Struggling to get PETG tuned. Pressure advance issue maybe?
rschlachter last edited by
I recently gave my Wanhao Duplicator i3 Plus an overhaul. I upgraded the board to a Duet Wifi, rewired everything, and changed to a Hemera extruder. Many would say it wasn't worth it, but I learned a lot along the way which I love. My goal is to eventually go full ReDuplicator.
I was able to dial in PLA pretty quick and easy. Even pushed the speeds up to 100mm/s with decent results. A little ringing/ghosting that high. But I am stuck on PETG. I got some pretty iffy prints with the settings I used on my previous Micro Swiss all metal hot end. The cube dimensionally is good in both PLA and PETG so I imagine my axis steppers and esteps are calibrated ok.
I know I have to tune my bridging. The fan was completely off the whole time which I think lead to the mess when the ceiling went on the Benchy although it did surprisingly almost make a full recovery.
The main issue I'm not sure how to fix are the gaps along the X axis. It happens on the bottom and top layers on the cube but seems a bit more random in the Benchy. It's like it's retracting too early on layer changes maybe? I'm keeping the retraction lower as I've heard is best on the dual gear extruders like the Hemera. I had pressure advance off for these prints, and after poking around the forums, I feel like maybe that's where I've got issues. That and maybe still acceleration and jerk issues as I'm seeing the banding on the Y side even at 45mm/s for PETG.
Cura Print Settings Layer Height: .2mm Wall/Top/Bottom Thickness: .8mm Top/Bottom Layers: 8 Infill: 20% Infill Pattern: Concentric Print Temp: 240 Build Plate: 75 Speed: 45 mm/s Retraction Distance: .5mm Retraction Speed: 30 mm/s
and my config.g
; Configuration file for Duet WiFi (firmware version 2.03) ; executed by the firmware on start-up ; ; generated by RepRapFirmware Configuration Tool v2.1.8 on Thu Mar 05 2020 15:48:10 GMT-0600 (Central Standard Time) ; General preferences G90 ; send absolute coordinates... M83 ; ...but relative extruder moves M550 P"wanhao-di3" ; set printer name ; Network M552 S1 ; enable network M586 P0 S1 ; enable HTTP M586 P1 S0 ; disable FTP M586 P2 S0 ; disable Telnet ; Drives M569 P0 S0 ; physical drive 0 goes backwards M569 P1 S0 ; physical drive 1 goes backwards M569 P2 S0 ; physical drive 2 goes backwards M569 P3 S0 ; physical drive 3 goes backwards M584 X0 Y1 Z2 E3 ; set drive mapping M350 X128 Y128 Z128 E16 I0 ; configure microstepping without interpolation M92 X632.71 Y633.66 Z3229.06 E397.09 ; set steps per mm M566 X540.00 Y540.00 Z12.00 E120.00 ; set maximum instantaneous speed changes (mm/min) M203 X12000.00 Y12000.00 Z1200.00 E3000.00 ; set maximum speeds (mm/min) M201 X800.00 Y800.00 Z100.00 E5000.00 ; set accelerations (mm/s^2) M906 X855 Y855 Z855 E855 I30 ; set motor currents (mA) and motor idle factor in per cent M84 S30 ; Set idle timeout ;M572 D3 S0.025 ; enable pressure advance ; Axis Limits M208 X-3 Y10 Z0 S1 ; set axis minima M208 X200 Y200 Z180 S0 ; set axis maxima ; Endstops M574 X1 Y1 Z1 S0 ; set active low and disabled endstops ; Z-Probe M307 H3 A-1 C-1 D-1 ; disable heater on PWM channel for BLTouch M558 P9 H5 F120 T6000 ; set Z probe type to bltouch and the dive height + speeds G31 P25 X13 Y54 Z1.659 ; set Z probe trigger value, offset and trigger height M557 X10:200 Y10:200 S40 ; define mesh grid ; Heaters M305 P0 T100000 B3988 R4700 ; set thermistor + ADC parameters for heater 0 M143 H0 S120 ; set temperature limit for heater 0 to 120C M305 P1 T100000 B4725 C7.060000e-8 ; set thermistor + ADC parameters for heater 1 M143 H1 S285 ; set temperature limit for heater 1 to 285C ; Fans M106 P0 S0 I0 F500 H-1 ; set fan 0 value, PWM signal inversion and frequency. Thermostatic control is turned off M106 P1 S0 I0 F500 H-1 ; set fan 1 value, PWM signal inversion and frequency. Thermostatic control is turned off M106 P2 S0 I0 F500 H-1 ; set fan 2 value, PWM signal inversion and frequency. Thermostatic control is turned off ; Tools M563 P0 S"E3D Hemera V6 .4" D0 H1 F0:1 ; define tool 0 G10 P0 X0 Y0 Z0 ; set tool 0 axis offsets G10 P0 R0 S0 ; set initial tool 0 active and standby temperatures to 0C ; Miscellaneous T0 ; select first tool M501 ; for saving
I'm going to run through the post stickied here today with the tuning macros, but if anyone has any thoughts/insight/experience, I'd love to hear it. I feel like I'm capable of tweaking and adjusting to many of the more common issues, but this one is feeling slightly more advanced.
jens55 last edited by
I ran into the exact same thing with PLA some time ago. I think I changed the order of inside/outside printing to fix it.
Your extruder temp is too hot, try reducing it by 15 or 20 degrees,
I had posted this on another thread the other day. I think it applies here as well.
I think these are the main generalized things for seam/blob minimization
Inner before outer layers
retract on layer change
retract for travels
quick and responsive Z and E axis
reatraction and PA tuned
quick unretracts and slower reprimes
try and maintain consistent volumetric flow rates between moves ( use same speed for internal and external perimeters. The version of Cura I use has the option to slow down on overhangs only. I'm usually trying to maximize my volumetric flow rate anyway.)
travel speeds and accelerations as fast as you can without skipping steps
carefully choose where the seam will be depending on the model. Some models have lots of nooks and crannies to hideit, others do not. Sometimes it's better to force it to a single side of a model.
E3D Titan Aero with 0.6 nozzle
M203 X12000 Y12000 Z600 E4000 ; Set maximum speeds (mm/min)
M201 X6000 Y6000 Z240 E3000 ; Set maximum accelerations (mm/s^2)
M204 P1000 T2500 ; Set printing and travel accelerations
M566 X1200 Y1200 Z120 E3000 ; Set maximum instantaneous speed changes (mm/min) (Jerk)
M566 P1 ; Set jerk policy to mimic Marlin and uses jerk between all moves.
M572 D0 S0.04 ; set extruder 0 pressure advance.
M207 S0.9 R0.0 F3600 T2700 Z0.0 ; firmware retraction settings
I think @jens55 is right about the inner/outer perimeter order. PETG is a pretty oozy material and even with retraction and pressure advance well tuned, the reprime amount after a travel can be a little less than needed to get a solid flow right at the start of the line. If the line happens to be an external perimeter, that will leave you with a small hole, and if the seam is lined up it can even lead to a huge gash as the holes all line up. Doing inner walls before outer walls allows you to hide your crimes so to speak.
Cura also uses combing where it tries to limit retractions and instead travels within the infill of the model where stringing and oozing doesn't matter. Combined with the default of Cura doing infill first, it doesn't usually matter. By the time it gets to the perimeters, the nozzle is primed. But if you're doing outer walls first, it will matter. So usually best to disable combing. Some cases where it can be useful is to avoid marring the surface of a top solid layer. It can avoid printed parts or even do a z hop. But those are special cases.
You may also think that you can use an extra reprime amount to cover the gap from the retraction ooze, but the amount that oozes is usually proportional to the distance traveled, so one single value for extra reprime isn't applicable in all cases. That said, sometimes a small amount of extra reprime is all you need.
In general I think it's better to prefer a retraction, especially with a direct drive extruder that has such tiny retraction to begin with. For a really long bowden extruder, retractions can add up to a lot in total print time.
rschlachter last edited by
Just wanted to come back here to post the results and close the loop. Overall, I was able to tune things and get things looking good. Here are the after pics https://imgur.com/gallery/Ogqr8lM
I did switch the order of the walls.
I printed the pressure advance test here https://forum.duet3d.com/topic/6698/pressure-advance-calibration/18 and adjusted accordingly. This made a nice improvement.
I lowered my print temp to 230. Might play around a little with this just to see.
I turned off combing. I did this more so because retraction on this extruder is tiny.
I also lowered my flow to 98%, lowered the speed of the walls to 60%, and turned on my cooling fan 30% after layer 3. For bridging I jumped the fan to 100%.
I've still got some slight ringing, but I'm going to tighten the belts a little and see how that plays out. They seem like maybe they are just a touch loose.