With companies watching their capital expenditures, mold plating and coating are in greater demand as a way to lengthen the life of a mold, increase cycle times, and reduce maintenance costs.
Plating and coating of molds is done for a variety of reasons, but the primary ones are longer tool life and improved lubricity for faster cycle times. This is even more important given the current economic climate, says Harry Raimondi, technical services manager for Bales Mold Service Inc. (Downers Grove, IL).
Bales develops mold plating materials and performs the plating service. One of its most in-demand products is Nicklon, an electroless nickel and Teflon plating that improves part release, enhances resin flow, and resists corrosion. Bales also offers Nihard (cobalt alloy coating and plating) and NiBore (electroless nickel boron nitride).
Bales Mold Service offers a variety of plating/coatings such as this small core and cavity coated wth the company's Nicklon.
Dura Slick from Progress for Indutsry can be applied just 0.0002-inch thick on mold components to improve the mold's lubricity.
“Molders need to keep running parts, so they’re looking for anything that can keep that mold in the press until regular preventive maintenance comes around,” says Raimondi. “We use our expertise to help them determine which plating or coating is optimum for the tool. Customers are not always sure what they need when they have choices of finish, so there’s a lot of communication between us and the mold shop. Most OEMs want low-cost ways to make the tools last and this is a good option.”
Gene Bianco, GM of Progress for Industry Inc. (PFI; Saegertown, PA), which specializes in mold plating for industries such as medical components, electrical connectors, automotive, consumer products, and closures, says the company offers a proprietary nickel-based product called Dura Slick. It’s a dry lubricant coating that offers a low coefficient of friction, and is the most requested coating of all the company’s products, primarily because it contains no mold release. “Dura Slick is ideal for slides and inserts and helps in the release of plastic parts,” explains Bianco. “Plus, it prolongs tooling life, prevents wear, and reduces cycle time in many cases.”
Dura Slick also works well on all types of tool steels, as well as Mold Max copper alloy, beryllium, and aluminum, and provides corrosion protection. To be effective, the layer of Dura Slick doesn’t have to be thick. “We start plating at 0.00005 inch or less, and can build up to 0.005, and we can control our plating to the nearest 0.0001 inch,” says Bianco. “Often the tooling we’re working with is so precise that we have to keep the plating to within tenths so the parts remain conforming.”
While many molders are used to getting flash coating with hard chrome throughout the entire core/cavity, Bianco says PFI can mask off the part and just plate the molding area. “That way the thicker plating deposit won’t affect the tolerances of the part, and it allows us to build up thicker deposits on areas that require it,” he adds.
Bianco notes that about half the company’s work involves mold salvage. “We can repair mismachined areas by filling in holes or other errors with a hard nickel plating, or if someone in the EDM process removes too much stock, we can build it up with our hard nickel and they can go back in with the EDM,” he says.
Additionally, Bianco says that the Dura Slick product can be built up if an engineering change is required because of a resin change and the shrink is different, or different release properties are needed.
“It’s imperative that we have plating procedures for every steel we plate,” explains Bianco. “We do pretreatment—we have a liquid hone facility and a glass bead facility. Sometimes that procedure is needed for older molds with corrosion.”
The molder’s edge
Weatherchem Corp. (Twinsburg, OH) uses Dura Slick on its molds for a proprietary line of consumer product PP dispensing closures. Vic Simich, senior tooling specialist, says the company uses Mold Max in these tools, and the PP emits a gas that erodes the copper. “Using Dura Slick protects it from that,” says Simich. “Other coatings will do that too, but this has both hardness and lubricity, plus it’s easier to clean and maintain, and we get more cycles between each cleaning.”
Weatherchem’s molding operation uses high-volume tools with high-production capacity, ranging from eight to 32 cavities. “If you use Dura Slick with grease, it enhances its properties,” says Simich. “However, we can’t use grease on caps used in food products, so this still allows us some dry lubrication to keep components from galling. It’s a win-win for us. We don’t have to grease it and yet it allows us to have the coating.”
Weatherchem typically coats between 0.0002- and 0.0003-inch thickness, and on the last tool the company had coated by PFI, it achieved almost a million cycles. “Some molds will last for 2 million cycles,” says Simich. “If there’s wear we can put a coating of Dura Slick on it and get more life out of the tool.”
The moldmaker’s role
When asked where along the supply chain the request for plating of tooling is generally made, platers say it’s from the molders. However, many mold manufacturers are proactive in plating their tooling, particularly when they see situations that could shorten tool life or add to maintenance costs.
Wally Schaub, co-owner of Pro Mold & Die (Roselle, IL), says that his company plates most of the molds it manufactures, and that “about 99% of the time it’s at our request.” Pro Mold plates to prevent galling and wear or if it involves a part with minimum draft where the molder might have trouble getting the part off the core. “In those cases we’ll tell the customer that it’s best to plate certain areas,” he explains.
Pro Mold typically nitrides the lifters and slides after they’re built to prevent galling and wear, and figures this into the cost of the mold. “It’s said that if there’s 10 points difference in Rockwell hardness between the slides and steel you won’t have to worry, but that’s not necessarily true, particularly on straight surfaces that are running against each other,” Schaub says. “We can achieve that hardness by nitriding these wear surfaces on the lifters and slides and create a surface as hard as a knockout pin.” —[email protected]