CAD Software Why is it so difficult to revise 3D print files?

[mrwalsh85]

I have been playing with Inventor and exporting STLs for 3d Printing using Cura.

Early on, the files were printing very small. I finally found the export properties and it turns out my files were being exported in metric, so if it was a 3" round object, it'd print 3 inches in diameter (or some scale thereof).

Exported the file, and it worked pretty good. Awesome.

And now it won't export properly again. Currently theory is that each time I export a file as a STL, somehow the original file is being modified and re-exported, messing up the scaling. It is apparent that this is happening when it is imported into Cura.

I decided to re-draw and save the file as a master file, and I will make my revisions from this master file. I won't touch this master file except to save-as > updated rev number.

This will be my starting point. My dad does the 3D printing for me as I don't really have time to fiddle with it, and honestly, I think he enjoys it more than he lets on... LOL. I've sent off the files to my dad with this new file and hopefully it imports OK. If so, I know what to do from here on out.

I am so close to finalizing my av-bay concept design and if this works, I will be able to scale up to different body tube diameters. I've got a Wild Child begging to be flown with GPS. The concept drawing is for a 29mm rocket that I want to put a H13 in

Anyone have problems with exporting and files being manipulated somehow in the process?

Appreciate any input you can provide, while I wait for feedback from my dad.

Thanks!
Mike

 

[SpaceX76]

I have never had any problems importing or exporting .stl files and i have done 100s of them. My theory is that Inventor includes some parameters in the .stl that Cura does not know how to properly handle.

 

[0011001100]

Inventor defaults back to inches every time you close and open the program. Otherwise there shouldn't be an issue, though I have never used Cura. I have been using Inventor for a few years.

 

[Michael L]

I've never had export / import issues but tolerances can give you fits. Ie lets say you have a part that is 6.251 mm (use inches, doesn't matter). The 3D printer is not going to hit those tolerances. Some filaments are worse than others. I use parameters when I make the part, print a small piece of it, test fit it, edit the file, try again until it's right.

Parameters (In Fusion 360) look something like this for a centering ring:

OD = 4.21mm
ID = 2.21mm
Thk = 6mm

Prusa Slicer likes metric units so I do all of the design in metric. It's just a number. Imperial and metric both reference the same standard. And yes, I have to use a converter sometimes though 25.4mm per inch is pretty easy to remember.

 

[mrwalsh85]

My coworker opened the file on his Inventor program and it turns out that his opened up with all the measurements in metric. We re-opened the file and checked under option, it was selected to open as metric... We changed to inches and it gave us the right numbers. So i will have to see if Cura has this option/issue also. Otherwise I will have to start thinking in metric as you all said. Shouldn't be hard as I work in a metric workplace...

 

[Bravo52]

Prusa Slicer likes metric units so I do all of the design in metric. It's just a number. Imperial and metric both reference the same standard.

I use the Prusa slicer as well and the thing I like about it is it will switch between standard and metric on the fly. On the platter tab in the "object manipulation" box (right side of screen) there is a simple check box that will jump between the two standards...

 

[beeblebrox]

I have had bad results with Cura, I have been using Simplify 3D. it is far superior. If the software thinks the model will be too small, it asks you if you want to change the units. If a part you want to print is small like 3/8" it might think it is the wrong unit and asks you. You can accept it or have it resized. But with any slicer, you can set default units and when the object is on the build plane, you should be able to see if it is the correct size or off by a factor of 25.4:1 If it is off, rescale it or check your default units and re-import. For simple mods of a file, it is much easier to import into Tinkercad and fix it there. You can mod it, scale it, whatever, very easily.

I use English units for everything for two reasons... 1. My accurate dial caliper is English units 2. Body tubes from every source are measured in English units.
It is curious that all the motor diameters are metric... Stemming from original fireworks casing sizes.

 

[mrwalsh85]

Thanks for the tip. Will look into it.

I sent my dad the metric versions, and none of them worked. They opened to a scale of 10k%. Scaling back to 100% yielded a very small part.

I watched a youtube video where the CAD creator exported in a different set of units (instead of millimeters, they exported in meters, or something to that extent). So I've exported both as Meters and Micro Meters to see if it gives me anything different. I just want to get a step in the right direction.

Thanks for the input

Mike

 

[SpaceX76]

Thanks for the tip. Will look into it.

I sent my dad the metric versions, and none of them worked. They opened to a scale of 10k%. Scaling back to 100% yielded a very small part.

I watched a youtube video where the CAD creator exported in a different set of units (instead of millimeters, they exported in meters, or something to that extent). So I've exported both as Meters and Micro Meters to see if it gives me anything different. I just want to get a step in the right direction.

Thanks for the input

Mike

Do you have correct printer and printer settings setup in Cura. It sounds like the units you are using in your cad software are different then what you have setup in cura. I have also sometimes seen if you have all the correct settings, units, ect that cura makes the models in the preview tab smaller then they are when printed.

- edit: I should have done some more research before opening my big mouth. You cant change the units cura uses, the only way to change the units from MM to IN is to use a plugin from the marketplace.

 

[mrwalsh85]

A bit of a revelation. Using Inventor gives us access to the 3D Print plugin. Another colleague explained that he uses this feature to export the STL, and I tried it, and it prompted me if I wanted to change the units or use the 'source units' which is a new option that I haven't seen before. So I think this might be the ticket. I've sent to my dad and hopefully get an answer tonight... Might just be the ticket!

 

[Howitzer]

Oh! A topic I can help with!

Create a metric .ipt template. Go to document setting and set it to metric. If you want to draw in inches just put "in" at the end of the dim you input. Save the template and use it for any of your 3D printing models. When you save the part as an STL file, under options in the save window you can also choose which units to save it as.