Scaling issues between Blender and flashprint

Hi, I’m new to Blender and I’m still going through the tutorial suite. There are a few things I’d like to do with it but I’m starting out with 3D printing since I got one as a gift quite recently. I’ve found and read a bunch of posts about scaling issues and I tried using what I’ve learned from them but I still can’t get the scaling right. Flashprint from what I can tell only deals with mm and inches, so I’m trying to stick with mm. Currently I am using the starting cube object to get the hang of the scaling but have had little success with the goal being to print out a 1in x 1in x 1in cube.

What I’ve tried is this:
Under Scene, changed length to Metric.
Pressing ‘N’, I changed the dimensions to 1cmx1cmx1cm, including the units in the text fields.
I’ve been playing around with both unit scaling and and the .stl export scaling but the closest I’ve gotten was a cube with all dimension approximately 50mm smaller than they should be.

Some projects I have in mind are going to have to be printed in sections so getting the scaling right to make them fit together is very important so any help is greatly appreciated. I don’t write on forums often so if there is any information that I may have not considered let me know. Thanks.

There are multiple scales. Scale with real world measurements (dimensions) and object scale which is more of a multiplier.

When you scale an object in object mode or change the dimensions in 3d view properties, the object scale also changes. Doing that changes how the object is displayed but not the geometry, the mesh still has the same dimensions as it was before scaling. That’s why the object scale needs to be applied (ctrl+A -> scale) if it’s not 1,1,1.

There’s also unit scale, also a multiplier, which is what the exporter scene unit option applies to the mesh when selected.

.stl format, like most, doesn’t include units or dimensions, it includes vertex coordinates. 1 blender unit is 1 meter with the unit scale of 1.000 when switching to metric. With that the resulting coordinates in the file are 2 units apart (-1, 1). If you switch it to millimeters and apply unit scale when exporting, the resulting coordinates are 1/1000 smaller. Still have to tell the importing application what those numbers mean. Could be meters, millimeters, inches, feet, fingers, toasters, whatever options the application has.

The scale is arbitrary up until the point you’re trying to specify what size of object needs to be printed. You could model in whatever scale to have a comfortably sized object in the viewport, but would suggest having that whatever be a multiplier that is easy to remember, or an order of magnitude. That way you can scale the object for exporting, apply object scale, and then export.

Sorry, I’m a programmer by trade so this is proving to be a little confusing. I’m used to answers like ‘set this to that’ or ‘use this function instead of that function’ and then just applying them to later issues. I’m having trouble understanding what I should and shouldn’t be modifying. The scale that is under the option where I choose Metric or Imperial: do I leave that alone or modify it? The scale when I export is supposed to be changed to .001? I don’t think FlashPrint provides a way for me to help it understand theblender vertices. It has it’s own scaling tool if that’s what you are referring to.

object mode, select object, ctrl+A -> scale
file -> export -> stl, leave scene unit unchecked
import, and the dimensions should be in the unit the application expects.

this suggests it expects inches https://nyjcdiscover.files.wordpress.com/2015/06/flashprint.png
so the resulting dimensions should be your object dimensions in blender (in whatever unit) now as inches in flashprint.

If you export with the ascii option checked, you can open the .stl in a text editor and inspect the coordinates. Default cube (2x2x2) should have the coordinates 2 units apart (-1, 1), which should mean it import as 2x2x2 inches object. If it’s expecting mm instead, then it’s 2x2x2 millimeters.

Okay I’ll give that a try as soon as I get off work and let you know. I still got two hours to go :frowning:

So I did Ctrl-a and selected scale, in object mode with cube selected. All it did was have a window pop up on the side with three checkboxes, one of them being Scale (and checked).
[ATTACH=CONFIG]478533[/ATTACH]
Any attempt to interact with the object makes the window disappear and replaced with the translate window.
I think the ascii is correct:
[ATTACH=CONFIG]478534[/ATTACH]
But when I load it in flashprint it comes out super tiny, rather than inches it was in millimeters.

however it seemed to accurately translate the bl into mm like I was originally trying to do. So i tried a fresh cube on a fresh blend file and did NOT set length units to Metric (left at none, like my very first attempt) and then played with the size a bit and sent it to FlashPrint and it seems to translate fine now. Im not sure what I was doing wrong, going to print the model out and see if the translation holds.

The attachments don’t work and I get the sense you’re not even reading my posts. Normally I would stop writing them just after the previous sentence since the scale issue is your problem, and me wasting my time would be mine.

As much as I hate working with “I did something, not sure what I’m doing wrong” as the only information, especially after explaining quite thoroughly what is happening and giving exact steps after that, I’ll assume it’s not intentional and just a case of not getting it. Most likely because the information wasn’t given clearly enough


Object mode, both objects have been scaled so the dimensions are 1,1,1 (#1), both in numbers and when viewing it visually against the grid. This changes the object scale (#2). In edit mode we’re not manipulating objects anymore, just the contents of one object, the structure/geometry. In this case it’s a mesh type object, and what is shown in edit mode is its mesh. When the object scale is anything but 1,1,1, the mesh dimensions don’t match the object dimensions, so in this case the default cube was scaled in object mode, but the edge lengths are still 2,2,2 (#3).


Applying the object scale transfers that scale to mesh dimensions, so now they match.


From left to right:

  • I’ve made a cube that is 1,1,1 kilometers by setting the scene units to meters and the unit scale of 1000
  • in the exporter dialog I’ve set it to not apply scene units, so it uses the scale number above
  • which is why the resulting .stl doesn’t have big numbers in it, but still has the expected coordinates of -0.5, 0.5, the vertex locations in the scene and those match the magnitude of the dimensions

If I selected the ‘apply scene unit’ on the exporter options, the coordinates would have numbers like -500.0, 500.0, as in 1000x because of the scene unit, and because 1km = 1000 meters.

The file doesn’t have units or dimensions stored anywhere. The importing application can use whatever unit it pleases when it interprets the coordinates. It’s up to it to provide you enough options to change it, or you having to fight it on the exporting side.

Edit:

The information is correct and uses actual terminology. Not 3d printing specific but worth a watch, if haven’t already.

I’m a software developer, trust me I hate that phrase more than you do, but sometimes it just happens and it makes me angry cause I can’t figure out why. As for the attachments I don’t know why they didn’t work, there’s nothing more straight forward than an insert image button.
I’ve already read your last post and it makes sense now, but for the sake of making my last post understood I’ll try uploading the image again.
I pressed ctrl - a, this happened:

No text fields appeared and if I tried to interact with the object directly the window disappeared. And I know the difference between edit and object mode. Not once did i ever set foot in edit mode.
As for my last post it finished printing and it came out the right size.

Apologies for having you go the extra mile to ex plain this to me, but people with a certain analytical mind set, especially programmer, it helps to have to good step by step instructions in detail. Why do you think programming tutorials are so long and cover a lot of things for just one topic :p.

That’s the operator panel you’re showing. It shows the options for the last operator which disappear after you do something else, because the options for the current one takes their place.

Object scale is quite hard to understand, and explain, because there’s no good real life equivalent. I also know things are harder to explain and understand without visuals. Screenshots of the full interface help explaining when asking questions, an example .blend helps to relay most information for collaborative troubleshooting, and the file is used to produce visuals when communicating back.

But when you’ve participated in thousands of threads that have to start with squeezing the information out, “show screenshots and post a .blend”, it’s not fun anymore. Easier to not even read the threads if they don’t contain enough information, or save time by not producing visuals when there’ s no existing ones to draw on or .blend file to take shots from.

Learned a lot from troubleshooting all kinds of issues but the off chance of learning something new is further and further away. Not very productive to learn something new when the process is unnecessarily painful. A bit like having to go through all the material from the primary school each time you want to learn something new about computer vision.

The issue can be solved with communication, which is why I made the tutorial linked in my signature. I think this is the most valuable thing I’ve learned through posting on a forum that focuses on visual arts. A piece of art and communicating anything, even technical stuff, have a lot in common. Art is surprisingly technical for one, but the goals and mechanisms are also similar;

For example, context and the story is important in both to be effective. There has to be a start, then continue to the point, and describe where it’s going. “There’s a girl who’s a princess and she’s a bitch” is not a good fairytale, similarly “I did something and it renders black, what could be wrong” is equally crap.

Composition rules apply to text. We’re using paragraphs to have a visual separation in the flow of information we’re putting out. No difference between a piece of artwork and communicating something technical, although visual communication wins against wall of text every time. Cleverly using both should be most effective.

Ironically a wall of text is what this post has become, but thought I write these. Might be something to consider if you look more into visual arts, as communication can be something that helps you in your work, not just hobby. http://www.davidrevoy.com/article242/what-skills-are-needed-to-draw