Windshield wiper assembly
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Revision as of 15:18, 23 September 2007
Failure Modes and Effects Analysis
| Item and Function | Failure Mode | Effects of Failure | S | Causes of Failure | O | Design Controls | D | RPN | Recommended Actions | Responsibility | Comments |
|---|---|---|---|---|---|---|---|---|---|---|---|
Motor connection link
| Loose connection | Little or no mechanical power transmitted to Link LN3 | 9 | Loosening of the motor connection nut due to vibrations in the motor | 4 | ||||||
Rubber Connections
| Corrosion | Doesn't connect other links and fails to transmit power to links | 6 | Tensile stress and chemical corrosion weakens the rubber with time | 3 | ||||||
Rubber Thermal Mount
| Corrosion | Does not mount properly in car; Fails to rotate the wiper arm | 7 | Overheating and use over time causes corrosion | 4 | ||||||
Cylindrical Rings
| Loss of grease | Causes grinding; Fails to rotate the wiper arm | 5 | Excessive use | 5 | ||||||
Hose
| Holes | Cause wiper fluid to leak and not reach the nozzle | 6 | Extreme temperature conditions can cause cracking; Foreign objects on windshield can puncture the hose | 9 | ||||||
Nozzle
| Chipping or breaking | Will not spray the wiper fluid onto the window | 6 | Foreign objects on windshield can break plastic; Over-stressing easily causes cracking | 9 | ||||||
Spring Connector
| Chipping or breaking | Does not secure spring thereby letting the wiper arms move away from the windshield | 7 | Foreign objects on windshield can break plastic; Over-stressing with taught spring causes cracking | 7 |
Design For Manufacturing and Assembly (DFMA)
Design For Assembly (DFA)
All and all this assembly seemed well designed for assembly. It was quick and easy to disassemble. One aspect to the windshield wiper assembly that seemed very good for assembly was that it used ball joints for all bends in the assembly. These are reasonably easy to pop on. The only heavy part was the motor which could be added on last making this assembly light and easy to move around. There is no need to flip the assembly being that all points of attachment can be accessed from the top. Also the same size wrench could be used on all nuts lowing the amount of tolling though there are different kinds of nuts. There is some room for optimization for assembly though it might hurt other aspects of the windshield wiper, such as: the rods used to transfer the motion of the motor to the wipers are all different. If there was a way to make these the same it could help the assembly process as well as the manufacturing process. The actual windshield wiper blades seem to use a rivet gun to attach the several arced pieces. The arced pieces are ascending in size and are symmetric making it pretty clear what order they go on. The rubber and metal pieces that are held by these pieces was a difficult piece to slide on but with the right tool it should not be that difficult although there are a lot of pieces it must slid in to. An advantage to the way the wiper was engineered is that besides at the base, where a nut is used to hold the wiper on, there are no extra parts used for connection. As in things are either riveted on or held in place by hooking on to the base. This not only helps in the assembly process but also helps insure that a driver would not have to deal with small parts flying off there wipers.
Design For Manufacture (DFM)
This part does not seem like an overly difficult part to manufacture. The major parts designed to transfer the motion of the motor to the wipers are all made out of steel with walls that are not too thin. They use simple processes such as casting or injection molding and then attach the post ball joint by pressing the posts in to the larger piece; none of these have high tolerances. They could be off by a good deal and still not hurt the assembly. There seems to be enough room to clamp these components down while attaching the ball joint post. All parts are rectangular, don’t taper, and are variations on each other. Injection modeling was also used around the wiper connection point; this may not be optimal as it would add an extra step to manufacturing that might be dealt with more efficiently in the assembly process. Most of the connections between two parts done in manufacturing was press fitting which is efficient and they allowed room for the parts to be clamped making this an easier process. The windshield wiper pieces were cast or injection molded--most are a hard plastic; the middle piece is metal. While these parts have many features to them, it should not be anything that casting and injection molding could not handle.
