Model is solidified but appears full during 3D print I'm Eric and I've just started my journey with blender. The plan is to provide 3D pictures for our customers.

Everything seemed fine (after a number of evenings spent in company of Netflix, Blender &amp; Blender Video) but now we are a bit stuck.

We created a model that is some 12x7x13cm, hollowed, solidified to 2mm &amp; painted on vertices as you can see on this screenshot:


Nevertheless, once we export it to 3D Print to use on our plaster printer Project 660 Pro - it seem full inside. Here is the screenshot for comparison of our model vs what is ok with some proper model in 3D - where it appears ok (you can even see a hole in the head as it is not yet corrected):


But in 2D slice - the one we need seems to be filled. Unfortunately - the same story appears when calculating volume for printing (increasing cost some 4-fold &amp; giving customer different feel):


Just to mention - model also appears ok in meshmixer (it is hollowed &amp; solidified) and we tried multiple type formats (wrl &amp; ply) but none worked correctly.

Here I need to ask for your help - what could be the matter here &amp; the method to resolve it please?
As they say - there are many ways to skin a cat - so perhaps there is some manner to get just the outer shell of original model, copy it and then proceed please?

Thanks,
Eric
When using a 3D printer, which has hollows, its like trying to print a bridge with the tunnel part underneath. The printer cannot do this not without supports being printed too as the maximum angle support is around 45 degrees. The way to over come this is to tilt your model so that printer can put layers on top of one another. This might not be your problem of course but it is worth considering.

The other way is to print the support using a material that you can wash out afterwards. It would mean changing the material over once the supports are printed.

If you model's outside angles (travelling upwards from the base)are all within the 45 degrees then it should be ok. But I suspect that the printer might be trying to put down layers where there is nothing underneath it, so it prints the whole model filled in. I've had this problem myself. Had to think outside the box for this one :)