Injection molding optimization thanks to adapted mold movement

Cycle times of 3 to 4 seconds are typical in the injection molding production of packaging parts. The pressure to reduce production times continues to increase. ENGEL has developed an intelligent assistance system that automatically optimizes the acceleration phases of movement sequences in injection molding. The result is faster movements.

The ENGEL viper linear robots made the start. What is new is that iQ motion control is also available for mold movement in the injection molding machine. The packaging industry in particular benefits from this.

Opening and closing the injection mold accounts for a large part of the production time in high-speed applications. This becomes clear in the production of thin-walled containers. They are produced in a 4-cavity mold on an ENGEL e-speed 280 injection molding machine.

The facts:

• Total cycle time: 3.15 seconds

• Injection time: 0.08 seconds

• Cooling time: 0.8 seconds

The demolding of the parts takes 2.27 seconds. Of this, only 1.0 seconds can be attributed to the removal by the robot. The mold movement therefore takes the remaining 1.27 seconds, which corresponds to 40% of the production time.

Closing the mold after removing the thin-walled containers takes 0.77 seconds, including the build-up of clamping force. To shorten the injection molding cycle, the injection process already starts at 70% of the set clamping force. An even earlier start is not possible, as the material could otherwise flow into the parting line of the mold. But with an injection time of only 0.08 seconds, the potential is manageable anyway. No further time can be saved by parallel movements. To reduce the cycle time in injection molding, the only option is to optimize the mold movement.

0.77 seconds for the closing movement is already impressive for a stroke of 285 mm and including the closing force build-up. The drive constantly alternates between acceleration and deceleration. The movement time can be optimized if you know when to accelerate or decelerate and how much.
This is precisely where iQ motion control comes in. The assistance system evaluates the relevant parameters such as clamping force, stroke and mold weight for the respective application. It also calculates the optimal accelerations. The drive power is used optimally, which shortens the mold movement by an average of 10%.

The use of iQ motion control results in the following advantages and optimization in injection molding:

• iQ motion control takes over the fine-tuning of the mold movement - for each individual application.

• The user benefits from shorter dry cycle times of the injection molding machine.

• The operation of the machine is simplified by the independent optimization.

In the production of the thin-walled containers, the cycle time was reduced from 3.15 to 3.0 seconds. In relation to the dry cycle time of the injection molding machine, this results in a reduction of 12% - 1.12 instead of 1.27 seconds.

The graphic shows, based on the motor movement and the drive torque, at which points in the injection molding cycle time is saved. By defining maximum values, iQ motion control ensures that there is no increased load on the mechanics and drive technology.

The comparison with the reference curve without iQ motion control makes it clear that the greatest potential for injection molding optimization lies in the first 0.3 to 0.5 seconds of the closing movement. The greater drive torque leads to higher speeds at an earlier stage, which saves time. In addition, the torque is built up and released much more evenly. This also saves time.