Model Rejected.....Again

So my 3D model was rejected for printing again, this time down to the walls being to thin. I did expect this so it wasn't a massive surprise. Shapeways told me in another email why the model was rejected and highlighted one specific part of the model that was too thin, however its not very clear, even with a screen shot, which exact part is too thin. Also I have realised that when checking a model they reject it straight after finding one issue (so they don't list all the problems with a model, just the 1st one they come across), and I knew there was going to be more than one part that was causing a problem.

So to avoid a very lengthly process of fixing one bit just to have it rejected due to another (which could have gone on for ages) I sent them an email trying to clarify a few bits I was unsure about.

Here is a copy of the email I sent to their service department who are meant to help with fixing models for print. ---------------------------------------------------------------------------------------------------------------------------

"I'd like to clarify a few things if possible about my model to try help me update it and get it suitable for printing.

Firstly I am unclear as to what 'wall thickness' is referring to, compared to things such as detailing etc. I understand that their are sections of my model, such as the part you highlighted which are too thin, but for parts such as the spikes I'm not sure how the thickness is affected or how to fix the problem.

I am aware I have several parts on the model, mainly fine details, which are bellow the thickness/size required to print, this is down to poor design on my part as I didn't know there was a minimum thickness limit when making the model. Now the model is finished and the geometry is quite bad (thanks to zbrush decimating) I'm finding it difficult to work with the model and scale any bits very easily.

I have enclosed a picture of my model, highlighting a few more areas where I know the wall thickness is too low (measurements are circled in red), put I am unsure what to do in order to fix them all. Small parts, such as the little spikes on the armour (bottom right picture) could be removed completely and I could put those in myself manually later. Other parts such as the bigger spikes on the shoulder pad are a suitable thickness at the base of the spike and then taper until they are well bellow the required limits. This is a similar problem to the highlighted spikes on the metal face/jaw plate, which is where I believe you originally highlighted an error. Depending on which dimension you're measuring in, certain little features are either within or bellow the required 0.8mm.

In order for the model to be printable does every single aspect/detail need to be above 0.8mm (apart from surface detailing), including spikes etc. So for example do the spikes need to be made in such a way that even at their tip they still measure at least 0.8mm. Also are there any sections on the model (such as in the Ork's mouth) where detailing such as the teeth are Ok, even though they are less than the required thickness.

The most obvious solution would be to rescale the model until it is big enough that all parts are thick enough, but upon attempting this I found the cost of printed escalated too much for me to afford.

I'm a university student working on this model as part of my Final Major Project, this is actually just a test model made to help me grasp 3D printing. I am planning to get a further 3 or more models printed with yourselves of a similar size. Obviously I have a lot to accomplish in a limited time frame which means I don't have much more time to attempt fixing this model and no time left to redo it completely.

I'd appreciate any insight or help you could give me in getting this model ready for printing. 

Regards
Luke Evans"
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Their response was fairly generic and unfortunately didn't really answer any of the questions I had asked so I won't bother posting the reply I got here.

However one useful bit of information I got was about their 'Automatic thickness checker'. I knew this existed as it had given me warnings, but I didn't know the text was actually a button leading to an interactive screen would could be used to view the model showing the problem areas highlighted!
Here is a screenshot of the tool, clearly displaying some troublesome points, although it says 8 problem areas its inaccurate, there were lots....lots more. 8 seems to be the max it will tell you.

Using this tool I was able to clearly see the issues that would mean my model kept getting rejected until fixed.

And so began the extremely lengthy process of fixing, uploading, checking and then re-fixing my model. Uploading the model is the only real way I can see if I'm fixing the thickness issues and doing so takes ages.  On top of the time and stress inherently involved in this process it is worsened by the fact the required thickness seems to keep changing! Bits that i have fixed and then replicated to speed up the process are fine in one part and to thin on the other?! How does that work? It also seems that every time I upload the model some parts that were fine before are now to thin.... The messed up geometry could be the cause as verts are all over the place making faces erratic and oddly shaped which is sometimes picked up and flagged as making sections too thin.

The issues seem to be never ending and its approaching the point that I have spent more time fixing the model than it took me to make it, and fixing has meant I've had to alter bits drastically or in some cases completely remove parts of the model altogether, so I'm worried the model will end up nothing like my original sculpt!

I have put too much time into this model now to not get it printed so I'm going to continue fixing bits (removing if its easier) until it can be printed. Hopefully the next time I send it to print (today all being well) it will be the last and it will finally get the go ahead.