Calibration of Ormerod
The aim is to calibrate the Ormerod so that I can accurately print meshing gears for my BluRay Robot. My current version doesn’t work well enough.
I also want to explore using the stepper motor limit currents to allow probing of the extruder. I am assuming that the limiting current is proportional to the force.
Good Prints
Requires both Slic3r settings and RepRap firmware settings to agree as well as be calibration to actual hardware and to the filament.
Motor Currents and stall detection
The new duet hardware and firmware is able to detect and log motor stall currents. It also allows the motor
current to be reduced by a proportional amount from the maximum that is set in the sys/config.g file as M906
Stage 1 the Extruder
- Filament All these experiments are done with Red Translucent PETG from www.real-filament.com. Relatively reasonable price, free delivery by Amazon and quality seems ok so far.
- Nozzle E3D 0.25 mm
- DuetWifi on 2.0 firmware
- Filament Ormerod 1 as modified by H3
- Settings file As you change the settings file you vary the effect of the extrusion.
1a Empty extruder
Taking off the bowden tube and zeroing the filament allows you to test the extruder length and required currents.
First try to find lower limit load
First remove the cold extrusion limit. Currently the extruder is set to a limit of 1.2A. I have found that althougth the driver can do up to 1.8 to 2A the stepper motor gets very hot. I had to use a high current with a worn gears and a bad filament path.
- Starting condition make sure extruder works. Bowden tube disconnnected. No load filament path.
- Remove cold extrusion limit by
M302 P1, (M302reports current situation) I think cold extrusion limit is hardcoded to something like 160. 
Test can extrude and retract 10mm. Which I can (although response not instanteous, maybe WIFI problem)
- Remove cold extrusion limit by
- Try out reducing feed current and logging stall
- Log stalls on Extruder. Hit first snag, the extruder doesn’t appear to be a valid motor
M915 E S10 F0 R1This seems to be ok but not sure. - Reduce current, set extruder 0 to 5% of normal current
M913 E5 - Tried at high current and just go humming noise
- Log stalls on Extruder. Hit first snag, the extruder doesn’t appear to be a valid motor
- Try and read the log
- See logging page.
- Set logging on
M929 P"extruderLog.txt" S1and rerun extrude but only 10mm this time. Get short hum - Extruder log says logging has started but there is no log.
. So the logging hasn’t worked - Turn loggin off and just use the hum. Also planning to change the macro files for quick testing.
- gave up macro as need to take sd card out.
- Turn logging off
M929 S04 Test no load at 15mm/sec - Use binary chop of extruder current - Extruder set to 1.2A
| Load | Direction | Result |
|---|---|---|
| 5% | Extrude | |
| 30% | Extrude | |
| 17% | Extrude | Stuttering |
| 23% | Extrude | |
| 20% | Extrude | Stuttering |
| 22% | Extrude | |
| 21% | Extrude | Stuttering |
| 22% | Extrude | |
| 22% | Retract | |
| 21% | Retract | |
| 17% | Retract | Stutter |
| 18% | Retract | |
Result Extrude 22%, Retract 18%
5 Retest at 5mm/sec, 24C
| Load | Direction | Result |
|---|---|---|
| 17% | Extrude | |
| 13% | Extrude | |
| 8% | Extrude | Stutter barely audible |
| 11% | Extrude | Stutter barely audible |
| 12% | Extrude | Stutter barely audible |
| 13% | Extrude | |
| 11% | Retract | |
| 12% | Retract | |
| 13% | Retract | |
Result Extrude 13%, Retract 13%
6 Retest at 60mm/sec, 24C
| Load | Direction | Result |
|---|---|---|
| 13% | Extrude | |
| 28% | Extrude | Stutter |
| 32% | Extrude | |
| 30% | Extrude | |
| 29% | Extrude | Stutter but not evenly |
| 29% | Retract | |
| 25% | Retract | |
| 21% | Retract | |
| 23% | Retract | |
| 22% | Retract | |
Result Extrude 29%, Retract 22%
Test effect of unwinding and path
Need longer sections of filament so will test 100mm. Can also use to measure length.
Only need to measure extrusion.
100mm at 60mm/sec at 24C
| Load | Direction | Result |
|---|---|---|
| 29% | Extrude | fails when needs to unwrap from PrintDry |
| 32% | Extrude | Stutter |
| 33% | Extrude | Stutter |
| 35% | Extrude | Occasional Stutter |
| 36% | Extrude | Occasional Stutter |
| 38% | Extrude | |
Length 98.7, 98.68 Diameter 1.73,1.75,1.73
Now taking path on top
| Load | Direction | Result |
|---|---|---|
| 38% | Extrude | |
Length 98.9
Going to tweak gearing calibration
Extrusion at 15mm/sec 100mm
- Changed gearing from 4000 to 4053 = 4000 * 100 / 98.7.
- Rebooted and need to remove cold extrusion limit again
M302 P1 - Changed the Z axis
- Changed gearing from 420 to 426.0 = 420 * 100 / 98.6
- Measured length 99.8, 100.12
X axis stall
Trying lots of variations but cannot get stallguard to work.
Just checking to convert steps/second to mm/min so in the X axis
F1000 = 1000mm/min = 16.7 mm/sec
M92 for X is set at 87 steps/mm so 16.7 mm/sec = 1450 steps / sec.
For stall guard it needs to be above 200.
Trying higher sensitiviy
Sensitivity ranges from -64 to + 63, not recommended to go below -10 but going to try most sensitive to see if it will trigger at all.
Nice idea but I can’t get stallguard to work
Ooops Axes on Duet Wifi are not numbered in squence so I was using setting Stallguard on P2 that I thought was X
New features
- Stall detection M915
- Pressure Advance?
2018-06-29 Update
Have turned off pausing on stall (M915) and have turned on logging. Also boosted X axis current from 800 to 900 mA Y axis still at 1200mA.
Nozzle is 0.4mm (I thought I had installed 0.25, however extrusion settings were set for a 0.4mm nozzle)
Going to create calibration first layer
Tests both extrusion of first layer and also correct bed height.
First sample
eg square single layer thickness and then a a quaer double layer, and 1/8th triply layer and then 5mm lever to take off surface easily.
Looking to see if get even fill
Then print at different temperatures to test adherence and quality.
First layer height is 0.4mm and subsequent are 0.2mm.
Z calibration displayed 1.4 measured 1mm +-0.3mm using cards.
2016-06-29 Too high - as bottom not all shiny (some dull patches) Under extrusion as when bend it, breaks into harp like threads ( in parts)
Can half height of square tower grip from 5mm to 2.5mm, nice to have something to hold onto. Also reduce from 3 layers to 2 layers thick.
Calibration 2
The first time I really focused on the extruder, I have since changed gears and think the problem was with the gears so probably worth revisiting. The current plan is to:
- Measure filament (need calipers)
- Do temperature calibration
- Do thinwall calibration
- Do calibration print
- do Fit check
Temperature calibration
Going to use a tower block from Eibwen.
(testing python GCODE modifier)
Downloaded the stl file into
C:\Users\HumphreyDrummond\CloudStation\A Letter-2018\2018-11-14 3d temperature calibrationNeed to download the OpenScad file for temperature range you are using as their are letters on the model.
Imported into Slic3r
created new filament for Blue PLA that I am using
- 1.75mm
- 190-220 C
Nozzle / filament calibration
Here is a quote that nozzle diameter may not be that important:
https://reprap.org/forum/read.php?1,113374,113953
Calibration is by single wall vase and measeuing wall thickenss.