Cast Metal Wall Hangers

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Learn how to make these fabulous metal letter wall hangers with this tutorial! Choose your preferred letter in your favourite font and eternalise it in aluminium (or other metal) using a sand casting technique.

Software used:

1. Adobe Illustrator: prepares the linedrawing of chosen letter in chosen font.

2. 3D software (Solidworks, Rhino, whatever works): import linedrawing, trace it, and extrude it. Creates the printable digital model.

3. Slicing software (Cura, Slic3r): import STL file and determine the print strategy.

Let's get going...

Step 1: Download the Files

Here are the original files that I used to make this y-hook.

However I recommend to use it mainly for guidance as the core of this project is really the customisability: the letters and fonts people like vary widely. Attached here is a lowercase letter "y" in Giddyup font. Although it has a curly form, it is actually easy to cast as it flows well (no bottlenecks or overly wide parts).

If you simply want to make a test piece with minimal effort, then the STL file is the one I printed.

Step 2: Make Linedrawing of the Letter

Choose a letter and go through all the fonts you have installed in your computer. Pick your favourite(s).

In Illustrator, activate the letter you want to craft and go to Type > Create Outlines. This converts it into a vector linedrawing.

Once you're happy, export it as DXF file.

Step 3: Make 3D Model of Your Letter

Import the previously created DXF file into your 3D program. Trace the outlines and extrude to your preferred thickness. I recommend it at least 1 cm though, as you will be sanding and polishing the metal product later on. It also looks more solid and valuable when thicker.

TIP: use a special feature called 'draft angle' when extruding the outline. It will make the subsequent sand casting affair much easier: it helps to release the mould from sand. I recommend an angle of at least 5 degrees.

Add small fillets to the edges, makes it look nicer.

Export it as a STL file.

Step 4: Prepare Model for 3D Printing

Import the STL file to a slicer program such as Cura or Slic3r. This prepares your model for 3D printing.

For example, my letter was printed in PLA using a layer height of 0.4 mm, 6 top layers, 3 bottom layers, 2 wall layers and 0% infill. No support, no brim (only a skirt). Printable in less than 30 mins.

If you're printing at a local fab lab, it's better to check with them what printers and filaments they have available. They can advise you the best. Simply bring this STL file with you.

Step 5: 3D Print the Letter

This will be your mould for metal casting!

Step 6: Fill the Sand Box

If you're sand casting your metal end product, then get yourself a wooden frame that fits your letter leaving room around edges, and some green sand to fill up the frame. FYI it's a special aggregate of sand, bentonite clay, pulverized coal and water.

Because of the draft, one side of the letter is smaller, other is bigger. Put the letter in the frame ensuring that the bigger side is facing down. Pack the sand around your letter very well, leaving no air trapped. Build up in thin layers and tap the sand with a tool (such as wooden stick or metal rod) firmly and evenly. Fill it up to brim.

When done, turn the frame upside down and your letter will appear, mirrored. Apply some talc powder to reduce stickiness. We are going to make a sand lid over it.

Step 7: Make a Sand Lid

Take another wooden frame and place it over the previous frame with letter inside. It needs to fit perfectly. We are not going to do two-part casting but something similar to it.

Fill the new frame halfway with sand. By halfway I mean at least 3 cm in thickness.

Step 8: Create Casting Holes and Tunnels

When finished, take the sand lid frame off and turn it upside down. The talc powder should leave a (faint) impression where exactly the letter is. This allows you to precisely carve out your pouring tunnels and air holes.

You need to be quite strategic where you pour the metal in and where you let the steam release. It is entirely dependent on your form, however. In this case, I made two pouring tunnels at the branching points of the letter so that it will immediately flow in as many directions as possible. These two holes need to be connected somehow so that it is possible to cast only once. This is preferable because aluminium cools down and hardens quickly, every second is at stake. So I carved a sort of crater around the two holes (looks like a piggy nose) that will contain molten aluminium and make it flow into two tunnels simultaneously.

The air holes should be made at the very extremities of your model where the metal will flow the latest. This ensures the material will flow though your whole mould.

Step 9: Demould the Letter

Return to the first sandbox where you still have your 3D printed letter sitting in. You now need to fish it out so that it leaves behind a perfect imprint. This is where the draft angles can really come to your aid: it will be much easier to lift up your letter.

For quick DIY handles, I drilled some holes and put woodscrews in. I pulled from these but it was still very problematic to remove the Y: the enclosed areas and sharp angles, for example, want to take the sand out with them. Hold your finger down in these areas. If it still comes out, you can carefully manually reinsert the sand in the imprint. Make sure the imprint is clean inside, i.e. no loose sand bits.

Once done, reassemble your two frames, so that the sand lid covers the letter imprint. It is ready now for casting.

Step 10: Collect and Melt Your Metal

I was able to get my hands on some aluminium tube offcuts. The smaller bits and leftovers, the less time it takes to melt them. You can use an oven, but I used a blow torch to speed up the process.

Step 11: Cast the Metal

Once liquid, pour the metal into the crater (piggy nose) that you made. Work quickly and efficiently, as aluminium will harden fast. Make sure you leave an excess material on your sand lid — this will become the wall mount for the letter hanger. (This blob of metal is usually cut off and sometimes wasted but in this case it becomes a functional part of the product)

Step 12: Remove the Product

Wait until the metal cools a bit and get yourself a pair of pliers to handle the burning hot metal. The most satisfying bit of the whole process is grabbing your metal product and lifting it up from sand. Place it under running cold water after which you can take it in your hands. Examine it. What went well, what not so well? Almost definitely there will be some imperfections. It's up to you if you want to do something about these. If yes, continue to next step. If not, congratulations you're done!

Step 13: Post-processing: Sanding, Filing, Polishing

I used several tools to refine my y-hanger. Firstly it was the sanding machine to level to front face of the letter and back of the wall mount. This gets rid of some dents but I'm not interested in removing them all. Other areas like the back of letter and top of wall mount I left intact. Then I used the file to refine the shape and raze off excess material, as well as rounding off any sharp edges. Finally I used sanding sponge to make the top surface satin-like smooth and pleasing to run your fingers over. If you have some surface decolouration from impurities in sand, then sponging it gets rid of these too.

Step 14: Enjoy Your Wall Hanger :)

Your metal wall hanger is now ready! Use glue or screws to attach it to a wall. Depending on the letter and font, you may find that there is a multitude of ways to hang your stuff. You may arrange the letters to form words or leave it abstract, up to you!

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