Bellows

What are bellows?

A bellows is an elastic, often rotationally symmetrically folded protective element that can follow the movements of components and at the same time prevent foreign substances from penetrating into sensitive areas. Due to its geometry, the bellows can be compressed, stretched or bent without losing its protective or sealing function. Bellows are manufactured in a wide variety of geometries, e.g. cylindrical, conical or rectangular. They are often connected at the ends by clamps, flanges or vulcanised Edges attached. Bellows serve not only as protection, but also as a guiding, sealing or compensating component.

Typical types of bellows:

Protective bellows: against dirt, dust and liquids
Compensator bellows: equalisation of movements, vibrations or thermal expansion
Pressure bellows: Sealing against liquids or gases under pressure
Fabric bellows: for high freedom of movement with low weight and high mechanical strength at the same time

Thanks to modern elastomer and composite materials, bellows can also be used reliably at high temperatures, under chemical stress or under vacuum conditions.

Functions & applications of bellows

Bellows fulfil several key protective and functional tasks in technical systems. They protect moving parts, compensate for movements and contribute to the longevity and operational safety of machines and devices:

Protective function: Sealing against dust, chips, moisture and other environmental influences
Motion compensation: Compensation of axial, radial or lateral movements
DampingReduction of shocks and vibrations through elastic behaviour
Guiding and centring: Stabilisation of moving axes or pistons
SealingReliable protection against liquids, gases or oils
Safety function: Protection of operating personnel from moving machine parts

Typical applications:

Mechanical engineering: Protection of spindles, guides and joints in machine tools
Vehicle technology: Axle, steering and shock absorber bellows to protect against dirt, moisture and salt
Hydraulics and pneumatics: Protection of piston rods and Seals from dirt
Medical technology: flexible, hygienic covers and Seals
Energy and environmental technology: Expansion joints in pipe systems to absorb expansions and compensate for tolerances
Robotics and automation: covers for joints and axes in moving systems

Bellows are therefore both functional Sealing elements as well as active protective components that extend maintenance intervals and increase the service life of sensitive mechanics.

Bellows components & materials

Bellows are manufactured from different materials, depending on the temperature, media and environmental influences to which they are to be exposed. The aim is to achieve an optimum combination of flexibility, tightness, chemical resistance and mechanical durability.

Typical materials:

NBRoil and fuel resistant, for hydraulic and machine applications
EPDMOzone, weather and vapour resistant, ideal for outdoor and climatic use
CR (neoprene): good resistance to weathering and ageing
SiliconeTemperature-resistant from -60 °C to +200 °C and biocompatible, suitable for medical and food technology
NRhigh elasticity, very good recovery behaviour
TPE (thermoplastic elastomers): dimensionally stable, recyclable, particularly suitable for series production
Composite materials: Rubber fabric- or Rubber-plastic combinations for increased stability

Bellows can be specifically optimised for mobility, tightness and durability during the design process:

Folding geometries for uniform deformation and load distribution
Reinforced end zones for secure fastening with clamps or flanges
Axial and radial pleat shapes to adapt to different directions of movement
Uniform wall thicknesses to prevent material fatigue
Sealing lips or double pleats for additional sealing effect

Further entries

Elongation at break

The elongation at break indicates how much a material can stretch under tensile load before it tears.

Rubber

Rubber is an elastic material of natural or synthetic origin that is vulcanised into durable components for sealing, damping and technical applications.

Extrusion of rubber

Rubber extrusion is a continuous manufacturing process for rubber-elastic profiles, hoses and seals in which the material is pressed through a moulding die and then vulcanised.

Rapid tooling

Rapid tooling is the accelerated production of functional tools for the rapid production of prototypes or small series under near-series conditions.

Compound

A compound is a customised material mixture of polymer and additives that is specifically tailored to the requirements of a particular technical application.

Series production

Series production refers to the repeated, economical manufacture of similar components in large quantities.

Prototype construction

Prototyping is the targeted production of functional sample parts for early testing and optimisation of geometry, material behaviour and processability before the start of series production.

Abrasion

Abrasion is the mechanically induced surface wear of a material caused by friction and has a decisive influence on the service life and usability of technical components.

HTV silicone: High-temperature curing solid silicone

HTV silicone is a high-temperature curing solid silicone rubber that becomes a permanently elastic material when heated. It combines high mechanical strength with excellent resistance to temperature, ageing and chemicals.

Saturated and unsaturated polymers

Saturated polymers have only single bonds in the main chain and are resistant to ageing, while unsaturated polymers contain double bonds in the main chain and are easier to crosslink; EPDM is a speciality because its double bond is in the side chain.

Sealed seats

Sealing seats are machined contact surfaces that accommodate seals in a form-fit and force-fit manner, thus ensuring permanent media separation protection.

Rubber-Plastic Composite Parts

Rubber-plastic composite parts are hybrid components in which elastic and thermoplastic components are functionally combined - ideal for seals, housings and flexible technical solutions.

Rubber-fabric composite parts

Rubber-fabric composite parts are elastic components with integrated fabric inserts that ensure high tensile strength, dimensional stability and dynamic load-bearing capacity - for example in membranes, seals or conveyor belts.

SBR: styrene-butadiene rubber

SBR is a cost-effective, abrasion-resistant elastomer with good mechanical properties that is mainly used in tyres, seals and general moulded rubber parts.

Valve seal

A valve seal is an elastic component that reliably seals the flow of gases or liquids in a valve. The seal prevents leaks, compensates for pressure and temperature changes and ensures that the valve fulfils its switching, control or shut-off function reliably and permanently.

Oil resistance

Oil-resistant materials permanently withstand aggressive oils and are used in seals, hoses and technical components.

Copolymerisation

Copolymerisation is the simultaneous polymerisation of different monomers to produce polymers with specifically adjustable properties for technical and industrial applications.

Rubber buffers

Rubber buffers are elastic elements that absorb and dampen shocks, oscillations and vibrations. They protect machines, devices and assemblies from mechanical loads, compensate for movements and reduce noise in technical applications.

PPA: Polyphthalamide

Polyphthalamide (PPA) is a dimensionally stable, chemical and temperature-resistant high-performance plastic that is used in particular for precise, media-resistant components and rubber-plastic composite solutions.

Injection moulding

Injection moulding is a precise moulding process for manufacturing complex plastic and rubber parts in which the material is injected into a mould under pressure and cured there.

PPS: Polyphenylene sulphide

Polyphenylene sulphide (PPS) is a high-temperature and chemical-resistant precision plastic that is used in media-exposed and dimensionally critical components, especially in hybrid solutions.

ABS: Acrylonitrile butadiene styrene

Acrylonitrile butadiene styrene (ABS) is a robust, impact-resistant and easy-to-process plastic that is used for housings, interior parts and rubber-plastic composite components with high surface and dimensional stability requirements.

Rubber blank

A rubber blank is a non-crosslinked, mouldable elastomer precursor that is processed in moulding tools to produce elastic rubber parts.

Vacuum cups

Suction cups are suction cups made of elastomer or plastic that cling elastically to the surface and trap the resulting vacuum. Suction cups create an adhesive connection between the gripper and the workpiece by means of negative pressure.

Rubber caps

Rubber caps reliably protect components from dust, moisture and mechanical impact.

Outgassing

Outgassing is the escape of volatile substances from materials and can lead to malfunctions, contamination or optical faults in sensitive applications.

Fillers

Fillers are functional additives in rubber or plastic compounds that specifically influence mechanical properties, processability or cost structure.

Cycle time

The cycle time describes the complete duration of a production run during injection moulding or pressing and is a key parameter for efficiency and output.

Vibration dampers

Vibration dampers reduce vibrations and noise in machines and vehicles.

TPE: Thermoplastic elastomers

TPEs are elastic, malleable materials with rubber-like behaviour that can be thermally processed and recycled like plastics - ideal for flexible seals, handles and hybrid parts.

Heat resistance

Heat-resistant materials retain their properties at high temperatures and are ideal for industrial and technical applications.

PA: Polyamide

Polyamide (PA) is a robust, wear-resistant plastic with very good strength and chemical resistance, which is used in particular in technical components and rubber-plastic composite systems.

CAD modelling

CAD modelling is the digital design of technical components and tools that serves as the basis for production, simulation and prototype development in industry.

Elasticity

Elasticity is the ability of a material to deform under load and then return completely to its original shape - essential for flexible technical components.

Freeze deburring

Freeze deburring is a process for removing burrs, particularly on rubber parts, by cooling and mechanical blasting.

Valves

Valves control, throttle or shut off liquids and gases in pipework, motors and hydraulic systems. They are crucial for process reliability and efficiency.

Assembly Services

Component assembly comprises the assembly of individual components into a functional unit as an assembly.

Rubber recycling

Rubber recycling includes mechanical, thermal and chemical processes for the reuse of vulcanised rubber products as raw materials or additives in new applications.

Sulphur crosslinking

Sulphur crosslinking is a proven vulcanisation process in which rubber is crosslinked with the aid of sulphur to form an elastic, dimensionally stable and mechanically resilient material.

Transfer moulding

Transfer moulding is a rubber moulding process in which the material is pressed from a heated chamber into a closed mould where it is cross-linked under pressure and temperature - ideal for precise components with inserts.

Protective housing

A protective housing encapsulates sensitive components and prevents damage caused by dirt, water or impact.

Synthetic rubber

Synthetic rubber is an industrially manufactured elastomer material that is categorised into main chemical groups and whose properties can be specifically adapted to technical requirements.

Rebound resilience

Rebound resilience describes the ability of a material to return energy after rapid deformation - crucial for dynamic applications such as spring elements or dampers.

Inserts

Inserts are solid components that are embedded in rubber components during processing in order to specifically extend their functionality, stability or fastening options.

Biocompatibility

The proof of biocompatibility proves through standardised tests that a medical device or material does not cause any harmful reactions in the human body.

Fatigue

Fatigue refers to the progressive degradation of material due to repeated mechanical stress and is a key factor in the design of durable technical components.

Rubber-Metal Composite Parts

Rubber-metal composite parts are mechanically stable components in which elastomer and metal are inseparably combined - ideal for bearings, dampers and technical sealing systems.

PES: Polyester

Polyester (PES) is a robust, chemical-resistant thermoplastic that is used both as an engineering plastic and as a fabric reinforcement in rubber composite parts.

EPDM: Ethylene propylene diene rubber

EPDM is a weather, UV and chemical-resistant elastomer with high thermal stability that is used in particular for durable seals, hoses and outdoor applications in industry and construction.

Compression moulding

Compression moulding is a process for manufacturing moulded rubber parts in which a rubber compound is compressed under pressure and heat in a closed mould and vulcanised directly.

Adhesion

Adhesion is the physical holding force between two different materials at their interface and is a key factor for strong, durable connections in technology and industry.

Stainless steel

Stainless steel is a corrosion and temperature-resistant material that is used for durable, hygienic and mechanically resilient components in demanding technical applications.

Medical device regulation (MDR)

The Medical Device Regulation (MDR) is the central EU regulation for medical devices, which places high demands on safety, documentation and market surveillance.

RoHS

RoHS restricts the use of certain hazardous substances in electrical and electronic equipment in order to reduce environmental and health risks. Products may only be sold in the EU if all components comply with the specified limits for listed hazardous substances.

Burr formation

Burr formation occurs in primary forming processes due to material escaping from mould parting surfaces and joints during forming and requires targeted reworking to ensure component quality.

Glass transition temperature

The glass transition temperature (Tg) is the temperature range in which a polymer changes from elastic to glassy and largely determines its low-temperature flexibility.

PP: Polypropylene

Polypropylene (PP) is a lightweight, chemical-resistant thermoplastic with a wide range of applications that is ideal for technical plastic parts and rubber-plastic composite solutions.

Silane crosslinking

Silane crosslinking is a moisture-controlled crosslinking process for plastics and elastomers that enables mechanical stability at moderate processing temperatures.

Aramid / Kevlar

Aramid / Kevlar is an extremely tensile, lightweight and heat-resistant fibre that is used as reinforcement in rubber composite parts, sealing systems and protective applications.

Shaft seal

A shaft seal is a sealing element that seals between a rotating shaft and a housing. It prevents lubricants from escaping and at the same time protects against dirt, dust and moisture.

LSR: Liquid silicone

LSR is a liquid silicone rubber produced on a VMQ or FVMQ basis and processed by injection moulding. The material combines high elasticity, purity and temperature resistance.

PC: Polycarbonate

Polycarbonate (PC) is a transparent, impact-resistant plastic that is used for high-quality housings, visible parts and functional composite components.

Autoclaves

An autoclave is a heatable pressure vessel for the thermal treatment of materials - e.g. for the post-vulcanisation of elastomers or for sterilisation in medicine and technology.

Adhesion promoter

Adhesion promoters are chemical bonding agents that permanently bond rubber with other materials and thus form the basis for resilient rubber composite parts.

HNBR: Hydrogenated NBR

HNBR is a particularly heat-, oil- and ageing-resistant elastomer that is ideal for durable seals and technical components in dynamically stressed applications.

Ageing

Ageing describes the gradual change in material properties due to external influences such as heat, UV radiation or media, which can lead to long-term impairment of function and service life.

EN 9100

EN 9100 explained: an overview of the requirements, areas of application and benefits of certification for the aviation, aerospace and defence industries.

Anti-ageing agent

Anti-ageing agents are functional additives that protect elastomers and plastics from damaging influences such as oxygen, ozone, UV radiation or heat, thereby significantly extending their service life.

Special alloys

Speciality alloys are highly developed metal mixtures for extreme requirements in technology, medicine and industry - especially where corrosion, temperature or load limits of standard materials are exceeded.

FVMQ: Fluorosilicone

FVMQ is a cold-flexible, fuel- and weather-resistant fluorosilicone elastomer that is primarily used in the aviation and automotive industries for demanding sealing applications.

Metal oxide crosslinking

Metal oxide crosslinking is a crosslinking process that is mainly used for chloroprene rubber and produces particularly durable, ageing and flame-resistant rubber parts.

Elastomer rollers

Rubber rollers transmit forces, dampen vibrations and protect surfaces in printing machines, conveyor systems and packaging lines.

Titanium

Titanium is an extremely corrosion-resistant, lightweight and high-strength material that is used in aviation, medical technology and for rubber-metal composite parts in aggressive environments.

Housing and cover with integrated seal

Housings and covers with integrated seals are components in which the sealing function is embedded directly in the plastic or metal part. The sealing function is usually realised as an overmoulded or pressed-in rubber sealing lip. They enable reliable sealing without a separate sealing component and are often used for compact, easy-to-install assemblies.

Tool cleaning

Tool cleaning ensures reliable, clean moulding, protects against burr formation and extends the service life of tools in series production.

Calendering

Calendering is a rolling process in which rubber or plastic compounds are rolled between heated rollers. In addition to the manufacture of finished products such as rubber mats, it is primarily used in the production of rubber blanks.

Elongation

Elongation refers to the change in length of a material under tensile load and is a key parameter for assessing the elasticity and breaking strength of technical materials.

Bearing bolt

A bearing pin is a cylindrical connecting element that serves as a pivot or swivel axis for moving components. It transmits forces, guides movements and secures the position of components within a bearing or a joint connection.

GRP: Glass fibre reinforced plastic

GRP (glass fibre reinforced plastic) is a robust, lightweight composite material made from glass fibres and a plastic matrix that is used in a wide range of applications in industry, construction and mobility.

Azo and urea compounds

Azo and urea compounds are speciality chemicals that are used as blowing or cross-linking agents in rubber processing - especially for foams and friction-active components.

Primer

Primers are adhesion-promoting primers that improve the adhesion between rubber, plastic or metal and ensure a permanent bond in composite and coating applications.

Bellows

A bellows is an elastic component with a corrugated, accordion-like geometry that absorbs movements, changes in length or swivelling movements without losing its protective or sealing function. It protects sensitive components such as joints, shafts or guides from dirt and moisture and at the same time enables a flexible, permanently movable connection.

IIR: Butyl rubber

Butyl rubber (IIR) is a particularly gas-tight, weather- and chemical-resistant elastomer that is mainly used in tyres, seals and membranes.

CR: Chloroprene rubber

Chloroprene rubber (CR) is a versatile, weather- and flame-resistant elastomer that is often used for seals, hoses and technical components for indoor and outdoor use and is also known as neoprene.

Keyboard and switch covers

Keyboard and switch covers are elastic protective components that protect keys and operating elements from dust, moisture and dirt. At the same time, they maintain the operating function by transmitting the actuation feel and enabling reliable sealing.

Engine damper

Engine dampers are elastic elements that absorb vibrations and shocks between the engine and the vehicle or machine frame. They reduce vibrations, protect adjacent components from stress and improve the noise and running behaviour of the entire system.

Aluminium

Aluminium is a lightweight, corrosion-resistant material with high thermal conductivity that is used in a variety of ways as a construction material and support element in technical components.

Shore hardness

The Shore hardness measures how deeply a test pin penetrates a material and thus provides information about its degree of hardness - a decisive factor in the selection of elastic and technical materials.

Structural steel: S235 and S355

Structural steel (S235, S355) is a robust, easily weldable construction steel that is used as a stable carrier material in load-bearing structures, machine components and rubber-metal composite parts.

Seals

Seals prevent leaks in pipework, motor and system components. They also compensate for manufacturing tolerances and protect processes against pressure, temperature and media stress.

Peroxide crosslinking

Peroxides are reactive cross-linking chemicals that produce stable, temperature- and chemical-resistant elastomer structures without sulphur bridges in rubber processing.

Molded Rubber Parts

Moulded rubber parts are elastic components made from vulcanised rubber by pressing, transfer moulding or injection moulding. They are manufactured according to drawings and are used as sealing, damping or functional elements in technical applications.

ISO 9001

ISO 9001 is the world's most important standard for quality management. It defines how companies manage their processes so that products and services deliver consistently high quality and fulfil customer requirements.

Grommets

Grommets are ring- or disc-shaped protective inserts that are inserted into openings or edges to allow cables to pass through safely. Grommets protect cables and hoses from sharp edges, seal feed-throughs and can be quickly inserted into holes or gaps.

FKM: Fluororubber

FKM is a heat- and chemical-resistant high-performance elastomer for seals and components in extremely demanding industrial applications.

Stress cracking

Stress cracking is the gradual formation of cracks in plastics due to the interaction of stress and chemical media - often with critical consequences for component safety.

Pressure resistance

Pressure resistance is the resistance of a material to compressive stress and is a decisive factor for the function and service life of technical components under mechanical stress.

brass

Brass is an easily machinable, corrosion-resistant copper-zinc alloy that is widely used as a functional and decorative metal - including in rubber-metal composite parts, fittings and electrical components.

Express Services

Express production refers to the particularly fast production of prototypes, tools or small batches and accelerated development projects with drastically reduced delivery times.

Toolmaking

In elastomer production, toolmaking refers to the development and manufacture of high-precision tools that are used in the production of rubber, plastic and composite parts for moulding.

Tool costs

Tool costs are the expenses for the manufacture of tools and have a significant influence on the profitability of series production.

Rubber expansion joints

Rubber expansion joints are flexible connecting elements that compensate for movements, vibrations and pressure surges in pipework. Thanks to their elastic structure, they can absorb changes in length, lateral displacements and angular movements and thus protect connected system components from mechanical stress, vibrations and tension in the pipework system.

Cold resistance

Cold resistance describes the ability of a material to remain functional and elastic at low temperatures - crucial for seals and elastomer components in outdoor or cold applications.

Deburring

Deburring is the process of removing burrs from components to ensure the function, appearance and safety of technical products.

Caoutchouc vs. rubber vs. elastomer

Rubber is the raw material, rubber is the end product created by vulcanisation, and elastomer is the superordinate material class of elastic polymers.

Residual materials

Residual materials are recyclable material residues from production that can be specifically collected and fed back into the production cycle to conserve resources.

NBR: Acrylonitrile butadiene rubber

Acrylonitrile butadiene rubber (NBR) is an oil and fuel-resistant elastomer that is frequently used for seals, hoses and technical moulded parts in mechanical engineering and vehicle construction.

Sealing lips

Sealing lips are flexible sealing elements that securely enclose media and remain reliably functional even in the event of rotation or pressure fluctuations.

DIN ISO 3302-1

DIN ISO 3302-1 defines the general tolerances for moulded rubber parts and is an international standard for ensuring dimensional accuracy in elastomer processing.

RTV silicone: Room temperature curing solid silicone

RTV silicone is a room temperature curing silicone rubber that cures without heat or pressure. It is particularly suitable for sealing, bonding, potting and mould making and is less strong and temperature-resistant than HTV and LSR.

ISO 14001

ISO 14001 explained: an overview of the requirements, areas of application and benefits of the international standard for environmental management systems.

ISO 13485

ISO 13485 explained: an overview of the requirements, areas of application and benefits of certification for medical technology.

Tensile strength

The tensile strength is the maximum stress that a material can withstand under tensile load and is a key parameter for the mechanical strength of elastomers.

NR: Natural rubber

Natural rubber (NR) is a highly elastic, tear-resistant elastomer made from renewable raw materials that is primarily used in dynamically stressed components such as tyres, dampers and conveyor belts.

REACH

REACH is an EU regulation for the registration, evaluation and regulation of chemical substances in order to better protect people and the environment. Companies must prove the safety of the raw materials they use and inform customers if their products contain substances of concern.

Profile seal

A profile seal is a seal with a defined cross-sectional shape (round, rectangular, hollow or with a complex profile) that ensures a seal between two components. It is made from elastomers and is used wherever gaps, movements or unevenness need to be compensated for.

LABS (paint wetting impairment substances)

LABS are substances that interfere with the wetting of paints and must therefore be strictly avoided or tested in paint-critical applications.

Suction pad

Suction cups are cup-shaped suction cups made of elastomer or plastic that cling elastically to the surface and trap the resulting vacuum. Suction cups create an adhesive connection between the gripper and the workpiece by means of negative pressure.

CFRP: Carbon fibre reinforced plastic

CFRP (carbon fibre reinforced plastic) is an ultra-light, extremely strong composite material made of carbon fibres and a plastic matrix that is used in highly stressed lightweight construction applications.

Degreasing

Degreasing is an essential cleaning step for removing residues from components to ensure optimum adhesion during vulcanisation, bonding or coating.

PU: Polyurethane elastomer

PU elastomers are dimensionally stable, abrasion-resistant plastics with high mechanical strength that are ideal for rollers, seals and shock absorbers in heavy-duty industrial applications.

IRHD hardness (International Rubber Hardness Degree / ball indentation hardness)

IRHD hardness is an internationally standardised method for measuring rubber hardness using ball pressure and is particularly suitable for small or sensitive elastomer components.

FDA conformity

FDA compliance means that a material or product meets the requirements of the U.S. Food and Drug Administration and is safe for contact with food, drinking water or pharmaceutical applications. Only approved ingredients may be used and the material must not release any substances of concern into the medium.