Fab-in-a-Box Invention Kits

Gather example materials:

Create an example invention kit and have it cut out or actively cutting out while students walk in.

Welcome:

Greet the students and introduce the lesson topic: designing and fabricating custom invention kits using CAD software and a laser cutter.

“Welcome to the step-by-step guide for creating your very own invention kit! In this activity, you’ll learn how to design and laser cut a series of two-dimensional shapes that can be assembled into three-dimensional structures.”

Briefly explain what CAD software is and its importance in design and manufacturing.

Show a few examples of invention kits to spark interest and creativity.

Context:

Rapid prototyping, press-fit slot-and-tab assemblies, parametric design

In the real world, engineers and inventors often face tight deadlines for solving problems. It’s easy to get overwhelmed—or to not know where to start!

Invention kits can help facilitate brainstorming and accelerate the prototyping process. They provide a ready-made set of components that can be easily assembled and reconfigured to test out various design concepts.

LEGO bricks are a great example of an invention kit. They can be quickly assembled or disassembled in a variety of ways to illustrate a concept or test out an idea. Your invention kits will work similarly, allowing you to build upward or outwork—but you get to customize the pieces!

Key terms:

Parametric Design: A design process that uses parameters to define a model’s geometry. By adjusting these parameters, designers can easily modify and optimize their designs. This approach is particularly useful for creating customizable and scalable components in CAD software.

Kerf: The width of material removed by the laser cutter during the cutting process. Understanding kerf is crucial for ensuring that parts fit together correctly, as it affects the precision of the cuts and the final dimensions of the pieces.

Toolpath: The path that the laser cutter follows to cut or engrave the material. The toolpath is generated from the CAD design and dictates the movement of the laser, ensuring that the design is accurately transferred to the material.

Brainstorm design ideas:

Begin by brainstorming ideas for the types of shapes you want to include in your invention kit.

Consider both decorative and functional shapes that could be useful for building different kinds of structures.

Here are a few ideas to help you get started:

Body parts: heads, bodies, arms, hands, legs, feet, tails

Decorative: wings, flowers, bows, hats, mustaches, hair

Mechanical: wheels, gears

Structural shapes: circles, triangles, rectangles, trapezoids, bars

Sketch your ideas on paper to visualize the shapes and their potential applications.

Decide on slot placement:

Looking at your designs, decide where you want to add slots or holes. Remember: this is how your pieces will fit together—but only add a few per piece! Too many, and your material’s strength will suffer.

Add lines or narrow rectangles to your design sketch to indicate slot placement.

Measure the width of your stock material.

Just like LEGOs, your construction kit will depend on a press-fit system. Your slots need to hug each other tightly in order for friction to keep your assemblies together.

The width of your slots depends largely on the thickness of your material. Use calipers to measure your stock material. Write this number down.

Determine kerf:

Unlike scissors, laser cutters work by vaporizing a tiny portion of the material they’re cutting. The kerf is the width of material removed.

Sometimes, when we’re creating something purely decorative, kerf can be ignored. However, when precision matters, so does kerf.

For these construction kits, precision matters. If we don’t compensate for the extra material lost to kerf, our slots will be slightly too big. This will cause our assemblies to be loose.

Determining kerf. Most laser cutters cut directly on the center of a line, meaning the kerf is split evenly across both sides.

Note: your kerf will vary based on material type, material thickness, and laser cutter settings, meaning you should always need to do a test cut for any new material you use. The design itself can be any size and shape, but we recommend keeping things simple with a 25-millimeter square.

Option #1: Design your own test piece to cut and measure.

Option #2: Use the test piece supplied.

To calculate the total kerf width, use calipers to measure the cut piece. Then subtract this measurement from the size in the original design file. Note: Be sure to zero your calipers first while they are closed, and to select either imperial or metric measurements, as appropriate.

Kerf = [width of square as designed] – [width of real square]

Calculate & test optimal slot width:

The optimal width for the slots for your construction kit is determined by two factors: 1) the width of your material measured in Step #3, and 2) the kerf measured in Step #4.

Slot width = [measured material thickness] – [kerf]

It’s always best to cut some test files to confirm the best fit (and double check your calculations). Since some materials are more compressible than others—meaning they have some spring to them, like cardboard—the ideal slot thickness can still vary.

Option #1: Design your own test pieces to cut and measure.

Option #2: Adjust or use the comb provided.

Note: this is for a slot-to-slot assembly, sometimes called a dovetail assembly. In these assemblies, two slots slide snugly together. If you would prefer to use a slot-and-tab assembly, where a tab slides into a slotted hole, you will need to run the same calculations but should use this test file instead.

Digitally design your kits using parametric design principles:

CAD design tutorial as appropriate.

If you’re using a software that supports parametric design, you can make your slots parametric and enter the appropriate measurement for them.

xDesign Steps:

Click OPEN on the xDesign landing page

Click the “Minimize” icon in the upper right-hand corner of the Search results page

— the results will be repositioned to the right-hand side of your screen so you can see things alongside your xDesign session

[1] Type “Lesson4” in the Search field, [2] press Enter on the keyboard, then [3] click on the blue header bar (to dismiss the Search History panel)

— the Search results will update to show you the Cardboard Invention Kits template

[1] Drag the Cardboard Invention Kits template into your xDesign session and then [2] click “Cancel” in the lower right-hand corner of the Search results panel

Click SAVE AS… in the dialog that appears

[1] Type a new name for the component (perhaps add your initials) and then [2] click SAVE

Work with your instructor to measure the thickness of the cardboard you’re using for this lesson.

Double-click the “MaterialThickness” parameter in the Design Manager

[1] Enter a the thickness of your cardboard in the “Value” field, [2]  Press “Apply” to update the model, [3] Click the OK checkmark to close the dialog

Double-click the “NumberOfSides” parameter in the Design Manager

[1] Enter a number from 3 to 18 in the “Value” field, [2]  Press “Apply” to update the model, [3] Click the OK checkmark to close the dialog

Repeat the above steps to experiment with modifying the “SlotLength” and “SlotSpacing” values

Click “Save” on the Action Bar to save your cardboard invention kit piece

Extensions:

Consider adding additional holes to fit dowels, chopsticks, pipe cleaners, LEDs, or servo motors in the vein of John Umekubo to expand your kit’s creative potential.

Laser cut the designed parts from cardboard sheets:

If using xDesign:

Click “fab connect.”

Mods workflow

Open laser cutter lid and place stock material onto honeycomb.

Click process.

If using XCS: 

Import design file: Save your CAD file in SVG or DXF format. Then import it into XCS.

As long as it was created at a scale that can fit on the laser bed, it will open at actual size. You can double check by selecting the design and looking at the dimensions shown in the “size” boxes across the top of the screen.

Configure cut settings: Select the appropriate material from the menu on the right size of the screen. (Hint: “corrugated paper” = cardboard.)

Choose cut settings. Select all elements you want to cut and choose “cut” under “processing type” in the object setting menu on the right.

Optional: engraving. If there are any decorative elements you wish to engrave instead of cut, select them and choose “engrave” under “processing type” from the object setting menu on the right. They should fill in. Enter the appropriate settings for your chosen material.

Prepare laser cutter:

Open laser cutter lid and place stock (balsa) onto honeycomb.

Manually drag laser head over center of stock.

Close lid.

Click “auto focus” and wait for machine to focus.

Open lid. Manually drag laser head to top left corner of desired cutting area.

To check framing, click “framing” in XCS and then press the button on the machine. The laser head will frame the area to be cut. If it does not fit on the stock or overlaps a previous cut, adjust the starting position as needed.

Run job:

Click “process” in XCS, followed by the button on the machine.

Remove pieces:

Check to make sure all pieces cut through, and rerun (adjusting settings as necessary) if not.

Remove workpieces and scrap stock from machine bed.

Close lid.

After the cutting is complete, carefully remove the shapes from the cutting bed. Clean off any debris or residue from the edges of the shapes.

Consider saving your excess material once you’ve punched everything out – this can be incorporated into your designs, too!

Build!

Now is the fun part: use your construction kit to build something new! Make assemblies by slotting the shapes together to form three-dimensional structures. Experiment with different combinations of shapes to build various structures. Take note of any improvements or modifications that could enhance the kit’s usability, and consider iterating your designs accordingly.

Build a character, vehicle, building, or prop and write a story about it.

(Re)create a monument memorializing a person or cause important to you.

Design something with multiple degrees of symmetry.

Congratulations! You’ve successfully created your very own invention kit. Whether you’re using it for brainstorming, rapid prototyping, or unleashing your creativity, your kit is a versatile tool that empowers you to bring your ideas to life. Keep exploring and experimenting with your kit to unlock new possibilities and innovations!

Extend:

3D print connectors

Incorporate flexures

Design and categorize multiple types of piece:

Anatomical = heads, arms, legs, hands, feet, tails

Whimsical/decorative = wings, horns, accessories

Mechanical = wheels, gears

Structural = beams

Discussion Questions:

Define kerf.

Do you think kerf width increases or decreases when the laser cutter’s power is increased? Why?

Do you think kerf increases or decreases when the laser cutter’s speed increases? Why?

Optional Tie-ins:

Mathematics:

Geometry and Measurement: Integrate lessons on geometric shapes, angles, and measurements. Students can apply these concepts when designing their invention kits, ensuring accurate dimensions and fit for the slot-together pieces.

Algebra and Parametric Design: Use algebraic expressions to define parameters in CAD software. This helps students understand how changing variables can affect the overall design, making it easier to create scalable and customizable components.

Art and Design:

Graphic Design Principles: Introduce basic graphic design principles such as balance, contrast, and color theory. Students can apply these principles to create visually appealing and functional invention kits.

Creative Expression: Encourage students to express their creativity through their designs. They can incorporate personal themes, stories, or messages into their invention kits, making each project unique and meaningful.

Engineering and Technology:

Mechanical Engineering Concepts: Explore the engineering behind slot-together mechanisms. Discuss how different types of joints and connections can create stable and functional three-dimensional structures.

Technology Integration: Highlight the role of technology in modern design and manufacturing. Discuss how CAD software and laser cutters are used in various industries, from product design to architecture, and how these tools can streamline the prototyping process.

Career Connections:

Learning to design and fabricate invention kits using CAD software and a laser cutter opens up a variety of exciting career paths:

Mechanical Engineer: Mechanical engineers use CAD software to design and analyze mechanical systems. The skills learned in creating invention kits can be applied to prototyping and developing functional components, enhancing their ability to design efficient and innovative solutions.

Graphic Designer: Graphic designers can use CAD software to create precise and intricate designs. The experience of designing invention kits helps in understanding the principles of form and function, which are essential for creating visually appealing and effective designs.

Physicist: Physicists often need to create experimental setups and prototypes. Knowledge of CAD software and laser cutting can aid in designing and fabricating custom components for experiments, allowing for precise control and customization of experimental apparatus.

Marketing: In marketing, the ability to design and produce custom invention kits can be a valuable skill for creating engaging promotional materials and interactive products. These kits can be used to demonstrate product features, engage customers, and enhance brand experiences.

These career connections highlight the versatility and applicability of the skills learned in this lesson, showing how they can be valuable in various professional fields.