When i turn off the buildplate the printer changes the extrusion rate ? Or what ? Underpowered ? Maybe a Voltage problem ? I have constant extruder overload errors and going forth and back with customer support gained nothing but wikipedia links and “we cant do something sorry its planned for the future but we cant tell you more” kind of answers. I kindly requested to turn off the extruder overload function or atleast give me a checkbox for " Yes im shure what im doing please dont stop my print for some kind of firmware threshold " But maybe this is more a Supply Voltage or Current problem maybe on the toolhead or MC ? How can the Heatbed when its already on temperature influence anything about how the printer extrudes that what im trying to understand, anyone else seen this on theyr machine ? I already made very shure the extruder does not get overloaded even tryed topfeeding without PTFE resistance ect. extruder and channels are as clean as they can be machine is maybe 50 hours in.
I did not test if the heatbed cycling on and off during the print to keep the bed temperature stable cause any artefacts, i just saw this right now but maybe this also causes artefacts ? I have to test further … maybe someone want to jump on to this and test that on theyr machine just a first layer, it was PETG on 255° and 70° bed.
To me imho the heatbed off extrusion looked way better than with the heatbed on i dont know if it comes over that way in the video.
I’m going to try some simple experiments here to replicate it with more standard/reproducible tests.
Maybe you can run one for me, could you create a cylinder primative, 3x (or whatever) it in height, print it in vase mode, then when it gets up an inch or so do your bed power toggle? Your current demo is a little hard to repro and is mixing in issues like the actual bed temperature (I know, very unlikely, that would be like instantaneous heating, but still) and z change due to heating.
And does it only happen with the left nozzle or both?
Youre right, i came up with a 3mf with custom gcode that turns the bed off and on in different way also heat to 100° ( wont reach ) and turn down to 70° to see the cooling cycle at the end there is a big section 0° vs 70° at the end. For now i only tested left nozzle, gonna test right nozzle now.
For those who wonder, who would turn off or on the heating.
Its sometimes better to exagregate ( right word ? ) something to see big errors to find where small errors lie, if its that hard visually it def. would cause smaller artefacts while the bed is cycling 69-70-72-68 ect. since i think this transistor controlled bed heating has some fluctuations that cause other errors in the machine atleast what i would guess when this happens on all machines hey, im out of ideas and fine with that guess my lemon will remain lemon then.
I have 2 other P1S printing on the same circuit, they show no visible artefacts while i turn on and off the bed on the H2D, i also concluded maybe its the circuit voltage being run down by the bed …
It would be great if you posted your G-code so someone else could check it. It might be a problem with just one printer, not all of them. Unfortunately, I can’t try it yet. Mine is still on its way.
I’m on my way out the door, so I just resliced your file for the filament I had in the unit and verified the custom g-code changes were still there.
The circuit my H2D is on has some LED lights that flicker when the bed heating goes on, so I started watching for the flicker and I see the artifacts exactly correlating with the flickering and bed temperature changes. I pulled it off the printer and it seems to match your pattern exactly.
I can’t play with this more today, but this needs some more eyes on it. If other people could test that would be great.
I don’t have one, but if I understand correctly the heatbed power draw (not temperature, draw) is directly affecting the extrusion rate? Do you know if the hall backpressure feedback is continuous or is it just used for initial calibration? If it is continuous I might look there also for an explanation. If the behavior also repros on an H2C left nozzle only than might be an indication of the fault being in the hall feedback. The features in the picture are so sharp it seems unlikely to be anything thermal related like the hotend temperature changing, but that is possible too.
Hello, i would guess that any temperature change ( Heatbed, Nozzle ) are too slow to produce such a effect since in my video its instantatneous on the next gcode line as it seems. The sliced file should be the same gcode for any machine im using the latest stable release of BS
Edit: Im not familiar with how they measure the extrusion feedback via hall or via the motor feedback e.g current drawn ( wich would be awesome since i could alter this measured value with soldering to avoid extruder motor overload shutting down my prints haha maybe ? ) Nevermind i just found out what Chip they use to measure the extrusion force and its a dedicated chip for motor control and load measurement as it seems its using some kind of secret sauce prediction algorythms for that. “SpinTrol SPC2168FPE”
In detail, the errors look like its a different height ( squish ? ) or simply the extruder making thinner lines or thicker lines depending of if you set it to 0 or 70 i would rule out x/y motions imho maybe even Z because i cant wrap my head around why the steppers should step at fluctuations but hey im not that deep knowledgewise
So temporary conclusion for me is the power fluctuation from the heatbed is high enough to actually cause defects, i think this will remain as i dont see either me or bambu fixing this in any form of future and also i dont really test if the cycling causes defects i just wanted to make shure its not only my machine for my sanity.
extruder rate variation
hotend temperature variation (seems unlikely, effect is almost instant)
bed changing z position (seems unlikely, would produce a pulse, not a band)
x/y speed change
Here’s a chart of your bed temperature changes so you can match up the lines with a micrometer
mm
#
C
0.8
5
0
1.6
10
70
2.4
15
0
3.2
20
70
4
25
0
6.4
40
70
8
50
0
11.2
70
70
12.8
80
100
15.2
95
70
19.2
120
0
(note I didn’t adjust for your initial layer height of .2, but the error is small)
I think you are mistaken about having to live with it, this is a serious problem, no one is going to consider this behavior acceptable.
I’m guessing you are on 240V? I’m on 120.
I’m going to run some more tests, watch the hotend temperature, etc.
Yes, 240V 16A breaker, 5m to Distribution box ( Next wall outside the room )
I have no device here that makes any visible changes to the power fluctuating, Vacuum for example its a pretty stable power here also 3Phase available in the house
I want to print a test where i print on p1s and the h2d the same part but on one of the p1s without the gcode just to see if it influences other printer to verify if its actually the power fluctuation shared on the whole line of just this machine now but i have prints on every printer for atleast another 10h.
Sadly i have no powermeter just tasmota plugs with uncalibrated power readings i guess a spike would be visible but no values would be right.
I’m thinking it’s power related, watching the meter on mine there appear to be several levels of heat, 2 or more. A high and maybe 1 or 2 mid powers. Trying to figure out if I have the gear here at home to measure and graph it at the layer resolution. I’ve got current probes for my scope, but that would need a lot of memory to capture to make sense of.
I just plugged in the tasmota, during startup it pulls about 2,1kw then it cycles between 80w and 400w while doing bedlevel ect. ( Those numbers can vary heavily, i just did SetVoltage240 for now so its all calculated on this wrong voltage )
Printing without heatbed 100w
Printing with the bed turning on and being on 400w
Heating to the 100° part also 400w
There are no crazy spikes, very predictable but yet uncalibrated results
Grid is constant all the time, sadly im too lazy to pull up fancy grafana sheets so this problem is most likely in the machine power supply or TH-board power supply itself and not the outlet / house wiring. Atleast, if the spikes are not faster than what my statistic can pull from the plug wich could be a very likely case
Yes this bed has to have a fast 230v preheat mode and then a “cycling mode” wich pulls way less power wich is understandable a good technique.
I would expect peaks much higher than 400W, I’m seeing 1200W peaks at least. I’ve ordered a plug with 1-second resolution to test with.
From looking at the bands and watching the heater cycle it is less clear that it is directly power related vs temperature. The 70 and 100 bands appear thinner, but uniformly so, if it were power related I’d expect them to change as soon as the bed reached the target temperature. Also when the temperature is set to 0 I see a rebound bulge at those points.
This is so easily reproducible it should be filed as a bug, but I’d like to simplify your test a bit for the repro. If you’d like to file it yourself that’s fine too, otherwise I’d be happy to.
I’ve got a H2C to test it on also but don’t have it set up yet.
For anyone coming into this thread, this must seem a bit esoteric and confusing, as this is something you’d never do.
In a nutshell, the assertion is that things printed on a cryogrip plate vs a PEI plate should look identical. There should be zero coupling between the bed temperature and extrusion width/rate/temperature. Not “a very small amount”, the coupling should be zero as these are independent systems in the printer.
What we are doing with these experiments is the engineering equivalent of using a magnifying glass to amplify and exaggerate any coupling so that it is easily visible. There are going to be some problems as changing the bed temperature can cause the bed to expand into Z, but we are trying to isolate those effects from any coupling coming from other sources such as the power supplies.
Ran a simpler test, 0 at 1/3 up and 55 at 2/3s. Layer heigh of .8 seems to exaggerate the effect at least in this test. No surface change I can see going from 55>0 (about 20 mins in) but a discontinuity going from 0>55 at 30mins in. It appears the layers are spread out, not squished, so the opposite of what I’d expect from thermal expansion in the bed pushing it up.
Towards the right is up, left side is 0 and right is 55.
I’ll need to take it into the lab Monday for a closer look at the topography, but looking at it with my microscope at home those big layers are single, unsquished layers and they are sunk down in the surface slightly, not bulging out. Right after (maybe 10 layers) there does seem to be an opposite bulge out.
I moved it here and the pattern is fainter, maybe 2 or 3 lines, and it appears to be in the opposite direction (squish), and the 55>0 transition also has faint line, also just a line or two but it is in the stretch direction. Both lines aren’t very strong, but they are quite sharp.
So this is suggesting something more mechanical. Note in the 55>0 direction the plate cools quite slowly, maybe 1/3C per second, what is magical about 55>53 that makes a sharp feature?
Here’s a crazy idea, sorry I don’t have one to test. What if for the 1/2 power modes they don’t pwm but simply use half-wave rectification. Then for half power, the heater becomes a magnet and pulls down on the buildplate more (or less). It would be crazy bad for PFC and maybe even illegal, I said it was crazy but would be fun to check. Does anyone know if it is PID? X1 was bang-bang.
I’m experiencing the same issue on my P2S. I’ll leave the link below for reference.
When the bed temperature stays constant, I already get under-extrusion with ABS. If I then increase the bed temperature from 90°C to 110°C, the situation gets even worse. However, when I lower the bed temperature back from 110°C to 90°C, all extrusion becomes normal again while the bed heater is off and cooling down.
Have you been able to find a solution? What is the current status on your side?
