Baby stroller
From DDL Wiki
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::c. Cost | ::c. Cost | ||
::d. Space constraints | ::d. Space constraints | ||
| - | 3. Manufacturers | + | :3. Manufacturers |
| - | a. Individual parts | + | ::a. Individual parts |
| - | i. Cost | + | :::i. Cost |
| - | ii. Speed | + | :::ii. Speed |
| - | iii. Quantity | + | :::iii. Quantity |
| - | b. Assembler | + | ::b. Assembler |
| - | i. Cost | + | :::i. Cost |
| - | ii. Speed | + | :::ii. Speed |
| - | iii. Labor | + | :::iii. Labor |
| - | iv. Shipping | + | :::iv. Shipping |
| - | 4. Stores | + | :4. Stores |
| - | a. Cost | + | ::a. Cost |
| - | b. Space | + | ::b. Space |
| - | c. Customer satisfaction | + | ::c. Customer satisfaction |
| + | |||
| + | ''' | ||
| + | == System Functions == | ||
| + | ''' | ||
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| + | The baby stroller has five main functions: transporting the baby forward and backwards, navigating turns, locking mechanism to reduce possibility of the stroller moving unintentionally, folding capability for ease of use, and most importantly keeping the baby securely fastened inside the stroller. Listed below is a detailed explanation of each of the functions. | ||
| + | |||
| + | :1. Forward and Backward Motion | ||
| + | ::a. Force applied to the handle which is transferred to the four wheels, which makes the stroller go forward or backward. The wheels are made of rubber, which makes it suitable for a variety of surfaces (like sidewalk, grass, tiles, etc…) that it might be used on. | ||
| + | :2. Turning | ||
| + | ::a. Front wheel is free to rotate when a moment is applied to the handle bar (from the centered position). FIGURE SHOWN | ||
| + | :3. Braking | ||
| + | ::a. Tab at the rear axle that can be activated which locks the back wheels and thus makes it harder for the stroller to go forward or backwards. Also the front wheels can be locked to limit the range of motion of the stroller (about 15 degrees). SHOW PICTURES | ||
| + | :4. Folding | ||
| + | ::a. By rotating HANDLE PIECE the entire stroller assembly can be folded for ease in transportation and storage. DESCRIBE DETAIL. FIGURE NEEDED. | ||
| + | :5. Keeping baby secure | ||
| + | ::a. 5 point safety harness which ensures that the baby is securely held in the stroller. PICTURE. | ||
| + | :6. Car seat integration | ||
| + | ::a. A car seat can be placed on the stroller and secured by SNAPPING DEVICE. This provides ease of transportation of the baby for the parents. | ||
Revision as of 12:42, 17 September 2008
Contents |
Usability study
This study looks at the different functions of the stroller and how the user achieves their goals. It will be broken down into different functions, and give a step by step analysis of different ways the user achieves the goals.
Putting a baby in the stroller/Removing baby from stroller
In order to insert a child into the stroller, the user first (1) ensures the stroller is stationary. Then the user can put the child by (A.2) unlatching the harness (Part Number), then (A.3) putting the child into the seat and then (A.4) latching the harness around the child.
Alternatively the user can insert a car set into the stroller. This requires the user to (B.2) put the car seat into the stroller seat and then (B.3) latch the car seat into the stroller by wrapping the car seat latch (Part Number) around the car seat, and fastening it.
In order to remove the baby, the step are simply performed in reverse, where you first (5) unlatch the harness or car seat latch and then (6) remove the child from the seat.
Folding the stroller
In order to fold the stroller, the user must first (1) ensure that the stroller is empty. Once that is done, the user can (A.2) pull on the white push knob (Part Number) on the handle assembly (Assembly Number). The user then (A.3) twists the handle assembly forward approximately 180 degrees. This unlocks the middle bar by separating the locking mechanism (Part Number). Then the user (A.4) pushes the handle bar down towards the floor. This often causes the stroller to fold at the locking mechanism and the wheels to slide towards the user quickly, so to combat this affect, the user can either (A.5.1) put their foot on the brake bar (Part Number) or (A.5.2) engage the braking mechanism before using this function. Alternatively, the user can (B.2) lift up on the handles of the locking mechanism (Part Number) in order to disengage the lock. This method brought about a problem in that these handles are within reach of the child who is in the stroller, and could be used by the child to their danger. We will discuss this point later in the report.
Moving the baby around
In order to move the baby around while in the stroller the user has many options. To push the stroller forward, the user simply (1) pushes forward on the handles.
In order to move the stroller around a corner, the user can either (2) supply a moment to the handle or (3) push down on the handle, lifting the front wheels of the stroller off of the ground, and then supply a moment, allowing the stroller to make sharper or more maneuverable turns.
A note is that the user should not push the stroller anywhere except the handle in order to control the stroller, nor should the user push the handle with excessive force or speed, as doing so results in the stroller becoming unstable and potentially tipping over.
Keeping the stroller stationary
In order to engage the locks of the stroller, the user (1) presses down on either the left or the right break (Part Number). Most users push this break with their foot, as it located on the break bar/rear wheel assembly.
How this assembly works is that a solid bar engages with a gear located on the wheel, which keep the wheel from rotating.
Also in order to lock the front wheels from turning, the user (1) pushes the front wheel locks (Part Number) upwards until it clicks. This stops the front wheels from turning, but not rotating.
Transporting stroller without baby
In order to transport the stroller without a child in it, the user first (1) folds the stroller. Then the user can (A1) carry it by one of the structural bars (Part Number), (B1) carry it by the plastic tray (Part Number), or (C1) by the handle (Part Number). Each method has been observed in user studies.
Major Stakeholders
There are four major stakeholders in the baby stroller product: baby, parents, manufacturers, and stores selling the baby stroller. The major needs for the users (baby and parents) are the safety and comfort of the child. The major need for the manufacturers and stores is the cost of the baby stroller. Listed below is a list of the major stakeholders and their needs.
- 1. Baby
- a. Safety
- b. Comfort
- 2. Parents
- a. Safety of the child
- b. Comfort – Ease of use and comfort of the child.
- c. Cost
- d. Space constraints
- 3. Manufacturers
- a. Individual parts
- i. Cost
- ii. Speed
- iii. Quantity
- b. Assembler
- i. Cost
- ii. Speed
- iii. Labor
- iv. Shipping
- a. Individual parts
- 4. Stores
- a. Cost
- b. Space
- c. Customer satisfaction
System Functions
The baby stroller has five main functions: transporting the baby forward and backwards, navigating turns, locking mechanism to reduce possibility of the stroller moving unintentionally, folding capability for ease of use, and most importantly keeping the baby securely fastened inside the stroller. Listed below is a detailed explanation of each of the functions.
- 1. Forward and Backward Motion
- a. Force applied to the handle which is transferred to the four wheels, which makes the stroller go forward or backward. The wheels are made of rubber, which makes it suitable for a variety of surfaces (like sidewalk, grass, tiles, etc…) that it might be used on.
- 2. Turning
- a. Front wheel is free to rotate when a moment is applied to the handle bar (from the centered position). FIGURE SHOWN
- 3. Braking
- a. Tab at the rear axle that can be activated which locks the back wheels and thus makes it harder for the stroller to go forward or backwards. Also the front wheels can be locked to limit the range of motion of the stroller (about 15 degrees). SHOW PICTURES
- 4. Folding
- a. By rotating HANDLE PIECE the entire stroller assembly can be folded for ease in transportation and storage. DESCRIBE DETAIL. FIGURE NEEDED.
- 5. Keeping baby secure
- a. 5 point safety harness which ensures that the baby is securely held in the stroller. PICTURE.
- 6. Car seat integration
- a. A car seat can be placed on the stroller and secured by SNAPPING DEVICE. This provides ease of transportation of the baby for the parents.
Design for Manufacturing and Assembly (DFMA)
Design for Manufacturing and Assembly Analysis (DFMA)
To make a stroller, first the individual parts are manufactured. Then, certain parts are assembled together into separate subassemblies. Finally, the consumer brings home a box full of subassemblies along with an instruction book and proceeds to assemble the stroller to its usable state. In this section we will analyze each of these stages separately.
Design for Manufacturing
The stroller has a metal structure for support of other materials. This structure is formed by individually bent hollow tubes with holes intended for later assembling the bars together by riveting. From general inspection, because the part was fairly light, we can be accurately assume the part is made of aluminum. The bars are painted providing a very smooth texture over the rustic aluminum feel and do not have any sharp edges. In addition, it is worthy to note that there were no dents in the metal tubes and they were very circular, creating no safety or quality concerns.
Another component of the stroller is the fabric that is fascined onto the metal structure. This fabric is rather strong and well stitched together. It can withstand very forceful tugs.
The rest of the stroller is made of plastic components; most likely ABS. ABS is very stiff and can be molded easily into many different shapes. This flexibility along with other desirable properties this material provides, and its cheap price makes it the logical choice of material for the stroller application.
The parts are designed very well to complements the material. The walls of all the components are designed with uniform thickness, thus avoiding sinks in the part and other manufacturing difficulties, resulting in an aesthetically pleasing and touch appealing surface finish. It is also worthy to note that although from a quick glance, the front and back wheels differ. However, when one looks closer, the wheels in the front are essentially composed from two sets of the wheels from the back. This usage helps decrease cost because it effectively puts to use manufacturing for scale.
Another advantage of using plastic is that it can be molded into various shapes that have the ability to be very detailed. This makes it practical to make many safety locks for the parts on the stroller. For instance, the locks for the wheels and the snap on trays are great examples of how the material was molded.
In addition, for the application of the product, the designers were very thoughtful in adding many fillets and rounding all the edges making it safe for interactions with children.
Nevertheless, plastic is not perfect. In making the injection mode for the mass produced part, designers have to keep in mind, shrinkage of the material. As can be seen in the figure below (Figure ___), when the parts are looked at individually, they seem very well made and little defects can be seen. However, when they are assembled, the molds were not created perfectly to account for the amount of shrinkage and some parts do not mate perfectly. But these defects and tolerances are built into the design. The overhangs have rounded corners, thus they will not be dangerous. The miss alignment gap is enclosed on the edges, thus it is hard to get one’s hangs pinched while in the handle is in its closed position.
From our analysis, we have concluded that the individually manufactured parts are very well made and are appropriate for the application of interaction with children. The injected or blow molded plastic parts have designs that consider tolerances and the properties of the material.
Design for Assembly
All the metal tubes fit together very well. They are secured together with rivets and will not loosen up easily. In addition, some wires are slipped through the tubes for the function of collapsing the stroller. Then the metal is secured with fabric.
Before the fabric is ready to be fascined on the metal frame, different materials are stitched together and metal buttons are added nylon strips. This makes later assembly onto the frame easier when the strip is wrapped around the metal bars and is secured. Another way that the fabric is secured is by directly screwing them into the metal tubes that had pre-drilled holes in them, as can be seen in figure ____ . In this way, the fabric is very securely attached to the main support and the additional plastic serves as a good way to distribute the pressure onto a larger area adding an additional layer of safety when a child is placed in the stroller. One drawback of this method is that they have to be manually secured because they need to be pulled over and drawn around the metal before they can be screwed in. This also adds variability because there are no predrilled holes or any visible indications as to where the screws should be placed. But this fact also makes it easy for assembly.
After the fabric and padding are added, additional plastic support are placed on. Some parts only add to the aesthetic appeal, such as part#. Others are to hold the subassemblies in place for transport in box to the customers such as part#. While a majority of the plastic adds additional futures for the stroller, such as part#, added to give a place for the parent to place bottles or other things.
All of these parts are designed for easy assembly and have a very logical order to it. There are Things fit together very well and does not require the assembly worker to get into awkward positions or use excessive force repeatedly. This is very important for this high volume product. It is also worthy to note that the designers tried to keep the amount of varying parts to a minimum. For instance, the front and back wheels use the same part, except the front wheels have an additional part to link two wheels together. This not only saves cost for manufacturing the part by not requiring an additional mold. It also decrease the amount of stock needed to be kept and avoids mistakes during assembly by mixing up the front and back wheels on accident.
After most of the parts are assembled, they are packed up in boxes and shipped off to be sold to customers.
Design for Customer Final Assembly
Because of the nature of the product, it is required that customers assemble certain parts themselves. When consumers purchase the stroller, they are presented with eight parts, as can be seen in figure#; one main assembly, front and back wheels, wheel lock, front tray and foot rest for the child. We noted that there were no screws or small metal parts that needed to be involved in the final assembly process with the exception of two end caps for the back wheels. Also, no tools were needed with the exception of a hammer and a pair of scissors to cut a tie that secured the main part in its closed position.
The final assembly was relatively simple. The parts were mainly snapped onto each other. When alignment of the parts was necessary, there were guides built into the design of the product, such as ribs that suck out, to ensure the right alignment. One example can be seen in figure#.
We did not have any difficulties with the assembly process. However, the foot reset for the child was hard to snap onto the metal frame. Nevertheless, we could fully assembly the stroller within ten minutes. In addition, little material remains after the assembly is complete. As can be seen in figure#, only some cardboard pieces, a tie, some caps that were on the ends of the metal rod that stuck out from the back wheel brakes, a plastic piece to hold the main subassembly in the closed position while it was in the box, a hammer used to secure the cap onto the back wheel, and the instruction, were left from the assembly.
Overall, this product was designed very well with many aspects considered. As noted in the detailed analyzes above, there were variations and tolerances that were left. It is noticeable that the designer kept the involved parties for this product in mind during the design. Parts were consolidated for ease of assembly. In addition, the designer included enough tolerances and flexibility in the design to avoid necessary tight precisions that can be tedious for the factory assembler and the customer. The material was well chosen to allow the designs of the parts to be well rounded, no sharp edges, and pleasing to the senses.
