Canadian Finishing & Coatings Manufacturing - Sept/Oct '23 - 24

PAINT AND COATINGS MANUFACTURING: ADDITIVE MANUFACTURING
temperature and then rapidly cooled, it has a different thermal
history than something that's forged or cast. So you begin with
a different microstructure because of the rapid cooling, and
you have to account for that in your heat treatment recipe. "
Ovens for this process are typically vacuum furnaces or a
controlled atmosphere furnace, according to Carl Hamann,
the Canadian technical sales business development manager
for Renishaw, which manufacturers metal AM technology.
" With a lot of materials you want an inert atmosphere.
Typically it's an argon atmosphere, but for some materials
you can use nitrogen, " he says.
" You can get away with not heat treating some materials.
But there are some that need heat treating, annealing and
stress relieving cycles to get the mechanical properties that
you intend to have with materials like Inconel or titanium.
If you're working with titanium, you're actually affecting the
grain structure and composition of it, and you heat treat it to
bring it back to the phase you want or get the ductility back, "
says Hamann.
Material World
If you ask if there's a difference between an AM and traditional
metal substrate, Simons says that it's less than you think and
that AM parts are being processed more similarly.
" This is another misconception - that the parts we produce
with this technology are somewhat porous or brittle, or the
structural integrity is not comparable to stock. That's simply
not true, " says Noack. " If you look at our process from a
technical point of view, it's a laser welding process and people
From an engineered performance
standpoint, AM allows manufacturers
to create more complex designs that
are more efficient or compact.
understand what's happening from a metallurgical aspect of
this. Our fusion process is much more likely to be adapted for
structurally critical parts than other technologies that might
use binder agents. "
Noack continues, " If you take a cross section, cut the part
in half, and polish the cut surface you will see the weld tracks
with the grains. You can post process these parts in any way
you would with conventional parts. The mechanical properties
of printed parts are very much comparable to stock materials.
And in some cases, they're even better if you compare it to
casting, with which you're usually dealing with impurities with
gas pockets. "
From an engineered performance standpoint, AM allows
manufacturers to create more complex designs that are more
efficient or compact. But one of the biggest challenges is in
changing people's mindset as they tend to want to stick to
traditional metals they know, rather than looking at alternative
materials that might have been too expensive to use in
conventional manufacturing processes but will improve the
performance of the part.
" With additive, you can drive that price down because we
have minimal waste and you don't need a solid block of that raw
material, " says Noack.
" Or maybe you're able to make a part with a material you
couldn't use before because you couldn't machine it very well, "
adds Hamann. " Materials like Inconel are hard to work with
and expensive to buy as a raw material. With AM I can get the
net shape printed and only have to machine a little bit to finish
up the surfaces I need to interface with. I can get 90 per cent of
the way to a finished part, it didn't cost me much, I got it faster,
and didn't have to machine it from a big piece of material. You
reduce the amount of post processing and bring your costs way
down. "
The Finishing Touch
The finish of printed parts is typically 10 microns in terms of
surface roughness, whereas a machined surface would be less
than one micron, according to Mark Kirby, industry training
manager at the University of Waterloo's Multi-Scale Additive
Manufacturing Lab. " The finishing steps are still a very critical
part of the supply chain. With complex parts, how do you get
them smooth without destroying the geometric accuracy of the
part? It's a chemistry problem, " he says.
But Hamann says that the surface finishes have come a long
way. There are a ton of post processes to get that surface finish
to where you need it.
" In the majority of cases you are machining it, tumbling it,
bead blasting or hand finishing and polishing, " he says. " Say you
have stainless steel 316L, there's going to be no difference from
a coating and finishing perspective because it's the same as the
raw material, it's just built differently. As long as the surface
finish is acceptable you should have no issues coating it. "
For the parts that BMA is manufacturing, Slade says that they
need anodisation, conversion coatings, paint and sometimes
grit blasting and tumbling. " But in general the finishing would
be the same as a traditional substrate. You debur, clean, maybe
acid wash and that would be sufficient preparation. "
" For anodisation, as with any manufacturing process, some
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Canadian Finishing & Coatings Manufacturing - Sept/Oct '23

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