P18432: Plastic Bottle Rope Machine Improvements
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Systems Design

Table of Contents

Team Vision for System-Level Design Phase

Throughout this phase our team identified the core concepts and individual tasks that our system needed to perform. From these small tasks we broke down how a system/mechanism could accomplish these tasks into concepts. Each of these concepts was evaluated for feasibility if possible and from that feasibility the concepts fitness for use was determined. After performing such a feasibility analysis systems comprised of some of these concepts were drawn up and evaluated against each other.

Functional Decomposition

The overall goal of this project was broken down into small discrete tasks to be performed at some level in the system.

Figure 1: Functional Decomposition

Figure 1: Functional Decomposition

















































Benchmarking

Type of Models Looked at

  1. Bottle Stringer
  2. Rope Machine
  3. Connect String

Different Models

  1. Bottle Stringer: Thingiverse 3D model,3D Prototype Updated and Improved, Kick Starter Device
  2. Rope Machine: Mechanical Machine Braiding, Rope Twisting Machine, Soda Bottle Rope Machine
  3. Connect String: Tie Two String Together and Splicing Method (Grass Version)

Details can be found on the following link.

Concept Development

Generate new concept options or combinations that can potentially exceed the benchmark concepts. This stage helps us take the information form the functional decomposition and benchmarking and begins to create ideas for individual tasks that need to be completed within the individual subsystems of the project.

Figure 2: Concept Generation

Figure 2: Concept Generation

Feasibility: Prototyping, Analysis, Simulation

Rope Breaking Strength

To determine the breaking strength of the rope we can extrapolate from the breaking strength of PET, the cross-sectional area of each strand, and the number of strands woven into each rope.

PET Yield Strength = 55 MPa Bottle thickness = .3mm String width = 4mm Number of Strands per Rope = 48

String Tensile Strength = Yield Strength * Bottle thickness * String Width

String Tensile Strength = 66N

Breaking Strength of Rope = Number of Strands * String Tensile Strength

Rope Breaking Strength = 3168N

Joining Strength

Determine whether or not the chosen method of joining strands together is strong enough to support the final tensile strength of the rope.

Preliminary Cost Analysis

Figure 2: Preliminary Cost Analysis

Figure 2: Preliminary Cost Analysis

Morphological Chart and Concept Selection

Morph Tables

Table 1: Morph table for cutting string from bottles
Function Concept 1 Concept 2 Concept 3 Concept 4 Concept 5 Concept 6 Concept 7 Concept 8 Concept 9
Shear String Razor Blade Bearings Perforator Angled Razors Scissors Laser Knife
Hold Bottle On top of post Inside Cylinder Collapsing cylinder Spring arms inside bottle Weighted guide By hand
Guide Bottle Flat table Rollers Conveyor By hand
Spool String By hand after cutting Crank string onto spool while cutting Electric Motor Gas engine Gravity Springs Natural coils Don't By hand
Guide String Spool Eyelet Slit Tube Straw By hand
Connect Strings Staple Laser melt Heat bonded Adhesive Knot Interweave Sonic welding Hold together by hand
Clean Bottles Water Power washer Compressed air Soap and Water Don't Chemical cleaner
Reform Bottles Pressurized air By hand Inflate bladder inside bottle Stomp Rockets style inflation
Cut off bottom Laser Knife Razor Scissors Paper guillotine Saw Can opener style
Remove Label By hand Soak in water Don't Pressurized air Chemically
Acquire Bottles Outsource Wind Ocean currents By hand Pay street children Nets Bags
Table 2: Morph table for weaving rope from string
Function Concept 1 Concept 2 Concept 3 Concept 4 Concept 5 Concept 6
Hold Spool (of string) Vertical spindle Hand Roller On the ground (Don't)
Rotate String Crank Pedal By hand Power tool Water power Wind power
Prevent Fraying Splice strings Tie strings together Melt strings together Adhesive Tape
Weaving Method Twisting Braiding Boondoggle weave Don't
Collect Rope Spool Weighted Drum By hand
Section Rope Cut and tape Adhesive Bottle Necks Melt chemically Melt thermally

Alternative Identification

Table 3: Alternative Identification chart for cutting string
Function Alternative 1 Alternative 2 Alternative 3 Alternative 4 Alternative 5
Shear String Bearings Bearings Bearings Bearings Bearings
Hold Bottle On top of post Collapsing cylinder Spring arms inside bottle Spring arms inside bottle On top of post
Guide Bottle Rollers Rollers Flat table Rollers Flat table
Spool String Crank string onto spool while cutting By hand By hand Crank string onto spool while cutting Crank string onto spool while cutting
Guide String Eyelet Tube Spool Eyelet Tube
Connect Strings Tie strings Tie strings Adhesive Tie strings Weave strings together
Clean Bottles Water Don't Soap and water Water Don't
Reform Bottles By hand By hand Pressurized air By hand Pressurized air
Cut off bottom By hand By hand Paper guillotine By hand Paper guillotine
Remove Label By hand Don't By hand Don't By hand
Acquire Bottles Pay street children Pay street children outsource By hand Outsource
Table 4: Alternative Identification table for weaving rope from string
Function Alternative 1 Alternative 2 Alternative 3 Alternative 4 Alternative 5
Hold Spool (of string) Vertical spindle Roller Roller Spindle By hand
Rotate String Crank Pedal Crank Power tool Crank
Prevent Fraying Splice strings Tie rope together Tape strings together Splice strings together Tie rope together
Weaving Method Twisting Braiding Twisting Twisting Braiding
Collect Rope Spool Weighted Drum Spool By hand Weighted Drum
Section Rope Cut and tape Bottle Necks Adhesive Cut and tape Cut and tape

Concept Selection

Table 5: Pugh chart for String cutting alternative comparison
Function Last Year Alternative 1 Alternative 2 Alternative 3 Alternative 4 Alternative 5
Completion in 2 Semesters + o datum o o o
Safety o ~ datum ~ ~ ~
String Width Consistency ~ + datum ~ + o
Production Rate ~ + datum ~ + +
Cost + ~ datum ~ ~ ~
Ease of Use o + datum o + +
Construction Material Availability + o datum ~ o ~
Scalability o + datum o + +
Complexity + ~ datum ~ ~ ~
String Quality ~ o datum o o o
Ease of Maintenance + ~ datum ~ ~ ~
Table 6: Pugh chart for rope weaving alternative comparison
Function Last Year Alternative 1 Alternative 2 Alternative 3 Alternative 4 Alternative 5
Completion in 2 Semesters + o o datum o o
Safety + o ~ datum ~ o
End Rope Length ~ o o datum o o
Production Rate ~ ~ + datum + o
Cost + o o datum ~ o
Ease of Use ~ ~ ~ datum + o
Complexity + o ~ datum o o
Construction Material Availability + o ~ datum ~ o
Quality of Rope ~ ~ + datum ~ +

This consists of two elements:

Systems Architecture

The flow of the overall system is reasonably linear in terms of material being worked on with human power input at each stage.

Figure 3: Systems Architecture

Figure 3: Systems Architecture

Designs and Flowcharts

A detailed flowchart of the individualprocesses that the bottles and material must undergo throughout the entire system.

Figure 4: Design Operation Flowchart

Figure 4: Design Operation Flowchart

Risk Assessment

Figure 5: Risk Assessment

Figure 5: Risk Assessment

Design Review Materials

Plans for next phase

Team Plan

Individual 3 Week Plans


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