Assembly/Gate 4

Revision as of 14:07, 30 November 2012

Purpose

After finishing up most of the analysis of the gun in the last gate, the team moved onto gate 4. In this gate, the main task that was worked on was reassembling the actual product. Also important was analyzing the mechanisms involved with the Nerf gun, as well recommending three design revisions that would help to improve the product as a whole. All of the information was placed neatly onto the group’s wiki page.

Project Management: Critical Project Review

In looking back at the project, the group for the most part has run very smoothly and without any major hiccups. The group has continued to meet once a week for the semester and we have met twice a week before the submissions. In following this plan, we have given ourselves enough time to finish everything, and also make sure everything is neat and orderly in the wiki. We have continued to meet in Greiner Hall and this has proven to be a good location for all of us.

Everyone in the group contributes to the project, and so luckily we have not had to deal with any “lacking” members. We have all learned a lot doing this project, and we have all contributed in different ways. For example, Andy has gotten really skilled at working with the wiki while Ray successfully completed the solid modeling that was part of gate 3. Also important to us is that our grade for the last gate went up from the first gate, so we know that we are improving our work. This is important to us, as we all want to do well on this project.

One of the major challenges we faced was reassembling the gun. The gun had many components and many small screws. In order to overcome this challenge, we had to all work together and go slow through the process. We used a lot of our notes from gate 2 and slowly reconstructed the gun back to its original state. This part took us a couple hours of hard work to do, but in the end, we accomplished this goal.

Other challenges we faced as a group included really understanding how to work the wiki, and having to do the presentation for our project suddenly. The first challenge has been something we as a group have been working on all semester. The skill level for each of us has improved dramatically, but it is still something that we could improve. Each gate, we have gotten better and better at formatting within the wiki. The presentation was not very difficult, but it did require some special attention. However, we feel that it ended up being very good. Overall, we have been pretty successful at overcoming any challenges that have been raised during this project.

Assembly

Step	Tool(s)	Process	Difficulty	Picture
1 - Insertion of Firing Motors	Size 1 Phillips Head Screw Driver	Slide the motors into place Fasten with two Philips head screws	2
2 - Insertion of Barrel Rotating Motor	Size 1 Phillips Head Screw Driver	Slide the motor until it is snapped into place Slide the blue support over it so the screw holes line up Fasten down with 5 screws	3
3 - Insertion of Ammo Box holder	Size 1 Phillips Head Screw Driver	Align with screw holes Fasten with 3 screws	2
4 - Insertion of Battery Pack	None, done by hand	Slide the battery pack into place	1
5 - Insertion of the Black Support Bar	Size 1 Phillips Head Screw Driver	Locate the holes that the black support bar lines up with Align the screw holes Fasten with 5 screws	3
6 - Insertion of Small White Piece	Size 1 Phillips Head Screw Driver	Align screw hole Fasten in place with 2 screws	2
7 - Insertion of Ammo Belt Feeder	Size 1 Phillips Head Screw Driver	Put blue cover over the feeder Put the metal shaft from the feeder through the hole in the bar Place the feeder in the slot and align the cover with its appropriate screw holes Fasten with one screw	2
8 - Insertion of Trigger System	Size 1 Phillips Head Screw Driver	Set blue support on black support bar Place first small white piece inline with screw holes Fasten with 2 screws Place larger white piece inline with small white piece Allowing it to slide through hole in the shell Place oval white piece over the large white piece Fasten with one screw into black support bar Place Smallest white piece on top Put the spring in place Fasten with 3 screws Place Long blue piece to the left of the white pieces Align screw holes Fasten with 3 screws Place gray piece under left end of the long blue piece Fasten with 1 screw	5
9 - Insertion of Ammo Loading Motor	Size 1 Phillips Head Screw Driver	Align Motor Assembly with screw holes in shell Fasten with 3 screws	2
10 - Attaching the Orange Handle	Size 1 Phillips Head Screw Driver	Put the orange handle back together by lining up the pieces Fasten with 4 screws Place handle in slot Fasten with single screw	1
11 - Placing the Outer Shell Back Together	Size 1 Phillips Head Screw Driver	Align the 2 halves of the outer shell and snap together We put the firing barrel on the peg that it goes around to hold the two pieces in place Fasten the 2 halves together using 14 screws	3
12 - Placing the Black Handle Back Together	Size 1 Phillips Head Screw Driver	Align the 2 halves of the black handle Fasten using 10 screws	3
13 - Attaching the Firing Barrel	Size 1 Phillips Head Screw Driver	Slide the firing barrel onto the peg it sits on Fasten using 2 screws	1
14 - Attaching the Noise Maker	Size 1 Phillips Head Screw Driver	Slide the white sound making piece onto its peg Fasten using single screw	1
15 - Attaching the Yellow Handle	Size 1 Phillips Head Screw Driver	Place the 2 pieces of the yellow handle around the yellow pegs Fasten the 2 pieces together with 6 screws	2
16 - Putting Together the Ammo Belt cover	Size 1 Phillips Head Screw Driver	Place box through square cut out. Fasten with 2 screws Slide the large spring onto the peg that it fits on Place orange lever piece over top of box into slots Attach spring Align the 2 halves of the outer orange shell Fasten together with 5 screws	5
17 - Attaching the Ammo Belt cover	Size 1 Phillips Head Screw Driver	Place ammo belt cover on the 2 flanges that it rotates around Insert one of the pegs into each side Fasten with one screw on each side	2
18 - Attaching the Gear to the Rotating Barrel	Size 1 Phillips Head Screw Driver	Put the 4 washers/wheels on the 4 pegs Place the big gear on top of them, lining up the 4 holes Fasten using 4 screws	2
19 - Attaching the Rotating Barrel	Size 1 Phillips Head Screw Driver	Slide the barrel assembly over the firing barrel Slide the yellow collar all the way to the blue piece Turn the Yellow Collar clockwise until it stops Fasten in place with 2 screws	2
20 - Putting on the Battery Cover	Size 1 Phillips Head Screw Driver	Slide the battery pack cover into place Fasten using single screw	1

We believe the assembly to have been done by hand. We believe it was done by hand rather than by robot because of the delicacy in maneuvering some of the parts into position. It would costly for a company to invest in the types of robots and programmers that would be necessary to do this.

The assembly took place in the same steps that the disassemble took place in except in reverse order.

Mechanisms

Gear Train w/ worm Drive

One mechanism that our device uses which alters specific motion and power is the gear train with worm drive. The gear trains main purpose is to decrease the output speed, while at the same time increase the output torque. As the motor spins, the worm gears are spun by the motor which enable the teeth of the worm gear to be feed into a system of gears, which share multiple axis. The varying sizes and number of the teeth adjust the speed and torque accordingly.

• Equations
  • W f = f.W t / (. cos φ n ) Frictional Force
  • T G = W t .d 1 / 2000 Torque Generated
  • σ a = W t / ( p n. b a. y ) Equation for stress induced in worm gear teeth

Trigger Mechanism

• Another mechanism that our device uses is a trigger mechanism. This mechanism generates specific control behaviors for the interactions of other mechanisms that lie withing the trigger subsystem. The trigger mechanism acts as a main support for other mechanisms within the trigger system. This mechanism helps translate forces and energies to different mechanism within the trigger system.
• Equations
  • S= (-t^2/2pi*a)*ln(pi(Tx -Tm)/4(Tc -Tm))
    • t= thickness of molding
    • a= thermal diffusivity of material
    • Tx= ejection temperature of molding
    • Tm= mold temperature
    • Tc= cylinder temperature
  • Ke = (1/2)mv2
  • E = Fd

Redesigns

Trigger Redesign

We believe that one redesign that would be beneficial to the gun is a modification to the trigger mechanism. The way the trigger mechanism currently works can be simplified. As of now when you pull back on the gray trigger piece it causes multiple reactions to take place. First the main gray trigger piece that the user actually comes into contact with, pulls on a long blue plastic piece which extends through the black handle and into the main blue shell of the gun. You can see this illustrated well in step eight of the reassembly. As it moves, it will come into contact with three switches, which then sends signals to the various motors. We suggest that this mechanism be simplified so that it takes out the long blue piece all together. We recommend that the switches be moved and placed into the black handle behind the actual trigger, having the trigger piece itself come in contact with the switched, thus having the same results occur. This simple change would add multiple benefits to the design. The elimination of the long blue piece would result in the use of less plastic in the manufacturing process. As the gun is mass produced even an insignificant piece such as this would add up over time. On top of that, in the factories, they would not need to produce the molds that are used make the shape of the piece, also saving on materials. Both of these benefits would lead to an increase in profits making it an economical factor. Both of these thing, since they are using less materials are better for the environment.

Removal of Barrel Spinning Motor

Rotating Barrel Redesign

Another design change at the system level that could be truly beneficial to the product is the actual removal of the motors. The motor the team discussed removing was the one whose only purpose was to spin the front barrels. The spinning barrel was an additional feature of the gun, but it is not help with or support the main function of the gun (to shoot darts). The barrel would remain stationary without the motor to spin it. This possible design change would have a big economic impact on the gun. First and foremost, there would be no need to manufacture a third motor. This would save a lot of money during the manufacturing phase, as less material would be needed. The motors were the most complicated parts, so removing one would reduce significantly the chance of a part getting made incorrectly. Also, on both and environmental and economic level, the removal of the motor would save a lot of energy, and thus less batteries would be needed. This would save on costs for the consumer, as well as create less wasted batteries that are potentially harmful to the environment. Removing this motor also adds a societal factors. With the barrels spinning as fast as they do if a child where to put their hand into the barrels while they were spinning it could harm their hand. This is important because safety is always something that parents take into consideration. The removal of the third motor is another possible design change on our product.