Thanks Everyone! Yes, I did get stuck trying to lift out yesterday. My afterthought duct-tape handle was not Class A tooling... I will need to improve the whole pattern making thing dramatically. I am 'superglue-ing' the 3D print in the inside corners and then will add provisions for lifting screws. Maybe paint and wax and ram it again to see what happens. On a good note, I left my sand set overnight with the cover a bit open and it 'squeezes' better, hardly any residue on my palm.
Yes I did! I did not see that until too late.. I am sort of liking the whole 'dump it out if it doesn't work' thing with sand. I have been working (playing, ramming, dumping) with a couple different pattern and went back to the drawing board fom something less ambitions with better drafts and fillets. Besides I told Jeff I was going to make a round tuit... So the second picture- had I not had a social engagement, I would have trie4d pouring this but did not know how to handle it as far as cope/drag/sprue/runner/riser goes. Would this best be done in the cope? My foundry buddy was telling me details in the drag so defects are on the back.
Hi Denis, I was using the handle end of the chip brush vertically . The first picture maybe 10 to 15 little taps/raps. The second picture was more raps with a little more force, trying to imagine where the letters were, but still not that hard. Pattern is a little over 4 inches/ 100mm diameter and .25 inches/ 6.4mm deep at 5 degrees, letters are .062 inches / 1.6mm at 10 degrees draft with a fillet at the base and top edge. Outer rim is same deep as letters but only 5 percent draft. It is printed so the fillets are little stairsteps rather than a machined or glued fillet. This one does not have wax. I tried one with #2 wax and it seemed too slippery, it came out by itself while flipping the flask over.
Watched this a couple times on YouTnbe: Pattern is rammed in the overturned drag so 'good' face is down as cast, struck, then flipped up. Cope is added, vent and sprue tubes added, rammed and struck and tubes removed. Flipped open, runner cut, pattern rapped and removed. Does this seem like a good order of things for the tuit?
I usually ram flat back patterns with the details in the drag. I also usually ram the cope separately on a flat board so I’m not ramming on the drag sand/pattern and potentially deforming it. Sometimes you might want the pattern to stay in the sand for one reason or another, but a flat back pattern that just falls right out would be ok with me. Pete
To get a basic understanding of the process, yes. As for technique or basic safety, no. This how people get hurt. Too hot to wear boots, apron, long pants? Then it’s too hot to pour metal. Period. Watch myfordboy, luckygen, olfoundryman for proper and safe technique as well as great info and ideas. There are many others with good videos here as well, but those 3 have extensive video channels and have helped many of us learn a safe enjoyable hobby. Pete
Tops, You have lots of draft. Might as well have plenty as it makes life easier. I always wax my patterns as having them release from the sand as easily as possible is what I hope for. If the pattern I am using falls out after packing the drag and flipping it, I just pack it on a board that I lift along with the drag while flipping. I am glad you are not rapping laterally and are just tapping vertically. On that pattern I think I wold just give it a very few very light taps all around and then screw in a draw spike with a cross bar on it and then give just enough of an upward tap to see that the pattern had released from the sand and then would gingerly lift it out. I have just learned in the last few weeks that I had been causing myself trouble by excessIve rapping especially lateral rapping on patterns with letters. It might not help you, but I always spray my patterns with lacquer as it helps me see any defects in my pattern and does itself make tiny smooth fillets. Denis
Thanks Guys. I am painting the pattern with some plastic-safe spray and waiting out the snowy-rainy-windy weather to try a pour.
Tops, I had not thought (no PLA experience here except for a few patterns sent to me by others) about the issue of lacquer dissolving a printed pattern. Duh. So, I looked around a little after your post. Here was an interesting idea where I guy used lacquer thinner to smooth out a print. Again, no experience on my part so maybe this idea is old-hat. Or, maybe it could be somewhat useful at times. Also, I wonder if first spraying a base of shellac and then spraying with lacquer would prevent adverse interaction with the print. I have many times successfully used shellac to improve adhesion to surfaces contaminated (by me) with silicone spray. The shellac provides a good base and prevents "fish eyes" that would otherwise relentlessly telegraph through coat after coat of lacquer. I like the white lacquer as it dries so quickly (as does shellac) and it highlights any surface defects and provides a wonderfully smooth final surface. Waxing the pattern and also rubbing the waxed surface down with graphite seems to assist clean separation of pattern from sand. And, despite the prior waxing and graphite, I have had quite good luck if I needed to respray a pattern after, say, some revision work on part of it. I use a light sanding with 220 Si-C paper before spraying. But that can not possibly remove all the wax and graphite. Still, it works. Denis
Thanks Denis. I watched the video and will try that on a print. I am going to give the tuit another coat or two of paint and then wax. Is it a warning sign if you like the smell of #2 paste wax ?
I suppose it is. But, I share the affinity for the smell of paste wax. In my case it is “Johnson’s.” It smell the same now as it did in the 50’s when I remember my mom applying it to our oak floors. The good part about that was taking off your shoes and making long slides in your stocking feet! Anyway, I do like how it smells and how it slicks down a pattern. It gets lots of use in my shop—-not just on patterns. Denis
So I went in seach of graphite at the local big box lumber home improvement store. Employee greets me in the automotive section. I ask about graphite. No idea. Second employee approaches. #1 asks #2 who uses his phone to look it up and then goes to another computer to find aisle number. Walks me across the store. Little baby tube for $x. Thank him and he walks away. I look it up on my phone. Twice size larger tube for half the money (4 times less per unit weight) was one aisle over from where I asked the original question. I remember using it 45 years ago on the black plastic Pinewood Derby car wheels... I wonder where that container ended up?
The place to buy graphite is (seems odd) NAPA. They have it in a good sized bucket for cheap. Part #: BK 33005OS Line: Balkamp Denis
Also check a local farm supply store, graphite is commonly used to lubricate seed, here's an example of that: https://www.sloanex.com/ez-slide-1lb-graphite-powder-seed-flow-lubricant.html
Thanks Guys. Those prices are much better. It helps to know what else it is used for in the world. I got enough for a few patterns or 20-30 Pinewood derby cars...
I decided to run the two new crucibles through their debut in the furnace per the written instructions. I did not think really hard about doing twoin-a-row thing and so I had one hot one out and one getting hot in and so I decided to cover the hot one loosly with a metal coffee can to maybe(?) do something about the 2000 degree F delta between crucible and airl. I heard some noises later on and saw a little 'poof' come out from under the can, I hope it is something below the plinth and slate giving up and not the new crucible. Second one is mellowing in the furnace. I will give it a couple hours and go check. Last time they stayed warms for several hours.
I do not think your crucibles will be adversely affected by being out in the air immediately after firing. I used to worry about that. But after hearing from others and my own experience, I just pour my iron and set the crucible on a little metal "plinth" next to the furnace. I use Super Salamander clay-graphite crucible and silicon-carbide crucibles. Denis
