SpiderMan Refrigerator Magnet and Using Fusion360 to Resize Large STL 3D Files for TinkerCad

In this Instructable I will walk you through reducing a STL file, load it in TinkerCad in order to make a refrigerator magnet.

First of all, What is an STL file? Put simply, The STL file basically describes only the surface geometry of a three-dimensional object using tiny triangles (also called “facets”). 3D Printers can print stl files.

Tinkercad is a free-of-charge, online 3D modeling program that runs in a web browser. Since it became available in 2011 it has become a popular platform for creating models for 3D printing as well as an entry-level introduction to constructive solid geometry in schools.

It is really very simple to take a 3D STL file from a free site (like Thingiverse.com ) and use TinkerCad to create something completely new. TinkerCad limits the number of triangle a model may have to 300,000. Why all the triangles. The more complex the model the more triangles are needed.

What do we do if the file is to large? We can Reduce the number of triangle by using Fusion360. Fusion360 can look for a few triangles that are mostly flat and group them and reduce the number to one manageable by TinkerCad. There is some loss in the model when we reduce the number so we want to be careful about how we do it.

A computer (PC/Laptop)

• Fusion 360
• Web Acces

3D Printer

Small ceramic round magnet. (15-18mm)

Optional

• Paints and primer
• Rust-olem primer
• I user Red Enamle spray paint
• Black felt tip marker
• Silver marker or white paint.
• Gorrilla glue.

So for this project I thought I would make a refrigerator Magnet of Spiderman.

First I go to Thingiverse.com and find a good model. I use the Spiderman Head by zacleung found here: https://www.thingiverse.com/thing:2185524

To download the file click on "Thing Files" the click Download next to the model.

Attempting to load the above STL into TinkerCad will give the following error:

In order to load the image we need to reduce it. To Do this we will load the STL into Fusion 360:

Fusion 360™ is the first 3D CAD/CAM tool of its kind, connecting your entire product development process in a single cloud-based tool.

Fusion 360 has many different options to get it for free trial or monthly license. You can visit AutoDesk.com on your own

Fusion 360 calls STL files Mesh. Once Fusion is running click on Mesh to enter the Mesh Menu, then "Create" and "Insert Mesh" to browse to your file and load it. Press the "OK" button to finish loading the file.

Once the model loads, there is a Navigator on the left, if we click on "Bodies" and right click on SpidermanHead, we can go to properties. This will make a popup that has a Mesh section. You click on the Mesh section and it will show you the Facets (triangles) in the Body.

So we see the problem, TinkerCad only allows 300,000 triangle and we have 354,866.

We need to reduce the number of triangle. Fusion 360 can do this by merging triangles together. This loses some of the detail so we was to reduce the count to just under 300,000. To find out the Percent to reduce the model we do some math:

(desired 300,000)/ (actual 354866) *100 = 84.5%

We will reduce the model to 84% to give us some extra room.

Click on "Modify" in the menu, then pick "Reduce" from the dropdown. In the popup change the "Proportion" to the 84% we calculated above.

When going back to properties as above we now see the Mesh has 298,104 triangles and we can now save it.

Right Clicking on the body will also give us an option to save the Mesh.

Change the file Format to be STL (Binary).

Enter your new filename and exit Fusion 360.

Now that we have the facets or Triangles down below 300,000 we can go to https://www.tinkercad.com

Login to your account or create a new account.

Then click on "Import" on the right menu, and pick your new Spiderman Head file.

A head will now be on your "Workplane"

I found the head was by default to big, I reduced the height, width and length by half. To do that you click on the image and then click the white squares to get the size.

After the model is smalled, I used, 33x45x39

Rotate the head to its upright, Its easier to work with it that way. To rotate click on the model and when the curvy arrows appear click them and rotate the dial to set the head upright.

The next we need to cut the back of spiderman's head off so its flat. This is the side that will sit against the refigerator.

Place a 'Hole' grey box behind the head and expand it to cut from top to bottom the entire back of the model. Then highlight both the square and head and click the merge button to remove the material.

Next we make the Hole for the magnet. My magnet is 15mm in diameter, so Drag out a cylinder "Hole" and set it to the dimensions of the magnet, and rotate it 90 degrees. Then using the up arrow move the magnet to the back of the head.

One the magnet 'hole' is at the right height we can use the Alignment button to center it.

Make sure the 'cylinder' is in deep enough for the magnet.

Highlight both items and hit the merge button.

You may now hit the Export and print your file.

Try it for yourself here:

Next I printer the STL file that was in my Download directory.

I rotated the head to be magnet side down. I printed with 'supports'.

Once printed

• I sprayed it with primer. I am not sure if that is required.
• Next I sprayed it with Red enamel spray paint.
• I highlighted the lines with a black felt tip marker
• and I colored the eyes silver. My 3D printer isn't great but panting really covers any flaws.
• Then I put the magnet in the back, it was a tight fit but a added a spot of glue.

Good luck.