I haven’t blogged about my 3D printing endeavours for a while, in fact the last time I wrote anything on this topic was back in March 2019!
At that point:
- I’d had my first three models 3D printed by Shapeways and while I’d been pleased with the results I’d had a few design problems and been a bit disappointed by some surface quality issues.
- I’d designed my first set of decals.
- I’d designed a sheet of etched parts for the three models that I’d had printed.
Since then I’ve been busily working on this project and now have some promising results to share.
Design Problems & Surface Quality Issues
While flat surfaces are fairly easy to smooth with tools and they can also be hidden under a piece of detailing etch, as would be the case with the man lids on top of the tanks shown above. Curved surfaces are a different proposition entirely and evenly smoothing a curved surface with ribs without destroying the fine rib detail in the process is almost impossible.
Even with the finest printing service offered by Shapeways, the surface is just too rough to not be distracting or hidden without obliterating the ribs of the tank. Even changing the orientation of the part while printing would make little difference and would massively inflate the printing cost as the tank would have to stand on end on the print bed.
So after a bit of thought I came to the conclusion I had two options. The first option was to re-design the models as kits and use an appropriately sized piece of tube as the tank. Details like manlids, walkways and outlets could still be 3D printed or etched and attached using superglue and 3D printed jigs or guides to help position them correctly.
The second option was to carry on using a 3D printed tank but cover it with an etched overlay. I could then 3D print the tank in a cheaper lower quality material without sacrificing the quality of the end result. Photo-etched overlays also make it much easier to produce very fine rib detail accurately and reliably at the cost of well, an increase in the cost of the final model 🙂
In cases where the tank is an odd shape (think about the round tanks with flat sides on modern bulktainers) or there is no appropriately sized tube I could use both techniques and 3D print a tank slightly under size via a cheaper, lower-resolution printing service and use a photo-etched overlay to lay on the final surface detail.
Too Many Models…
Now I had to focus, as I was planning to re-design everything it was obvious I was dividing my attention between too many models so I chose to work just on the ISO bromine tank model. Here is the ISO bromine tank in it’s original form with a 3D printed tank:
Here it is in new tube kit form:
While it’s not immediately evident in this photo, I also used the redesign as an opportunity to change the way the etched deck would mount to the frame, shrink the diameter of the tank and increase the size of the discharge valve on top of the tank as the original model didn’t look or measure up correctly compared to new reference photos I’d found.
Shapeways Fine Detail Plastic 3D printing offers incredible resolution so I decided to have a go at tabs and slots for connecting the frame (grey) to the base (blue).
The strange grey tuning fork-like object is a guide to help align the discharge valve to the top of the tank when you put the model together.
I was struggled to find anyone in the UK to print my decals so I decided to cast my net a little wider and try a couple of services in the US and Canada.
I ended up going with a company called Precision Design Co (PDC) run by Bill Brillinger. As this was my first decal project there were quite a few problems with my initial submission but Bill patiently helped me work through the errors and problems in my file and the technical issues caused by Inkscape/Linux and Corel compatibility.
The final results are excellent:
As you can see Bill can even print white which is very convenient when printing tiny ADR placards. These decals are easily equal to the pad-printed details on most N scale RTR models, in fact, the decals are better in some cases and all but the tiniest text is legible under magnification! The decals respond well to MicroSet and MicroSol and even without a top coat the carrier is very thin and unobtrusive.
If you need N scale decals I’d recommend giving PDC a chance to quote.
I’d originally designed an etch that featured details for all three of the 3D printed models I was working on:
I did this to minimise the cost per model but after much deliberation I decided this probably wasn’t the best way to go about things. Time for another redesign; with the new sheet I only included parts for the ISO bromine tank container.
I commissioned PPD Ltd to produce the etch. If you’re producing your first etch their website contains lots of useful information and advice on selecting metals, sheet thicknesses and file preparation.
Here’s the result: a sheet of super-fine nickel-silver parts.
Putting It All Together
So here’s the new 3D printed kit version of the ISO bromine tank with etched parts:
Unfortunately between the test fitting stage and the final photos below I ran into some problems with the tab and slot construction method. I’m currently restricted to brush painting and despite repeated attempts at cleaning the tabs and slots they just didn’t want to go together upon final assembly. Seems obvious in hind sight but this is probably due to a combination of the tolerances involved (0.05mm) and the relatively thick layers of paint that brush painting lays down.
So please forgive the wonky/broken frame in the photos below:
Here’s my modle alongside a Fleischmann tanktainer (the height difference is prototypical as the Fleischmann model represents a taller tanktainer although it’s actually quite inaccurate in other respects):
Despite the problems with the tab and slot construction I’m very happy with the final result and once I’ve corrected the construction issue I’m confident I’m going to be able to produce a model at or above the quality of a RTR to model.
I’ve already created another version of the CAD model with a different and simplified construction method. The simplified construction method also means that the model is a suitable candidate for printing via i materialise’s high-detail resin service.
Resin printing is not only cheaper but it might actually result in better surface quality too so fingers crossed in that respect.
I’m currently waiting for prints of the re-designed model to come back from i materialise and I’ll post some updates when I get them.
The results of this experiment have also given me new motivation to re-design the other two models and work on some new projects too. Watch this space…