and yet Even More... Metal Casting with Foam

...and yet even more Lost-Foam Metal Casting

Surface Treating and Misc

This going to be a major installment, as I've been able to plug away at this over a period of days and now have as much images and info together as I need to make my notes... These pages are my penance for making hurried errors and force me to either determine where issues arose or to help others from repeating my mistakes...

Typical start, slap down some lines...

Some folks use a wire cutter, and I built one a while ago... But I do need to keep using the Bandsaw, as it's a skill that's directly transferable to metal and wood...

Since I do tend to hack at projects, what little discipline I try to impose on myself is for my benefit only...

The finish from the saw is very nice, but a Foam Wire Cutter is superior, if you take the time to set the voltage to the point just prior to melt-back (where the foam shrinks back from the wire), and you can keep a constant feed-rate ( a function of melt-back...)

Here's an old trick I still use, a router bit in the drill press to mill out sections or surface a foam plug.

In this case If chucked in a beveled edge bit with a contour bearing to follow the edge. This helps set a bland looking piece out as a bit more fancy.

This piece is part of an optic apparatus that I'm building as part of an other series of projects I'm working on... The base will support an adjustable arm for "Macro Photography and video imaging"

Here are the 5 pieces that I'd hope to cast, only the center 2 came out, they each had flaws, so here we are trying to figure out how to avoid that in the future...

The top 3 pieces were all cast on a single tree that just didn't make it (due to cold slushy metal) so all of those images are omitted.

It has been 10 (ten) weeks since it's been warm enough to cast in my area, and I just lost my cool... I wanted to be splitting wood, making roads for Maple syrup, melt metal and drinking beer with friends all at the same time... I'm surprised anything turned out.

The beginning of my problem is with this plug, I've started to use hot glue like it was a do all wonder bond. Which it is, and I'm not trying to take back or change my earlier statement's about hot glue, Great Stuff, but be judicious in it's use. Quarter to 1/8 inch thick bonds are unnecessary and wasteful of the glue and the energy that's invested into the metal to make it flow through the glue.

I'm not only visualizing the path the metal takes, but also gauging the thermal transfer required to pass through varying densities of material.

This is where uncharted ground starts, painting the pieces.

The credit here goes to Nigel V. a once student at Ottawa University. Nigel Emailled this tip...

Paint foam parts with a latex paint and then coat with a high temp (typically BBQ) paint... Thanks for the tip...

The pieces were all painted with 2 coats of the first can I could put my hand on in theworkshop.ca... using the home made air compressor, which as become a permanent fixture and well used.

Here is a can of the cheapest BBQ Hi-Temp paint I could find at Canadian-Tire, I believe it was just under $5 Canadian.

This should last quite a while as very little is used.

Here is the base with a single coat of the Hi-Temp, you'll see in the next image why I only did one coat and only the part that would benefit from the finish.

The top of the sprue and feeds just get cut-of and re-melted so they are fine as is...

Either 3 or 4 coats of Latex are required or, only one coat of the Hi-Temp...

Regardless, this piece started to shrivel-up as shown, and eventually got worse over time. The whitish specks on the black are pink foam oozing out like a pussie discharge from an infected wound.

This is exactly what happens when you try to fiber glass plain EPS foam.

The base is usable, though the front-left pad didn't fill completely and appears rounded.

The foam in this case also was attacked by the hi-temp paint, but it is barely visible.

The plug sat over-night and through the morning before being cast. In the future, I'll paint the hi-temp on within an hour of casting, as it dries within minutes.

The Swivel head piece that was to have supported a miniature camera had a more exaggerated flaw. First I wanted to illustrate that the casting with just latex (this is NOT the same piece that had shriveled) had a heavy black coating over it's surface and required more Wire Brush work than an untreated casting.

Similarly I wanted to show where the flow of metal stopped. This is definitely due to the Hot Glue plug that it just couldn't burn through. This particular feeder had quite a bit of glue both at the top and bottom. My best guess is that it made it's way through the first batch okay but had expended enough energy that it couldn't stay liquid through the second. Also there was a chunk of plasticized sand immediately where the glue was, NOT completely melted. This pour was good and hot (vague and subjective but accurate), and there was enough head in the sprue to feed the plug completely.

The stand is for this type of Macro Imagery. The special camera is less than 1" from the metal, and is picking-up tremendous detail. A full detailing of camera comparisons can be found elsewhere on this site.

This is an Un-painted length of sprue out of the scrap pile from a previous casting.

This is the swivel assembly of the camera mount (smaller V shaped casting).

This is Latex paint only again 2 coats. the finish is visibly better. Beyond the extra elbow grease to wire brush it clean, it had no sand inclusions at all, and is visibly smother than the unpainted which has excessive sand and is more pitted and irregular in it's surface.

Finally, this is the Latex & Hi-Temp coated piece, and it is Very Slick and smooth compared to either of the other two.

All images are tight Marco Shots and show far more than is normally visible. Each finish is unique and I'll continue using all three, as well, I think far more effort will have to be put into the raw EPS Foam finish itself before deciding to paint and or coat.

There is only so much that the paint can fill in.

The image on the left is really a dumb thing I did at the end of a pour... I like using tin cans for smaller objects, just to keep the sand sifting to a minimum. With the last of crucible I poured it all into the can thinking that it would be easy to get out. Not likely as the can is ribbed and had to be ripped open to get at the casting.

The image on the right is the actual casting of a star with a small crystal I pulled from the chandelier in our hallway (you'd be hard pressed to notice it was missing) The crystal is cracked from the heat but the surface is intact. It is being held into place by small dabs of hot glue that did get melt and get replaced with alloy.

The last item is a small emblem I cast for a friends wife.. it is the logo from her business, that she carved into the foam with a dremel type tool.

The surface was brought down with a rasp and Bastard file, 200 grit, 320 grit and lastly 400 grit with water. It's not a chrome like finish but it is quite nice for about 30 minutes total work from foam block to metal (less melt time)

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