Before specifying a silicone component, there is a technical decision that determines everything else: extrusion or moulding? This choice is not interchangeable. Each process has structural advantages, geometric limitations and cost ranges that make it suitable for specific applications. Choosing incorrectly means cost overruns, extended lead times or components that fail to perform their function.
This article does not explain what extrusion is. It explains when to use it, what can be manufactured with it and what specification errors to avoid. If you need a continuous profile, a tube or a seal with constant geometry, extrusion is probably your process. If you need a part with complex three-dimensional geometry, it is not.
1. Extrusion vs. moulding: technical decision criteria
Extrusion produces constant cross-sections in continuous lengths. Moulding produces three-dimensional geometries defined by a closed mould. This fundamental difference determines when to use each process.
When to choose extrusion
- The part has a constant cross-section along its length
- Lengths greater than 500 mm are required (although shorter pieces are manufactured)
- Production volume justifies amortisation of extrusion tooling
- The geometry is a profile, tube, cord or linear seal
- Flexibility to cut to length per order is needed
When NOT to choose extrusion
- The part has cross-section variations along its length
- Closed forms such as O-rings or diaphragms are required
- The geometry includes complex internal cavities or localised reinforcements
- The component requires integrated metal inserts
- The application demands very tight dimensional tolerances in all directions
2. What problems extrusion solves compared to moulding
Extrusion is not simply an alternative to moulding. It solves specific problems that moulding cannot address efficiently:
Continuous lengths
An extruded profile can be manufactured in coils of tens of metres and cut to the exact length required. Moulding would require a specific mould for each length, multiplying tooling costs.
Dimensional flexibility
The same extruded profile can be supplied in lengths of 100 mm or 10 metres without tooling change. This allows more efficient inventory management and response to demand variations.
Reduced tooling cost
An extrusion die has a significantly lower cost than an injection or compression mould for equivalent geometries. For medium runs or applications where design may evolve, this reduces investment risk.
Development lead times
Manufacturing time for an extrusion die is typically shorter than for a complex mould. This accelerates prototyping cycles and initial production runs.
3. The silicone extrusion process: technical fundamentals
Silicone extrusion is a continuous process where uncured material is forced through a die that defines the profile cross-section. The material exits the die in an uncured state and immediately passes through a vulcanisation oven where it acquires its definitive mechanical properties.
Process stages
- Feeding: The silicone compound is introduced into the extruder
- Plasticisation: The screw conveys and homogenises the material
- Forming: The material passes through the die adopting the defined section
- Vulcanisation: The uncured profile passes through a hot air or infrared oven
- Cooling: The vulcanised profile is cooled in a controlled manner
- Cutting/Coiling: The final product is cut to length or coiled continuously
Critical process variables
The dimensional stability of the extruded profile depends on precise control of multiple variables:
- Extrusion temperature: Affects viscosity and flow behaviour
- Line speed: Determines residence time in the oven
- Vulcanisation temperature: Controls the degree of crosslinking
- Haul-off tension: Influences final dimensions and molecular orientation
- Die design: Compensates for die swell
A well-controlled extrusion process produces profiles with minimal dimensional variation throughout production. Standard tolerances according to ISO 3302-1 for extruded products are class E1 or E2, depending on profile complexity.
4. Product types manufacturable by extrusion
Silicone extrusion enables the manufacture of a wide range of products with highly diverse geometries. The main product families and their technical characteristics are detailed below.
4.1 Extruded silicone profiles
Extruded profiles constitute the broadest category of extrusion products. They can be manufactured in solid (compact) or cellular (sponge) section, and accommodate geometries from simple cords to complex sections with multiple cavities.
Solid profiles
Manufactured from solid VMQ silicone, solid profiles are used in applications requiring mechanical strength, sealing under pressure or fluid contact. Available hardnesses range from 10 to 90 Shore A, although the most common range in extrusion is 40 to 80 Shore A.
- Sealing profiles for industrial doors and windows
- Closure seals for equipment and enclosures
- Edge and corner protection profiles
- Guides and sliding rails
- Decorative and finishing profiles
Custom Silicone Profiles
VMQ silicone profiles custom-designed according to drawing or sample. Personalized sections, specific formulations, and RAL colors. Compliance with FD...
View product →Cellular profiles (sponge)
Cellular silicone profiles are manufactured through controlled expansion of the material during vulcanisation. The resulting density typically varies between 0.4 and 0.8 g/cm³, compared to 1.1-1.2 g/cm³ for solid silicone.
Advantages of cellular profiles include greater compressibility, better thermal and acoustic insulation, and lower closure force required. However, they are not suitable for applications with fluid pressure or direct liquid contact.
- Low-compression sealing gaskets
- Thermal insulation profiles
- Dampers and vibration absorbers
- Gaskets for railway applications (Series 33, EN 45545-2)
Sponge Silicone Profiles (Cellular)
Extruded sponge silicone profiles with a closed-cell structure. Low density, high compressibility, and elastic recovery. Compliance with FDA, EC 1935/...
View product →Co-extruded profiles
Co-extrusion enables the combination of two or more materials in a single profile. Typical combinations include solid + cellular silicone, different silicone hardnesses, or silicone + textile or metal reinforcement.
This allows optimisation of the profile for multiple functions: for example, a solid sealing zone combined with a cellular absorption zone, all in a single piece without subsequent assembly.
4.2 Silicone tubing
Silicone tubes are extruded products with annular cross-section, defined by their internal diameter, external diameter (or wall thickness) and length. The manufacturable dimensional range extends from microtubes with 0.5 mm internal diameter to large-bore tubes with internal diameters exceeding 100 mm.
Standard industrial tubing
Industrial silicone tubes are used for fluid conveyance, air, vacuum and transfer applications. Standard formulations (Series 2, 12) offer good chemical resistance, flexibility across a wide temperature range (-60 to +200 °C) and FDA compliance for food applications.
Industrial Silicone Tubing
Extruded VMQ silicone industrial tubing (hose). High flexibility, thermal resistance from -60 °C to +200 °C, and chemical stability. Hardness 10-90 Sh...
View product →Tubing for medical applications
Medical-grade tubes are manufactured with specific formulations (Series 17) that comply with USP Class VI and ISO 10993 for biocompatibility. They are used in medical devices, laboratory equipment, drug delivery systems and patient-contact applications.
Dimensional tolerances for medical tubing are tighter than for industrial, and batch traceability is mandatory to comply with medical quality management system requirements.
Medical Silicone Tubing
Extruded VMQ silicone medical tubing (hose) manufactured in an ISO 8 cleanroom. FDA, EC 1935/2004, USP VI, and ISO 10993 approved. High biocompatibili...
View product →Reinforced tubes
For applications requiring resistance to internal pressure, vacuum collapse or mechanical stress, tubes with integrated reinforcement are manufactured. Reinforcement types include textile mesh (polyester, aramid), metal spiral or stainless steel braid.
Reinforcement is incorporated during the extrusion process, becoming embedded between two silicone layers. This maintains tube flexibility whilst significantly increasing pressure and vacuum resistance.
Reinforced Silicone Tubing/Hoses
Silicone reinforced tubing/hoses with polyester, fiberglass, or stainless steel mesh. Resistant to pressure and vacuum. Working temperature from -60 °...
View product →4.3 Cords and solid profiles
Cords are the simplest form of extruded product: solid sections with circular, square or rectangular geometry. Despite their geometric simplicity, they are critical components in many sealing and cushioning applications.
Circular cords
Circular section cords are primarily used to manufacture O-rings by vulcanising the ends, or as filler material in sealing grooves. Available diameters range from 1 mm to over 50 mm.
Square and rectangular profiles
Square or rectangular section profiles are used as flat gaskets, sealing strips or cushioning elements. The ratio between sides can vary widely, from square sections to very flat strips.
Solid Silicone Cords
High-precision extruded solid VMQ silicone cords. Hardness 10-90 Shore A. Compliance with FDA 21 CFR 177.2600, EC 1935/2004, UL94, EN 45545-2, USP VI,...
View product →4.4 Extruded inflatable seals
Inflatable seals are hollow profiles designed to expand radially when pressurised with air. This expansion allows sealing against irregular surfaces or creating hermetic closures that can be released at will.
Designing an inflatable seal requires considering multiple factors: working pressure, required expansion, cavity geometry where it is installed, frequency of inflation/deflation cycles and sealing requirements.
- Door closures for autoclaves and vacuum chambers
- Hatch and industrial gate sealing
- Temporary workpiece fixturing in machining processes
- Tolerance compensation in assemblies
Formulations for inflatable seals must have high tear resistance (Series 1, 7, 10) to withstand fatigue from repeated inflation cycles. Typical hardness is in the 50-70 Shore A range.
Silicone Inflatable Seals
TIXAN’AIR® VMQ silicone inflatable seals. Controlled expansion for dynamic sealing in doors, autoclaves, ovens, and pressurized systems. Inflation pre...
View product →5. Common errors in extruded product specification
Accumulated experience in extrusion projects enables identification of recurring errors that generate problems in production or service. Knowing them helps avoid them during the specification phase.
5.1 Incorrect hardness for the application
Specifying a Shore A hardness without considering actual working conditions is one of the most common errors. Hardness is not just a number: it determines the closure force required, sealing capability, fatigue behaviour and temperature response.
- Hardness too low: Excessive deformation under load, loss of geometry
- Hardness too high: Excessive closure force, loss of sealing on irregular surfaces
- Not considering thermal variation: +3 to +5 Shore A per 50 °C temperature increase
5.2 Geometry poorly conceived for extrusion
Not all geometries are extrudable. Some limitations are physical (the material must flow stably), others are economic (very complex geometries require expensive dies that are difficult to maintain).
- Very thin walls: Filling difficulty and rupture risk. Recommended minimum 0.5-1 mm depending on hardness
- Large thickness differences: Uneven vulcanisation, internal stresses
- Complex closed geometries: Require special mandrels and increase cost
- Very sharp angles: Stress concentration, premature die wear
5.3 Unrealistic tolerances
Specifying moulding tolerances for extruded products generates unnecessary rejections or additional costs for part selection. Extruded products have process-inherent tolerances that must be respected.
Additionally, post-extrusion shrinkage must be considered: silicone profiles may shrink between 2% and 4% after vulcanisation. This effect must be compensated for in die design.
5.4 Poorly specified material
Simply stating "silicone" without specifying the required formulation leaves the decision to the manufacturer, who will optimise for production cost, not for performance in the customer's application.
- Specify: Cure system type (peroxide or platinum)
- Specify: Certification requirements (FDA, EN 45545-2, USP, etc.)
- Specify: Special resistances (chemical, thermal, tear)
- Specify: Colour restrictions if applicable
6. Sectors where silicone extrusion is critical
Silicone extrusion has cross-sector presence in industry, but there are sectors where it is especially critical due to volume, technical demands or regulatory requirements.
6.1 Railway sector
The railway sector is one of the main consumers of extruded silicone profiles. EN 45545-2 requirements for fire, smoke and toxicity behaviour demand specific formulations that maintain mechanical properties under very restrictive conditions.
- Sealing profiles for doors and windows
- Intercirculation gaskets between coaches
- Cable protection profiles and cable glands
- HVAC gaskets and air ducts
Railway
Manufacturing of silicone components and seals with EN 45545 certifications and fire resistance for railway applications.
Explore sector →6.2 Medical and pharmaceutical sector
Medical-grade silicone tubing is essential in diagnostic devices, drug delivery systems, laboratory equipment and patient-contact applications. Biocompatibility, traceability and process control requirements are at their highest.
- Tubing for peristaltic pumps
- Medical suction lines
- Tubing for dialysis equipment
- Short-term implantable device components
Medical
LSR parts, tubes and components certified ISO 13485 and USP Class VI for medical devices.
Explore sector →6.3 Food sector
FDA compliance and certification according to EC Regulation 1935/2004 permit silicone use in food contact. Typical extruded products include tubing for food liquid conveyance, sealing profiles for processing equipment and gaskets for packaging machinery.
Sector Agroalimentario
Productos de silicona aptos para contacto alimentario conforme a FDA y BfR.
Explore sector →6.4 General industry
Beyond regulated sectors, silicone extrusion has presence in virtually all industrial spheres: automotive, appliances, lighting, HVAC, laboratory equipment, industrial machinery and many more.
The combination of thermal resistance, flexibility, durability and ease of forming makes extruded silicone a versatile solution for sealing, protection and fluid conveyance problems in demanding environments.
7. Decision process: is extrusion right for your application?
To determine whether extrusion is the appropriate process, answer these questions:
- Does the part have a constant cross-section? If not → consider moulding
- Are lengths greater than 100 mm required? If yes → extrusion is efficient
- Does annual volume justify dedicated tooling? If not → evaluate standard profiles
- Are required tolerances achievable by extrusion (ISO 3302-1 E1/E2)? If not → consider moulding
- Are there specific certification requirements? If yes → verify formulation availability
If answers predominantly point towards extrusion, the next step is to define the complete technical specification: geometry, material, tolerances, certifications and volumes.
Do you need to validate whether extrusion is the right process?
If you have an application in the design phase and are unsure whether extrusion is the best option, or if you need to define the technical specification for a profile, our technical team can help you make the correct decision before committing to tooling.
We routinely work with engineering departments and consultancies to optimise designs and avoid problems that manifest in production or in service.
Extrusion technical enquiry
Send us your geometry or preliminary specification and we will help you validate the process and define the optimal material.
Contact engineering →The information contained in this article is for guidance purposes. Final specifications for any product must be validated with our technical department based on the specific requirements of each application.
