Successful 3D Printing - Part II - "Why did the print fail?"

See also earlier post: "Successful 3D Printing - Part I".

 If you are just starting out, I would first print one of the supplied models:
For example: XXXXXXX      (will upload examples soon).

"Checking the model if it is printable"
This should have been in "Successful 3D Printing - Part I".

After I printed a few of the models that came with the printer, I went online to download a bunch of other models, for example from Thingiverse or other sites.
But not everything is suited or designed well for FDM 3D printing and modification and support structures are needed.
Thankfully some users post pictures of their print of a certain model so you can see how it might come out, but often you only see the 3D CAD model.
The CubeX software has a very nice feature that lets you see and scroll thru the Build file to see the layer build / slicing.
If you have model files where you have not seen successful 3D prints, looking / scrolling thru the build file can give you a very good idea if your print should come out fine or might have some issues.

I wanted to print a nice spider model and found one on Grabcad.com.  http://grabcad.com/library/boristhespider
I downloaded it, build it in the software and started the print.  -  not so quick  !!  I watched the printing process for a few minutes and saw some problems.  - Abort !  Abort !!

Here is what I should have done before printing:

This is the model before building the print file:
Always keep in mind the printer prints layer by layer.
When looking at the model it is obvious that the part needs support structure since the spider body is in mid air. But you could think that the legs might be able to print without support, since the printer can gap small horizontal distances. So lets create the build file.

 

 

After you build the print file, first save the printfile (see File Management for file naming suggestion), then close the Model file. (You could also close the software and just open the Build file which does not contain the original model anymore). 

 

 

Now the Model file does not cover up the Print file and you see only the build file and, can toggle the print jets for Part, Support or Raft on / off.

 

 

When scrolling thru the build file with just the spider (jet 1) turned on, the problems become obviously. You can see that some of the spider legs are not touching the platform, the legs that are touching are so pointy an provide no support for an angled upward build. The thin sections in the legs tiny thin.

 

 

So in this case selecting "Raft" when building the part would not help for the legs were they start on the build platform. I opened the file in Cubify Invent and created a plane (blue plane, see below) at a level that intersects with all legs. Then I cut everything below that plane. That ensures all legs are touching the print platform and removes the pointy ends of the legs. Some models might not have a flat bottom surface, so you can either cut one like in this example or the part would need some other support structure.

 

 

 

Even now with the better bottom contact points for the legs, one should either use "helper disks" Helper disks zip file (see in earlier post about part lifting) and slide those under the spiderlegs to provide a larger contact and support area since the build of the legs is in an angle upwards and that little contact area of the legs only would not hold that angled leg once it is building up higher.

 Or you could design some pads in Cubify Invent underneath the legs.

 

 

These are just some examples how some of the issues could be addressed and solved.  In case of the thin sections in the legs, I don't have an easy solution to fix that, exept cutting the legs off and creating new ones with not as small sections.

 

 Where the legs bend around is another problem area. With the thin sections in those legs and the designed shape really cause problems. The printer can print over horizontal gaps, but only a small distance. In this case additional support where the legs curve around would be needed.

 

 

 

With the selected "support material" option, the body of the spider should print fine.

 

 

This all is just an example what to look for in a more challenging part for 3D printing.

In case of this spider model which looked great as just a 3D model but is not 3D printable without some rework and redesign. I would first look if I can find a better suited model for 3D printing or design my own spider model. 

 

So for most prints unless they are very simple and straight up, I scroll thru the build file and check for possible issues to avoid bad prints and disapointment hours later.