Hi danieljb,
You could force Simplify3D to make a complete solid infill at the point you need that extra strength.
There are 3 ways to do this.
METHOD 1
One infill option that can do this is "Include Solid Diaphragm Every X Layers". With that option you need to know the exact layer to make the solid infill. It's not that useful for what you need, but it can work. I repeats the solid infill even X layers. So if you specify 10, then every 10 layers will be solid.
METHOD 2
Make 2 processes. Make process 1 start at the bottom and go up until the height you want the extra solid infill for strength. Make process 2 identical to process 1 but make it start at the exact height process 1 stops at.
You just need to go into "Advanced" settings tab and set the "Start printing at" and "Stop printing at" properties appropriately for your 2 processes.
For example, if a spot at 100 mm needs extra strength for the infill, make process 1 stop at exactly 100 mm. Make process 2 start at exactly 100 mm. Now, instead of using interior infill at the 100 mm point, this will cause exterior infill to be generated for the layers that meet at the 100 mm point in your print object.
Process 1 will end at the joining point creating "Top Soiid Layers". Process 2 starts with "Bottom Solid Layers". If you set "Top Solid Layers" to 1 and "Bottom Solid Layers" to 1 for both processes then this joining area will have 2 solid layers. If they were each set to 3 then this area would have 6 solids layers, etc. You could use other combinations as well.
METHOD 3
Like method 2 but this uses 3 layers.
Process 1 is your normal process and uses the infill you want. Process 2 has 100% solid infill. Process 3 is the same as process 1.
You make process 1 print until the height of that spot you want to strengthen.
You make process 2 print starting from the exact height process 1 left off at. You make it print until you have as much solid infill as you like, perhaps 10 mm? Any amount is fine.
You make process 3 print starting just where process 2 stops and print the rest of the object with normal settings.
The 3 process method is pretty simple. You just need to go into "Advanced" settings tab and set the "Start printing at" and "Stop printing at" properties appropriately for your 3 processes.
For example, if at 100 mm you need solid infill to be exactly 10 mm thick to make your print much stronger, but you don't care about the other portions of your print having solid infill, then you would make process 1 print with say 10% infill, and stop at 100 mm. You would make process 2 print with 100% infill and start at 100 mm and stop at 110 mm. You'd make process 3 start at 110 mm using 10% infill again.
Pretty cool tricks in all. These are things MakerWare can't do, and one of the reasons I love Simplify3D so much.
Here's an example of method 3. This is a cylinder (cut so you can see the interior) that is 100 mm high. From 50-55 mm I made it have 100% infill. The rest is 20% infill.
- Example of using 3 different processes to make solid infill at a specified height.