| Item & Function | Failure Mode | Effects of Failure | S | Causes of Failure | P | Design Controls | D | RPN | Recommended Actions
|
G1 Back Panel Cover Screw
- Attaches back panel to guitar
| Screw holes may become stripped with frequent removal
| Back panel no longer secure, lack of panel could cause harm to bridge internals or user
| 4 | Screw holes become stripped | 4 | Test number of screw/unscrew cycles before failure on test guitars | 1 | 16 | Use metal inserts, or a latch system instead of wood screws on higher end guitars
|
G2 Back Panel Cover
- Protects internals of bridge from foreign objects and shocks
- Protects user from being pinched or scratched by springs
| Back panel may break when large amounts of pressure are put on it
| Without back panel, the bridge mechanism can become fouled on user's clothing, may pinch user
| 4 | Plastic plate cracks | 1 | Test force necessary to break back pannel | 2 | 8 | Use stronger plastic back plate, or a plastic/metal plate
|
G4 Springs
- Provides counter force to string tension
- Returns bridge to tune after use of tremolo function
| When springs removed for servicing, may shoot off
| Harm to guitar, or user
| 9 | Springs not adequately anchored | 3 | Measure spring tension at factory | 3 | 81 | Design springs to be easily removable, or create anchor cable to prevent spring from flying away (like a garage door spring cable)
|
G5 Whammy Bar
- Allows user to control tremolo function
| Shear failure at base
| Broken handle, leading to an inability to use tremolo function without replacement.
| 7 | Bar not strong enough near base | 2 | Test for imperfections using x-ray | 7 | 98 | Design bar to be thicker at base, where forces are greatest
|
| Hard to tell if bar is inserted correctly | 3 | None (design flaw) | 1 | 21 | Design bar so it is difficult to insert incorrectly
|
G6 Bridge Mounting Screws
- Pivot point for the bridge
- Provides counter force for all forces on bridge
| With excessive use, the screws may become lose
| Lose bridge, resulting in tuning problems
| 3 | Bridge screws not tight | 4 | Measure screw tightness at factory | 2 | 24 | Use special screws designed not to work lose with operation of the bridge
|
| Item & Function | Failure Mode | Effects of Failure | S | Causes of Failure | P | Design Controls | D | RPN | Recommended Actions
|
FR1 Whammy Bar
- Allows user to control tremolo function
| Shear failure at base
| Broken handle, leading to an inability to use tremolo function without replacement.
| 7 | Bar not strong enough near base | 2 | Test for imperfections using x-ray | 7 | 98 | Design bar to be thicker at base, where forces are greatest
|
| Hard to tell if bar is inserted correctly | 3 | None (design flaw) | 1 | 21 | Design bar so it is difficult to insert incorrectly
|
FR2 Springs
- Provides counter force to string tension
- Returns bridge to tune after use of tremolo function
| When springs removed for servicing, may shoot off
| Harm to guitar, or user
| 9 | Springs not adequately anchored | 3 | Measure spring tension at factory | 3 | 81 | Design springs to be easily removable, or create anchor cable to prevent spring from flying away (like a garage door spring cable)
|
FR8 Clamp Screw
- Adjusts clamp to anchor string at bridge
| Screw head becomes worn
| Becomes impossible to unscrew screws, or change strings
| 3 | Screw metal too soft | 3 | Measure screw hardness at factor | 2 | 18 | Use stronger metal for screws, or use screw head type more resistant to wear (Torx)
|
FR11 Tuner Spring
- Prevents Fine Tuners from rattling
- Keeps strings in tune
| Spring bent when user services guitar
| Spring provides inadequate pressure on tuners
| 6 | Spring too easy to access | 3 | None (design flaw) | 1 | 18 |
- Make spring harder to access
- Include warning label
|
| Spring too weak | 3 | None (design flaw) | 1 | 18 | Redesign spring to be thicker stamped piece
|
FR12 Baseplate
- Base on which all components are mounted
- Main load bearing component of bridge
- Pivots based on user input on hardened steel "knife edges"
| "Knife Edges" become dull with use
| Friction at pivot point increases, bridge ceases to return to pitch correctly.
| 5 | Knife Edges not hard enough | 1 | Batch test knife edges for hardness | 3 | 15 | Use higher grade steel for knife edges
|
| Too much pressure on knife edges | 8 | Design flaw, need pivot mechanism with larger contact area to spread pressure | 1 | 40 | Redesign pivot mechanism
|
