Enclosure Design Eliminates Screws
Simplified design saves time, money during
production and in the field
When enclosures must withstand extreme vibration and shock
during tests in the lab and subsequently in the field, engineers
typically overcompensate in their designs by adding extra
fasteners, especially screws, to reinforce unit sturdiness.
But in the case of a remote data acquisition box manufactured
by Agilent Technologies Inc., Loveland, CO, all but one screw
has been eliminated in favor of self-clinching fasteners integrated
as part of the assembly.
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Installed PEM standoffs
integrated as part of the enclosure's assembly |
Using fewer parts while meeting all performance demands,
this redesigned unit can now be assembled in about two minutes
(instead of the half-hour required with other models) and
disassembled within seconds. The result is a simpler design
that virtually snaps together and yields time and cost savings
during production and in the field.
Comparable rack-mounted enclosure designs usually contain
about 40 screws, says Agilent R&D mechanical engineer
Rick Euker, while the Agilent box specifies just one for an
electrical ground connection. The screwless design is made
possible by two different types of PEM self-clinching standoffs
from Penn Engineering, Danboro, PA. A dozen of these standoff
fasteners are specified to secure the unit's internal components.
KEYHOLE standoffs secure the motherboard to the
bottom cover and hold the front panel in place
Four PEM SNAP-TOP stainless self-clinching standoffs (Type
SSC) are used to attach the unit's power-supply board to the
bottom cover. In the process, the board sandwiches a vibration-dampening
rubber bump pad beneath it. Eight PEM KEYHOLE stainless steel
self-clinching standoffs (Type SKC) secure the 17- x 9-in.
motherboard to the bottom cover and hold the front panel in
place. Both types of standoff fasteners (each 8mm long) allow
quick assembly and disassembly of the components.
According to Euker, these permanently-installed, self-clinching
fasteners further promote DFMA objectives. Unlike loose fasteners,
they arrive at Agilent as an integral part of the box's 0.060-in.-thick
aluminum sheet metal, reducing parts count and handling requirements
during assembly. The fasteners are installed by squeezing
them into a punched or drilled hole using any standard press,
producing high pushout values.
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SNAP-TOP (above),
KEYHOLE (below)
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Other significant elements of the simplified box design included
a folded "lip" that engages a groove in the front-panel
extrusion to attach the two covers to the front panel without
screws, and specification of connectors that would snap into
the enclosure. Compared with other models, further practical
advantages were achieved. Costs for strain gauge channels
was reduced by 50%, and wiring costs were reduced by 97%.
The reach of the remote gauge was expanded 12-to-1, and accuracy
of the product was improved.
SNAP-TOP standoffs attach the unit's power-
supply board to the bottom cover
"The success of this design underscores that manufacturing
and assembly issues should be considered in the earliest stages
of the design," says Euker. "Doing so can cut costs
in half or better and ensure product reliability at the outset."
--KC
For more information:
Circle 558 - Penn Engineering & Manufacturing Corp,
or connect directly to their website via the Online Reader
Service Program at http://www.OneRS.net/104df-558
Circle 559 - Agilent Technologies or connect
directly at http://www.OneRS.net/104df-559
