Tuesday, November 30, 2021

Introduction to the blog

Introduction


This blog describes ongoing progress in the development of a G gauge Garden Railway from its inception to the present day. 

NEW -

When I became interested in building my own garden railway I spent a considerable amount of time (and money) on books, videos, DVDs and scouring the internet for information, ideas and inspiration. When I eventually started construction I used some of the ideas I had discovered, but also experimented with my own approaches. This blog outlines how I have gone about constructing my own garden railway. My aim is to provide the sort of information I was looking for when I was getting started and also to share what I've learned (or 'borrowed' from others). I've tried to include a few 'How I ........' postings interspersed with occasional 'Progress Reports'. I do not profess to be any kind of expert - what I offer here is an opportunity for you to metaphorically look over my shoulder to see how I have gone (and am going) about this fascinating hobby.

As this is a blog, the various posts are presented in reverse chronological order (ie the most recent first). To see a categorised list of contents go to the Blog Contents Page.


If you are thinking about building your own garden railway then why not join the 16mm Association or the G Scale Society - you'll get plenty more advice and opportunities to visit other peoples' garden railways
. Alternatively, browse through the G Scale Central website - there's plenty more guidance here and an opportunity to sound out the views of others through the G Scale Central discussion forum.


The Blog


The advantages of blogging are that it is immediate and uncomplicated when creating and uploading information. The other, of course, is that with Blogger it is free. The major disadvantage is that I have minimal control over how the postings are presented. The blogging system adds the most recent information to the start of the blog, hence the postings appear in reverse chronological order (most recent first, oldest last). Whilst there is a list of postings on the right hand side, it's not particularly easy to see what is there. This introduction is an attempt to provide you with a contents list of the postings organised into categories so, hopefully, you see if what you are looking for is presented in this blog. To ensure that it always appears at the start of the blog, I update its content and set its presentation date into the future each time I add a new posting.

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Progress Report 93

 It doesn't feel as if three months have passed since my last progress report. There are quite a few developments which have kept me very busy and so writing the blog has taken a bit of a back seat for a while.

It's coming to that time of year when the railway goes into hibernation and so there's nothing to report about the railway's infrastructure. However, I have managed to get a couple of good running sessions in since my last progress report and hosted a visitor when live steam was the only motive power. I have constructed another locomotive and another two and a half Cleminson six wheeled open wagons - all of which were 3D printed. I have now acquired a resin 3D printer and have discovered the delights of printing small objects with fine detailing (including a figure). I have also shared my experiences with 3D printing and drawing via blog posts and had a short article about my Southwold rolling stock published in the Southwold Railway Trust.

On related issues, I have been fortunate enough to have a footplate ride on the Walsingham Light Railway in Norfolk and have made a start on an indoor project - an 0-16.5 representation of a small part of the Glyn Valley Tramway.


Rolling stock

Southwold Railway Cleminson open wagons

Having already constructed a Southwold Railway Cleminson six wheeled open wagon from my own 3D printed parts (see How I constructed a Southwold Railway Cleminson open wagon), I modified the drawings to produce two variants on the original design. 

One variant has additional metal straps across the planking on the side doors .......

...... and the other has the name of the local coal merchant, MOY, in large raised letters across the three side doors.

Although the first variant has been constructed, the second variant is awaiting the delivery of Bachmann metal wheels which have been on a back order from a supplier for two months. Apparently, there is a national shortage of these parts!


Metropolitan Water Board Kerr Stuart 0-4-2T

Having used a Bachmann Lyn motor block to construct a 3D printed model of a Schull & Skibbereen 0-4-2T loco, I was was generously given another Lyn motor block by a fellow modeller. This block was from a more recent version of the Lyn and was completely re-engineered from the original which I had found to be seriously under-powered. Then new design is a great improvement but my block had some significant faults - the flanges on two of the wheels were completely worn away on around a quarter of their circumference and the non replaceable brushes on the motor had disintegrated. Furthermore, the cylinders and associated coupling rods were also missing. 

Replacements were acquired from Bachmann Industries in the USA. The postage costs were almost as much as the cost of the spares but considering the motor block had been donated to me, I felt the costs were acceptable and much less than the cost of a secondhand Lyn.


After a quick internet search revealed, not only a suitable outside framed prototype, but some line drawings of the actual and the proposed locomotives. Using these, I produced 3D drawings for an amalgamation of the two designs - the proposed design better suited the dimensions of the motor block while the actual locos were more attractive in appearance (and provided several photographs for reference).

Once the parts had been printed out .......

..... it was remarkably easy to construct (or maybe I'm just getting the hang of designing, printing and constructing 3D printed locos).

However, I was unhappy with the way the body sat on the block - the larger diameter driving wheels made the body sit higher above the track than the original locos. So, back to the workshop and after a few cuts from the razor saw, I was much happier with how she looked.

The 3D drawings were modified to reflect these changes and have now been uploaded to Thingiverse.


3D printing

Having acquired a very cheap 3D printer just before Covid lockdowns started nearly two years ago, I have produced a wide range of items for the railway. A few people have asked me about the basics of 3D printing and so I put together a beginners' guide - see A beginners' guide to 3D printing

I have now also acquired an AnyCubic resin printer which produces highly detailed smaller items.

For example, here's a comparison between the builder's plate printed on my FDM printer and my SLA resin printer.



Operation

I managed to organise a couple of really good full operating sessions towards the end of August and early September.



In addition, I had another visit from Zach Bond and we had a good session running live steamers.


A new venture

With winter weather already making its presence felt, I was looking for something different to occupy my time before it's warm enough to return to working outside. 

I have always found the Glyn Valley Tramway interesting. Partly because of its location (less than an hour from here by car), partly because of its rolling stock and partly because of the type of goods it carried.

Source: NGRS WJK Davies Collection

Rather than attempting to squeeze a 16mm scale railway into the cramped space in my workshop, I thought I would experiment with 0-16.5. so far, I have drawn one of the Beyer Peacock tram locos for 3D printing and downloaded a wagon and a coach for 3D printing.


I am finding the challenge of working in a smaller scale to be interesting and already discovered I need to over engineer some of the parts to ensure they will print successfully. I am also beginning to realise that the resin printer will be more successful at producing the level of detail needed for the smaller scale models.


A grand day out

Towards the end of September, I was fortunate enough to be invited to take a footplate ride on the Wells  & Walsingham Light Railway in Norfolk.


The visit contributed to my retirement quest to visit all the narrow gauge and miniature railways in the UK and Ireland which I am logging on one of my other blogs - see ngruk.blogspot.co.uk


After taking some photos and video footage along the line I took my place in the confined space of the cab.

My driver (a certain Zach Bond), was an excellent and informative companion on the trip, explaining the complexities and intricacies of driving a loaded train up and down the undulating track which was laid lightly across the Norfolk countryside.

I can certainly appreciate the attraction and challenges of driving a real steam locomotive - even one which has been miniaturised. I am still not fully convinced that reducing the scale to 1:19 provides a comparable experience but, if I had the space and the capital, I would be sorely tempted to invest in a live steam ride-on loco.


<<<Previous Progress Report     -    Next Progress Report >>>>

Friday, November 12, 2021

A beginner's guide to resin 3D printing

This post supports and augments my previous post on 3D printing which focused primarily on FDM (Fused Deposition Modelling) printers - see A beginners' guide to 3D printing. In summary, FDM printers apply a series of layers of melted plastic to create an object in three dimensions. By contrast, resin, or SLA (Stereolithography), printers harden a series of layers of light sensitive resin to create a three dimensional object.

Image source:https://jiga.io/resource-center/3d-printing/best-affordable-resin-3d-printers-2021-buyers-guide/

The majority of domestic resin printers now use ultraviolet light projected through an LCD screen to harden small areas of resin at the base of a vat. The higher the resolution of the LCD screen, the more intricate and accurate the detail on the object can become.

The best way to explain how 3D resin printing works is to follow each stage of the process required to create a model.

 

Stage 1 - Creating a 3D image

3D images are created with a 3D Computer Aided Design (CAD) program. Once an images has been created, it is usually saved as a .STL or .OBJ file which can be understood by the slicing software for the 3D resin printer.

3D images can be downloaded from internet sites such as Thingiverse ......

.....or created yourself with 3D CAD software such as SketchUpFusion 360 or TinkerCAD.


For more information on downloading and creating 3D images see A beginners' guide to 3D Printing


Stage 2 - Slicing the image

As with FDM printers, SLA printers need to be given instructions to tell them what shape each layer of the 3D print should take. The .STL or .OBJ file of the object which has been exported from the 3D CAD program or downloaded from the internet ........

.... is opened in the slicing program which is usually supplied with the printer.

NOTE: For objects with overhangs, additional supports need to be created by the slicer or other programs

Slicing is achieved with the click of an on-screen button and the set of instructions required by the printer is saved on to a USB stick, SD card or sent to the printer via a cable or Wifi.

Stage 3 - Setting up the printer

Like a FDM printer, the print bed or building platform needs to be levelled in relation to the upper surface of the LCD screen. A sheet of standard A4 paper is positioned between the plate and the screen and screws adjusted and tightened.

The next job is to fill the vat with light sensitive resin. This is usually supplied in a 1kg bottle. 

Care must be taken in handling the resin as it is mildly toxic and so plastic gloves are recommended to avoid contact with the skin.

The vat is then positioned on the printer above the LCD screen and fixed into place. The base of the tank is transparent to allow light to pass through.


Stage 4 - Printing

Assuming object's slicer file has been loaded into the printer via the USB stick, SD card or via the cable or wifi, it can be selected from the printer's user LCD screen.

It is then just a question of waiting. The building platform (or print bed) is gently lowered by the printer into the vat and the first layer exposed through the LCD screen and the base of the vat.

The print bed is then raised a few millimetres before being lowered again, this time a fraction of a millimetre higher to allow the next layer of resin to be hardened. This process is repeated layer by layer until the object has been printed.

The print bed is then raised to its highest point to allow excess droplets of resin to fall back into the vat.


Stage 5 - Washing

The excess resin needs to be thoroughly removed from the outside of the printed object otherwise it will be hardened on to it by natural UV light. This can be done with Isopropyl Alcohol (IPA) either manually or more efficiently using a dedicated washing machine.

The object can be placed into the tank either still attached to the build plate or removed from it if it is large enough not to slip through the mesh of the wire basket holding it in place.

The alcohol is then agitated by the machine for five to ten minutes (time being dependent on the size or complexity of the object) before being removed and allowed to dry off for a few minutes.


Stage 6 - Curing

To ensure the resin is fully hardened it is then exposed to UV light. Again, this can be achieved simply by placing the object in sunlight or more reliably by placing it on a turntable while being exposed to UV LEDs. The process takes five to ten minutes with UV LEDs.

Stage 7 - Tidying-up

The object is now ready for painting or attaching to other parts to form a larger model.

The printer needs to be tidied away. If it is not going to be used for some while then the resin needs to be poured back into its light resistant container. If more parts are going to be printed then the resin can be left in the vat. Resin printers are usually supplied with plastic covers which resist UV radiation and some come with lids to cover the vat. I usually cover my vat with a layer of thick card as an additional protection and also place another large piece of card between the printer and the washer/curer to ensure there is no accidental UV light leakage.

It's very difficult to prevent drops of resin dropping from the build plate or unwashed object as they are being removed from the printer and so I find it useful to have a good supply of paper towels readily to hand.


Conclusion

An that's really all there is to it. The quality of printed object produced by SLA printing is superior to that produced by even the best FDM printers

Left = Resin printed - Right = FDM printed

They are probably similar in upkeep costs but resin printers can be a bit messy to operate and maintain. The build size is also smaller on resin printers, but as they are generally used for the production of small detailed parts that, to my mind, is quite acceptable.



Wednesday, November 03, 2021

A beginner's guide to 3D printing


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:

  1. Buy a printer
  2. Set it up
  3. Download or draw a 3D image
  4. Open the image in a slicer program (usually supplied with the printer)
  5. Slice the image and save it as a GCode file (which contains the instructions needed by the printer to make the object)
  6. Load the GCode file into the printer (via memory card/stick, wifi or cable)
  7. Prepare the printer (level the bed, load the filament, pre-heat the bed and print-head)
  8. Print the object
  9. Remove the object from the print-bed
  10. 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). 

Source: https://www.cleanpng.com/png-3d-printing-rapid-prototyping-ciljno-nalaganje-fus-1318947/download-png.html#Personal

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.

PLA v PETG

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?

Source: https://builder3dprinters.com/

 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 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.

An example of a more recent sub £100GBP printer

 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, ......

All these items on the luggage rack were 3D printed

...... 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.

My own Southwold wagons drawn and 3D printed

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.

Source: https://www.creality.com/blog-detail/the-necessity-of-a-bl-touch-for-auto-bed-leveling

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.


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. 

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.

Source: https://www.trustfm.net/hardware/3DPrinter.php?page=FineCalibration

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 (NB - only to be used when the bed is cold)
  • a thin layer of Pritt stick adhesive
  • a layer of decorator's masking tape

I've tried most of these but always return to Pritt. A very thin layer spread in one direction and then another at right angles seems to almost guarantee adhesion of the first layer. 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. 

NOTE: It's easier to apply a thinner layer of Pritt when the print bed is hot

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 will keep checking the printing process, 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 on the print bed. 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 board 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 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 combined (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. 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!

Southwold closed van, coaches and open wagon

Ridge tiles

Arched window frame and guttering

Southwold six wheeled open wagon

Station fencing

Level crossing gates and station nameboards

Kerr Stuart locomotive body
Belt tensioner for my cheapo printer