Printing issues at different speeds

Hi,

During solid fill layers, changing the speed has a strange effect: higher speeds seems to put more ABS than lower speeds. My 'normal' speed is 40mm/s. If I increase it to 60mm/s, I notice that the filament goes too far on the perimeter, and also put a kind of blob when reverting the direction. This leads to a higher layer at both ends. Decreasing the speed to 25mm/s gives me much better results.

What I don't undertsand is why I have more stuff at higher speeds? Or is it another problem? X axis inertia? Acceleration problems?

In fact, it should be the exact opposite effect, as I noticed that at higher extrusion speed, the filament starts to slip a little bit...

Any idea is welcome.

Thanks.

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Frédéric

In fact, dimensions increase a little bit with the speed... Don't understand why.

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Frédéric

What gcode generator are you using? Slic3r doesn't do that. With other generators, you have to adjust several parameters if you want to change the speed or layer height and still get proper prints.

The print head has to slow down before changing directions (acceleration)

The pressure in the print head does not change instantaneously, so if you slow down the print head the extruder will not slow down until a fraction of a second later.

As your print speed increases, the delay increases because there is higher pressure in the extrusion head.

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www.Fablicator.com

If you are using Skeinforge, you need to change both feed rate (speed the nozzle moves) and flow rate (speed of the extruder). They should be the same. If you only change one, you will end up with more or less material deposited overall. If your calibration is correct, having these 2 values the same will produce good quality prints.