Senior Capstone: Automated Box Conveyor
Skills:
project management, problem solving, machine shop, electrical engineering, circuit design, microcontrollers, programming, finite element analysis, CAD
Project Overview:
My undergraduate capstone project was to design, construct, and install a fully automated box conveyor for our local food bank. The conveyor is capable of holding boxes still while being filled, then advancing them one-by-one as they are offloaded onto a pallet for transport. This ended up being one of the biggest and most expensive projects undertaken by the mechanical engineering department to date. My team and I finished the project with a fully-functioning product to deliver to the client.
If you would like to know more, please continue reading.
Needs Finding:
South Plains Food Bank supplies families in need across the plains of west Texas with meals when they have run out of options. The beautiful new facility houses everything each family will need to thrive. Qualifying families receive packages containing fresh produce, bread, frozen goods, and dry goods. As is the case with many non-profits, the organization relies heavily on volunteers to help pack boxes with the nutritious food required by the patrons. A key location for volunteers is the dry food boxing area where items like rice, pasta, drink mixes, canned goods, and snacks are portioned and sorted from donated pallets to the boxes for distribution.
Upon reception of our assigned project, I suggested that we volunteer for a day in the dry food boxing area to assess and identify the need directly from the regular volunteers and area managers. Here, we saw volunteers construct and line boxes along two sides of a well used, worn out roller table. These boxes were then filled with food, closed, and loaded, one by one, onto pallets. Even when there were many volunteers, it was difficult to move a full line of boxes down the roller table. It was learned that sometimes only the manager and one staff member are present in the area and that she alone must offload the boxes, walk around the table, push the line forward, and repeat the process throughout the day. We also learned the table was too high for many of the volunteers to comfortably load the boxes. After this fruitful day of observation and volunteering, we were ready to establish the project requirements.
Through exhaustive brainstorming sessions, the team decided that the main needs were as follows:
- An easier, more efficient method for moving and offloading full boxes
- Fully operable by one or two individuals
Project Organization:
After the initial brainstorming and establishment of project guidelines and requirements, I made the decision to split the sizable team up according to category of work:
- Structural: Side beams, supports, rollers, and legs.
- Drive: motors, motor mounts, drive belts, tensioners, belt safety covers
- Electronics: Automation equipment, VFDs, microcontroller, user input interface
My Contribution:
I acted as project manager for both semesters of the project and was the principal member of the electronics team. Having completed two internships at Sandia National Laboratories (SNL) working in an electrical engineering group, I had the most experience with electronic component design. This being said, I am a mechanical engineer, not an electrical engineer, so from the beginning, I ran into problems I did not know how to solve.
I began by seeking out resources to get me up to speed on the electrical components and circuit design that would be required for the project. I read journals, consulted professors in the electrical engineering department, and turned to one peer in particular with whom I had worked at SNL.
Because this was a senior capstone, and we had been tasked with building something that already, in essence, exists in every automated warehouse in the world, we decided to include a microcontroller as the central processing hub for the system, rather than the standard industrial controllers. This decision, for better or for worse, made our system novel.
The system I designed consisted of two retroreflective lasers (above) to stop forward movement when tripped, a control box with knobs and a button for power and forward/reverse and an emergency shutoff (below), the microcontroller, two variable frequency drive (VFD) units, and an auxiliary emergency cut-off fail safe. Parts and professional advice were acquired from both local and international companies.
The greatest challenge in the electronics portion of this project was assembly. The industrial size of the system meant we were working with 480V three-phase power supplying the motors, 220V/110V as power for the micro controller, a 12V circuit for relays and optics, and 3.3V–5V on-board signals. We were also dealing with base high and base low signals from the microcontroller that were not well documented. This being the case, I extensively used relays to allow circuits running two different voltages to “talk” with each other.
An example of some of the on-the-spot engineering required for the completion of this project was sourcing relays that would allow the 12V circuit for the optics to communicate with the 5V microcontroller. Installation of the conveyor happened primarily at night and on weekends when the food bank was closed. Unfortunately, most of the industrial electronics businesses were also closed nights and weekends. When we had to make a last minute change to the system (going from a 6V generator to a 12V to meet the requirements for the lasers) our on-board relays would no longer be able to take the load. Without any local businesses open, I needed a solution quickly. With some quick thinking, I knew the vast majority of cars run a 12V circuit for onboard electronics and signaling, and therefore, any auto parts store would have the relays we needed to complete the project. Using automotive relays, I was able to set up the required circuit and saw the rollers move for the first time that day.
I also designed and built two electronics enclosures to house the VFDs and microcontroller. Both were fully enclosed, properly grounded, and used components standard to the electrical industry.
Project Outcome:
Many months of very long hours were put into this project and in the end, we were able to deliver a fully functioning automated box conveyor to South Plains Food Bank.
Volunteers line boxes on both sides of the conveyor just as with the original table. Our table was shorter than the original to make loading the boxes easier for shorter individuals. These boxes are stationary while they are filled with dry goods and closed. One or two volunteers then move to the offloading end of the conveyor where they remove the first boxes on each side. The line of boxes is then moved forward until the laser beam is broken and the next box is ready to be picked up. When all boxes have been offloaded, the next batch of empty boxes can be loaded onto the conveyor and the process can be repeated.
The project was completed May 2019 and the conveyor is still in use and operational.
Additional Information:
If you would like to read more on the impact this project had on the community, please see the following links. All content in these links is owned by the respective parties with which I have no affiliation.
