<p>I'm printing on an Ender 5 with the default flex/magnetic build surface.
I read that PLA and PETG may sometimes be printed without any bed heating at all and also that bed heating is the main contributor to the power consumption of a printer.</p>

<p>As I do see that bed heating definitely helps with the first layer adhesion I did not want to turn it off completely, but I did start experimenting with turning off bed heating after all solid bottom layers have printed (using the ChangeAtZ script in Cura) and so far I haven't seen any negative effects, especially no warping (I am usually printing with a brim or raft; I think that might also help in that regard).</p>

<p>Am I missing something? Why is <em>anyone</em> keeping the bed heated for an entire print?</p>

[{'answer_id': 10684, 'author': 'r_ahlskog', 'author_id': 14957, 'author_profile': 'https://3dprinting.stackexchange.com/users/14957', 'pm_score': 2, 'selected': False, 'text': '<p>All the valid points of bed shrinking and dislocating your parts when cooling from the other answer aside there is also the added complexities both in testing reliability of such a thing that may or may not be applicable to all materials.</p>\n\n<p>The added complexity to the slicers to figure out when it is safe to turn off the bed which I would imagine depends on part footprint. I also sometimes print several parts sequentially in the same job so then it would need to know that and time the bed heating correctly or pause and wait for bed between parts.</p>\n\n<p>I would also categorize printer power use as trivial (order of three 60W lightbulbs), but considering millions of machines worldwide economics of scale does kick in.</p>\n'}, {'answer_id': 10685, 'author': 'Pᴀᴜʟsᴛᴇʀ2', 'author_id': 11242, 'author_profile': 'https://3dprinting.stackexchange.com/users/11242', 'pm_score': 6, 'selected': True, 'text': "<p>There are three reasons (I can think of):</p>\n\n<ol>\n<li><p>A large problem you'd face with allowing the bed to cool after first layer is you stand the chance of losing adhesion after it cools. When you heat the bed, it expands somewhat. When it cools it contracts. It has been known for parts to actually pop off the bed if left on there to cool (after a print). If you allow the bed to cool fully, you could ruin a print due to it losing the adhesion, popping off the bed, then the printer keeps on going. </p></li>\n<li><p>When you're dealing with 0.1&nbsp;mm layer height, that's not a lot of wiggle room. When you level your bed before printing, it should be done after everything is heated. If you were to turn off the bed after you start printing, you could very easily shift the bed enough to take up the worth of an entire layer, which means your print has adjusted and will then have major imperfections. This isn't a <em>given</em>, but definitely a concern ... especially for larger or taller prints.</p></li>\n<li><p>Whether PLA or PETG, the extruded filament needs to have heat in order to stay. This is not only heat in the extruder, but heat in the print itself. If the print cools off, this could affect subsequent adhesion for the filament getting laid down. If you turn the bed heater off after print start, you'll lose that heated environment. The print will cool off and you'll start seeing variations in the print, which, if the print is large enough, would most likely be more noticable. Think of it as a heated environment, not just putting piling host plastic on top of each other.</p></li>\n</ol>\n\n<p>There may be other reasons, but I believe these are <em>very good</em> reasons not to turn your bed off after print start. If you are worried your power supply isn't providing enough power, then get a bigger power supply. If you're worried about power consumption overall, once the bed is heated, consumption goes way down (as @r_ahlskog stated in their answer). </p>\n"}, {'answer_id': 10688, 'author': 'user77232', 'author_id': 12857, 'author_profile': 'https://3dprinting.stackexchange.com/users/12857', 'pm_score': 2, 'selected': False, 'text': "<p>PETG requires a heated bed otherwise it will shrink, detach from the platform and begin curling at the edges. </p>\n\n<p>PLA, however in some situations does not require a heated build platform. It depends on the build surface. Some surfaces need to be hot to work, and some do not. Keeping it on helps stop the part from cooling too quickly as well. However with the correct first layer height, this tends to be less of an issue. </p>\n\n<p>I've had PLA parts stick so well to a PVA coated glass bed, that picking it up also lifted the printer. Once the bed cools on PET-G however, it practically detaches from the bed itself.</p>\n"}, {'answer_id': 10734, 'author': 'flounder', 'author_id': 10900, 'author_profile': 'https://3dprinting.stackexchange.com/users/10900', 'pm_score': 2, 'selected': False, 'text': '<p>For long prints, if turning off bed heating saves  money, throwing out the filament from a detached print costs you more.  The risk to gain ratio is very skewed.  The “savings” in turning off the bed are considerably negative, and, as pointed out, the risk of losing the print is increased.</p>\n'}, {'answer_id': 14110, 'author': 'Guz', 'author_id': 21964, 'author_profile': 'https://3dprinting.stackexchange.com/users/21964', 'pm_score': 0, 'selected': False, 'text': "<p>A way to save energy would be use a pretty tight enclosure around the printer, I think a pretty thin layer of insulation would be enough to reduce power usage by a large factor. I've not build one myself yet but there seems to be so many benefits.</p>\n"}]
['https://3dprinting.stackexchange.com/questions/10683', 'https://3dprinting.stackexchange.com', 'https://3dprinting.stackexchange.com/users/16962/']