Introduction: Candy Casts

By Maker Resources for K-12
About: The mission of the K-12 Maker team is to help K-12 classroom educators create and deliver fun, enriching Maker experiences - no matter what subject they teach. Building upon our experiences as K-12 teachers, w…
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CREATOR(S): Leilani Roser,Diane Brancazio,Josh Verdejo, MIT Edgerton Center

Math, Social Studies, English, Science, Grades 3 - 12

Lesson Overview

In this activity, students will learn the manufacturing process of casting and molding as well as 3D design. Students use Tinkercad to design and create molds for pourable candies and figurines. The molds are typically quick to print, minimizing 3D printer time. The casting process has multiple hands-on steps extending the activity beyond 3D printing.

Giving students the chance to design their own mold is a perfect opportunity for students to practice process engineering by spotting steps in the candy making process that need improvement. And, working with the positive and negative versions of a molded 3D object help people to develop spatial and geometric awareness.

Simple prompts for 2-3 hour projects can focus strictly on making functional molds, allowing first-time Tinkercad users to focus on learning and using Tinkercad. High school students and/or students who are already skilled with Tinkercad can be assigned complex, higher-order-thinking prompts that require additional time for intense research, collaboration, design, and sharing. Consider the example of these two math prompts and one science/engineering prompt:

Simple: use simple geometric solids to recreate the school logo as a printable, moldable design

Complex: design a process for making 100 candies per class per day, with budget constraints

Complex: (extension of above) identify stages in the process where bacteria could enter the candies - design solutions to prevent contamination

This project is structured to follow the Engineering Design Process (EDP), a process that helps designers in any discipline create solutions to problems. While there are many ways that people solve problems, designers often use the EDP because it offers a clear roadmap for them to follow as they work towards a solution.

First, designers Define the challenge they are facing, then Learn more about the problem and Explore existing solutions. It’s tempting to skip these first few steps and head straight into brainstorming, but don’t! When designers take the time to understand the problem clearly, they come up with much better solutions.

The Design phase is where brainstorming happens. Designers brainstorm multiple possible solutions, then develop a few of them into more detailed plans. Encourage your students to plan at least 3 of their potential ideas before choosing a design direction and starting to Create a product based on their design. If they hit any roadblocks trying to create their first design choice, they’ll be able to revisit their alternate design plans and choose a new direction - without starting from scratch.

Designers then take time to Observe their design and see how they can Improve it. We strongly recommend that students have an opportunity for at least 2 Create-Observe-Improve cycles. When students feel they have to “get it right the first time” they are less willing to take risks and be creative. By repeating the cycle, they have a chance to fix flaws and adopt successful ideas from classmates, and in fact, they’re practicing what professional designers really do.

A good design cycle builds in time for the designer to Reflect on their product and the process of making it, looking for learning habits and insights that will help in future challenges.

When the work is complete, designers are ready to Share. They bring their work into the real world, by posting, publishing, presenting, or exhibiting what they’ve made- even giving or selling if appropriate! For students working through a design process, a real audience helps students connect their learning and work experiences to the world outside the classroom. For Makerspaces and Maker projects, in particular, this is hugely important for building confidence in every student and a sense of community among Makers.

To help students work through this process, be sure to build in planned “stops” at each step for students to record their thoughts and progress as they work through product iteration cycles.

Essential Question(s)

How is the molding/casting process used Making products we use in our lives? How is it possible for factories to make so many of the same thing?

How can the design process and 3D modeling tools be useful tools in learning manufacturing?

Time Required:

1-2 Hours design time + 1- 3 hours class time for melting, pouring, unmolding

Skills Practiced:

  • The Design Process
  • 3D modeling in Tinkercad
  • Symbolic Communication
  • Mold-making process
  • Casting/molding and releasing process

Materials Needed:

  • Sketch paper and pencils

  • Tinkercad

  • 3D Printer and filament

  • Food-safe, fast set, Silicone molding compound (e.g. “Easy Mold” by Castin’ Craft. A one pound kit costs ~$30 and can be used to make about 12 - 16 molds for 1.5” square candy)

  • For candy: Colored candy melts or chocolate suitable for melting

  • Lollipop sticks or popsicle sticks

  • For non-edible figurines: hi-temp hot glue, candle wax pellets, crayons, or plaster

  • Electric skillet and/or pot, slow cooker, or chocolate melter

Step 1: Define

Context

Designing molded candies or figurines is an engaging way for students to learn a manufacturing process while practicing 3D modeling. The activity can be done in an assembly-line fashion or with individuals carrying out each step of the process.

Molded candies or figurines are easily made with pre-made candy or wax chips, removing the need to follow a multi-ingredient recipe. That way, kids can focus on creating unique molds and troubleshooting their design, instead of worrying about troubleshooting a given recipe. (That said, silicone molds are also suitable for molding hard candies like lollipops, which can be a worthwhile challenge for high school chemistry students.)

Challenge:

Students create a mold for creating reproducible candies or figurines, following a theme that the teacher assigns. (E.g., school logo, personal symbol, etc.) Students will fabricate their work using Tinkercad, 3D printers, and silicone molding materials.

Criteria:

  • The designed item meets the theme and design requirements set by the teacher
  • The designed item has at least 2 of the following features:
    • Legible text
    • 1 or more pictures
    • Meaningful shape (other than circular, square or other)

Constraints:

  • The molded item can be unmolded without breaking
  • The molded item shows all desired details from the mold
  • The designed item follows size constraints:
    • Area of design must fit within a 1.5” x1.5” (4cm x 4 cm) square
    • Maximum height/depth of design must be < ¼” (7 mm)
    • Print time < 25 minutes

Student Product / Technical Learning Goals

A custom-designed, fillable mold of a 3D printed item.

Step 2: Learn / Explore

Depending on your choice of topic, this phase can be very brief.

1. Research: Students examine and analyze a few real-life examples of the product they want to create (chocolate, lollipops etc.). Give students examples, and prompt them to observe, document, and discuss:

  • Describe what you see - what are the designs like? Why do you think they were made to be this way? How do you think they might have been made?

2. Collect: Have students document their research on mold-making and casting - it might be a simple matter of having them take notes on a brief video or teacher presentation, or they might be given more time to do independent research. Students can keep an inspiration page such as a blog, Google Docs, a notebook, poster, etc to save notes or images.

Step 3: Design

1. Design: Students use their inspiration page from step 2 as a reference and use one of the following methods to create at least 3 different ideas that meet the criteria defined above.

Option A: draw designs showing how this coin will look, naming each design element

Option B: sculpt design drafts using clay.

Option C: let the students try drafting directly in Tinkercad to get familiar with the program and make practice models.

2. Choose a Direction: Have the students choose a design to model and print.

Examples:

Raised features offer a fun way to experiment with multicolored projects - just use one color at a time, with a pause in between to let the first colors cool slightly.

If you are casting a non-edible object, you might need to experiment with temperature and time. The translucent cast showed above (hot glue) hardened too quickly to take the shape of the mold as it poured, resulting in pooled edges and pits where air bubbles formed (above eyes). The brown cast (photo at right) was made from hot glue and microwave-heated for additional time before being removed from the mold.

Recycled crayons are robust and easy to unmold from silicone, but melting them requires more heat than chocolate. Molds full of crushed crayon pieces can be placed directly in the microwave or filled from standing hotpots of melted crayon.

Step 4: Create

REMEMBER: Be sure to provide stopping points for the class where students can observe, evaluate, and document their designs.

Creating an original item to replicate with casts

Remember that the final product will be a replica of the original.

1 - Create a base to decorate

2 - Add raised or engraved shapes, graphics, and text to the base. (See details below.)

3 - If making lollipops, add a cylinder to your design to allow room for the stick to extend past the edge of the mold.

4 - Group all items together

5 - Check design against size constraints

6 - Export design

7 - Use the 3D printer “slicer” program to check against print time and volume constraints - if you meet the constraints, you’re ready to print.

8 - If your design doesn’t meet the print requirements, go back to Tinkercad and refine the design until you meet the design criteria and constraints.

Adding embossed or engraved images

  • Make or choose a high-contrast image. If it is not in STL format, search online for “convert the image to STL”, and follow instructions(
  • Import the SVG file into Tinkercad workplane
  • Add height to your shape 1 mm or .05” works well) and drop it on top of the base
  • Drag to the base, adjust position, and group with all other parts of the item.
  • For an embossed feature keep your shape solid
  • For an engraved feature change the shape into a hole and lower it onto the base. Group the base and the cutout shape to see the engraved part.

Need a jumpstart? Students can go to the project at https://www.tinkercad.com/things/hG8H4S4ojGv-edge... and start by following these steps:

  • 1. Create a copy of the file for personal use by clicking “Tinker this”– give it a new name.
  • 2. Ungroup the elements and move the pieces apart to see how each is incorporated into the object.
  • 3. Use the design drafts from Step 3 above, and begin to replace parts of the model with original graphics.

Molding replicas of the model

  1. Prepare molding compound according to manufacturer’s directions
  2. Squish your printed model, face down, into the molding compound - press the molding compound up to the model around all edges, making sure that all edges of your printed model are touching molding compound. (If you have a stick-holder for lollipops, leave the end of the stick-holder open.) For younger grades, this may take a few tries.
  3. Let molding compound cure according to manufacturer’s directions, then remove the printed model. Some compounds set in just 20 minutes, others may need to set overnight. Check your directions!
  4. Rinse and dry molds
  5. Melt and pour chocolate or wax pieces according to manufacturer’s directions or trusted tutorial - there are many great tutorials on Instructables on melting and molding chocolate, wax, and/or plastic - happy searching!
  6. Let chocolate cool and harden before unmolding - again, refer to chocolate manufacturer’s tips.
  7. Take a moment to document cast work before eating or gifting!

Step 5: Observe, Improve, Iterate

Be sure to provide stopping points for the class where students can observe, evaluate, and document their designs.

1. Observe and document: Students print their designs, share, observe, and document what they notice. Some possible note-taking prompts they might respond to:

  • What do the designs look like now that they’ve been printed and cast?
  • What parts of the design are unclear? Is anything too big? Too small? Blurry? How could the design be changed to make them clearer?
  • When others look at the cast, do they see the ideas that the designers wanted them to? If not, what changes can designers make?

2. Improve: Students use their observation notes to return to Tinkercad and make slight alterations to their design. If any students are feeling particularly discouraged by their first round of creating, redirect them to their alternative designs

4. Create documentation guidelines for students to record their thoughts and progress as they work through product iteration cycles. This can serve as a formative assessment.

  • A description/sketch of the original design
  • How well the design met the project definition, criteria, and constraints
  • What students liked about their design
  • What students want to improve on the design
  • Suggestions for improvement

Download pdf at bottom of this step with possible discussion/documentation prompts for Steps 5 and Step 6.

3. Iterate: Follow instructions in the Create Step as needed for the next iteration - we strongly recommend that students have an opportunity for at least 2 design-build-improve cycles. When students feel they have to “get it right the first time” they are less willing to take risks and be creative. On the second time through, they can fix flaws and adopt successful ideas from classmates.

Attachments

Step 6: Reflect

Reflect: After the design and build time is over, have students reflect on the process and product. This reflection is similar to the one in the “Observe, Improve, Iterate” step but now includes reflection on the process as well. At this point, students have learned about 3D modeling, mold-making, and the casting process, and have lots of new skills and experiences.

Download pdf at the bottom with possible discussion/documentation prompts for Steps 5 and Step 6.

Attachments

Step 7: Share

Give the students an opportunity to share their molds with the class or some other community. Options for sharing include presentation, demonstration, blog or online post, video clip, physical display, family events, and maker fairs - or in the use for which it was intended.

Step 8: ​Resources

First time making molds? Get some general information and tips right here on Instructables: https://www.instructables.com/class/Mold-Making-C...

Edible working materials:

  • The most inexpensive edible chocolate material is commonly called compound chocolate, in particular, the kind labeled “candy melts.” Compound chocolates contain vegetable oils as a substitute for more-expensive cocoa butter, usually contain dairy, and may contain soy. The flavors are often mild but they are the most user-friendly option for beginners. For a lesson that centers on designing the molds, this is probably your best option.
  • Couverture chocolate contains cocoa solids and cocoa butter, and may contain dairy - as you might guess from the name, it’s used for covering the outsides of truffles, pastries, and other chocolate-coated confections. Due to the presence of cocoa butter, couverture is preferred by serious chocolate makers and costs more than compound chocolate. Expensive higher cocoa butter content allows properly tempered couverture to harden into chocolates with an attractive sheen and a hard “snap” when bitten or broken. And because it needs careful attention to melting temperature to produce a good cast, it’s probably best reserved for older students and longer class blocks. For a chemistry lab or a culinary class, you may want to make a mini-unit out of exploring how to temper chocolate.
    • Not recommended: chocolate chips or pre-made chocolate bars. They typically have a much lower cocoa butter content than couverture and are difficult to temper. Casts made from these may get stuck in fine-detailed areas of the mold, and the final product will be soft, mushy, and vulnerable to fingerprints.

  • Hard candy requires high temperatures to transform the sugar solution into something that will harden properly, and is probably best left to older kids, working in rooms outfitted with gas or electric burners.

Step 9: ​Project Extensions

ELA + STEM:

Math

  • Students practice measurement and quality assurance by designing items with stringent specifications:
    • Minimum/maximum volume
    • Specific mass (e.g. every piece must be within .8-1.2 oz and show predictive calculations based on design)

Math + Social studies:

  • Students work in groups to design fundraising items and sell competitively Requirements may include but are not limited to:
    • Minimum number of geometric solids used
    • Minimum/maximum volume
    • Specific mass (e.g. every piece must be within .8-1.2 oz with predictive calculations shown)
    • Maximum time/ease of production per unit
    • Method of mass production
  • Student teams compete to design fundraising or commemorative items for a school group, with only a limited selection being produced after judging

STEM (Biology, Math) + Social Studies (Economics, Industrial Revolution)

  • Design equipment and process for making 100-1000 candies in a given timeframe (class period? day? week?), with budget constraints.
  • Identify stages in the process where bacteria could enter the candies - design preventive solutions to contamination.
  • Define costs of labor, materials, set price accordingly - or set price first and design manufacture process to reach the goal.

STEM (Chemistry)

  • Practice tempering chocolate* or making hard candy (e.g. lollipops) as an introduction to practical chemistry lab skills (reading directions, using heat, closely observing and appropriately reacting to changing materials) or to demonstrate concepts of molecular arrangement in solid structures (chocolate crystals, amorphous sugars) - use with molds. Be sure to use food-only pots, stirrers, and materials containers! *better for 60+ minute class periods, older kids, and small groups - may be best offered as an extra-credit project that only a handful of students work on at a time.

Visit our website k12maker.mit.edu to get resources for K-12 teachers:

Maker skills workshops for K-12 educators - Spring, Summer, and Fall

Lists of Tools and Materials and illustrated charts to print and post

Supervision and safety guidelines for shop administrators

Training guides for common tools (including student checklists and refresher guides)

Our Maker Methodology for designing Maker Projects for core curriculum, including sample projects.