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Is there anything I can do to improve the bottom side of surfaces that are printed on support?

I always try to rotate the model so that surfaces that need to look nice are on the sides or top, and, if possible I divide the model into smaller parts to minimize the amount of support.

But sometimes there is an object that has an irregular shape that need support no matter how I rotate it and can't be broken down into smaller objects with no support.

And then, after removing the support I get a very ugly ridged face that takes forever to sand.

To clarify, I'm not asking about making supports easier to remove, I don't have a problem with this, I'm talking about making the surface that touched the support better looking after removing the support.

Is there anything I can do to improve the look of the face that is printed on supports?

I'm using Cura to do the slicing and printing, I'm using the "lines" support type, my printer is the Robo3D R1+

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  • $\begingroup$ I think in theory if the orientation of the support "lines" would be perpendicular to the outher shell lines they would be easier to separate. $\endgroup$ – Leo Ervin Feb 7 '16 at 15:59
  • $\begingroup$ @LeoErvin - I don't have a problem separating the support, only that the face that is built on top of support looks horrible. I've edited the question to clarify. $\endgroup$ – Nir Feb 7 '16 at 16:09
  • $\begingroup$ Could you include a picture of what it looks like so it would be easier to diagnose? $\endgroup$ – Eric Johnson Feb 7 '16 at 17:55
  • $\begingroup$ @Nir I know what you meant. The point I was making is if it is easier to separate, it means they weren't merged too much to begin with, so there wouldn't be any merged (common) plastic parts (bulges) left after you remove the support that you then need to sand down. If the lines of the support were layed down perpendicular to the lines of the print, I believe that would help the above. Does that make sense? $\endgroup$ – Leo Ervin Feb 7 '16 at 18:39
  • $\begingroup$ @EricJohnson - I spent hours sanding the part and didn't take pictures before sanding, I will take a picture the next time $\endgroup$ – Nir Feb 7 '16 at 20:52
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The basic answer to your question is to create better bridging or overhangs on your machine. Bridging is when you are printing between two solid pieces (like a bridge). Overhangs occur when printing off of a single solid piece and coming back. Most slicing engines allow extra settings for speed, fan power, etc for these parameters, just refer to this terminology.

A very common and simple solution in getting features to 3D print properly is to just slow down! If you're not a in a rush to get the part done, you bring down all of the feedrates in your slicing engine. MakerWare has mine at 90/150 mm/s for print and rapid. Typically I'll bring that down to about 50/90. My reasoning is the more time you give the plastic to cool, both while and after printing the layer, the more rigid that layer will be for the next one. When briding or overhanging, there will typically be a sagged area in the print. You can minimize this by providing the plastic more time to cool. Also keep in mind that printing on supports is still technically bridging (printing between two solid pieces).

Another thing to keep in mind is adhesion from one layer to the next matter just as much between the current layer and the previous as the current strand to the one next to it. So, in some cases, increasing your shell could possibly make it easier for the infill/roof/floor strands.

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  • $\begingroup$ On the other hand, move the hotend too slow and the hotend will have more time to heat/melt the plastic that it is close to. Even if you use fans around the hotend. $\endgroup$ – Leo Ervin Feb 7 '16 at 18:41
  • $\begingroup$ @LeoErvin that depends on the material. A material such as ABS would probably benefit from having the hotend nearby as ABS needs more of a gradual cooling. While you wouldn't want to get to the point of melting previous layers, having a higher ambient temperature in your build area can help ensure the structural integrity of your part once it finally cools. $\endgroup$ – tbm0115 Feb 7 '16 at 18:47

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