Aluminum Flask

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Harry
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Re: Aluminum Flask

Post by Harry »

Lookin' real nice David, always love it when a casting comes out of the sand near ready to use. The cleanup and other work to finish out parts is one of the next steps for me to set up. Finances have slowed me down on expanding on the shop and current machinery, I want to build a couple or three small cnc mills so I can set them up and do several operations on a lot of parts at once by moving them from one machine to the next.

Doesnt look like going a little hot on the temperature has hurt you at all on those castings. Notice and gas inclusions at all when you clean them up? That seems to be my concern when pouring at a hotter temperature, I believe the more you overheat the more likely you are in seeing them. I suppose the other component would be in shrink since the metal would shrink more from a higher temperature but then it would feed until it began to solidify right?
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dallen
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Re: Aluminum Flask

Post by dallen »

I did see shrinkage in the top of the sprue which pulled down pretty good on the one I cast yesterday and the one today. I don't think I'm actually over heating that much at 1400, I know I was at 1400 yesterday when I shut the burner off because I checked it with a probe from Mifco that I have, on that fluke indicator I won off evil bay. I have been really lucky in the amount of flash around the edge on these last two castings in that there really isn't any. The casting yesterday I had to work on pretty good with a file but that was because I cut the vents and runners off about an 1/8" out from the actual part, the one today I was careful and cut them off flush or almost so. I actually think that today when I poured that I may of been a little colder then yesterday.
I have been pouring hot because my muller sits outside and even if it was in the shed I don't have heat out there so the sand is cold as all get out even though it may be 50 degrees outside. and the one reason I ran the temp up yesterday was because of the pour that I did before yesterday I had fired the big furnace on oil and the temp got away from me but the part came out looking great so I said I would pour the rest of these that way. the big problem is that the middle of that pattern is only a 1/4" thick so its gotta be hot to fill it up and with the handle lug on the outside and the grip strip on the other I have added even more metal to the pour so I don't really think that around 1400 is too hot, and i am using car wheel for my raw stock.

I know I like it when I turn the crucible up and can pour till I can see the smoke come out the vents from the sand burning, today the metal was fluid enough that I had it jump out the vents then suck back down inside about half and inch.

My muller which is were I normally pour when only doing one mold as I don't have to man handle it around then sits sort of un-level because of the ground, so I always turn the sprue to the low side and as you have seen in other pictures I always gate these flask panels into each end of one side and two vents on the other side I have found that to be the best setup for me. I'll post up a picture of this last panel later tonight supper time now

these are as it came from the mold the only thing I have done is to cut the gating off as you can see I cut it as close as I could to the actual part on this casting didn't want to have to file as much as I did yesterday.

The two little bumps you see on top of that rib is actually the heads of the brads that pin the rib to the pattern when I flip the drag over to ram the cope.
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David and Charlie aka the shop monster

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F.C.
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Re: Aluminum Flask

Post by F.C. »

If your sand has a compatible mix to the temperature of your melt, the temp you described (especially about the riser fill and how it settled) suggests to me your temp was perfect. That said... Depending upon your sand grit combination, excess moisture AND a combination of too much bond (or possible too hard of a pack) could cause those gas inclusions. Sand inclusions is indicitive of too dry of sand, too course of sand and insufficient binder, or too light of a pack, or not enough draft on the pattern which causes sand molds (at their sharpest edges) become too weak. Plop the drag onto the cope too abruptly, or fuss with it down the guide pins too much (or fail to adequately blow out your sand mold before closing) and you'll vibrate lose those edges and they become captured in your pour. Curious... did those molds sit overnight or more before you poured them? Moved them several times before the pour? Inquiring minds need to know... haha :D

The best tell tale visual for Aluminum being up to proper pouring temp is a uniform "pink" hew to the melt as well as the crucible. If you dial back your furnace temp the same hew will appear on the furnace wall and you can hold the melt at that temp for as long as you need. Add more metal and you'll have to throttle up the furnace again. Anyway... sorry to ramble. Another thought here, do you purge your melt prior to pouring or just go from scrap straight to cast?

Shrinkage puckers is due to poor design in how you intend to fill the mold cavity and expect (more like design) the way it's going to chill. Every shape, every differnce in size, every thickness, AND combinations thereof, all have their unique way in which to ideally fill the cavity with metal and have it chill exactly as the shape it was poured against. That's a lifetime learning experience.. :lol: I've got 20 years doin it and I still have to question and plan for contingencies. Maybe we can all sort this out with ya and learn somth'n! ;)
dallen
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Re: Aluminum Flask

Post by dallen »

I take it that your talking about the black spots that are along the rib, yes the edge pulled off of that when I pulled the pattern piece out of the sand. the mold was rammed up about 30 minutes before melting and pouring. as far as I know there is only one inclusion in that casting its on the outside face and can't be seen in the pictures.
The sand was oil bonded sand that was mixed up sometime around august and has been in use since, yes I probably rammed it up too hard but it works I don't worry about venting thru the sand I put vents in, this is a thin piece and I have had a ton of problems getting to where I am with casting these. and now I'm fixing to open up a whole new can of worms cause I'm fixing to make a pattern that is 4 inches longer then this one.
The shrinkage that I spoke of on the sprue where the melt showed shrinkage was probably down about 3/16" if that.

here is a picture of the way that I gate this part, it works if you know of a better way I'm willing to try it.
This picture is actually the pattern the parts in the previous post was made off of this was before I modified it to have the handles which is where the alignment pins will go.
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Jammer
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Re: Aluminum Flask

Post by Jammer »

Do you tip the flask up a little while you pour. I have had good pours buy lifting the riser end a little so the metal flows uphill. Seems to help fill the thin parts.
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dallen
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Re: Aluminum Flask

Post by dallen »

The muller, which is where I do most of my pouring at keeps me from lugging the flask around sits at an angle, so I always turn the sprue hole to the low side, which gives it a slight up hill pitch on the fill maybe half and inch from the low sprue side to the high vent side. if I am doing cast iron I move the flask over by the big furnace where I have a raised grate which I set them on to keep from having to go all the way to the ground due to a messed up lower back. you would be surprised how much help 16" is.

The panels have been coming out great, I have been getting full pours although the last couple feel a little rough, for the application that they are being made for I don't see that as a problem, and it is probably being caused by me pouring hot metal into cold sand. This can't be helped as my muller and the sand that I am using is outside or in an unheated storage shed. I guess I could if it was absolutely necessary put the space heater blowing under the muller to warm the sand up with. The sand actually acts dry when cold, it rams up fine, but it has this dry look and feel, once it has had some metal poured into it and warms the mass up it goes back to its regular look and feel of oil bonded sand with just a little too much oil in it.

F.C. was asking about the mixture of my sand. This sand is a mixture of two different batches of oil bonded sand that I mixed up, it was originally mixed with a 50 lb bag of quikrete play sand with prtrobond powder, with oil and Methanol added as a catalyst. I then added some 100-120 grit silica sand that I had in a bucket that I wanted to use up so I added this two or three scoops at a time ( I have the same Scoop as Harry) till it was all mixed it. With this blend I have had surface finishes from the finish that I achieved on the plate that I poured yesterday to almost mirror like with a smooth finish that will show finger prints.

My gating is as can be seen in the photo I posted early this morning is simple I cut the sprue, then carve a basin for the metal, normally I just carve a somewhat circular runner with it ending at the side of the pattern/mold, with it running into each end so I get max fill rate. I have tried using just one gate in one end, and with it into the middle, and have tried with no vents and with only one vent. This setup works.

I guess I could wait to close the mold just before pouring and take a torch and heat the mold face or spray it with Alcohol and set it on fire, and close as soon as the flames go out. I did try spraying with Alcohol with graphite in it but it clogs the sprayer so it won't work. There is a line of what looks like sand inclusions along the rib, this is caused by the rib being a loose pattern piece with only two small brads to act as dowels to hold it in place. I have been thinking of covering the pattern with saran wrap then installing the rib then using some wax fillet material to make a radiused edge on is so that when I remove it from the mold it isn't so apt to tear the edge of the depression left by it. yesterday even thou I helt it down with one hand while I packed sand around it to hold it in place ( the one poured on Wenesday cocked over sideways), it stayed upright like it was suppose to,the raised up and some sand did manage to work its way under the edge, this broke off when I pulled it out.

The mold that I made yesterday is probably one of the best molds that I have rammed up since I started doing this, except for having to machine the one end flat where it has some draft on it the part could be used if all of them were of the same quality of casting as this one by simply cleaning the edges with a file.

I am hoping to get a casting out of this pattern that I can keep an use as a master for further flask to be made off of.

maybe this summer seeing as how it looks like I will have plenty of time I can expand on my foundry area, by maybe moving things around to its in more of an orderly line from start to pour.

F.C. most of my sand is approximately the same grain size as the sand that Harry uses, he sent me a sample and side by side if I didn't tell you which was which you could not tell the difference between them. Most of my problems I have are because of lack of experiance in not only pattern making (I hate wood working) to molding, to melting and pouring all go back to not enough time getting hands on, I think you said that you have 20 years I need to borrow 15 if them I only been trying for almost three now and I don't get to cast as much as I would like, right now due to the weather being so uncooperative with it too cold one day to raining the next to the sun shining but the wind blowing 30 MPH.

Sorry for such a long winded post, please feel free to post any thoughts, solutions, help comes in many forms as they say.

David Allen

Happy Holidays to all and a New Furnace to some.
David and Charlie aka the shop monster

If life seems normal your not going fast enough" Mario Andrette
F.C.
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Re: Aluminum Flask

Post by F.C. »

Your sand (other than being petrobond) sounds almost mirrored to mine. Good mix of grit ya have there. I have had no experience with the oil based. My experience has been exclusively with water/clay/corn flour based. I, too, can get almost mirror surfaces if the conditions are absolutely in sync with my pattern and gate design.

Something to think about here, David, is "directional solidification". Every pour of melt, no matter what cavity it's in will have a natural direction in which the metal will chill based on the shape and varying thicknesses. What you need to do in your gating is provide not just for the fill but to also provide a little extra to assist a thicker mass to shrink without tearing itself free of a thinner section and to assist with your theory of designed directional solidification. You can control chilling by keeping something hot longer or quicken a thicker area to freeze by incorporating what's called a "chill" into the sand mold designed to pull heat out of that thickened cast area faster to assist it to chill quicker and in sync with an adjoining thinner section. There's also preheating the mold as you already have experience in doing, as well as mold manipulation techniques as you've done in elevating one end to force the metal to flow uphill with less turbulance. In a sense, and I'm sure you've already come to this conclusion, often a good quality cast will incorporate a balancing of many different factors together to achieve that perfect cast... of that one particular shape, at least. That balance differs with every different shape you encounter.

But hey, that what you cast there is damn fine work and is perfect for the task it's intended to serve. You got excellent skills... the experience is what you lack and only hands on application will educate you more and add to your knowledge base. Keep a running diary is my method of internalizing new frontier research. I log EVERYTHING down as parameters to conditions, materials, and methods at the time I first attempt the pour. That which I alter, I log that attempt's conditions, too. I write those diaries into surveyor's field note books (they are convenient, durable, hard plastic covers) and catalog them into generic shapes, i.e., circles, squares, rectangles, triangles, etc., with sub sections involving thick, thin, wide, long, etc., etc. These come in handy when I encounter something new and have to theorize a method to cast its shape. And whatever i do to accomplish that new shape, that, too, goes into the book. Eventually they will gather dust but they will forever come in handy at a moments notice. But nothing beats hands on application and sheer determination to get beyond an impasse. ;) i wish I lived close to you to be able to visit and see what it is you have going on. I can diagnose this stuff much easier holding teh cast in my hand and reading the metal, and seeing the conditions in which the cast was made. But, when I do see something that draws my attention I'll definately speak up.

This stuff is addicting, ain't it!! :lol:
dallen
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Re: Aluminum Flask

Post by dallen »

I try is all I can say, and without casting metal into molds I can read all the books and listen to people all I want to and its still not going to make me a metal caster or pattern maker. like my old dead daddy used to say ya gotta get your hands dirty to learn.

and yes directional solidification can be very important in a mold, because if you don't build the pattern right and have thin sections and thick sections placed in the wrong areas, the casting can tear itself apart, thats not the problem that I have had with these plates basically the problem has been that I was just pouring too cold, and the mold would not fill before freezing. of course warm sand helps but its kinda hard to heat the muller up when its outside and its 38 degrees and I want to cast.
I have a probe so holding temp is no problem if I will take the time to get it out and plug it in. I guess you could say the biggest problem is that I don't take notes I know I should, (should do it with my coffee roasting also) but don't. Even on the job a note can save your ass.

My casting up to date has been pretty simple objects except for when I set a goal to cast the fan blade that cracked on the motor to my mill.
Image

I wasn't able to do that fan blade till after I finished my muller and I believe that was done with greensand that had been run thru the muller. I think that for someone getting into this hobby the first thing they should acquire is a Muller, or someway to mechanically mull there sand. I build mine long story for later.
I tried to cast the blade out of a 60 mm computer fan, I didn't quite get a whole blade before I stopped because I went a different direction on my burner.

I wish that there were more accomplished casters in the area, there are a few, one I converse with is into building a Bigboy Locomotive and is casting all the parts he still has a long ways to go but is getting there.

I plan to cast today, I have one more of the flask panels to make of this type,
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poured number four this afternoon, here's the picture before knocking it out of the cope. should of taken a photo of the top of the sprue but it showed no shrinkage, the metal was at 1420 when I shut the burner off and was probably at 1350 by the time I got done degassing and pulled the crucible and skimmed the dross off the top, poured like water.
poured number four this afternoon, here's the picture before knocking it out of the cope. should of taken a photo of the top of the sprue but it showed no shrinkage, the metal was at 1420 when I shut the burner off and was probably at 1350 by the time I got done degassing and pulled the crucible and skimmed the dross off the top, poured like water.
David and Charlie aka the shop monster

If life seems normal your not going fast enough" Mario Andrette
dallen
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Re: Aluminum Flask

Post by dallen »

I started and finished this back in December but never got around to finishing this thread up so here is the picture of the finished flask with the alignment pin.

As you can see if the photo I goofed on the handle/pin bases. when I reworked the pattern in one of my not so finer moments put the handle in the middle of the flask side, wrong this makes the handles to far apart to use. What I should of done was to make the pattern so that the handle could of been put on either side, and in and inch from the edge which would of set them 2 inches apart and would of worked a lot better. So if things permit its back to the pattern room for another go at this.
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David and Charlie aka the shop monster

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mite5255
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Re: Aluminum Flask

Post by mite5255 »

dallen wrote:I started and finished this back in December but never got around to finishing this thread up so here is the picture of the finished flask with the alignment pin.

As you can see if the photo I goofed on the handle/pin bases. when I reworked the pattern in one of my not so finer moments put the handle in the middle of the flask side, wrong this makes the handles to far apart to use. What I should of done was to make the pattern so that the handle could of been put on either side, and in and inch from the edge which would of set them 2 inches apart and would of worked a lot better. So if things permit its back to the pattern room for another go at this.
Hey Dave they still look damn good ;)
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