Cura Question - Page 1
Forum section: electronics / general

author: bostonman
author_rank: Super Contributor
timestamp: May 08, 2022, 11:51:35 pm
content: On McMaster-Carr they allow to download a STEP file for parts. Currently I'm looking at a bolt (part number 92820A550):https://www.mcmaster.com/browse-fasteners/thread-pitch~1-5-mm/length~40mm/length~41mm/head-type~hex/screw-features~flanged/thread-size~m10/flange-diameter~21-mm/I don't have software that allows me to convert the STEP to STL, but I found online websites. When I did this, Cura opened it and automatically scaled up the part to a ridiculous size. I turned off auto scale for small parts and the part opens as a very tiny size.I'm trying to figure out why Cura is doing this or whether the STEP file can't correctly be converted to STL.

author: Ian.M
author_rank: Super Contributor
timestamp: May 09, 2022, 01:35:34 am
content: FreeCADcan import that .STEP file (Create a new document, select 'Parts' workbench then do (from menu): 'Part' -> 'Import CAD...'). Poking around with a measure tool gives sane dimensions for it. Exporting (File menu) as STL gives a STL file that opens in Cura 3 and appears to have sane dimensions. OpenSCAD can also import the resulting STL file, with correct dimensions. Therefore I think the problem is with your online converter. FreeCAD converted STL file attached.

author: bostonman
author_rank: Super Contributor
timestamp: May 09, 2022, 01:57:38 am
content: I tried two different websites, and, ironically enough, they both saved as the same file size, so I thought it was something with Cura since I'm new to using it.The cheating work around was that I scaled it up by the percentage it seemed to be wrong by, but it didn't make sense doing this.I'll try converting the STEP file(s) in FreeCAD to practice, but thanks for converting it.

author: Ian.M
author_rank: Super Contributor
timestamp: May 09, 2022, 02:10:45 am
content: I suspect both your online converters are using the same rendering engine. Another possibility is something hinky in your Cura settings - 3D printing slicers customarily uses the millimeter as the unit of length, and STL files are unitless, so if you've done something that changes the default there's the possibility for a scaling error. As I don't use the current version of Cura (as Cura 3 was the last version that could be installed and run entirely offline), I cant be much help finding what it could be. As you are flagged USA, maybe you have it set for inches, or thousandths thereof?

author: bostonman
author_rank: Super Contributor
timestamp: May 09, 2022, 01:46:51 pm
content: The units make sense, I'll have to check.I haven't used Cura much at all as I recently came across a throw around Win7 laptop that I've been using to tinker with 64-bit related software.Usually I use another slicing software that I like, however, it has quirks; and Cura is the more popular one. I'll check the unit settings, but also trying to work out some other quirks.First I noticed the printer didn't home, and needed to enter some g-code in Cura. Now the printer homes, but after it heats the bed and extruder rather than before it home'ed after the bed and before the extruder. Also, the speed was horribly slow and thought I set all the settings to mimic the other slicer software.

author: Ian.M
author_rank: Super Contributor
timestamp: May 09, 2022, 02:05:10 pm
content: Its easy enough to check. If Cura imports my STL of the bolt (or a STL of Benchy etc.) at the right scale, its those online converters, or the settings you entered when using them. OTOH if your Cura has gross scaling problems with a known-good STL file, its FUBARed Cura settngs.