extruder issue

[derrickoswald 0]

Hi,

I'm consistently getting spots worn away on the filament where the bolt grinds the material away, and extrusion mostly stops.

I have tried a few things http://derrickoswald.blogspot.com/2011/11/extruder-experimentation.html, like refastening the Bowden tube, and removing slack etc. but I have a new theory, based on how good it works after the print gets going.

I think that when the print starts, the temperature control of the head stops, for the length of time start.txt takes or so, and then control resumes after that.

So maybe it's my workflow that's at fault. Here's what I do.

Start ReplicatorG and generate GCODE if necessary.

Connect to the machine.

Start the Control Panel.

Set the target temperature to 260. (the current temperature will eventually be 11 degrees less that that).

Use the X, Y and Z jog position to move the head to the start position.

Zero the current position.

Lower the bed 5 mm.

Wait for the temperature to stabilize at 249 degrees.

Raise the bed 5 mm.

Close the Control Panel.

Push the Build button.

Watch the bed lower and the extrusion start going.

Wipe off the excess plastic.

Watch the bed raise and the print start.

Within 30 seconds or less than a minutes, the first layer of plastic stops and the filament is stripped.

Could it be that the firmware I'm running has a flaw that turns off the heater while the preamble is running?

Here's the start.txt and print preamble:

G21 (This is GCode, generated with Skeinforge version 35 from ReplicatorG)

G21 (Ultimaker profile - Quality print from alterations/start.gcode)

G21 (Metric: The unit is a millimeter)

M18 (Disable motors for now, to allow manual moving of the head)

G90 (Absolute positioning)

G92 X0 Y0 Z0 E0 (set origin to current position)

G91 (Relative positioning)

G1 Z35.0 F400 (lower platform for cleaning nozzle)

G92 E0 (zero the extruded length)

G1 E260 F1000 (extrude some to get the flow going)

G1 E-20 F3000 (reverse a little)

G92 E0 (zero the extruded length)

M1 (Clean the nozzle and press YES to continue...)

G1 Z-1.0 F100 (rise platform again)

G1 Z-34.0 F400 (rise platform again)

G90 (Absolute positioning)

G1 Z0.4 (Tool slightly above the platform)

G92 Z0.4 E0 (zero the extruded length)

G21 (end of start.txt)

G90

G21

;M103

M105

M106

M113 S1.0

;M108 S58.87

M104 S245.0

;M108 S61.81

G1 X-31.78 Y-31.79 Z0.3 F1620.0

;M101

G1 X-31.78 Y38.01 Z0.3 F1620.0 E159.783

G1 X31.79 Y38.01 Z0.3 F1620.0 E305.305

G1 X31.79 Y-31.79 Z0.3 F1620.0 E465.088

G1 X-31.78 Y-31.79 Z0.3 F1620.0 E610.61

;M103

G1 X9.9 Y-24.46 Z0.3 F2880.0

;M101

Any ideas?

[derrickoswald 0]

Further info...

It seems that the object I'm trying to make might be the cause. It has a large number of short strokes at the beginning of the profile and this might be causing the hiccup.

[ddurant 0]

I'm consistently getting spots worn away on the filament where the bolt grinds the material away, and extrusion mostly stops.

:(

That's called 'stripping' as in "you've stripped the filament.."

I think that when the print starts, the temperature control of the head stops, for the length of time start.txt takes or so, and then control resumes after that.

The temperature is controlled by the firmware on the machine. RepG (or whatever is feeding it gcode) tells it what the temp should be and that's it - there's nothing else needed on the PC side to keep it at that temperature. You could turn off your PC and the machine probably stay at whatever value you set it at last.

I don't see any reason why it'd stop maintaining temperature while start.txt is happening.. Could be but I really don't think so.

Start ReplicatorG and generate GCODE if necessary.

Personally, I think it's a better idea to use repg as just a something that feeds gcode to the machine. You're better off (IMO) using skeinforge by itself to do the slicing instead of using the version integrated into repg.

Set the target temperature to 260.

That's too hot!!! I've been printing at 225 and that's been working pretty well.

One thing to watch out for is leaving the machine hot while it's idle. The plastic will work its way out of the nozzle and that can mess up the start of your print and (possibly) encourage heat to travel back up the hot end and form the dreaded PLA-plug that people have been talking a lot about lately. This is especially true if you're really putting the spurs to the heater (which you are).

Within 30 seconds or less than a minutes, the first layer of plastic stops and the filament is stripped.

Are you sure you're not starting too low? If the nozzle is too close to the platform, the filament drive won't be able to push more filament into the system and that'll cause it to strip..

Could it be that the firmware I'm running has a flaw that turns off the heater while the preamble is running?

Nope - the firmware just sees gcode lines coming in. It has no concept of start.txt.

Here's the start.txt and print preamble:

.

.

G21 (end of start.txt)

.

.

M104 S245.0

M104 is the "set temperature" command and there's nothing before it to do some other temperature..

Do you print with a raft? That might be a good thing to try as rafts are made of big, slow lines that should be really easy to print..