Hey there Klipper Skippers,
Just made the transition to Klipper to attempt to get some better print times. Done the calibrations and have Pressure Advance set to 0.55, max_accel: 3000 left at default, and retraction set to 0.75, and printing at 100mm/s.
The printer seems to like this for the axis movements, but the retraction seems brutally abrupt and I keep going to check on the print to find the extruder click clacking away after its snapped the filament off inside once it hits full speed when doing the infill. Looking at what the extruder is trying to do during retraction, it seems abrupt for a Bowden setup.
So I’m wondering, do I need to back the acceleration off just for the extruder?
I’ve seen someone post a setting for extruder acceleration, but it’s missing from my printer.cfg as per the sample.
So A, is this likely the culprit?
B. since the setting is missing, what would it be set to currently if I want to add the setting manually and back it off?
C. anyone else seen this?
Thanks.
You will really need to experiment to dial-in your settings.
A good starting point would be the stock Creality firmware, if they published the source code. If you look at their Marlin configuration you will be able to determine some of the key settings like maximum speeds, accelerations, etc. Just beware that my experience with CR-10S Pro indicates that they really do not test some of these settings. For example, the CR-10S Pro ships with maximum X and Y feed rates set to 300 mm/s even though the printer is really not capable of 300 mm/s. In my tests my (extremely) well tuned stock configuration maxes out at around 250 mm/s before it starts sounding like a chain saw. My curent heavily modified printer maxes out just above 200 mm/s, primarily because I upgraded the steppers to 0.9 degree Moons’.
The same can be applied to the extruder, except you have even more parameters to consider, including your hot end, the heater thermal flux (how fast it can melt the filament), the design of the extruder (the CR-10S Pro has a dual gear Bondtech which grips the filament like a vise), the quality of the Bowden tube & fittings, etc. The quality of your filament will also make a big difference - for example PLA becomes extremely brittle as it ages and absorbs moisture. So it is extremely difficult to troubleshoot remotely.
Having said this, I have been experimenting lately with my retraction setup and at the moment I settled on the settings shown below. I am only providing those as an example of a working setup, because your setup will be different. I do not have any issues with the extruder whatsoever, but these value do work the whole Bowden setup A LOT during retractions. I will be optimizing those further as I continue dealing-in my printer after the extensive “mod program”. Note also that I am showing below only the pertinent lines from the applicable configuration blocks of printer.cfg.
[extruder]
max_extrude_only_velocity: 150.0
max_extrude_only_accel: 5000.0
pressure_advance: 0.640 # Canadian Maker ToughPLA low sheen black @ 205 C, 0.28mm layer height (2021-06-22)
[firmware_retraction]
retract_length: 1.5 # Canadian Maker ToughPLA low sheen black @ 205 C
retract_speed: 55.0
unretract_extra_length: 0.0
unretract_speed: 25.0
Ok thanks for the reply!
One of the main reasons for moving to Klipper from stock Marlin, is that they ship it with far too conservative speeds. (AFAIK acceleration is set to 500 for everything).
This makes for nice looking prints, ease of use, and almost silent operation.
But with a recommended print speed of 50mm/s, you can image prints take days.
On 1st install of Klipper using the included sample config designed for this printer, I was blown away, its straight off the bat a 3-5 x speed increase and the prints look tidier even than the stock marlin. (the sample config sets acceleration to 3000 which is 6x stock)
It’s just the corners, and then pressure tuning that follows that seems to play havoc with retraction.
Anyways, it’s good to see your settings, and that its really a lower speed you want. 5000 acceleration would appear to be close to no acceleration at all from my knowledge.
Just one question now, in Cura I have Retraction speed set to 40mm/s. In this case, would I technically have to set Extruder Velocity to lower than 40 to have any effect?
Generally speaking PA puts a lot of additional stress to your extruder system. The higher your PA value, the higher the stress for the extruder.
This means PA heavily depends on your mechanical properties of the extruder system, i.e. gear ratio, tolerances, bowden length/quality, torque etc.
If your extruder starts skipping steps then this means it cannot cope with the fast acceleration / deceleration required by PA. This can be countered by either lower acceleration and/or giving some love to the mechanical aspects of your printer.
From my experience, trying to solve hardware topics (worn / lose bowden couplings, low torque stepper, bad tolerances in the bowden itself, cheap extruder systems etc) with software is hardly going to work.
Another aspect to consider is the maximum volume you can extrude: At 100mm/s with default line width and a layer height of 0.3 you end up with 14.4 mm³/s. Depending on hotend, material and temperature this might already be close to the limiting factor.
In consequence this means your hotend cannot “transport” the required volume and your extruder is pushing against a wall
In this context it is also extremely important to turn off dynamic acceleration or pressure controls in the slicer, e.g. coasting etc.
Ok thanks for the reply.
Yes with so many variables, I had expected much fine tuning would be needed. But my general understanding was that being there is a sample file included fluiddpi/flipper for my exact printer model, that the ball park figures set in this file are set and tested to be appropriate for the things you mention, stepper quality and torque, Bowden setup, hotend etc.
That said, the sample doesn’t have PA set, so that changes everything. I’ve been finding some reports about unexpected behaviour using retraction and PA together (like the extruder trying to extrude and retract at the same time) but the documentation does recommend a retraction of 0.75 when using PA.
In the end I just reduced the overall acceleration to 2250 as a happy compromise and print at 80mm/s (which ends up being just the infill in Cura without further adjustments). This is still a huge speed improvement over stock so color me happy.