I think it is fair to say the 3D printing has revolutionised model making.
In the past developments in the world of modelling have had varying degrees of
impact: injection moulding, resin casting, laser cutting, air-brushing; but the
widespread availability of 3D printers, their cost effectiveness and the ease
with which they can be used is, to my mind, unprecedented.
Why and how? I will attempt to support this claim by sharing my own
experiences in designing, printing and constructing various models for my
garden railway.
The process of creating a 3D printed object can be summarised as:
- Buy a printer
- Set it up
- Download or draw a 3D image
-
Open the image in a slicer program (usually supplied with the printer)
-
Slice the image and save it as a GCode file (which contains the instructions
needed by the printer to make the object)
-
Load the GCode file into the printer (via memory card/stick, wifi or cable)
-
Prepare the printer (level the bed, load the filament, pre-heat the bed and
print-head)
- Print the object
- Remove the object from the print-bed
- Switch off the printer
These processes are fleshed-out in more detail below
Contents
What is 3D printing?
Put simply, a 3D printer is a device which creates a three dimensional object.
3D printers can be used to create a full sized house in concrete or a
precision mechanical part in metal but the printers we use for model making
generally use plastic or resin.
FDM printers
The most popular 3D printers for creating models for hobbyists are
Fused Deposition Modelling (FDM) printers. FDM printers force a thin
stream of melted plastic through a heated nozzle to fuse repeated layers of
plastic together. The nozzle and its associated heating element (ie the print
head) are moved left and right (X axis), forward and back (Y axis) and up and
down (Z axis) with electric stepper motors which are precisely controlled by a
microprocessor (ie a computer chip). In reality, the forward and back (Y axis)
movement is usually achieved by moving the print bed.
The plastic used for 3D printing is usually supplied on a drum as a filament -
ie a long thread (a).
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Source:
https://www.cleanpng.com/png-3d-printing-rapid-prototyping-ciljno-nalaganje-fus-1318947/download-png.html#Personal
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This is fed into the print head (b) at a steady speed so that it can be melted
and forced through the nozzle on to the print bed (e). The stream of melted
plastic is continuously moving and placed on to the print bed and/or the
plastic which has already been deposited there to slowly build-up the object
(c) in a series of layers.
Resin Printers
Resin printers work in a different way. I will cover that in another article
to avoid confusion here (See A Beginner's guide to Resin Printing)
Printer filaments
The plastic used in FDM printers is supplied in a variety of different forms.
The most popular are PLA (PolyLactic Acid) and ABS (Acrylonitrile Butadiene Styrene), though PETG (Polyethylene Terephthalate - Glycol modified) is beginning to gain
favour with some modellers.
All melting plastics emit fumes which you should avoid inhaling and so your 3D printer must be installed in a well ventilated room. The fumes from ABS are considerably stronger smelling and more harmful than either PLA or PETG and so it is advisable to install an air extractor or some sort near the printer if you are intending to use ABS.
PLA
PLA is by far the most popular. As it is a plant-based plastic it is almost odour-free when printing. It is easy to use, bonds readily with
superglue and doesn't require high temperatures during printing. It is
also biodegradable. Some garden railway modellers are concerned about how
long it will last in an outdoor environment and whether it will be
adversely affected by sunlight. Biodegradability is not really an issue as
PLA would take several decades to disintegrate in a landfill site and so
should last modeller's lifetime, particularly if it is painted. However,
PLA can be affected adversely by prolonged exposure to hot sunshine. It is
unlikely to cause problems in a temperate climate such as that found in the
UK, but garden railway modellers living in warmer climates might find ABS or
PETG to be a safer option.
ABS
ABS requires higher temperatures to print and is harder and more durable
than PLA. However, it is tricky to get good results with ABS. The printer
has to be set up very carefully and it's advisable to place the printer in a
draught-proof cabinet to help ensure the temperature doesn't fluctuate. In addition, the fumes which ABS emits when it is printing are very strong and considerably more toxic than those emitted by PLA or PETG and so should only be used in a well ventilated space and/or with some form of air extraction. ABS
can be readily bonded with acetone and is much more tolerant of hot sunshine
than PLA
PETG
PETG is a sort of half-way house between PLA and ABS. It requires a hotter
temperature to melt the filament which can be bonded with some of the
solvents used for styrene (eg Dichloromethane, methyl ethyl ketone (MEK), toluene, and cyclohexanone).
However, these solvents are highly volatile and listed as carcinogens and so
should be used with caution. PETG is, however, more durable than PLA and is
less susceptible to environmental factors.
Most of my models have been printed with PLA, though I have tried both ABS
and PETG. I found ABS to be extremely temperamental and experienced a series
of problems in trying to get successive layers to bond. It was a lot easier
to print parts with PETG but I was disappointed with the level of detailing
I could achieve with PETG as opposed to PLA.
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PLA v PETG
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The locomotive sandbox on the left was printed with PLA - the one on the
right was printed with PETG. Maybe, with perseverance, I could improve the
quality of PETG prints by adjusting the settings but the PLA print was
successful with the default settings.
NOTE: Both prints are as removed from the print bed, with their 'brims' still
attached. Brims help small parts such as these to adhere to the print bed
(see below) and are easily removed.
Buying a printer
"You get what you pay for" is generally just as true of 3D printers as
it is with most things in life. The more you spend, the better the quality.
But what does that mean in terms of 3D printers?
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Source: https://builder3dprinters.com/
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3D printing technology is developing continuously and new models of
printers generally build on the successes of what has gone before. Rather than
providing you with a list of manufacturers and models of printers which would
probably be obsolete the moment it is published, it is better for you to read a
few recent online reviews as to which makers and models are currently considered
to be the best value for money before parting with any cash. Simply search for
"
Best 3D printers 2021 (or whatever year you're searching
)".
What you might need to consider when buying your first 3D printer is:
- How much can I afford to spend?
- How often will I be likely to use it?
- Where will I put it?
How much can I afford to spend?
At the time of writing, FDM printers can vary in price from less than
£100GBP to over £50 000GBP. The more you spend, the better will be the
quality of the construction materials and components used and the higher will be the quality of what it prints. However, a lot
will depend on your maximum budget. My first 3D printer cost me just under £80 GBP,
when most hobbyist 3D printers at the time were well over £200GBP.
I wasn't sure about 3D printing and so wanted to try it out without forking
out too much cash. It's fair to say that, to achieve that price, the
manufacturers had cut a few corners, but I still have that printer and use
it regularly to print out parts which don't require a high level of finish.
Since I bought that printer, the average price of printers has fallen and
the quality of the sub-£100GBP computers has improved, so by shopping around
you could pick up a bargain.
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An example of a more recent sub £100GBP printer
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At the time of writing, Creality and Anet have gained a
reputation for good quality entry-level FDM printers and have sold millions,
so for a novice they are a good investment as there is plenty of advice and
good-value accessories available to help you through your early learning
experience.
How often will I be likely to use it?
That really depends on what you think you might be using it for? Before I
started creating my own 3D drawings, my use of my printer was limited to
items which others had created and could be downloaded (for free) from the
internet. So, my usage depended on what I could find which was suitable.
However, in addition to small items such as suitcases, crates, churns,
barrels and baskets, ......
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All these items on the luggage rack were 3D printed
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...... I downloaded the parts needed to build a small diesel locomotive and
a beam engine.
Sources for downloadable 3D images suitable for printing include:
These sources provided me with enough downloads to keep me busy for a few
months but, before long I couldn't find anything else I needed and so taught
myself how to create my own 3D drawings. After creating a few simple designs
such as window frames, seats, roof tiles and gutters, ......
..... I developed sufficient skills and knowledge to start creating
my own rolling stock.
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My own Southwold wagons drawn and 3D printed
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However, it took a while to learn the skills needed to draw objects in 3D (see below).
Where will I put it?
3D printers take up a fair amount of room. The space you have available on your
desk or workbench will largely dictate what size of printer you can buy.
Clearly, if you are intending to produce large scale models for your garden
railway then it is useful to have a printer with a fairly large print bed.
Most hobbyist 3D printers have a 200mm x 200mm or 220mm x 220mm print bed,
which is suitable for the majority of models. However, a 300mm x 300mm print
bed is very handy when producing rolling stock or buildings for use on a
railway built to 1:20.3 (15mm:1ft) or 1:19 (16mm:1ft) scales.
My first (cheap) printer has a print bed of 200mm x 200mm which was fine when
I was using it for printing small models, but once I started drawing and
printing parts for coaches and locomotives, I quickly found that the need for
a printer with a larger (300mm x 300mm) print bed.
Fortunately, I now have a dedicated workshop for my model making and so it was
simply a case of clearing some space on my workbench to accommodate my two
printers.
There are 3D printers with a fairly small footprint and so, if space is tight
and you anticipate only producing small scale accessories for your railway,
then something like this Labists Mini X1 printer with a print bed of
100mm x 100mm might be suitable
Alternatively, resin printers tend to have a much smaller footprint and
produce very high quality prints - see
A Beginners' Guide to Resin Printing
How to print a 3D model
There are slight variations in which FDM printers are loaded, adjusted and
set-up but the general principles are the same. This section will show you
what is involved in printing a model to give you an idea of what is involved.
Step 1 - Setting up your printer
All 3D printers need to be set up before they can be used. The three main
processes involved in setting-up are:
- Pre-heating
- Loading with filament
- Levelling the print bed
Pre-heating
Before the filament can be loaded, the print head needs to be heated. It's
also a good idea to heat up the print bed at the same time.
Most (if not all) printers have a small LED or LCD screen which is used for
setting-up and controlling the printer. Dependent on the type of filament
being used, the print head (or hot-end) must be pre-heated so the filament can
be fed through the nozzle.
Loading with filament
The filament is then threaded though the print head. The feed mechanism is
slackened-off to allow the filament to be pushed through manually until it
reaches the heated nozzle. It can then be fed through by hand until a stream
of molten filament appears out of the nozzle.
Most printers now have some form of automation built into the filament-loading
procedure with instructions as to what needs to be done next shown on the
screen.
Levelling the print-bed
To ensure that the base of the model being printed sticks firmly to the
print-bed, it must be perfectly level so the nozzle is exactly the same
distance from the print bed as it moves across it. This is usually achieved by
adjusting sprung-loaded screws at the four corners of the bed (though some
printers have only three adjusters).
Usually, a sheet of normal printer-paper is used as a sort of feeler-gauge to
determine the correct distance between the tip of the nozzle and the bed. The
print head is moved around the bed and adjustments made repeatedly until the
bed is levelled.
Auto-bed-levelling is available as an optional extra on most 3D printers. A
sensor is bolted to the print head and a series of readings automatically
taken at key points around the print-bed which are then stored by the
processor and used to make adjustments as the print is made. These sensors can
be quite tricky to set-up and, although auto bed-levelling sounds attractive,
it is by no means straightforward.
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Source:
https://www.creality.com/blog-detail/the-necessity-of-a-bl-touch-for-auto-bed-leveling
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Step 2 - Slicing the 3D drawing
3D drawings intended for 3D printing are usually saved as .STL or .OBJ files.
These need to be imported in a program which slices them into the series of
layers which the printer will lay down. 3D printers are supplied with a
dedicated slicer program, though any could be used as they all perform the
same job with varying levels of sophistication.
Once the drawing file has been imported, the slicing is done with the
click of a button and the "GCode" file which contains the instructions
to control the printer is either saved on an SD memory card, a USB stick or,
if the printer is hard-wired to the computer, sent directly to the printer.
As you can see above, this object will take 51 minutes to print and will use
6g or 2.00m of filament. The GCode file for this object can now be
saved to the memory card (or disk).
Slicing programs contain a wide array of settings which can be adjusted to
suit the properties of the filament being used or to change the way the object
is printed. Probably, the vast majority of modellers use the default settings
which are generally set-up for the specific model of printer with which it was
bundled. However, small objects or those with a narrow base will usually need
some additional support to help them adhere to the print-bed. This most often
comes in the form of a 'Brim' or a 'Raft'.
Brims
A brim comprises a series of concentric, overlapping strips of filament which
surround the base (or bases) of the object being printed.
The greater the number of strips, the more additional adhesion is provided.
The width of the brim can be adjusted in the slicer program. As it is only one
layer thick (usually 0.1 - 0.3mm), then is is easily removed once the object
has been taken off the print bed.
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| NOTE: This was printed on my £250GBP printer |
Rafts
A raft, as the name suggests, is a slab which is printed first and upon which
the object sits. The raft usually comprises a base layer, followed by a
criss-cross pattern of supports sandwiched between an upper layer on which the
object will sit.
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| NOTE: This was printed on my £80GBP printer |
Rafts are particularly useful when the an object's base is not particularly
flat or when ABS filament is being used as it can be quite difficult to get
the first layer of ABS to adhere to the print bed.
The raft is broken-off the object once printing stops and the object is
removed from the printer.
Skirts
Like a Brim, a Skirt is a series of concentric strips of filament surrounding
an object but, unlike a Brim, the Skirt is quite separate and does not touch
the object. It doesn't improve adhesion directly but can be used to ensure
there is a clean and steady flow of filament on to the print-bed before the
actual object is printed.
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Source:
https://www.trustfm.net/hardware/3DPrinter.php?page=FineCalibration
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Skirts are also used to provide some protection from draughts for small
delicate objects.
Once the GCode file has been transferred to the printer (via memory
card, stick, cable or wifi), printing can commence.
Step 3 - Printing the object
The actual printing of the object is probably the most straightforward part of
the whole process, providing all the preliminary steps have been gone through.
Preparing the print-bed.
A lot of printers are now supplied with rubberised surfaces or a removable mat
over the print-bed, to help with the adhesion of the first layer. Whilst it is
possible to print directly on to a smooth aluminium or glass print-bed, the
addition of some sort of medium over the surface is advisable. This can take
the form of:
- specialised sprays
-
hair lacquer spray
- a thin layer of Pritt stick adhesive
- a layer of decorator's masking tape
I've tried most of these and favour hair spray or sometimes Pritt.
The cheapest hair lacquer seems to be the most effective. A light coating is given to the print bed (carefully masking the print-head and surroundings with paper). Occasionally, the bed needs to be washed with diluted domestic ammonia to avoid a build-up, otherwise it's fairly foolproof and seems to result in very few failures.
On those odd occasions when hair lacquer doesn't seem to work, I use a very thin layer of Pritt, spread in one direction and then another at right angles. The Pritt needs to be reapplied to
the areas where printed objects have been removed and after a few prints I
generally scrape the Pritt off with a broad bladed chisel and vacuum
cleaner or it can be washed off with warm soapy water or domestic
ammonia.
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NOTE: It's easier to apply a thinner layer of Pritt when the print bed is hot
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Pritt can also be used with PETG and ABS. One application of
Pritt seems to last for dozens of prints with PETG but ABS requires a
good thick layer (and even then, in my experience, it doesn't always guarantee
success).
Pre-heating
Preheating the bed and hot-end isn't an essential prerequisite with PLA, but
is more necessary with ABS and PETG to help with adhesion.
Printing
Having made these preparations, it's then just a case of selecting the
GCode file from the memory card (or sending the file to the printer
from the computer) and waiting.
I usually monitor the application of the brim and sometimes the complete first
layer to check the filament is flowing smoothly and sticking to the print-bed
evenly. If the first layer looks uneven, I will tweak the bed levelling knobs
to raise or lower the bed while the brim is being deposited. Rubbing a finger
gently over the deposited rows of filament will soon reveal whether they are
or aren't sticking properly!
If tweaking the levelling knobs doesn't work, then the print is aborted and
the bed re-levelled from scratch.
With large prints, I check printing progress at least once
every hour, to ensure all is well. Sometimes the print head can snag on the
printed object and drag it off the bed - resulting in a mass of
filament-spaghetti. These things happen from time to time;
it's just a case of aborting the print and trying again. Alternatively, there
may be a problem with the shape of the object or the way it was sliced (eg
having insufficient support or a too narrow brim) and so it may result in a
return to the drawing software and/or the slicer.
All being well, a successful print should be sitting on the print bed at the
end of the printing process.
Drawing your own objects
Having tried to use several (free) 3D drawing programs and online tools, I
eventually discovered TinkerCAD and, so far, I have not created an
object with it which hasn't been accepted by my slicing software
(Cura).
Unlike most other 3D CAD programs, that start with a 2D drawing which is then
extruded into the third dimension, TinkerCAD tools are 3D objects,
which are placed on the 'Workplane', manipulated (ie resized or
reshaped) and then combined with other 3D objects.
To my mind, what is really clever about TinkerCAD is the way in which
any object can be turned into a 'Hole'. When a 'hole' is
combined (ie "grouped") with another object, the hole's shape is removed from it.
For example, to make a window frame, a box object is placed on to the
workplane:
It is then resized to match the dimensions of the window (by
dragging the white 'handles' on the corners of the shape).
Four boxed-shaped holes are then resized and positioned where the panes will
be, ......
..... and, when the holes are grouped with the frame, the panes are
created.
The window frame is then saved as a .STL drawing which can be opened up in the
slicer, turned into G Code and printed. It really is that simple.
If you think about it, most man-made objects are made up from a series of
simple shapes joined together. With a bit of effort, even the most complex
shapes can be drawn in TinkerCAD by joining simple shapes together.
A more comprehensive tutorial on creating railway related objects can be found
here -
How I drew an open wagon with TinkerCAD
Conclusion
There are some things which 3D printing do very well and things which it is
not so useful for - in terms of the technology as it presently exists. Who
knows where it will be in another three, five or ten year's time? In the
meantime, I have certainly found it to be an extremely useful adjunct to my
arsenal of modelling techniques.
Here are just a few of the things I have created for my railway with my 3D
printer - and this is just the tip of an, as yet undiscovered, iceberg!
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Southwold closed van, coaches and open wagon
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Ridge tiles
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Arched window frame and guttering
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Southwold six wheeled open wagon
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Station fencing
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Level crossing gates and station nameboards
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Kerr Stuart locomotive body
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Belt tensioner for my cheapo printer
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