Safely heating up bed and extruder(s) simultaneously

[ajg 0]

Hello there,

 

Because heating up the bed takes a while, I'd like to accomplish the following:

 

1. (Non-blocking) heat up bed to bed temp
2. (Non-blocking) heat up T0...Tn to standby temp(s)
3. (Blocking) Heat up bed to bed temp
4. (Blocking) Heat up T0 to print temp
5. ...

 

I have a rough sense of how to manually change the start gcode to do it, but I wanted to check whether it's already possible some other way (e.g. via the UI) or otherwise what the optimal gcode sequence is—for instance, I'm not sure how M105 factors into things.

 

I'm also wondering whether there'd be any unintended side-effects or if it's known to be a bad idea, period. (Note that in my case the printer doesn't support auto-leveling, which could presumably be affected by changing the order/asynchrony of temperature changes; and at any rate, I don't see any G29s emitted anywhere.)

 

Thank you!

 

[Smithy 1,145]

2 hours ago, ajg said:

I'm also wondering whether there'd be any unintended side-effects or if it's known to be a bad idea

 

Depending on your power supply it could be a bad idea. Heating up the bed consumes a lot of power which is near the capacity of a usual power supply. So be carful when doing both at the same time!

[ajg 0]

29 minutes ago, Smithy said:

 

Depending on your power supply it could be a bad idea. Heating up the bed consumes a lot of power which is near the capacity of a usual power supply. So be carful when doing both at the same time!

 

Ah, good point.

 

I've little idea how much heating up either part draws... nor how much the printer can supply, for that matter. Anyone know or care to estimate what those wattages are for a stock BIBO2 Touch? (Per one source its power is 100W; not sure how reliable that data is.)

 

Thanks.

[Smithy 1,145]

I would say it is not worth the risk, to probably burn down your printer or power supply. The bed takes the longest time to heat up, the nozzle should be at temperature after a few seconds or half a minute or so. That said, you will not save much time when doing it in parallel. 

[ajg 0]

1 hour ago, Smithy said:

That said, you will not save much time when doing it in parallel. 

I took a few times down and it looks like, on their own from "cold," it usually takes a little over two minutes for the bed to heat up to 60C and a little under two minutes for one extruder to reach ~210C. So in my case I do think there's opportunity for at least one minute of savings if the heating could be parallelized safely to some extent.

 

1 hour ago, Smithy said:

I would say it is not worth the risk, to probably burn down your printer or power supply. The bed takes the longest time to heat up, the nozzle should be at temperature after a few seconds or half a minute or so.

 

I see. Another idea that I've entertained is preheating the bed on startup to something commonly used like 60C (maybe combined with an automatic cool down after several minutes if a print hasn't begun.) However,  I can't imagine there's a way to do this without custom firmware.

 

Anyway, thanks again.

 

 

 

 

[geert_2 558]

In addition to the load of the supply:

 

If the heated bed takes a very long time to heat up, for example for materials that need a higher bed temperature like ABS, a side effect of heating both nozzle and bed together might be that the molten filament in the nozzle gets burnt and clogs it up by the time the bed is ready.

 

So, first bring the bed up to a stable temp, and only then start heating the nozzle to prevent product degradation and clogs. Especially with products where the melting temp and burning- or decomposition temp are very close together.

 

[eldrick 65]

For several years I have heated the bed up to the target temp, while heating the extruder to about 50C less than its target. This avoids the possibility of overheating the material in the nozzle, and doesn't heat both at the same time for nearly as long.

I've never had any sort of issue from doing so. I usually do this manually, rather than in starting gcode.

[mikers 0]

On 9/27/2019 at 5:41 AM, eldrick said:

For several years I have heated the bed up to the target temp, while heating the extruder to about 50C less than its target.

 

Is there a way to automate this in the settings?  I have seen messages about doing it manually by editing the start code somewhere, but would like to make it standard.