Optical sensor assemblies were shipped to customers with screws missing thread lock. Loose screws were found in some units. Solidworks Simulation was used to estimate potential axis alignment error from a missing screw under a 10g acceleration load. The simulation predicted a maximum gap of 0.0025 inches at the missing screw location and additional optical axis deviation of 0.0044 inches. This alignment error was within specification and no reported optical errors, so no recall is needed.

1. Solidworks Simulation
A prediction of an
optical assembly
alignment error
03/22/2016
Don Blanchet
3B Associates

2. Problem
 Optical sensor assemblies have been shipped to
customers with defects. Screws without loctite
thread lock.
 Loose screws were found in the shipping container
of some top assemblies.
 All units have been deployed.
 There have been no reported optical errors.
 Estimate the potential axis alignment error to
establish a recall schedule.

3. Precision machined Assembly
lens

4. Precision machined Assembly
lens
Alignment
Axis
Center line of
lens

5. FEA mesh - 450,000 d.o.f.
Maximum
10g
Acceleration load

6. Result –max gap at missing
screw location = .0025 inches
lens
Alignment
Axis
Center line of
lens

7. Result optical axis
deviation - .0044 inches

8. Conclusion
 The single missing screw will add to
the optical misalignment budget.
 At the peak of the worst case load of
10G an additional alignment error of
.0044 inches is predicted.

9. Conclusions