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• This method also allows many parts to be put in place, and then a number of parts assembled in one assembly step.
DI:13.2.11 Examples
•First, review the DFA handbook paying special attention to the work sheets and the tables.
•Use the DFA handbook a) To do an analysis of the assembly below (assume dimensions with an overall length of about 8”). b) do a redesign of the assembly and reanalyze.
DI:13.3 DESIGN FOR MANUFACTURING (DFM)
DI:13.4 DESIGN FOR RECYCLING (DFR)
• When disassembling a product is can be very difficult to reclaim any value.
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•There are three clear objectives when disassembling a product,
-remove subassemblies that can be resold as is.
-remove hazardous materials
-separate the remaining materials into single materials with as little effort as possible
•By following the design for assembly rules we can actually produce a part that is relatively easy to disassemble, and with some additional rules we can obtain easy to recycle designs.
•The basic rules (above DFA) are,
1.Use modules (consolidated parts) that can be removed and reused in other applications
2.Mark all materials for identification that cannot be sorted easily
3.Make parts easy to disassemble
4.Reduce materials and energy invested in the parts.
DI:13.4.1 Reduce Materials and Energy
•When we manufacture a product it requires energy to generate the raw materials, more energy to form them, and over the life of the product energy is used.
•Ideally the perfect product last forever, and never needs to be recycled. This can be attempted through good design practices.
•Other ways to reduce the total energy/materials in the product are,
-reduce the number of parts
-reduce the part size
-reduce the time to assemble
-eliminate redundant components
-use recycled materials where possible
-reduce scrap
-evaluate materials chosen for their environmental impact, and recyclability
-minimize waste in production processes
-packaging should be eliminated, or replace with reusable packaging
-when reliability is a problem, make the components easy to maintain and repair.
-avoid finishing operations that might contaminate materials
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• If you recycle your own products, there are potential economies of scale, and the approach to DFR will improve.
DI:13.4.2 Consolidated Parts
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•Auto wreckers commonly salvage good parts from an automobile before it is scrapped. This reduces the amount of material that must be reprocessed from raw state.
•These parts are self compact modules that,
1.can be removed and reinstalled in another machine
2.can be rebuilt easily, if at all
3.has a compact geometry with connectors
DI:13.4.3 Ease Of Disassembly
•One major reason not to recycle is the time required to separate materials.
•To make a product easy to disassemble you can,
1.use snap fits that can be undone or broken easily
2.mark the location of snap fits so that they can be separated quickly
3.reduce the fastener count
4.avoid threaded and permanent fasteners (eg glue)
5.reduce the number of components to reduce the number of steps in disassembly
6.assembly from top in layers so that parts can be picked off
7.avoid parts with mixed materials
DI:13.4.4 Recycling Markings
• For plastics there are six symbols commonly recognized,