Some items just don’t print at all

Hi. I have a Dental Laboratory. I am trying to print my models with removable teeth as designed by the 3 shape scanner. Everything scans and looks fine but certain items just don’t print at all. After the last attempt I just stopped because nothing was working at all. So if I print a model with removable tooth the model prints fine but not the tooth and visa versa.all files are from the same scan. I then find the file that didn’t print and try it on its own but nothing. The form labs works as if it is printing but it actually never gets started.

it won’t print a separate part In Place… but it sounds to me like your software is not creating the tooth as a SOLID model.

a model might LOOK fine onscreen… but open manifold surfaces can display like a solid but not actually be a solid.

So first of all, check to see if the tooth model is a solid- or try to export the model as STL which either your software or Preform can sometimes convert into solid on export or import.

Thanks so much for the advice. I am really good at teeth but I don’t really quite understand what you are saying. The 4 parts were all scanned together. I then imported an STL file off Google. It was 2 parts. It printed 1 and not the other. So again I found the file that didnt print first time and I tried it separately but still no luck. Can you please explain what I need to check from your advice.

a 3D printer has to be able to tell what part of the build volume is solid- and what part is air.

But it only has math to do it with, So the one characteristic that can be said to define a solid object, mathematically, is that is has only ONE side… its OUTSIDE.

But 3D modeling apps do not have to model objects as solids… instead- they can also represent forms as SURFACES.

Try to picture the difference between a balloon, and a rock the same shape as the balloon.
The balloon is a thin surface with nothing inside… and that is how modeling apps represent surfaces… even the surface of a solid object is actual only the exterior of the object.

with a balloon, it holds air in because there is no hole between the outside of its surface… and its inside volume.

If a printer can determine that a model surface represents a contiguous surface with no holes into the interior volume- then it can determine that filling that interior volume with resin will form a proper solid. That is- the surface delineates the separation boundary between the Object- and the empty space around the object.

Now- try to imagine a HALF a balloon. Still in the shape of a balloon, but not actually able to hold any air inside, because its now just two sides of a hemispherical surface.

Mathematically, any model with even the smallest hole in it, is still just like that Half balloon… just a curved surface- that does NOT separate an interior volume from and exterior volume.

Looked at from one side- the half balloon looks like it has form… but its surface is infinitely thin and does not fully enclose a separate volume from an exterior space.

So- your scanner can scan the outside of something like a tooth, but even the slightest missing piece of the surface will result in a hole to the ‘inside’ that makes that tooth look like half a balloon to the printer.

It can RENDER on screen just fine, because light can bounce off a surface whether it is solid or not. And in animation or CGI- you don’t really CARE if the model is solid or not. you only need it to render- and so LOTS of software simply does not even Try to maintain the solidity of models.

Your software or scan resulted in ONE part of the model being a qualifed solid. But the tooth part in NOT being a solid and so, unprintable,

You can look to see if your modeling app has an Object Doctor or similar feature for fixing bad geometry in a model and see if it can fix the model that won’t print.

But Preform simply doesn’t have the capability to treat SOME models entirely differently than others. If it will print one model- but not the other, then the Other model is simply not valid solid geometry.
Preform uses the same OpenGL technology to RENDER the model it imports… thus, just like a CGI app- it can SHOW you a surface that is not a solid… but when it doesn’t print at all, that means the model is most probably not a solid.

That’s a great explanation thanks.
So my scan may be fawlty?
On Friday I downloaded a file off a 3d site and tried to print it and the same thing happened. Could it be my settings before I send it to the printer?

Also. I am a complete novice at this but I want to learn. What would be the best software for a complete novice to start creating files to print

It is hard to say what caused it.

Generally speaking, the vast majority of folks posting models online have no real comprehension of Topology and how it relates to solidity.

A huge percentage of models you can download are designed By animators For animators and thus never were even intended to be solid models.

Often- a file you buy online will be available in several different formats… usually, the STL format- if offered- is the most likely to be a solid… even though an inexpert modeler can still manage to make an STL that is not solid… it at least eliminates the kind of solidity issues that tend to plague models produced in 4 point geometry.

Myself- I use the best voxel based modeling software out there for solid modeling- Freeform. But even its entry level version Sculpt is pretty expensive. It is able to solve most any problem of solidity on import and is staggeringly easy to learn and use.

On the less costly side- MeshMixer is widely well regarded as a way of importing files and fixing issues of solidity.

Programs like Rhino, 3D Studiomax, Form-Z, and Maya- are more focused on rendering than on actual solid modeling. While they CAN produce solid models, they each have a hundred ways in which a newbie user can accidentally lose solidity in their model.

however, most pro level modeling apps have some form of Object Doctor that can try and repair issues that stem from bad topology.
Of course- whether they can fix a file or not has a lot to do with just how spectacularly incompetent the person who modeled the original file was.

It sounds like your really good at this and I really appreciate your giving such detailed advice. Because I am such a novice I am unsure where to go from here. I thought the STL files I downloaded off Google would be ok. I am not sure which site but it was one of the sites that only has STL models to either buy the final print or print them yourself. You have been great but now I am unsure what to do next. I would of thought my scanner. Which cost $40,000 would give me a solid model. That was the whole reason for getting this. To help me at work.

it will- but you have to provide it with good files.

Try MeshMixer- you can download it for free.

but definitely read the manual and/or try and get yourself some background in 3D modeling and how it works.

If you can afford a copy of 3D system’s Sculpt software… that is probably the easiest and most powerful modeling app you could want… you can learn how to use it in a couple of weeks, and the vast majority of problems with files you buy online will be fixed simply by importing it into Sculpt.

This topic was automatically closed 14 days after the last reply. New replies are no longer allowed.