Extrusion steps per mm issue

[abear]

Hi all,

I have been trying to calibrate my "the Beast" from Cultivate3d after installing an e3d titan extruder and e3d V6 hotend.
I found I could always get the steps per mm, just perfect as long as I didn't change
- the filament brand
- the pressure on the extruder idler
- the FEED RATE on the G1 command

Just think about that for a bit...the feed rate.. hmm, the feed rate changes throughout your print, maybe not by a huge amount...Unless you have a big printer, with big areas and the ability to vary from very slow to very fast.
Feed rates also change depending on your LAYER height.

So if you calibrate your printer, and then change layer heights to get a fine print of what have just been doing in "rough" draft prints on a low resolution. DON'T expect a good quality print, you'll likely be over extruding as you have reduced your layer height and therefore your FEED RATE, as a result your steps per mm calculations are out.
This is obviously cause by some level of slippage/grinding on the filament at higher feed rates.
Therefore the only way around this (currently) is to always print slow and ensure your feed rate never changes too much (i.e. below 30mm per second).

Attached is an Excel spreadsheet of my test results.

Extrusion Calibration.xlsx

Standard Extrusion calibration errors

(11.45 KiB) Downloaded 255 times

How can we address this properly?
The firmware developers could/should cater for this.
It would be a simple matter of changing the 1 "steps per mm" calibration procedure to measure at 3 different feed rates and enter the steps per mm for each feed rate. The firmware could then calculate the "lag" curve represented by the slippage/grind on the filament.

Alternatively, Simplify3d could cater for this and make it part of the "material" profile. Altering the feed rate based on the layer height selected AND the filament selected. (i.e. a calibration procedure would be needed for each filament type you used).

Simplify3d...
Can you add this feature? It would certainly help me. I only ever use 1 brand of Filament, but I am frequently changing layer height to print final quality parts. Users (who could be bothered) would only need to calibrate for each type of material they use (I doubt ambient temperature would make a significant difference within a region).

Adrian

[brian442]

The firmware will already adjust the extruder speed correctly depending on your feedrate, so the actual speed that is uses is already correct, regardless of what speed you are using.

But, that being said, it's possible your extruder just starts slipping or grinding at high speeds which would explain the problem you are seeing. If that is the case, just change the maximum extruder speed and acceleration in the firmware settings. That will make sure you don't try to extrude too fast.