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Product Labeling machines come in many shapes and sizes, depending on the requirements of the solution. In this case the product to be labeled is riding on a moving conveyer belt. The labeler is on a linear stage that moves parallel to the conveyor belt (see Figure 1). The challenge is to have the labeler properly align with the product and then mimic the motion of the product until the labeling procedure is complete.
 Figure 1: Product Labeling Process In this application, the Prodigy/CME board is used to control the labeler (See figure 2). A successful labeling application requires that the motion of the labeler track the motion of the conveyor belt. This is accomplished by placing an encoder on the conveyor belt, which serves as a master signal for the controller in charge of the labeler’s motion (Gear Slave).
 Figure 2: Labeler Controller System
An optical sensor is located at a known distance from the home position of the labeler. When the product breaks the optical beam, a High Speed Position Capture is triggered on the labeler controller allowing it to know the positional relationship (encoder counts) between the product and labeler (dPL). This relationship continues to be tracked until the labeling procedure has completed.
The information is used to program a SW Breakpoint that will kick-starts the labeler’s motion when the encoder reaches a specific value. The motion is “kick-started” because the action associated with the breakpoint is to place the labeler into the Gearing profile mode. The result of the kick-start is that the labeler will follow the product.
The labeler axis will undergo an instantaneous acceleration, which, depending on motor/system properties, may lose steps during the acceleration spike. To accommodate for potential lost steps during acceleration, a calibration numeric (dcal) can be generated experimentally. In this case the motion of the labeler will start when the encoder reaches a value of (dPL + dcal) plus the position of the sensor.
Another SW Breakpoint is used to trigger an output after the labeler has moved a defined distance (dlab). The output drives a relay which applies the label on the product. Once the labeler has been given adequate time to complete the labeling process, the output is disabled and it is commanded to stop tracking the product and move back to home. The system is now ready for the next label process.
Once the system is up and running, the operator can inspect the resulting label location. If the location needs to be changed, a new calibration metric can be sent to the C-Motion Engine user code running on the Prodigy/CME board. The operator can repeat the calibration as many times as needed.
1. Check for new Calibration metric (dcal) received on TCP/IP port.
2. Wait for optical sensor trigger.
3. Fetch encoder position of sensor trigger (p).
4. Setup Breakpoint 1 to initiate Gearing Mode on labeler when encoder travels.
p + dPL + dcal encoder counts.
5. Setup Breakpoint 2 to drive AxisOut when labeler has moved dcal encoder counts.
6. Wait for Breakpoint 2 to trigger.
7. Wait a specific amount of time for label procedure to complete.
8. Command labeler to move back to position “0”.
 The Prodigy CME Stand Alone Card is based on PMD's Magellan® Motion Processor and provides high performance motion control for multiple motor types. Running user code directly on the motion card to allow off-loading of the host and complete stand-alone machine controller functionality, Prodigy/CME cards are designed for demanding and precise applications such as this automatic product labeling application and other automation and instrumentation challenges.
Click to learn more about the PMD Prodigy/CME Stand Alone Card.
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