# 3D Design / 3D Scanning / 3D Modeling > 3D Printing Slicer Discussion >  Can't get this model to slice

## dwatrous

Hi,

I designed a model in blender and have tried many ways and two slicers to get it to print correctly on my ender 3. I have tried Cura 4.7.1 and Creality slicer 1.2.3. In both cases, there is a big hole in the top that I can't close, and it seems to be printing something solid in the middle.

I did try using the 3D print toolbox in blender to Make Manifold, which broke a few things that I can't see how to fix.

I'm going to keep trying things, but I wanted to see if anyone in this forum had some pointers. This is my first 3D printer and my 7th print, so I'm learning fast.

Thanks.

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## dwatrous

I found some great resources:https://i.materialise.com/blog/en/3d...th-blender/One thing I did  was to use the binary modifier to Union two parts that were CTRL + J joined in blender. What appeared to be a large hole in the top of the object was a rendering error in the creality slicer. I am printing now and the non manifold parts don't appear to affect the print.

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## curious aardvark

that's just a mess. 
Also would never print without supports in the centre.
oops, turn it upside down and if it were solid it should print without supports _ I think. 
It looks like the top part is being treated as solid, rather than a solid with parts removed. 

It does slice in simplify3d. But the whole top is solid and the threads do not show in the sliced version. 

Blender is definitely NOT recmmended for stl design. 
It does work - but easy it is not ! 

Have a look at tinkercad, fusion360 (free version) or openscad.

And 3d modelling for appearances, is a totally different animal from 3d  modelling for 3d printing. 
We only deal in solid shapes = most cad packages work in shells and voids.

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## dwatrous

After some additional work, I was able to get this to work for a print. Blender is great for modelling, but it can be a challenge to get a good STL. Thanks for your response.

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## jeffrey1gardner

Check flow rate and increase your extrusion multiplier. When the amount of filament that your 3D printer thinks is going to be extruded is actually less this results in gaps within your print.

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## curious aardvark

> Check flow rate and increase your extrusion multiplier. When the amount of filament that your 3D printer thinks is going to be extruded is actually less this results in gaps within your print.


well it looks like a spambot. 
See if it posts again :-)

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