Creating CAD for 3D Printing

[Crosland]

I have a reasonable idea how to use CAD software, but how do you create the models for rolling stock?

 

Start with a solid block and cut sections out?

 

Build it up from components?

 

Create a half (or quarter) and mirror if the design is suitable?

 

Does anyone have any good tutorial links relevant to railway modelling?

 

What about more complex models such as locos?

[Ian Morgan]

I find it is a combination of all the available tools in the 3D toolbox. extruding, cloning, duplication, lathing, etc to form components. I often use boolean difference to 'punch' holes in objects for windows, handrails, etc.  I use groups and layers to organise the various parts of the final model. The final model can be a collection of separate, but overlapping, objects and do not need to be joined or merged to form the eventual .STL file. All the objects do need to have a full compliment of 'faces' though, so they are 'watertight'.

 

It is quite different from creating models for a train simulator, where the poly count has to be kept as low as possible, unseen faces being removed, and curves being created from a few segments as possible. For 3D printing, it is only the overall size that costs - curves can be made smoother and more detail added at will.

 

Here's one I made earlier (well, over the weekend):

 

 

[richbrummitt]

Whatever makes sense to you is my honest answer: You find/learn the tools that give you the result you are looking for. The software I use tends to favour patterns or mirror/symmetry and I use this as much as possible.
 

There are some geometries that are difficult to produce. The hardest I have tackled so far was getting a belpaire firebox to appear correct. In the real world I presume the panels are shaped according to a template and made to fit. In the ‘precise’ 3D definition there are a lot of boundaries and tangents that upset the software or produce undesirable results. I eventually got to somewhere I was content. 
 

Ian’s horsebox model above has over 52,000 facets according to the software I imported it into this morning. 
 

What software are you using? 

[Crosland]

I'm open to suggestions on software. I have FreeCAD installed. I don't want to get hooked on Fusion 3D in case the free usage is pulled compleetly and I may want to make commercial use of it.

 

I got the impression that blender wasn't really CAD software but quite a few seem to use it. Perhaps I should try it?

 

I'm not sure about Sketchup (even though I have used it for other purposes) as it seems easy to end up with things that are not watertight or have internal faces that need to be removed.

 

Any recommendations welcome.

[Ian Morgan]

Everyone will recommend something different, I am sure. It is 'horses for courses', so you really need to have a look at each and decide for yourself which one you feel comfortable with.

 

Once decided, take the time to learn how to navigate round, switching your view, moving things, etc. With Blender there are different ways to use the mouse while pressing different mouse buttons, shift, Ctrl, etc, and, like driving a car, it needs to be done without thinking about it so you can concentrate on the model you are making. In Blender, I can poke shapes, and move them about with the mouse, and then feed in more accurate numbers for size and position and angles from the keyboard. It suits me, but I know others prefer scripting everything.

 

 

[Chris Higgs]

3 hours ago, Crosland said:

I'm open to suggestions on software. I have FreeCAD installed. I don't want to get hooked on Fusion 3D in case the free usage is pulled compleetly and I may want to make commercial use of it.

 

I got the impression that blender wasn't really CAD software but quite a few seem to use it. Perhaps I should try it?

 

I'm not sure about Sketchup (even though I have used it for other purposes) as it seems easy to end up with things that are not watertight or have internal faces that need to be removed.

 

Any recommendations welcome.

 

I attended a demo of Blender at a Shapeways training evening with one of their experts, it was hugely impressive. I just don't have the time to learn how to even scratch the surface of its capabilities.

 

Chris

 

Chris

 

[Valentin]

For a very short time, many years ago when it wasn't an online only application, I used SketchUp, for a couple of very basic projects. After getting my first 3D printer at the end of August, I wanted to be able to design my own 3D models so I tested two completely different programs: Fusion 360 and Blender. I started with the former and after some frustrations and many hours of video tutorials, I managed to build some very good models.

 

But, because I am a big supporter of Open Source software and Fusion 360 is not an open source software and AutoCad doesn't offer a Linux option, I tried Blender. After another many hours of tutorials, and more frustrations, I gave up! Blender is not for me.

 

I ended up with FreeCAD which, although very similar to Fusion 360 (both are parametric models of 3D design), has it's particularities. But, I can run it on my Linux machine, it's faster than Fusion 360, and, most important, allows me to create those models I always wanted.

[Edge]

Very much 'horses for courses' most certainly. All of my stuff is done in tinkercad, which being designed for children suits me down to the ground. Simple geometic shapes which can be solids or holes and adjusted down to 0.1mm. Entirely web-based as well, so no worrying about system specs or operating systems or the like

[MinerChris]

54 minutes ago, Chris Higgs said:

 

I attended a demo of Blender at a Shapeways training evening with one of their experts, it was hugely impressive. I just don't have the time to learn how to even scratch the surface of its capabilities.

 

 

 

Does this mean that you are moving (or thinking of,) away from OpenSCAD Chris?

 

Best Regards,

 

Chris.

[Crosland]

16 hours ago, MinerChris said:

 

Does this mean that you are moving (or thinking of,) away from OpenSCAD Chris?

 

Thanks for the tip

 

I took a look at OpenSCAD and like what I have seen so far, maybe due to my programming experience.

 

Does anyone else use it?

 

Is there a reason you ask if Chris is moving away from it  ?

 

[eldavo]

I've used OpenSCAD for a few things and as a programmer I find it fairly simple to use. I haven't attempted to use it for complex items like rolling stock but for bits of buildings etc. it's good.  I would expect things to start getting pretty messy with larger things as everything tends to get nested. You can break things into components though and it has a very useful feature for extruding a 2D drawing.

 

My current favourite is Designspark Mechanical which is available from RS components for free. Never have managed to get my head round Blender despite many tries. I suspect I'm just too impatient and hate going through tutorials. :-)

 

Cheers

Dave

 

 

 

 

[MinerChris]

3 minutes ago, Crosland said:

Does anyone else use it?

 

 

I know that @D869 of this parish also uses it to produce his tank wagons, and the occasional coach roof. Some bloke also wrote up a quick and dirty user guide in the 2mm mag in October 2018.

 

 

3 minutes ago, Crosland said:

Is there a reason you ask if Chris is moving away from it  ?

 

Sometimes I wonder about the amount of graphics memory resources it uses to do fairly simple operations. Re-rendering the entire model every time you make a change to a parameter is also pretty irksome sometimes, particularly when it's measured in minutes rather than seconds. The viewport also has some nuances that can make it annoying when you're dealing in sub mm units.

 

Best regards,

 

Chris.

[Chris Higgs]

2 hours ago, Crosland said:

 

Thanks for the tip

 

I took a look at OpenSCAD and like what I have seen so far, maybe due to my programming experience.

 

Does anyone else use it?

 

Is there a reason you ask if Chris is moving away from it  ?

 

 

I am not moving away from it. I don't have the time to learn anything else given the limited amount of my life devoted to 3D-Cad.

 

OpenSCAD is fine for what I do, which is mostly 3D extrusions of 2D shape (like coach roofs) or recilinear objects (like wagon bodies).

 

But it would never manage a BR Western, as an example . For such shapes Blender looked great. OpenSCAD can just about be persuaded to do something like the dome on a Gresley coach roof, buts its capabilities are being pushed.

 

Blender is like Concorde, looks like a lot of training is required to fly it! It could probably draw Concorde, come to think of it.

 

Chris

Edited December 2, 2020 by Chris Higgs

[Crosland]

Thanks for the replies.

 

4 hours ago, MinerChris said:

Sometimes I wonder about the amount of graphics memory resources it uses to do fairly simple operations. Re-rendering the entire model every time you make a change to a parameter is also pretty irksome sometimes, particularly when it's measured in minutes rather than seconds.

 

I have only scratched the surface so far, but, for me, OpenSCAD only renders when I click the button to do so, not when a parameter changes. The preview is a lot faster than rendering.

[MinerChris]

1 hour ago, Crosland said:

I have only scratched the surface so far, but, for me, OpenSCAD only renders when I click the button to do so, not when a parameter changes. The preview is a lot faster than rendering.

 

Hi Andrew,

 

Don't get me wrong, I'm not bashing OpenSCAD and it is the only 3D tool that I use. These issues really are just minor niggles and nusances I've run into once or twice before, not every time that I use it. If I had the time, just thinking about optimising how I build objects, and not being lazy when coding, I would probably solve these problems.

 

The preview will only get you so far down the build tree before it gives up (100,000 elements is the default I think.) It also throws up views like below when you get to edge sums. 100,000 elements sounds a lot, right up until you start compounding curves and circles together.

 

 

Best Regards,

 

Chris.

 

 

[Gingerbread]

I'm also an OpenSCAD user, though I've not yet got far enough to input one of my creations to a printer.

Its parametric approach seems to suit me, and appears to handle my current examples, mostly wagons.

As has been said here and elsewhere, I think it would struggle with complex curves, though I have seen Chris Higgs using it for a Belpaire firebox.

Rendering does get painfully slow, so I am currently using a parameter to include/omit most of the details for a quick preview facility.

 

David

[njee20]

I use Fusion 360. I like to start with a quarter and then mirror it to end up with a complete wagon. I start with a good drawing or picture of the end and the side, I usually start with an end on profile (drawn over the image) which I extrude to the correct length, and then start adding or subtracting bits to end up with something approaching the right design. Works well enough for me.

[Chris Higgs]

1 hour ago, Gingerbread said:

I'm also an OpenSCAD user, though I've not yet got far enough to input one of my creations to a printer.

Its parametric approach seems to suit me, and appears to handle my current examples, mostly wagons.

As has been said here and elsewhere, I think it would struggle with complex curves, though I have seen Chris Higgs using it for a Belpaire firebox.

Rendering does get painfully slow, so I am currently using a parameter to include/omit most of the details for a quick preview facility.

 

David

 

Rendering with wireframe set seems to just about make it not run out of memory.

 

The Belpaire firebox needed a lot of tricks and was painfully slow.

 

With my software development hat on, both Blender and OpenSCAd are open-source and so I shuld be able to modify them if I don't like what they do (warning: don;t try this at home unless you are an experienced C++ nerd).

 

Chris

Edited December 2, 2020 by Chris Higgs

[D869]

+1 for OpenSCAD (but you knew that already)

 

If you are happy getting your hands dirty with code then it's ideal - most of the tank barrel and rivets below were done with code - like spacing the rivets equally around the barrel and doing the 3d trig required for the rivets on the filler skirt. The top of the filler is a separate bit BTW. It's not all code - the vent and syphon bosses are rotated DXFs as are the domed ends on the barrel. Horses for courses.

 

 

I also use a lot of 'if' statements to allow me to do an assembly preview model pulling together DXFs from etch artwork with the 3d printed bits... and then use the same OpenSCAD model to render the parts (on sprues) for sending to the printers.

 

I suspect something similar is possible with Blender, Fusion 360 etc but once you know one tool there is less benefit in figuring out how to do the same things in another.

 

I do use a bit of Blender too - for posing views of rendered STLs and setting up lighting and camera angles to replicate prototype photos (and overlay the two for comparison). I find this a useful way to check dimensions when drawings are unavailable or don't fully answer the question. I have to refer back to my notes to remember how to work Blender every time though - I find it a pretty strange beast but its 'sweet spot' is more artistic 3d rendering, perhaps of organic shapes and also animation so perhaps it's no surprise that it's a bit odd to those of us more used to CAD tools.

[Chris Higgs]

Anyone worked out how to do the flare on a dome in OpenSCAD? I rather suspect it is beyond its capabilities.

 

Chris

[Gingerbread]

2 hours ago, Chris Higgs said:

Anyone worked out how to do the flare on a dome in OpenSCAD? I rather suspect it is beyond its capabilities.

 

Chris

 

Not yet, but I think I will need something similar (but simpler) if/when I progress to tenders, and similarly for the top corners of some of the GWR coal wagons, though any crude short cuts will be less obvious in them than in a dome.

 

David

[KeithHC]

I am slowly learning Onshape going from zero to first simple print in about a week. The reason I use Onshape is both my son-in-law and several of his work colleagues use it. They are all charted engineers working for a major uk aero engine manufacturer. Also we all have the Ender3 pro.

 

Keith

[D869]

9 hours ago, Chris Higgs said:

Anyone worked out how to do the flare on a dome in OpenSCAD? I rather suspect it is beyond its capabilities.

 

Chris

 

First work out the geometry of the flare on a dome. That seems somewhat tricky on its own. I struggled to do it with a file and some brass, never mind telling software how to do it.

 

At the risk of diverging well off the OP's question... I suspect it's do-able - at any point when viewed in cross section it's probably not unlike a circular fillet but the radius is small on top of the boiler and a good deal larger at its lowest point. Not all flares are created equal - some seem to flare so that they end up almost tangential to the boiler cladding, others hardly seem to bother much and have a fairly noticeable angle where they join.

 

So it seems possible to generate circles of varying radii and position them around the base of the dome in a manner not unlike my tank filler skirt rivets. Joining them up as 3d objects might be trickier... generating lots of spheres and subtracting them from a 'fat' dome might be easier.

[Chris Higgs]

10 hours ago, Gingerbread said:

 

Not yet, but I think I will need something similar (but simpler) if/when I progress to tenders, and similarly for the top corners of some of the GWR coal wagons, though any crude short cuts will be less obvious in them than in a dome.

 

David

 

The flares on a GWR tender I managed. By making the corners a separate part done by rotating the flare profile through 90 degrees.