In this final part of the series on building battery locos, I have
decided to focus on 3D printing. If you have ploughed your way through any of
the previous four sections, you will have seen that 3D printing keeps cropping
up in each of them. It has now become an accepted part of railway modelling -
another skillset in our armoury.
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Part 1 - Kits
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Part 2 - Modifications and conversions
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Part 3 - Semi-scratchbuilds
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Part 4 - Scratchbuilds (pending)
In this section we will explore
- An overview of 3D printing and printers
- Downloading, printing and constructing other people's models
- Designing, printing and constructing your own models
An overview of 3D printing and printers
I'm not entirely sure why, but there are some modellers who regard 3D printers
with disdain, arguing that they are undermining more traditional modelling
skills. To my mind, 3D printers are just another tool in a modeller's armoury.
Over the years, various innovations have been embraced by railway modellers -
airbrushes, laser cutters, computer aided design software, the internet,
digital photography, colour printing, photo etching, resin casting, white
metal casting, transistorised controllers, digital command control, radio
control, butane burners, ...... do I need to continue? 3D printers are simply
another form of assistive technology. To get the best out of them requires
modellers to equip themselves with quite specific knowledge and a new
skillset. Whilst it is true to say this knowledge and the skills required are
quite different to more traditional construction techniques, they are no less
challenging.
For the hobbyist, there are two types of 3D printer - filament or FDM (Fused
Deposition Modelling) printers and resin or SLA (Stereolithography)
printers.
Filament printers
Filament printers carefully position a stream of melted plastic on to a build
plate. The heated print head can move in three directions in relation to the
print bed; left/right (x), forwards/backwards(y) and up/down(z).
The model is created by depositing a series of layers of plastic. Once the
first layer has been laid down on the print bed, the next layer is printed on
top of it, and so on until the model has reached its designated height.
Resin printers
The print bed on a resin printer just moves up and down. Below it is a vat of
photo sensitive resin with a clear plastic base. Below the base of a vat is a
digital screen which sits on top of an ultra-violet light source. The print
bed is lowered into the vat so it is a fraction of a millimetre above the
base. The shape of the first layer of the object to be printed is shown on the
digital screen allowing the UV light to shine through. This solidifies the
resin but only where the shape i bys shown. The print bed is raised by a fraction
of a millimetre and the next layer is projected on the screen and the resin
solidified. And so on.
Summary
As can be seen, both types of 3D printer create their objects as a series of
layers.
Resin printers have the advantage of precision (dependent on the resolution of
the digital screen) but have the disadvantage that they are more expensive and
the user has to deal with mildly toxic resins which need to be cleaned and
cured after printing.
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A resin printed 16mm scale figure
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Filament printers are generally cheaper and larger but the models they produce
tend to have more prominent layered striations. Filament printed objects
therefore need more smoothing and maybe some filling to improve their finish.
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A filament printed 16mm scale figure
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As can be seen, there isn't a dramatic difference when large parts are printed
(though the striations on the filament printed figure are more prominent).
However, with smaller detailed parts, the difference becomes a lot more
apparent, as in the maker's plate below.
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A maker's plate resin printed (left) and filament printed
(right)
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Making models using files downloaded from the internet
There is a growing wealth of files deposited on sites such as
Thingiverse which can be downloaded free of charge, imported into your printer's slicing
software (which creates code needed for the printer to create the layers) and
then printed out. The main advantage is that they are completely free
(provided you don't try selling them as your own creations). The disadvantages
are that you are limited to what is available which might not quite suit your
particular needs and you are dependent on the skills of the person who
uploaded the models - some models are better than others!
However, they are a great way of using your newly acquired printer and can
provide you with items at a fraction of the cost of buying them readymade.
For example, the first item I 3D printed for my railway was a pigeon basket -
something which was often seen on railway platforms in the inter-war years
but, to my knowledge, is not commercially available in 16mm or 15mm scale.
A couple of them. suitably painted, ended-up on the roof of my Clogher Valley
Railcar
In essence, the process for downloading and printing items from the internet
is:
- Locate the item(s) you need
- Download the files on to your computer
- Import the files into your printer's slicing software
- Upload the sliced files to your printer
- Make sure the printer is properly set-up for printing
- Print the object(s)
If you are resin printing there are another couple of steps in the process
- Wash the excess resin off your object with alcohol
- Cure the object by subjecting it to UV light
If the object is more complex than the pigeon basket, then you may have to download several parts and glue them together (I use thick Superglue from
Tool Station for both filament and resin printed parts), such as the parts needed to create this working beam engine.
To be honest, it is slightly more complex in that the slicing software needs to be tailored to your printer and the filament or resin you are using. You might need to rescale the parts if they are not quite to the right scale for your railway. Your printer needs to be carefully levelled and set-up, though this is becoming easier with each new generation of printers. Sometimes, things go wrong - the object doesn't adhere to the print bed properly, there are blobs or gaps in the object, the finish isn't as smooth as you have hoped, the print nozzle becomes blocked,, etc.. These setbacks can be frustrating but, with help from fellow 3D printers on forums they can usually be overcome and the with each problem your knowledge and ability to overcome obstacles improves.
Getting back to the subject of locomotives, there are a few 3D printable locos available for 16mm and 15mm scales on the internet and, hopefully, this number will increase over time.
For example, I have downloaded and constructed a small diesel loco which I found on Thingiverse.
For more information on this build, see How I 3D printed and constructed a pair of diesel locomotives
Designing, printing and constructing your own locos
I have created several files for my own 3D printed locos and made them available as downloads on
Thingiverse and the
Garden Rails forum. For example, see:
In summary my approach to designing, 3D printing and constructing a loco is:
1 - Identify a loco you want to build
When I first started constructiing my own 3D printed locos, I used commercial motor blocks as my starting point. The diameter of the motor block's wheels and the spacing of the wheelbase would largely dictate what sort of locos I could choose to construct.
However, now I have started making my own power units, the only limitation is tracking down suitable wheels. I could design and 3D print my own wheels; I know fellow modellers who do this very successfully; but I prefer my locos to have metal wheels and so this restricts the models I can construct.
2 - Find plans for the loco or find or take photos from which measurements can be made
If you can track down scale drawings of your intended loco, then this saves a lot of time and effort.
However, sometimes, it is either difficult or impossible to find any. In this case, you can work from photos. For example, when I constructed my three foot gauge de Winton vertical boilered loco, I visited the Welsh Highland Railway station at Caernarfon and looks a range of photos and kept measurements. Using these, I could extrapolate the dimensions of other components.
3 - Break down the loco into a series of parts
Whilst it is possible to 3D print whole loco bodies, I prefer to create a kit of parts for my locos. I usually start with the running plate. If I have a pre-existing motor block, I will have to work out how the body will sit upon it. This will inevitably mean a hole needs to be created in the running plate matched to the size and position of the block.
Although I try to carefully measure where the block will fit, it usually takes a couple of tries before I produce a running plate which fits perfectly. This is one of the great virtues of 3D printing and designing, it is easy to go back to the 3D drawing and make slight amendments.
I then usually tackle the cab, breaking it down into ends, sides and roof. Again, the beauty of 3D CAD is that the sides tend to be mirrors of each other and the ends are usually the same shape and size with slight variations on the position of the windows or spectacles.
In general, next comes the boiler or, in the case of a diesel loco, the bonnet. I usually make the firebox, boiler and smokebox as a single unit, unless the firebox is an awkward shape. The firebox tends to slot into a firebox shaped hole in the front of the cab. With Tinkercad, I generally turn a copy of the firebox into a 'hole' to cut a perfectly shaped and proportioned hole into the cab front.
I will usually cut some sort of cavity into the base of the boiler to allow access for the battery pack and electronics. Its shape and size is dependent on the position of the tanks for a tank loco.
Most of my locos are tank locos, and so the tanks come next. Side tanks are a lot easier to draw, tough some have rounded ends which can add an extra complication. As with the boiler, I will work out how I can gain access to them from beneath the loco.
I have been known to tweak the dimensions of tanks to ensure battery packs or individual cells can be fitted in. Saddle tanks are a bit of a pain. I would strongly urge you to make a loco without a saddle tank before tackling one.
Finally, I turn to the fiddly bits such as the chimney, dome, safety valves, backhead, etc, etc. Now I have created a few locos, I can often modify the parts I have drawn for other locos.
If I am using one of my own powered chassis, I generally create a 3D outline shape for it, so I can check it will fit OK.
Also, I tend to assemble some or all of the parts of the loco on screen before printing them, to check I haven't made any major mistakes.
Once this has been done, I print out all the parts and after doing a dry run, start gluing the parts together. Inevitably, some of the parts require a bit of tweaking to ensure what worked on screen actually works in practice. But, as mentioned above, this is a relatively easy process with 3D CAD.
Here's a selection of the locos I've designed, CADed, printed and constructed so far. I find the process equally as satisfying and as challenging as making a loco from scratch using plasticard, metal castings and brass strip.
They say that every journey starts with a first step. I can honestly say that, if you do decided to start designing, 3D printing and constructing your own locos, you won't regret it.
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