Prototype Slitting Machine
Project Overview
Proof of concept manufacturing process capable of creating slits in plastic straw developed, designed, and prototyped for external customer. Project carried from concept generation to preliminary testing. Achieved 1st Place in Senior Design.
Project Objective
Design a manufacturing process that can consistently create four identical equidistant slits on a plastic straw and develop a proof-of-concept prototype to validate the process. Compete in senior design showcase competition at the conclusion of the project.
Specifications
- 6 second cycle time
- Slit length of 2.5 ± 0.2”
- Slit width of 0.02 ± 0.005”
- Slit positioning 0.25 ± 0.1”
Technical Process
1. Scope Management
Continuous communication with customer was conducted to refine project scope and requirements. Weekly meetings were used to discuss any necessary changes to expectations and update customer on design updates.
2. Initial Experimentation
Experiments with numerous blade shapes and cutting techniques were evaluated to identify optimal method. A variety of straw holding techniques were explored as well.
3. Concept Generation
Process was decomposed into the holding and slitting mechanisms. Initial concepts were generated. These concepts were presented to customer alongside benefits and drawbacks. A vertically moving slitting mechanism where the straw traveled horizontally was selected.
4. Concept to Design: General Practices
Prototype was designed to allow for easy iterating while maintaining accuracy. Mechanisms were designed to minimize play and were constantly refined to reduce cost.
5. Concept to Design: Actuation
Pneumatics were selected for actuation. Linear actuators, airlines and valves were sized and schematics created.
6. Concept to Design: Control
The sponsor did not want to invest heavily into control yet, so an Arduino was selected to control the manufacturing cycle. A simple open loop cycle was coded to facilitate the process.
7. Prototype Fabrication
From the final design, a bill of materials and manufacturing design package was generated. Custom components were milled from aluminum stock. Stainless steel mandrel arms were 3D printed on an EOS M290 Printer. The prototype was fabricated in stages with frame components being assembled prior to the installation of pneumatics and control
8. Process Evaluation
Established operating procedure and conducted quality control study on designed process. Measured product outputs and utilized ANOVA to determine if process consistently produced the required slits.
Outcome and Impact
- The final prototype was evaluated in line with customer requirements:
- Slit length found to be within tolerance but failed to be entirely linear or equidistant.
- Results presented to customer and despite shortcomings, they felt prototype provided significant proof of process.
- Final Design a development process presented at 2024 Fall Senior Design Showcase where 1st Place was awarded.
Manufacturing Drawings
