Design of a constant-force snap-fit mechanism for minimal mating uncertainty
Journal
Mechanism and Machine Theory
Journal Volume
55
Start Page
34
End Page
50
ISSN
0094114X
Date Issued
2012
Author(s)
Chen, Yiho
Abstract
For assembling injection-molded plastic parts having complicated geometry, snap-fit mechanisms are preferable to screws and chemical adhesives. The use of snap-fits relies on accurate calculation of interference and the associated mating force. The mating force is proportional to the interference, which is very sensitive to plastic part dimensional error. Insufficient interference would result in loose assembly, whereas excessive interference would impede assembly and possibly damage the thin-walled plastic parts. The possibility of unqualified interference impairs the high-value application of snap-fits to electronic appliances and automobiles. To alleviate the requirement for precise interference and to improve the assembly's robustness, this paper presents a constant-force snap-fit mechanism that maintains a regular mating force against a range of interference uncertainty. We propose a design formulation to find mechanism configurations that produce the most constant mating force. Illustrated simulations and experiments show that the mating force of the constant-force snap-fit is less sensitive to interference uncertainty than are typical snap-fits. Since uncertain mating force is minimized without demanding precise interference, we expect this mechanism to provide a ready alternative to existing snap-fit assembly applications.
Subjects
Compliant Mechanism
Constant-force Mechanism
Contact Analysis
Plastic Part Assembly
Snap-fit Connector
Complicated Geometry
Contact Analysis
Design Formulation
Dimensional Errors
Electronic Appliances
Injection Molded Plastic
Mating Force
Thin-walled
Compliant Mechanisms
Mechanisms
Plastic Parts
Type
journal article