Tuesday, 19 March 2013

Thin Wall Engineering and the problem with classic infill

The structural issue with infill is that this kind of support structure doesn't really do much and to it's full potential, here's why:

this is what infill currently looks like,

in the image below you can see the contact points between the two layers of infill,  as can be seen there isn't much linking the two layers, this essentially leaves you with towers of dotted links from the bottom of the print to the top,

 the result is a parallelogram type of effect, while the object will feel solid and behave in a fairly rigid fashion under compression when under a shear type of load its no where near as string as it could be, this however depends on the part too

 the solution to this problem is simple, like in a lot of inject molded  parts ribs are usually added to make the part stronger and to a very successful effect in our case where we have the luxury of being able to print the whole object including internal cavities , with the up comming version of slic3r we can do this:

because the internal ribs are solid walls as opposed to a 3d mesh you can get a stronger object, the main advantage however is that you can customize and reinforce specific parts of the object like holes with extra ribs to make specific parts of the object strong

the cylinder in the above photo is the most successful, it's just as rigid if not more rigid than if it was fully infilled,  currently however slic3r has no infill settings for this just the classics so it's up to the designer to draw everything, internally,

1 comment:

  1. I noticed this a while ago as well, I use regular infill when I need it to be above 50%, below that, I like to use the honey comb. One thing you have not considered though is that the plastic is essentially being smooshed when it comes out of the nozzle, so if your layer height is a out %50 of the nozzle diameter, you are basically printing about twice as wide, or something like that, then when it goes to do the infill, the "contacting point end up being smooshed, and the non contacting points assume a more cylindrical form which makes them taller, making them touch. basically imagine a straw being smooshed as the filament, when its smooshed its wider, when its not smooshed its taller and will fill the gap.