Cura Scaling by Itself?

[Yoter 14]

I am running Cura 15.06.03. We have been printing building components sliced through Cura on our Ultimaker, we've been running these about three months with no problem. This week, I suddenly have a major headache. None of my parts are fitting together all of a sudden.

The models are made in Sketchup, and test fit in Sketchup. Before exporting the .stl, we are scaling them in Sketchup and checking the dimensions. After I bring them into Cura and slice them, I load them up on the Ultimaker and print, and they are typically smaller than they were in Sketchup. The building parts are modular, so we are basically just making changes to the same platform again and again, nothing we should be doing should be affecting the overall dimensions. Furthermore, I can re-slice the same .stl and it will return a different size the next print. I hate to admit, but we ran two or three of these models before I sat down to post-process and start painting and said "wait a second"... The differences are +/- 1/8", so they werent really apparent until we had them right next to each other. Wiped out a week's worth of printing.

Is there something I could have done in Cura to cause this? One reason I like Cura is that it requires clicking a button to the side to do any scaling or rotating, so it's hard to do accidentally. I printed an old Benchy gcode I had on a SD card and measured it with calipers and it came out fine, so I am tentatively ruling out the printer developing problems.

If anyone has any ideas, let me know. I sliced a model on Simplify3D this morning to double-check the printer itself. I'd really like to go back to using Cura, however, as the models have been coming out absolutely incredible and I would rather not change a thing if I can.

[gr5 2,070]

Sometimes sketchup saves things in inches and STL's have no units and Cura expects everything in mm so I simply multiply by 25.4 and everything scales perfectly and accurately.

The "errors" between sketchup and Cura should be an EXACT number like 10 or 25.4 (10 if sketchup exports in cm).

[Yoter 14]

I have seen that before. I selected millimeters and exported. I know Sketchup isn't the most reliable .stl generator out there, so I imported the .stl to 123d Design and re-checked dimensions. The weird thing is, the same .stl sliced three times gave three different answers. The model is supposed to be 8-3/8" length. One is 8-1/16", one is 8-1/8", and the final is 8-1/4". I just sliced the model in Cura 15.04 and started it, then paused after the first couple layers and measured it and it seems to be scaled appropriately.

I've got previous examples of this same model printed from the same .stl in the same program at the right scale, so I am not sure what exactly is going on. I thought maybe I'd thrown something off in the printer, but I printed a few Benchys and measured them against the dimensions online and everything seems correct there. I'll do some more checking with the current Cura and if I don't find anything, I think I'll re-install.

[Slive 0]

Cura is scaling you object if it thinks it will not fit on the plate. Even if it will fit after you rotate it right. It is annoying as hell!

https://ultimaker.com/en/community/view/16742-i-want-auto-scaling-turned-off?page=unread#unread

They want to fix this with a switch (turn off auto scale ) in the next release. Maybe it is already in the current release.

Slive

[IRobertI 516]

The answer here is "Don't use 15.06.03" [period]. It was a version that shouldn't have been released for general consumption. It's an early version of the new iteration of cura. There are newer versions of this new version of cura (which includes a toggle to turn auto scaling off) to be found here:

http://software.ultimaker.com/Cura_closed_beta/15.10/

Just be aware that these are very much beta versions, so expect bugs. I've seen the plans for the new version and it looks like it's going to be awesome, but for now, stay with 15.04.2 when you need reliability and try the new version if you're willing to experiment. The guys and gals over at UM are working hard on getting the new version stable and I'm sure we'll see a much more stable version very soon.

[nallath 1,117]

15.06.03 did scale automatically, just like the old version. The difference is that it did not -tell- you that it did (our bad!). The newest vesion (the ones IRobbertI linked to) does notify you and gives you an option to disable auto scale.

[Yoter 14]

Realized I forgot to return and update. A re-load did seem to fix my problem, but I went back to running 15.04 (I run some Printrbots, as well so I keep a version installed). All went well with the earlier release. I ran that for a week before I talked the boss man in to springing for a S3D license for the office.