Creating model of disc with offset hole for 3D printing

Question

For an engineering project I have been requested to 3d print a disc with the following characteristics:

• 7.5 cm diameter
• 4.8mm thickness
• hole with a diameter of 1.27 centimeters through the disc and offset from the center by 1.905 centimeters

The modeling software available to me is Blender, and we are exporting the model to a .stl for use with the MakerBot Replicator 2X. I have never used Blender or this printer before, but was able to create a model of the shape I require without too much difficulty and export it to the printer.

I have however come across many problems with how the printer builds my model, depending on adjustments I make in Blender and in the printer settings:

• It will create a solid disk with no hole but with ample honeycomb support inside, which is what I desire
• It will create a disk with a hole and all of the proper dimensions but omits support structure inside, leading to the printer being unable to properly print the top part of the disk.
• Only fragments of the model make it into the final product.

I have linked the .stl file I am currently working with. If anyone has experience with either of these programs and could take a look at the file and explain the issue to me, I would appreciate it. Like I said, I'm new to these softwares and the printer, so I'm sure it's a small thing I missed.

Answer 1

I just had a look at the file and I can see disconnected geometry around the top and bottom rings:

Trying creating it in a similar fashion to this:

Add a circle mesh and select Nothing on fill type.

Tab to go into edit mode. Select all by pressing A. Press E to extrude and press Enter without moving the mouse. Press S to scale in toward the center. Then select the new hole and offset it by the proper margin.

Select all (A) and extrude again in the Z direction this time. You now have a hole with faces:

Another way to do this with a little more precision is with the knife tool (you can find tutorials on this forum). But after you make your cut, and delete the faces, you must Bridge Edge Loops by pressing W: