The objective of the proposed project was to integrate a robotic system with the ability to dispense raw material and remove a finished shower base from a molding machine.
Project Focus Points
Throughout each phase, the robotic integrator tested each design to ensure full functionality and application success.
Equipment
The equipment used for the feasibility study included:
The equipment used in the feasibility study consisted of both reconditioned components and new items. Reconditioned equipment kept cost to a minimum while demonstrating a proof of concept.
Partial Production Simulation:
The robotic integrator recommended a simulation run including:
The Feasibility Study Illustrated:
The Study Did Not Illustrate:
The results of the feasibility study and equipment use did not provide any information about cycle time for the robotic system. With the many variables that existed in this application, true cycle time could only be determined during actual production.
Discovery
A careful inspection of the shower bases was made to examine the surface contour and texture, as well as their different sizes and shapes. Because the bases did not have the same surface texture, there was some concern that they would present a challenge and create leakage around the edge of the vacuum cup. Upon further examination, it appeared that successful gripping of heavier textured parts would mean successful gripping of other parts as well. It was also determined that the weight of some of the larger parts could cause problems when removing them from the molding machine.
It was also noted, after conversations with the customer, that the raw material would need to be dispensed in a variety of different areas within the molding press. This presented a challenge for the dispensing tooling. This portion of the tooling would have to be cantilevered out an extreme distance from the end of the robot.
Results
The first trial attempt to pick up the part was done with the Piab vacuum generator and Piab suction cups. The robotic integrator was able to create a vacuum with a single cup. But the operating temperatures of the cups were at a lower operating temperature than the molding machine. The robotic integrator realized this difference in temperature would cause some part wear and tear. A silicone-based suction cup that could better handle the temperature was chosen and tested.
The second trial attempt included six suction cups at one time with the Piab vacuum generator. In order to pick up the part, a vacuum of at least 20 inches of Hg is required per cup. The vacuum generator was then run with two cups, producing 12 inches of Hg.
After failing to create enough vacuum with a Venturi style vacuum generator, the robotic integrator implemented a pump style vacuum generator. The new style of vacuum generator created 26 inches of Hg on a single cup. When the robotic integrator attempted to run all six cups at once with the large vacuum pump, a reading of 5 inches of Hg was recorded. This remained too low to pick up the part. Finally, the robotic integrator ran all six cups simultaneously on a flat surface, a piece of 16 gauge sheet metal, obtaining a reading of 26 inches of Hg.
Two possible causes for the trouble were determined from the suction cup trial results. The first cause was the air leakage that was occurring around the cup seal due to the textured surface. However, softer cups did not hold up to the temperature rating required by the customer. The second possible reason a firm seal could not be made was the volume of air being sucked through the cups. The robotic integrator even plumbed in cups with a 12 mm supply line instead of a 10 mm supply line and observed very little change in the results.
Tub And Tooling
The next challenge for the robotic integrator was to create the dispensing tub and EOAT to hold the raw material and dump it into molds. A rotary unit was purchased to handle this task. The customer required a robot that would dump materials in different areas of the press depending on the part. Another limitation was the opening size the robot had to go into and flip the tooling to dispense the material. Finally, the weight of the material was about 100 pounds prior to molding.
Because of these variables the tooling and dispensing box had to be long and narrow to achieve the right reach and volume to hold and dump raw materials. While developing the EOAT for dispensing, the robotic integrator realized the Motoman UP130 would not have the capacity to handle the weight of the extension. The tooling was adapted to fit the UP200, which has a greater capacity.
Though the EOAT was finished, the robotic integrator still had some major concerns regarding overloading the end of the robot, reach constraints, and the tooling colliding with the robot. While the UP200 greatly increased the capacity of the robot, it significantly reduced the reach of the robotic system.
With the prototype tooling mounted on the UP200, it was determined the robot would still be overloaded because the work portions of the tooling were overextended. However, if tooling was shortened, it was unable to reach inside the press to the necessary locations for dispensing or base removal.
Conclusion
The feasibility study raised some questions about the application.
Based on observations from the study, the robot appeared to be pushed to accomplish too many tasks and handle too high of a payload. The robotic integrator suggested that the customer explore the possibility of using two additional robots, one for loading raw materials, and another to extract parts from the mold. This solution would allow the customer to maintain lower payloads to accomplish the task.
