That's more or less what I did: heat the piece until the silver paint turned black and burnt off. When I worked in an aluminium warehouse we kept 6061-T6 and also 6061-T0 temper in stock with the T0 seeming more like plasticine by comparison. There's a sheetmetal fabricator next door to the foundry who was bending some 3mm thick T6 sheet for a vehicle and cracking it in the press who wasn't aware of this (and nearly killing his press). My understanding of 6061-T6 is that the plate rolling mill puts a hard skin on the thicker sheets which you can feel as a hard skin you penetrate when drilling the stuff. T0 just has a final annealing step after rolling and maybe some straightening in rollers without resizing it.
Regardless of the method, I would cast the body and head separately and attach them however is convenient. I'd probably end up putting a stud into the body and tapping a hole in the head. For the body I would make a uniform coil in the largest diameter of the snake, and place a core throughout the negative that decreases the casting diameter. I'd make the cores by using that same large pattern, placing the snake as a core for the core-box, and casting the main cores into the negative space between the void and the rubber snake. That is just how I'd do it Looking forward to how you end up solving this one! I don't wanna say it's not possible but I will be happy and surprised if you are able to just use the snake itself as the pattern.
Well, you didn't say that in your first post. I was just trying to make it as simple as possible. So if the snake laying flat as cast is the case, plastacine or some like material (as ESC suggested is your ticket for making the follower, but it probably adds a step. It won't care about the plane of the parting line. Think you would still find staking it in place to be helpful. But why bother for one copy? I think a traditionalist molder would just hold the snake in place as it was rammed, then cope down, and be done with it. Depends upon what it is you want to teach your student, but for one copy, no doubt this is what a skilled foundry man would do. Best, Kelly
My favorite material to make a follower is EXP styrofoam. I cut the foam to fit the flask. You could pin the snake to it to increase the distance between the coils. Then trace it out with a Sharpie. I use a dremel with different bits depending on how much material is to be removed. Rasps are good for deep removal, sanding drums for light work. I don't fret with getting it perfect because a slight overcut on the width is just a flick to remove a bit of sand. You would probably need to place it upside down to get the flat surface.
From post 1: “I plan to cast it in sand using either petrobond or sodium silicate sand. The problem I have not yet figured out is how to part the cope and drag. The model does have a part line that is easily seen. But, laying flat on a surface the snakes part line varies from 1/4” to nearly 3/4” above the plane of the table.” From post 15: “Sure, I could cope down, but that would be tricky given the relatively close spacing of the coils. And then there is the need to repeat that work a few times until I get the gating and runners right. By pinning the snake and using bondo or POP, I can at least start at the head and spread the coils a bit to provide a bit more room for shaping the Bondo on the outside of the coil. Then as I progress I can place the next portion of the coil in position---nearer the prior coil and do the Bondo. Once I have a follow board it will be relatively easy to mold subsequent sand until I get it right. I will probably make more than one once I get it working. I will be using PBond---actually Kbond and Pbond mixed per a prior thread. Coping down was the first strategy I considered.” That is an interesting idea I had not thought of. Sounds like it could work pretty well. That along with Mark’s pointing out that the coil can be bent post-casting may be a good approach. Denis
I have a half dozen foam followers that I use frequently. It usually takes a half hour to make them. If I cut a little too deep, painters tape makes a good shim to adjust the parting line. Quick and easy.
A cake of soap rubbed on the metal also works well as an indicator; stop heating when the soap turns black. Works on any grade of aluminium in my experience, Cheers Charlie
I got started on the follow board this morning. I used a piece of OSB for the backer and got out my can of Bondo and a putty knife and a small shop-made scraping tool. I waxed the snake with Johnson's and sprayed it with silicone. Before I got started I had entertained the idea of needing to pin the snake down to hold it in postition. But I decided to just use the blobs of rapidly-setting Bondo to stavbilize the "specimen" and that worked just fine. Getting started Even the kindest observer would not describe my technique as "neat." The little pusher at the top of the frame was quite handy in this operation. It is actually a scraper I use on fillets, but today pushed Bondo into awkward areas. The snake pulled easily from the Bondo as the wax and silicone prevented adhesion and the flexibility of the snake allowed it to pull out of some areas where the bondo partially encased the snake. Here is the factory mold parting line easily seen in the bondo (as hoped). I will fill in the spaces between the coils with POP and then sand down to the part line. That should be the right level for the casting [arting line as well. This was a fairly straightr-forward process. More updates later. Denis
I filled in the spaces between the coils with POP. After the POP sets, I’ll sand Dow to the part line. Denis
Would it be worth putting an eye ball friendly ball on the tail tip or maybe bending it into a loop after casting for when the kid's older brother frisbees it into someone's head.
Mark, that’s not a bad idea probably. If I can get the tail cast in the first place then I think I will try your heating method and see if I can bend it in such a way that’s a little less likely to poke somebody straight away. Good thinking.
I use clay to do a parting line...wax it really good and pour a plastic negative and make a positive from that....gives a good parting that can be molded. Down side is it takes a lot of plastic.
Hello Denis, How went the snake? I hate coming to the party late but for what it's worth, this is how I would handle it. I am going to guess that the beastie is about 3ft. long unwound? No matter really. Take a 4ft. x 1ft. x 2" piece of high density Styrofoam. (The blue stuff). Stretch the snake out in a reasonably strait order along the centre line of the foam and pin it down to the foam with turkey sewing needles from your local dollar store. Don't worry about the holes in the snake as they will heal over. With a felt-tip draw a line along both sides of the snake onto the foam outlining it's shape while leaving a little margin for jointing. Remove snake. With a Dremel, remove sufficient foam to allow the snake to sit, in it's stretched state, approximately to its centre/parting line. Skewer the snake once more into the cavity. You will need to trim each of the needles to a less than the total thickness of the foam and snake. You may even want to put the pins into new locations. Again the rubber will heal over. (I just typed heel over so have to watch my gramma). When secured, joint the snake using green sand, Petrobond (nice) or modelling clay. Knock up a quick cope and drag flask from whatever material you have to hand leaving sufficient headroom and elbow room for running and gating. Don't worry about pins if you leave enough room to scoop out half a dozen golf ball sized indents on the mould face, these will form a male/female self centering dowel system for closing out. You mention you have access to sodium silicate sand? By all means use it. Ideal really as it means that you will be able to mould the mouth cavity without losing to much detail. Ram up, cure, roll over, remove foam jointing board. Remove needles. Leave snake in sand. Titivate the joint a little where grossly out of line. Remember we are dealing with a rubber pattern which should roll out of a somewhat miss-jointed cavity. Lots of leeway. Scoop half a dozen golf-ball sized "cups" in the mould face remembering how you intend to gate and feed the casting. these will form the female locating dowels. Place the second part of the flask in position and repeat above. Remember that there should be no need to "pin" the snake down as it should be locked in the hardened sand. After setting, gently part the flasks. The snake may stay in one half of the mould or it may decide to partly separate. One way or the other it will leave! Using a large masonry bit in your power drill, cut runners, risers and gating to taste. You may want to be a bit generous in this as we are going to cast it in a zinc/aluminum alloy known by various names. KM12. Ilzro 12, ZA12 etc. All commercially available. Basically this is a 12% aluminium and zinc alloy and the reason for using it I will outline in a moment. After cooling, clean up the casting to taste. This is much easier to do on a linear piece than when coiled. Now for the fun bit. You will need. A row of firebricks laid end to end. 2 high output propane torches and gas supply. A pair of asbestos mitts but there is probably a modern alternative now. Instructions: Lay the snake out along the length of the firebricks. Apply heat via the propane torches, evenly, along the length of the snake, Be careful with the tail end as this could melt if heat is too concentrated. You will reach a critical but fairly broad temperature window where the alloy becomes "plastic". At this point, using your Superman gloves. you may pick up the snake and coil it into the required shape or form with fracturing or tearing. If you want to test its limit, you could tie a knot in it! As it cools it will lock in to it's now re-formed rigid state. You could if you wish set it into a Cobra like pose, sitting on it's tail. I used this phenomenon many years ago when making parts for laboratory equipment which would have ordinarily required a really, really odd jointing challenge and much added cost. Thinking back, it was a two man operation, permanent mould, one man casting, removing part and handing it over to the second operator who slipped the still hot casting into a frame and tapped it with a lead mallet into it's new and now complex shape. Brilliant! Now thinking forward. It may be handy to have a second pair of hands when twisting the snake. I wish that I could give you even a reasonably accurate temperature at which this feature becomes active. No records of course but obviously fairly soon after solidification but as I say, I think the window was fairly wide. Maybe the horse has bolted and this idea is redundant but file it away for another adventure. There is much you can do with metal. John
John, thanks for your detailed instructions. It sounds like an interesting way to approach the problem and one that would probably work out nicely. As it stands I made a follow board out of POP and Bando. I varnished it with some epoxy with the idea that I may want to use sodium silicate on it. However I was pleased to find that ramming this up with Petrobond seems to be working quite well at least acceptably well If I were trying for an absolute perfect rendition of the snake I think your method would probably provide that. As it is, this is really for a nine-year-old girl and I want to be able to have her see the process and actually participate in the process of ramming up the mold. Right now I am melting aluminum and hope to be able to cast the mold that I made in a few minutes. I say hope to because right now one of a heating element connections in my kiln has failed and I cobbled back together a connection hoping to salvage the melt which was about 2/3 of the way complete. The failure of the connection is largely a failure of the maker—-that would be me. I should have used a better form of connection and will make the correction as soon as the melt is complete. Added: Well the kiln held together to finish the melt. Yes!! Here is the first attempt: Poking his little head out of the sand: Denis
