Monday, May 3, 2010

Team F - Santa's Little Helpers - Package Wrapper

Main Design Concept

The main concept behind our package wrapper design was that we would have two arms that moved horizontally in order to pick up, rotate, and fold the paper onto the box. The arms have carefully crafted gripper hands that allow for folding and gripping. These arms can also move the box vertically so that the paper can be slid underneath it, and can rotate so the paper can be wrapped around the box. There are two CAD drawings of the final project below in Figure 1 and Figure 2. Figure 1 provides a nice view of the multi-purpose gripping hands in relation to the entire project. Figure 2 provides a more detailed look at the hands.

Figure 1: Final Project, Top View

Figure 2: Detailed View of Gripper Hands

Team Members and Responsibilities
Gregory Pitts : Electronics and Control
Eric Tsai: Electronics and Control
Wei-Hsuan Chen: Mechanics
Kay Csuri: Mechanics

Overall System Description
Like all package wrapping teams, we had five subsystems. Below in Figure 3 is a modified CAD drawing that has the five subsystems labeled.

Figure 3: Labeled view of the overall system

  • Paper Feeder sub-system: The paper feeder is what is used to unroll the paper. It has a controlled clip that releases the paper once it is unrolled beneath the box.
  • Paper Cutter sub-system: The paper cutter cuts the paper vertically when is is unrolled, and then slides across to perform a horizontal cut.
  • Package Measurement sub-system: The package measurement sub-system measures the width of the package by sensing how far in the arms are when they grab the box.
  • Paper wrapper/folder sub-system: The paper wrapper/folder subsystem wraps the box by rotating it with the paper adhered to it and folds by using the top of the grippers to fold down the paper.
  • Paper adhesion sub-system: The double sided glue applicator passively applies glue to the paper when it unrolls.
Further Subsystem Explanation
As stated earlier, there were 5 sub-systems in the project. This section will explain each one in greater detail.
  • Paper Feeder: The paper feeder was the first sub-system constructed in our project. In the design, the paper is manually clipped into the two clips. One clip is controlled with a servo motor and the other one is a binder clip. When the box is lifted by gripper arms, the paper feeder rolls across the platform, unrolling the paper. The system is driven by a DC motor. Finally, the device runs into a slot sensor that stops the DC motor. When the motor stops, the clip controlled by the servo is opened. The binder clip is clipped to paper that was already cut of by the cutting sub-system. A labeled picture of the paper feeder is shown below in Figure 3.
Figure 3: Labeled photo of the paper feeder

  • Paper Cutter: The cutter sub-system has two aspects. The first aspect happens directly after the measuring of the box occurs. When the system knows the width of the box, it moves the cutter across horizontally so it can cut the paper as it unrolls. This degree of freedom is controlled by a DC motor. The system then lowers the blade to pierce the paper and cuts it vertically when it is unrolled. Once the paper feeder is done unrolling, the blade moves and positions itself to cut horizontally. The action of positioning the blade is controlled by a small servo motor. Once the horizontal blade is positioned, the DC motor activates and slices the paper. Figure 4 shows the two blades and the DC motor that drives the horizontal DOF, as well as the horizontal and vertical planes
Figure 4: Paper Cutter sub-system

  • Package Measurement: The package measurement system is integrated into the horizontal motion of the gripper arms. When the horizontal arms move in, there is a slot sensor that moves along a series of ridges and counts how many it passes. When the arms grip the box, a pressure sensor detects when it is gripping hard enough to lift the box. The system remembers the number of notches it has moved the horizontal arms and uses that as the measurement of the box. There is no need to measure other aspects of the box in our design.
  • Paper Wrapper/Folder: The paper wrapping and folding system was the most complicated of our design. There are several aspect. One aspect is that the horizontal arms move in to grip the box. Each arm is driven by a servo motor. Then, the arms rise while gripping the box. These are driven by a lead screw attached to a DC motor. This can be seen in Figure 5. Once the box is raised, the paper feeder rolls out the paper beneath it. Once the arms set the box down and it is adhered to the paper, the box is lifted and rotated to wrap the paper around the box. This rotation is driven by two servo motors. Figure 7 below shows these motors, but they are not labelled. Finally, the grippers rotate 180 degrees and fold the paper down on each side. This process is shown in Figure 6.
Figure 5: Vertical motion components

Figure 6: Photo of the folding action

  • Paper Adhesive: The adhesive sub-system is a passive system for applying glue to the paper. As the paper gets pulled out, it is pulled against three glue dispensers that apply enough glue to adhere it to the box. Figure 7 shows a CAD drawing of the system, with the adhesive applications labelled.
Figure 7: CAD Drawing with the adhesive applications labelled

Overall System Process
The overall system process will describe the actions of the system from start to end
  1. Paper is placed into clips
  2. Box places in the middle of the platform
  3. Arms move in, sense width, grip box, and rise
  4. Paper feeder unrolls paper, adhesive is passively applied, vertical cut is made, and clip is released.
  5. Box is placed back onto the paper, adhering to it.
  6. Box picked back up and raised. Rotates 360 degrees to wrap the paper around the box. 
  7. Box is placed on the ground. Folding on top side is done.
  8. Box is picked up and rotated 90 degrees. Folded on the new top side.
  9. Repeat step 8 twice.
  10. Box should be fully wrapped.

Video of the System in Action

No comments:

Post a Comment