Ok, let me introduce myself first 
My name is Baha Abunojaim, CTO and co-founder of Mixed Dimensions, the developers of MakePrintable, a service that will repair your model and turn it into a printable form taking in consideration the size of the print, soon the printer and material you are going to print with as well.
MakePrintable is a fully automated service that handles non-manifold, flipped faces, intersecting geometries, solidity issues, wall thickness and other common issues in 3D printing, it allow you to generate a reconstructed and fixed 3D model (STL or OBJ), a series of SVGs or GCode, you can also send your file directly to shapeways. There is also a punch of other functionalities like hollowing and auto generation of escape holes that will reduce the cost of your print! You can even reverse existing GCode files back into 3D models (still experimental).
We’ve also built a number of integrations including sketchup, thingiverse, DAZ, Blender, Box, Drive and still working on others to make it easy to take your file from an unprintable state to a printable state without wasting a lot of time modifying it for different print settings.
There is a number of scenarios you will find MakePrintable handy:
1- Your model is really complex and it will take a lot of time to modify into a 3D printable state.
2- You don’t know the requirements to make your model 3D printable for a specific print mechanism and material.
3- You have a deadline and limited time to fix your 3D model.
4- You are composing a scene with assets from the warehouse and not sure how the designs are made and want to print that scene but printing issues exists in it and you are finding hard time to solve it.
5- You have a large collection of files and you want to fix all of these files for 3D printing (think of a marketplace, an old collection, a library, thingiverse, etc…).
6- You designed your file with a specific wall thickness in mind for a specific scale\ material and then you decided to change that.
7- You want to lower the print cost thus hollowing your part.
8- You have a GCode file and you lost the original design and want to get the 3D model back.
9- You want to merge a number of complex models but boolean operations always fails to do it.
10-You want to slice your file faster through using a cloud.
11-You liked a design on a marketplace (let’s say Turbosquid or DAZ) and you want to get it printed.
These are some common use cases for MakePrintable and below is one of these cases:
Here is an example model as I promised, it is one that is available on sketchup warehouse and of the one and only optimus prime 
The original model contains so many boundaries, non-manifolds and intersecting geometries with wall thickness issues as well, here is how it looks in meshlab before fixing with MakePrintable 
Here is the output after running it with MakePrintable 
As you can see all issues got solved including wall thinkness issues and all what I had to do is few clicks
For me, I came from a gaming background and when designing for a game or visual representation then you usually try to eliminate as much un-needed polygons as possible, think of hair and cloths on a character for example, typically you try to avoid creating hidden geometry that is not visible to the screen but when it comes to 3D printing that is problematic and can cause your print to fail, it all depends on the design approach and the tools used but for us, we believe you should only focus on making a great design without bounding yourself to the limitations and constrains of 3D printing.
If you want to test it out then run the file through either one of the below links! it is FREE!
Website: https://makeprintable.com/
Sketchup extension: Extension | SketchUp Extension Warehouse
Would love to hear some feedback as we are still in BETA
