Bars, sheets and springs in polyurethane
Perfecting Performance by EXSTO
Polyurethane springs are elastic elements for tools and moulds: here our selection of Jumpy springs.
Polyurethane elastic springs
Below some of the main strenghts of Jumpy springs:
- Functional safety
- Extended life
- Low maintenance
- Reduced operating costs
The high quality of Jumpy elastic components comes from the special chemical structure of the polymers used in their manufacture.
Jumpy elastic springs have excellent mechanical-dynamic properties thanks to the special chemical-morphological structure of the polymers used:
- High tear resistance
- Optimum oil resistance
- Continuous dynamic functioning at 80-90 ºC
- Low heat accumulation due to internal friction
- High breaking loads
- Elongation 500-600 %
- Low permanent deformation
- High elastic performance
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The purpose of this section is to help technicians select the correct size of elastic component.
In order to make the most of Jumpy elastic components we recommend the following advice:
- Adjust the deformation of the Jumpy component within the limits allowed (25-30% of the original height)
- The length of the elastic component must not exceed twice its diameter to avoid load loss due to deflection
- Select the frequency of deformation in relation to the percentage of deformation to avoid dangerous overheating
- Ensure proper lubrification of the pilot pin and all work surfaces to reduce friction at the polyurethane-metal interface.
POLYURETHANE SPRINGS CAN BE MOUNTED IN TWO WAYS:
- A) PARALLEL MOUNT
This kind of mounting can double or triple the force necessary for deformation (see Fig.1)
Total load P = a + b
Total deformation C = C1 = C2
- B) SERIES MOUNT
When it is necessary to double or triple the deformation of the unit without varying the force of deformation (see Fig.2)
Total load P = a = b
Total deformation C = C1 + C2
With both types of mounting it is necessary to allow sufficient space for the lateral expansion of the elastic components during the deformation. To calculate the space necessary it is important to remember that d1 = 1.33 d (see Fig.3)
The deformation characteristics of Jumpy elastic components are a function of the percentage of deformation to be obtained, of the ShºA hardness of the elastomer and the form factor.
The form factor is obtained by calculating the ratio between the load-bearing surfaces and the surfaces free to deform (see Fig.2).