Metal Casting with Sand

Plaque Casting

unfortunately more Don't's than Do's...

Rather than start this installment off on a negative note, I thought it best to highlight a few of the ones that actually made it out of the sand alive.

This is the commemorative plaque of the "Black Lodge", The hunt Camp I used hunt with... This has yet to even have a wire brush over it.

In total there will be 10 plaques for the founding and associate members. And then the Gcode will be erased, never to be run again.

I think that I may have just coined a phrase... Yep, they erased the GCode when that one was made...

Just for kicks I thought I'd run off the Black Lodge code over a blank of Clear Pine...

Pretty cool eh?

The issues here are the same as when I first started into cutting foam. The actual cutting bit and the depth of cut has to be fine tuned.

This is 2 complete passes at approx 30 thou per pass. Any thing over 30 thou seemed to break the 32nd" cutter tip.

This is a prime example of how far the mill has progressed, this custom grill emblem is slated for a buddy's Nova SS should I ever get a decent pour.

So far it has been cast four times unsuccessfully. The fine raised letters always have imperfections. It's almost as though I need some sort of Metal injection system to completely fill the pattern.

After attempting various positioning in the sand, it was time for something drastic, a philosophic shift in how the metal gets poured and what it gets poured into.

Above, to the left is plain clean kitty litter, to the right is a coffee grinder that was used to reduce the granular clay to a very fine powder.

Below, Sifted sand and generic drywall compound typically used for mudding taped joints and covering cracks in wall board.

The idea above is a variation on Dave Kush's plaster dip process, he has had fantastic results, and inspired me to see if I could apply the concept to plaque casting. I don't know why I don't just follow his directions but felt compelled to concoct my own secret grog.

This is the chevy nova logo embedded in the mix after 2 days and a final drying period in the oven at about 150 F.

The cracking started within the first 8 hours or so and only got worse as time went by.

I figured that I should see this through even if for no other reason than to see if the mold could be removed from the compound, and if so, what would the impression look like.

As you can see it didn't come out, nor could I even determine what the finish would look like once I busted the mold out.

The objective here is to be able to orient the plaque face down to maximize the weight of the feeder sprue to force the metal into the finer details of the lettering and graphics.

This is the result of a 9 by 4 " plaque that's been plagued with the same issues that the Nova Logo has suffered... Similarly it has been cast a number of times unsuccessfully...

The "Face Down" theory is sound as every letter formed, but the micro cracks and air bubbles that were in the grog came out with a mess that simply couldn't be cleaned up.

This was encased in a much thinner version of the slop that was shown above on the Nova Logo.

The image below to the left is a back view of a defective casting, the curved feeders definitely are an improvement, but the positioning is far too low on the plaque.

The image above to the right is the front of the same plaque, the picture doesn't capture it as clearly as I'd wanted but the lettering at the top of the plaque is considerably less defined than the lettering in line or below the feeders.

I did want to close out this episode on a positive note as it was opened.

Here is casting number 5 or 6 (I've lost count), not plaster dipped, but the feeders are mounted high and a full pop can was used to create more pressure to feed the mold.

The high gloss black creates a nice contrast, and the hand polish on the surface is enough distraction from the minor imperfections still visible.

The issue of plaster encasing will be revisited, but my energies are being investing in making a better Melting Furnace. If I could bring the metal to an even higher temp and closer to water I may be able to finally pour the perfect plaque.

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