Wont reach Nozzle Temp

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RocketMagnet
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Wont reach Nozzle Temp

Postby RocketMagnet » Fri Feb 13, 2015 6:46 pm

Been playing with Cura in Repetier and think it's really good generally Vs Slicer for various prints (though not everything).

Anyway I wasn't keen on how it controlled on startup and shutdown as it was different to Slicer and what I was used to.
so I modified it to be the same as Slicer (cut out that pointless agonising crawl to 15mm, prefer the nozzle at height with a warning its starting.. if it could heat simultaneously then ok but not sequential).. however it wont attain nozzle temp.. it keeps cutting the heater about 1 degree below target so wont reach and im having to manually set it to 1 degree above target then starting the print to get it to start.

Clearly it's trying to prevent overshoot but it's being too aggressive.. any ideas how to tune it better or what G code I need to replace
{IF_EXT0}M109 T0 S{TEMP0}
with?

Earthbound
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Re: Wont reach Nozzle Temp

Postby Earthbound » Sat Feb 14, 2015 6:56 am

Could it be that in using Cura, you've enabled the layer fan and it is cooling the nozzle?
"Trust no quote from the Internet." - Abraham Lincoln

RocketMagnet
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Re: Wont reach Nozzle Temp

Postby RocketMagnet » Sat Feb 14, 2015 7:24 pm

No its cutting the power to the nozzle as can be seen below as I've got the UI modded to display % Power to the Bed and Nozzle
and incidentally Layer Fan %age which is Cf @ 0% btw se below:

2015-02-15 00.00.54.jpg
Cutting Nozzle power prior to setpoint

NozzleTemp.png
TempTrace

Anyway as can be see above its cutting it to Zero at ~227 with a target of 230 so never gets there.. if I manually set it to 230 it gets there ok.

So yeah it's a slicing software issue, probably the start-up G Code is at fault... this bit IMO ({IF_EXT0}M109 T0 S{TEMP0}).. btw I'm using repetier host and with Slicer it works fine.. so it's a Cura specific issue. Maybe it's

RocketMagnet
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Re: Wont reach Nozzle Temp

Postby RocketMagnet » Sun Feb 15, 2015 5:43 am

OK managed to find the problem... it is due to the start G Code and it seems to be down to the fundamental difference between M104 & M109 commands.
Thought I'd post this in case someone else has the same issue..

M109 Temperature[S] Set extruder Temperature (waits till reached)
M104 Temperature[S] Set extruder temperature (not waiting)
https://thingiverse-production.s3.amazo ... tSheet.pdf

So the G-Code does the two commands in sequence

{IF_EXT0}M104 T0 S{TEMP0}
.
.
{IF_EXT0}M109 T0 S{TEMP0}

And it's definitely hanging on the M104 step of the code, I'm not 100% sure why but either way I can't see what the point of the M104 step is... why have a step heating to 230 (no waiting) followed by a step heat to 230 (wait until reached).. makes no sense to me but must be accounting for some scenario I can't think of..

Anyway commenting out the M104 command fixes the problem... below is my start G-code with the slow crawl to 15mm for the hot end commented out along with the M104 step and I've stolen the warning beeps from the Slicer G Code..

; Default start code
G28 ; Home extruder
;G1 Z15 F{Z_TRAVEL_SPEED}
M107 ; Turn off fan
G90 ; Absolute positioning
M82 ; Extruder in absolute mode
{IF_BED}M190 S{BED}
; Activate all used extruder
;{IF_EXT0}M104 T0 S{TEMP0}
G92 E0 ; Reset extruder position
; Wait for all used extruders to reach temperature
{IF_EXT0}M109 T0 S{TEMP0}
; BEGINNING OF HEAD MOVEMENT WARNING TONES
M120 S4 P10
G4 P40
M120 S4 P10
G4 P40
M120 S4 P10
G4 P40
M120 S4 P10
G4 P40
M120 S4 P10
G4 P40
M117 KEEP HANDS AWAY
G4 S3
; END OF HEAD WARNING TONES

JFettig
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Re: Wont reach Nozzle Temp

Postby JFettig » Sun Feb 15, 2015 9:00 am

Its your pid auto tuning that is causing it to cut power, I have manually adjusted mine for one of my extruders.

Polygonhell
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Re: Wont reach Nozzle Temp

Postby Polygonhell » Sun Feb 15, 2015 11:36 am

Agreed this is what you get if I or D are too far out of whack.
Sometimes autotune comes up with unusable values and you are reduced to manually tweaking the PID settings.

RocketMagnet
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Re: Wont reach Nozzle Temp

Postby RocketMagnet » Sun Feb 15, 2015 12:04 pm

yeah its the PID tune... works ok with slicer tho but not Cura..

RocketMagnet
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Re: Wont reach Nozzle Temp

Postby RocketMagnet » Wed Feb 18, 2015 5:30 pm

Finally got round to doing this using MC Autotune and it did fix the issue somewhat. Not sure but there was a wide variance in each P I & D individual values over the 3 data sets
Is this normal or should they be +/- an acceptable variance?
PID Values.png
PID Values
PID Values.png (5.75 KiB) Viewed 1769 times


Presumably my original values already in the machine were set at 200°C during SeeMeCNC build? .. As I almost exclusively use ABS I performed mine at 230.

Really odd but it's been fine for several months. Should I be concerned that something is going faulty and I'm compensating for it or is drift normal?

thegeewz
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Re: Wont reach Nozzle Temp

Postby thegeewz » Fri Jun 24, 2016 6:27 pm

I've just recently started playing with cura, and running into the same issue. I'm short 2-3 degrees, but only with cura.

Whats the difference between MC autotune and PID auto tune?

MC=mattercontrol?

My printer eventually gets lucky and starts, but the extra half hour is annoying as hell. I like the brim, and cura in mattercontrol throws the hot end into random space when I try to slice with it.


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