Plastic Enclosure Functional Features

Enclosure Layout Small

 

Bosses and Inserts:
 
• Self tap or brass insert
 – Less than 2-3 insertions use self tap
 – 4 mm minimum for self tap depth
• Try to keep shorter than 9mm
 – Otherwise use sidewall tabs
 – Frames
• Combine bosses to save $$
• Through-wall brass inserts OK
 – 4-40 height is .093”
 – 6-32 short is .125”
• Studs tend to fall out prior to fastening
• Male/female hex stack-up require brass inserts
• Can also use Rivnuts
 
Access Doors:
 
• Slide-in, no fasteners
 – Requires frame or undercut
 – Difficult to create good snap
• Otherwise use fastener with brass insert and frame
 
Pockets & recesses:
 
• Machined or through with insert from back
 – Insert is best way to eliminate machine marks, less expensive for pockets larger than approximately 9 square inches
• For cosmetic purposes
 – Labels, nameplates, decals & overlays
 – Use thicker (.015”) material to hide machine marks
• For keypads
 – May require stiffener; may be less expensive to insert
 – .010” clearance per side
• For rubber feet
 – Non-skid, feet won’t slip around on plastic over time
 
Cooling - Fans & Vents:
 
• Vents
 – Machined vent pattern has great flexibility
 – Holes more expensive than slots
 – 2mm minimum slot width
 – If too long, leave in cross supports
• Fans
 – Mount with through holes or bosses
 – Self taps or brass inserts
 – Open vent pattern, keep as open as possible to reduce back pressure
 – Match area of inlet and outlet
 – Rule of thumb, cool air blows over the fan motor
 
Windows:
 
• Usually acrylic, solvent bonded into recess from rear
• Bezel approach OK for polycarbonate (FR rated)
• Acrylic/HIPS bond well
• Acrylic/ABS moderate bond
• Polycarbonate does not solvent bond
• Windows can be flush to front or recessed with chamfer
 
Cosmetics & Decorating:
 
• Decorating
 – Silkscreening
 – Paint – can fill seams inconsistently
 – Decals, nameplates
• 2-color inserts
 – Same installation as windows
 
Hinges and Handles:
 
– Standard hardware usually most economical
• Belt clips
• DIN clips
• Handles
• Latches
• Acrylic hinges (solvent bonded in place – optimized for Tool-Less process)
• Metal hinges
• Key locks