First try at making and using a match plate

Thanks, wow that does look tricky...

I got it to work by flipping the mold over and taking off the drag first, so I could rap on the back of the board a bit better to loosen the fins a bit easier. It meant I didn't have the pins there to guide me lifting the board off the cope anymore, but I just went by feel and lifted it real slow. Seemed to work ok.

Jeff

 

Thanks. "Tactical krinkle finish," I like it. Best of both worlds.

Jeff

 

Thanks Pat, yup, still sampling the bifilm theory kool-aid and it seems to have worked out well enough this time.

I used the sand I bought from Smelko Foundry Products several years ago for facing sand here. It had sat unused for at least a year, and in that time I forgot how nice and sticky that stuff was, as well as being finer than my homebrew sand (it was made with AFS GFN 115-130 silica whereas mine has 75 mesh sand that I got from the pottery supply). I love the finish I sometimes get using that stuff!

I think maybe I will experiment a bit with small additions of calcium bentonite, maybe that will help close the gap between the green strengths of my homebrew vs the Smelko sand. I only have 4% total clay in my own sand, 2% each of sodium and calcium bentonite. So I think there's room for adding more binder without immediately losing permeability.

Sadly there's not much I can do to make the sand grains that are already in it get smaller. I guess I have until I run out of Smelko sand to use for facing, to figure that part out...

I did get a bit of shrink on the 2 brackets farthest from the sprue. It appeared on the inside vertical surface of one fin on each of them, close to the base of the fin where the fillets and the T shaped section are just a little thicker than the rest of the pattern. I did overheat the melt a little bit this time, so maybe simply not doing that again next time would fix it. Failing that I will add (a) riser(s) on top of the second set of gates to help feed those 2 brackets that were affected.

Jeff

 

Here's the accompanying video:



It's a really long one, so here are the timestamp links to the most interesting parts (IMO) for those of you with more sense than spare time.

02:25 to 06:40 - Using a push block that has one end sanded square and one end with draft on it to set the sander table angle and put draft on the tall thin fins. And some pitfalls to avoid while doing so.

13:16 to 14:00 - The glossy spray sealer disaster that is giving me ideas for texturing different patterns... if I can figure out how to do it again on purpose.

23:00 to 23:20 - Demolding FAIL. Laugh it up.

24:05 to 25:45 - Using parting dust to take a print of the drag on the cope to verify the pattern bits on opposite sides of the match plate board are properly aligned. I don't remember ever reading about or seeing this technique before, but I am pretty sure I didn't invent it.

26:45 to 28:15 - Successful (enough) demolding. Please post tips for an easier way that does not involve demolding the tricky side with no alignment pins in place! Also, how are you guys getting/keeping stubborn sand grains out of your flask alignment hardware? I get a lot of crunchy stuff happening when I'm separating the cope and drag, which doesn't make the process go any smoother.

29:00 to 30:00 - Running 5psi propane and a hairdryer in the Red Dwarf, melting wheelium. Takes about 15 minutes from cold start to pouring temperature with this furnace and crucible. Special guest camera operator for this segment: Tobho Jr.

31:40 to 32:27 - The last of the ingots finishes melting, and the mold being poured. Tobho Jr. having long since fled to the relative safety of his online war simulations and future carpal tunnel issues.

33:20 to 36:50 – shakeout and examination of the castings.

I tried to use the Dr. John Campbell & Bob Puhakka bifilm theory based gating and pouring basin approach here, which has been much discussed on this forum. Or at least the best home gamer’s approximation of it that I could pull off, as I understand it.

Jeff

 

Thanks Pat, I was happy with this result and I LOVE my small new furnace!

For clarity's sake, that's Bob P., not that other foundry wizard Bob S. (I was mildly confused for about 5 minutes, but probably everyone else realized that right away.)

Agreed, I remember him explaining (in one of the SWDweeb YT videos he appeared in) how to base the sprue's skinny end size aka runner cross section on the fastest flow rate you can pour at while still being able to control it well.

I never did actually pour out a full crucible and time how long it took to dump out that volume of metal to do the calcs from scratch, but the base of my standard sprue pin that I use these days is very near 1/4" in diameter, and that has proven to be a comfortable size for me for keeping the pouring basin full with a cope that's about the height seen here.

I'm thinking about using 2X4's instead of 1X3's for rebuilding the flask, hoping this buys me enough extra height to put the pouring basin near the edge the of the mold with this pattern, for lower altitude pouring, without the bottom of the basin cutting into the top of the closer set of fins and ruining the mold. Guess I'll find out then if the same sprue pattern will still work as well using a little bit taller cope. Hope so; smooth tapered sprue patterns the right size are hard to find among the random junk I tend to come across. (Or create!) This one used to be a plastic toy magic wand. Now get your mind out of the gutter Jason, I'm talking about the kind of plastic wand toy that comes in a kid's Halloween magician costume kit!

Jeff

 

Thanks, no I didn't say that, but every so often I do think about casting some flask parts like some of the ones I've seen others make... Seems to happen more, the more flasks I burn up.

Edit - I'd maybe try to integrate alignment brackets into the patterns somehow, if I ever did try it.

Jeff