A project that I take up from time to time: The Austro-Hungarian 420 mm howitzer called «Küstenhaubitze M.14». And I will present it here, as in this way I have no choice but to carry on regardless my current mood ;D
420 Rovereto 6.jpg
The sheer unlimited number of nuts and bolts and their different layout in all the photos can drive you crazy. That's why I have to put away this project in regular intervals...
(Bernhard, doesen't this sounds familiar?)
L6-5.jpg 7-8-7.jpg
That reminds me of a wooden ship model I put away at the age of 16 and never returned to. -- Russ
Quote from: Peter_T1958 on November 29, 2024, 01:07:36 AM(Bernhard, doesen't this sounds familiar?)
Yes indeed, Peter. After decorating almost 20 m of angle profiles with embossed rivets recently, I've had enough of this "meditative activity". But there's only one thing to do: keep at it!
Bernhard
Cool! A very interesting project!
Hi gents
As I wrote in my other tread (https://www.finescalerr.com/smf/index.php?topic=3392.15 (https://www.finescalerr.com/smf/index.php?topic=3392.15)) on my working desk there is always only on a single project. Though on my computer there are mulitple projects under development. Due to the hot wather in Europe I wasn't in the mood to work on my Centurion.
I therefore took up my work on the Austro-Hungarian 420 mm howitzer called «Küstenhaubitze M.14» where I am able to spend some night time (when it's colder) on my computer.
And I made some progress – or rather a re-start! :o Instead of working on each segment (there are sixteen segments of the same basic layout but with different configurations) I created a new «mother» segment with all possible nuts, bolts and holes included.
(https://images20.fotki.com/v1691/photos/4/3824994/14463210/Mother-vi.jpg)
Taking this as the starting point, I am able to add/subtract the details as desired. In last few days my progress was about the same as in the past half year. As they say: Work smarter not harder ;)
(https://images15.fotki.com/v1635/photos/4/3824994/14463210/Zusammenstellung_klein-vi.jpg)
And that is the awesome beauty of CAD. -- Russ
Just trying the posting of another update!
And it is astonishing to see what progress is possible with this new approach... Nevertheless I must confess, all those small differences in the arrangement of bolts, nuts and holes is still a boring task. Each of them has to be placed according to photos of the real thing.
BTW. Currently, this looks still more like an old spin drier than the biggest gun of the Austro-Hungarian army ::)
(https://images49.fotki.com/v1692/photos/4/3824994/14463210/Zusammenstellung_2_klein-vi.jpg)
(https://images12.fotki.com/v1690/photos/4/3824994/14463210/Zusammenstellung_4_klein1-vi.jpg)
Peter, Your "mother" segment is an excellent idea and sounds like it is working well.
Stay cool. It is hot here, but nothing like what you have been enduring.
Yes, the mother segment is a really good idea. Are you just modeling the 3D model, or will you make a physical model out of it later?
Bernhard
Thanks, gents!
@ Bernhard
As all of my WWI designs, also this one is planned to become a 3d kit in the distant future. There are some producers around that are seriously interested in this subject, although the number of potential customers would be very small.
But if all that were not enough, there will be also a related crane to be done...
(https://images15.fotki.com/v1675/photos/4/3824994/14463210/Kran-vi.jpg)
Fortunately I found a large photo collection at the «Österreichisches Nationalarchiv». These pictures help a lot in understanding the whole buld up process. Astonishingly enough, this gun was described as «mobiler» Mörser M.14... :D
(https://images49.fotki.com/v1692/photos/4/3824994/14463210/Zusammenbau-vi.jpg)
If you build it they will come. -- Russ
I'm really looking forward to the model of this crane. Together with the Mörser, one can certainly create an interesting diorama.
Bernhard
As I wrote before, all those small differences in the arrangement of bolts, nuts and holes are a boring task. At the moment I have even the feeling of developing a ,,nuts and bolts mania" ;D
(https://images15.fotki.com/v1675/photos/4/3824994/14463210/Zusammenstellung_6-vi.jpg)
Further more, first printed parts are ordered for an experimental setup. They are just for proof of concept.
(https://images12.fotki.com/v1686/photos/4/3824994/14463210/IMG20250801WA0001-vi.jpg)
You can make out that the surface is quite irregular rather than smooth curved. I already tried to increase the resolution, but this is the maximum. Actually I do not know yet how to solve this problem.
How frustrating. -- Russ
Is it the resolution of the printer or of the stl conversion? I really feel your frustration!
(https://images20.fotki.com/v1691/photos/4/3824994/14463210/Facetres-vi.jpg)
It's already in the stl.file. With my clumsy CorelCad program I am able to modify the system variable up to the ratio «10» (normally I am working with the ratio «6»).
This increases the file size noticable, but in this case the outcome remains the same...
Quote from: Peter_T1958 on August 08, 2025, 03:11:00 AM(https://images20.fotki.com/v1691/photos/4/3824994/14463210/Facetres-vi.jpg)
It's already in the stl.file. With my clumsy CorelCad program I am able to modify the system variable up to the ratio «10» (normally I am working with the ratio «6»).
This increases the file size noticable, but in this case the outcome remains the same...
Hm. Have you looked into Autodesk Fusion? Its free for Hobbyists, and the free version have al the bells and whistles we need for making 3D drawings for printing.
Is this something that pops up in the STL, or is the problem already visible in the native file you are working with?
You might have asked the Oracle yourself, but here is what ChatGPT-5 have to say on the matter:
Eliminating Facets on Large Curved Surfaces in STL Files from CorelDraw/CorelCAD
The Problem
When designing 3D objects with large-diameter curved surfaces in CorelDraw or CorelCAD and exporting them to STL format for 3D printing, the resulting file may show visible flat segments (facets) along what should be smooth curves.
The issue is apparent in the STL viewer before printing, which means it originates during export — not in the printer or slicer.
Why It Happens
The STL file format does not store true curves. All curved geometry is approximated by a series of flat triangular faces. The smoothness of the curve depends on the resolution of this tessellation process — how finely the software divides the curve into straight segments.
Low tessellation resolution = fewer, larger facets → visible flat edges on cylinders, domes, and arcs.
High tessellation resolution = more, smaller facets → smooth appearance.
If the export settings are too coarse, even a perfectly drawn circle will look polygonal.
Solution 1 – Increase Tessellation Resolution in CorelCAD
CorelCAD offers commands and settings to control mesh smoothness when exporting to STL.
Step-by-step:
Set drawing units
Tools → Options → Drawing Settings → set to millimetres or your working units.
Ensures tolerances are scaled correctly.
Increase curve display resolution
Command: VIEWRES → set to 20000 (maximum).
Increase mesh facet resolution
Command: FACETRES → set to 10 (maximum).
Adjust STL export tolerances
Command: STLOPTIONS
Chord Height (Deviation): 0.01 mm or less
(Maximum distance between the mesh facet and the true curve)
Angle: 1° or less
(Maximum angular step around circles)
Output: Binary STL for smaller file size.
Export to STL
Command: EXPORT or _STLOUT
Select objects and confirm STLOPTIONS settings.
Result: Curved surfaces will have facets much smaller than the printer's resolution, making them appear smooth in both the STL viewer and the printed object.
Trade-off: File size will increase.
Solution 2 – Use a CAD Program That Keeps Curves Until Export
If you are working in CorelDraw only (without CorelCAD), curves are flattened early in the process, with no control over tessellation quality.
To preserve curve precision:
Export your 2D paths from CorelDraw as DXF or SVG.
Import into a CAD program that uses NURBS or parametric geometry (e.g., FreeCAD, Fusion 360, Rhino).
Extrude or revolve your shapes in the CAD program.
Export to STL, setting chord height and angle tolerances as in Solution 1.
Benefit: Curves remain mathematically exact until the very last export step.
Solution 3 – Post-Process the STL
If the coarse STL has already been generated and the original geometry is unavailable:
Use MeshLab → Filters → Remeshing, Simplification and Reconstruction → Subdivision/Smoothing.
Or use Blender to subdivide and smooth the mesh.
Limitations: This increases polygon count but cannot perfectly restore the original curve.
Key Takeaways
STL is always faceted; smoothness depends on facet size relative to printer resolution.
For CorelCAD: VIEWRES = 20000, FACETRES = 10, Chord Height ≤ 0.01 mm, Angle ≤ 1° are practical maximums.
For CorelDraw: export to a proper CAD program before creating the STL.
Higher resolution = bigger file, but no visible faceting.
If desired, a CorelDraw → FreeCAD → STL workflow can be documented that ensures mathematically perfect curves until the final export stage, completely removing visible facets in large curved surfaces.
Havard
Thanks a lot for your input. Up to now I never used KI to search for solving problems. Seems so I should change that habit... ;)
For CorelCad the advises are :
- VIEWRES = 20000
- FACETRES = 10
- Chord Height ≤ 0.01 mm
- Angle ≤ 1°
Although the commands are a bit different, I tried them out. Some were working orther failed. So I couldn't adjust the «chord high» and the «angle». Alas the result remained the same!
In my 3d-Tool viewer it was very easy to smoothen the curves, but (of course) this doesn't influence the original file.
3D-Tool Optionen Glättung anpassen 10.jpg
Perhaps I sould try to find a solution with "blender"!?!
I'm not sure how simple Blender would be assuming you started with an .stl.
I had a quick play myself and it wasn't easy. Very easy to smooth curves and to keep the desired edges sharp, but not both at the same time.
Starting with a quad based model would be easier I suspect. You really want to be sorting faceting before converting to triangles.
Quote from: Lawrence@NZFinescale on August 09, 2025, 05:55:28 PMI'm not sure how simple Blender would be assuming you started with an .stl.
You were right, that approach did not work! However, a brief look at the today's delivery showed, that things are not too bad. I removed the supports relatively roughly and especially the big fundation elements are still bent out of shape. At least it becomes obvious, that this would become a big gun...
(https://images14.fotki.com/v1688/photos/4/3824994/16713952/1000046126-vi.jpg)
(https://images14.fotki.com/v1689/photos/4/3824994/16713952/1000046130-vi.jpg)
The imperfection is barely noticeable and paint may further camouflage it. I also wonder how resin castings from such a master would look. In our little modeling society perfection is always the goal so I hope you devise a way to achieve it. -- Russ
Quote from: Peter_T1958 on August 11, 2025, 02:34:29 AMQuote from: Lawrence@NZFinescale on August 09, 2025, 05:55:28 PMI'm not sure how simple Blender would be assuming you started with an .stl.
You were right, that approach did not work! However, a brief look at the today's delivery showed, that things are not too bad. I removed the supports relatively roughly and especially the big fundation elements are still bent out of shape. At least it becomes obvious, that this would become a big gun...
That looks OK - Always good to get some paint on too as it's hard to really tell until you do, but paint generally improves things.
If you do decide you need things to be better, the approach I use (albeit for different reasons) may help:
Draw in CAD.
Export in a way that the parts (ie bolts/rivets etc) remain separate.
Redraw the parts in Blender that you need to modify based on the CAD pattern
Delete/hide the original problematic CAD parts and export as stl.
[/list]
This is the approach I use for wood grain on the wagon planks. The wagon is exported as OBJ (stl works too I think, though you may need to export as a more than 1 file). In the cad model planks are separate so I can export so that individual parts stay as distinct objects (a bit painful as there are many objects) or just export as 1 piece. If the latter the parts are still distinct in edit mode and easily separated. Redrawing a board is extremely easy of course. Adding grain and distorting/distressing boards is far easier on a plain board comprised of quads compared to a triangulated board that is unhelpfully complex due to surface bolt detail etc.
In your case you'd just be redrawing the parts where faceting is a problem. But hopefully you don't need to worry!
I found some time to continue on this project. That thing gets bigger and bigger. One point that is often overseen in kits, but at a calibre of this size it is absolutely necessary to replicate : the rifling. My idea is to print the inner lining of the barrel separately to avoid supporting structures.
(https://images12.fotki.com/v1694/photos/4/3824994/16713952/Zusammenstellung_8-vi.jpg)
Ok, the gun is fished, ammunition is also available. So I am ready for a first test-shots!
(https://images14.fotki.com/v1688/photos/4/3824994/16713952/Gun_5-vi.jpg)
(https://images49.fotki.com/v1692/photos/4/3824994/16713952/Granaten-vi.jpg)
Seriously now! Designing any subject in a CAD program is only one part of the whole task. Each part has to be re-thought as a kit part. Wall thickness, printability and assembling had been a huge problem for me at the beginning, but with increasing experience it becomes much easier.
And if I am uncertain, I create a «plan B» right from the beginning. Changings later on are always more labour intensive. That's why I made two cradles , a complete and a half shell one.
(https://images12.fotki.com/v1686/photos/4/3824994/16713952/Gun_5B-vi.jpg)
Please post a video when you fire the canon. And remember to fire it outdoors to avoid blowing up your house! -- Russ