to hurt the human body. The nozzle leaves the die, and the oil pump motor is stopped after the die is opened.

1.2 Safety equipment

1.2.1 General equipment

Safety features include guards and insurance

The protective door prevents anyone or anything from entering the hazardous area and protects people from being injured by molten plastic splashing out. When the protective door is opened, the safety mechanism will interrupt any dangerous mechanical movement. The dimensions of the moving protective door in the die area and the hydraulic ejector mechanism are designed to have a large enough safety edge. For larger molds, the size of the protective door at this time is correspondingly increased.
1.2.3 Mould area moving protective door

There are three safety braking mechanisms for the moving door insurance in the cavity area, one is a mechanical safety braking device, the second is a hydraulic safety braking device (except PD60-PD148), and the third is an electrical safety braking device.

When the protective door is opened, the three safety mechanisms automatically work to prevent the clamping device, the ejection system and the injection device from moving. When the electrical safety of the injection molding machine is active, the main motor does not work.

The mechanical safety device makes the mechanical safety stop fall down by moving the mechanical safety collision block, preventing the movement of the mechanical safety lever and preventing the clamping action.

Through the action of the safety travel switch, the electrical fuse stops the clamping action in the electrical system.

Error message:

If the protective door is not closed and the machine is started, the information displayed on the screen during misoperation: the message "safety door is not closed" will be displayed on the display of the operation panel.

Error message elimination:

Close the protective safety door. If the message on the display is still not canceled, continue to check the limit switch, adjust or repair the limit switch; after the error is eliminated, the error message is automatically canceled. 1.2.4 Nozzle guard

In order to prevent the hot plastic spray from hurting people, a metal nozzle protective cover is set at the working position of the nozzle, a movable door cover with an observation window is installed on the protective cover, and a safety travel switch is installed on the movable door cover.

When the nozzle guard is opened, "injection seat forward", "injection" and "pre-molding" all stop (some series models may be slightly different due to the configuration relationship).

Semi-automatic and fully automatic operation is canceled.

Error message:

If the start action is made without closing the nozzle guard, "Nozzle guard not closed" will appear on the display. After closing the protective cover, the error message disappears and work can be resumed.

1.2.5 Hopper feeding

The auxiliary feeding equipment is provided by the user and must be fixed with the feeding port. Auxiliary facilities such as steps, platforms or feeders should be used to feed the hopper.

Attention! It is forbidden to step on the injection unit for maintenance or on the machine to add material to the hopper. This operation is prone to injury.

1.2.6 Fixing the protective door

The fixed protective door is tightened with screws, can only be opened with suitable tools, and can only be removed for maintenance.

ATTENTION! It is not permitted to operate the machine with the fixed protective door open.

The fixed protective doors are installed on the operator and anti-operator sides in the clamping area, in front of and on the side of the glue injection device. Other fixed protective doors to prevent the mold clamping device from entering the side of the second plate: to prevent possible contact with the barrel heat insulation device.

Attention! PPE protective gloves and safety glasses must be worn when working in the plasticizing and injection area; it is not allowed to adjust the safety valve of the oil pump system under any circumstances.

1.2.7 Other hazards arising from the opening of the nozzle guard

If the hopper is removed or the addition is interrupted, increased barrel heat means a fire hazard at the filling port.

Fires can also occur in the nozzle area because of the high nozzle temperature and the nozzle heating ring, and the molten material can be ejected at the same time.

1.3 Hydraulic safety device

In addition to the hydraulic protection safety valve of the protective door, the hydraulic safety system is mainly realized by the system safety valve. The manufacturer has set the maximum allowable value and closed it. If the pressure value exceeds the set specified value, the system safety valve will open.

Relief valve hydraulic system pressure and protect the operator, prevent the hose and steel pipe connection from damage caused by excessive pressure. At the same time, it is protected from damage caused by hydraulic system errors. The safety valve protects the oil pump in the hydraulic drive from overload.

Attention! It is not allowed to adjust the safety valve of the oil pump system under any circumstances.

1.4 Electrical safety devices

Electrical safety devices include a basic ground wire and an emergency stop button.

All electrical parts of the machine have grounding wires, especially the electric heating part, the heating ring must be checked.

The emergency brake buttons are respectively arranged on the operation panel and the protective plate of the head plate.

If this button is pressed, all the movements of the machine are stopped immediately, including the oil pump motor. All operating devices connected to the standard interface will also be switched off.

Required for safety Once the emergency stop button is pressed, the machine will stop immediately.
Injection molding machine
Injection molding machine

Rotate the outer ring of the button by a certain angle to reset the button. Then the operation restarts and the error disappears.

The circuit breaker has a voltage loss protection function.

1.5 Check safety equipment

Attention! When the customer tests the machine after the machine is installed, he should first check whether the safety facilities are effective. If the safety device is faulty, stop the machine immediately.

When the machine is back in working order, the cause of the error must be found and eliminated.

We recommend the following inspections of security facilities:

When testing the machine, the operator and the installer must check it together. Carefully check the moving parts of the machine to see if there are foreign objects that hinder the operation of the machine. After confirming, close the mobile protective door. Use the manual mold opening button to move the template to the left to the mold opening position. Open the moving protective door and visually check whether the mechanical safety stopper has fallen, which can prevent the clamping action. Press the mold closing button, there should be no mold closing action, if any action occurs, check and adjust the hydraulic safety switch. Press the demoulding button, plasticizing button, injection button, and ground button. If any action occurs, check and readjust the electrical safety switch. When closing the moving protective door, the safety bump will lift the mechanical safety block, press down the electrical safety switch, and at the same time make the hydraulic safety switch pop up. At this time, all button controls on the operation panel are valid. Inspection safety devices include the following items:

The rigidity of the actuator; whether the safety safety mechanism is fastened to the machine; whether all wires are properly connected to the electrical safety switch; whether each individual safety device and limit switch function properly. Attention! When the protective door is open during the safety inspection, the dangerous part of the machine is exposed. Make sure that the body and other objects are kept away from this area.

Check the travel switch of the nozzle protective cover, and wear protective glasses to avoid the danger of molten material splashing.

If a fault in the safety device is found, the machine must be shut down immediately! The fault and cause must be eliminated before restarting the machine.

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