Tech Briefs Magazine - July 2021 - 14

3D Printing Resolution
To test the Form 2's minimum feature size on the XY plane, a model (left) was designed with lines
ranging from 10 to 200 microns and printed in Clear Resin (right).
Practically, it means that you should
pick a 3D printer that performs well in
both categories (in all three dimensions).
SLA vs FDM 3D Printing
A lot has changed since the first desktop
3D printers became available to the
public. Now, SLA 3D printers are competing
for the same desktop spots as
FDM 3D printers. One of the main
advantages that resin-based SLA 3D
printers hold over their plastic-melting
cousins is print quality: SLA 3D printers
produce significantly smoother and
more detailed prints. While SLA printers
can usually also achieve significantly
smaller layer thicknesses, the reason for
the improved print quality lies in their
much higher XY resolution.
Unlike on FDM 3D printers, minimum
feature size in the XY plane on
SLA 3D printers is not limited by molten
plastic flow dynamics but rather optics
and radical polymerization kinetics.
210
190
170
150
130
110
90
While the math is complicated (and outside
the scope of this article), it shakes
out to this: features on SLA prints can be
approximately as small as the diameter
of their laser spots. And laser spots can
be very small, especially compared to the
nozzle size of FDM printers' extruders.
Laser SLA vs DLP 3D Printers
Resin 3D printers - like SLA, low-force
stereolithography (LFS), and DLP technologies
- offer the highest resolutions of
all 3D printing processes available on the
desktop. The basic units of these processes
are different shapes, making it difficult to
compare the different machines by
numerical specifications alone.
DLP 3D printers have a fixed matrix of
pixels relative to the build area, while laserbased
SLA and LFS 3D printers can focus
the laser beam on any XY coordinate. This
means that laser-based machines, given
high-quality optics, can more accurately
reproduce the surface of a part even if the
Intended Size vs. Measured Size
Measured
Ideal
laser spot size is larger than the DLP pixel
size. Whichever resin 3D printing process
you choose, however, professional resin
3D printers should be able to capture the
finest details of your creations.
In SLA and LFS 3D printing, layer
lines are close to invisible. As a result,
surface roughness is reduced, which ultimately
leads to smooth surfaces and
more translucent parts for clear materials.
DLP 3D printers render images
using rectangular voxels, which causes
an effect of vertical voxel lines.
Understanding XY Resolution
In the world of 3D printing, no factor
influences print quality more than XY
resolution. Often discussed but seldom
understood, the definition of XY resolution
(also called horizontal resolution)
varies by 3D printing technology:
* SLA and LFS 3D printers: a combination
of the laser's spot size and the
increments by which the laser beam
can be controlled
* DLP 3D printers: the pixel size, the
smallest feature the projector can
reproduce within a single layer
* FDM 3D printers: the smallest movement
the extruder can make within a
single layer
As a rule of thumb, the lower the number,
the better the details. Yet this number
is not always included in spec sheets
and when it is, the published value is not
always accurate. To truly know a printer's
XY resolution, it's important to understand
the science behind the number.
Practically, how does XY resolution
affect your 3D prints? To find out, we
decided to test the Form 2 SLA 3D printer.
The Form 2 has a laser spot size of
140 microns (FWHM), which should
allow it to print fine details on the XY
plane. We put it to the test to see if this
ideal resolution holds true.
First, we designed and printed a
model to test the minimum feature size
90 110 130 150
170 190 210
Intended Size (microns)
The results indicate that the Form 2 has the same ideal and actual XY resolution for features that
are 150 microns and larger.
14
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ToC
on the XY plane. The model is a rectangular
block with lines of varying widths
in horizontal, vertical, and diagonal
directions to avoid directional bias. The
line widths range from 10 to 200 mi -
crons in 10-micron steps and are 200
microns tall, which equates to two layers
when printed at 100-micron Z resolution.
The model was printed in Clear
Resin, washed twice in an IPA bath, and
post-cured for 30 minutes.
After post-curing, we put the model
under a microscope and took high-resoTech
Briefs, July 2021
Measured Size (microns)
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Tech Briefs Magazine - July 2021

Table of Contents for the Digital Edition of Tech Briefs Magazine - July 2021

Tech Briefs Magazine - July 2021 - Intro
Tech Briefs Magazine - July 2021 - Sponsor
Tech Briefs Magazine - July 2021 - Cov1
Tech Briefs Magazine - July 2021 - Cov2
Tech Briefs Magazine - July 2021 - 1
Tech Briefs Magazine - July 2021 - 2
Tech Briefs Magazine - July 2021 - 3
Tech Briefs Magazine - July 2021 - 4
Tech Briefs Magazine - July 2021 - 5
Tech Briefs Magazine - July 2021 - 6
Tech Briefs Magazine - July 2021 - 7
Tech Briefs Magazine - July 2021 - 8
Tech Briefs Magazine - July 2021 - 9
Tech Briefs Magazine - July 2021 - 10
Tech Briefs Magazine - July 2021 - 11
Tech Briefs Magazine - July 2021 - 12
Tech Briefs Magazine - July 2021 - 13
Tech Briefs Magazine - July 2021 - 14
Tech Briefs Magazine - July 2021 - 15
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Tech Briefs Magazine - July 2021 - 17
Tech Briefs Magazine - July 2021 - 18
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Tech Briefs Magazine - July 2021 - 20
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Tech Briefs Magazine - July 2021 - Cov3
Tech Briefs Magazine - July 2021 - Cov4
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