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Revision as of 03:29, 8 February 2012

Group Information

24-441 Spring 2012, Group 10

Claire Castleman

Elisha Clayton

Michael Serebrennikov

Mathew Swisher

Vedant Saraf

Product: Razor Scooter

Executive Summary

A kick scooter is a simple human-powered vehicle, composed of a small platform to stand on and handle bars to hold onto and steer, used as a means of transportation over short distances. As a case study, our team is analyzing the Razor brand scooter, one of the most popular in the United States. The scooter will be disassembled in order to gain an understanding of how it is manufactured and put together. Competitor products will also be examined in order to understand various solutions the manufacturers face. An initial user study will be conducted to determine shortcomings in the overall design. The goal of the project is to come up with an innovation to make the scooter easier or safer to use, to make the construction simpler, or to change its purpose by adding a utility attachment.

Major Stakeholders

Manufacturing

Simple parts that can be mass produced
Small number of unique parts
Assembly with minimal effort
Fast assembly time
Environmental effect of materials used
Product re-usability

Shipping

Maximum compressibility
Low weight
Low volume
Reduce empty/wasted space
Durable enough to withstand damage with minimal padding

Retailers

Appealing colors to customers
Cheap product cost for maximal profit
Minimal store floor-space usage
Efficient packaging for minimal storage space

Potential Consumers and their concerns

Parents

Low cost
Reliable
Safe
Durable
Something their kids will want and think is cool

Kids

Fun
Cool
Light weight
Trick friendly

College Students

Portable
Collapsible
Light weight
Easy to carry/store
Energy efficient
Cheap
Durable

Product Details and Observations

Product Operation and Preliminary User Study

Potential Innovations

Bill of Materials

In order to make the BOM more comprehensible, it is split up into separate subassembly BOMs. Repeating components share the same part number across subassemblies.

Front Wheel Subassembly

Part No.	Part Name	Material	Quantity	Weight (oz)	Manufacturing Process
01	Washer	Steel	1	<0.1	Stamped
02	Screw	Steel	1	0.2	Purchased
03	Pin Nut	Steel	1	0.4	Purchased
04	Bearing	Steel	2	0.4	Purchased
05	Bushing	Steel	1	0.1	Extruded
06	Wheel	Urethane and polypropylene	1	3.4	Injection Molded

Shock and Wheel Attachment Subassembly

Part No.	Part Name	Material	Quantity	Weight (oz)	Manufacturing Process
07	Washer	Plastic	2	<0.1	Injection Molded
08	Disk	Aluminum	1	0.2	Stamped
09	Screw	Steel	1	0.2	Purchased
10	Pin Nut	Steel	1	0.6	Purchased
11	Washer	Metal	1	<0.1	Stamped
12	Shock	Rubber	1	1.4	Injection Molded
13	Wheel Bracket	Steel	1	4.4	Stamped and Bent
14	Suspension Bracket	Plastic	1	0.2	Injection Molded

Lower Tube Subassembly

Part No.	Part Name	Material	Quantity	Weight (oz)	Dimensions	Manufacturing Process
15	Threaded Tube	Chromium plated Steel	1	9.6		Extruded and Welded to a piece that was Stamped and Bent
16	Bearing	Steel	2	0.2		Purchased
17	Bearing Track	Steel	1	1.2	4.5cm OD, 2.5cm ID	Pressed and Machined
18	Nut	Steel	1	0.7	3.2cm OD, 2.6cm ID	Machined
19	Screw	Steel	1	0.3		Purchased
20	Collar	Aluminum	1	0.5		Machined

Collapsing Mechanism Subassembly

Part No.	Part Name	Material	Quantity	Function	Weight (oz)	Dimensions	Manufacturing Process
21	Cover	Plastic	2	Decorative Cover	0.4		Injection Molded
22	Screw	Steel	2		<0.1		Purchased
23	Containment Tube	Steel	1		10.3		Extruded and Machined piece Welded to an Extruded and Drawn piece
24	Screw	Steel	1		0.1	M3x8	Purchased
25	C-Clips		2		<0.1		Stamped
26	Pin	Steel	1	Locks on Frame	0.6		Purchased
27	Spring Tensioner		1		0.8		Extruded and Machined
28	Edge Protector	Plastic	1		0.1		Injection Molded
29	Guide	Plastic	2	Keeps Spring Tensioner from rotating	<0.1		Injection Molded
30	Spring	Steel	1		0.1		Bent
31	Lever	Steel	1	To initiate collapsing	0.2		Extruded and Machined
32	Torsional Spring	Steel	1	To return lever to lock position	<0.1		Bent
33	Tension Adjuster		1		0.3		Purchased
34	Pin	Steel	1		0.7		Purchased

Front Deck Subassembly

Part No.	Part Name	Material	Quantity	Weight (oz)	Manufacturing Process
35	Edge Protector	Plastic	1	0.2	Injection Molded
36	Screw	Steel	4	0.1	Purchased
37	Screw	Steel	4	0.1	Purchased
38	Locking Bracket	Steel	1	5.9	Machined and Bent
39	Underside Plate	Steel	1	2.2	Machined and Bent

Rear Wheel Subassembly

Part No.	Part Name	Material	Quantity	Function	Weight (oz)	Manufacturing Process
04	Bearing	Steel	2		0.4	Purchased
05	Bushing	Steel	1		0.1	Extruded
06	Wheel	Urethane and polypropylene	1		3.4	Injection Molded
40	Wheel Bracket	Plastic	2	To attach wheel	0.05	Injection Molded
41	Pin Nut	Steel	1		0.5	Purchased
42	Screw	Steel	1		0.2	Purchased
43	Wheelie Bar Bracket	Steel	2		1.0	Stamped
44	Screw	Steel	2		0.1	Purchased
45	Wheelie Bar	Aluminum	1		0.4	Extruded

Top Tube Subassembly

Part No.	Part Name	Material	Quantity	Function	Weight (oz)	Dimensions	Manufacturing Process	Picture
46	Bottom Tube	Steel	1		5.1		Extruded and Machined
47	Top Tube	Steel	1		4.8		Extruded, Welded, Machined

Handle Bar Subassembly

Part No.	Part Name	Material	Quantity	Function	Weight (oz)	Manufacturing Process
48	Tube	Steel	2		1.2	Extuded
49	Button Spring	Steel	2		<0.1	Bent
50	Button	Steel	2		<0.1
51	Grip	Foam Rubber	2		0.5	Expansion Molding
52	Side Cap	Plastic	2		0.5	Injection Molded
53	Cord	Elastic	1	Keep handle bars attached to frame	<0.1	Purchased

Top Tube Adjustment Subassembly

Part No.	Part Name	Material	Quantity	Weight (oz)	Dimensions	Manufacturing Process
54	Lever	Steel	1	0.4
55	Collar	Aluminum	1	0.5		Machined
56	Screw	Steel	1	0.4		Purchased
57	Screw	Steel	1	<0.1	M3x5	Purchased
58	Spring	Steel	1	<0.1		Bent
59	Bracket	Plastic	1	<0.1		Injection Molded
60	Bracket	Steel	1	<0.1
61	????			0.1

Frame and Brake Subassembly

Part No.	Part Name	Material	Quantity	Function	Weight (oz)	Manufacturing Process
62	Deck	Aluminum	1		13.5	Extruded
63	Brake	Steel	1		3.3	Bent
64	Nut	Steel	1		0.1	Purchased
65	Torsional Spring	Steel	1	For Brake	0.2	Bent
66	Rod	Steel	1		0.4	Purchased
67	Edge Protector	Plastic	1		0.1	Injection Molded

Design for Manufacturing and Assembly Analysis

Design for Manufacturing

When analyzing our competitor's product, the Razor scooter A2, we found a lot of room for improvement of its manufacturability. In order to minimize the part count, it would be possible to design a collapsing mechanism that uses fewer parts than the current design, which has 18 parts. The plastic covers especially are mostly for decoration, with a secondary purpose of preventing young children from sticking their fingers into the locking mechanism. Even so, they are not essential to the design of the collapsing subassembly, and so only add unnecessary steps to the manufacturing and assembly processes. Throughout the whole product, plastic parts were added instead of using metal finishing processes. While this was resulted in fewer finishing steps, it added steps both in manufacturing and assembly.

The Razor scooter we disassembled also showed opportunities to standardize components, commonize the product line, and standardize design features. A lot of the screws used as fasteners were the same size, but several differed by one size, and a few even switched from Imperial to Metric sizing. By unifying the size and length of screws used, the scooter could take better advantage of economies of scale and utilize fewer tools in the manufacturing process.

Another area for possible improvement with respect to design for manufacture is the creation of multifunctional parts. No parts of the scooter are currently multifunctional, but there is a definite opportunity for the creation of such parts in our redesign. For instance, designing a brake that doubled as a lock for the handlebars when the scooter is in its collapsed position could remove the hassle of the handlebars swinging about loosely when unlocked.

A final place where manufacturability of the scooter could be improved is in its secondary & finishing operations. Every single aluminum piece that is visible on the outside of the scooter has been polished, and a sandpaper sticker was glued onto the deck when it would have been much easier and probably as effective to extend the extruded ribs across the deck of the scooter to add friction.

Despite all these areas for improvement, there were many ways the current design had kept maufacturability in mind, which we will remember as we consider our redesign. Some of the locking mechanisms on the scooter had minimized their part counts to about 2 parts (for example, the handlebar locking mechanisms each consisted of a button and a spring). Similarly, the scooter had some fairly sleek and simple designs, like the braking mechanism which, while not 100% functional, also only consisted of about 4 parts. In terms of ease of fabrication, most of the scooter was made of aluminum, which is easy to manufacture (when the aluminum is recycled) and very easy to machine. Most parts that were not aluminum were plastic, and the few remaining parts were made of steel or rubber. The plastic parts were all colored black by color dyes added to the injection molding process.

Overall, there are a few good designs we will keep in mind during our redesign, but even more opportunities for improvement which we hope to take advantage of in the next phases of our design process.

Design for Assembly

Our product was fairly complicated to disassemble, and in our limited experience attempting to reassemble some of its subassemblies, we discovered much room for improvement in its design. First of all, there were a lot of components for such a small, simple device. Some of these were flashy add-ons for marketing and design purposes, such as the shocks and wheelie bar, but others were useless or not essential to the function of the device, such as the numerous plastic pieces used as covers to hide unfinished parts. As well as removing unnecessary components, another way to minimize the part count is to remove fasteners, and utilize snap fitting or other means of attachment. A lot of screws were used in this device, and as we've discussed, they were already a hindrance for a number of other reasons.

Another area that could be improved upon is the ease of handling of parts for human assembly. There are a lot of ambiguous parts, such as screws and levers, which can be very difficult to tell apart and could easily be unified for easy assembly. Some of these parts are also symmetrical, but only work in one orientation. These parts should be made obviously unsymmetrical, so that it is obvious in which orientation they should be attached to the product. The orientation in which parts are attached is not uniform, either. Many parts have fasteners on multiple sides, and most of these are attached horizontally instead of the ideal attachment direction of straight down. A final cause for concern is that many of the parts of this scooter are assembled inside its small-diameter tubes, which are tight and do not facilitate easy movement or sight.

The main way in which the scooter utilized good design for assembly was its use of subassemblies that can be assembled and tested separately or outsourced. The wheel subassemblies are almost certainly tested and purchased separately, and most other subassemblies, such as the telescoping tubes, brake assembly, and handlebar assembly, can easily be tested without the entire product.

There are many ways to improve the ease of assembly in this product, many of which we will probably explore in the next phases of our project.

Failure Mode and Effect Analysis

@@ Line 961: / Line 961: @@
 =Design for Manufacturing and Assembly Analysis=
-Design for Manufacturing Overview:
+==Design for Manufacturing==
 When analyzing our competitor's product, the Razor scooter A2, we found a lot of room for improvement of its manufacturability. In order to minimize the part count, it would be possible to design a collapsing mechanism that uses fewer parts than the current design, which has 18 parts. The plastic covers especially are mostly for decoration, with a secondary purpose of preventing young children from sticking their fingers into the locking mechanism. Even so, they are not essential to the design of the collapsing subassembly, and so only add unnecessary steps to the manufacturing and assembly processes. Throughout the whole product, plastic parts were added instead of using metal finishing processes. While this was resulted in fewer finishing steps, it added steps both in manufacturing and assembly.
@@ Line 976: / Line 976: @@
-Design for Assembly Overview:
+==Design for Assembly==
 Our product was fairly complicated to disassemble, and in our limited experience attempting to reassemble some of its subassemblies, we discovered much room for improvement in its design. First of all, there were a lot of components for such a small, simple device. Some of these were flashy add-ons for marketing and design purposes, such as the shocks and wheelie bar, but others were useless or not essential to the function of the device, such as the numerous plastic pieces used as covers to hide unfinished parts. As well as removing unnecessary components, another way to minimize the part count is to remove fasteners, and utilize snap fitting or other means of attachment. A lot of screws were used in this device, and as we've discussed, they were already a hindrance for a number of other reasons.

Scooter