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Improve the life span, gloss and anti-corrosion capabilities of aluminum molds

Posted by: Alan Xia 2023-11-22 Comments Off on Improve the life span, gloss and anti-corrosion capabilities of aluminum molds

Mold House News: Aluminum molds are a hot topic that everyone in the mold industry is very concerned about. Using aluminum as a more cost-effective method to produce molds has many advantages and can further improve the competitiveness of enterprises. Because the advantages are very obvious, the mold manufacturing cycle is shortened, thereby reducing production costs. In addition, this mold has better thermal conductivity, which means that the production cycle can be greatly shortened. In summary, it is timely to discuss the issues surrounding electroplated aluminum molds for those considering the use of these types of molds. History and applications

The use of aluminum molds in injection molding processes is not entirely a new concept. Initially, prototype molds were generally precision 3d printing aluminum molds, and the automotive industry has been using such molds for many years, and it has gradually become popular among companies outside the automotive industry.

More and more customers are asking the question: How to extend the service life of these molds so that they can be suitable for limited production? As this trend grows, customers are beginning to explore aluminum molds as real production tools and even asking more questions, such as:

  • (1) What level of final surface finish should the mold need to be plated to better allow the part to be released from the mold?
  • (2) Does it require a paper-like surface finish or a diamond-like surface finish? Does it need to be shot peened?
  • (3) What requirements need to be met to prevent corrosion and wear?

All of these questions should be well answered before processing the mold.

Due to the development of new technologies and aluminum templates, especially for the design of injection molds, aluminum molds are becoming more and more commonly used in blow molds, R.I.M. molds, rubber molds, structural foam molds and R.T.M. molds. Although it may not be suitable for all application areas, in fact, its use is becoming more and more common.

Extended service life

Everyone hopes to extend the production life of the mold, such as using traditional tool steel to make the mold, using hard chromium or nickel metal plating on the surface, or using more specialized engineering coatings, which can prevent its surface from wearing or Corrosion promotes better demoulding. Later, in pursuit of the same goal, aluminum molds were used and a practical solution was found.

gloss level

In order to be able to produce decorative parts through injection molding, in addition to extending the service life of the mold, manufacturers also hope that the surface of the aluminum mold can maintain a certain degree of gloss. Therefore, it is recommended to use a non-electroplating nickel spraying process because This method helps extend the life of the mold surface finish, making it relatively easy to produce decorative parts.

Due to the soft texture of aluminum, if no surface coating is used, it will be easily worn by the plastic, accelerating its damage and thus changing the gloss of the injection molded parts. Electroless nickel coating adds 50RC to the mold surface, making it sufficient to protect and prolong the gloss and structure of the mold surface.

surface finish

Even more advantageously, an electroless nickel coating can achieve a better surface finish quality than the aluminum itself, but it must be noted that some surface preparation first needs to be done before the mold can be plated. For example, in order to enable it to achieve a lens-grade quality level, it is recommended to first machine the surface of the aluminum mold to a SPIA-3 grade finish level, and then apply a high-phosphorus electroless nickel coating of 0.0003~0.0005 before it is further polished. , bringing it to a diamond-quality finish level.

On the other hand, this process saves a lot of time and cost. Under normal circumstances, aluminum will also bring various defects, but they are often invisible to the naked eye. They can only be clearly seen on injection molded parts, which will inevitably lead to waste of material and returns. Time for the test bench to be re-tested to analyze and correct any problems that arise. Electroless nickel coating will help eliminate or minimize these defects before the mold is put into production.

Because the electroless nickel coating is deposited evenly on all surfaces of the mold, it will comprehensively cover the entire part, including all threaded holes, pin holes, etc., which actually improves the structural integrity of the aluminum mold. An additional advantage is that the application of the electroless nickel coating will not affect the properties of the aluminum as it is applied at a low temperature of 180°C.

On aluminum moulds, other coatings can work well, but this depends on the required production characteristics.

Anti-corrosion protection and water lines

If corrosion is a concern, nickel-PTFE coatings, boron nitride nickel coatings, and electroless nickel coatings will provide the best protection. After using any of the above types of engineering coatings, there is no need to spray other protective layers and anti-corrosion layers on the mold when the mold is not in use.

Waterlines can also benefit from electroless nickel coatings on aluminum molds. If used, there is no need to worry about waterline shrinkage or white, scaly coating, and it can reduce processing cycle time because the electroplated material can actually eliminate these problems. Therefore, as long as the plug is not pulled out from the mold before application, when the entire mold is sprayed, the waterline will also be covered by the spray coating.

At 50RC, the directly sprayed electroless nickel coating can provide general anti-wear protection, but the best protection can be obtained through PVC gas; at 50RC, the nickel-PTFE coating has good protection against wear. It has a medium protective effect, can improve lubricity, and has a good anti-corrosion effect; while the boron nitride nickel coating has excellent wear resistance and protection at 54RC, and also has good demoulding performance and anti-corrosion protection. .

It should also be noted that there are different grades of aluminum that require different treatments to ensure proper adhesion to any plated material. Therefore, it is always beneficial to understand your substrate or find a plating dealer who is equipped to provide you with analysis. This guarantees you the best adhesion on slides, mold closures, parting lines and other mold elements.

There is no doubt that the long-term trend of using aluminum molds for injection molding production will continue, and a series of more novel aluminum alloy materials will undoubtedly be developed to adapt and meet the production and application needs of different molds. No matter what situation arises when following this principle, there is always an engineering coating that can be used to improve the quality of the product and extend the life of the mold. It is a very simple thing, and dealers who provide electroplating services have a lot of experience. and resources are available to help people achieve this wish.

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