Where Should the Gate Be Placed on an LSR Silicone Product?

Answer Excerpt

The gate position in an LSR silicone product should allow the material to fill the cavity evenly while keeping the gate vestige away from critical appearance, sealing, oral-contact and high-flex areas. Gate location also affects flow length, air trapping, weld or flow-front interaction, part filling and production stability. It should therefore be reviewed during DFM before mold machining rather than selected only for tooling convenience.

Liquid silicone rubber is injected into a closed heated mold and cured inside the cavity. Modern LSR systems can use cold-runner and needle shut-off systems for direct and highly controlled injection.

This means the point where silicone enters the product cavity is an important part of mold design.

A poor gate position may contribute to:

• Visible gate marks
• Long flow paths
• Uneven filling
• Trapped air
• Flow marks
• Incomplete thin sections
• Different filling between cavities
• Local deformation
• Difficult gate-area finishing
• Cosmetic rejection

For B2B buyers, gate location should not be treated as an invisible mold detail.

It can directly affect how the finished silicone product looks and performs.

What Is a Gate in LSR Injection Molding?

The gate is the controlled entry point through which liquid silicone enters the product cavity.

During LSR injection molding, the two-component silicone material is metered, mixed and injected into the heated mold, where it cures into the final product shape.

Depending on mold and runner design, the gate may feed:

• One product cavity
• Several cavities
• A thick product section
• A thin product section
• A hidden product surface
• A dedicated non-cosmetic area

After molding, the gate location may leave a small visible or tactile vestige.

Whether this is acceptable depends on where the gate is located.

A small gate mark on the hidden end of a handle may be acceptable.

The same mark on a spoon bowl, sealing edge, visible logo or soft oral-contact area may be unacceptable.

Why Does Gate Position Matter?

1. Gate Position Controls the Main Flow Direction

Silicone begins filling from the gate and moves toward the remaining cavity.

If the gate is located too far from a difficult feature, the material may need to travel through:

• Long thin sections
• Narrow channels
• Multiple thickness changes
• Fine textures
• Small openings

before reaching the end of the cavity.

This can make filling more difficult.

The gate should therefore support a practical flow path rather than forcing silicone through the most restrictive area first.

2. A Long Flow Path Can Increase Filling Risk

Consider a long silicone baby feeding spoon.

The product may contain:

• A thicker handle
• A narrow neck
• A thin spoon bowl
• Small decorative texture
• A molded logo

If silicone must travel through a long, narrow section before reaching the opposite end, the mold becomes more sensitive to flow balance and venting.

The correct gate location should help the cavity fill consistently without unnecessarily increasing flow distance.

This is particularly important for products with thin walls or fine details.

3. The Gate Should Avoid Critical Functional Surfaces

Some areas should normally receive special attention during gate review.

Examples include:

• Sealing lips
• Suction edges
• Drinking openings
• Spoon-contact surfaces
• Pacifier or teether oral-contact areas
• Flexible hinges
• Thin tear-sensitive edges
• Assembly interfaces

A gate vestige in one of these locations may affect:

• Touch
• Limpieza
• Sealing
• Comfort
• Assembly
• Appearance

The buyer should identify these critical areas on the drawing before final tooling.

Why Can Gate Position Cause Flow Marks?

When silicone enters a cavity, the material spreads outward from the gate.

The appearance of the surface can be influenced by how the flow front moves through:

• Large flat areas
• Thickness transitions
• Corners
• Textures
• Logos
• Multiple branches

A gate positioned directly beside a premium visible surface may make local flow patterns or gate-area appearance more noticeable.

The issue becomes more important for:

• Glossy silicone
• Large smooth areas
• Dark colors
• Premium consumer products

A product does not need to hide every flow direction, but the mold should avoid placing unnecessary cosmetic risk in the most visible area.

How Can Gate Position Contribute to Air Traps?

Silicone entering the mold pushes air toward the remaining empty areas.

If the gate causes several flow fronts to surround an area before air can escape, air may become trapped.

High-risk locations can include:

• End-of-fill corners
• Deep logos
• Fine textures
• Thin edges
• Closed pockets
• Small ribs

LSR molding systems commonly use mold evacuation and controlled runner technology because air management and precise filling are important for stable molding.

Gate and venting design should therefore be reviewed together.

Moving a gate can change where the final air trap appears.

Should the Gate Be Hidden?

Often, but not always.

For consumer silicone products, a gate is commonly preferred in a location that is:

• Less visible
• Non-functional
• Easy to inspect
• Easy to trim or control
• Away from high-flex areas
• Away from food-contact or oral-contact zones where practical

However, hiding the gate should not create a much worse flow path.

For example, placing the gate at the far end of a product only because that position is invisible may force material through a long thin section and create incomplete filling.

The correct design balances:

Appearance + Filling + Function + Production stability.

What Is a Gate Vestige?

A gate vestige is the small remaining mark where the silicone entered the cavity.

Depending on the mold system, the vestige may appear as:

• A tiny raised point
• A shallow mark
• A small circular area
• A slightly different surface texture

The acceptable condition should be defined before mass production.

Buyers should confirm:

• Gate location
• Maximum visible gate mark
• Whether the area is touched by the user
• Whether the gate is on a cosmetic surface
• Whether trimming is required
• Whether the gate affects packaging or assembly

Statements such as:

Gate mark must be invisible.

are often too vague.

A better standard defines where the gate is allowed and how the approved sample should look.

How Should Gate Position Be Selected for a Silicone Baby Spoon?

A silicone baby feeding spoon is a useful example because it contains several different functional areas.

These may include:

• Spoon bowl
• Thin spoon edge
• Neck
• Mango
• Logo area
• Grip texture

The spoon bowl and edge are directly involved in feeding.

A visible or rough gate vestige in this area may be undesirable.

The handle end is usually less functionally sensitive, but the final gate location must still be evaluated according to:

• Material flow
• Product length
• Wall thickness
• Mold structure
• Logo location
• Surface finish

This does not mean every silicone spoon should automatically be gated at the handle end.

The final position should be confirmed during custom silicone mold development based on the actual 3D design.

How Does Wall Thickness Affect Gate Design?

The gate should not be reviewed independently from wall thickness.

A product may contain:

• Thick sections
• Thin sections
• Reinforcement ribs
• Flexible edges
• Local textures

Material generally fills different geometries differently.

If the product transitions from a thick area into an extremely thin area, gate location may influence whether the thin feature fills consistently.

Important questions include:

• Does the material reach thin areas early enough?
• Are there unnecessary long thin flow paths?
• Will air become trapped at the end?
• Will one side fill before another?
• Does the gate create excessive pressure around a cosmetic surface?

The engineering team should review the full product cross-section.

What About Multi-Cavity Molds?

A multi-cavity mold produces several products during one cycle.

The runner and gate system must deliver controlled material filling to each cavity.

ENGEL has demonstrated multi-cavity LSR systems where fill quantity can be individually controlled through cold-runner needle shut-off technology, showing how important precise cavity filling becomes in larger production molds.

During sample approval, buyers should compare:

• Product weight
• Gate appearance
• Filling completeness
• Dimensions
• Flow marks
• Flash
• Functional performance

across all active cavities.

One good cavity does not prove that the entire production mold is balanced.

Why Can Changing the Gate After Tooling Be Expensive?

The gate is part of the mold-flow and runner strategy.

Moving it after the mold is finished may affect:

• Runner design
• Mold inserts
• Cavity machining
• Venting
• Product appearance
• Filling balance

The modification may require:

• Mold rework
• New sample trials
• New dimensional inspection
• New cosmetic approval
• Functional retesting

This is why gate position should be included in the DFM review before mold machining.

What Should Buyers Check During Sample Approval?

Gate Appearance

Inspect:

• Gate height
• Surface mark
• Roughness
• Trimming
• Local deformation

Product Filling

Check:

• Thin edges
• Spoon tips
• Logos
• Textures
• Ribs
• End-of-fill locations

Flow Marks

Inspect visible surfaces under consistent lighting.

Air Traps

Look for:

• Bubbles
• Burn marks
• Missing material
• Incomplete corners

Functional Performance

The finished product must still pass the real use test.

For a feeding spoon, inspect:

• Spoon edge
• Handle stability
• Product flexibility
• Surface comfort
• Shape recovery

Mold-Cavity Consistency

Compare samples from every cavity.

Gate Design DFM Checklist

How LYA Silicone Supports LSR Gate and Mold Design Review

LYA Silicone currently provides OEM and ODM development for baby, pet, outdoor and educational silicone products, and its current factory information lists both liquid silicone injection molding and solid silicone molding equipment.

For LSR projects, engineering review may include:

• Product drawing review
• Gate-position evaluation
• Flow-path review
• Wall-thickness analysis
• Venting review
• Surface-finish review
• Mold-cavity planning
• Sample production
• Gate-area inspection
• Filling validation
• Pilot production
• Mass-production quality control

Gate position should be selected as part of the complete product and mold system, not as an isolated tooling decision.

Frequently Asked Questions

Does Every Silicone Product Have an Injection Gate?

No.

This article mainly applies to injection-molded LSR products.

Compression-molded silicone products use a different material-loading and molding approach. LYA’s current OEM information lists both liquid molding and compression molding among its processing routes.

Should the Gate Always Be Put on a Hidden Surface?

Not necessarily.

A hidden gate location is useful only when it still supports stable filling and product function.

Can Gate Position Cause Incomplete Filling?

It can contribute to filling problems when the resulting flow path is too long, restrictive or poorly balanced.

Can Gate Position Cause Air Traps?

Yes.

Changing the direction of material flow can change where air becomes trapped, so gate and venting design should be reviewed together.

Can the Gate Be Put on a Logo Area?

It is usually better to avoid creating unnecessary gate marks on important branding surfaces when another technically suitable location is available.

Should Buyers Approve the Gate Mark?

Yes.

The final molded sample should establish the acceptable gate location and appearance before mass production.

Review the Gate Before the Mold Is Machined

A gate may occupy only a very small area of the final silicone product, but its influence can extend across the entire cavity.

Gate position can affect:

• Filling
• Flow direction
• Air trapping
• Surface appearance
• Gate vestige
• Thin features
• Product consistency

Before tooling an LSR silicone product, buyers should review the gate together with wall thickness, venting, cosmetic surfaces and critical functional zones.

To review the gate and mold design of your custom LSR project, send Silicona LYA your 3D drawing, product dimensions, material requirement, target hardness, cosmetic requirements and estimated production quantity.