Top 4 Surface Treatments for Production Tooling
Hello, this is Gordon Styles and welcome to Serious Engineering. For those who are new here, I’m the CEO of Star Rapid and I have more than 35 years of experience in rapid manufacturing and new product development. I started this channel because I love to share what I’ve learned with other engineers and curious people just like you.
Now, on the very odd chance that you haven’t already seen it, may I suggest that you first check out our previous video where we learned about surface texturing for plastic injection mould tools.
Go on, I’ll wait. Ok, you ready now?
Today we’re on a slippery slope, as it were, sliding into the world of surface treatments for production tooling. It’s a subject that can be hard to grasp, so hang on tight.
First, a word about Tribology
Tribology is the study of friction and the interaction of surfaces in relative motion. It can at times be a triffle troubling but ’tis not as troublesome as tribbles.
But seriously folks, all manufacturing tools – cutters and endmills, moulds and dies – are subject to incredibly harsh working conditions and must withstand a lot of wear and tear. Tribology, therefore, comes in handy for discovering new and better ways for surfaces to interact without being destroyed in the process.
If you’re making a production mould tool, for example, you can easily see why this is important to you. Tools and dies represent a significant financial investment. If a mould wears out prematurely because of surface friction and must be repaired, that means lost production time and lost revenue.
So, investing in surface treatments that improve tool quality and longevity is one way to save money for long production runs.
Which Surface Treatment is Best for your mould tools?
As with so many things, it all depends on your particular application.
The amount of wear a mould experiences depends on many factors including the base metal, production volumes, heat transfer, resin type, design complexity, surface texture, gate and runner design and many more.
There is no one solution that’s right for everyone. That’s why there are different treatment solutions to help withstand heat, increase hardness, resist corrosion and lower friction for better part release. Here is a closer look at the top four general types for production tools. And note, these techniques can also be applied to other tools, like die casting moulds and CNC cutters as well.
One of the earliest forms of mould treatment is chrome plating. This increases tool hardness so it’s much more resistant to abrasion when using glass-filled resins. Chrome helps to prevent rust but it’s not resistant to chemical outgassing when using corrosive resins such as PVC.
Also, chrome plating requires the use of a separate anode. The anode adds expense to the build, and, because of the physical size and shape, it can’t reach deep cavities or thin features in a mold.
Electroless nickel plating doesn’t need an anode so it can be used to coat all features inside the mold uniformly. It helps the mould resist chemical attack but it’s not as good at handling abrasive fibers.
Nickel-Boron Nitride, another common plating, also improves abrasion and corrosion resistance without adversely affecting heat transfer properties. But it’s main advantage is that is greatly reduces friction so it’s used for moveable sliders, cores and other high-wear areas in the mold.
- Physical Vapor Deposition
In this process, the “source” is the object that will be vaporized. It’s usually a rod or ingot of ceramic or metal that’s struck with a high-energy ion beam that causes the material to “sputter” into a plasma. This plasma bonds to the tool wall in very thin layers with great adhesive strength.
How thin are these layers? Some are nanometers, or less than one micron, so not enough to affect the final part dimensions in most cases.
One of the most common applications on tools is Titanium Nitride (TiN). Not to be confused with TinTin.
It’s exceptionally durable and increases hardness greatly, while offering better corrosion resistance than chrome. It can withstand the chemical attack of PVC resins while enhancing lubricity. One potential drawback is that it’s applied at temperatures of 800C so this can affect the tool’s heat treatment. Another limitation is that this is a line-of-sight application, so it can’t be applied to hidden areas.
- Chemical Vapor Deposition
Unlike PVD, chemical vapor deposition uses a chemical reaction to produce a gaseous thin film. CVD coatings are thicker than PVD and applied at even higher temperatures. The advantage is that diamond coatings can be applied, offering the highest possible wear resistance and increased tool hardness for extremely long tool life. CVD coatings also don’t need to be applied in line-of-sight, so the whole tool can be treated.
One drawback to CVD is that, because of the high application temps., mould tools must be heat treated a second time after coating.
- Spray On Coatings
Another way to alter the surface tribology of a mould is with a spray-on mould release agent. These do not improve hardness or durability but are designed to increase lubricity (lower the coefficient of friction) so that parts can be removed more easily. Lower friction also aids in faster mould packing time.
The type of resin being molded will determine the best type of coating to use, although most are based on formulations of silicone, molybdenum, lithium or PTFE (i.e., Teflon).
Newer spray-on coatings use nanotechnology to create semi-permanent thin films that are more durable and greatly reduce friction. This helps to improve production efficiency by decreasing cycle times and prolonging tool life. Plus, it’s pretty cool saying “nano” about anything.
Speaking of time, that’s all we have right now. Don’t forget to ding the bell, like and subscribe. We’ll be back again soon with more Serious Engineering for Serious Engineers.
Warning: Side effects may include wearing slippers, slipping on banana peels, slipping into something more comfortable while singing “Slip Sliding Away”, skating on thin ice, singing “Skating Away” while mixing a scotch and soda, slipping out of gear, sliding into home plate, slipping up, and eating a batch of sliders while watching “Sliders” for a slice of Sci-fi.