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Bridge perimeters not anchored properly #2258
1.2.0-exp trying to print 50mm Bridge Torture Test from Thingiverse:
Unlike in 0.9.9, Slic3r correctly detects the perimeters that are part of the bridge, and uses the correct speed. But there is a problem in the way that they anchor.
The inner part of the bridge prints as parallel tool-paths running the full length of the bridge, from about the middle of one post to the middle of the other post. This gives them plenty of overlap with the post, so as to stick to it and maintain the tension. I can get this to print pretty much horizontally without sagging.
But the first two tool-paths, which I'm guessing count as perimeters because they print on either side of the others, and just before the others (which I assume are treated as infill), they don't overlap with the posts at all. I'm guessing they start right on one corner, and run to the other corner. With slight errors in starting and stopping extrusion, they seem to always sag very badly; they're not stuck down.
I'm attaching the g-code. In the tool-path preview within Slic3r, the perimeters go all the way around, but I expect they are output broken into bridge parts and non-bridge parts, which occur not in sequence. I would be happy for the speed to change abruptly between the two, if it extruded as one continuous movement, but that isn't what happens, so it collapses.
I think this is a bug, but if not, then it's an urgent feature request. I have bridges 99% perfectly horizontal, but the perimeters are stuffed with no hope of simply changing parameters to fix them.
I actually don't know how to attach g-code.. what an awful issue tracker this is :/ I'm putting it aside, ask me for an email if you need it. Hopefully this is easy to reproduce. Here is the start and the end of the g-code, so you can read off the settings:
; generated by Slic3r 1.2.0 on 2014-09-04 at 00:46:15
; external perimeters extrusion width = 0.50mm
; avoid_crossing_perimeters = 0
Hi, Im new to 3D but I have the same issue with my Ormerod printer. Putting up a digital microscope I observe that the printhead is just running back and fourth between pillars and the extrusion just falls down without binding to the pillars. My test object is simply to 2mm rectangular pillars with 10mm spacing and a 2mm rectangular overhang.