Assembly Test: Elastic Averaging Jouni Huopana

Two Piece Assembly Test Two piece assembly to test “elastic averaging” as an assembly method Principle is to use multiple contacts and elasticity of the material to decrease the effects of manufacturing errors in assembly Measurements were done in the metrology lab by Didier Glaude with a CMM (accuracy of +/- 3 µm)

Elastic averaging Examples: Fiber optic connector D_Thesis_low.pdf

Elastic averaging Examples: Chrome plated LEGO™

1.Reference planes for the origin 2.Reference holes 3.Averaging features 4.Holes for the screws 5.Contact planes Design of the test pieces

Overlap of 10 µm

SECTION A SECTION B SECTION C SECTION D SECTION E SECTION G SECTION F SECTION E Control measurements for a single piece -Profile measurements for the assembly features -8 profiles measured with contact measuring machine (accuracy of +/- 3 µm) CLIAAS110109

Required shape tolerance 10 µm Measured ~30 µm

Required shape tolerance 10 µm Measured ~30 µm

Control measurements for a single piece -Profile measurements for the assembly features -8 profiles measured with contact measuring machine (accuracy of +/- 3 µm) CLIAAS SECT1 SECT2 SECT3 SECT4 SECT8 SECT7 SECT5 SECT6

Required shape tolerance 10 µm Measured ~30 µm

Required shape tolerance 10 µm Measured ~30 µm

Assembly test Two pieces were assembled and disassembled for 10 times The relative position of the center holes were measured (four places)

X+ Y+ Z+ Photo by Didier Glaude

C1C2 C3 C4 Photo by Didier Glaude

Repetition accuracy x z Calculating the distances in Z-X plane for the circle centers. Four centers are used to determine three distance. Maximum deviation is µm between the parts in 10 assembly trials. Result: Repetition accuracy of µm

Deformation of the lower piece Deformation of the lower piece in X and Y directions (0.25 deg) Due to the design of the test pieces it is possible that the assembly experiences rotation and deformation Also due to the overlapping it required a lot more force to assemble the pieces. (designed 5 µm, now 20 µm)

Conclusions Repetition accuracy of 3.78 µm was achieved –Pieces were not in the designed tolerance –Assembly accuracy is still limited by the manufacturing For the future –Assembly test of multiple pieces –Machining the assembly features first, then assembly, then machining –A lot more testing