collision problem

hi all,
have had this problem a couple of times now - but need to work out a solution now.
in the attached part the plastic on the overhang dries in such a away that each layer sticks or curls up a bit.
when the nozzle zooms across after drawing the opposite sides perim to do the fill it hits the curled up edge and whacks the x carriage
out of line. part ends up having a shift in it.
current plan is to slow travel speed from 130 to 30 to hopefully melt my way thru any upstanding plastic.
any other ideas?
regards,
roger.

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Prusa 'Explorer' (3dStuffMaker), GEN6, J-head Mk III-B, Bowden Extruder, Marlin 1.0.0 RC2, Repitier-Host V0.84 and Slic3r 0.9.8, PLA. Live at Victoria, Australia.

Lower your z height by 0.1mm first layer will stick a lot better. There are also other shortcuts you can try also. enable brim which roots the outside of your objects down with a thin outer layer as wide as you want specified, or you could use skirt, it builds up a single wall outside object. Typically around 5mm away from outer perimeter of object, and you can have it up to the height of your object. The theory is that it prevents rapid cooling of plastic.

hi james - the 'hit' occurs high up say layer 100 - it doesn't knock the part off the plate - is still stuck on ok
it seems to hit the lip of the overhang and then some how get out of whack - may a slip on the belts.
will attach a picture tonight.
roger.
ps. I bullclip the apart down on the 1mm thick tabs shown. if i phsically hold the part down it will not warp. no heat bed.

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Prusa 'Explorer' (3dStuffMaker), GEN6, J-head Mk III-B, Bowden Extruder, Marlin 1.0.0 RC2, Repitier-Host V0.84 and Slic3r 0.9.8, PLA. Live at Victoria, Australia.

A picture would help. Perhaps too much material is being laid down. This happens a lot in cool operation where the extruder slows down enough to ooze and build up plastic. A feature you can start trying is in retraction. There is a z height lift. I sometimes use 0.6 lift to avoid collisions.

You're not alone with this problem, it seems to come up every couple of weeks.
Your solution may or may not lie in one of these threads:

[forums.reprap.org]

[forums.reprap.org]

[forums.reprap.org]

[forums.reprap.org]

[forums.reprap.org]

If its in the travel that you are hitting try a bit of lift in the retraction settings if you are not already, maybe layer height or a little more.

interesting reading tsb4k - thanks for putting that together.
normally overhangs are not a problem but this part is 200mm wide and the overhangs are at each end.
the head gets a real run up zooming from side to side and whacks into the very slight upturn on the overhang.
have tried adding some 'fake' walls inbetween the sides (.4 thk) but it likes to print the perim and them zoom back to the fill.
i use a big fan now , just a house hold fan - maybe should be blowing down onto the part instead of from the side.
will try printing very slow esp the travel speed and see how i go - instead of 6 hrs will be 8 or 9. but like others have said normal buggers up at the 5hr point oh well
the z height lift thing that james mentioned sounds interesting too - not sure where that option is???
thanks,
roger.

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Prusa 'Explorer' (3dStuffMaker), GEN6, J-head Mk III-B, Bowden Extruder, Marlin 1.0.0 RC2, Repitier-Host V0.84 and Slic3r 0.9.8, PLA. Live at Victoria, Australia.

As highlighted use the z lift, it lifts the head between travel moves to avoid oozing across perimeters. It should solve your problem as long as it only happens on travel moves.

You should perhaps check your extrusion steps or print temperature though, you may well be over extruding or printing too hot or not adequately cooling (printing too fast or features that are small?). You shouldn't really get curling across 100mm.

hi all
had success last night after slowing down the travel speed to 30 instead 130. moved the fan position as well but don't think it was that.
have attached the photo of the good print and bad one. the bad one has been 'hit' several times and the x carriage must have slipped some each time. once it got past the overhang part it printed straight up as normal again. i need to print another one tonight (the other symmetrical half) so will see if it was just a fluke or not
roger.
sorry for the poor quality photos

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Prusa 'Explorer' (3dStuffMaker), GEN6, J-head Mk III-B, Bowden Extruder, Marlin 1.0.0 RC2, Repitier-Host V0.84 and Slic3r 0.9.8, PLA. Live at Victoria, Australia.

If you could just angle the inside of that piece all those strings would disappear. Looks like you fixed your main issue though.