Extruder steps by mm Calibration

K8200 3D Printer K8200 - Printer software (repetier, slicer, ...) a
1

Hi,

I found no post about the extruder feed calibration on this forum and it’s one of the more important parameter to have good dimensional accuracy and good filling of printed part.

I checked on my K8200 and the standard value of 600 steps/mm (at standard 1/16 microstep) in the firmware is not correct.

To have a correct lenght of fillament pushed Inside the extruder I need to use a value of 715 steps /mm instead of 600. With this value when I ask to Repetier to extrude 50mm of fillament I have realy 50mm of fillament pushed.

But despite this calibration I must now use an extrusion multiplier in slic3r between 0.85 and 0.9 to have an extrusion width and a part accuracy near from the theorical value defined in my slic3r settings.
The external part dimensions are corrects but all the holes in part are always a little too small, for exemple for a cube of 20mmx20mmx10mm with a hole of 10mm in the center, I measure 20.05mmx20.05mmx10.0mm and 9.8 or 9.7 mm for the hole diameter.

I have a good Z accuracy because I have replaced the Z axis screw by a precision threaded rod with a new bearings and a rigid holder in top with a flex coupling between rod and motor.
I also replaced X,Y and Z motors by 400 steps by turn motors and the T5 belts and pulley by MXL type to have more smooth and more precise movement.

Standard profile for PLA from Velleman give an extrusion multiplier of 1.1, it’s like if we use a multiplier of 1.0 with a firmware feed adjusted to 660 Steps/mm (6001.1=660).
In my setup I use 715 steps/mm and a multiplier of 0.9,it’s like if we use a multiplier of 1.0 with a firmware feed adjusted to 643.5 Steps/mm (7150.9=643.5).

Of course I have measured my velleman black fillament to a mean value of 2.93mm and used this value in slic3r.

It would be interesting to discuss about all the parameters who can explain that with good calibration of extruder it’s always necessary to use a multiplier and to tune all the advanced Slic3r parameters to try to reach good results.

For exemple, one thing that we can’t precisely check is the nozzle hole diameter, velleman say it’s a 0.5mm nozzle but the presision of the machined part are not a constant and if the nozzle is realy de 0.55 or 0.45 mm it can influence the final result.

I also have an UP! Mini printer and this one is realy a lot more accurate that the K8200 and there is almost no parameters that we can or we need adjust but the final result is always very good and better than with the K8200.

2

I had an almost identical experience in October 1014.

How can it be that Vellerman has “tweaked” all the parameters to approximately produce a good print even though things as basic as the extrusion rate and extrusion multiplier are wrong wrong wrong!?!

Did the boys at Vellerman supply a set of bogus parameters just because they seem to work? Is it possible that nobody ever checks something as basic as extrusion rate but you and me?

When you add the z axis problem to the bogus parameters and lousy print quality, it seems Vellerman has done us all a disservice.

How can it be that a true value for extrusion feed rate and a true value for filament diameter cannot produce a good print? Others need to explain to me how it is possible to get good results with this printer. If anyone wants to take on that challenge, I’d like to know if they ever measured the feed rate and filament diameter?

The problem with fudging phony parameters is that they only work for a singe print, or very similar prints. I’d like to challenge Velleman to publish the slic3r setup parameters they used for their video of the Gyro Cube. With an extruder feed rate off by 25%, what other screwy parameters had to be fudged to make it work? And would those same parameters work for something as simple as a calibration cube?

Disappointed,
Art

3

reprap.org/wiki/Triffid_Hunter’s … de#E_steps

4

I’ve tried using this guide. Personally, I’ve been able to print only simple calibration files with a setting of 0.25 for layer height. Anything complex always fails on the upper layers when the extruder collides with the printed object and rips it off the print bed.

I can print complex objects at 0.35 layer height only. I’ve seen claims that some people print at 0.15 with the K8200. I’d like to see a poll of what results people get with the stock machine, not having bought a E3DV5 extruder or bought a leadscrew for the Z-Axis.

You are free to believe that I am incompetent and did not build my K8200 carefully, or do not know hoe to calibrate it, or do not understand scilc3r parameters, or don’t know how to make things print to a 60 degree print bed with 3M blue painters tape. But I don’t believe those things are true. I know that I cannot print anything nearly as complex as the gyro cube at 0.25 mm layers.

As I said, the K8200 will print for hours before the extruder collides with the printed object and rips it from the bed. Sometimes it sticks, but a portion of the object is broken off. The rest is sticking so well that I have trouble removing it!

I have no clue how to print at 0.25.

Art