What is the problem that the injection molding manipulator does not pick up the parts in time during the production and processing?

The untimely picking of parts by injection molding manipulator may be caused by many problems, such as program setting, mechanical hardware, sensor detection, cooperation of peripheral equipment, etc., which need to be investigated step by step. The following are common reasons and solutions:

First, the program setting problem

1. The cycle time setting is unreasonable.

Reason: The operating speed and acceleration of the manipulator are set too low, or the time parameters of each action (such as descending, picking up, ascending and releasing) are too long, which leads to the cycle period exceeding the mold opening period of the injection molding machine.

Solve:

Optimize speed/acceleration parameters (within the allowable range of equipment to avoid impact);

Shorten unnecessary action time (such as reducing waiting delay and merging coherent actions).

2. Coordinate position deviation

Reason: The coordinate (X/Y/Z axis) of the manipulator is not aligned with the center of the mold cavity, which leads to the need to adjust the path extra and prolong the time.

Solve:

Teach the pick-up point manually, and calibrate the coordinates with the needle aligning tool or mold locating pin;

Turn on the "automatic centering" function (if any) to ensure the accurate alignment of the sucker/fixture.

3. The action sequence is wrong

Reason: The action logic of the manipulator and the injection molding machine in the program conflicts (such as starting to take parts before the mold is completely opened).

Solve:

Check the I/O signal docking: ensure that the manipulator receives the signal of "mold opening is complete" of the injection molding machine before triggering the part taking action;

Add the conditional judgment of "waiting for mold opening in place" (such as delay of 0.5~1 second).

Second, the mechanical hardware failure

1. Abnormal driving system

Servo motor/cylinder problem:

Cause: Motor overload, encoder failure, insufficient air pressure or air leakage in the cylinder, resulting in shaft motion jamming and speed reduction.

Solve:

Check the alarm code of motor driver (such as overload alarm "AL.06"), and check whether the load is too large (such as heavy fixture);

Measure the air pressure of the cylinder (the standard air pressure is usually 0.4~0.6MPa) and replace the damaged air pipe or sealing ring.

Wear of transmission parts:

Cause: The wear of screw, guide rail and gear rack leads to the increase of transmission resistance and the slow running speed.

Solve:

Clean and lubricate the guide rail and lead screw (using lithium-based grease);

Check the transmission clearance (if the back clearance of the screw rod is more than ＞0.05mm, it needs to be replaced).

2. Fixture/suction cup failure

Reason:

The sucker is damaged and the vacuum degree is insufficient (such as vacuum pump failure), which leads to multiple attempts to take the parts;

Wear of clamping jaws, slow opening and closing speed, or insufficient clamping force cause the workpiece to fall off and need to be grabbed again.

Solve:

Replace the sucker and check the vacuum pressure (the standard vacuum degree is usually-60 ~-80 kPa);

Adjust the position of gripper travel switch, or replace pneumatic fingers (such as SMC pneumatic gripper) to improve the response speed.

Third, the sensor detects abnormality

1. The position sensor fails.

Reason:

The position of photoelectric switch and proximity switch is offset or blocked by oil pollution, which causes the manipulator to misjudge the mold opening state or the signal of taking parts;

The magnetic switch did not detect that the cylinder piston was in place, and stopped waiting for the signal.

Solve:

Clean the sensor surface and recalibrate the installation position (ensure that the detection distance is within the effective range, such as the detection distance of photoelectric switch is 5 ~ 10 cm);

Check whether the indicator light of cylinder magnetic switch is normal, and adjust the switch position to the end of piston stroke.

2. Failure of workpiece detection

Reason:

Workpiece detection sensors (such as optical fiber sensors) are not installed, or the sensors can't identify transparent/reflective workpieces, which causes the manipulator to wait for overtime;

Detection signal delay (such as sensor response time > ＞50ms), missed the best pick-up opportunity.

Solve:

Select the appropriate sensor according to the characteristics of the workpiece (such as laser sensor for transparent parts and diffuse reflection optical fiber for reflective parts);

Shorten the transmission path of detection signal, or set the threshold of "overtime forced pickup" in the program (such as automatically executing the next step after waiting for 2 seconds).

Four, peripheral equipment with the problem

1. Abnormal mold opening of injection molding machine

Reason:

The hydraulic system of injection molding machine is faulty and the mold is stuck, resulting in slow mold opening speed or incomplete opening;

Delayed action of thimble (e.g. thimble does not eject the workpiece in place), which affects the grasping of manipulator.

Solve:

Check the mold opening pressure and speed parameters of injection molding machine (such as whether the set value of mold opening pressure is lower than the actual demand);

Adjust the ejector stroke of the mold to ensure that the workpiece is completely separated from the cavity (the ejector stroke should be 5~10mm longer than the height of the workpiece).

2. Conveyor belt/receiving platform failure

Reason:

The speed of the conveyor belt does not match the speed of the manipulator, which causes the manipulator to wait for the conveyor belt to be in place;

The position of the pick-up table is offset, and the manipulator needs to adjust the placement path.

Solve:

Synchronize the manipulator's release signal with the start-stop signal of the conveyor belt (for example, the conveyor belt starts 0.5 seconds in advance when releasing the parts);

Calibrate the coordinates of the docking station to ensure that there is no interference in the placement path.

V. Other potential factors

1. Workpiece sticking/deformation

Reason:

Injection molding process problems (such as insufficient pressure holding and short cooling time) cause the workpiece to stick to the mold and the manipulator cannot take it out smoothly;

The workpiece is deformed and stuck in the mold, which requires extra force to grab it.

Solve:

Adjust injection parameters (such as increasing holding pressure and prolonging cooling time);

Add release agent to the mold, or optimize the gate design to reduce mold sticking.

2. Control system compatibility

Reason:

The communication protocol between manipulator and injection molding machine does not match (such as different PLC models), and the signal transmission is delayed;

The system version is too low, and there are program loopholes.

Solve:

Replace compatible communication modules (such as Modbus-RTU to Profinet);

Upgrade the firmware of the manipulator control system to the latest version.

Suggestions on troubleshooting process

Step 1: Observe the alarm log of the manipulator and give priority to hardware faults (such as motor overload and abnormal sensor).

Step 2: Compare the cycle time of the manipulator with the mold opening cycle of the injection molding machine to confirm whether the delay is caused by the setting of program parameters.

Step 3: Manually test the motion speed of each axis and the response of the fixture, and troubleshoot the mechanical jamming or wear problem.

Step 4: Check the mold opening state of the injection molding machine and the demoulding of the workpiece to eliminate the influence of peripheral equipment.

Step 5: Detect the signal transmission delay through the oscilloscope and optimize the I/O communication logic.

Through systematic investigation, the root cause of untimely pickup can be quickly located, and most problems can be solved by adjusting parameters or maintaining hardware. If complicated system compatibility or mold design problems are involved, it is recommended to contact the equipment manufacturer or mold engineer for collaborative processing.