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Heating during z-calibration ok?  

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Høgge
(@hogge)
Active Member
Heating during z-calibration ok?

To save a little time I changed the g-code to start heating before the "G80 ; mesh bed leveling" starts, but seems like results are a bit off?

Does the heating of extruder and bed disturb the pinda probe measurements (electrical noise) or is it because the rising temperature does (needs to be stable to measure) or should it not affect the Z measurements at all?

kr
Morten

Posted : 29/06/2017 11:47 am
Knickohr
(@knickohr)
Moderator
Re: Heating during z-calibration ok?

My comment : No !

While heating the bed and nozzle the pinda probe measuring is affected.

Thomas

Posted : 29/06/2017 11:50 am
Høgge
(@hogge)
Active Member
Topic starter answered:
Re: Heating during z-calibration ok?

Thanks. Sounds plausible. Is it "backed" by any solid evidence?

Posted : 29/06/2017 12:08 pm
PJR
 PJR
(@pjr)
Moderator
Re: Heating during z-calibration ok?

You must heat the bed before the 9-point calibration (G80) ; the nozzle is to a large extent irrelevant.

If you don't heat the bed to print temps then the calibration will be incorrect (variable). You need to ensure the probe is at least 100mm above the bed while heating the bed.

However, I heat the nozzle to 170 degrees while the bed is heating and then to print temp during the G80 just to save time.

If you look at older posts, you will find plenty of evidence.

Peter

Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…

Posted : 29/06/2017 12:29 pm
Høgge
(@hogge)
Active Member
Topic starter answered:
Re: Heating during z-calibration ok?

But then the G-code for the printer should do that and also move the probe up? And should you then turn heating off during calibration?

The temperature calibration of the probe - shouldn't that make it possible for the printer to compensate for bed temperature?

So you should use the preheat commands on the printer first then?

Posted : 29/06/2017 12:39 pm
Høgge
(@hogge)
Active Member
Topic starter answered:
Re: Heating during z-calibration ok?

So to incorporate what I found I will start prints like this (see gcode below)

1) Preheat nozzle to 170 and bed to printing temperature
2) Home and wait for temperatures to stabilize
3) Turn off bed and extruder heat
4) Do bed leveling
5) Re-set extruder and bed temperatures and print when reached

Makes sense?

As this:

G21 ; set units to millimeters
G90 ; use absolute positioning
M82 ; absolute extrusion mode
M104 S170 ; set extruder temp to 170 preheat MHP
M140 S{material_bed_temperature} ; set bed temp MHP
G28 W ; home all without mesh bed level
M190 S{material_bed_temperature} ; wait for bed temp MHP
M109 S170 ; wait for extruder temp MHP
M104 S0 ; turn off extruder during bed leveling
M140 S0 ; turn off heatbed during bed leveling
G80 ; mesh bed leveling
M104 S{material_print_temperature} ; set extruder temp
M140 S{material_bed_temperature} ; set bed temp
M190 S{material_bed_temperature} ; wait for bed temp
M109 S{material_print_temperature} ; wait for extruder temp
G92 E0.0 ; reset extruder distance position
G1 Y-3.0 F1000.0 ; go outside print area
G1 X60.0 E9.0 F1000.0 ; intro line
G1 X100.0 E21.5 F1000.0 ; intro line
G92 E0.0 ; reset extruder distance position

Posted : 29/06/2017 1:12 pm
PJR
 PJR
(@pjr)
Moderator
Re: Heating during z-calibration ok?

You certainly don't need this:

M104 S0 ; turn off extruder during bed leveling
M140 S0 ; turn off heatbed during bed leveling

I repeat, the heated bed must be at printing temperature during the 9-point calibration.

The built-in probe temp calibration is OK, but it does not take into account changes in ambient temperature. Therefore it's not something I use.

Peter

Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…

Posted : 29/06/2017 1:16 pm
Høgge
(@hogge)
Active Member
Topic starter answered:
Re: Heating during z-calibration ok?

You certainly don't need this:

M104 S0 ; turn off extruder during bed leveling
M140 S0 ; turn off heatbed during bed leveling
I repeat, the heated bed must be at printing temperature during the 9-point calibration.
....

Well if the pulses to the bed and extruder disturbs the measurements then I DO have to turn of heating during bed leveling.

kr
Morten

Posted : 29/06/2017 11:35 pm
PJR
 PJR
(@pjr)
Moderator
Re: Heating during z-calibration ok?

Well if the pulses to the bed and extruder disturbs the measurements

Why would that happen? The probe (and MCU etc) is powered via a buck regulator so the 5 volt rail is simply not likely to be affected by the heaters. Especially so when the PSU has at least 25% overhead.

Peter

Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…

Posted : 29/06/2017 11:44 pm
felix.f
(@felix-f)
New Member
Re: Heating during z-calibration ok?

Do we have a good start and end g-code established yet?

I'm having troubles with getting consistent results with bed levelling, printing with ABS/HIPS

Posted : 03/07/2017 2:20 pm
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