Posts: 14
Joined: Tue Jul 03, 2018 11:25 am

Dual extruder, collisions between support and ooze shield

Sun Mar 10, 2019 10:47 am

I am printing PLA on T0 and PVA on T1. One each layer, it lays down the PLA main structure before the PVA supports. There are many situations where I see the PVA line crossing a previously-deposited PLA line on the same layer, or even crossing other PVA lines on the same layer. I don't see any interruption in the later line....the Gcode previewer shows it as a single line laid right across the pre-existing line. I would think that would be undesirable, and lead to a bump in the second line, and perhaps some disruption of the first line.

For example, in the attached Gcode, line 548 is PLA at 0.18mm (first layer). Line 1585 is PVA crossing this also at 0.18mm. The Gcode viewer plots it as an intersection between the lines. In this case, the PLA is part of the ooze shield, and the PVA support is drawn with large "extra inflation distance" to show this problem. But I run into this problem unintentionally also, for example if using Waterfall ooze shield on a complex shape. Note that in this example the PVA support (later line) is crossing both the PLA and the PVA of the ooze shield (laid down earlier).

I can avoid this by making the ooze shield far away (for example Waterfall), and/or I can make sure "extra inflation distance" is zero, so that the support structure is smaller. Generally there is a way to avoid this by adjusting things. But I am unsure which of the following is true:

1. This is an actual bug (?)
2. This is just how it works, and I am supposed to preview the Gcode, look for such situations, and avoid them by adjusting positions of support vs main lines. (?)
3. This is just how it works, and it doesn't cause any physical problem, so I should just ignore it (?)
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Posts: 444
Joined: Thu Aug 30, 2018 1:23 pm

Re: Dual extruder, collisions between support and ooze shield

Wed Mar 13, 2019 9:34 am

I took a look at your gcode and at first glance it looks like you might have some conflicting settings with Extra Inflation Distance and your Ooze Shield Offset. It would help to see a Factory File though. Can you please post one when you're able?

Posts: 14
Joined: Tue Jul 03, 2018 11:25 am

Re: Dual extruder, collisions between support and ooze shield

Wed Mar 13, 2019 11:12 am

Yes, I do....for that Gcode I set the Extra Inflation Distance to a large number and the ooze shield "Offset from Part" to a small number to show that it is possible for lines to conflict. One possible answer is that there is no automated check for this and I am just supposed to avoid this situation, and watch for it in the preview. I notice that it doesn't just happen when Extra Inflation Distance > Offset From Part. It can happen even when Extra Inflation Distance is quite a bit less than Offset from Part. But as far as I have seen, I can always reduce Extra Inflation Distance (for example to zero) or raise Offset from Part to avoid this. I just thought it odd that the program would ever draw intersecting lines. Note that even within the Gcode for a single extruder on one layer (the support extruder), it draws the support line across the ooze shield line. So my question remains,
1. Is this a bug?
2. Is this not actually a physical problem? I have printed several parts with such intersections, and they don't seem to fall apart (although I haven't done much testing).
3. Am I just supposed to manually / visually adjust these two parameters so I never cause this situation?

In other words, I think I can see what in the factory file is causing this - it is the relation between Extra Inflation Distance and Ooze Shield Offset From Part. My question is not that - my question is what, if anything, to do about it.

(Edited to fix a couple typos)

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