Why keep the bed heated after initial layer(s) with PLA (or PETG)?



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.

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).

Am I missing something? Why is anyone keeping the bed heated for an entire print?

Oliver Giesen

Posted 2019-07-25T08:46:26.333

Reputation: 295

3D printing has a lot of variables, and it may work for one setup but not for the other to switch off heating. Anecdotally it works fine for me in the summer, but not so good in the winter. Also I have some glow in the dark PLA that just doesn't want to stick very well at all.. – PlasmaHH – 2020-01-14T09:48:40.730



There are three reasons (I can think of):

  1. 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.

  2. When you're dealing with 0.1 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 given, but definitely a concern ... especially for larger or taller prints.

  3. 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.

There may be other reasons, but I believe these are very good 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).


Posted 2019-07-25T08:46:26.333

Reputation: 2 271

At the risk of getting snarky, Changing the layer height to the max possible (depending on nozzle size and aesthetics of product) reduces the total print time & thus reduces the total energy consumption. – Carl Witthoft – 2019-07-25T13:28:17.187

Another way to reduce the power consumption of the heated bed is to insulate the underside, e.g. with a cork mat and adhesive/sticky tape that will withstand the temperature. – Andrew Morton – 2019-07-25T14:13:40.223

Depending on the printer, reason 2 may be very important. I've gotten very different "bed leveling" settings depending on the temperature state of the bed. – cmm – 2019-07-25T19:50:36.150

Absolutely correct about the power to initially heat and reheat the bed being equal. However, during re heating the printer will only be adjusting the temperature a degree or so every few seconds. When the heated bed is first turned on the difference between the target temperature and the actual temperature is much larger than when re heating. Therefore, power consumption will be cut way down after the target temperature is met due to the fact that the heating element will only be activated for a short amount of time every few seconds rather than being on continuously. – Jw_electrical – 2019-11-26T03:45:12.250


PETG requires a heated bed otherwise it will shrink, detach from the platform and begin curling at the edges.

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.

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.


Posted 2019-07-25T08:46:26.333

Reputation: 2 090

3PLA doesn't require a heated bed, but if bed temp drops after the first layer, all the corners will curl up due to uneven cooling rate. You want either unheated or consistently heated. – R.. GitHub STOP HELPING ICE – 2019-07-25T23:56:27.277


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.


Posted 2019-07-25T08:46:26.333

Reputation: 141


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.

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.

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.


Posted 2019-07-25T08:46:26.333

Reputation: 274

Well, my print jobs usually run over night (or actually over several days), so I'm typically not there when a print finishes to start a new one before the bed had a chance to cool down. It's especially the multi-day, tall prints where constant bed heating feels wasteful... Apart from that you make a good point. Also, thanks for pointing out that power consumption for bed heating mainly applies to heating up, rather than maintaining heat... – Oliver Giesen – 2019-07-25T11:15:11.663

2It is incorrect to suggest that it takes more power to re-heat the bed vs. maintaining the temperature throughout the "first" print. This is basic Thermodynamics. The amount of energy per unit volume per unit temperature doesn't change. – Carl Witthoft – 2019-07-25T13:26:52.660

You are absolutely right, I should have known that. – r_ahlskog – 2019-07-25T13:41:27.743

2In my experience, watching the temperature curve with constant energy input, it is not the case that keeping the bed hot is relatively incidental. There are substantial heat losses from the hot bed, and these must be constantly overcome to maintain temperature. Keeping the bed hot only consumes energy. There is no condition where it saves energy compared to turning off the bed heater. – cmm – 2019-07-25T19:49:30.880

Lets edit out my thermodynamics violating statements, keeping a bed warm uses energy, heating it uses the amount required to to reach that equilibrium but since we don't want to wait approx infinite time we expend more over a shorter time to reach it and the optimal strategy is to heat as quickly as possible, maintain temperature and then cut heat as soon as it is not needed. Up to the point where powersupply and mosfet losses start to exceed design capacity. – r_ahlskog – 2019-07-25T21:11:10.813


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.


Posted 2019-07-25T08:46:26.333

Reputation: 1

That won't give you a large power saving, it will heat up the enclosure, also this may introduce other problems like hotend cooling and electronics cooling. – 0scar – 2020-07-20T21:59:18.670

OK, I had the impression if you want to do any serious printing you use an enclosure? The air in the enclosure will be the same temp as the bed, I guess around 50-70C, don't think that will damage the electronics. The air will not be warmer than that if you have some little ventilation, so my guess is that this will be pretty ideal conditions for printing and pretty power efficient. But this is all in theory :-) – Guz – 2020-07-21T13:27:05.173

Oh, and you say the power saving won't be large, I would say it will be proportional to the quality of the insulation. – Guz – 2020-07-21T13:30:39.093