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FABupdate
Solving Z-axis challenges during
stereolithography processes
12 | MARCH/APRIL 2010 | MICROmanufacturing
When producing 3-D parts via the SL process, it’s critical to compensate for overcure.
The increasing miniaturization of products
and devices requires designers to
iterate their designs at ever-smaller scales to
arrive at a final design. Unfortunately, they
often find themselves hamstrung by the lack
of prototyping tools that traditionally have
helped drive their iterations.
The latest 3-D printing technologies
were not designed
to operate at meso- to microscales,
and even the venerable
stereolithography (SL) technology
is stretched to its limits.
Those involved in SL—suppliers and users
alike—continually work to improve the process,
equipment and materials. At FineLine
Prototyping, we have addressed certain X-,
Y- and Z-axis limitations associated with the
process: X and Y in the imaging plane of the
equipment, and the Z-axis for building up
layers to form the parts.
This article addresses Z-axis challenges
and the means employed to overcome them
to ensure the production of accurate mesoand
micro-scale parts.
All images: FineLine Prototyping
Understanding Z-axis layers
FineLine’s high-resolution SL process features
0.002"-thick layers. A part is built from
the bottom up by stacking layers one on top
of the other to form a 3-D part to the specified
height. This might lead one to assume
that if a part has features at least one layer
Dead-flat leveling of the resin does not
occur. There are always areas that are
shallower and deeper.
thick, they should come out accurately in
the final part. Unfortunately, given how the
process and materials work, this usually is
not possible. The first layer of any feature,
whether it is on the bottom of the part or it
forms a “shelf” higher up somewhere, will
cure down into the liquid resin by several layers—sometimes
as much as 0.016".
Several combined factors contribute to this
“thick first layer” effect, commonly known as
overcure. In a nutshell, it is the result of the:
■ cure kinetics of the photopolymer