Coating mould components (like ejector guide elements, cores, lifts and cavities) increases the lifespan of moulds while reducing maintenance and running costs.
The moulds used to create plastic parts ranging from water bottles to automobile bumpers are the most critical – and expensive – part of the injection moulding process.
In some cases, a single mould can cost hundreds of thousands of dollars, not including the ongoing maintenance and running costs.
Injection moulders are turning to a variety of coatings to protect their investment and reduce maintenance and running costs. These coatings, applied to mould cavities as well as moving, sliding components within the mould, come in a variety of styles from carbon-based coatings, PVD & PACVD deposition to nitriding techniques that share one overriding goal: to harden the surface of the steel to protect it against all manner of abuse.
Oerlikon Balzers’ prodyct range includes carbon-based coatings such as Balinit C, Balinit Triton or Balinit Dylyn, which are thin (approximately 2-3 microns) and provide extremely hard layers to the surface of components and cavities.
“These coatings are applied for the simple fact that steel alone is not hard enough to protect these expensive moulds and ensure optimal uptime and productivity,” explained Thomas Vermland, Global Application Manager for Oerlikon Balzers, a company that has been producing specialised PVD coatings for components and tools for more than 30 years.
In the automotive industry, manufacturers are placing greater emphasis on design and weight reduction. Subsequently, automotive designers are increasingly using glass fibers as reinforcements in many parts, including automobile bumpers. As a result, automobile bumpers are constructed using less material than before.
“Inside the mould there is more pressure and higher temperatures being used to inject the plastic by a factor 2-4 times higher than in the past,” explained Vermland.
Vermland said Oerlikon Balzers’ Balinit Primeform diffusion treatment increases injection mould surface hardness up to 1400 HV.
This makes the moulds significantly more robust (including versus long glass fibers) and reduces residue build-up, spalling and edge embrittlement.
“We can take the entire bumper mould and place it in the machine and treat it in one operation,” said Vermland.
“With the diffusion treatment process we can take a base steel and harden the first hundred microns of the surface to Rockwell hardness well above 65.
“The rest of the steel remains unaffected.”
With the surface now harder than that of the glass fibers and any additives, repairs and re-polishing are reduced as much as 80%, according to some customer experiences.