Molded part guide: grommets

Injection Molded Grommets

A grommet lines a hole so wire or tubing exits without cutting insulation on a sharp panel edge. The flexible lip has to span panel thickness tolerance and still seal, or at least stay put when someone tugs the cable.

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Pass-through

The hole in the panel is part of the grommet design

Grommets appear in appliance cords, enclosure cable exits, and automotive firewall pass-throughs. Some are a rubber ring pressed into a hole. Others are overmolded, with a rigid flange and a flexible bore.

The grommet must fit the minimum hole without falling out and not over-compress at maximum hole and maximum panel thickness. That is a tolerance stack on diameter and thickness, not a single nominal.

Strain relief features, such as a ribbed bore or a cable tie landing, belong in the same molded part when the harness is assembled through the panel.

Types

Molded grommet constructions

Type	Behavior	Tooling
Single-shot flexible TPE	Whole part elastomeric	Simple mold; may need draft on bore
Rigid flange with soft bore	Flange seals to panel; bore grips cable	Overmold the soft bore onto the rigid flange
Split grommet design	Wraps cable already terminated	Two halves ultrasonically welded or snapped

Service tiers

Grommet service tiers and quote path

Grommets seal cables through panel holes. Match tier to panel thickness range and whether the lip sees UV or fluid splash.

Tier	Environment	What matters most	Typical molded route	Quote path
1 Indoor cable exit	Office equipment, dry panels	Lip flex and bundle range	TPE or PP grommet	Instant quote; field TPE or PP
2 Strain relief	Pull on cable at exit	Lip root stress and retention	TPE with generous fillet	Instant quote; note cable OD range
3 Outdoor panel	UV and temperature swing	Cracking at lip root	UV TPV or ASA stiff ring plus TPE lip	Instant quote; describe outdoor use
4 Fluid mist	Washdown or oil mist	Material swell on lip	TPV lip; substrate PC or PA	Instant quote; name mist exposure
5 Sharp panel edges	Thin sheet metal holes	Cut-through on lip	Softer TPE; DFM on lead-in chamfer	Upload CAD; flag edge radius on mate

Materials

Elastomer families: quick reference for quote notes

List cable OD range and panel thickness in comments. Split rigid collar and soft lip in notes when using two materials.

Family	Typical use on this part type	Notes for instant quote
TPE	Soft gasket lips and beads	Field TPE; note Shore target in comments
TPV (Santoprene)	Compression gaskets and seals	Field TPV; note fluid exposure
TPU	Flexible gasket rings	Field TPU; note UV if outdoor
PP	Low-cost static gaskets on indoor products	Field PP; limited long-term compression set
Drawing callout NBR/EPDM	Legacy rubber names on prints	Describe media in notes; map to TPE/TPV on RFQ
PP	Low-cost solid grommet on indoor panels	Field PP; stiffer lip, less seal range