LSR vs HCR Silicone: Which Molding Process Is Better for Your Custom Product?

When developing a custom silicone product, one of the most important manufacturing decisions is choosing the right molding process.

Two of the most common options are:

• Liquid Silicone Rubber, or LSR
• High Consistency Rubber, or HCR

Both materials are silicone elastomers, but they behave very differently during processing.

LSR is a low-viscosity liquid material that is usually processed by injection molding.

HCR is a high-viscosity solid silicone rubber that is commonly processed by compression molding, transfer molding, or conventional rubber injection molding.

The right choice depends on the product design, production volume, tolerance, application, material requirements, and total project cost.

This guide compares LSR and HCR from an engineering and purchasing perspective to help you choose the most suitable process for your custom silicone product.

1. What Is LSR?

LSR stands for Liquid Silicone Rubber.

It is normally supplied as a two-part liquid system.

The two components are mixed at a controlled ratio and injected into a heated mold, where the silicone cures into the final part.

Because LSR has very low viscosity, it can flow into small cavities and fine features.

This makes it suitable for precision components with complex geometry.

Typical LSR applications include:

• 医療用シリコーン部品
• ベビー用授乳用品
• シリコーン製バルブ
• 防水シール
• 自動車用コネクタ
• 電子部品
• Precision gaskets
• シリコーンオーバーモールド
• Thin-wall silicone parts

LSR is widely used in industries where repeatability, cleanliness, and automated production are important.

2. What Is HCR?

HCR stands for High Consistency Rubber.

It is also commonly called high consistency silicone rubber or solid silicone rubber.

Unlike LSR, HCR has a thick, gum-like consistency before molding.

It usually requires mechanical mixing and preforming before being placed into the mold.

HCR is commonly processed through:

• 圧縮成形
• トランスファー成形
• Rubber injection molding
• Extrusion

Typical HCR applications include:

• Silicone gaskets
• シリコンパッド
• Kitchen products
• 産業用シール
• Silicone covers
• Silicone mats
• 消費財
• シリコーンチューブ
• General-purpose molded silicone parts

HCR is widely used because of its flexible processing options and relatively economical tooling.

3. LSR vs HCR: Main Difference

The biggest difference between LSR and HCR is how the material is processed.

LSR is liquid and is generally injected into a closed mold.

HCR is solid or semi-solid and is generally loaded into a mold as a preformed piece of material.

この違いは、以下の点に影響します：

• 金型設計
• 生産速度
• Labor cost
• 自動化
• Part precision
• 製品の複雑さ
• フラッシュ制御
• 生産量
• 単価

For this reason, the correct process should be selected during the early design stage.

4. Material Flow and Product Complexity

LSR has very low viscosity.

This allows the material to flow into small channels, thin walls, micro-features, and complex cavities.

LSR is therefore particularly suitable for products that contain:

• 薄い壁
• Fine details
• Small holes
• Complex sealing features
• Microstructures
• Narrow flow paths

HCR has higher viscosity.

It does not flow as easily into very small features.

However, HCR performs well for many medium and large silicone products with relatively simple geometry.

If your product has very fine details or complex internal structures, LSR may offer better molding performance.

5. Tooling Cost

Tooling cost is one of the most important differences between LSR and HCR.

LSR Tooling

LSR molds are usually more complex.

以下の要件が求められる場合があります：

• Precision mold machining
• Cold runner systems
• Accurate temperature control
• 真空システム
• Precision venting
• Automated demolding
• Tight mold alignment

As a result, LSR tooling normally requires a higher upfront investment.

HCR Tooling

Compression molds for HCR are generally simpler.

The mold structure may be easier to design and manufacture.

This usually results in a lower initial mold cost.

For small production quantities or simple products, HCR can therefore be more economical.

6. Production Volume

Production volume is another major factor.

LSR is particularly suitable for medium- and high-volume production.

Because LSR molding can be highly automated, the process can achieve:

• Short cycle times
• 材料の自動供給
• Automatic molding
• 自動離型
• Lower labor requirements

For large-volume projects, the higher tooling cost can often be offset by lower unit production costs.

HCR molding typically requires more manual operations.

These may include:

• Material cutting
• Preforming
• Mold loading
• 型抜き
• フラッシュトリミング

For lower-volume projects, this may still be economical because the initial tooling cost is lower.

7. Labor Cost

LSR production can be highly automated.

Once the process is established, operators may only need to monitor the molding system and perform inspection.

This reduces labor cost per piece.

HCR compression molding often requires more manual handling.

Workers may need to:

• Weigh material
• Cut silicone
• Place material into the mold
• Remove molded parts
• Trim flash

As labor costs increase, automation becomes more important.

For high-volume production, LSR often provides better long-term cost efficiency.

8. Precision and Tolerance

LSR injection molding offers excellent process consistency when the mold and process parameters are properly controlled.

It is suitable for precision applications where repeatability is important.

例としては、次のようなものがあります：

• 医療用バルブ
• 電子シール
• 自動車用コネクタのシール
• Precision diaphragms
• Small silicone components

HCR can also achieve good dimensional control.

However, because more manual steps may be involved, process variation may be slightly higher.

For products with critical dimensions, the manufacturer should review:

• Silicone shrinkage
• 製品の形状
• 肉厚
• パーティングライン
• 金型の構造
• 測定方法

Tolerance should always be defined based on functional requirements rather than applying unnecessarily tight tolerances to every dimension.

9. Flash Control

Flash is excess material that forms around the mold parting line.

LSR molds can achieve very small flash when designed and machined correctly.

Precision mold alignment and controlled injection help reduce flash formation.

This is particularly important for:

• 医療用部品
• Small valves
• シーリング製品
• 電子部品

HCR compression molding generally produces more visible flash.

Additional trimming may therefore be required.

For products where appearance or sealing performance is critical, flash requirements should be specified during the RFQ stage.

10. Surface Quality

Both LSR and HCR can produce high-quality surfaces.

The final appearance depends mainly on:

• Mold surface finish
• Silicone formulation
• 金型温度
• 硬化条件
• 型抜き
• 後処理

LSR is often preferred for precision products with smooth or detailed surfaces.

HCR is also suitable for:

• マット仕上げ
• 質感のある表面
• Glossy surfaces
• Functional industrial surfaces

For consumer products, mold texture can be used to create different visual and tactile effects.

11. Material Purity and Cleanliness

LSR is widely used in applications where cleanliness is important.

Because the material can be processed in a closed system, contamination risk can be reduced.

This makes LSR suitable for:

• 医療製品
• ベビー用品
• Food-contact parts
• Precision electronic components

HCR can also meet food-grade and medical-grade requirements when the correct silicone material and manufacturing controls are used.

The choice should be based on the actual material standard and application requirements.

12. Medical Applications

LSR is commonly used for medical silicone components.

代表的な用途としては、次のようなものがあります：

• 医療用シール
• バルブ部品
• 呼吸器系
• ウェアラブル医療機器
• Silicone diaphragms
• Precision tubing connectors

LSR is suitable for medical projects because of:

• 高い再現性
• Clean processing
• 自動化
• Biocompatible material options
• Precision molding capability

However, not every medical silicone product requires LSR.

HCR may also be used for larger or simpler medical silicone components.

Material certification and process validation are more important than simply choosing one molding method.

13. Baby Care and Food Applications

Both LSR and HCR are widely used in baby care and food-contact products.

LSR is often selected for:

• 哺乳瓶の乳首
• シリコーン製バルブ
• おしゃぶりの構成部品
• Feeding components
• Precision sealing parts

HCR is commonly used for:

• シリコン製歯固め
• シリコン製のボウル
• Baby plates
• シリコン製スプーン
• Silicone mats
• Larger molded baby products

For baby care products, important requirements may include:

• 食品用シリコーン
• BPA-free material
• 臭気対策
• 色の均一性
• 表面品質
• お手入れが簡単

The best molding method depends on product structure and production volume.

14. Silicone Overmolding

LSR is especially suitable for automated overmolding.

It can be molded onto compatible substrates such as:

• PC
• PA
• PBT
• PPSU
• ステンレス鋼
• アルミニウム
• Other engineered materials

LSRオーバーモールドは、以下の用途で使用されています：

• 医療機器
• 自動車部品
• 電子機器用筐体
• 防水コネクタ
• Handheld devices

HCR can also be used for overmolding, but the process is generally less automated.

If the project requires tight bonding control and high production consistency, LSR is often preferred.

15. Thin-Wall Products

Thin-wall silicone components are difficult to mold using high-viscosity materials.

LSR flows easily into thin sections.

そのため、次のような用途に適しています：

• 薄い膜
• フレキシブルバルブ
• Small sealing lips
• Thin-wall covers
• Precision diaphragms

For very thin products, LSR usually provides better filling performance.

16. Large and Simple Silicone Products

HCR is often more economical for large silicone products with relatively simple structures.

例としては、次のようなものがあります：

• シリコンパッド
• Silicone mats
• 大型ガスケット
• 保護カバー
• 産業用部品

Using LSR for these products may not provide enough benefit to justify the higher tooling investment.

In such cases, HCR compression molding can offer a better balance between tooling cost and production cost.

17. LSR vs HCR Cost Comparison

The total cost should be evaluated based on the complete production program.

LSR

Typically offers:

• Higher tooling cost
• Higher automation
• 人件費の削減
• Shorter cycle time
• Better for high volume
• Good precision
• 再現性が良い

HCR

Typically offers:

• Lower tooling cost
• 手作業による処理の増加
• Higher labor content
• Longer cycle time
• Good for low to medium volume
• Flexible manufacturing
• Good cost performance for simple products

A project with 1,000 parts may favor HCR.

A project requiring hundreds of thousands or millions of parts may benefit more from LSR.

18. Which Process Is Better for Prototypes?

For early-stage development and small production quantities, HCR compression molding is often easier to start with.

The lower tooling investment can reduce development risk.

However, if the final product will definitely use LSR during mass production, it may be better to develop the prototype using a process closer to the final production method.

This can help validate:

• Product shrinkage
• 金型充填
• 表面品質
• パーティングライン
• 型抜き
• Material performance

The prototype strategy should match the final production goal.

19. Which Process Is Better for High-Volume Production?

LSR is generally more suitable for high-volume automated production.

Once the mold and process are validated, production can run with relatively little manual intervention.

This makes LSR attractive for industries such as:

• Medical
• 自動車
• 家電製品
• Baby care
• Industrial sealing

For very large volumes, the lower labor cost and higher productivity can significantly reduce unit cost.

20. How to Choose Between LSR and HCR

Before choosing the molding process, consider the following questions.

What Is the Estimated Annual Volume?

High-volume projects often favor LSR.

Lower-volume projects may favor HCR.

Is the Product Geometry Complex?

Thin walls, fine details, and microstructures may favor LSR.

Large and simple shapes may favor HCR.

What Is the Tooling Budget?

If the initial tooling budget is limited, HCR may be more practical.

Are Tight Tolerances Required?

Precision components may benefit from LSR.

Is Automation Important?

LSR is better suited to highly automated manufacturing.

Is the Product Used in Medical or Precision Applications?

LSR is commonly selected for these applications.

Is the Product Large?

Large silicone parts are often more economical with HCR.

21. LSR vs HCR Comparison Table

因子	LSR	HCR
Material Form	液体	Solid / Gum
Main Process	Injection Molding	Compression / Transfer Molding
金型費	より高い	下へ
自動化	高い	Medium to Low
Labor Requirement	下へ	より高い
生産量	Medium to High	Low to Medium
Thin-Wall Capability	素晴らしい	Moderate
複雑な形状	素晴らしい	いい
精度	高い	いい
フラッシュ制御	Very Good	Moderate
オーバーモールド	素晴らしい	あり得る
Large Simple Parts	あり得る	Very Suitable
Medical Applications	Very Common	あり得る
Prototype Cost	より高い	Usually Lower

22. Common Mistakes When Selecting LSR or HCR

One common mistake is choosing only based on mold price.

A lower mold price may look attractive at the beginning, but a labor-intensive process can become expensive during long-term production.

Another mistake is selecting LSR simply because it is considered more advanced.

LSR is not automatically the best choice for every product.

A large, simple silicone pad may be produced more economically using HCR.

The correct decision should balance:

• 金型費
• 単価
• 年間取扱量
• 製品の形状
• 品質要件
• 自動化
• Long-term production plan

結論

Both LSR and HCR are important silicone manufacturing technologies.

Neither process is universally better.

LSR is generally more suitable for precision, complex, thin-wall, high-volume, and automated applications.

HCR is often more suitable for simple, larger, lower-volume, and cost-sensitive products.

For a custom silicone project, the best process should be determined by the complete product requirements rather than material preference alone.

Fuhongying provides custom silicone molding, LSR injection molding, HCR compression molding, and silicone overmolding services for OEM and ODM projects.

We support applications in baby care, medical devices, consumer electronics, automotive components, sealing products, sports products, and industrial silicone components.

Send us your 2D drawing, 3D file, sample, estimated order quantity, and application requirements for a DFM review and quotation.

よくある質問

What is the main difference between LSR and HCR?

LSR is a low-viscosity liquid silicone that is normally injection molded. HCR is a high-viscosity solid silicone that is commonly compression molded or transfer molded.

Is LSR more expensive than HCR?

LSR normally requires more expensive tooling, but the automated production process can reduce labor and unit cost for high-volume production.

Which is better for small production quantities?

HCR is often more economical for low-volume or simple custom silicone products because compression tooling is generally less expensive.

Which silicone process is better for medical products?

LSR is widely used for medical components because it supports precision molding, automation, and clean processing. However, HCR can also be suitable depending on the product design and material requirements.

Which process is better for silicone overmolding?

LSR is commonly preferred for precision and automated silicone overmolding, especially for plastic, metal, medical, automotive, and electronic components.

Can both LSR and HCR use food-grade silicone?

Yes. Both LSR and HCR materials can be supplied in food-grade formulations. The correct material should be selected according to the required food-contact regulations and application conditions.