Have seals made to measure – requirements, tolerances and processes

Custom-made seals are used wherever standard solutions reach their limits. In industrial applications, even the smallest deviations often determine whether something functions or fails. Individual geometries, specific media or changing loads require solutions that are precisely tailored to the intended use.

When you have seals made to measure, an interplay of design, material selection and manufacturing technology emerges. Each of these levels influences the subsequent sealing effect. The course is already set during the planning phase: which forces act, which media are used, which temperatures occur and how high the mechanical load is.

Straight to implementation: Send us your drawing or describe your application – you will receive a technically suitable solution including a material recommendation and a manufacturing proposal.

Having seals made to measure – briefly explained

Custom-made seals are individually tailored to your application. Based on medium, temperature, pressure and geometry, a suitable material is selected and the seal is manufactured precisely. The result: higher tightness, longer service lives and lower failure risks in operation.

When custom-made seals make sense

Individual seals are needed above all when:

• standard dimensions do not fit
• special media resistance is required
• high temperatures or pressures occur
• complex geometries are present

Typical areas of application are mechanical engineering, plant engineering, the chemical industry and food technology.

Technical requirements for custom-made seals

The technical design of a seal determines tightness, service life and operational safety. A holistic consideration of the operating conditions is decisive: medium, temperature, pressure, installation space, relative movement and installation state. Even small incorrect assumptions in one of these points lead in practice to leaks, premature wear or material damage. A clean specification combines material properties, geometry and tolerances into a functional overall system.

For the design, standards, safety factors and economic aspects are taken into account alongside the operating parameters. This results in a seal that works stably in real operation and can be manufactured reproducibly.

Media resistance

Chemical resistance determines whether a material remains stable in contact with the medium. Oils, fuels, acids, alkalis or gases act differently on elastomers and plastics. Swelling, extraction of additives or embrittlement change the geometry and thus the sealing effect. A material-appropriate selection – for example NBR for oil-based media, EPDM for water and weather or FKM for aggressive chemicals – ensures that volume change and ageing remain within the permissible range. In addition, diffusion effects and permeation with gases must be taken into account.

Temperature range

Temperature influences elasticity, resilience and ageing. Below the glass transition temperature, elastomers lose their flexibility; above the continuous service temperature, ageing accelerates. Alternating loads due to temperature cycles lead to material fatigue. Materials such as silicone or FKM cover higher temperature ranges, while EPDM works stably in water and steam applications. The design takes into account continuous and peak temperatures as well as heating and cooling rates.

Pressure conditions

Pressure acts directly on the contact pressure of the seal. As pressures rise, extrusion risks in gaps increase and so do the requirements on resilience. The geometry (e.g. sealing lips, support elements) and the hardness of the material are selected so that sufficient surface pressure is created without excessive deformation occurring. In dynamic systems, pressure surges and pulsations must also be taken into account.

Mechanical load

Relative movements between sealing surfaces generate friction and wear. Rotary, sliding or oscillating movements require adapted materials and surfaces. Shore hardness, tensile strength and abrasion resistance determine the service life. Edge radii, surface roughness of the mating surfaces and lubrication significantly influence tribological behaviour. An adapted design reduces friction and prevents edge loading.

Installation space and assembly

The available installation space defines the profile, cross-section and compression of the seal. Too high a compression level leads to overloading, too low a one to insufficient sealing effect. Assembly conditions such as lead-in chamfers, lubrication and anti-rotation protection are part of the design. For flat gaskets, flange geometry and bolt preload play a central role in uniform surface pressure.

Standards and approvals

In many applications, binding standards and directives apply. These include DIN and ISO standards for dimensions and testing as well as industry-specific requirements such as EU 1935/2004 for food contact. The selection of suitable materials and test methods ensures conformity and reduces the risk of complaints in operation.

Materials at a glance

Alongside classic elastomers, different types of seals are used depending on the application, including flat gaskets, profile seals, O-rings or complex seal cut pieces. The choice of material determines function and service life.

The choice of material determines function and service life. An overview of the most important materials:

Material	Properties	Typical application
NBR	oil-resistant, cost-efficient	hydraulics, mechanical engineering
EPDM	weather-resistant	outdoor areas, water
FKM	chemical-resistant	chemicals, automotive
Silicone	temperature-stable	food, medicine
PTFE	universally resistant	aggressive media

Further details can be found in the section custom rubber seals and cut pieces.

Tolerances for custom-made seals

Tolerances directly determine the sealing effect.

Typical values:

• Punching: approx. ±0.3 to ±0.5 mm
• Waterjet: approx. ±0.1 to ±0.3 mm
• CNC: approx. ±0.05 to ±0.1 mm

Tighter tolerances increase functionality but also increase manufacturing effort.

Manufacturing processes for custom-made seals

The manufacturing process depends on geometry, material and quantity. Punching is suitable for large series with simple shapes, while waterjet cutting is used particularly flexibly for individual parts and complex contours.

CNC processes enable the highest precision and are used in technical applications with tight tolerances. Turning processes are used for rotationally symmetrical components, while injection moulding or compression moulding work economically for large quantities. In practice, the optimal solution often results from a combination of these processes.

Standard solution vs. custom-made

Criterion	Standard	Custom-made
Fit accuracy	limited	exact
Flexibility	low	high
Area of application	simple	complex

How manufacturing proceeds

1. Define requirements
2. Select material
3. Create or check drawing
4. Produce sample
5. Produce series
6. Check quality

Avoiding typical mistakes

• dimensions defined unclearly
• unsuitable material selected
• operating conditions missing
• tolerances not taken into account

Quality assurance and testing

Quality assurance begins already in the quotation and design phase and continues throughout the entire manufacturing process. Based on the defined requirements, inspection plans are created that specify which characteristics are checked at which intervals. These include in particular dimensional properties such as inner and outer diameter, material thickness, flatness and function-relevant geometries.

During production, suitable measuring equipment and methods are used to detect deviations at an early stage. For higher requirements, statistical methods are used to ensure process stability and reproducibility. In parallel, material tests are carried out, for example to determine hardness, tensile strength or resistance to defined media.

For safety-relevant applications, functional tests are additionally carried out. These include pressure and leak tests under realistic conditions, in which the seal is mounted in a test fixture and subjected to defined loads. This allows behaviour in later use to be reliably reproduced.

Costs, delivery times and ordering

The costs of custom-made seals result from a combination of several factors. The material chosen, the complexity of the geometry, the manufacturing process used and the desired quantity are decisive. Elaborate contours, tight tolerances or special materials increase the manufacturing effort, while larger series can be implemented more economically through economies of scale.

The choice of process also influences the cost structure. Processes such as punching are particularly efficient for high quantities, while CNC or waterjet processes offer advantages for smaller batch sizes and complex shapes. In many cases, the most economical solution is determined as part of the technical coordination.

The delivery time is closely linked to the scope of the project. Simple cut pieces or near-standard geometries can often be realised within a few working days. Complex components, material procurement or series production with toolmaking lead to correspondingly longer lead times. Clarifying all technical details at an early stage significantly speeds up the entire process.

In practice, it is evident that a structured enquiry has the greatest influence on speed and result. Clear specifications reduce queries, shorten the project duration and lead to a solution that works directly in use.

Practical examples

A mechanical engineering company needs a flat gasket for a special housing with increased oil pressure. Standard parts lead to leaks and unplanned downtime. A custom-made NBR seal with optimised material thickness and adapted geometry keeps the system permanently tight. Result: reduction of failures and longer maintenance intervals.

In the chemical industry, an FKM seal replaces an existing solution that was damaged by aggressive media. The new design takes into account temperature, pressure and chemical resistance. Result: significantly extended service life and fewer replacement cycles.

A food company relies on silicone seals with the corresponding approval according to EU 1935/2004. The custom-made solution meets hygienic requirements and ensures reliable sealing at changing temperatures.

In conclusion

Custom-made seals create reliability in applications where standard solutions reach their limits. The combination of precisely fitting geometry, suitable material and coordinated manufacturing process reduces failures and increases the service life of systems.

Companies benefit in particular when the design is carried out at an early stage. A precise definition of requirements leads to stable processes, lower maintenance costs and predictable quality over the entire life cycle.

Experience from projects shows: the biggest lever lies in a clean specification at the beginning. Those who work clearly here avoid later adjustments and achieve a working solution directly.

Request a seal now: Send a drawing or describe your application and receive a suitable solution directly.

FAQ

When is a custom-made seal worthwhile?

A custom-made seal is worthwhile for special requirements regarding geometry, medium, temperature, pressure or load.

Which types of seals can be made to measure?

Possible options include flat gaskets, O-rings, profile seals, moulded seals and individual seal cut pieces.

What information is needed for an enquiry?

Dimensions, drawings, CAD data, desired material, medium, temperature range, pressure conditions and the desired quantity are helpful.

Which materials are suitable for custom-made seals?

NBR, EPDM, FKM, silicone, PTFE and other technical materials are frequently used. The selection depends on the operating conditions and medium.

How long does manufacturing take?

Simple cut pieces are often possible within a few working days. Complex geometries, special materials or series production require more time.

What influences the cost of a custom-made seal?

The costs depend above all on material, geometry, tolerances, manufacturing process and quantity.

Which tolerances are possible for custom-made seals?

The achievable tolerances depend on the manufacturing process. CNC processes enable particularly precise results, while punching is above all economical for series.

Which standards and approvals can be relevant?

Depending on the application, DIN, ISO or food-law requirements such as EU 1935/2004 can be relevant.

Our rubber sheets

For industry and trade, we offer a wide variety of rubber sheets.

SBR rubber sheet

Our high-quality SBR rubber sheet (styrene-butadiene rubber) is the solution for numerous industrial and commercial applications. This rubber sheet is made from first-class styrene-butadiene rubber and stands out due to its excellent physical properties.

EPDM rubber sheet

Discover the versatility and reliability of our EPDM rubber sheet, which is made from ethylene propylene diene monomer (EPDM). This high-quality elastomer solution has been specially developed to meet the most demanding industrial and commercial applications.

NBR rubber sheet

The NBR rubber sheet is a high-quality industrial product that has been specially developed for applications requiring excellent resistance to oils, greases and various chemicals.

Viton rubber sheet

The Viton rubber sheet is a high-quality technical product that is used for a wide range of industrial applications. Made from fluoro rubber (FKM), it offers outstanding properties that make it the ideal choice for extreme conditions.

FKM rubber sheet

The FKM rubber sheet is a high-quality technical product that is ideal for use in demanding industrial applications. Made from fluoro rubber (FKM), it stands out due to a wide range of outstanding properties that make it the optimal choice for extreme operating conditions.

Silicone rubber sheet

The silicone rubber sheet is a first-class technical product that has been specially developed for applications placing high demands on temperature resistance and flexibility.

PUR rubber sheet

The PUR rubber sheet, made from high-quality polyurethane, is a technically advanced product that has been developed for applications placing the highest demands on abrasion resistance and mechanical load capacity.

Neoprene rubber sheet

The Neoprene rubber sheet, made from high-quality chloroprene rubber (CR), is a versatile technical product that is ideal for a wide range of industrial and commercial applications.