Introduction: How to Make and Print a 3D Corn Cob With Spikes

Picture of How to Make and Print a 3D Corn Cob With Spikes

Making a 3D printed corn cob with spikes on the inside might seem like a random project, but there's a really important reason why this should be the next great thing you make!

New technologies often give rise to great concern. Bayer, the pharmaceutical company known for aspirin, bought Monsanto, the largest producer of genetically modified seeds in the world, for 66 billion dollars on September 14th, 2016. Regardless of the unknown promises of their combined technology, including medicated produce, both companies have rich track records of control and corruption. The best way to control the populations of the world is with food, and food containing medication is even more frightening.

We decided to design a cob of corn that appears perfect on the outside but reveals spikes on the inside in an attempt to create awareness about this new and potentially dangerous situation. The object is a symbol of the danger concealed within this new merger. If you want to help spread awareness to the uneducated consumer about this new cause for concern, keep reading!

Depending on your level of expertise in using 123D Design software, this project can take anywhere from 3-8 hours (the latter being if you've never used 123D), excluding a 2 hour print time. Although these instructions are best suited to people who have experience using 123D Design, you'll find links to video tutorials placed throughout the instructable that go along with the steps. Feel free to use them to refresh your memory or learn something new. Happy creating!

Step 1: Create the Shape of the Full Corn Cob

Picture of Create the Shape of the Full Corn Cob

Create four circles using the primitive shapes. The second circle from the bottom should be slightly bigger than the others. Vertically align these circles to the approximate dimensions of the corn cob (6 inches tall and 2 inches wide). Use the loft tool to create the shape of the cob. Note that there must be space between the circles to successfully use the loft tool.

***To successfully carry out this step, select the first three circles and loft them together, then select the last two circles (of the four) and loft them together.

***The dimensions of the corn cob are approximations. You may create it as big or as small as you like, depending on the max size your 3D printer will print. Also, as shown in the picture, the cob is not the same radius everywhere, so 2 inches is an average)!

How to Use the Loft Tool

Editing Edges, Faces, and Points

Step 2: Hollow Out the Corn Cob (this Will Create a Hole in the Bottom of the Cob)

Picture of Hollow Out the Corn Cob (this Will Create a Hole in the Bottom of the Cob)

Use the Shell tool to hollow out the object you have created. Make sure the bottom face of the corn is selected before you shell the object, as this is where you will want the hole that it creates to be. The thickness of the corn is down to you, but it is advised to go thicker than the minimum thickness (2mm) needed for 3D printing, as this object will need to be quite sturdy.

From this point on, we found it easier to rotate the corn cob so that it was horizontal to the grid plane.

How to Shell an Object

Step 3: Cut the Cob in Half and Delete One Half

Picture of Cut the Cob in Half and Delete One Half

Create a rectangular solid object and place it down the middle of the corn. Then, use the Split Solid tool to split the corn in half, as shown in the picture. To further improve the accuracy of slicing the corn in half, make the rectangular solid very skinny. Delete a half of the corn cob to make the remainder of the design process simpler.

How to Add and Subtract Objects

Step 4: Create the Bottom of the Cob

Picture of Create the Bottom of the Cob

Sketch and then extrude a half-circular, cylindrical solid that is the same thickness as the cob itself. Snap it to the hole on the bottom of the cob (that you created in a previous step). It may be difficult to correctly fit the circle in the bottom portion of the cob, so get as close as you can.

How to Create a Sketch

How to Use the Extrude Tool

Step 5: NOTE: the Remaining Steps Will Apply to the Half of the Corn Cob Remaining. You May Keep Both Halves But We Found It Easier to Not Worry About the Other Half of the Corn Cob Until One Half Was Complete

Step 6: Create a Line Pattern Along the Middle of the Cob

Picture of Create a Line Pattern Along the Middle of the Cob

Use the Spline tool to get as close to the cob shape as you can by adjusting where each dot is placed, but it is okay if it isn’t perfect (the image shows an example of where the dots talked about in the step should be).

Using the Spline tool in 123D Design

Step 7: Create an Individual Corn Kernel

Picture of Create an Individual Corn Kernel

The shape of the kernel depends on how realistic you want the kernel to be. In the example, we created an oval shape with the specified dimensions to represent the kernel.

Step 8: Create a Line of Kernels

Picture of Create a Line of Kernels

The easiest way to do this is to use the path pattern tool (the kernels around the ends will be facing the wrong direction, that is okay). Adjust/move the row so that the kernels are flat against the cob (this might cause some to sink into the cob but this is okay)

Using Rectangular Patterns in 123D Design

Using Circular Patterns in 123D Design

Step 9: Copy and Paste This Line of Kernels

Picture of Copy and Paste This Line of Kernels

Copy and paste this line of kernels, then rotate the extra line around the half cob to fill up the space on the cob. Repeat several times until the outside surface of the cob is covered.

Each line needs to be adjusted to fit flat against the cob, otherwise the object will not 3D print correctly.

***This may be a frustrating step! This is where the program is most likely to crash as well because of the large number of individual 3D objects. If this happens, see below in “Troubleshooting.”

Step 10: Clean Up the Ends of the Cob

Picture of Clean Up the Ends of the Cob

Starting with the bottom of the cob, delete any extra and overlapping kernels. Make sure that the kernels do not hang over the end. If some do, select them and move them as shown in the first picture.

With the top end of the cob (shown in the second picture), most of the overlapping kernels will need to be deleted, but leave a few still there. With the remaining kernels, rotate and fit them against the cob so that the design does not look incomplete.

Step 11: Combine the Kernels With the Cob

To do this, select everything and use the Merge tool to create one solid object. DO NOT use the Group tool.

Merging in 123D Design

Step 12: Create an Individual Spike

Picture of Create an Individual Spike

Start with a cone solid and adjust the dimensions to look like the spike shown on the right.

The thinnest the spike can be is 2mm. However, we made ours a little thicker at the base so It wouldn't break off from the corn as easily after it was printed. In our experience, the majority of the spikes came out with the printed support material, so this is the best method to avoid this.

Step 13: Place a Spike Inside Cob

Picture of Place a Spike Inside Cob

There is no particular place the spike must be placed so long as it is on the inside curve of the cob.

***The spike must be placed completely horizontal compared to the cob. You can adjust the angle to be exactly perpendicular.

Step 14: Add More Spikes

Picture of Add More Spikes

Copy and paste the first spike and move each of these spikes to fill up
the cob. After getting a few spikes inside the cob, we found it helpful to select a group of spikes, copy it, and then move this new group of spikes. This saves time and effort in creating many spikes at once.

***Use as many spikes as desired and make sure to keep them all facing the same direction, otherwise it will be hard to remove the support material and can create problems with overlapping spikes.

Step 15: Adjust the Size of the Spikes

Picture of Adjust the Size of the Spikes

Adjust the size of the spikes so they do not extend past the edge of the cob (as shown in the pictures). Afterwards, move the spikes forwards or backwards so that they are embedded in the cob but not poking through the back.

While it might look visually appealing to split open the cob and see long overlapping spikes we decided against this because the longer the spikes are, the more likely they are to break.

Step 16: Combine the Spikes With the Cob

Just like you did with the kernels, select everything and use the Merge tool to create one solid object. DO NOT the group tool.

Step 17: Copy the File to Create the Second Half of the Cob

Label one file "MonsantoCorn" and the other "BayerCorn." You can choose different names for these files, but make sure you can distinguish between the one that will have Monsanto written on it and Bayer written on the other.

Step 18: ​Add the Words to the Corn Cobs

Picture of ​Add the Words to the Corn Cobs

Opening the 123D file labeled "MonsantoCorn," use the Text tool to create the text "Monsanto," then use the Extrude tool to make the text into a 3D object. Afterwards, snap the text to the side of the corn cob with the kernels on it and center it as best you can.

Do the same thing to the 123D file labeled "BayerCorn," except the text should say "Bayer."

Step 19: Print

We chose to use gray PLA because it is readily available and relatively cheap. Each half of the corn cob was sized to be about 6 inches long and 2 inches wide because that was the limit of the 3D printer that we used. The two halves were then printed separately, and the entire process took approximately 4 hours and cost $1.50 for 25.07 m of filament.

Step 20: Post Processing

Picture of Post Processing

Once the corn is finished printing, it can be painted. We used acrylic paint because it is easiest to control, but other forms such as spray paint may work as well. We chose not to paint the inside of the cob and leave it gray to show the contrast of the perfect outside to the unexpected inside.

Using PLA will require more than one coat of acrylic paint, should you choose to do this step.

Step 21: Interesting Idea

Picture of Interesting Idea

If you want an added flare to this project, you can fill the corn cob with slime and glue the halves together by using super glue. This will easily break apart with some force, and you can surprise others by what they find inside!

Here is a link to various ways to make this slime!

Thank you for participating in this project and helping us spread awareness one corn cob at a time! We hope your corn-making experience was successful, but if you have any further questions feel free to post a comment below and we will be happy to troubleshoot with you.

~The Corn Cob Crew

Comments

CornCobCrew (author)2017-03-02

Thank you! You're right, it would be very interesting to see what other ideas we could come up with to go along with this one.

DIY Hacks and How Tos (author)2016-12-10

That is a really creative way to make a statement. With a few more ideas like this you might even be able to put together some kind of art exhibit on social issues.