My Personal Hell...
The ugly truth about LFMC...
This was the start of my day...
My point being that it's STILL snowing. I have a whack of jobs on the go and I'm running out of time...
Xmas is one of those immovable deadlines, no one wants to hear about how it took 4 tries so far, but you think it will come out on #5... (maybe I should start wrapping the foam molds...)
As I keep threatening that I want to bring theworkshop.ca into the real-world, I thought it a good exercise to set some ridiculous goals for myself and jeopardize every relationship our family has with the circle of friends & Family we exchange gifts with.
Yes, I opted to make castings in lieu of letting my wife agonize over a meaningful yet financially consistent measure of the recipients estimation on the vast dynamic that is part obligation, part desire and part tradition.
All of these plaques will not turn out, each will have a flaw that may be minor, major or just imaginary as I start to lose my objectivity...
I've been drafting designs and milling foam since mid October, I had lots of time... What the fuck went wrong???
I've had 10 individual failed plaques since then... Damp plaster, too many air bubbles on the surface, Cracked (Plaster) or shifted castings, the back getting blown out by as much as 1 full inch.
I never lost my cool, I'd breath slowly through my nose, and turn the plaques over and over in my mind... I tried more plaster, less plaster, no plaster, more sprues, bigger sprues, fewer sprues... I even mixed 400g of talc to 2kg of plaster trying to approximate a closer match to commercial casting plaster.
The last 3 molds didn't even get hit by metal and they were toast. I wanted to try heavy open backed castings, no sprue, heavy plaster mold and just pour... some plaster was fired in the furnace to burnout the foam like a Lost Wax type casting... Each spent days being carefully dried out on the top of the wood furnace that heats theworkshop.ca.
The plaster simply could not withstand any excessive heat over say 150 Degrees F. The plaster apparently calcifies and then definitely crumbles as it has no mechanical strength left.
The only thing that I can clearly identify as the problem is the size of the plaques... any pieces that are 7" by 5" or less work great, once I start to get into the 6" by 9" range the trouble starts. I'm guessing that the surface area from 35" sq onward is able to exert a greater force in lifting the sand, buckling the thin plaster coat etc...
These pieces are in the 50" sq plus range, but are where I have to take this operation. especially with the NexMill-15 coming on-line in Jan/Feb 05, it will be creating parts and plaques that could be up to 225" sq...
All work on the NexMill has been shelved until this is resolved.
As I have become consumed by this situation I will be taking a shot-gun approach to finding a solution to the problem at hand.
First, the pieces will no longer be oriented at a right angle to the flow of the metal, in the hopes that a) the angled sprue will offer better flow, and b) the parts lifting power is reduced and limited to the surface of the edge that is now pointed upward.
The second area to address is the mass of sand that is containing the larger area mold.
These are my new sand boxes/flasks. They are 16" deep as compared to 8" Max Depth that I have been using so far.
As it snowed all day I also took an hour to sift/clean all of my sand, as these will eat up far more than what I've become used to...
This somewhat shaky/blurred image is how the molds will sit in the sand.
Each box will be assaulted by a jig saw arbor for about 2 minutes per side to aid in compacting the sand tightly around the mold.
I have a couple of ideas for a sand compactor, but all require some sort of off-center/eccentric shaking heavy contraption that I just don't feel like fabricating.
Hey, is that one of those lost wood molds that nobody is talking about???
No it is a wood mold, that will be a back-up when the foam part doesn't turnout.
Funny Hhow I always looked down on wood as an archaic medium, but now find that it is actually nice to work with.
What the hell is going on here???
There's more wood patterns... What good are wood patterns for Lost Foam Casting???
The time has come for theworkshop.ca to step back from LFMC and learn some new skills... I actually have high hopes for eventually solving the 35"sq barrier, but by moving to cavity mold casting (Somehow that sounds rather disgusting...) I will be able to create even more versatile work.
A Braun Coffee Bean Grinder makes short work of the kitty litter (made of bentonite clay)... Braun is now officially another company that can send me something (but they won't, like all the others).
The clay is ground to a fine powder consistency, again by a fine Braun product.
This is the selection of techno chemicals that I've opted to start testing with.
"Orange" Anti-freeze, not the pre-mix type, and it looks almost phosphorescent.
High viscosity chain saw oil, just cuz it's real sticky and has a wide thermal range, though is flammable beyond a certain point.
And lastly Synthetic 2 stroke oil, because it was listed in the K-Bond formula developed at Kent State University, for their Petro-Bond version.
The Clay is added in a 1:5 ratio to clean dry sand, and the various liquids were added in equal parts at about 1/2 pint each for 20lbs sand.
This is the toxic mess that resulted after close to 30 minutes of hand mixing...
I feel like I did when I built the lathe and had never used one before starting... But given my pronounced absence of experience and general enthusiasm I think that it has potential.
It is quite stiff to mix now, and holds its shape better than I thought it would...
But having had learned my lesson with the lathe, I do have 200lbs of real Petro-Bond ordered and hope to have it for the new year. With Parting sand and flux/desgassing agent.
If it doesn't snow tomorrow, I'll give the above deep boxes a chance with LFMC, and try some simple pieces in the faux Petro-Bond, until the real thing gets here...
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