By Dianna Brodine, managing editor
The American Mold Builder
Tooling life is at the top of the list of concerns for any molding project since downtime for repairs jeopardizes profit margins. Mold coatings and surface treatments have the ability to extend the life of injection molding tools, offering corrosion protection, increased performance and reduced wear.
Two AMBA-member companies provided additional insight into mold protection options.
Dynamic Surface Technologies is headquartered in Canton, Michigan. “There’s a distinction between what we do, which is surface treating, and coating processes,” said Loren Epler, president of Dynamic Surface Technologies. “Our DYNA-BLUE® and DYNA-BRITE™ surface treatment processes are intended to increase the life of tools for injection molding, diecasting, stamping and other types of tooling applications.”
Standex Engraving Mold-Tech, located in Carol Stream, Illinois, is the largest provider of surface finishes for molds, said Paul Williams, senior program manager for Standex Engraving Mold-Tech. “We design and apply textures to molds, including leather grains, stipples, geometrics and other decorative finishes,” he said. “We get involved in mold coatings because these finishes need to be preserved, and our Tribocoat process does that.”
Why apply mold coatings or other protection processes?
Coatings and surface treatments add a layer of protection to the mold steel, reducing wear that can occur as resins move though the tool. With today’s resin options containing a variety of additives and minerals meant to strengthen the molded plastic part, wear and tear on tooling can mean additional time in the repair shop. Corrosion also can be reduced through the application of a coating or surface treatment, protecting the steel.
“Every time you inject material across the surface of a mold, there’s a wear factor,” said Williams. “It could be caused by the materials, but sometimes the way a material is injected into a mold or certain gating processes may have conditions that contribute to wear in affected areas.”
A mold coating or protective surface treatment can make it easier for plastic resins to move through the mold, reducing cycle times and providing for a quick release of the molded part. All of these benefits reduce overall wear and tear on a mold.
“Treating the mold steel can double or triple the life of a mold’s surface at a cost that’s very modest when compared to the cost of the tool,” explained Epler. “With production levels at their peaks, downtime becomes a critical thing – it can cost the molder a lot of money. Coatings and treatments can make the tools last longer with less downtime and can improve the quality of the parts, too. In the long term, that can eliminate processes like flash trimming that may need to be performed when a tool starts to wear down.”
How are today’s resins impacting tooling life?
Plastics molders are finding that resin additives meant to improve end part quality are reducing tool life and production efficiency. “To strengthen plastics, resin manufacturers are adding glass-filled minerals,” said Epler. “The glass particles are hard, and that wears the mold out faster. That’s a big problem for molders.”
Although the addition of glass fillers can significantly improve the strength of plastic parts, glass fillers are highly abrasive. To counteract the effect the abrasiveness has on tooling, some molders recommend running equipment at slower speeds, which reduces parts per hour coming off the line. And, the wear still occurs.
In addition, flame retardant resins, frequently used in electronics, can be caustic to a steel mold surface. “When you start putting those in the equation, you really need to have a protective process that can prevent the attack,” Epler explained.
Williams added, “Any time the surface begins to show wear and tear – whether it’s due to corrosive materials like PVC or additives like glass – you’re changing the surface of the tool,” explained Williams. “And, of course, that changes the appearance of the surface. Prevention is paramount if it can replace maintenance. Mold coatings preserve the decorative finish appearances that designers have specified and approved for the production parts.”
How are mold coatings and surface treatments different?
“When talking about mold coatings, typically what comes to mind is a chrome plating or physical vapor deposition (PVD) coating, where the coating lays on the surface of the tool,” said Epler.
PVD coating is a vacuum deposition process, and chrome plating is an electroplating process. Both offer a decorative component, with metallic finishes that can be used to enhance the appearance of a tool, while still providing a barrier against damage and corrosion.
Standex Engraving Mold-Tech offers Tribocoat, a composite electroless nickel coating process. It can be welded and benched without any negative effect and it can be removed if surface damage occurs and needs to be repaired. “If the tool has a decorative surface, a coating that can be applied or removed typically is recommended to make it easier to re-etch the surface,” said Williams. “Etched textures can be more difficult to repair on tools that have been treated with an impregnation process.”
Dynamic Surface Technologies has a proprietary process wherein the “coating” is diffused into the steel, which means it can’t peel or flake off. In addition, said Epler, the surface treatment process is effective around curves or ribs. “Many coatings are ‘line of sight,’ so if the tool has deep ribs, some other processes can’t penetrate to the bottom of the ribs or through the water lines,” he explained.
Both processes provide protection against wear and corrosion, and tool builders should consult with experts regarding the best process for their particular application.
What is the takeaway?
With tight production deadlines, injection molders can’t afford tooling downtime. Mold builders can offer added value to their customers with education about the potential benefits of protective coatings or treatments.
“These days, everything is ‘just in time’,” said Epler. “With production levels so high, if a tool needs to be repaired, it can really affect profits.” Preventive measures in the form of added coatings or surface treatments may be the difference between a profitable job and one that veers into the red.