[feature] Adaptive / Feedforward Temperature setpoint

Triet

@timschneider said in [feature] Adaptive / Feedforward Temperature setpoint:

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This was a test I spontaneously decided to do without planning, but it turned out unsuitable for the purpose of temperature modulation. The maximum flow rate of 5.44 mm3/s (using a 1.75 mm filament) happened very shortly and was not representative at all. I did notice the jump though - causing a heater fault at my first try.

I also use a 60 W heater, in a copper block (E3D style) and an original CHT nozzle. It can achieve a 25C increase faster that one would think, but certainly not fast enough if the model consist of parts with disparate flow rates in succession. And that is exactly the test case I am printing right now:

As you can recognize here:

The temperature is set at 195C but settles at around 199C +/-2C, it can't follow as you say. The range would be much wider if it could. But there are some layers with predominantly high flow, I am waiting to see how the temperature behaves then (I am staring at the display).

Based on my experience using the postprocessing script mentioned above, the maximum temperature lag was about 5C, in most cases only 3C - but that script uses a different method, where the flow rate is adapted (smoothed) to match the predicted temperature, very clever in my opinion. The temperature/flow rate relationship is defined there by entering three points of desired temperature at the given flow rates, quite easy. I could envision that a similar method is implemented in the firmware. But even this T-Parameter is a thing as it is now. I have learned to appreciate the value of temperature control and am quite excited about it.

More tests following.

Triet

@timschneider That model (I would call it "the "mother of hinges"), went well - all hinges were moving free without play (after forcingly "unfreezing" them the first time). I can infer then than the temperature variation does not pose a danger in maintaining correct dimensions, in this case at least.

Now I am choosing a more representative test model with an ample variation of flow rate, which at the same time allows us to assess artifacts, without being excessive large or long to print.

This JUN - the Jungle Queen (visual benchy) has a plethora of details and is not too small.

Results:
Printing with at 195 C, 0.2 mm layerheight, (0.4 mm nozzle), solid infill with 0.6 mm layer width, and sparse infill speed set at 300 mm/sec (but not reached) and still using M309 P0 S0.06 T10 A40, Orca Slicer was showing a flow rate up to 29 mm3/s, but that is not true. The real maximum is about 20 mm3/s, enough of a range. Extrusion rate smoothing was set to 90 mm3/s to avoid abrupt transitions.

The temperature occassionally reached >240 C in the high flow areas. In very slow areas, it was decreased (!) down to 190 C. Most of the time, is was about 200C.

The print shows very crisp details, reminding me of previous cases using the postprocessing script. This is obviously the result of printing the small details with a suiting lower temperature.

Despite some suboptimal slicer settings (happens when printing in a hurry), the print went well and it looks better than in the picture.

Remarks:
I noticed that right at the begin of the print the temperature is higher than it should be (although I disabled this temperature modulation feature for the first layer), but immediately begins to fall as the print of the 1st layer progresses. My suspicion is that the firmware looks at the flow of the movements in the print queue in advance, but ignoring the command disabling the feature. But the command it is there:

and when it is processed, the temperature fails again to the nominal 195C. It looks like a slip to me.

Furthermore, I still got heater faults (even after releasing the check conditions), but strangely, this happened at a moment where the temperature was quite stable after having significantly changed before. So it looks to me like the firmware notes a temperature deviation, but does not update that deviation timely as the temperature has changed and stabilized. Perhaps that part of the firmware should be revised.

This time, a decrease in temperature compared to the nominally set print temperature (195 C in this case) took place at some point. So I withdraw the objection I made before, although I don't quite understand how this is controlled in detail. I assume that the T parameter defines a slope determined by changes of temperature in relation to changes in flow, but where we are in that characteristic curve, I don't know.

Summarizing, I am very pleased with this enhancement. I still stand on my prediction that this feature will stay extremely underrated. I recommend to try it out.

Triet

@timschneider In case you are interested, this video offers insight to flow modulated temperature control:

Variable Temperature 3D Printing – The FUTURE of 3D Printing?