Make Waterproof Prototypes [From Sheet Correx]




Introduction: Make Waterproof Prototypes [From Sheet Correx]

About: I'm a Product Design Engineer, currently living in the UK. I have been fortunate to have lived, studied and worked in Hong Kong, Norway and California. I believe physical models help people to communicate,...

This Instructable will show you how to make lightweight, waterproof models for Correx (which is like Corrugated Cardboard, but made from Plastic), you might have seen it used to make 'For Sale' signs, etc. There are many product made from Correx (like Folio Cases, etc) but these typically require specialist die-cutting methods. The next steps will show you an alternative way to get good results using Glue-Gun to make a neat and water-tight seal.

Originally, I made a tool to help people make prototypes from Corrugated Cardboard, I called it the Card Rabbet Tool... However, I soon realised that the tool not only worked on Card - but also on other materials, including Correx, which enabled me to make a Space Pod to send a Superman figurine 22miles high into space, but that's another story...

...The next steps show you how to work with this material safely and effectively. It could be used for boats, costumes, professional prototypes, architectural models...who knows... so please do share if you make anything using this technique, or improve on the CAD :o)



Check out the original post (with instructions, free files and tips, here).

Teacher Notes

Teachers! Did you use this instructable in your classroom?
Add a Teacher Note to share how you incorporated it into your lesson.

Step 1: Materials & Tools

4mm thick Correx or Corriflute - available from ebay and Amazon as well as many craft shops.

Hot Melt Glue Gun.

Metal Ruler.

X-Acto / Craft Knife, (as oppose to scalpel blades - which you may might find to be too flimsy).

Permanent Market (for marking up your designs).

IPA & Lint-Free Wipes (for cleaning off Permanent Marker, once assembled).

Sellotape (for holding joins in place while glue is hot) & Dispenser (much easier for having other hand free to hold model when hot glue is still hot).

'Card' Rabbet Tool. (Which is designed for the most common 4mm Sheet thickness).

Step 2: How to Make a 90-Degree Joint in Correx

This in fact similar to the methods used on Cardboard, but unlike those in Cardboard, the 'Tool' is required, as the small 'fillet' of plastic cannot be simply 'dug-out' using a ruler - the dual action of the blades is essential.

1. Using the Tool, cut away the fillet from one side.

2. Apply hot glue to the rabbet/rebate area.

3. Bring the two faces together.

4. Use a flat surface to press the edges flat (and avoids burning fingers with glue).


5. This is a simple joint, but for more complex sequences of joining things together, use some sellotape to secure (and pull) the edges together.

6. Remove sellotape once dry/set.

Step 3: How to Make a Cylinder (or Curved Joint) in Correx

1. Many design is Correx do not have bends in them - however, here you can see that a smooth curved surface can be achieved. This only takes around 5mins.

2. Start as before by removing a 'fillet' from one strip of Correx (make sure to note the direction of the fluting - perpendicular to the edge cut).

3. Cut the opposite side of the strip.

4. Make a partial cut through one side of the Correx's fluting. Keep doing this all the way along.

5. You will now have a bendy section of Correx.

6. Cut a tab off the back of the same side of the Correx (this allows it to be glued flush to the other side).

7. Cut out a circle. TIP: Roll it along the edge of the strip to see if it will go all the way around. Trim excess.

8. If you used Permanent Marker to mark-up, use some IPA to wipe clean.

9. Prepare small pieces of sellotape along the edges of the strip.

10. You are now ready to apply glue, the same way as before (though you can do this in stages, as if more than 15cm/6in at a time, you might risk the glue drying/setting too soon.

11. Place one edge of the circle on the Rebate/Rabbet area, and roll along, securing with the sellotape tabs as you go.

12. One side done.

13. Apply hot melt to the other side and drop in the other circle. (If you want to be extra technical, put the two circles' fluting at 90 degrees to each other, which will make it more robust.

14. Apply glue on the tab. Press against the table to avoid burns / give a flat join.

15. Remove sellotape - and it's finished!

Step 4: Building Blocks (for Any Type of Model Making / Prototyping)

These shapes will allow a variety of different profiles to be made, quickly and cheaply.

Some future tips include:

- Try threading wires down the 'fluting' to enable complex assembles to have hidden wire-looms.

- Try designing a net in CAD or Pepakura, print out and transfer the 'net' to Correx - assemble using this method.

- Try Laser Cutting the template if you can't be bothered to cut it out by hand! (You can even cut 'mid-depth' for the bendy bits if you get the settings right, though this takes trial and error, depending on the machine used).

- A larger project I did with this technique was a SpacePod for Superman.

Hope this is useful. Do check out Design Modelling for other ideas - and please add any creations/iterations you come up with below.



Formlabs Contest

Participated in the
Formlabs Contest

Be the First to Share


    • Backyard Contest

      Backyard Contest
    • Silly Hats Speed Challenge

      Silly Hats Speed Challenge
    • Finish It Already Speed Challenge

      Finish It Already Speed Challenge

    5 Discussions


    5 years ago on Introduction

    Cool tool!

    I've seen people who used cartoon blades to cut gently as this rabbet tool, but with this you don't need to be so gently.

    Hey Jude
    Hey Jude

    Reply 5 years ago on Introduction

    Hey aheibi, do you mean like this - so that the corners are rounded? (I'd never heard of it, so just googled it - and it make sense what you are saying). I'd like to think this is a great alternative, so will give it a try, though I tried an X-Acto knife and found that this has a lot of drag/resistance in Correx, so Scalpels are still really smooth for cutting. The only blade I though would be better would be a No.12, but it's a bit savage if it slips down - as it just cuts through the whole piece. It's a fine balance to get right between slicing and not cutting all the way through. Let me know if you crack it - as it'd be cool to have a CRT MkII out there :o)

    carton blade.jpg

    Woah I had no idea that material has so many applications. They models almost look CGI they're so clean!

    Hey Jude
    Hey Jude

    Reply 5 years ago on Introduction

    Thanks. Yes, it was a bit of a bonus that this worked (as is obvious - as I called it the *Card* Rabbet Tool...regretting that now a tiny bit!).

    Anyhow - it makes a great joint between the sheets - as it fills the 'fluting' of the Correx. It opens up a load of cool modelling possibilities... I wonder what people will do with it. (I'm thinking of a boat).