Round cap / protective cap

In your role as a strategic buyer, as a contact person in the design and development department, as a technician, quality engineer, production or operations manager, you are involved in other areas of the company, detailed information about round caps, especially about Available dimensions from existing tools and Assembly instructions interested. In the following knowledge area we offer you Design recommendations, installation instructions, Selection criteria and dimension tables for PVC round caps.

Design instructions

To ensure that the PVC round caps do not lose their grip on your component, we recommend using protective caps with an inner diameter that is approx. 0.5 mm smaller than the outer diameter of the round area to be protected. This rule of thumb for the undersize applies to medium diameters. If the round component dimensions to be protected are significantly larger, the ideal undersize of the round cap may be larger (e.g. up to 1.0 mm), or smaller (e.g. 0.1 - 0.2 mm) if the dimensions are significantly smaller.

From the point of view of a designer who is about to create a drawing of this standard protective element based on our design instructions, this statement may seem non-binding in connection with the FMEA, the incoming goods inspection to be planned, the identification and attributive random sample inspection for dimensional accuracy of the protective caps to be produced. But there are understandable reasons for this.

Why is it advisable to concretise the drawing of a round cap only after sampling?

The captive fit of a round cap depends not only on the selected undersize, but also in particular on the condition of the area of the component to be protected. In addition to the fact that the inner contour of the round cap moulds itself very well to a smooth, polished surface and generates a high level of static friction, it is also the vacuum that forms when the cap is pulled off a round solid material that makes it difficult to accidentally strip the round cap off the component. No vacuum is formed in the case of uncapped round tubes.
The threads of fastening elements, such as those of threaded screws or, for example, the threads of the spirals of a drilling tool, act like undercuts in the pull-off direction. However, an additional effect of a vacuum forming as described above will also not occur due to the geometry.
This means that only the preload achieved (equivalent to the selected undersize of the mounted cap) is effective, which may have to be increased after appropriate practical tests in order to reliably guarantee the desired loss-proof hold. The drawing would then have to be adapted again.

Which undersize should be considered when requesting a new round cap application?

For the above-mentioned reasons, we recommend specifying the outer diameter of the round component to be protected in addition to the desired inner length H of the protective cap when enquiring about round caps.

We clarify in advance in a personal dialogue with youwhich Priorities and wishes need to be considered from your point of view. Only then do we create a meaningful offer about the Design customised to your application of the round cap. To the enquiry.

Assembly instructions

PVC protective caps manufactured using the dipping process are produced undersized. Due to the process, round caps have larger Wall thickness tolerances  as Injection moulded parts. If manual fitting of the PVC round caps is not so easy, the fitting process can be significantly improved by heating the round caps to a maximum of 50°C.

What influence do colours have on the properties of PVC?

Dark colours such as black and anthracite grey are extremely UV and weather resistantbecause the UV-stable Colour pigment carbon black has a high percentage share in the formulation of the colour batch used.
Round caps with bright coloursin the practice of Outdoor weathering the PVC material must be protected by Addition of a UV stabiliser UV-stable to the formulation.

As both the liquid base material (PVC plastisol) and the UV stabiliser have a yellowish inherent colour, this has a minimal effect on the accuracy of the RAL colour tone. Using the protective caps above the recommended continuous use temperature leads to a yellowish discolouration, especially with light colours. For the aforementioned reasons, we confirm for our Standard colours and special colours only similar to the RAL number.

Can PVC round caps be manufactured and supplied cost-effectively from existing moulds?

Due to the very high number of over 6,000 dipping moulds available for the production of an almost complete range of standard dimensions, we would like to be considered as a Europe's leading manufacturer for PVC round caps and Rectangular caps want to call it.

For our customers operating internationally or based abroad, we have developed a Comparability of the dimensions in [mm] with other nationally applicable standards created.