Note to Reader[edit | edit source]
The resulting paper of this literature is pending submission and publication, check back later for results!
Background[edit | edit source]
Search Strategy & Terms[edit | edit source]
Key words terms (KWT)
- "Plastic" AND "Sheet Press"
- "Thermoforming"
- "Compression Molding"
- "Plastic Processing"
Strategies
- Searched browser and Google Scholar using KWT 1-4.
- Precious plastics reference.
What is Waste Plastic Pressing?[edit | edit source]
The open source waste plastic sheet press is a low-cost, large-volume plastic molding process designed to handle waste plastic with minimal preparation. It uses compression molding, a type of thermoforming that applies pressure and heat to mold thermoplastics into desired shapes around a mold. This technology aims to divert waste plastic from landfills by recycling it into useful products, such as large sheets that can be further processed.
Theoretical Framework[edit | edit source]
Compression molding, the core technology behind the waste plastic sheet press, operates on the principles of thermoforming. This process involves heating plastic until it becomes pliable, then pressing it into a mold where it cools and solidifies into a new shape. The process is particularly suited for recycling because it can accommodate plastics of varying cleanliness and composition, unlike more sensitive methods that require pure, sorted materials.
Significance and Importance[edit | edit source]
The significance of the open source waste plastic sheet press lies in its potential to address the environmental impact of plastic waste. By providing a cost-effective means of recycling, it supports waste reduction, resource conservation, and pollution prevention. Additionally, by being open source, it democratizes access to recycling technology, allowing communities, small businesses, and developing countries to adopt and adapt the technology to local needs.
Current State of the Art[edit | edit source]
The development of waste plastic processing technologies has evolved over time, with recent advancements focusing on improving efficiency, reducing costs, and enhancing the quality of recycled materials. The open source waste plastic sheet press represents a novel contribution to this field by combining the principles of compression molding with an open source ethos. It stands out for its accessibility, scalability, and adaptability to different types of waste plastics and product specifications.
Relevant Stakeholders[edit | edit source]
Stakeholders in the open source waste plastic sheet press project include environmental organizations, recycling companies, community recycling initiatives, makerspaces, educational institutions, and policy makers. These groups have a vested interest in promoting sustainable waste management practices, developing circular economies, and fostering innovation in recycling technologies.
Applicability and Context[edit | edit source]
The applicability of the open source waste plastic sheet press is broad, with potential uses in various contexts worldwide. It is particularly relevant in areas with limited access to recycling facilities, as well as in settings focused on sustainable development, such as eco-friendly product manufacturing, educational programs on recycling, and community-led environmental initiatives. The technology's open source nature ensures that it can be adapted to meet the needs and constraints of different regions, cultures, and economies.
Literature[edit | edit source]
TODO[edit | edit source]
- Electrical and controls
- Thermocouple grounded vs ungrounded
Compression Molding[edit | edit source]
Potential for Reuse of E-Plastics through Processing by Compression Molding[edit | edit source]
W. Mills and R. Tatara, "Potential for reuse of e-plastics through processing by compression molding," Challenges, vol. 7, no. 1, 2016.
- Average tensile strength of molded e-plastics with an impure composition: 29.3 MPa
- Heterogeneous results with plastic inclusions and internal voids due to nonmelted plastic
- Provides mechanical properties of compressive molded plastics, and suitable compression molding conditions
- molds should include features to promote venting of gases to improve strength and eliminate internal voids
- procedure ideal for moderate strength and durability applications including "are outdoor stakes, signs, frames, planting containers, fencing, and furniture components"
- recommended conditions: softening the charge with 30 min of preheat at 204 °C, followed by a molding pressure of 17.2 MPa at 204 °C for 4 min.
- 7075-T651 aluminum three-cavity mold was utilized
Modeling and Optimization of a Plastic Thermoforming Process[edit | edit source]
Yang, C., & Hung, S.-W. (2004). Modeling and Optimization of a Plastic Thermoforming Process. Journal of Reinforced Plastics and Composites, 23(1), 109–121. https://doi.org/10.1177/0731684404029324
- Methods of thermoforming:
- place/pour liquid viscous plastic over a mold and apply either a differential pressure (vacuum forming) or a plug and clamps
- Ideal for large scale products that cannot feasibly be tackled with injection molding and where bulk production is not necessary (i.e. prototyping)
- typical problems observed in thermoforming:
- nonuniform thickness distribution
- Quality dependent on:
- temperature of heating pipes
- vacuum pressure
- plug material
- plug moving speed
- plug displacement
- Method:
- Pipe heaters oriented perpendicular in plane between top and bottom press plate
- use of an assisting plug is most widely used for deep drawing
- pneumatic plug – allows velocity of plug to be adjusted based on flow rate
- heated material well above glass transition temperature
- verified the accuracy of the final product relative to intended geometry using micrometers
What is Thermoforming and How Can the Process be Used in Product Manufacturing?[edit | edit source]
Sealwerks-Author, "What is Thermoforming and How Can the Process be Used in Product Manufacturing?," SealWerks. [Online]. Available: https://radiofrequencywelding.com/what-is-thermoforming-and-how-can-the-process-be-used-in-product-manufacturing/#:~:text=Thermoforming%20is%20a%20process%20of,cools%20into%20the%20desired%20shape. [Accessed: 18-May-2022].
- Typical tolerances for:
- forming: +/-.025" between parts
- perimeter die cut: +/-.060"
- Maximum mold size: up to 30" wide
- Maximum depth of draw: 8.0"
- Maximum sheet thickness: 0.80"
- Molds are temperature-controlled aluminum
- Common thermoforming materials
- Benefits of thermoforming
- ideal for large parts
- multiple finished parts from the same material
Guide to Compression Molding From Prototyping to Mass Production[edit | edit source]
"Guide to compression molding from prototyping to mass production," Formlabs. [Online]. Available: https://formlabs.com/blog/compression-molding/. [Accessed: 18-May-2022].
- Basic methodology outlined: heated charge loaded into the profiled top and bottom plates of a cold press
- due to varying thicknesses of the profiled surfaces, uneven heat distribution may occur resulting in imperfections
- mold design:
- loaded charge
- overflow grooves to capture plastic
- ejector pins to remove the completed part and ensure it does not become stuck within the mold
- Advantages:
- cost effective for large, mostly flat, simple parts
- lower pressure than alternative extrusion or injection molding
- can adjust molds to produce multiple parts at once
- high structural stability
Existing Design Methodology of Sheet Presses[edit | edit source]
Build a Sheetpress (AND Sheetpress an Overview)[edit | edit source]
"Precious plastic community," Precious Plastic Community, 11-May-2022. [Online]. Available: https://community.preciousplastic.com/academy/build/sheetpress. [Accessed: 18-May-2022].
Alternative Design Methodology 1:
- complete detailed breakdown of engineering specifications, drawings, assembly methodology, and cost breakdown for an open source and accessible metric sheet press
- more energy efficient when conduction is used in place of convection
- fixed datum top plate and vertically adjustable lower pressing plate
- single bottle jack used at center of bottom plate to guide pressing plate along 4 guideposts
- 8 tons of pressure for the hot press, and 3 tons for the cooling press
- Use of a hot press, cold press, and prep table to maximize efficiency
A locally producible plastic plate press for bottom-up recycling in low-resource settings[edit | edit source]
M. Bachrach, "A Plastic Plate Press: A locally producible plastic plate press for bottom-up recycling in low-resource settings," thesis, TU Delft Library, Delft, 2018.
Alternative design Methodology 2:
- four inclined bottle jacks at each of the four corners of the plate press
- press surface constructed from large rectangular steel extrusions to provide active cooling and lateral stiffness
- robust design and adjustable top plate position
- Welded frame assembly
- symmetric welded mold with bent handles for ease of use. Top and bottom molds nest, and top press plate footprint fits within profiled mold to apply even pressure
- improved mold design for plastic overflow and minimized post processing of produced sheet
Heat Press Machine[edit | edit source]
Jaymin, "Heat Press Machine," Dave Hakkens, 02-Mar-2017. [Online]. Available: https://davehakkens.nl/community/forums/topic/heat-press-machine/index.html. [Accessed: 18-May-2022].
Alternative Design Methodology 3:
- lower plate acts as the datum (immovable) plate, upper plate acts as the adjustable compression plate
- Top plate adjusted using a central lead screw and manual crank drive
- Single, large lead screw and hand crank method makes it more ideal for small scale pressing
- flat disk heat cartridges/coils installed in both the top and the bottom plates
- relied on a polished top plate being in direct contact with the plastic (versus typical alternative designs in which a mold act between the press and plastic)
- high energy consumption and slow cooldown time
- 3-hour process time
Protomax Plastics large sheet press[edit | edit source]
Automated P2 Plant. YouTube, 2016.
Alternative Design Methodology 4:
- Large scale press relying on a hinge mechanism and table clamp in place of a vertical actuator joining two tables
