In-class disassembly exercise

Transcription

1 In-class disassembly exercise Students dismantle obsolete computer keyboards, telephones or like-size objects, preferably of different makes and dates (such as IBM and Apple). Instructor and students bring to class: 1. Keyboards or other objects, 1 for 2 or 3 students if large class 2. Simple tools (screwdrivers, plyers and cutter), 1 set per team 3. A magnet (to differentiate between iron and other metals) 4. A scale (to weigh objects and parts) Activities: 1. Weigh the object. 2. Consider ergonomicity (curved shapes to prevent injuries during use). 3. Dismantle the objects as far as possible. 4. Weigh plastics and metals. Weigh recyclables and disposables separately. 5. Consider the following aspects during disassembly: Things to look for during disassembly: MATERIALS: 1. Variety of materials (How many different plastics and metals?) 2. Quantity of materials (More than strictly necessary?) 3. Hazardous materials (Lead solder?) 4. Recyclability of each part (Each part down to a single material? Glue holding labels?) 5. Disposal of non-recyclable parts (Energy recovery? Safe to landfill?) 6. Toxicity of landfilled materials (heavy metals?) DESIGN: 1. Modularity (Are there modules? And, are they easily accessed?) 2. Serviceability (Are repairs possible to prolong life?) 3. Refurbishing potential (Can refurbishing be done to re-sell on second-use market?) 4. Multi-functionality (Are there parts cleverly used for multi purposes, such as cover and structural stiffness? Single screw or snap holding more than two components?) 5. Ease of disassembly (Energy & time required? Need for special tools? Complexity?) 6. Ease of identification and sorting (Are plastics labeled with international codes?) 1

2 Post-disassembly discussion and brainstorming 1. Fraction of plastics and metals. Could have been done without certain metals or plastics? 2. Fraction of recyclables versus non-recyclables? Is most of it recyclable? 3. List environmentally friendly aspects. Compare between the various models. 4. List problems encountered: - Excessive use of materials, - Excessive variety of materials, - Presence of adhesive labels, - Lack of labeling of plastics, - Lack of modularity, - Disassembly requiring excessive number of steps, - Disassembly requiring special tools, - Disassembly demanding irreversible breaking and preventing serviceability, - Hard-to-reach module. 5. Brainstorm about improvements (to overcome the preceding problems). Some additional elements regarding disassembling 2

3 Factors to consider in design for disassembly Design for ease of disassembly Reduce the number of assembly operations Simplify and standardize component fits and interfaces Make components modular Select easily recyclable materials Minimize the variety of different materials used Use compatible materials (esp. plastics) Consolidate parts used (ex. identical screws) Marked materials to ease and enhance separation (esp. plastics) Avoid rivets (use screws or, better, snap-clips) Avoid adhesives (imprint information instead of sticking a label) If adhesives must be used, select water-soluble kind As one progresses in the disassembly, the needs change from ease of access (larger parts) and fewer parts to ease of sorting and reduced material variety. optimal compromise between environmental benefit and economic return time spent and cost of operation 3

4 Automotive example: Product = car Modules = engine, transmission, door, bumper, dashboard Assembly = piston, locking mechanism, ignition key assembly Parts = piston ring, screw, wire Material = cast iron, steel, copper, plastic, rubber, glass 4

5 Example ELEMENT DESCRIPTION MATERIAL RE-USE RECYCLABILITY Component Composite Waste (0) 4 5 Component Valuable (3) OPERATION Component slide away remove Snap-fit open Clip remove Connection break Wire disconnect MEAN TIME REQUIRED 1.25 sec 0.6 sec/turn 1.5 sec 1.0 sec 2 sec 1.5 sec In which order do you proceed to remove - only what is valuable? - what is valuable and reusable? - all that is valuable, reusable and recyclable? 5

6 Disassembly trade-offs Destructive versus non-destructive disassembly: Destructive disassembly is faster and therefore cheaper, but generally yields lower-value results, and often results in mix of various materials. Non-destructive disassembly allows scavenging of reusable parts, better separates materials, but is slower and may require specialized tools. One screw holding many parts together: Advantage = quick disassembly Disadvantage = less robust product s and snaps: Advantage = reversible assembly / disassembly (avoids destructive disassembly) Disadvantage = not as strong as welding and rivets (esp. when vibration is an issue) 6