Die Casting Success Story
Hard Surface, Die Casting Tool Coating Saves Die Pins from Soldering and Thermal Shock Failure
Each die designer's goal is to produce castings that come out of the die as finished parts, with no secondary operations required. However, as every tool designer learns, limitations in tooling and the physical characteristics of casting materials can lead to design compromises.
Everyone knows there are certain design guidelines and standard practices that must be followed. For example, one cannot cast non-tapered walls or cylindrical holes. Generally accepted design principles call for a 1 to 2 degree taper on core pins and other internal forms. Too little taper and there is risk of material build up, release problems, and broken tools.
A widely known die casting company has found that FortiPhySM coatings from Phygen have fantastic release characteristics, well beyond those assumed by the old design guidelines and standard practices. FortiPhy coatings resist wetting and soldering so well that, when necessary, it can specify nearly cylindrical core pins without hurting production rates.
The company produces a variety of thin- and thick-wall aluminum die castings. In one of its dies designed to cast high-quality electronic component housings, core pins are used to produce holes for self-tapping screws. Using traditional tapered core pins, the screw holes would have been loose at the top and tight at the bottom. In order to make a better casting, it designed core pins that approximated the drilled pilot hole specified for the screws.
The firm fabricated core pins with a draft of only 0.5 degrees per side. With such a shallow draft, pins would need to have exceptional release characteristics to survive the production line. In addition, these small (1/8-inch diameter) pins, located in a relatively massive area of the casting, experience high thermal cycling. This often causes tool steels to weaken and deteriorate rapidly, even with commercial coatings applied.
According to the company, it first had the core pins coated with a high-temperature CVD coating. During initial production runs, core pins were breaking frequently. Various other coatings were tried without success. The best were destroyed after an average of 1,700 shots.
The die casting company put in a call to Phygen after hearing about how FortiPhy corrosion resistant PVD coatings give better results in extreme conditions and radical tooling applications. Within a few days they had the pins back and ready for a production run. Running around the clock, the previous pin breakage problems halted production at least every other day for repair and setup. With the new FortiPhy metal surface coatings, core pins were still like new and going strong after more than 12,000 shots—well beyond the previous results.
This productivity improvement led the company to continue sending core pins to Phygen. “We just completed another run on a job that has 30 Phygen-coated core pins in the die. After more than 12,000 shots, we have had no broken core pins.” That kind of production adds to profits two ways, by increasing piece part numbers and by reducing downtime. ”Considering the die casting machine had to go down for three hours every time a core pin was replaced, savings from not having to shut down for broken pins is adding up very fast.”
The key to FortiPhy thin-film coatings exceptional toughness, low coefficient of friction, and corrosion resistance is its uniform, nanocrystalline structure. Phygen’s patented plasma acceleration process improves upon traditional PVD methods to produce the most uniform coating deposition layer possible, with exceptionally high adhesion.
Having solved the uniformity problems inherent in the PVD processes of the past, Phygen can apply thinner coatings that outperform thicker, less-uniform coatings. In addition, Phygen hard surface coatings are applied at much lower temperatures. Low-temperature processing and thinner coatings help to keep critical tool dimensions within tolerance, without the costly rework of other processes.
The company was an early adopter of FortiPhy high performance surface coatings. Its results and ongoing tests continue to support the move to FortiPhy coatings. “The firm has been pleased with the resultant productivity improvement, and will continue to use FortiPhy coatings for our toughest applications.”