Bridge Settings

I've been having a problem with bridge settings. From my testing it looks like verstion 44 was the last version that changing bridge settings actually made changes to the Gcode. I haven't found any topics about it here, maybe I'm searching in the wrong place.

I haven't been printing in a few months so I may just be behind on versions or something.

Does anyone know if the bridge settings have been fixed or maybe I just don't have something set right in the later versions of skeinforge.

I don't know as I have never used them. Are they supposed to just affect affect the floating bit of the bridge or the whole of the layer with the bridges in it?

It has never really made sense to me why you would want to deviate from the normal settings?

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[www.hydraraptor.blogspot.com]

As I understand it, the bridge setting allow you to change the speed of the print head and adjust the flow on the layers where the bridge starts. The first layer that spans a gap. If I remember correctly, it reverts back to normal settings after a layer or 2. It helps to eliminate some of the sagging you sometimes get with a big gap.

But if you change the flow from what it should be then the layer will be wrong, presumably too little plastic and so weak. So all you can do is speed up the print head, but if it works at that speed why not always have it that fast?

To get good bridging W/T needs to be small because it becomes 1 when extruding into mid air as the filament become cylindrical. The larger W/T is the bigger the gaps you get between bridge strands.

To make sure it is tight and doesn't sag you make the filament cross section slightly smaller than the die swell cross section.

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[www.hydraraptor.blogspot.com]

Since I'm not an engineer, I'm not sure I followed what you are expaining. My background is in programming. Let me see if I understand this.

You are saying that you don't want much difference between the width and height of the extusion to be very different, just a bit squished, so that there is no dramatic difference between a supported layer and extuding into air. Is that correct?

I assume the it is the filament cross section after extrusion, What is the die swell cross section?

bbriggstkd Wrote:
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> You are saying that you don't want much difference
> between the width and height of the extusion to be
> very different, just a bit squished, so that there
> is no dramatic difference between a supported
> layer and extuding into air. Is that correct?

Yes the bigger W/T is the more squashed the filament is, so when it is no longer squashed over a bridge it has big gaps between the cylindrical threads. W/T can't be too small though as you then get weak interlayer bonds.

>
> I assume the it is the filament cross section
> after extrusion, What is the die swell cross
> section?

The die swell cross section is the area of the cylindrical filament you get extruding into mid air, with no tension stretching it. When you extrude filament with a smaller cross section it means you are stretching it length ways and that defines how much tension it has.

This video shows a void spanned with no special bridge settings. In fact I don't think SF would class it as a bridge. [hydraraptor.blogspot.co.uk]

That was done with W/T = 1.5 and the cross section a little smaller than the die swell. It pulls reasonably tight, but you get gaps between the filaments. I don't see how that can be fixed without support material. You can't increase the flow rate to make them touch because it would then be slack and droop. If you extrude them closer together then the rest of the layer will be weak. This is why I have never understood the point having separate settings for bridges.

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[www.hydraraptor.blogspot.com]