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  • Taking advantage of the low melting point of lead free solder I was able to create a simple mold out of mdf with my cnc machine.
  • Lead free solder as well as pewter has a high tin content which melts at around 220 degrees Celsius.This makes it ideal for mdf mold making.It also allows more detail on the mold as the mdf is much easier on my small endmills rather than actually cutting the metal.

Materials and Tools

-CNC machine

-MDF board

-sand paper

-utility knife

-stainless steel cup

-pliers

-clamps

-lead free solder

-CAD CAM program of choice

Disclaimer

working with:

-hot metal

-sharp knifes

-toxic fumes

please take necessary precautions

Step 1:

First I created a 2d drawing in sketchup.

I used the circle tool and then stretched it with the scaling tool to create my elipse then used the offset tool to do the inside elipse.

I then used the 3d text tool to insert the text.

Next I created the pouring sprue as well as the vent sprues.

Step 2:

I use Cam bam to create my machine operations.

Using a one eighth endmill I made an entire pocket cut at a 1/16 inch depth followed by a further 1/16” deeper pocket cut of the border and text.

The pour and vent sprues were cut at a depth of 1/8” using the engrave operation.

Step 3:

After machining take a wood block with some 220 grit sandpaper to remove the raised grain along the cut lines and lightly sand around the edges of the text.

Enlarged the pouring sprue with a utility knife, then lightly flame the mold to remove any raised fibre.

Step 4:

Clamp a flat piece of mdf to create the second half of the mold.

Now were ready to pour.

Step 5:

I melted what I thought was enough solder to fill the mold.

The first attempt was a little shy but no problem if your carefull removing your piece you can just melt it again and reuse the mold.

I melted the metal with a propane torch until it was shiny, this gave me ample time to pour as the piece was rather large, 3.5”x 9”.I used a stainless steel cup I got from dollar store for a crucible, pinching it in a vice to create a spout.When the metal was ready for pouring I grabbed it with a pair of pliers and slowly poured it into the mould.

Step 6:

After about ten minutes the piece was ready for removal.Prying gently with a small screwdriver and scraper starting at the sprue overflow try to pull it out as straight as possible to avoid damaging the mould for future use.

I cut off the excess sprue and ground them down on a 1” belt sander.

Step 7:

I then coated the entire piece with black spray paint and let sit over night.

Finally sand the raised letters and border with 220 sandpaper keeping the sander as flat as possible to avoid touching the background colour. It is possible to bring the finish up to a higher gloss using various grits of wet sandpaper but my son liked the brushed finish look.

Step 8:

https://www.youtube.com/watch?v=creDhhoGyNU

https://www.youtube.com/watch?v=wbjZsFTSE-Q

<p>Could applying talc powder to the mold before casting help with release of the casted part?</p>
<p>I'm not sure although I've had no problem removing the pieces without the use of any release agents.Perhaps the metal shrinks a bit when it cools.</p>
Cool project. Must have been fun.
<p>That's Awesome!!!!! :D</p>
<p>I will give this a try. I have made coins and stuff like this, but haven't used my cnc machine for the mold making. Very nice results!</p>
Awesome, I like the flow lines to allow air pockets to escape, never thought of thay
how hard is the metall piece? do you think its possible to mold a litle thicker pieces?
<p>The metal is pretty solid similar to aluminum.The solder has over a 90% tin content it is important that its lead free.I believe a thicker pour would be easier as the metal would flow better and stay molten longer.</p>
<p>that is cool, have you ever melted down old carburettors and car door handles? It a zinc alloy an also has a low melting point.</p>
<p>No but I will give that a try, I have a pile of old what I call white metal castings.I believe they have a high zinc content.</p>

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