The project involved the Design for Assembly (DFA) analysis of a paper shredder. The analysis was performed using Boothroyd and Dewhurst DFA method. Using the analysis the assembly time for paper shredder was estimated. The solid modeling of paper shredder was developed using Solidworks, it helped to understand the interaction of various components and possible optimization areas for the product. The DFA rules were used to redesign the paper shredder. After the redesign , the DFA method was again used to estimate the new assembly time for paper shredder. The optimization resulted in reduction of 256 seconds in the assembly time.
Design for Assembly (DFA) Analysis
The paper shredder was divided into 4 sub-assemblies. The first sub-assembly was for shredder body, which consisted of four plates (top, bottom, left side and right side plate) and 4 flanges holding them together. All these parts were joined by 15 pairs of screw, washer and nut. The cutter subassembly consisted of 2 cutter rods separated by a plastic separator. This subassembly also had 3 gear pairs bolted to a mounting plate. This subassembly was considered as a single component in DFA as its inability to break down into subsequent parts. Another subassembly was handle mechanism subassembly, consisting of metal base, Irwin-plastic top, shredder handle mounting and plastic wheel. Armature and rod sub-assembly was made of armature, rod, 3 mountings and one plastic base. Mounting served the purpose of aligning the rod, armature and plastic wheel. The plastic base was used to fix the armature mountings to gear mounting plate from cutter subassembly. Based on the DFA analysis, the estimated assembly time for paper shredder was 682 seconds.
CAD Rendering of a Paper Shredder Assembly
Redesign of Paper Shredder
During the Design for Assembly, it was observed that some features of the paper shredder could be the cause of increased assembly time. The most evident observation was heavy use of fasteners and various joining elements. Hence paper shredder was redesign using DFA rules and method to reduce the assembly time and cost. The design changes performed to the paper shredder assembly were:
During the Design for Assembly, it was observed that some features of the paper shredder could be the cause of increased assembly time. The most evident observation was heavy use of fasteners and various joining elements. Hence paper shredder was redesign using DFA rules and method to reduce the assembly time and cost. The design changes performed to the paper shredder assembly were:
The redesign eliminated the 58 components of paper shredder assembly. This also resulted in a savings of a 256 seconds in the assembly time which was 37% of the original assembly time.
Figure 1: Plastic wheel Original (Left) and Redesigned (Right)
Figure 2: Components of Shredder Handle Subassembly
Figure 3: Integrated Handle
Figure 4: Top Cutter Holding Plate and Flange
Figure 5: Integrated Top Cutter Holding Plate and Flange
Figure 6: Bottom Cutter Holding Plate and Flange
Figure 7: Integrated Bottom Cutter Holding Plate and Flange
Figure 8: Paper Shredder Assembly After Design Modifications
