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Here's the place for discussions about those 3D creations for Tguage...and lets not forget the trials and tribulations of designing and printing.

The making of a viaduct..

Postby dkightley » Sat Jul 18, 2015 11:37 pm

With the now almost normal view of 3D printers being the salvation of all. Buy a printer, unpack it....and print whatever you want! Not quite!!

To give an idea of what's involved in the process, I thought I'd detail the design and printing of a medium sized model. The Forth bridge is a bit on the big side...and is taking a long time to do, so I need something smaller.

When barneyadi (aka Dave) announced that he was going to build a layout featuring the Ribblehead viaduct, i offered to help by designing and printing an accurate and detailed model of the viaduct..which he accepted. A perfect example to run through the processes involved....so here goes! :shock:

Firstly, for those who are not familiar with Ribblehead, hers' a photo I lifted from the web:
Ribblehead.jpg
Ribblehead.jpg (80.08 KiB) Viewed 2033 times

The viaduct is 400m long and 32m high at its highest, and consists of 24 almost identical arches each of length 14m. The arches are grouped into four sets of six arches, and the intersection between each set of six having a thicker column. Reasonably straight forward....but not quite. The viaduct is curved! So the first stage in the design was to consult Google Earth to find out the curvature....

Here's a satelite view:
Capture2.JPG
Capture2.JPG (150.98 KiB) Viewed 2033 times

Using this image, I decided to make an assumption....the viaduct is a constant radius, so I worked out the radius of the "curve" and it's angle. I've lost the actual figures...and can't remember the radius (it was huge!!), but the angle of the curve for the whole viaduct is 16 degrees.

From all of the above data, I made a very rough mock-up of the viaduct in my 3D package so I could get an idea if the figures I had were good......and to send an image to Dave so he could see what he'd let himself in for! Here's the mock-up:
Capture.JPG
Capture.JPG (24.61 KiB) Viewed 2033 times

As I was designing this remotely, and the fact I had some gash printing filament going spare, I printed off a low resolution ( print layer thickness of 0,25mm) copy of the viaduct and sent it to Dave so he could check it wasn't going to be the wrong size, etc for the layout he had in mind. I didn't take any photos so can't post one. :(
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Re: The making of a viaduct..

Postby dkightley » Sun Jul 19, 2015 12:07 am

Once Dave had given me the OK to proceed, I started work on the detail of the design.....

I decided to go for a road deck printed in four pieces that would form the curve. The four sections will fit securely together and have slots to hold twin track flexitrack. Each arch will be printed separately and will fit to the road deck and to the adjacent arch section. Several blobs of superglue should hold all the pieces together!! The arches are separate so that I can keep the amount of design work down. One standard arch; two lead-in sections, and a thin section to sit between two arches to make up the thicker columns!

I've designed it this way also because of the physical restraints in the manufacturing process. I intend to print the arches standing up so as to get the greatest surface detail on the sides...and so I can dial in support to ensure the arches print correctly. The road deck is in four sections due to the available build volume in my printer....but I'll be able to print the deck also the right way up....again with some support to ensure accurate printing

So, on with the CAD work. Here's a shot of the single arch with a single portion of the road deck:
Capture4.JPG
Capture4.JPG (87.01 KiB) Viewed 2031 times

The deck is keyed into the arch, the top of which is shallowed out so the edges meet flush. The slots for the flexitrack can be clearly seen...cribbed from the Forth bridge! I've not yet put any keying to locate the arch sections together, but have started the stonework detail.

Here's a progress shot of the stone detail:
Capture5.JPG
Capture5.JPG (84.06 KiB) Viewed 2031 times

This is one aspect where the design process has to take into account not only the size of the end product, but also the technology being used to produce it. Once my printer has had chance to approximate the surface, all of those triangular faces in the surface will be softened out and it'll look spot on! The only problem ....is the number of sticky out bits!! There's hundreds!! And each one is different to give a sense of randomness.

Just to give an idea of the proportion....each of the stone courses will be 1mm high! :shock:
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Re: The making of a viaduct..

Postby mattd10 » Sun Jul 19, 2015 10:26 am

Fantastic thread and great to see the processes behind creating something for home printing! Look forward to seeing more and photos of the viaduct!
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Re: The making of a viaduct..

Postby dkightley » Sun Jul 19, 2015 4:06 pm

Thanks for the comment, Matt.

I've reached a notable point....all the stonework texturing done on the arch section. And here's a shot of two sections of the viaduct placed next to each other to give an idea of how the final viaduct will look:
Capture6.JPG
Capture6.JPG (145.52 KiB) Viewed 2010 times

The next step is to add the keying that will align the columns at the bottom, and the skewing of the end faces by 0.33 degrees to form the curve....and then I'll be ready for a test print. That is once I get my printer back together....
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Re: The making of a viaduct..

Postby Nutter » Sun Jul 19, 2015 4:45 pm

How big is that going to be?
Mike based on the Southern side of London

Posting most of the time from a mobile phone please excuse typos. Happy to spot potential problems that other people may have overlooked.
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Re: The making of a viaduct..

Postby dkightley » Sun Jul 19, 2015 4:55 pm

Each arch section is 34mm long x 24mm wide x 70mm high...and the overall viaduct length is approx 850mm
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Re: The making of a viaduct..

Postby dkightley » Sat Aug 01, 2015 10:07 pm

I've not forgotten this project.

I now have my printer back in action......but I'm far too involved in the organising and running of a WW2 event at the Tramway Museum at the moment to be able to do very much towards it.

Once the event is over (after the 10th August) and I've had time to recover, I'll be able to get some printing done.....
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Re: The making of a viaduct..

Postby dkightley » Tue Aug 11, 2015 11:37 pm

Now I've got some of my energy back after a totally exhausting but amazing week of wartime event management, I'm back on the case.

I've done a test print of the road deck for one arch's worth. Here it is still on the printer plate with it's raft and support:
IMG_2149_red.JPG
IMG_2149_red.JPG (80.05 KiB) Viewed 1896 times

And here's it once removed and with the raft and support removed:
P1010450_red.JPG
P1010450_red.JPG (93.73 KiB) Viewed 1896 times

First impressions are that the stonework pattern on some of the coarses needs randomising a bit...which I've done.

To form the road deck for a quarter of the viaduct, I then angled off both of the ends so the formed a slightly wedged section...then mirrored the shape four times to get a deck section eight arches long:
Capture200.JPG
Capture200.JPG (68.46 KiB) Viewed 1896 times

The section at each end (with surfaces marked in red) will be shortened to form either the end of the viaduct, or the extra length at the joins.

I'm currently printing a test arch and will post a picture tomorrow...
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Re: The making of a viaduct..

Postby JBModels » Wed Aug 12, 2015 3:34 am

Looks lovely Doug..... with a bit of painting and weathering it's going to be a wonderful piece!
LOL! Some people need a to think logically, or rather just have common sense!
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Re: The making of a viaduct..

Postby dkightley » Thu Aug 13, 2015 11:37 pm

A day late :oops: (I don't like making a promise and not keeping it!) , but here's the first archway print:
IMG_2165_red.JPG
IMG_2165_red.JPG (124.38 KiB) Viewed 1857 times

I actually had issues with the stability of the support as it was printing...and I must have disturbed the print plate as I was trying to add bits of blue-tac to steady things. Notice the horizontal stripes on the back of the right-hand column..twas me moving the bed around whilst it was printing!! And I'd noticed an issue with the extrusion rate causing stringy bits on the surface. Both issues resolved as I've done a partial print since.

Also, since taking the photo I've actually broken the arch into two so I could place the two halves back to back to check the proportions of the column. I've also started making the wider section for the column for arch 6/7, 12/13 and 18/19, and for the lead-in and lead-out. No photo yet to make the explanation clearer...
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