In order to be able to produce rubber seals in large volumes, various standards regulate the quality in these industrial productions to general industrial standards. These general industrial standards define in all cases the risk of errors. The challenge is to build in certainties in the production, finishing and final inspection of critical rubber seals.
If the specification deviates from the standard, the price will also deviate. After all, extra costs have to be incurred in order to realise a deviating higher quality standard. This includes fewer errors, by reducing the chance of errors through structurally tightened – and additional – procedures. Parties should always agree such a higher quality level in advance via a technical specification in combination with a control plan per article. So that production can be set up correctly from the start.
Basic conditions are decisive
In many cases, it is not possible to convert existing production, set up according to standard industrial norms, to a stricter higher quality level because the basic conditions were not realised to begin with. Thus, in addition to a general industrial standard, whereby the production process is qualified according to ISO9001:2015, there is the standard ISO/TS 16949, which is entirely tailored to the requirements of the automotive sector. Although this standard significantly tightens up the number of verification points and reduces the extent to which an error can occur, it still describes the number and extent of errors that must be considered acceptable in the article/delivery.
(Sampling) error reduction
In the industrial environment, a control system based on the available standard AQL (Acceptable Quality Level) is used as standard. This standard has various classes and there are also various levels within these. It is based on a representative sample in which the number of faulty products that may be found in the sample is defined. If this is no longer sufficient, one switches to the system that works with Parts Per Million (PPM). In this system, parties determine the number of errors per million pieces of an article supplied. For example: 500 PPM, which means that 5 articles per 10,000 may have a predefined error.
High bar for critical rubber seals
Then there are the critical seals where customers describe the quality level as ‘zero defects’. The customer who asks for this immediately faces the problem that he cannot check/maintain this standard himself. Simply because he would then have to subject every item to the agreed inspection. The problem that the producer also has. And we have not yet defined the additional costs involved. This ‘zero error standard’ does not exist in practice and can actually only be seen as ‘striving for’ perfection. But that is as far as it goes.
Strict control process for critical rubber seals
There are, however, critical rubber seals that have to be delivered flawlessly at specific points and at the same time still have to be fit for the market commercially. It is customary in our supply chain to have these seals 100% checked at specific checkpoints via a fully automated inspection process. These checkpoints can be, among others:
- Optical inspection of the surface by cameras
- Optical inspection of the surface in stretched condition by cameras
- Pressure test, in which hoses are tested for leakage under overpressure.
- Pressure test, in which the seal is tested for tightness in a copy of the actual construction.
Distinction through top quality
It has been proven that only the application of such a fully automated test/checking installation can bring the risk of errors within the range of the desired ‘zero defects’. It is clear to everyone that this type of fully automated test and inspection rig requires substantial investment. But it does give the product a unique status that suits the image the brand/product wants to have in the market. A unique piece of security for which the consumer is usually prepared to pay a little extra.
NDS-Seals doubles test capacity
NDS-Seals has – after 12 years of working with a semi-automatic pressure testing machine, where the seal is tested for tightness in a copy of the actual construction (see picture above) – placed the order for a new test installation. This will enable us to provide a similar and now fully automated inspection process, including the repackaging of the seals (see image above). This new test installation will be completed in mid-2021, which will more than double our test capacity. Fully automating the process eliminates the potential for human error and increases efficiency, which in turn will reduce costs over time.
Want to know more, contact us!
For more information about our standard and upgraded inspection processes for critical rubber seals, we invite you to contact one of our sales staff.