Hello all,

Thank you for taking the time to read this and help.
I should say advanced printing ideas to me at least, these may be common for all of you.
I am new to 3d printing, but am experienced in traditional CnC (mills and lathes), SolidWorks, and Embedded Systems.

Here is the question, when performing what I would call advanced printing how do make the software do these things. I am used to solidcam where every toolpath is selected and chosen letting you decide what it is going to do. Neither the reprap software or repsnapper seem to give me any options or control to do this.

Take for example a hollow cube,
There seems to be two approaches to solving the problem of making the top without support.
1. Move the extruder very fast from one side to another, effectively stretching the plastic over it. Although this layer isn’t great it makes enough support for the next layer to be printed making the top.
2. Starting at one edge move the extruder slowly at just the right rate so that it sticks to the line next to it, hanging over open space.

How do you chose what method is used in the software? Or do you not get a choice. I am thinking I am not using the right software.
The first one seems easier but there are times when I can see needng the 2nd, for example a wing off of a box.

Thank you for your time and your help.

Option 2 is not a real option. (or at least I've never seen it done and don't see how it is plausible)

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www.Fablicator.com

Once an overhang is greater then 45 degrees and bridging is not possible, you need support.
Plastic wil not stick to plastic right next to it, or if you can get it to do it, I'd like to know how.

I think you would have to tilt the nozzle 90 degrees to extrude a layer onto the side of another. That would need a 5 axis machine and much more complex software and would have problems with tool collisions. The beauty of 3D printing is the software is much simpler than subtractive CNC and can make any shape if it has support material.

Edited 1 time(s). Last edit at 05/07/2012 03:01PM by nophead.

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[www.hydraraptor.blogspot.com]

HI all,

Ok since #2 isn't possible, at least currently. How do you do #1? Does the slicer do it automatically? Or do you have to tell it when to do it?

It just happens, no action necessary from the slicer since the plastic should always be stretched a little. Some slicers detect it and give the option to go faster I think. See this video from nearly four years ago: [www.youtube.com]

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[www.hydraraptor.blogspot.com]

Nophead,
In the video when it goes 2x, 4x is that just playback speed? I had imagined that the speed would be more critical. Or is it only the speed to extrusion rate that matters?

Thanks for all the help,

It is just playback speed.

I don't think the speed of bridging has a big effect. Faster extrusion causes more die swell so the filament tries to be fatter and shorter. Than means it is stretched more at high speed, so it will have some benefit but you can see in the video that it spans fine at the default speed.

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[www.hydraraptor.blogspot.com]

You can set a separate speed for bridging in both slic3r and skeinforge, but it's mostly a trial and error setting and depends on a lot of variables.

I use 40 mm/s with PLA at the moment, but I find it so much easier to do bridges and difficult parts when using a fan.

Also for point 2), the filament does stick ever so slightly to the side of a previous line. It's not enough to rely on bridges to do this, but it's enough that you want to print the perimeter outside last when you do large overhangs.

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-Nudel
Blog with RepRap Comic