Posts made by jschall

@phaedrux so, accelerometer required? No way to tune without? Where do I buy one compatible with my duet 2 wifi?

Things improved greatly with input shaping disabled. How do I properly tune input shaping? I don't have an accelerometer.

Input shaping was actually enabled (Input shaping 'zvd' at 50.0Hz damping factor 0.10, min. acceleration 10.0, impulses 0.334 0.822 with durations (ms) 10.05 10.05) - I am re-running the test.

Physical setup: E3D ToolChanger with direct Hemera extruder, PolyMax PC @ 285C.

RRF 3.4.0, input shaping and nonlinear extrusion off (should be, not configured - will check)

I am tuning pressure advance using the python script - that part is working - the print is changing as the Z axis gets higher - for example, when pressure advance is too low, there are the expected holes where the nozzle is accelerating. The pictured sample is from 0.0 to 0.2. I've gone 0.0 to 1.0, and it starts to totally fail just beyond 0.2.

However, on every acceleration and deceleration, there is a thin spot regardless of the pressure advance setting. What's weird is that it is on both sides - I'd expect a thin spot on accel and a thick spot on decel with PA too low, and the opposite with PA too high. I can't think of anything that would cause this. I tried tightening belts as well - they're tightened up to 8lbs.

What is interesting is that this doesn't happen nearly as much with my bowden extruders - it is like there's some bug or issue or missing tuning feature in RRF that is being covered up by the slow response of the bowden extruders.

Any suggestions?

@deckingman said in RRF 2.03 pressure advance causes 20% overextrusion:

One last contentious comment is that as mass increases, the resonant frequency decreases. Is it purely coincidence that I never get "ringing" or "ghosting" when using my heavy hot ends but people with lightweight hot ends offen have those problems?

What is your jerk set to?

@deckingman So why the hell is bowden so popular? It isn't simpler, it isn't cheaper, it isn't better.

@deckingman said in RRF 2.03 pressure advance causes 20% overextrusion:

If a Nema 17 is perfectly capable of attaining printing speeds of >300mm/sec with a 2Kg mass, then it is implicit that it must have sufficient torque to accelerate that mass up to that speed in less than half the axis length.

So you are actually getting achieved speeds of 300 mm/s with a NEMA 17 pushing around 2kg?

Still, acceleration matters a lot. It dominates when printing smaller parts. What kind of accelerations are you achieving?

@jschall Can those servos meet the speed/acceleration achieved by a stepper? Not saying they can't I just have no idea of what they can do.

Yes. Regardless, not suggesting the use of those specific servos.

@Veti said in RRF 2.03 pressure advance causes 20% overextrusion:

i think the biggest problem is that they cant do a full revolution

That's just because of mechanical stops in the gearbox to prevent the potentiometer from having problems. In an extruder application, you'd have a somewhat different configuration. Remember, this is just more of an example of how cheap, small and light an integrated servo motor could be, not suggesting that these are options for our application without significant modification.

@JRDM said in RRF 2.03 pressure advance causes 20% overextrusion:

Hobby servos are very limited on what they can do for that kind of use because the type of input doesn’t allow for the level of control needed.

@JRDM said in RRF 2.03 pressure advance causes 20% overextrusion:

Hobby servos also use deep multistage gearboxes, which induce excessive backlash.

I'm not talking about using hobby servos. I'm using hobby servos as an example in a first-principles argument that steppers are dumb in extruders. Backlash not important for extruder. Just means you need very slightly more retraction to take up the backlash.

@deckingman said in RRF 2.03 pressure advance causes 20% overextrusion:

So if carriage mass isn't a limiting factor, then why reduce it? In fact I have demonstrated this by printing at up to 300mm/ sec with a moving carriage mass of around 2Kgs driven by modest NEMA 17s. I'll make a other contentious statement that adding mass reduces the resonant frequency - I don't get ringing -ever.

It's more about acceleration than speed. A NEMA 17 could accelerate a locomotive to 300 mm/s, assuming low enough friction. It'd just take longer.

@jschall said in RRF 2.03 pressure advance causes 20% overextrusion:

@Veti

Yeah totally agree.

Bowden is fking stupid. The whole premise of bowden is to REMOVE a motor that needs to output LESS THAN 1W OF MECHANICAL POWER in order to SAVE MASS on something that weighs in at like 500 grams. Hey, here's an idea: how about instead of that, we stop using half-pound 1970s-era stepper motors?

Here's a servo that outputs more torque than the geared titan extruder. It costs a whopping $10 - which is cheaper than the stepper. It weighs 58g vs 280g for the stepper. It includes the gears, which add not-insignificant mass as well. I'm not trying to say you can buy that servo and stick it on an extruder and it will work unmodified - it won't. I'm pointing out from a first principles point of view that you can cut out 80% of the mass of the extruder, without bowden, and it doesn't have to be expensive.

https://hobbyking.com/en_us/hobbykingtm-high-torque-servo-mg-bb-w-proof-12-8kg-0-22sec-58g.html?queryID=76697295b4ca978c54e06a560255a667&objectID=47699&indexName=hbk_live_magento_en_us_products_hbk_price_stock_2_group_0_desc

@Phaedrux said in RRF 2.03 pressure advance causes 20% overextrusion:

Doesn't it seem silly to replace a one of the walls with a travel move though? It's still taking the time to move around the entire perimeter it's just not extruding anything.

Not really, because the only case where it isn't extruding anything is the case where the wall thickness is exactly equal to the line thickness. But yeah, could be optimized.

What slicer does the absolute best with thin walls? I bought Simplify3D and was horribly disappointed. Cura so far seems to do the best job overall.

@Veti

Yeah totally agree.

Bowden is fking stupid. The whole premise of bowden is to REMOVE a motor that needs to output LESS THAN 1W OF MECHANICAL POWER in order to SAVE MASS on something that weighs in at like 500 grams. Hey, here's an idea: how about instead of that, we stop using half-pound 1970s-era stepper motors?

@Phaedrux Cura has something called "compensate flow" and I think it reduces the flow on one of the two walls so that the total extrusion volume is correct for the wall thickness.

@Phaedrux Really? Cura seems to do way way better than PrusaSlicer when slicing things with thin walls. Also it has support for coasting which is super important on my ender3 v2s that don't frigging work with linear advance...

I just hate Cura's interface. Hard to be worse.

Good to see "Detect thin walls" still sucks just as much as ever.

@bot
Got it running. Doesn't work in VirtualBox anyway because no opengl 2.0+ support. So, I ran it in WINE and it works fine. Extrusion amount looks about right.

@bot ah ok.
It is complaining about vcruntime140_1.dll, but I've already installed the visual c++ 2015 redistributable...

@bot What's the difference between that and the n8_precision_minus_infill_support branch?

@bot said in RRF 2.03 pressure advance causes 20% overextrusion:

However, I found the SuperSlicer (fork of PS) build instructions fantastic.

That's just identical to the PrusaSlicer build instructions.

Hmm, even a windows build would be fine. Can run it under a VM.

@bot do you think you could build the linux .appimage for that and send it to me?

@bot I tried to build PrusaSlicer before and gave up because of ridiculously huge numbers of dependencies on cutting edge versions of everything.