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Marneus68

Print larger than expected

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Hello,

We recently acquired an Ultimaker 3 Extened at work, its higher vertical resolution is an important criteria for us. One of our prints is roughly 29 cm high and it looked properly scaled in Cura, however the resulting print ended up being a whole centimetre taller than expected.

I had to slightly increase the material extruder temperature (210°C for PLA) and the bed temperature (75°C) to avoid warping problems on the print and brims and the brims not sticking to the bed plate properly. This was inspired by the answers provided in this topic: https://ultimaker.com/en/community/6153-pla-not-sticking-to-the-bed-and-warping.

Is there any possible cause for that size discrepancy between the model and the resulting print.

Best regards;

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Two unrelated problems. The "stick to bed" issue is most likely that you need to level a little closer. It's safe to just turn the 3 bed screws 1/4 turn CCW. More info in this video:

 

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The height issue is much more serious. First check cura as that is more likely the issue. Sometimes cura rescales objects. Click on the object and choose the "scale" icon in upper left and make sure it is scaling to 1X or 100% in all 3 axes. Also look at the height - I believe in that mode it shows the height of the object in mm.

Another possibility is that the part is sunk into the glass. This is a great feature but people don't realize that when they do another print late the feature is still turned on. And thirdly after the gcode is generated open it in a text editor and skip to the bottom and search upward for " Z" (space Z) a few times to see the last layer height commanded that printed also. In mm. This should be equal to the height.

If all that is correct then something is wrong with your machine. steps/mm is off or something. Contact your reseller. Is there other evidence that the Z axis didn't move for some layers - if so they will stick out like a hat brim (but not so much).

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Thanks a lot for taking the time to answer my question;

 

The "stick to bed" issue is most likely that you need to level a little closer. It's safe to just turn the 3 bed screws 1/4 turn CCW. More info in this video:

Thanks for linking me to this video, I was probably not clear enough in my OP. I initially had an issue with the brim being ropy and not sticking to the bed but I fixed it by making the bed slightly hotter. I will attempt the other techniques in the video you linked, including the trick with the screws. Thanks for pointing that out.

 

First check cura as that is more likely the issue. Sometimes cura rescales objects. Click on the object and choose the "scale" icon in upper left and make sure it is scaling to 1X or 100% in all 3 axes. Also look at the height - I believe in that mode it shows the height of the object in mm.

I paid attention to that after ending up with a print at a totally wrong scale in an earlier attempt. I'm pretty sure the scale and sizes shown in cura were the proper ones for that print.

 

And thirdly after the gcode is generated open it in a text editor and skip to the bottom and search upward for " Z" (space Z) a few times to see the last layer height commanded that printed also. In mm. This should be equal to the height.

I still have the gcode of that print and after a cursory search it seems that the Z size for the last layer are the correct ones.

It seems that the piece has been put hot water to get rid of the support material and I'm noticing that it warped the print in places. Could the hot water used to remove the support material have caused the print to "expand" somehow?

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I think the recommendation is *warm* water, not hot water. If the temperature exceeds ~60 degrees, the PLA will start to soften, and the object can deform.

That may be the cause then, we'll be trying another print soon. I'll be more careful when removing the support material.

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Maybe measure the part height before removing the PVA just to test your Z accuracy.

Actually keep the water below 50C. PLA softens around 55C (13:29 in video).

75C bed for PLA causes other "warping" issues (but only on the bottom 2mm or so). Stick to 60C. The Ropy problem should have been fixed by fixing leveling instead of using temperature. Again - in the video.

I know the video is long but I spent many hours trying to keep on topic and cutting out a second here and there and keeping the video as short as possible and still interesting. There's just a lot of details to go over to understand not just "how" but "why".

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75C bed for PLA causes other "warping" issues (but only on the bottom 2mm or so). Stick to 60C. The Ropy problem should have been fixed by fixing leveling instead of using temperature. Again - in the video.

I know the video is long but I spent many hours trying to keep on topic and cutting out a second here and there and keeping the video as short as possible and still interesting. There's just a lot of details to go over to understand not just "how" but "why".

Like I said I'll try everything that doesn't involve making the bed too hot on my next print. The video is great, don't worry!

I printed a smaller piece yesterday by fixing the leveling and it came out exactly as expected, so I can safely say that my scale problem is no more.

Thanks everyone for the help.

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