extruder reverses at beginning

hi, just got into skeinforge and I can't figure out why the extruder reverses sometimes at the beginning of print.

It reverses so much that the filament comes out entirely.

So, what the hell?

Are you using the RepRap Host?
Are you pressing the extrude button (one or more times) before starting the print?

If the answer do BOTH questions was YES then don't do that anymore!

If I change filament color then I press the extrude button several times, THEN I:
* EXIT the RepRap Host
* Reset BOTH the extruder and mother boads
* Start the RepRap Host
* Load the desired GCODE file
* Press the PRINT button

If I load a GCODE file and start a PRINT AFTER pressing the extrude problem the extruder also runs backwards at the start of the print. I have been meaning to look at what code the RepRap Host sends to do the extruding but haven't gotten around to it yet.

---

Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

Thanks!

I'm using repsnapper.
But running the extruder before printing seems to be the problem.
Thanks for the help, bit strange though =)

THEN DON'T DO THAT!

Then RepSnapper has the same problem.
Good to know.

Since I use Skeinforge and the Outline plugin I only need to use the extrude button when I change PLA colors.
I always reset both boards and restart the RepRap Host after pressing the Extrude button and then I don't have any problems.

---

Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

@JnsMuovi

What is happening is when you instruct the printer to extrude it sets the E value to some value. The more you extrude the higher the E value will be.

Then when you print your gcode probably gives the printer a low E value command, expecting the current E value to be 0. The net result is that the extruder must reverse to get to the instructed point...

Simply edit your start.gcode file which should be in your ...\skeinforge_application\alterations directory to contain the gcode G92 E0 which will set the extruder's current value and position to 0.

Also ensure that your Preface tab has the start.gcode file in the correct place (see pic).



The contents of the start.gcode file is appended to the front of your gcode created by skeinforge.

notice the button with the question mark next to the button named preface? If you click that it will open a help page explaining contents of the Preface tab. Each tab has a question button which will take you to the relevant help page

for reference, included is my own start.gcode file below.

G21 ;metric is good!
G90 ;absolute positioning
T0; select new extruder
G28 ;home all
G92 E0 ;zero the extruded length
M113 S0.0 ;switch off extruder motor
G1 F3000.0; feed for start of next move
G1 X120.0 Y3.0 ;horizontal move
G1 F70
G1 Z1.0
G1 Z0 F70
M109 S210.0 ;set temperature and wait
M113 ;turn on extruder motor
G1 F30 ; feed for start of next move
G1 E15.0 F40; extruder dwell
G92 E0 ;zero the extruded length
G1 F4500.0; feed for start of next move

Edited 3 time(s). Last edit at 04/08/2011 04:03PM by AgeingHippy.

This info would be a great addition to the Skeinforge wiki page's Troubleshooting section.

Unfortunately I have always had a "G92 E0" in my START.PLA and it has never fixed this problem.

---

Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

stupid question, but is it in your generated gcode? Maybe you are priming your extruder after sending the G92 E0 instruction and then not resetting it to 0?

But then you say it only happens when you have extruded using some form of host before actually printing....?? weird.

Perhaps you can post the initial section of your gcode here for fresh eyes to peruse?

Yes. You can't solve this without looking at the actual g-code.

Here, the start of the Android Device Rest (as an example):

M104 S210
M116
G92 E0
G1 F50
G1 Z8.0 F50
G28 Y0
G92 Y0
G28 X0
G92 X0
G1 X135.0 Y5.0 F2300
G28 Z0
G92 Z0
G1 Z8.0 F90
M109 S210
M113 S0.75
G1 Z0.2 F90
G92 E0
G90
G21
M140 S70.0
M141 S0.0
M142 S0.0
M113 S0.75
;M108 S35.0
M104 S210.0
;M108 S21.0
;M108 S21.0
;M108 S8.4
G1 X44.2 Y48.28 Z0.38 F1920.0
G1 F28800.0
G1 E50.0
G1 F1920.0
G92 E0
;M101
G1 X44.2 Y151.72 Z0.38 F525.0 E99.299
G1 X155.82 Y151.72 Z0.38 F525.0 E206.449
G1 X155.82 Y48.28 Z0.38 F525.0 E305.748
G1 X44.2 Y48.28 Z0.38 F525.0 E412.898
G1 F28800.0
G1 E362.898
G1 F525.0
;M103
G1 X68.25 Y56.61 Z0.75 F1920.0
G1 X67.64 Y56.4 Z0.75 F1920.0
G1 X68.25 Y56.61 Z0.38 F96.042
G1 F28800.0
G1 E412.898
G1 F96.042
G92 E0

If I extrude using the RepRap Host BEFORE starting the print then the extrude starts to run backwards which ruins the beginning of the print.

If the extrude button is not pressed this does not happen.

---

Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

Hi Bob

Seems like a lot is going on here in your code.

I have commented a section and inserted line numbers for ease of reference

1 - M104 S210   ;set temp
2 - M116          ; wait to reach temp
3 - G92 E0       ; set Extruder to 0
4 - G1 F50      ; set feedrate 50mm/min
5 - G1 Z8.0 F50 ;move Z axis to 8mm
6 - G28 Y0       ; Home Y axis
7 - G92 Y0       ; set Y axis co-ords to 0 (redundant as you have just homed the Y axis so the Y value is already 0)
8 - G28 X0       ;home X axis
9 - G92 X0       ; set x-axis co-ords to 0 (redundant)
10 - G1 X135.0 Y5.0 F2300 ;move to dump point
11 - G28 Z0       ;Home Z axis
12 - G92 Z0       ;set Z-axis co-ords to 0 (redundant)
13 - G1 Z8.0 F90 ;Move Z to 8mm
14 - M109 S210   ;Set extruder temperature and wait to reach (repeating lines 1&2)
14 - M113 S0.75  ;set motor PWM (?) to 75%
16 - G1 Z0.2 F90 ;move Z axis to 2mm
17 - G92 E0        ;Set Extruder to 0 (again? but you have not extruded since last reset)
18 - G90            ;Set absoluter positioning
19 - G21            ;Set to metric (Personally I would put this first - what units are the previous instructions in?)
20 - M140 S70.0 ;set bed temp to 140
21 - M141 S0.0  ;set chamber temperature to 0
22 - M142 S0.0  ;set bed holding pressure to 0 (??? huh - never seen this one??)
23 - M113 S0.75 ;Set motor pwm to 75% (already done in line 15)
24 - ;M108 S35.0 ;commented out (by your replace.csv?)
25 - M104 S210.0 ;set extruder temp - I am guessing we have left the start file and this is skeinforge generated
26 - ;M108 S21.0 ;commented out (by your replace.csv?)
27 - ;M108 S21.0 ;commented out (by your replace.csv?)
28 - ;M108 S8.4 ;commented out (by your replace.csv?)
29 - G1 X44.2 Y48.28 Z0.38 F1920.0 ;move to print start position
...

I wonder what is happening when you instruct it to move to Z8 mm when the Z axis has not yet been zeroed?

Perhaps you should try simplifying your start.gcode file to something similar to mine?

If it is safe to Home your Z axis why not do
the following

G12 ;set to metric - this replaces line 19
G90 ;Set absoluter positioning - line 18
G1 Z8.0 F50    ;move Z axis to 8mm with feed rate 50mm/min
G28 X0 Y0 ;home X and Y axis (replaces lines 6-9) (if it is ok ho home Z I would also do so here else include next line)
G1 X135.0 Y5.0 F2300 ;move to dump point with feed rate 2300mm/min
G28 Z0 ;home Z axis (replaces lines 11 and 12)
G1 Z8.0 F90 ;Move Z to 8mm - guess you do this so you an remove any ooze... ?? is it neccesary if you are over the dump point??
M109 S210   ;Set extruder temperature and wait to reach (replaces lines 1&2 and 14)
M113 S0.75  ;set motor PWM (?) to 75%
G92 E0 ;set Extruder length at 0
G1 E100 ;extrude 100 mm to prime extruder (this is extrudate length rather than feedstock length I assume??)
G92 E0 ;set Extruder length at 0
G1 Z0.2 F90 ;move Z axis to 2mm

I would actually simplify it a little more if I knew your circumstances.

Perhaps you should also at the very least place your current line 19 and 18 BEFORE you set the Extruder position to 0.

so ...
G12 ;set to metric - this replaces line 19
G90 ;Set absoluter positioning - line 18
before
G92 E0 ;set extruder position to 0

You could also try deleting the lines that are only comments (those starting with a semi-colon)

Hope this helps. let me know

I just included the start of a created gcode file.

My START.GCODE is as follows:

M104 S210
;M140 S140
M116 ;WAIT for all temperatures to reach set values
G92 E0 ;zero the extruded length
G1 F50 ;clear the bolt heads
G1 Z8 F50 ;clear the bolt heads
G28 Y0 ;home Y
G92 Y0 ;adjust Y absolute zero
G28 X0 ;home X
G92 X0 ;adjust X absolute zero
G1 X135 Y5 F2300 ;move to dump location
G28 Z0 ;home Z
G92 Z0 ;adjust Z height for optimum 1st layer adhesion
G1 Z8 F90
M109 S210
M113 S0.75
G1 Z0.2 F90
;G1 X10 E360 F1500
;G1 E360 F2300 
G92 E0

---

Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

I know

Let me know if trying what I suggested helps or not.

The Z-axis was zeroed in lines 11 and 12.

---

Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

yes Bob, but I assume you are zeroing the Z-axis at the dump point rather than at the origin because you are concerned about a possible head crash?

The issue is not with the Z axis.

I will repeat what I suggested...

Perhaps you should (also) at the very least place your current line 19 and 18 BEFORE you set the Extruder position to 0.

so ...
G12 ;set to metric - this replaces line 19
G90 ;Set absoluter positioning - line 18
before
G92 E0 ;set extruder position to 0

Now I know you cannot remove those lines since that is what skeinforge does, but you can still add them at the start of your gcode start file

You could also try deleting the lines that are only comments (those starting with a semi-colon)

Tomorrow I will be changing my filament color so I will give your suggestions a try then and see if it helps.

---

Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

G12 kenne ich nicht

---

Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

oops

Enshuldegung bitte.

My age is causing me to transpose numbers.

G21 tells it to go metric

(Just as well I did post preview. I put G12 again lol)

My START.GCODE now looks as follows:

G21              ;Set to metric
G90              ;Set absolute positioning
M104 S210        ;Set Extruder temperature to 210 degrees C
G92 E0           ;Zero the extruded length
G28 X0 Y0        ;Home X & Y
G1 X135 Y5 F2300 ;Move to the dump location
G28 Z0           ;Home Z
M116             ;WAIT for all temperatures to reach set values
M113 S0.75       ;Set Extruder PWM to 75%
G1 Z0.2 F90      ;Move UP 0.2 mm

And it appears to work properly now. Thanks!

---

Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

Nice one

Glad it worked

im not getting end.gcode or start.gcode in the preface tab



any ideas

thanks in advance