Third Steps: 3D Molecular Representations

Image of the hemoglobin molecule described in a previous blog post.

Good evening, everyone, I am back once again with another update on my “3D Molecular Representations” project. Since my last post I have been working in CAD and trying my hardest to get this MMU printer to work. In this blog post I will mostly be talking about what I have been up to in CAD as I did not make much progress on fixing the printer issues. Also, the image above shows the print that was running in my last blog post. I personally think the white appears to have a pinkish shade to it as a result of red and white filament being dispensed through the same extruder. I would have expected the wipe tower would completely negate this effect but it that does not seem to be the case.

Designing a Molecule Stand!

Since my goal is to print models of molecular structures, I thought I might want to have a nice figure stand. This was a simple task and I’m pretty proud with how it looks.

Image of the simple base and peg design.

How It’s Made…

Image of the first step which is a drawing of a rectangle and triangle.

First start with a thin rectangle with a triangular top using the sketch tool.

Image showing how the extrude function is used.

Then using the extrude tool, extend both shapes symmetrically to the distance that you desire.

Image showing placement of next triangle.

Then flip your object 90 degrees and use the sketch tool to draw another triangle.

Image showing how to extrude using special tools to create the pyramid shape.

Then extend the new shape but make sure you change “cut” to “intersect” in order to create the pyramid like shape.

Then to create fillets, select each of the corner edges and use the fillet tool (or press f) to create fillets.

To add Chamfers, select each of the top edges and press the modify tab to select “chamfer.”

I was also thinking it might be super simple to make a little “design” in the base of the stand that displays the name of the figure. I think next for the next iteration I’ll make an effort to include this detail.

Making Pegs for the Stand!

The Issue…

My goal in this step is to make a peg attached to the stand which matches up perfectly to a hole in the model itself. This step took me a bit of time since I was not familiar with mesh objects vs model objects. Model objects are basic structures that can be easily made in CAD with a sketch and extrude tool, whereas mesh objects are complex structures constructed by connecting varied sizes of triangles to order to replicate the shape a desired object. When I tried to use both mesh and model objects in Fusion360, the two would not interact with each other and could not act as a single piece but would instead operate as two separate entities. When working with STL files (the files used for 3D printing) it will almost always contain mesh objects.

The Solution…

Now on the surface this is not an issue since the stand and the peg are to be printed separately. However, in order to make a peg hole in the model the mesh and model objects must be able to interact with each other. A model object, in this case a tube, is used to delete a “tube shaped” section of the mesh object to replicate a peg hole. Shown below are a series of images that outline how this is done.

Image showing how the cylinder can be made.

First upload the STL file of choice and then create a circle using the sketch tool and extend it to the desired length. The diameter of the circle dictates the size of the peg hole, and the length will dictate how deep the peg hole will be.

Drag the cylinder into the STL model and position it in the location of the peg hole.

Use the tessellate function on the cylinder.

Image showing where the combine tool is.

Use the combine tool on the cylinder and the STL model ensuring to select the settings shown below.

Image showing how to use the combine tool.

Ensure the “target body” is the STL object and the “tool body” is the cylinder. Select the cut option and press ok.

The Result…

The BIG BAD…

The Great Multi-Extruder Printing Problem

In my last blog post I discussed a big issue I have been running into with multi-extruder printing which is… well working with multiple extruders. I have found that using any filament other than PLA in the MMU results in clogging, jamming, misprints, filament oozing, and print crashes. I seriously cannot think of a solution to this issue and will be trying my best to address the issue next time.

Sneak Peak

For the sake of progress, I decided use PETG filament with PLA filament instead of PVA/PLA. This is because the two filaments are heated at different temperatures and would therefore cool at different times, causing the bond between them to be weaker.

-PLA recommends a nozzle temperature of around 215°C and a heat-bed temperature of 60°C.

-PETG recommends a nozzle temperature of around 250°C and a heat-bed temperature of 70-80°C.

Now after all that good idea talk… ruined because once again the MMU struggled to dispense two different forms of filament without clogging and canceling the print. Instead, I started a print using only PETG using the non-MMU printer just to test the fit of the peg in the hole. My guess is the hole on the model needs to be just slightly wider in diameter to the peg and will also require a deeper hole. Regardless, see you next time!