First layer "weak" printing

[DrUsual]

I'm trying to print some two-color prints with my Dreamer and running into some issues that I didn't have with the same operation in the past. New objects, new .gcode files, so it's not necessarily something that's changed in the printer itself. An example object is a standard six-sided die; I create one STL of the die with holes for the numbers, and another STL of just the numbers. Put them together in Simplify3D, create a process for each extruder.

Neither extruder seems to flow quickly at the start of the print. The cube is 20mm, and if I do a skirt with 3 outlines, the PLA will *just* start flowing as it starts to outline the actual object -- the skirt never gets printed. With larger objects the filament starts to flow well into the skirt.

Same issue with the second extruder. The first layer lays down little or no PLA in whatever number is facedown on the print. It's not until the second layer that the PLA is really flowing, which means that face is very weakly inscribed.

Any thoughts on this? I know Simplify3D has a lot of settings for retraction, coasting, etc, but I don't know enough about them to know what might solve the problem.

[LambdaFF]

It might as well be just the degrading of the filament. Have you taken steps to protect it from humidity ? Is the extruder wheel skipping ? In S3D, what is your value for extrusion multiplier ? The coasting and wiping should not apply for the skirt.

Usually I prime the extruder before doing the G28 / G29 commands. So I don't have more than a couple cms missing in the first skirt outline. Have you tried that ? How long is your outline ?

Do you have the same situation if you switch back to single extrusion ?

[DrUsual]

Extruder wheel isn't skipping, and the extrusion multiplier is set at .9. (I'm just using the S3D defaults for many settings.) I don't know how to prime the extruder before the G28 command, though; any chance you could paste in an example of that? I'm also about to try just one of the two models with a single extruder and see if there's any difference in the performance.

Thanks!

[LambdaFF]

It depends on your machine but perhaps 0,9 as multiplier is not required ? Typically, mine is at 1... I'd advise you to check on that.

[curious aardvark]

what resolution are you printing at ?

Bear in mind that the volume of the nozzle heat chamber doesn't change. But the amout of plastic it extrudes for different resolutions does.

So a print at 0.3 mm will have plastic going down sooner than one for 0.1mm.

If you're printing the dice at a higher resolution. Then it would make sense.

what you can do is set the first layer to go down thicker than subsequent layers. There is a specific percentage setting for first layer thickness, saves you having to have 2 processes.

[Sebastian Finke]

I don't use S3D so maybe this won't help but Makerware has purge walls, do you have a similar feature?

[DrUsual]

So, I upgraded to S3D 3.0 yesterday, and finally started getting successful multi-color, two extruder prints again. Aardvark, I was using (and still am) the default settings in S3D regarding first layer -- 90% height, 125% width, and 35% print speed. (I do sometimes bump up the first layer print speed to 60%, though.) I've never changed the Primary Layer Height, which is set at .2mm, but I think that's the attribute you're referring to? It hadn't occurred to me to tweak that one before, but your explanation makes sense.

Sebastian Finke mentions the purge wall -- S3D 3.0 has that as an option, as well as a priming pillar. I've been using the purge wall and the dice have been turning out quite nicely. Unfortunately, it nearly doubles the print time, since the purge wall completely surrounds the object. I'm going to try switching to the priming pillar instead.

Version 3.0 also has a very cool dual extruder wizard. It seems to help avoid conflicting settings by configuring the processes separately, which was necessary prior to this version. Now common settings change in both processes, regardless of where you make the change. You can also preview the print with color coding of the active tool head, so you can see which extruder is laying down filament at which time...

[curious aardvark]

the setting I was referring to is the first layer height. It's a good way to adjust things without having to have a second process.

Also you really want first layer speed to be really slow. Mine is now set at 10% by default. yeah it can add tie to the print. But I get a helluva lot less failures.

Haven't tried dual extrusion yet - I like the idea of the priming pillar alot more than the purge wall. Makerware has that and it adds a lot of time and wasted filament to the prints.