Plastic Industry
The printing of plastic parts is the main application of pad printing. The trend is moving towards direct printing at the injection molding machine, with part handling directly managed by the unloading robot.
Plastic parts are manufactured using injection molding machines, which are widely used in industries such as automotive, medical technology, electronics, toys, and household goods.
An injection molding machine can produce one or multiple parts per cycle. The cycle time is typically 45 seconds but can vary between 2 seconds and 2 minutes depending on the application.
In the standard production process, the injection molding machine produces parts that are collected and packed into boxes. These boxes are then transported to the pad printing system, where the parts are fed manually or automatically—e.g., via vibratory feeders—into the pad printing machine and repacked after printing.
To improve efficiency, pad printing is increasingly integrated directly into the injection molding machine. This approach offers numerous benefits. A robot often removes the plastic parts from the mold. If this robot directly loads the pad printing machine, additional transportation and manual loading are eliminated. The pad printing machine can also operate within the robot's safety cell, removing the need for a separate safety enclosure—another cost advantage.
A camera can be used for quality control of printed parts. It inspects both the components and print quality, transmitting the results to the robot, which then sorts the parts into "good" and "bad" boxes.
Printing requirements vary depending on the size and number of parts per injection molding cycle. For one or two larger parts, a more complex multi-color printing process is often used, requiring the part to rotate to different angles, which extends the printing process. For smaller parts (4–8 per cycle), fewer designs are typically printed, but all parts are printed simultaneously to minimize the robot's handling time.
Part handling presents a particular challenge. The robot picks up parts from the injection mold using vacuum suction, which does not always ensure precise placement in the pad printing machine. The fixture must be designed to compensate for inaccuracies. When inserting the part into the holder, it is precisely positioned to avoid misalignment or overlapping colors.
Since pad printing machines in this environment typically operate without human supervision, we recommend using automatic ink dilution and monitoring functions for the cleaning tape. In high-temperature environments, cliché cooling can be integrated. The entire process is monitored by a camera-based quality control system to ensure consistently high printing quality.