If the injection molding machine and robot coordinate their movement sequences, this shortens the cycle time in many applications. iQ motion control from ENGEL now allows reliable early start combined with fully automatically optimized motion planning. The assistance system has been part of the standard kit of all new ENGEL viper linear robots since October 2021.

Fluid movements arise when movements harmoniously intermesh. Only then are they economic and efficient. Every living organism masters this labor- and time-efficient interplay of different limbs — while, in this respect, a robot or automated machines and processes are only as good as the human being is at programming them via the system controls.

In an injection molding cell, there are many different movable “limbs.” Some of them critically also determine the cycle time of the injection molding process. They include the removal robot’s entry and exit movements, as well as the mold opening and closing time. It is illuminating that much cycle time is wasted when a removal robot only starts moving when the injection mold is completely opened.

To achieve fluid movements in the production cell, ENGEL always focuses on the entire injection molding cell and the interplay of the movements of injection molding machine and robot. If ENGEL supplies the entire production cell, from the injection molding machine, via the automation and other ancillaries, as far as the process engineering from a single source, all the components of the cell access the same control platform and the same database, and thereby have the best prerequisites for a short overall cycle time.

Since an injection molding cell does not have command of these intermeshing parallel movements per se, the operator must specify the movements via the central control panel or the mobile handheld unit. He must teach-in the robot — specifying the path, velocity and acceleration of the insertion movement. The “iQ motion control” assistance system reduces this teaching effort to a few clicks.

Optimized motion planning saves cycle time

Linear robots generally move from point to point. These individual points are specified during teaching. The plant operator determines the trajectory manually and specifies many points to optimize the paths (Fig. 1).

Fig. 1. iQ motion control operates with optimized motion planning (right). The path is computed as a whole and not generated by approximate positioning of single-axis movements.

In the iQ motion control feature, which has the new ENGEL viper series linear robot on board as standard, optimized motion planning was already implemented. The linear robot calculates its path and significantly fewer parameters therefore need to be set or positions taught. This significantly shortens the cycle time of the injection molding process as well as the setup time and the time required for teaching (Fig. 2).

Fig. 2. The juxtaposition illustrates the high potential of iQ motion control for cycle time reduction.

iQ motion control is the latest product in ENGEL’s range of intelligent assistance systems. To offer the greatest benefit for users, operation of the assistance systems must be very simple. iQ motion control, too, therefore has an intuitive dialog with all the available options for setting the removal (Fig. 3).

Fig 3. Intuitive user guidance is a prerequisite for the acceptance and success of intelligent assistance systems.

Optimized motion planning in three steps

To plan the robot motion during entry such that it reaches the removal position at precisely the point when the mold terminates its opening motion, certain background conditions must be taken into account: first the parameters set by the user, such as position and linear clearances, as well as the motion of the mold; on the other hand, the robot-specific threshold values for velocity, acceleration and other parameters.

Determining the optimum entry motion requires the following steps, which are processed automatically with the iQ motion control activated:

The function compensates for any long-term effects, such as differences in the running behavior of a cold and warm machine, temperature influences, etc.

Early start desired and supported

In modern systems, the cycle time is also unnecessarily prolonged if, while opening, the mold has to wait for the robot to enter into the removal area and demold the parts. Since, thanks to the integrated control system, the robot in an ENGEL injection molding cell has direct access to the machine data, such as mold opening stroke and position of the moving platen, the robot and machine execute a coordinated movement and, ideally, are at the removal position and mold-open position respectively at the same time for removal. In this case, the cycle is not prolonged by entry of the robot.

The cycle time is shortened with the aid of the iQ motion control since the mold does not have to wait for the robot. This is achieved by the fact that the robot does not have to wait for the complete mold opening stroke during entering but can enter into the machine area at an early stage due to the already familiar “early start” feature, which is completely integrated in the software.

The settings dialog displays a suggestion for the early start position, which is based on the robot and machine setting parameters. This allows even less experienced machine operators to efficiently and reliably leverage the advantages of the assistance system.

Multistage reliability through intensive data exchange

Despite the early entry into the machine area, a collision between the robot and moving mold half can be ruled out with certainty, since iQ motion control operates with a two-stage safety net. The first stage corrects the robot movement at an early stage in the event of identified deviations from the planned mold movement. The second stage ensures that the robot can brake in good time before contact with the mold in the event of an exception situation or an emergency stop.

Since the robot knows the exact position of the movable mounting plate, it consequently also stops if such a collision threatens. In this way, damage to the mold and gripper system due to unforeseen incorrect positions or faulty settings can be reliably avoided thanks to the direct data exchange within the common control system of the integrated system solution.

Even processes with simple removal movements can be very readily optimized by iQ motion control. Users producing deep injection molded parts – for example housing components, boxes or containers with a long core benefit particularly greatly, since the machine must execute a particularly large mold opening stroke.

If the robot travels into the mold area already during the mold opening movement, this can shorten the cycle time. The effect is particularly large in the case of parts with long cores, such as boxes.

To exploit the potential, ENGEL has performed tests with a viper 12 linear robot. With a mold opening stroke of 490 mm and a maximum velocity of the movable mold mounting plate of 1465 mm/s, an overall cycle time of 15 s was achieved. The robot early start was at mold position 303 mm. A greatly shortened waiting time was found (Fig. 5).

Fig. 5. The trials confirm the greatly reduced waiting time with iQ motion control and early start.

The waiting time means the time that elapses between the completion of the mold motion and the end of the phase during which the gripper enters into the mold space. It directly forms part of the cycle time because the mold is blocked by the robot during this time span. With an overall cycle time of 15 s, for an assumed continuous operation of 24 h, with iQ motion control and with early start, 236 more parts per cavity can be produced per day than with sequential three-point removal (Fig. 6).

Fig. 6. The reduced cycle time leads to a significantly higher output source.

The use of iQ motion control is independent of the injection molding machine type and the type of removal. The assistance system automatically adapts to the respective removal variant. This comprises both vertical and — in the case of tie-bar-less machines — horizontal removal for the known construction variants, as well as deposition at the operator side, non-operator side and at the end side in the case of longitudinal constructions.

This feature will not remain the only one targeted at an even closer interplay between the machine and robot. However, iQ motion control is ENGEL’s first assistance system comprising the machine-robot.

Due to the protruding kinematics, linear robots systemically tend to vibrate. Thanks to iQ vibration control, the intelligent motions in robots of the ENGEL viper series prevent undesirable deflections. Waiting times at the end of the motion are therefore no longer required. iQ motion control goes a step further. By the fact that smooth fourfold-constant motions do not excite vibrations, there is no loss in cycle time due to the compensation of large vibrations (Fig. 4).

Fig. 4. Examples of smooth movement profiles of robot axes. Vibrations of the robot axes can also prolong the cycle time.

Deborah Lidauer is head of Product Management Automation at ENGEL AUSTRIA GmbH, Schwertberg, Austria

DI Dr. Matthias Oberherber is control systems engineer at ENGEL

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