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Compression limiters meet many design criteria

Edited by the Engineeringtalk editorial team Jan 27, 2005

Spirol Industries has come up with a standard range of rolled split seam compression limiters for post-moulded assembly.

With more assemblies being produced in plastic it is ever more critical that the product can be secured in place with confidence.

Plastic, unlike metal, will compress under the pressure of a bolt and over time will set, resulting in the component becoming loose.

The designer's solution to this has been to design and add a purpose designed but expensive steel compression limiter into the holes of the plastic assembly to protect the plastic from the compressive load generated by the tightening bolt.

Spirol Industries has now come up with a more effective solution with a standard range of rolled split seam compression limiters for post-moulded assembly.

Developed over many years working with the automotive industry worldwide the Spirol range has been designed around common bolt diameters M4 to M12.

Standardisation enables Spirol to provide the customer with reductions in cost through elimination of special tooling charges and improved productivity and also reductions in lead times to meet the short development times required by the industry.

The objective is to keep the compressive stresses below the elastic limit of the plastic.

In practice, as the bolt is tightened the plastic compresses and the stress in the plastic increases until the head of the bolt comes into contact with the compression limiter.

Thereafter the compression limiter will compress at the same rate.

A further major advantage offered by Spirol is that with its unique production techniques it is able to offer any length within a standard diameter range without any tooling costs.

If the designer needs a length of 32.35mm, this is available.

Spirol Industries compression limiters meet many different design criteria.

These include the head of the bolt always seating against the compression limiter under load.

This prevents the bolted joint deteriorating due to plastic creep, which reduces the clamping load.

Also, the compression in the plastic component should not exceed its elastic limit when compressed to seat the bolt against the limiter.

The proof load of the compression limiter should be equal to or greater than the proof load of the bolt.

Finally, the clearance between the maximum bolt diameter and the minimum installed inside diameter of the limiter should be sufficient to compensate for normal misalignment.

To provide for all levels of compressive load, the Spirol split seam range is also available in high carbon steel heat-treated and non heat-treated versions.

For very high loading and moulded in assembly Spirol also have a range of solid compression limiters manufactured from brass for M3 to M10 bolt diameters.

Not only does Spirol have the only standard range in the industry, through their comprehensive Design Guide they also provide the designer with all the information and formulae necessary to design their assembly around the range of limiters.

Along with this, Spirol also offers a free application design service which includes a review of the application and comprehensive component testing.

As well as the standard range of compression limiters, Spirol also produces customer specific parts for unique applications where the standard ranges do not provide all the solutions.