TECHNICAL SUPPORT - BELLOWS

Development and production of components for machine tools since 1949.

Classification - Bellows

Bellows are essential elements for protection from dust, chips, humidity and moving chemicals.

Rubber bellows – Available in the following versions:
- Cylindrical: with collars of the same diameter
- Conical: with collars of different diameters
Fabric bellows (made without mold, suitable for long strokes and covers of guides and worm screws)

Material and thermal compatibility - Bellows

Each material used for the production of bellows has specific characteristics of chemical resistance and temperature ranges. Below is a comparison table:

Material	Typical chemical resistance	Temperature range
NBR Nitrile Rubber	Mineral oils, greases, light fuels	-30°C / +100°C
EPDM	Hot water, steam, atmospheric agents, UV	-40°C / +140°C
Neoprene	Moderate oils, atmospheric agents	-35°C / +110°C
Silicone	High temperatures, sterilization, food	-60°C / +200°C
FKM (Viton®)	Oils, solvents, fuels, aggressive chemical agents	-20°C / +210°C
Natural rubber	Abrasion, flexibility, air resistance	-40°C / +80°C

Assembly - Bellows

To ensure the durability and effectiveness of the bellows, it is important to respect some fundamental rules during installation:

Collars can be secured by metal or plastic clamps, or in machined housings
The diameter of the collar can be slightly extended to fit the attachment point
The flange fixing is suitable for:
- Rubber coated fabric bellows
- Some special rubber versions
Always check that the minimum and maximum bellows stroke is compatible with the machine movements
At maximum extension, the coils must not retract inwards, to avoid damage.

Troubleshooting - Bellows

Problem	Possible cause	Recommended action
Laceration	Excessive extension or abnormal torsion	Check the compatibility of the bellows with the machine movements
Laceration	Cutting from a rigid body or external object	Check for sharp objects in the running area
Hardening or cracks	Aging of the material due to exposure to air and direct light	Check UV exposure and service life – prefer EPDM or CR for outdoor applications

Hardening or cracks	Aging of the material by temperature	Check the thermal range of use
Swelling	Chemical reaction	Check the compatibility between the bellows material and external agents

Notes - Bellows

Fabric bellows can be customized in shape, fastening and materials.
For bellows subjected to aggressive environments or complex movements, contact our support for suggestions on materials and geometries.

Dimensional tolerances - ISO 3302-1 - Bellows

The ISO 3302-1 standard represents the international reference standard for defining dimensional tolerances rubber products, such as gaskets, seals and moulded parts.

Its objective is to ensure the consistency, reliability, and correct functioning of components, taking into account the specific characteristics of elastomeric materials and production processes.

The directive introduces different tolerance classes (M1, M2, M3 and M4), which allow the most suitable precision level to be defined based on the application, the context of use and the functional requirements of the component. A correct interpretation of classes and tolerances is fundamental to avoid critical issues during assembly, operation and long-term durability.

For this reason, in addition to the regulatory reference, Technical support plays a central roleSupporting the client in reading the standards, choosing the most suitable tolerance class and evaluating technical solutions allows for the reduction of errors, optimisation of the project and assurance of reliable performance.

Below are the main differences between tolerance classes and the reference table, useful as a technical guide for informed evaluation.

Class M1
It is the class with the most restrictive dimensional limits, used when high levels of precision and repeatability are required, typically in technically critical applications.

Class M2
It represents a good compromise between accuracy and production feasibility and is the most used in standard industrial applications, where reliability is required without excessively stringent tolerances.

Class M3
It allows for wider tolerances and is intended for components with less stringent functional requirements, where slight dimensional variations do not affect overall performance.

M4 Class
It is the class with the most permissive tolerances, generally adopted for non-critical or highly deformable elements, for which dimensional accuracy is not a determining factor.

Nominal size (mm)	Tolerance Class M1 (mm)	Tolerance Class M2 (mm)	Tolerance Class M3 (mm)	Tolerance Class M4 (mm)
0.00 - 4.00	± 0.08	± 0.10	± 0.15	± 0.25
4.00 - 6.30	± 0.10	± 0.12	± 0.20	± 0.25
6.30 - 10.00	± 0.10	± 0.15	± 0.20	± 0.30
10.00 - 16.00	± 0.15	± 0.20	± 0.25	± 0.40
16.00 - 25.00	± 0.20	± 0.20	± 0.25	± 0.50
25.00 - 40.00	± 0.20	± 0.25	± 0.35	± 0.60
40.00 - 63.00	± 0.25	± 0.35	± 0.50	± 0.80
63.00 - 100.00	± 0.35	± 0.40	± 0.60	± 1.00
100.00 - 160.00	± 0.40	± 0.50	± 0.70	± 1.30
160.00 -	± 0.30%	± 0.40%	± 0.50%	± 0.70%