Resizing to different scales

[rue_d_etropal]

I know that one feature of STL files IDs that resizing can be done at the post design phase, ie not necessarily as part of the original Cad Design .

Now there are obvious limitation such as walk and rod thickness. Reducing scale can result in breakages, and increasing scale can result in over thick walls and clumsy detail.

The CAD software I have used for 20 years makes it relatively easy to resizes designs and make adjustments a required. It does mean my designs have several versions mapping different scale ranges, but it doe mean that when asked I can usually resize any of my designs relatively easily.

Now there are others out the who offe some fantastic designs but possibly not in scales some would want. A few years ago I asked one designer if they could up the scale on some of the model vehicles and they said no. A pity as I think there was a potential market lost. 

It does worry me that some designers are not fully making use of 3d print design. Is it the CAD software they are using that prevents them resizing or something else?

Just wondering how many of the CAD packages out there can resize designs, and if they can not , then maybe they should. 

 

One thing you can always predict is that when you design a model in one scale someone will always ask if you can do it in a different scale. 

[monkeysarefun]

I design mainly model buildings and vehicles.

 

I've used both Sketchup and Blender and both allow resizing of the objects inside the file . This can be done either to the actual objects inside the file, or (in the case of Blender at least)  you can set a scaling factor during the export process. In addition any Slicer programme will allow rescaling  -  so you can choose where you want to do it, but like you say, inappropriate  thickness can then become an issue.  Blender however has an additional feature whereby you can easily adjust the thickness of individual objects via a modifier rather than actually having to physically adjust it for different scales.

 

One powerful feature of Blender is that it uses "Modifiers" . THese are non-destructive operations  that you can assign to an object in your file and it will do it "virtually" rather than change the original mesh. Hard to explain but in the case of changing thickness of say a wall, you can create the wall as a plane, then instead of using the extrusion tool to make it say 4mm thic  thus creating physical mesh,  you instead assign the "Solidify" modifier to it. In the modifier settings you enter the required thickness. THis value is easily changed in the modifier settings at any time so you can easily alter the thickness of all your parts just by altering this modifier setting assigned to them, thus you can set it to say 3mm for a OO scale print, then to 1.5mm for N.  The actual rescaling of the model as a whole can then be done either using the scaling factor in the Blender export window or inside the slicer programme. 

 

 

YOu can either apply the modifiers at any time   at which point the objects mesh is physically modified and the thickness created, or you can keep it virtual even through the export of the .stl or .obj file, just click the box marked "apply  modifiers" on the export screen.

 

There's a whole heap of these modifiers that do a whole lot of different operations ( including actual explosions!) and they are brilliant in that if you make a mistake or a change you just edit the modifier. For instance to cut a hole in a wall for a window do it using a Boolean modifier. If halfway through your modelling you realise that the window is 5mm too far to the left, the modifier allows you to simply relocate  the Boolean object to where you want it and the window opening magically  moves. Similarly you can simply resize the Boolean cutting object and the window will be automatically resized. If you use the same object to cut a wall full of windows, they will ALL be resized automatically in one simple step. 

 

It can become an interesting exercise to see how little actual physical mesh is required in an object. For instance I have often created entire 3D brick walls with inset panelling, windows and doors, and so on using just one single brick-sized plane. From that the rest of the  wall   - brick thickness, brick bond, inset panels, window openings etc is achieved by using the correct sequence of Array modifiers, solidify modifiers, boolean modifiers etc. 

 

Sorry that I got a bit over-excited about Blender and wandered off-topic a bit!

 

 

Edited October 1, 2023 by monkeysarefun

[rue_d_etropal]

It does sound complex, but in essence very similar to the software I use. Big advantage for one I use is that it is more like program writing, and has a start and end. There are tools to push and pull but I still prefer to edit the code. I say code, but it is more like a set of sub routines with me setting the parameters. It suits me down to the ground, but can sometime throw up problems which are difficult to fix, especially when resizing. For simple resizing it is just a case of adding one extra line of code. I have now even built in code which calculates minimum thicknesses required for a specified scale. 

 

[njee20]

I don’t believe there is any CAD software which won’t allow scaling. Any designer refusing to scale items is purely for the reasons you mentioned - parts either becoming too small and or unnecessarily coarse.

 

edit: I would be supportive of someone refusing to scale something though - I would never just hit rescale on anything beyond a very basic scenic model, because I think the results are poor unless you’re talking European N to uk N or similar, ie negligible difference. A piece of rolling stock that makes a good N gauge model will not scale instantly to OO without work IMO. 

Edited October 1, 2023 by njee20

[tebee]

In the software I use I can resize in multiple ways.  I can include a part or a collection of parts in another part and specify the ratio of original size to current size. I can adjust the size when I turn it into an STL file .It's also a parametric cad so I could write a formula to calculate the optimum thickness based on the size of the part. I don't use this as I'm printing to multiple targets ( a couple of Shapeways materials , resin printers and FDMprinters ) preferring to adjust manually. 

 

I do normally design things for 4mm scale  and scale up or down from there - I use more than the minimum thickness in most cases and can easily thicken a part when scaled down if needed.

 

Tom  

[rue_d_etropal]

Tom

Which software package are you using now?

I am still using the one( updated) you originally recommended to me.