Plastics & Rubber World - May/June 2019 - 31

3d printing

orders. We recently sold our first machine
in India.
How is the overall market, is there a
lot of competition?
Yes, there is a lot of competition. They all
have good machines. But when it comes
down to it, every machine has its unique
selling point. You need to figure out with
the customer what they need. If someone
just wants a simple prototype, there are
probably better systems. But if you want
a functional prototype or a spare part, this
is the system for you.
So each machine manufacturer offers
something different in their specialist
field?
Yes, that's right. It's not that you have competition, in the basic sense.
So you create a niche and advance
your expertise within that area to
improve the process?
Exactly. Plus, the Freeformer is an open
system. The process parameters can be
changed in order to optimise the mechanical and geometric properties of the parts.
Can you go into more detail about
how the Freeformer 300-3X works?
We use the Arburg Plastic Freeforming
(APF) process. Like injection moulding, a
heated plasticising cylinder holds a melt of
standard plastic granulate. A rigid nozzle
then discharges tiny droplets in a high-frequency pulse. The part carrier moves in
three axes, placing each droplet in a calculated position. The droplets bond with
the surrounding material, layer by layer.
Are we talking about a stream size at
the micron level?
Yes, definitely at the micron level. When
we talk about layer thickness, the height
of the droplet stream is the layer thickness, we're looking between 100 and 200
microns (0.1mm - 0.2 mm).
Is that one of the reasons for the slow
speed of the print process, the small
amounts of material?
Well, 3D printing is a layer-based process.
If you just look at production time, yes,
then it's slow. But that's not the whole story, you have to look at the complete supply chain. Design through to delivery, it's
quite fast. If you send me a 3D file, I can
print that overnight.
If we were using an injection moulding
machine I'd need a mould, testing, a machine. That can take weeks. If you want to
have a really quick prototype, 3D printing
is way faster than other processes on the
market.
Is the material simply melted and then
shot into the deposition area?
Yes, the material is melted at about 210°C
when you're working with ABS. Polycarbonate is heated to 300°C. A tiny tip on
the nozzle creates the material droplets.

Does the system require a specific
type of polymer?
It's the same material used in injection
moulding, the same pellets. That is one
of the key advantages of the Freeformer,
standard material and standard material
price. It doesn't need a special filament or
power source.
Are the hard and soft materials applied
in separate application processes?
It depends on the geometry of the part,
what you want to achieve. We define that
in the software. Before you need to print
you have to slice the part. There, you define which elements have to be hard and
soft. Then we create a small overlap in
each layer and the material is added following the software.

Discharge units on the Freeformer
300-3X

Are there any limitations on the
additives which can be used?
What's important is the size of the additives. If they are too big, like glass reinforcement, they can jam the nozzle tip.
But we've used flame retardants for electronic applications. We've used a conductive material, a PC/ABS, which had carbon
nanotubes to make it conductive.
Can you run through the process,
from start through to delivering a
printed part?
First you need a CAD file. That's converted
to an STL [Standard Triangulation/Tesselation Language] file, the common file in
3D printing. Then the system slices the
STL file into layers and that info is sent to
the machine. The slicing is done automatically. The user defines other things, how
many parts, part orientation.

The Arburg Freeformer 300-3X is
delivered with necessary software

Does the CAD file require any special
software?
Yes, but it's delivered with the machine. All
you need to do after that is prepare the machine, heat the build chamber, for example.
How long does that take, to prep the
machine?
It doesn't take long. Slicing and preparing
the software takes a couple of minutes,
preparing the machine takes about 10 or
15 minutes. It also depends on what material you are working with, but it's in the
range of minutes, not hours.
Is there a maximum heat that the
finished part can withstand?
That's related to material property. ABS
cannot withstand such high temperatures
as polycarbonate, for example.
The layer joins are the weak point in
the printed structure?
Yes, that's right, but the droplets melt so
well together there is a good density to
the material. We've several parts which
demonstrate the high density and high
mechanical strength. But it is still a layer-based process and the joins are the
weak point, you need good adhesion.

›› Continued on page 32
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