[FIXED ] Ooze shield / prime tower print after layer

[bjarchi]

When printing dual extrusion, the ooze shield seems to be very helpful... and you need either that or a prime tower to make sure the extruders are primed.

However the gcode generated by simplify 3d does not have the ooze shield (or prime tower, for that matter) print before the layer.

Expected behavior: Ooze shield should print before any of the actual model features in each layer, at least once, so that it fulfills its purpose of wiping ooze off of the idle nozzle while printing. IMO prime tower, if chosen, should also print a layer before the first layer of print to make sure the chosen extruder is primed and ready to go.

Observed behavior: When printing with ooze shield or prime tower enabled, the shield/tower is only printed at the first tool change, or AFTER the first layer.

This behavior seems particularly bad when using the ooze shield because of two things:
1. Shield does not protect first layer at all, allowing any ooze on idle nozzle to be wiped on edge of print and potentially cause things to fail downstream
2. For the same reason the shield is frequently 1 layer shorter than the model outline and features being printed - again leading to it not serving its purpose and having idle nozzle ooze be wiped on the print edge instead of the shield.

I suspect it is the intended behavior - it's certainly what the gcode says - but it doesn't make sense to me. The only mitigation I see is to print a skirt as well as the ooze shield - but this only helps with the first layer problem, and it it raises the possibility of the skirt lifting and causing print failure (that is, another potential point of first layer failure).

Thoughts?

[madmat_tco]

I m having the same issue. Ooze shield and prime tower only print after the layer. Causes issues when printing with dual extruders.

[utahbmxer]

I would like to see this addressed as well. I noticed that when I print with several skirt outlines and a prime tower the following seems to happen.

1. First outline with T0 is laid down.
2. Prime tower with T1 is performed, followed by the outline.
3. Start on second outline, both tools.
4. Third outline, both tools
5. First layer.

The issue I have is that the fist layer of the prime tower has poor adhesion. I even extrude both nozzles and then immediately start the print, picking away any ooze with tweezers as the printer is homing.

I would like to see all the skirts laid down, then the prime tower. As it is now, the prime tower has poor adhesion and I worry that it's going to pop off during the job.

[Aha]

Anyone find a fix for this? This is basically invalidating the point of an ooze shield! (I'm noticing this and not finding a fix).

Also egregious: if you print a solid base of one color, it will only print ooze shield every other layer, right over open air, adhesion by luck!

Tried replacing with skirt/brim the first few layers but having trouble overall with it still.

[b-morgan]

I am also having problems because of the order of printer for the skirt/brim, ooze shield, and prime tower. This combined with a lack of a first retraction of the inactive nozzle make dual extrusion printing with S3D very difficult. I believe the following fixes will solve the majority of the problems.

1. Provide documentation on the assumptions made by S3D about the position of the filament in each extruder (I believe this state should be all extruders are primed and ready).

2. When there are multiple extruders, S3D picks an active extruder and should then retract all inactive extruders. If this needs to be done in the tool change script, then the first execution of this script should have the variables defined and perhaps a new variable, FIRSTTIME should be provided.

3. If the skirt / brim has All Extruders selected, then print the skirt / brim with all extruders before moving on to the next additional feature.

4. If a prime tower is selected print it next.

5. If an ooze shield is selected print it next.

6. Print the part with the active extruder and if a prime tower or an ooze shield is selected, move the active nozzle to the next additional feature before executing a tool change (or the tool change script). If this needs to be done in the tool change script, document and/or provide access to the "next" location.

The printing loop should be steps 4,5,6, 4,5,6, ...

There are numerous topics in this forum about dual extrusion, standby temperatures, and tool change scripts. I believe that if the developers provided some guidance / documentation regarding the S3D internal processes / state around these issues, then users of dual extrusion with S3D would benefit and this community could better help those that do have issues.

[S3D-Jake]

I’m happy to state that this issue should be resolved now in the latest 4.1.0 release. Our team successfully tested tons of factory files examining how this should work moving forward. The ooze shield and prime pillar should always print before the layer now. This was just one of many improvements to the software. All of which are detailed on our Release Notes page.

Thank you for your help reporting this issue!