M2 V4 Starting Issue

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M2 V4 Starting Issue

Postby peterbrown77 » Thu May 18, 2017 6:53 pm

Hola -

I'm having trouble with the very beginning of a print. The hot end is not extruding any material for the first 2 or 3 inches of travel; this leads to raft problems because it can't attach the ends of the pattern and it lifts up.

Part of the startup GCODE is to extrude some material before doing a wipe, so it's not as if the extruder is starved of PLA. It moves to the right of the platform, spits out 8 or 10 inches of PLA, then starts doing the raft.....except there's no material coming out of the nozzle. From there it proceeds normally....

TIA
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Re: M2 V4 Starting Issue

Postby Hugs » Thu May 18, 2017 8:28 pm

Can you post the first bit of gcode from one of your problem prints? It sounds like after the initial prime/purge/wipe there's a retraction that may be a bit too much. So the filament is retracted after the wipe and has to make up for it when it starts printing.

For example, here's a snippet from one of my prints that relates to the prime/purge/wipe:

Code: Select all
G1 Z5 F2000 ; lift nozzle
G1 F3000 X220 ; move off the bed to the right
G1 F2000 Z0 ; move the nozzle back to bed height
G1 F200 E10 ; prime/purge at a slower feed rate
G1 F1000 E9 ; prime/purge at a higher feed rate
G1 F3000 X190 Y50 ;move back on the bed doing a wipe


Then set temps and get ready to print

Code: Select all
M201 X1000 Y1000 ; slows acceleration
G92 E-1
G1 F2000 Z2
M109 S215 T1 ; set extruder temperature and wait for it to be reached
[etc.]
G1 E-2.00000 F2400.00000 ; <-- this is a retraction, since it may ooze while waiting for temps to come up
[...]
G1 F1200 ; start the actual print
G1 X111.170 Y118.943 E2.02395


Just a thought (and have you tried adding a skirt?)...
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Re: M2 V4 Starting Issue

Postby Matt_Sharkey » Fri May 19, 2017 2:06 am

Have you calibrated your Z-Height? Have you leveled your bed?

If your nozzle is too close to the bed, it won't be able to extrude anything.

Are your extrusions consistent otherwise?

If not, you may have your filament tension set poorly. easiest way to check is to withdraw the filament and examine the bite marks in the filament. it should bite through about 10-20% of the filament thickness.
another thought may be a clogged extruder, which happens with wood fill filaments as well as frequent switches between PLA and high temp filaments.
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Re: M2 V4 Starting Issue

Postby peterbrown77 » Fri May 19, 2017 11:25 am

Here is a typical program:
========================================================================
;FLAVOR:RepRap
;TIME:3888
;Filament used: 4.04383m
;Layer height: 0.2
;Generated with Cura_SteamEngine 2.5.0
M190 S70
M104 S220
M109 S220
G28 ;Home
M108 S255 ; turn on fans
G1 Z15.0 F6000 ;Move the platform down 15mm
G92 E0
G1 F200 E3
F1 E25 F255 ; purge nozzle
G92 E0
;LAYER_COUNT:230
;LAYER:-6
M107
G0 F3600 X80.858 Y94.147 Z0.36
G1 F1800 X82.003 Y93.284 E0.15022
G1 X82.244 Y93.119 E0.18082
G1 X83.133 Y92.56 E0.29084
===================================================================================

I've leveled the bed and the gap is fine. Once the PLA starts coming out, the results are good..... it's just that very beginning that's problematic. I've cleaned the nozzle more than once as I've had partial clogs and the bite marks are significant so i don't think it's slipping (I can't remove it by hand).
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Re: M2 V4 Starting Issue

Postby Jules » Fri May 19, 2017 2:39 pm

There's a small retraction on the Rev E machines when the actual printing starts....never got a chance to figure out a way around it - I just do a separate skirt - about 2 or 3 outlines, and it takes care of that issue.
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Re: M2 V4 Starting Issue

Postby peterbrown77 » Fri May 19, 2017 7:23 pm

Problem is (with Cura) that you get a choice of Raft, Skirt, Brim.... you can't combine them. So if i go Skirt, I can't get a Raft too.....
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