If you are printing at home, you have no startup fee and your material cost will be much less. A single spool
of PLA filament, 1kg (2.2lb), will represent about 800 cubic centimeters of printable material and costs
around $21 to $35. More exotic filaments like PET or flexible filament are roughly double the price of PLA
filament, thus in the $70 range.
Resin printing has a similar price per cubic centimeter compared to FDM printing when printing with the
lower cost resins. One liter of resin contains about 900 cubic centimeters of printable material. 1Kg of fil-
ament is about 800 cubic centimeters. Assuming a parity between 1L of resin and one spool of PETG, the
prices are comparable. Resin prints tend to have thicker walls than FDM as there is no time penalty for
printing a thicker wall on mSLA printers. In the FDM world, those thicker walls would take quite a bit more
time to print. The thicker walls on resin prints serve to make the objects more structurally sound, but at a
higher material cost.
TIME NEEDED FOR SETUP/CLEANUP
This is the other critical factor that sways people in one direction or the other. With the online print services, the
base startup fee for an FDM print can be around $5. For resin prints, startup fees can be around $20. Why the
difference? Resin is much harder to work with than FDM. When you run a resin printer, you have to use gloves
to prevent the resin from getting on your hands, as well as pour the unused resin back into containers for long-
term storage. A resin print also needs to be washed off with isopropyl alcohol to remove the uncured resin, and it
needs some time in an ultraviolet curing box (or to be placed in direct sunshine) to finish curing.
For an FDM print, you just pop the print off of the build plate and everything is pretty much done. Of course, if your
workflow requires extreme detail, or you do not mind working with resin, you will enjoy the prints that resin print-
ers create.
PRODUCTION QUANTITY: LOW-VOLUME MANUFACTURING
If you are looking to create many units of a design, you have three options: 3D print them at home, go through a
service bureau, or use traditional manufacturing. Typically, creating a mold for injection molding (traditional man-
ufacturing) costs anywhere from $2,000 to $10,000 for a simple mold, and then the prices increase for molds that
are more complex or that are made for producing many thousands of items. Before 3D printing there was a gap
in the market where inventors and product designers had very few inexpensive options if they wanted to produce
a thousand or less copies of an item. The economics for traditional manufacturing (with molds) only made finan-
cial sense when production neared the “several thousands” unit range.
Additive manufacturing has changed all of that. Prototypers can move to smaller production runs at signif-
icant fractions of the cost that previously were commanded by manufacturers. The economics of making
many thousands of items still favor traditional manufacturing, but a new class of “boutique” manufactures
is being created by 3D printing.
CHOOSING THE RIGHT QUALITY FINISH FOR PRINTS
If you want to sell products to consumers and the quality of surface finish is important, you can outsource
your printing to a 3D printing service bureau to get excellent quality at a higher cost per unit. Or, you can
print the objects yourself.
If you decide to print the objects yourself, you have several options for surface finishes. If you are trying to
compete with traditional parts (that have smooth surface finish), then any FDM print will not be the right
choice without what is called “post processing.”
This is a generalized list that applies to both FDM as well as to resin prints. Post processing steps can also
apply to prints made at service bureaus, even from their very expensive 3D printed titanium parts!
SOME POST PROCESSING OPTIONS MIGHT
INCLUDE:
• Surface sanding (either manually, or mechan-
ically) using smoothing machines and sanding
medium like glass beads or plastic pellets
• Milling operations to create perfectly dimen-
sioned holes for screws
• Tapping (the act of cutting threads into an object
rather than 3D printing the threads)
• Heat set inserts as shown in Figure 7-9. If you
want excellent threads to accept screws, you
can heath these up with a torch and press these
into the 3D printed plastics to lock them in and
provide great threads
FIGURE 79: : A heat set insert which would get pressed into a 3D
print the enable reusable threads (Image credit: Joshua Vasquez,
via Hackday article https://hackaday.com/2019/02/28/threading-
3d-printed-parts-how-to-use-heat-set-inserts/ )
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If you decide to use FDM printing for creating end-use
parts you can use a material called ABS (acrylonitrile
butadiene styrene). As previously discussed, ABS
is a durable material but can be a bit smelly to print
with; it also requires a heated print bed. ABS has one
unique capability, however. The chemical acetone
“liquifies” ABS. You can use acetone vapors to “melt”
the outside layers of your print, as shown in Figure
7-10, to create a smooth finish.
FIGURE 710: Before and after results of treating the outside of an ABS print with a few seconds of acetone vapor
Acetone: Proceed with
Caution
Acetone is an aggressive chemical that is not rec-
ommended for inhaling or direct skin contact. The
acetone vapor you will be producing by heating
the acetone is extremely flammable. Exercise
caution, otherwise explosions or fires may occur.
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The other method for making production parts out of FDM prints is to post-print hand-process them. This
could include sanding the prints to remove the obvious layers created by the printing process, as well as
painting the model to cover up the remaining layers. It is a laborious process, but one that can yield nice
parts, at the expense of your time.
EVALUATING FOR SPECIAL MECHANICAL CONSIDERATIONS
Even if your product does not need to undergo extremes in terms of durability or performance under
stress, something as small as a pair of earrings still undergo the forces that are common in life. Objects get
dropped, or brush up against a wall, or get tossed in buckets with other items. You need to make sure that
your print can withstand the environment in which it will be placed. On average, it’s best to start with FDM
prints, even if those prints might not have the best surface quality as compared to resin prints.
Another main reason to prefer FDM over resin is the wide variety of FDM materials available to the con-
sumer, which gives you more choice in suiting the print to its end goal.
As an example of the breadth of filament available, Figure 7-11 shows a spool of impact modified PLA (poly-
lactic acid). It looks like normal filament, but looks can be deceiving!
FIGURE 711: A spool of impact modified PLA
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The impact modified filament in Figure 7-12 is an example of a “blended PLA” that was designed to improve
on PLA’s characteristic to be rigid, but brittle when exposed to stresses. There is a growing field of “func-
tional filaments” created by a number of reputable companies. They can create not only decorative items,
but items that are designed to take advantage of specific material properties.
SOME NOTEWORTHY BRANDS OF “SPECIALIST” FILAMENT MANUFACTURERS ARE:
• NinjaFlex provides flexible filaments, more generically called “TPU” (thermoplastic urethane)
filaments
• PETG is similar to what water bottles are made out of and is one of the most popular materials for
FDM printing
• Many types of “enhanced” or “impact modified” PLA
• Nylon is very strong but slightly more difficult to print with due to its tendency to absorb water
quickly from the air thus necessitating keeping the filament dry between print runs
As an example of what a functional filament is designed to do let’s take impact modified PLA. PLA is a great
material to make strong, rigid objects. But, once your object gets stressed to a failure point, normal PLA
will snap or shatter. Look at the following example prints to see how a normal PLA part (left, in black) fails
FIGURE 712: : After three back-and-forth bends, normal PLA (left) snaps, while the enhanced PLA (right) remains structurally sound
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while the “enhanced” PLA (right, in blue) survives. Each sample was bent back-
ward and forward three times, as shown in Figure 7-12.
The rise of enhanced/functional materials that overcome the limitations found
in current filaments will increase. We will continue to see advancements in
both FDM and SLA materials, making them more adaptable and useful in more
applications.
CONCLUSION
You are now more familiar with the options you have when 3D printing your
models. You will need to consider your resources in terms of money, time, and
willingness to work with technology that sometimes fails when making the deci-
sion to print at home or outsource the job to a third party.
It’s great fun to watch the printers operate, with their buzzing and whirring, and
then seeing the results of your work turn into a physical product. Additionally,
for many people, the enjoyment of producing 3D CAD models themselves will be
more popular than the actual physical printing process. You won’t want to miss
the next chapter, which walks you through the whole 3D printing workflow from
idea, to CAD model, to print!
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