Teachable moments 1 - Clones!

My GPS Tracker project (See Teachable moments 2) is in the testing phase.  I needed a small package for mounting the parts in the final product.

Answer: Why not make a Vacuum Former to shape plastic sheets?  Let's see how I can get Paige and Ellie involved.  It turns out that they were really excited (or just couldn't sleep).  We even got to explore other ways of "cloning" shapes like wax molding.

Here are a few results

A few finished pieces from Plastic Vacuum Forming

Paige painting one of the wax Clones - a cat

Ellie made a copy of this seal toy

Here's how we completed this project.

Safety - make sure you are working in a well ventilated area
Knowledge - Look at a few websites like Instructables.com, Make Magazine, even Youtube

Components

• Vacuum Former - Large plastic container with a lid, vacuum cleaner, heat gun or hair dryer
• Wax molding - Wax candle, plasticine or playdough, cupcake cups

NOTE: Some hobby shops sell molding and casting kits - shop around for options

Vacuum Forming

1. Test your materials

We tested a few household plastics

Milk containers are surprisingly good!

These plastic plates have nice color and melting characteristics

2. Next, make the former

Use the lid for the vacuum plate

Drill it full of holes

An old water bottle makes a good support

Now use the bowl and draw out a hole for the vacuum attachment

Drill and cut (be careful here)

Seal the vacuum with silicone rubber

Insert the hose and VIOLA - A vacuum former!

3. Now for some testing

1. Place a piece of plastic on top of the former (e.g. the plate we showed earlier)
2. Try the vacuum.
3. Heat the plastic in even strokes with the air gun while keeping the vacuum pressure

Result with an animal shape

Tips & tricks

• Watch for air leaks.  Silicone rubber can seal leaks on the air hose side. 
• Cling wrap is really good for sealing your plastic sheet to the former.  You can heat it along with the plastic sheet and remove it after.
• Practice a few pieces till you get the heat and timing right

And now.. How to do wax molding

1. Make the mold

The kids made their own molds from playdough by squeezing thier toy between 2 pie shaped pieces.

2. Clone your toy
Next, cut up some wax and heat it in the cupcake cup till it melts. The heat gun works nicely. Paigey measured the melting point at about 80 degC with an IR Thermometer.

Disposable hot wax container - A.K.A. cupcake cup

Mold shells with a wax copy

Tips & Tricks

• Stir the wax while it's being heated
• Don't waste your good candles. Use left-over wax from a used large candle
• Create air holes so that air pockets do not build up.  Paige thought through the path of the wax and put holes for wax entry and air exit
• When making the mold mark some lines across the joined pieces to re-align them after they are separated.
• Wait enough time for the wax to solidify

  

Learning outcomes:
- 3D shapes
- Gas pressure, the vacuum concept
- melting point and freezing point