P09310: Automatic Shift Controls for ATV
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Design for Manufacturing

Table of Contents

There are many similar products out in the market that can perform same tasks easily but; are they easy to manufacture? Designing a product which is easy to manufacture and easy to assemble is the key to building a product that is successful in market. When parts can be fabricated faster it lowers manufacturing cost of the product hence that lowers the product cost itself. Lowering the cost of the product is also one of the important customer requirements in the design of the ATV autonomous shift control system. Since the design of the ATV shifting system is going to be mass produced the ATV team has designed the shifting system that is easy to manufacture.

One of the important customer requirements is to reduce weight of the whole system. Reducing the number of parts in the system will save time in assembly and also reduce weight. By incorporating more functions in a single part the number of parts used can be reduced. One of such design is the chain guard solenoid mount. This component serves as a chain guard, and also a mount for the solenoid. The present chain guard mounting locations are used to mount the new redesigned chain guard solenoid mount.

QFD

To evaluate features of different shifters out in the market a competitive benchmark analysis was done. After side by side comparison of the shifters each features of different shifter designs were ranked. Team P09310 took the best features out of each design to come up with a robust product. After analyzing designs with strong features the team came up with our design concept. Looking at the customer requirements and the design capabilities the team thought that the best design concept would be to use solenoid for shift actuation force. To verify the design concept further analysis had to be done.
Phase 1 QFD
In developing a quality function deployment for shift system for Polaris ATV, benchmarking categories were chosen. The candidates for quality function deployment were chosen for two different categories pneumatic and electrical.

A. pneumatic system - This system uses a pneumatic cylinder provided by compressed air from the compressor which provides force for gear shifting.

B. pneumatic system with clutch activation - This is a same system as the pneumatic system but is equipped with additional feature for clutch activation.

C. wheel driven compressor - This design consist of the pneumatic system but the only difference is that the compressor is driven by a rotating shaft connected to wheel which is activated whenever the wheel is turning.

D.electrical actuator - This system eliminates most of the components and replaces an air cylinder, compressor and solenoid valve with a single solenoid actuator powered by the 12 V ATV battery.

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Based on the raw score of engineering metrics the top three metrics are engine spark cut out with a relative weight of 15% , shift time with 14% realtive weight and (shift force, life cycle and weight)all getting the 12% relative weight. The top three engineering metrics are related to the customer requirements automatic shifting, safe for transmission, smooth and fast shifting which are heavily weighted. All four systems score the same under the 'fast shifting' customer requirement and like wise for the auto shifting option. For the customer requirement 'safe for transmission', the clutch activation in design B (Pneumatic shifting with clutch activation) is not necessary due to the auto clutch system built into the ATV. On the 'shift smoothly' customer requirement, design B gets higher score since the ATV has an auto clutch system built in. Therefore, clutch activation will not be an issue. The other designs score the same just below the pneumatic shift with clutch activation. According to the result on technical benchmarking out of top three engineering metrics the design D (electrical solenoid actuation) scores the highest in two of the engineering metrics shift time and engine spark cutout.
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Phase 2 QFD
After analyzing results in Phase 1 QFD much attention is given to engineering metrics with high scores on phase 1 analysis. Looking at Phase 2 QFD most of the components on the pneumatic systems have little or almost no scores on the engineering metrics that scored high on QFD 1. From this it is apparent that a new system other than pneumatics would have to be chosen.

A new Phase 2 QFD is generated for the proposed design with an electrical actuator system rather than pneumatic air cylinder system. The electrical solenoid replaces all the high price components such as air compressor, solenoid valves and air cylinder. The proposed design is comprised of parts that outputs mechanical movement through electrical input. From research it was found that the failure rate of the solenoid actuator is highly unlikely.

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Cost Worth Analysis

The team P09310 believed that with more mechanical moving parts the more chance of failure. Since the components are expensive the cost for repair and service is going to be very high. This gave an opportunity to investigate on part elimination and on a new concept design.
P08310 Cost Worth Analysis
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According to the Cost Worth diagram a strong candidate for cost reduction are the solenoid valves and the air line fittings. The solenoid valve has a relative cost of 17% and a relative worth of 9% which results in a C/W ratio of 1.90.

According to cost worth analysis, quality enhancement candidates are the air cylinder, the micro controller and the compressor. This is because they have relatively high worth 16%,14% and 14% respectively. Improving the quality or features of these parts will generate a greater satisfaction to the customers because they associate high worth to these parts.

A new Phase 2 QFD is generated for the proposed design with an electrical actuator system rather than pneumatic air cylinder system. The electrical solenoid replaces all the high price components such as air compressor, solenoid valves and air cylinder. The proposed design is comprised of parts that outputs mechanical movement through electrical input. From research it was found that the failure rate of the solenoid actuator is highly unlikely.

Using phase 2 QFD another cost worth analysis for the proposed design was preformed to determine the feasibility and assess the design.

P09310 Cost Worth Analysis
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P09310 cost worth analysis

The cost worth analysis diagram shows high cost of the solenoid (electric actuator). This was realized by the team. The solenoid actuator replaces components such as the air compressor, solenoid valves, and air cylinder, which have high customer weight given in QFD 1. The team realized that a robust product with high durability the increased cost for a solenoid actuator is a small price to pay.

Design for Manufacturing and Assembly

In the design of ATV autonomous shifting system the parts used are readily available in the market. Since the amount of parts used in the design is not customized, analysis on design for assembly is crucial. The design will implement basic design for manufacturing and assembly guidelines.

Reduce part count One of the guideline for assembly is intended to minimize part count. Hence some of the design concepts during the design phase were immediately eliminated such as using a linkage to shift the ATV shifter. Further reduction of part count is taken into consideration in designing a handle bar switch where instead of an initial and more common two piece design a new one piece slide in design has been chosen.

Multiple function parts Multiple function performing parts will be designed in order to decrease part count. The foot lever which is a manual switch to shift in case of a failure will also function as a tab where the air cylinder pushes down or pulls up on it. The bracket to hold the air cylinder will also function as a chain guard serving two functions. This feature of the chain guard will be further verified after a thorough cost benefit analysis.

Ease of insertion and assembly To permit assemblies in open space not in closed space, the micro controller case will have a open flat base ,without the confinement of walls, where the printed circuit board gets mounted leaving open space all around for the operator to perform soldering tasks easily. A cover will be used to protect the electrical system from foreign materials like rain, water and dirt.

Use of standardized parts All bolts and nuts used on the ATV to fasten equipments will be standardized in order to reduce part variety. The air lines will be harnessed together and for permanent solution the group has decided to go with steel braided lines instead of plastic tubing. The micro controller will have a port on the PCB for programming the Micro controller according to the user needs.

Color code different but similar looking parts Parts that are similar such as air line fittings and air cylinder valve fitting will be color coded for quick intuitive installation. Color coding will also help in reducing confusion where the parts are different but shaped similarly. Where ever possible alignment features will be provided on the assembly parts. Instead of welding tabs since the product is going to be sold as a separate kit fasteners will be used however the number of fasteners used will be minimized.

Machining Parts Parts that need to be machined will be designed so that even a manual mill can perform the machining job. For designing parts that needs machining some of the design considerations are:


There are many similar products out in the market that can perform same tasks easily but; are they easy to manufacture? Designing a product which is easy to manufacture and easy to assemble is the key to building a product that's successful in market. When parts can be fabricated faster it lowers manufacturing cost of the product hence that lowers the product cost itself. Lowering the cost of the product is also one of the important customer requirements in the design of the ATV autonomous shift control system. Since the design of the ATV shifting system is going to be mass produced the ATV team has designed the shifting system that is easy to manufacture.

Weight Reduction

One of the important customer requirements is to reduce weight of the whole system. Reducing the number of parts in the system will save time in assembly and also reduce weight. By incorporating more functions in a single part the number of parts used can be reduced. One of such design is the chain guard solenoid mount. This component serves as a chain guard, and also a mount for the solenoid. The present chain guard mounting locations are used to mount the new redesigned chain guard solenoid mount.

The total weight reduction was almost 4 lbs compared to the P08310 team which was 7.85 lbs.

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Part Count Reduction

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In the above graph we can see that team P09310 has reduced part count by 35% compared to the generation 2 design (P08310) which uses pneumatic system for shift control. This reduction in number in parts serves great in reduction in time for assembly. The part count takes into account that the microcontroller unit , the handle bar unit and the gear indicator unit are one single components for both designs.

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A mounting clamp is used to clamp the solenoid. The clamp has a pivoting capability. This extra feature allows for the solenoid to be adjusted while installing. The pivot mounting clamp can be adjusted for different specification of force required to shift. The foot lever which is a manual switch to shift in case of a failure has a tab where the solenoids shaft attaches to.

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The chain guard solenoid mounting piece replaces the current chain guard. To reduce part variety during assembly the double feature chain guard is made so that all the ATV out of the production line will have them. This enables future usage of these mounting locations for the solenoid if the autonomous shift control system is to be added on later after purchase by a customer.

All the components used on micro controller PCB (Printed Circuit Board) are surface mount components. Instead of through hole technology which requires human labor and is time consuming our micro controller PCB uses SMT (Surface Mount Technology). The placements of surface mount components by pick and place machine is fast and precise. This fast assembling of the PCB reduces cost assembly cost and hence reflects on the product cost itself. The fasteners used in the product are standardized. Therefore there is a less chance of ruining threads if wrong style screw is used. They are all 8-32 of size. There are different styles of fasteners used in the product this is mainly because of constraints faced during designing and for aesthetic reasons.


Downloads

Phase I QFD

Phase II QFD

PhaseII QFD P09310 ] [[P08310 cost worth analysis