Porosity & Sturdiness & Smooth Surface Combined

[yesnlsy 0]

Hey everyone,

 

I am an Ultimaker 2+ user for about 8 months and I have had many successfull prints which are challenging for me. Nowadays I need to have a porous and smooth surface (as shown in the picture) and also I want the structure to be as strong as possible. Hope I can get this using PC or ABS as material, PLA is the last choice (I also think that Colorfabb xt-CF20 carbon fiber would fit requirements, I haven't tried but I will). I had an extended research on it and see that it can be achieved using extreme printers like costing hundreds of thousands of euros (Which I don't find right to share here any trademarks etc.). I really wonder if it is possible to create a surface like this on Ultimaker printers. Is there anyone tried something like this before?

[IRobertI 521]

What type of scale are we talking about here?

[yesnlsy 0]

Hey IRobertl,

 

You can assume that it is something like 200 x 200 x 50 which is quite suitable on the UM2+'s build plate.

[gr5 2,268]

No he wants to know how big these structures are.  Are they 1mm apart?   0.1mm apart?  That's a 10X difference and it matters.

 

Does it have to be porous such that gas or liquid passes easily through?  

 

Does it just have to be a rough surface such that paint or glue would stick well?

 

It sounds like you want a smooth surface as felt by fingers but rough surface on a smaller scale.  Is that right?

 

If so then maybe you would want a nozzle with a bump on the tip that can cut groves in the part as it prints.  UM2 and UM3 can swap nozzles (or cores) such that you could manufacture one with a needle or something sticking down.  You wouldn't want it sticking down more than .2mm (the typical height nozzle is off glass on bottom layer printing).

[yesnlsy 0]

Thank you for your answers guys but I still don't feel like satisfied. Let's try again.

Here what I want as sorted:

 

* It needs to be porous so that air can flow through the structure.

* The surface needs to be rough because of that sticking issues, and also smooth because of the quality of the part that I would like to obtain from the structure im gonna print.

* Whole structure needs to be as strong as possible because of the tough working conditions.

 

Im gonna try spaghetti infill by the way. 

 

Hope this clarifies everything.

 

Edited January 22, 2018 by yesnlsy

[gr5 2,268]

We still don't know the scale of the roughness.  How small do the holes have to be in diameter?  Can they be 3mm holes?  1mm holes?  0.1mm holes?  (UM definitely will have trouble going smaller than .1mm).  1mm holes is very doable.

[yesnlsy 0]

The CAD data is not designed with holes. But let's assume that 1mm holes are ok for me. What's next? How to programme it on CURA? Only decreasing the infill? Changing the shell thicknesses? Got so confused to combine all of these...

[gr5 2,268]

Well maybe you can set the top and bottom thickness to zero and set the infill pattern such that it has about 1mm holes.  Maybe around 80% infill - play with it.

 

This only works if it's okay to be porous vertically but not horizontally.  This is what people do when they make "molds" for cardboard packaging (start with wet cardboard pulp (or cut up newspapers) and put it on the surface, let it dry and voila.

 

Also what they do for vacuum form molding.

 

Alternatively maybe there is a way to set the flow rate to 50% JUST FOR THE TOP AND BOTTOM.  And just do 2 infill layers maybe (top/bottom thickness set to 2 layers).

 

Try those 2 ideas first.

 

If cura doesn't let you set flow for just top/bottom infill then you could do it by modifying the gcodes a bit - just insert the gcode that sets the flow to 50% or 100% in a few places in the code - 100% for shell bottom few layers and 50% for infill.  The gcode file is marked up where each layer starts/ends (plus you can look at the Z value in there to see the current printing height) and the gcode has comments showing where shell starts/ends and where infill starts/ends and so on.  You might only have to insert these 5 or 10 times.

 

If you end up creating tons of these all the time you could write a plugin that does this automatically.  This kind of post-processing plugin would be a perl script that locates all the top/bottom infill parts of the gcodes and inserts the flow gcode around that section.

 

OR you could do it all in CAD.  Tell the cad software to put thousands of holes through your part.  This is pretty easy to do in openSCAD.  Or you could take the STL file from your cad, pull it into openscad (very easy) and then subtract off thousands of thin cylinders and save it back out.  Also pretty easy to do in openSCAD.  I could write that for you for about $100 if you want.  Send me an stl and I'll send it back with holes and if you like it, pay me and I send you the openscad code and help you set up openscad.  I'd write it so you can easily change the hole spacing and the hole diameter.  But some of the holes would put cylindrical grooves in the edges so that would have to be acceptable to you.

[geert_2 558]

This sort of holes can easily be done in CAD: design one hole, and then repeat that in a pattern in both directions. This sift (for a laboratory sink) is ca. 50mm diameter. But it does not print easily: too much jumping and retracting. Making a solid plate and printing it with ca. 70% to 80% infill (try it) like gr5 says, would give much smaller holes, and will be quite strong, but it will have a *very high* resistance to airflow. So it all depends on the exact purpose. Maybe you would be better off printing a sturdy housing only, with big openings, and then put some standard proven air filter in it.