Bridge Feedrate Multiplier

Hey all!

I'm trying to tune my reprap and i'm having problems with bridges and overhangs. see (note first image show the part upside down so you can see the overhang issues):




I read in several calibration posts that i should be increasing my Bridge Feedrate Multiplier by 0.1 increments until i get bridging correct (i don't think that actually fixes overhangs though). And i can't seem to find that in Slic3r. I found something that i thought was close in the advanced, called Acceleration Control > Bridge, and i put it at 1.1 (they all started at 0, but if i left it like that, i got an error, so i assumed they should be at 1):



however, that makes a _really_ strange acceleration during printing.

questions:

1. what is the default value of these supposed to be? if i change back to simple mode in here, they go away altogheter
2. how do i fix my overhangs?

With what material are you printing? PLA? Try using a fan. Bridging is a point of weaknes with this printing technology so you will always have gaps between threads on the first layer of a bridge but the layers get better when printed on top of the bridging layer.

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Using ABSPrusa Mendel Zaphod with Pronterface and slic3r 1.3.0. Printing well with 3mm PLA and ABS through 2 x J Head Mk IV b and Wade Geared Exruders. Controlled using RAMPS1.4 board running Marlin_v1.1.9

Cool, i'll try that. yup, PLA.

For the topmost image, the problem looks like excessive speed during overhangs. Try slowing down bridges and perimeters. For my experience with ABS, they need to be in the 5 to 20 mm/s range, but I do not know for PLA. Leave acceleration control alone, its use is to avoid sharp acceleration. Put it back to zero (that is, let Slic3r decide). The gaps on the first bridge layer are a must, or new strands will stick to the older ones and drag them around making a mess.