Application
(1) What level of final surface finish might the mold require for electroplating in order to better release the parts?
(2) Does it need to achieve a paper-like surface finish or a diamond-like surface finish? Does it require shot peening and polishing treatment?
(3) What requirements need to be met to prevent corrosion and wear?
All these questions should be well answered before processing the mold.
Due to new technologies and the development of aluminum templates, especially for the design of injection molds, aluminum molds are increasingly being used in areas such as blow molds, R.I.M. molds, rubber molds, structural foam molds, and R.T.M. molds. Although they may not be suitable for all application areas, in fact, their use has become increasingly common.
Extend Service Life
Everyone hopes to extend the service life of molds. When using traditional tool steel to make molds, their surfaces are plated with hard chrome or nickel, or coated with more specialized engineering coatings. This helps prevent surface wear or corrosion and facilitates better demolding. Later, in pursuit of the same goal, aluminum molds began to be used, and practical solutions were found.
Gloss Level
In order to be able to injection mold parts with good decorative qualities, manufacturers not only aim to extend the service life of molds but also hope that the surface of aluminum molds can maintain a certain level of gloss. Therefore, it is recommended to use a non-electrolytic nickel spraying process, as this method helps to prolong the surface finish life of the mold, making it relatively easier to produce decorative parts.
Since aluminum is relatively soft, without a surface coating, it is easily worn by plastic, accelerating its damage and thereby changing the gloss of injection-molded parts. A non-electrolytic nickel coating can increase the mold surface by 50RC, which is sufficient to protect and extend the gloss and texture of the mold surface.
Surface Finish
More advantageously, non-electroplated nickel coatings can achieve a better surface finish quality than the aluminum material itself. However, it must be noted that before the mold can be electroplated, some surface treatment is required first. For example, to reach lens-grade quality, it is recommended to first machine the surface of the aluminum mold to an SPIA-3 finish level, and then apply a 0.0003~0.0005 high-phosphorus non-electroplated nickel coating before further polishing to achieve diamond-grade surface quality.
On the other hand, this process saves a significant amount of time and cost. Under normal circumstances, aluminum can also have various defects, which are often invisible to the naked eye and can only be clearly seen on injection-molded parts. This will inevitably lead to material wastage and time spent returning to the trial bench for re-testing to analyze and correct the problems. Non-electroplated nickel coatings help eliminate these defects before mold production or minimize them.
Since the non-electroplated nickel coating is uniformly deposited on all surfaces of the mold, it covers the entire part, including all threaded holes and pin holes, effectively improving the structural integrity of the aluminum mold. Another advantage is that the application of the non-electroplated nickel coating does not affect the properties of the aluminum material, as it is applied under low-temperature conditions of 180°C.
Corrosion Protection and Water Lines
If corrosion is a concern, using nickel-PTFE coatings, boron nitride nickel coatings, and electroless nickel coatings will provide the best corrosion protection. After applying any of the above types of engineering coatings, there is no longer any need to spray additional protective or anti-corrosion layers on the mold during production downtimes.
Water lines can also benefit from the electroless nickel coating on aluminum molds. If used, there is no need to worry about water line shrinkage or the white, scale-like coating, and it can reduce processing cycles, because plating materials can effectively eliminate these issues. Therefore, as long as the plug is not removed from the mold before application, the water lines will also be covered by the coating once the entire mold is sprayed.
At 50 RC, directly sprayed electroless nickel coatings can provide general wear protection, though optimal protection can be achieved with PVC gas; nickel-PTFE coatings at 50 RC offer moderate wear protection, improve lubricity, and provide good corrosion protection; while boron nitride nickel coatings at 54 RC provide excellent wear resistance, as well as good release performance and corrosion protection.
