FlashForge Creator Pro 2016+ extruder lag

[tbfohman]

Good day,

I hope someone can help me with this.
When starting any print, the initial extrusion doesn't create extrusion for approximately 5-10mm.
I mean, the toolpath is running, but no plastic comes out at the start. This distance is the same for any partfile.
This doesn't seem to be a temperature, or nozzle flow issue - I've messed with both. I've also experimented with retraction length and restart distance.
Any help would be greatly appreciated.

[brian442]

This is pretty normal. It's why you use a skirt. That way the extruder can get fully primed on the skirt before it moves to the actual model.

[tbfohman]

Thanks so much for the reply....

Does it need to "re-prime" after the initial prime/wipe at the edge of the table?
I've been researching, and it seems that there might be a "deprime" command in the generated G-code/x3g.
If this is true, then this would negate the priming routine at the end of the start script (I would imagine)
Is there a way to disable the FFCP's deprime function?
I use a skirt to verify all is good, but what often happens is the extrusion starts slowly extruding (while traveling) and a tail or a curl is created at the beginning of the extrusion line. This tail mucks up the following layers, and has even been snagged a drug about with the secondary nozzle.
(You can see this tail in the "start here instead" circle - pointing toward 8 o'clock, in the original post's image)

[brian442]

Again, this is really normal, and I see this on almost all of my printers. That's why you use a skirt, since you just throw it away in the end.

But if you really want to mess with it, then you could probably write a custom starting script to prime the nozzle someplace else

[tbfohman]

Hey Brian - thanks for getting back with me.
My start scripts do prime the nozzle (purges 15-20mm), extrude a line across the bed, and wipe the nozzle. She then moves to the starting point of the print. I also do use a skirt with no part offset to aid in bed adhesion.

When starting the actual print, at the starting point, the extruder lags in producing extrusion for around 5mm. I honestly can't think that this would be normal operation. I've attached a factory file, if you'd like to check it out.

Thanks for your help with this.
-Scott

[dkightley]

If you're referring to the visual representation of the printing not exactly mimicking the actual printing process whilst you print via USB....then what you describe is exactly what happens....and nothing is wrong.

Because there is no feedback from the printer, the software has no idea what the printer is doing. It merely transmits a series of commands to the printer via the USB connection....and the simulation speed is calculated from the same sequence of commands. Printers take different times to execute the stream of commands....hence the real print lags behind by an unknown time delay.

Hope this explains things...

[tbfohman]

Hey Doug - thanks for your reply. The image in my original post is the actual print-in-progress. I print from SDcard and do not connect to the printer. I cannot believe this is "normal operation". the plastic should come out of the extruder at the beginning coordinates of the print.

[dkightley]

Having taken a look at the generated gcode for both your part and an example of one of my own prints, I can see something slightly amiss that not only will explain what you're reporting, but seems somewhat silly!

An extract from your gcode...covering the lines at the start of the first line of the skirt:

Code: Select all

M73 P1 ; @body (notify GPX body has started)
G1 E-0.9000 F3000       <================================ LINE ONE
G1 Z0.270 F3000
; layer 1, Z = 0.27
M135 T0
; tool H0.300 W0.480
; skirt
G1 X-78.640 Y23.883 F4200
G1 E0.9500 F900    <================================== LINE TWO
G1 X-78.640 Y-25.264 E2.9423 F1800
G1 X-78.682 Y-25.759 E0.0298

Note the filament retraction in line 1 at a speed of 3000, and the re-feed in line 2 at a speed of 900....at the exact point the "lag" has been reported!

Now, similar lines at the next retraction of the filament:

Code: Select all

G1 X-78.640 Y23.883 E0.0296
G1 E-0.9000 F3000       <================================ LINE ONE
G1 X-78.160 Y23.903 F4200
G1 E0.9500 F3000    <================================== LINE TWO
G1 X-78.160 Y-25.284 E2.9447 F1800

Note that both line 1 and line 2 have the same speed.........as does every pair afterwards.

This is exactly the same in my own gcode...but speeds are slightly different, of course.

I see no reason to feed the filament on that one occasion at a slower speed....and it must be this that is causing the reported "lag". Perhaps this is a bug!!