Leveling Procedure and Print Core Heating on S5 7.0.1

[arj3090 2]

I was watching the printer to figure out why it takes so long to start a print and one thing stands out that wastes time. Just before leveling, the print core is brought up to temperature. Once the leveling starts, it seems the heat is turned off. With the nozzle repeatedly touching the glass, it cools the nozzle back down. This then requires the printer to wait again for the print core to heat up before starting the print. Why couldn't it continue to keep the print core up to temperature during leveling and save the time it takes to re-heat a second time?

[Smithy 1,141]

The reason why the heater is turned off before leveling starts is that there are many interferences from the heater that could cause a leveling error. 

[arj3090 2]

Would it be better to not heat the print core before leveling? If the core is at temperature on the first touch off point and cool for the last, I would have to guess there is a small amount of thermal expansion/contraction creating some inaccuracy in height measurement.

[Smithy 1,141]

Yes there could be a small difference between the beginning and the end, but not so much as when you level with the cold nozzle and print with the hot one. And additionally a hot print core is needed to soften any filament residues on the tip of the nozzle.

 

Heating up a print core is quite fast, the time you notice after leveling and before starting the print is the print bed which takes much longer to heat up again and which is also turned off during leveling to avoid electrical interferences. 

[arj3090 2]

Softening the plastic on the tip makes sense. I do see a small blob stick to the glass at the start of leveling.

[arj3090 2]

On 1/16/2022 at 1:41 PM, Smithy said:

Yes there could be a small difference between the beginning and the end, but not so much as when you level with the cold nozzle and print with the hot one.

I'm revisiting this and still think the heat should not be turned off during the leveling process. Two reasons as to why. The first is the difference in nozzle temperature between points makes it less accurate. The other reason is the time the printer needs to wait for the nozzle to heat back up after the leveling process before it starts to actually print.

[Smithy 1,141]

As far as I know it is needed to turn off heating to avoid interferences coming from heater itself. The capacitive sensor is very sensitive to such things.

[FixMaestro 0]

I would like to ask for a feature consideration.

 

As there are problems when using materials (PEI, etc) on the printer bed that can be damaged by heat during the auto-leveling stage, how about providing a preference setting where the maximum hot-head temperature during auto-leveling can be entered.

 

One way to minimize the damage caused during auto-leveling is to allow the hot-head to be heated to the required temperature and then move the head to an extreme edge to wipe the hot-head clean. Then the setting preference for a 'Maximum Auto-Leveling Temperature' will cool the head down to a safe level to avoid further damage to the build surface during auto-leveling. After the leveling, raise the head temperature back to the normal print level. Maybe even have a preference setting for a 'Cleaning location' on the build plate.

 

By careful setting of the maximum temperature, the plastic on the head can be still allow the head to fully contact the build plate, but won't drip either. So you don't need the higher temperature that causes the build plate damage.

 

I agree with the 'cold-head' approach not being optimal, but maybe this one is a good compromise to avoid build plate damage?