This is our first application of the Universal Robots UR-10 collaborative robot, or cobot.
Through this process we have learned and assessed the risk involved with collaborative robots including collision, caught-between, crushing, and electrical hazards. The collaborative robots are very safe but workers do need to stay clear of the movements. At higher speeds, safety barriers and/or sensors may be needed. It is also important to be cautious of the robot starting movement unexpectedly, especially if triggered by sensors that may be within operator reach. Most injuries would be more likely to occur during installation, and testing. Lock-out/Tag-out is required similar to all equipment.
The online e-learning was very helpful in allowing our team, including several apprentices, to program the various pick and place sequences, and connection to the conveyor and sensors, right out of the box.
The basic tasks previously performed by a full-time person requires nesting the two parts and separating the long and short into separate cartons.
The first step was fairly simple and involved consistently flipping one of each of the parts over. Due to the cycle time, this task was offloaded to the press robot.
We also positioned the grinder so the press robot can drop the runner to grind and reuse immediately.
After several long hours of testing we found a simple way to align the parts that greatly improved the ability to create neat pallet stacks.
The approach position also is critical to mating the parts face to face without overlap.
The project took 4 days to program including a preliminary feasibility trial and a complete do over. We found it much easier to adjust the pallet stack positions along the X Y instead of on an angle.
We incorporated a sensor at the head of the conveyor to allow the conveyor to run every two shots and a sensor at the end of the conveyor to stop it.
The sensors and outputs are wired in standardized connectors that make moving the equipment and connecting the robot to other work cells easy.
The speed of the robot had to be optimized to keep ahead of the molding machine cycle without going too fast causing it to shift around or endanger coworkers.
After the cobot completes one set of cartons on the left table, it starts stacking parts on the right table while the operator is clear to slide a box over the parts and flip it over.
The start-up requires a pre-start sequence to fill the conveyor and synchronize the operation.
Total labor time went from 40 minutes to 4 minutes per carton set. The operator is free to run other automatic jobs and take a break without a relief operator.
Each run is just a few days long before the machine has to be changed to other jobs so we have marked locations for the equipment and fixtures.
The conveyor and press robot are easily capable of running with or without the cobot to permit maximum flexibility. This was especially important as we developed the cobot program.
We used variables in the cobot program to indicate the pallet set, left or right and part and up or down position.
If-then-else statements and loops were used in the programming.
Subprograms were not used in this application.
We ran a continuous simultaneous thread program to monitor the sensors and move the belt.
There are 8 pallet stacking positions with the up position and down position overlapping.
Each pallet position and related variables are named to help organize and structure the cobot program, but the over 300 lines of code does make it a little difficult to deal with. Collapsing lines of code helps to see the overall sequence. We did not use the folders features which could have also helped. As much as we want to keep it simple, there always seems to be challenges that have to be overcome with ingenuity.
The parts cooling on the conveyor and stacks on the table allow for easy inspection and the cobot keeps the short and long parts 100% separated.
Our next application which we developed first involves unpacking substrate parts to be placed in the press for overmolding by the press robot. It connects to a conveyor and interacts with the other robot to safely enter each other’s space without collision. That application will free up a part time operator from placing 2 parts every 2 minutes to placing two cartons every 20 minutes.
This is the official news blog for Sapona Plastics, LLC.