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Avanex EGTST

We hope you enjoy the latest edition of our Engineers Guide To Spring Technology. We often find that sharing common issues and challenges can help designers and engineers in their work.

In this edition we take a look at detangling springs and also the different forms of protective finishes that are available. We are also keen to introduce our new Knowledge Hub, our new online resources tool.

Please let us know if there are any other design problems or questions that you would like answering.
Avanex EGTST

Avanex EGTST New - Knowledge Hub

We have been busy creating a new resources tool online for designers and engineers. Our new Knowledge Hub contains all kind of useful information such as articles on reducing particulate, our Spring Glossary and insight into the different end types of Compression Springs. We are also keeping all previous editions of the Engineers Guide To Spring Technology for you to refer to. We will be updating this each month with content from the teams at Advanex Europe.

Click here to explore. Avanex EGTST Avanex EGTST Detangling Springs

Spring Tangling can be a major issue for customers, not only for those using automated production lines but even hand assembly can be made substantially more difficult if the springs have become tangled.

Many springs and wire forms have the potential for tangling and become interlocked. Spending time solving this issue can be expensive, time consuming and damaging to the components.

The major problems with tangled springs are:
  • Deformation - Potential to deform the original spring shape
  • Production Delays – downtime sorting springs
  • Damage – potential to cause damage to the production equipment
In a lot of cases, the risk of tangling can be reduced or removed through, either a design option, or various packaging options.

Click here to download full article. Avanex EGTST Protective Finishes

Despite the availability of spring materials in many different grades of stainless steels, nickel alloys and copper alloys, most springs are still specified in spring steel, due to its relatively low price. Often though, customers will need some form of coating to be applied, normally to give a degree of corrosion protection. This will add to the cost, although the combination of spring steel and a protective finish will normally be more cost-effective than a more exotic material type on its own.

Avanex EGTST Electroplating

This is by far the most common type of coating, and it's normally zinc that is used. The benefits are the low cost and the effectiveness;- zinc essentially sacrifices itself due to its position in the galvanic series relative to iron. Because of this, the zinc will offer protection to the steel from corrosion, even if the coating is missing in places.

The downside is the risk of hydrogen embrittlement. During the plating process, hydrogen is formed, some of which gets absorbed into the surface of the steel. This hydrogen will render the steel brittle, and liable to failure. To counter this, the springs should be baked immediately after plating, at around 200°C for at least 8 hours, to drive out as much hydrogen as possible. For routine applications this is usually satisfactory, and the incidence of embrittlement failure is rare if the proper post-plating heat treatment has been carried out. If the application is critical in nature however, we wouldn't recommend using an electroplated type of finish.

Other elements can be applied by electroplating, e.g. tin, nickel, silver, gold, cadmium. The latter is now prohibited for all but very special applications, due to its toxicity. Tin and nickel are sometimes used where good electrical conductivity is required, as are silver and gold, albeit with the obvious disadvantage of high cost.

Avanex EGTST Pre-Plated Wire

A metallic coating can also be achieved by using a pre-plated wire. This is usually achieved by drawing the wire through a bath of molten metal, in which case there is no risk of hydrogen embrittlement. Zinc is the most common coating and wire treated in this way is commonly referred to as 'galvanised'. The advantages of this process are low cost, and full coverage of the wire surface - even between closed coils of the finished spring. It should be mentioned that the cut ends of the wire will not be coated, although this is rarely considered to be a serious drawback.

Avanex EGTST Organic Zinc Flake Coatings

These coatings give excellent corrosion resistance with no risk of hydrogen embrittlement. They basically consist of flakes of zinc in a suspension of resin, which can be applied by dipping and spinning, or by spraying, before stoving at about 200°C. We recommend the use of these finishes where the consequences of spring failure are serious. The cost is a little higher than zinc electroplating but is easily justified in critical applications.

Avanex EGTST Powder Coating

This is a very useful finish for larger springs. A large range of colours can be achieved for corrosion resistance, decorative purposes, or for identification, and the paint adheres very tightly to the substrate. The thickness is substantial however, and is therefore not always suitable for smaller springs. The price is also a disadvantage; the coating costs can be very significant compared to the cost of the uncoated spring.

Less Common Coatings

There are a variety of rarer coatings available, such as zinc or manganese phosphate (cheap, limited corrosion resistance but it provides a good substrate for painting or oiling), black oxide (no corrosion resistance; for cosmetic effect only), coloured dye (used for part identification only), and many others. Customers are invited to consult our Technical Department for advice on the right coating for their springs.
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