Rolling suitcase

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Revision as of 13:58, 7 February 2011

Executive Summary

Product Stakeholders

Product Use Study

Product Mechanical Function

Bill of Materials

Main Components

There are only about 4 different types of cloth used in the suitcase, but they make up approximately 200 components. Some of these scraps of cloth are only a square inch or two, while others are as large as 5 or 6 square feet. Since there are only a few different types of cloth, each cloth has been given a name and components are listed with the type of cloth used and the size of cloth used. The suitcase also only has 6 different types of seams where these pieces of cloth are sown together. Examples of each are shown below the bill of materials. For simplicity, most of the individual pieces of cloth have been omitted.

Main Compartment
Part Number	Name	QTY	Weight (g)	Function	Material	Manufacturing Process	Image
001	Interior Bottom Lining	1	69	Presentable appearance for main compartment. Hides structural components.	Cloth	woven
001	Interior Bottom Padding	1	21	Cushioning for main compartment	Foam	??
001	Interior Top Lining	1	79	Function	Cloth	woven
001	Metal Support Frame	1	457	Rigid Structural Frame	Steel	Bent
001	Support Frame Cover	1	46	Protects other components from sharp edges of metal support frame.	vinyl	??
001	Plastic Support Frame	1	447	Rigid Structure for suitcase	plastic	bent
001	Edge support wire - side	2	26	Rigid support for seam	steel	extruded
001	Edge support wire - bottom	1	12	Rigid support for seam	steel	extruded
001	Buckle Assembly	1	6	Function	Plastic	Injection Molded
001	Buckle Straps	2	6	Function	Cloth	woven
Handles
Part Number	Name	QTY	Weight (g)	Function	Material	Manufacturing Process	Image
001	Handle stablizing piece	2	52	No function	Synthetic leather	??
Cloth Types
Part Number	Name	QTY	Weight (g)	Function	Material	Manufacturing Process	Image
001	Exterior Fabric	area	??	Heavy duty fabric resistant to tears	Woven something	Woven
001	Interior Fabric	area	??	Light fabric to line interior of suitcase	Woven something	Woven
001	Vinyl Cloth	area	??	No function	Vinyl	Who knows?
001	Rubber Piping	area	??	adds support to edges where metal is not used	rubber	Molded
001	Textured Piping	area	??	Adds rigidity to corners	??	??

Design for Manufacturing and Assembly

In our analysis of the competitor product, we identified several interesting choices made by the competitor in regards to the design for manufacturing and assembly. While some of the choices on the part of the competitor were useful for cheap and efficient manufacturing and assembly, there were a few choices that we feel can be improved upon for more economical product manufacturing and assembly.

Manufacturing

The biggest success of the competitor’s design for manufacturing was the relative standardization of design features. One of the most prominent examples of this standardization is evident in the corners of the bag. All corners on the bag, including that of the main storage compartment as well as the exterior pockets, were the same radius. This means that the same manufacturing process can be used for the construction of every corner. Another example of standardization of design features is that some parts looked as if they could be interchanged between various models of suitcases. For example, the wheelbase of the suitcase could be assembled for three different widths of suitcase. This allows for larger manufacturing quantities of injection molded parts, thus leading to a lower cost per part. Another notable thing about the manufacturing decisions of the competitor is the choice of material. All of the materials chosen for the product were fairly easy to work with. These include plastic for injection molding and metal for extrusion, which are both inexpensive materials to manufacture with in large quantities. We found a number of competitor manufacturing choices that can be improved upon in order to simplify the manufacturing process. The first major complaint we had about the competitor product is that they used a huge number of different parts. There were a hundred different shapes and kinds of fabric used in the construction of the bag. We feel that many of these layers served little purpose and could be eliminated or replaced with one layer of higher quality material. Additionally, the competitor used a very large variety of different fasteners throughout the product. Depending on how the competitor laid out the assembly process, all of these different fasteners could cause confusion. We hope to eliminate the majority of these fasteners and replace them with parts that snap or slide together.

Assembly

One of the best choices that the competitor made for the assembly of the product was the use of subassemblies. Many of the external pockets on the bag, as well as some of the internal mechanical components of the luggage, were probably assembled separately and then inserted and attached to the final bag. This allows for workers that can be specialized for one assembly function, thus streamlining the assembly process. Another decision made by the competitor that specifically benefits assembly is the use of fastener slots on injection molded parts. These slots are used in the place of holes for attaching two parts together with fasteners. They aid in assembly because they allow some tolerance in the spacing of parts. This saves time used for alignment in the assembly process. Another thing that the competitor designed into their product to help with alignment in assembly was self-centering mechanisms for many of the internal mechanical parts of the bag. For example, the wheelbase for the bag was a subassembly that was assembled to the correct width of the bag, so that it could be inserted into the bag without the need for additional measurement. The bag also features a chamfered opening in this wheel base, which the telescoping handle fits into. Both the wheelbase and these chamfered openings speed up the assembly process. Although there was clearly thought put into design for assembly of the competitor product, there were also clearly areas for improvement. One of the largest problems we identified was the huge quantity of different parts. Having so many parts to assemble quickly becomes costly and cumbersome. Additionally, because of the complexity involved in so many parts, the assembly of the non-mechanical parts is by no means fool-proof. There is a large potential for error in the assembly of the internal clothes holding features, such as the layers of padding, the pockets, and the straps. This complexity could lead to waste, which only increases the costs of manufacturing and assembly. We feel that many of these internal features could be simplified or eliminated without a noticeable difference in usability.

Failure Mode and Effect Analysis

In our analysis of the competitor product, we identified several different potential failure modes in using the competitor product. These are enumerated in the table below. This uses the FMEA method described in Section 14.5 of Dieter and Schmidt’s Engineering Design. Note that we felt that none of the cases were very severe. There is likely a very low chance of injury from using this product.

Failure Modes and Effects Analysis - Rolling Luggage
Item & Function	Failure Mode	Effects of Failure	S	Causes of Failure	O	Design Controls	D	RPN	Recommended Actions
001	Interior Bottom Lining	1	69	Presentable appearance for main compartment. Hides structural components.	Cloth	woven	Design for Environment Group Dynamic Team Leader: Mallory Elbert Safety Expert: Fritz Langford Manufacturing Expert: Eric Lawson Environmental Expert: David Stonestrom As a team, we have all worked with one another (though not all at the same time) on various other projects, so we already have a good sense of how everyone else thinks and works. We have allotted two weekly meeting times to use as necessary, but because we know eachother outside of the scope of the course, it has been easy to schedule additional time as necessary. References Dieter, G. and L. Schmidt, Engineering Design, 4th edition, McGraw-Hill, 2009, pages 707-712. Carnegie Mellon University Green Design Institute. (2008) Economic Input-Output Life Cycle Assessment (EIO-LCA), US 1997 Industry Benchmark model [Internet], Available from:<http://www.eiolca.net> Accessed 7 January, 2011.