Product Analysis/Gate 3

Gate 3

Purpose

In gate 3, a detailed analysis of the product can now be completed, as the product is fully disassembled. There are several pieces of information in this technical report. First, there is a project management section that comments on how well the group has been working together thus far. There is a component summary that lists all the components of our product. Next, there is a detailed product analysis on seven key components. Also included in the report are a couple pictures of components that have been solid modeled, a component that could benefit from engineering analysis, and three possible design revisions that could improve the product.

Project Management: Coordination Review

At this point in the project, the group is working well together. Our plan has worked out well, as we have been able to meet once a week, and twice a week before the gates are due. This allows us to get the gates done in a quality fashion and also gives allows extra time if needed. We have continued to meet in Greiner Hall, as this seems to be a convenient location. All members of our group have been contributing an even amount, so there are no problems with an individual member as well.

The biggest challenges we have had to overcome so far have been dealing with wiki and learning the formatting of it. It has been a group effort to figure everything out, ranging from how to effectively place pictures in the wiki, to how to set up an organized table. However, each week we all learn a little more and soon we should be able to do everything we want to in the wiki.

More specifically for this gate, the biggest challenge was deciding on which components to go further in depth with, and it took the group quite a while to pick the seven components. After some debate though, we all were able to come to an agreement, and the gate was able to progress forward. The team also had a little bit of trouble with this gate as no one had used a solid modeling program in over a year. Ray took up the challenge to learning the program, and was able to successfully model a couple key components.

Looking into the future, the biggest challenge that lies ahead is going to be actually reassembling the gun. It is going to require a lot of effort, as there were many, many screws and several small plastic pieces. However, with the good notes we took during the disassembly of the project, it should hopefully be done in a reasonable time frame.

Product Archeology: Product Evaluation

Component Summary

Part	Function	Material	Manufacturing Process	Picture
Battery Cover	To protect the batteries, keep them from falling out of the battery pack	Plastic	Injection Molded
Barrel Assembly	For aesthetic purposes, make the gun look realistic	Plastic, Rubber Tips	Barrel Pieces Extruded,Blue Supports Injection Molded, (Held together by strong epoxy)
Orange Rubber Ring	To cover the hard plastic end of the barrel	Rubber	Injection
Barrel Gear	To help gear the motor to drive the rotating barrel assembly	Plastic	Injection Molding
White Washers/Wheels (4)	To space the Barrel Gear away from its base and to help the barrels rotate more smoothly around the firing barrel	Plastic	Extruded
Sounds Maker	For auditory purposes, make it sound realistic	Plastic	Extruded then Machined (drilling, cutting)
Firing Barrel	Firing the dart through	Plastic	Extruded, Injection Molded
Ammo Box	Hold the ammo (darts)	Plastic	Injection Molded
Yellow Handle (2)	Use to hold the gun while in use	Plastic	Injection Molded
Ammo Cover Shell	Hold in the internal components of the ammo cover	Plastic	Injection Molded
Ammo Cover Hinge	To sense whether the top is closed or not	Plastic/Metal	Injection Molded/Drawn
Ammo Belt Tensioner	To keep tension in the ammo belt	Plastic	Injection Molded
Black Handle (2)	To hold the gun, hold power switch and trigger	Plastic	Injection Molded
Blue Outer Shell (2)	To hold all of the internal components of the gun	Plastic	Injection Molded
Orange Handle (2)	To hold the gun	Plastic	Injection Molded
Ammo Loading Gear Box/Motor Assembly	To rotate the ammo feeder to pull the ammo belt around	Plastic Shell and Gears (Metal motor inside)	Gears and shell made by injection molding
Trigger	User Input	Plastic	Injection Molded
Trigger Mechanism ( Long Blue Piece)	To connect the trigger piece to other mechanisms, translate forces	Plastic	Injection Molded
Trigger Piece	Translate Forces	Plastic	Injection Molded
Trigger Piece	Translate Forces	Plastic	Injection Molded
Trigger Piece, Dart Pusher	Push the dart out of the ammo belt into the firing mechanism	Plastic	Injection Molded
Ammo Belt Feeder	To pull the ammo belt out of the ammo box and into position for the dart to be pushed into the firing mechanism	Plastic	Injection Molded
Black Support Bar	To provide a location to insert screws to hold other components, support	Plastic	Injection Molded
Battery Pack	To hold the batteries	Plastic	Injection Molded
Ammo Box Holder	Movable lever that when pushed would release the ammo box	Plastic	Injection Molded
Barrel Rotating Gear Box/Motor Assembly	To make the barrels spin around giving the gun its realistic look	Plastic Shell and Gears. (metal motor inside)	Shell and Gears made via injection molding
Firing Motors	To propel/fire the darts	Wheels made from Plastic, metal motor	Wheels were injection molded
Power Switch	To turn the gun on and off	Plastic	Injection Molded

Product Analysis

The following components are all very important to the product and all required a lot of design work in order for the product to be successful. We have looked at many different factors regarding these products. We choose the following seven components because they were the most important components, and all required different kinds of analysis.

Firing Wheels

Component Function

• The firing wheels purpose is to project a dart at an intended target. Without this component this particular model Nerf gun would not be able to project a dart. The firing motors power the wheels which enable spinning to occur at a fast velocity, so when the dart comes into contact with the two wheels the dart is projected.
• This component does not perform multiple functions, its sole purpose is to fire the dart
• One flow that is associated with this component is mechanical flow. Mechanical energy spins the disks, once contact is made between the disk and the dart the force, (kinetic energy) transfers from the disks to the dart, thus giving the dart kinetic energy and firing it.
• This is an internal component and does not experience any outside elements from the environment

Component Form

• Circular Wheels
  • Radius=3.4cm
  • Width=1.2cm
• This part is axially-symmetric as it is a round wheel
• This is a primarily two dimensional piece
• This component is made out of plastic
• An economical factor in the decision to use plastic is that plastic is the cheapest and efficient material to use for a toy designed for children.
• The part was made via injection molding. Evidence to support this are visible riser marks.
• With this process there would be a high initial cost, but on a large production scale, injection molding is the most economical process when mass producing this component such as this. One global factor is that this part does not require skilled labor to operate, therefore increasing the availability of a work force capable of producing the part.
• The shape and function of this component is not very complex, it has a simple geometry. However the energy interactions taking place in this component makes it more complex than the just a disk spinning about a fixed point.

Ammo Belt Feeder

Component Function

• The belt feeders function is to rotate about its axis, as it rotates it pulls the ammo belt up out of the ammo box and aligns the dart in the belt with the firing barrel
• Other than moving the dart into position the belt feeder does not serve any other functions

Component Form

• Circular patter
  • Radius=4.2cm
• Groove
  • Length (tip-to-tip)=1.7cm
  • Groove height=1.2cm
  • Thickness =.3cm
• This part has a symmetric patter rotated in a circular pattern around a single center point.
• This part is primarily three dimensional
• Without its particular groves around the ammo feeder, its main purpose, to feed the ammo belt would be rather difficult. It is the grooves that actually makes contact with the belt and pulls it through.
• This part was made from plastic.
• Plastic is cheap and to an extent durable, so for economic factors this material would be the best choice when the intended use for this product is for young children.
• Evidence on the piece, riser marks, suggests that it was made via injection molding
• The geometry of the component most likely impacted the decision to use this method. The only other method in which this parts geometry could be achieved is by machining, taking a block of plastic and removing the undesired material. This is not the best idea for a piece like this because machining is a much longer and expensive process. Injection molding is a better choice because although it has a high up front cost if the part is to be mass produced it will be more economical in the long run. Injection molding also does not leave any waste material that would be associated with machining. Injection molding also does not required skilled workers that machining might and thus makes a work force easier to find.
• Due to the unique design of groves around the ammo feeder, this component becomes complex on a scale of manufacturing this part. Different from other possibly designs for an ammo feeder, this component is better off only using the process of injection molding for time constraints.

Firing Barrel

Component Function:

• The Barrel's purpose is to help guide and provide accuracy to the projection of bullet. The firing barrel does not serve multiple functions.

Component Form:

• This component has a Cylindrical Shape.
• The Firing Barrel has an axis of symmetry and is three dimensional.
  • Dimension:
    • Radius: 3.6 cm
    • Length: 24 cm
• The components shape helps prevent environmental factors such as wind, by allowing the dart not to be exposed to this element for (x) more seconds than that of a smaller firing Barrel. The components shape helps the projection of the dart.
• The firing barrel is made of plastic.
• For societal reasons such as safety, a direct design influence to this part would be the color of the firing barrel being orange, which distinguishes this being a toy gun. Being made of a cheap plastic lowers material cost which is also influenced by economic factors.

Manufacturing Methods:

• Due to the components constant flow and uniform shape, it gives evidence that extrusion was the method chosen. Also there was no presence of riser marks or parting lines.
• The choice of plastic making up the firing barrel did not impact the method of manufacturing.
• However since this component is a cylindrical shape, extrusion would be the best and most efficient way to produce this component on a time basis.
• On a global scale this part does not require a skilled labor to manufacture, therefore this component can be produced anywhere. Economically the method of extrusion may cost the same for the process of injection molding, but extrusion allows thin geometries to be formed, and will be cost efficient in the long run.
• The firing barrel is not very complex on any levels, its geometry is simple and only interacts with the bullet being passed through it.

Push Rod

Component Function:

• As the bullets are revolved around the belt feeder, the push rod ejects each bullet out of the ammo belt and into the firing wheels which will then project the dart.

Component Form:

• The push rods overall shape forms an (s) shape, but the main part that makes contact with each dart is that of a cylindrical shape. The entire shape of the push rod is three dimensional.
• Dimensions:
  • Total length 11 cm
  • Height 4.6 cm
  • Rod shape length 7.3 cm
• This component needs to be long enough to push the dart a distance to reach the firing wheels, therefore the long cylindrical part of the push rod accounts for the shape coupled to the function it performs.
• This component is made of plastic.
• For safety reasons the majority of the push rod is hidden, and when needed moves towards the bullet.

Manufacturing Method:

• Injection molding was used as the method of manufacturing for this component. Evidence of riser marks on this component support our claim.
• The shape did not impact the method selected.
• Having injection molding as the method of manufacturing allows for global production of this component since this method doesn't require a skilled operator. Economic concerns are low when it comes to this method of manufacturing since injection molding provides low long term cost with mass production.

Component Complexity:

• This component has an important function in which it feeds the darts into the firing wheels. Its interaction with the other components is key in that if this action is delayed or two fast, then the amount of bullets per min would be thrown off, which is a major seller for this gun.

Handle

Component Function

• The function for the handle is to provided stability for the user when interacting with the gun. The handle does not help to perform multiple functions, instead it serves as one purpose.

Component Form

• Has a length of 13.5 cm
• Height of 10 cm to the top of the arc.
• Radius 3.0 cm
• The component is made of plastic.
• From an economical stand point, for the handle on a Nerf gun there is no need for anything stronger than plastic to make up this component. Looking at the economic influence on the handle, there will be less money spent on a plastic material then any other sturdy material. Looking at this components function from a societal standpoint, knowing that there is an extra means of carrying this gun increase's the amount of children able to play with this model.

Manufacturing Methods:

• Injection Molding was the method used for this component. The appearance of riser marks on the handle support the claim of injection molding.
• The shape and material choice did not really affect the choice of manufacturing.
• Having this method of manufacturing allows production to take place globally since it doesn't require skilled operators to manufacture this component. Since this Nerf Gun is being mass produced the economic cost of injection molding will be cost effective in the long run.

Outer Shell

Component Function:

• This component is a key component in that it keeps all the internal components in place. The outer shell hides all of the potential harmful components to children while trying to resemble as close to a real gun within safety specs. The outer shell of the gun must be able to withstand environmental factors such as rain, wind, and be able to withstand common damage that comes with young children. (Scratching, dropping, etc)

Component Shape:

• The general shape of the outer shell can be closely related to that of a rectangle and is three dimensional.
• Dimensions:
  • Length 16.5 in
  • Width 7.0 in
  • Height 6.5
• The shape is designed so that it can give a close representation, within safety requirements, to what a real gun would look like. Its size and shape also performs the task to hold every internal component, so that each component can work properly.
• The outer shell of the gun is made of plastic.
• For societal reasons, plastic would be the best choice for this component since the intended target for this product is young children. Having a young child run around with a metal shell would be dangerous and require more strength. Economically, using plastic vs. a form of metal would be cheaper in production cost.
• This component has aesthetic properties such as decals and bright colors. The reasoning behind this design is for safety constraints to show that this is a toy, not real gun. Aesthetics are added to attract children as well. Colors consist of bright orange, blue, yellow and black to show its a toy gun.

Manufacturing Methods:

• From the presence of injection marks, the process of injection molding was the method used for this component.
• The shape and material did not impact this method selected.
• Wanting this particular model to sell globally, having injection molding not requiring a skilled operator helps this companies chances. **Injection molding from an economic standpoint will be the most cost efficient in long term costs.

Component Complexity:

• The component is only complex on a scale design for this model gun. It has no complex interactions besides being able to cover all the internal components. Its design is complex for this particular model but its function is no different than a different model Nerf gun.

Trigger Spring

Component Function:

• The trigger spring enables the trigger to move in, firing the bullets, or back out which stops firing.
• The flows withing the spring are potential and kinetic energy transfers. The trigger spring is also key function which acts withing the trigger system.

Component Form:

• The shape of the trigger spring is a helix.
• Dimensions for the spring:
  • Length stationary 1.0 cm
  • Length elongated is 4.0 cm
• The springs shape allows a tensile force to act on it which is needed for the trigger system to compress on its own once an outside force is removed from the system.
• The trigger spring is made of metal.
• On a small scale, for the cost of this trigger spring would be cheap due to the small amount of material used to produce this spring. This spring can be produced globally since its a standard spring.

Manufacturing Method:

• Drawing was the manufacturing method used to produce this component. The trigger spring is made of wire which is an example of drawing.
• The material choice for this component did impact the method used for manufacturing.
• The process involved in manufacturing this component does not require a skilled operate due to the use of machinery. Therefore this does not make this a societal concern to the workers.

Component Complexity:

• This component is not a complex component on its own. However since the trigger spring is what operates the trigger system, it becomes a complex component by the interaction with other components.

Solid Modeled Assembly

Parts
This Piece is the lower half of the gear box	This is the motor that drove the gears. The output shaft has a worm gear on it	This gear is a 36 tooth Gear	This gear is a compound gear with 24 teeth and 10 teeth	This gear is a compound gear with 24 teeth and 10 teeth	This is the axle was used 3 times for the gears to revolve around

• The color of the gears was changed in the 3D drawings to make it easier to see the gears

Assembly Views

Solid Model

For our solid model assembly we choose to construct the gearbox of the ammo belt. The torque is transferred from the motor through the worm gear, and then through a system of gears, which control the speed and torque. Finally the largest of the gears exports the torque to another component out the bottom. The gears were well lubricated to prevent friction.

In the Autodesk Inventor drawing I choose to color each gear a different color to accent the connections in the system. I choose Autodesk because I’ve had 6+ years of experience with the program dating back to early highschool.

Engineering Analysis

Arguably the most important function of any gun is the firing method. Our product is no exception to the rule, and performing an engineering analysis on the firing motors to look at this function would have been very important in the design and testing stages of the product. The creators of the product would want to make sure that this function is as optimized as possible.

In our product, the dart is fired by an electric motor. The motor draws its power from the batteries also located in the gun. The motor converts this electric energy into mechanical energy by spinning two shafts that are connected to two smooth wheels. These two wheels each have about a diameter of about 1.25 inches. They are separated by about .5 inches. When the trigger is pulled down, a signal is sent to the motors through wires to start spinning. Darts are then pushed between the two wheels and the mechanical energy transfers to the darts in the form of kinetic energy and the gun dart fires forward.

In order to complete an engineering analysis of the firing motors, and look at how well the gun fires, a number of equations must be known and looked at. These equations would help produce solid numbers that can be compared. They also allow the firing functions to be compared to other guns, and so a number of fairly simple equations would be very helpful for this engineering analysis. The equations as follows would all be very important:

Equation	Mathematical Model	Description of Equation
Efficiency of Motor	Efficiency = Work Out/Electric Work In	This is one of the first equations an engineer would look at, as the firing process starts with the motor. Engineers would be able to figure out how much electrical work would be input from the batteries, and from there they would be be able to find the work out. Motor efficiency would prove to be a key decision, as the gun will use less power to fire at the same rate if the motor is more efficient, but this would come with some trade-offs. These include that the motor might be more expensive or the size of the motor might be different.
Kinetic Energy	Kinetic Energy = (1/2)*(mass)*(velocity)^2	Kinetic Equation is another equation that can help give the gun some solid data. The kinetic energy comes from the spinning wheels and is transfered to the darts as they pass through the two wheels. The kinetic energy equation can potentially be used to find the initial velocity of the darts, as well as used to find the work of the system. Friction could be looked here as well, as some energy would be lost to it.
Work	Work = (Force)*(Distance)	Work is a very basic equation that can help engineers find out the force that is applied to the darts. This could potentially be very helpful in analysis that is looking at how fast the darts shoot out or how far the travel.
Force	Force = (Mass)*(Acceleration)	Newton's second law is one of the most useful equations for all of engineering anaylsis. The mass of the darts is known, and either the force or acceleration can be calculated depending on what is being looked at. The equation can be used to look at how fast the dart shoots right when it fires and how fast it is still moving when it is about to hit the ground. It could also be useful in finding the distance the darts travel, a very common test for most toy guns. Also, looking at the force applied to the dart would be useful in making sure the darts do not cause a safety hazard.
Velocity	Velocity = (Distance)/(Time)	This equation would be very useful, as it directly finds the distance the darts travel. This is a very common measure of performace for the gun.

The engineering analysis would be a hybrid method of investigation between first principle models and empirical models. Many of the known physics equations would apply to the firing motors, but many tests would have to be created to fully test the motor and determine the overall factors of the firing function. There are many tests that could be performed to complete an engineering analysis of the firing motors. These tests would measure several performance factors that would determine if the firing function was up to standard.

One test that would be useful would be measuring the distance the darts travel when fired. This is one of the standards that a lot of people would look at before buying the gun, and it would be a major indicator if the motor was up to standard. People look at the size of our product and think that it should fire a long distance. The gun would have to fire at least a set distance for it to be a viable product. In our products specific case, the darts will fire about 30 feet. This is actually pretty far for a “nerf” gun.

Another test that would be very important to the engineering analysis would be looking at the efficiency of the motor, and testing how much work it produces per amount of electrical energy. This would be a very important test and would look at how long the batteries actually last in the gun. This would have important economic and environmental implications. If the motor is not very efficient, the user will need to change batteries much more often, as well having to find a way to dispose of the batteries. However, if the motor is much more efficient, it will cost a lot more up front for the consumer to buy. A balance is needed to find the proper motor efficiency.

Yet another test would be figuring out the velocity of the darts as it shoots. This could be combined with the distance test as well. In order to perform this test, the testers would fire the gun from the same angle for a large sample size. The distance could be measured directly, and if the time is kept for how long the dart is in the air, the velocity can easily be calculated. This basic test would determine how fast the darts shoot and also if they could potentially be dangerous. Also, knowing the velocity allows the engineers to calculate other factors such as acceleration and force.

These are some of the major tests that could be applied to the firing motors of the gun. There are several other tests that could be performed as well, such as an accuracy test, the friction of the wheels on the dart, how far apart the wheels should be apart, how fast the wheels themselves should spin, etc...

In designing this gun and performing an engineering analysis of the firing motors, balance of all the important factors should be the main focus. The gun should perform as well as possible, but at a relatively cheap cost. Most consumers want a gun that is fun to use and performs well, but they will not pay a steep price for something as trivial as a gun. It is important to keep cost low throughout the entire process. Also, considering how the parts are made is important to this cause as well, because a big motor might require more expensive manufacturing techniques.

This is the basic way an engineer would go on about doing an analysis of the firing function of the gun.

Design Revisions

Dart:

The dart, at the moment, is made up of a Styrofoam material with a rubber tip on the top to make it more solid. We suggest that the Styrofoam be replaced by a similar biodegradable material. Anyone who has ever played with a dart firing gun of any kind knows how easy it is to lose the darts either around the house or if you are playing outside. Styrofoam takes over a million years to decompose and is a hazard to the environment. Therefor if we use a material, such as the one that scientists at Case Western Reserve University in Colorado discovered made of mostly milk protein and clay. This new material is biodegradable and decomposes within 45 days. The economic impact may be a little high for manufacturers to want to do in the beginning but with all the concerns for being ‘green’ lately we believe that it will do better in the market.

http://extra.mdc.mo.gov/nomoretrash/facts/

http://www.ecogeek.org/component/content/article/3334-biodegradable-styrofoam-made-from-milk-and-clay

Batteries:

The gun requires six D batteries that the consumer has to buy out of pocket after purchasing the weapon. First of all, the batteries weigh down the weapon and make it harder for a smaller child to use, which is the designated user group. This also means that there are a lot of used batteries going into our waste. We suggest that the gun come with a rechargeable battery. This would make the gun more light weight and easier for a young child to use. Along with this it would continue on with the ‘going green’ movement that is going on. These two impacts would make the product be more consumer friendly, increasing the sales.

Removal of Orange Handle

Another possible design revision would be to remove the orange handle located on the bottom of the gun (underneath the barrel). The orange handle's only function is to provide the user another spot to hold the product. However, this piece is not one of the most common places to put their hands, as one hand usually rests on the trigger handle, while the other holds the yellow handle. Due to this fact, removing the orange handle becomes a viable option. The gun's performance will not be affected by the removal of the handle, but economically, the removal of the handle will contribute to the overall development of the product. Money would be saved because the mold would not have to be created, saving the company start up cost, and the the actual amount of plastic needed will be much less. This will save money for the company, and in turn the gun will be cheaper for the public. This will most likely cause more guns to be sold, which is always a good thing for the company. This economical factor is the main reason for the removal of the handle.