# Scaling a model could be better

I’ve been bouncing back and forth between Luban and Cura. I’d prefer to use Luban because the simplicity of the software is preferable for my needs. However, I have encountered one major thing that could be better – object scaling. Currently Luban only allows for scaling by percentage. While it’s not impossible to figure out the scaled dimensions of an object by percentage, it’s much easier to just enter those dimensions. For example, if my imported model is 55.76mm high, and I want it to be exactly 200mm high, I’d like to just enter that value instead of having to figure out the math.

I have forward your request to our Luban team. They will evaluate it.

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In my opinion the scaling function in Luban is intended to compensate for e.g. shrinkage. Changing the scale of a model should be done in the design software.
Leave it as it is.

@Snapjehet … it’s intended to “compensate for shrinkage”? Ok, let’s assume the software stays as-is and I scale an object from 100% to 200% – the model was 10mm and it with scaling it should be printed at 20mm.

How is scaling an object by 200% any different than just indicating 20mm as the final scale? I still have expectations that the model will end up as 20mm.

To put it another way, let’s say I found a really cool sculpture I’d like to print from Thingiverse. I import the model into Luban, and it’s tiny – 5mm high. I have a bookcase where I’d like to display the scuplture and I have 150mm of vertical space to fill. When I measured the space, I didn’t use a percentage measuring tape because as far as I know, there is no such thing? Then I go into Luban, and now I’m faced with a calculation to figure out how to get the model from 5mm to 150mm. The calculation is simple, yet completely unnecessary.

One more thing to consider … how many numbers should I round my scaling percentage to? Ten, hundred, thousand, ten-thousand? Assuming your Snapmaker is spot on accurate (which is likely not, but that’s another conversation), rounding can introduce a piece that’s not the right size. Side note, a rounding error is how the Space Shuttle blew up. Ok, we’re not launching space ships, but it’s worth noting that rounding can cause inaccuracy.

Scaling by percentage or scaling by size – it’s all scaling. There’s a reason that Cura defines scaling by size and not percentage … it just makes sense.

Also, scaling of a model in the design software can only be done if you have the model file and software to edit the file. Many people are just grabbing .sitl files from Thingiverse and generating g-code in Luban. You’re solution to scale in the design software adds an unnecessary step.

I’ve been doing software UI/UX for more than 30 years. Frankly, I can only think of one other product that I’ve used which does scaling only by percentage and I don’t use it today because I found it to be cumbersome.

@VaughnDTaylor

while cura allows for that, the fact remains that if the dimensions need to be changed it should be done in the CAD software used to create it in the first place. Scaling non uniformly will distort other features, such as round shapes for example.

Cura has both ways to define it, percentage OR dimensions.

There are TONS of FREE design software. Blender for example is a very good one. And if you don’t have the model file, how are you getting it into Luban in the first place? That requires having the model file too… just because it’s in STL form doesn’t mean you can’t import it to edit in CAD software, especially since STL is so common, virtually all CAD software I’ve seen supports it.

In the end you’re asking for something that will distort details of the model if not done uniformly.

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Yes I know. So let me amend the request. We should have both scaling options, and I should be permitted to distort the scaling however I like.

What I’m trying to do is avoid using a non-native piece of software by suggesting improvements. When adequate options are not available within a piece of software, people will stop using it. Hence so many people using and recommending Cura for slicing. This is neither good for the end user, nor for the company.

I’m failing to understand the reluctance to add additional functionality where there are obvious omissions? I’m not requesting that Luban be made to function identically to Cura — I’m just asking for an additional scaling option.

You seem to be missing the point. There are tons of resources that provide STL files. With those files, I can bypass design software and go directly to slicing. This may not be your chosen workflow, but it’s not an unreasonable workflow for someone who is just printing other people’s work and has no interest in learning modeling.

If Snapmaker is supposed to be the bridge that brings more people into 3D printing, then this scenario is not unrealistic.

I think it’s worth explaining the origin of this request and the real-world event that brought it about last week. Maybe then there won’t be so many questions?

The head was created in Blender using Face Builder (a paid plugin) which allows for mapping of a wireframe onto photos taken 360 degrees around a subjects’s head. The result is a 3D wireframe which can be exported as an STL file.

I did not create this model. It was created by a digital sculptor. Even if I could modify the model I would not because it’s not in my wheelhouse to do so.

So, what is this being used for? My wife works in the film industry – specifically in FX. I am an independent contractor, and I occasionally do work for her FX company. The company will take the 3D printed piece, add 3D epoxy to the surface for smoothing, add any additional items (eg. scars, cuts, pimples, etc), create a silicone mold, then vacuum form promotional masks.

I was tasked with scaling this model up to a very specific dimension then printing it. After I handed over the print, the company asked me if I could slightly modify the dimensions of the print. They wanted it to be 1" taller, and 1.5" wider because after they made the prototype it was too tight on the face. The original model has a very slender face, so it would not fit most people well.

I could not go to the digital artist that created the original model – I was told she was on a different project and I’d have to resolve the issue. I have blender, but I don’t have the paid plugin nor the original photos used to create the model file. Also, I was told not to play around with her model.

So, this brings me back to my original problem:

1. I need to print an STL file that was created by someone else
2. I cannot modify the model
3. I need to scale the model to a very specific height and width
4. I need to slightly distort the model’s original proportions
5. Luban does not allow me to do what I need to do, but Cura does
6. Distorting the model in Cura did not change the integrity of the 3D print in a way that was noticeable

This is just one example of how 3D printing is being used – I’m sure there are many more. But, I hope that you understand why I’m asking for a modification to how Luban works? I’d prefer to use Luban, but if it doesn’t meet my needs, then I’m forced to use Cura.

@VaughnDTaylor again if the scaling isn’t done uniformly in all directions. Are you only wanting to scale in one axis without scaling the others by equal ratio? Or are you only worried about the height being exact and letting it scale the other axis’s equally by ratio not caring what those end up being? If the latter is the case then your method and request is perfectly normal and reasonable. But if the former, only one axis without resizing the others, is what you want then you need CAD software to edit the model that way so it doesn’t distort the features.

There’s also the fact that Luban’s slicer engine is actually a heavily modified version of an older version of Cura’s slicer engine. I’m not trying to argue nor do I want to, I’m only trying to help.

What I’m saying is that I understand that the model will have some distortion, but that’s not important for the final product. I’m also saying that I need the height to be an exact measurement.

As far as the slicer’s engine, that’s not the issue. I have no issues with the performance. I have an issue with the lack of features available in the UI.

I understand you’re trying to help, no worries.

@VaughnDTaylor i agree, Luban is very lacking. I only use it anymore just to connect to the machine and use console commands. It’s more of a program with enough features only for beginners, making others like us forced to use other programs to bring out the true potential of the machine.

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I suggest you give this feature request on github a like: Scaling in mm · Issue #709 · Snapmaker/Luban · GitHub (enable scaling in mm)

And the scaling screen already has a checkbox “uniform scaling” that you can toggle to scale in all dimensions or just in a single one. The only issue you have is that you have to do the math to convert actual size to percentage. Which I think is a doable workaround in the meantime.

(Or just use a more advanced slicer)

Or, probably easier: install Microsoft 3D Builder (there was a time it was installed automatically with windows) and use that to scale. That one does allow you to scale the way you want, including just filling in the desired size and save the stl in the new size.

I’ve given it a like on Github. Thanks for pointing that out. I’m on a Mac platform so unfortunately the MS 3D Builder will not work for me.

@brvdboss 3dbuilder can be fun to mess with, it actually has a cool embossing function that makes it easy to engrave/raise lettering on a model. It’s future is uncertain unfortunately, with Microsoft caught lying about Windows 10 being the last and Windows 11 being confirmed and just on the horizon because of an inside leaker. Those of us that know software all knew it was coming. Technology changes too fast, and software needs change with it.

@VaughnDTaylor heres an article for both the best free and best not so free modeling software for Mac if you ever do decide to delve into the dark rabbit hole that is modeling.

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As an alternative I would recommend to use Meshmixer:

that is available for Mac, but has a little bit of extra complexity if you just want to scale.

Then again, if you’re using this professionally, I would consider switching to another slicer anyway. (I am personally a fan of prusaslicer) which offers scaling by size out of the box.

I don’t have any understanding of why that would have any impact really? (And it’s not like I would consider Luban development more reliable in any way)

@brvdboss I was just saying 3D Builder can be fun, but it’s unknown if it’ll be around after support for Windows 10 ends in 4 years. It’s unknown if it’ll be available for Windows 11 or not.

I actually do 3D modeling with Sketchup. But I haven’t found it to easy to create 3D models for print using Sketchup – it seems more adapted to hand constructed builds?

This is an example of a Sketchup model I designed, then recently turned into a tangible object. Basically, I built a workstation around my Dewalt jobsite saw, and my router (at this point, I was not finished – still needed the drawer and electrical. Need to take new photos.)

@VaughnDTaylor honestly I’ve never used sketchup. I heard it can also be a slicer though. Is it a parametric modeler?