Start of print not extruding for several cm

[dennisjm]

I can't seem to get filament to extrude at the start of a print for several cm.

Anything that S3D generates before the actual model prints is fine, but when I go from start code to S3D code, I miss several cm of plastic.

I've tried various start gcode files. Some lay a line across the front of the plate. Others extrude some material off the side then go straight to the print. Regarless, when that is finished and the tool moves to the print start, it misses several cm of material before extruding. If the first thing to print is a raft then I miss a few cm of raft. If it's a skirt I miss a few cm of skirt. If it's the model itself I miss a few cm of model.

I've been working around this by simply always printing a 1 ring skirt and ignoring the few cm of skirt at the start that don't print. I'm trying to do dual prints now though and since both extruders don't print a skirt the extruder that didn't print ends up missing the material when it starts to print something important. Then I get off to a bad start right away.

Any suggestions?

[JohnB]

Check that you have "G92 E0" to zero the extruded length in your start gcode after the last "E" command.

[jimc]

well i cant comment on the dual extruder part of your question but the whole point of printing a skirt is to pressurize the nozzle before you start printing your model. its pretty normal for the start of your skirt line to be missing a little. if you are done your skirt though then jump to your model and you still get the problem yet again then what your have seems more of a mechanical issue.

[dennisjm]

Check that you have "G92 E0" to zero the extruded length in your start gcode after the last "E" command.

I'll give this a shot. there wasn't one.

[dennisjm]

well i cant comment on the dual extruder part of your question but the whole point of printing a skirt is to pressurize the nozzle before you start printing your model. its pretty normal for the start of your skirt line to be missing a little. if you are done your skirt though then jump to your model and you still get the problem yet again then what your have seems more of a mechanical issue.

The problem is in between the start code and the S3D generated code. If S3D prints a skirt the start of the skirt is missing but from skirt to model works fine. If I print an extrusion line at the end of the start gcode.. the start of that line is normally slightly messed up because it's the first thing to print but then when I jump to the skirt you'd expect it to be ready to print and working but the skirt is still missing a bit.

so like this:
print start -> extrude start line (normally missing a bit but prints as expected) -> gcode start end -> S3D start -> missing filament

[dennisjm]

Here is a snip of the generated gcode.

G0 Z0 (Position Height)
G92 E0 (Set E to 0)
G1 E6 F300 (Extrude 6mm of filament)
G92 E0 (Set E to 0 again)
G1 X-110 Y-65 F300; (Slow wipe)
G1 Z0.6; (Raise back up)
M73 P0 ;@body (notify GPX body has started)
; **** end of start.gcode ****
G1 E-1 F1800
; layer 1, Z = 0.16
M135 T0
; tool H0.2 W0.42
G0 X20.21 Y20.21 F7200
G0 Z0.16 F900
G1 E1 F540

So what I do is extrude a bit of filament then wait for the print to start. Much like extruding a line or whatever. But it seems no matter what type of start code I use, when I move to the model you can see that initial retraction and then extrude but for whatever reason I always miss the first cm or so of the extrusion, then it works great. This hasn't been a problem if I use a 1 layer skirt but now that I'm doing duel extrusions the 2nd material to print always has this issue. Very annoying.

[BaronWilliams]

...This hasn't been a problem if I use a 1 layer skirt but now that I'm doing duel extrusions the 2nd material to print always has this issue. Very annoying.

I have this same problem when the second extruder starts making my support. It always starts with a few cm missing plastic. There doesn't appear to be a way to solve this problem in Simplify3D. To solve this you need a "purge wall", and there is no such feature in Simplify3D.

The "purge wall" needs to be drawn every time you switch heads during dual extrusion. Even when using just 1 extruder for support and another for your actual model you still need this "purge wall" feature for both extruders.

Until they add the "purge wall" feature to Simplify3D we need to all use another software package for dual extrusion. Simplify3D doesn't really support dual extrusion properly. It lacks "purge wall" features, and the tool change script isn't designed correctly so you can't make your own "purge wall". It tried it. It's impossible.

[Sean]

+1

I am having the same problem.This seems to be especially troublesome when using PVA as the support material on my Leapfrog Creatr. I (we) really need a way to purge my second nozzle. There has to be a way to print the first layer of build material, have the head step off the part, lay down some support material, then come back to the part to lay down the first support layer. It would be awesome if it just laid down another skirt perimeter or two immediately before doing the first support layer.

[BaronWilliams]

Having both the 1st and 2nd extruder print a separate skirt would work well IF the skirt could be set to rise automatically to the last layer printed by that head. The skirt performs the same function as a "purge wall", except that the "purge wall" rises to the level of the print object, while the skirt needs to be specified in layer height.

Wether Simplify3D modifies the skirt function to work for both heads and includes an option to print as many layers as your printed object is high, or Simplify3D adds the ability to have a normal "purge wall", engineering wise, both probably amount to a similar level of coding.

I don't care how Simplify3D manages to solve this. I just want this solved. Its crucial for large dual head prints where each head sits idle for extended periods of time.

[Sean]

It would seem to me that it would only take a few lines of code. All of the prompts and controls are in the GUI already. The software is already generating the skirt geometry. It just needs to apply it to both extruders with an offset. This is how it should work (similar to Repetier):

Edit Process Settings > Layer/Right Extruder > [check] Include Skirt/Brim > Set Distance > Select Left Extruder > [check] Include Skirt/Brim > Set some different distance (S3D should know this from the right extruder settings)

You can also select how many layers and perimeters as done now. Then there needs to be a good way to save these settings that don't require an export and import (entirely separate problem).