Pattern/Rapping fail Sailboat Part

Discussion in 'Sand Casting' started by Tops, Jun 12, 2022.

  1. Tops

    Tops Silver Banner Member

    Thanks Denis. I started with a tounge depressor and an old pallet knife. The pallet knife felt good in the hand but it was not fully radiused. I grabbed some discarded steel banding from the dock and will try to shape some better tools.
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  2. Tops

    Tops Silver Banner Member

    I made some tools from the steel banding strap mentioned above. Cut with a tin snips to approximate the leading half of the diamond on the pallet knife, filed to various radii, sanded. I also cleaned up the 30-something-year old pallet knife with a full radius. The black ones can scrape a little (did not draw and burnish as scrapers, thanks for the video, just squared up and deburred) and spread, the pallet knife just spreads unless I use it to pick at something. I like the add of a drop or two of the Bondo 402 polyester resin into the Bondo 262 filler and its cream hardener. I laid out 4-5 small smears (teaspoon each?) of filler on a piece of plexiglass and added resin and hardener into the first smear. Once the mix started clumping on the part, I wiped off the tools and mixed the resin and hardener into the next smear. Finding it all to be relaxing after a crazy week 'at the office'. Recycled Amazon mailer under the cans to keep spills off the bench.
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  3. Melterskelter

    Melterskelter Gold Banner Member

    Those look useful, for sure. For a quick and very dirty scraper edge, just place one of your spatulas against the spinning grinder wheel more or less perdendicular and let it raise a burr along the edge. Then use that burr as a cutting edge to smooth the set or partially set Bondo. It will cut a shaving of Bondo. Kinda nice. Dulls pretty fast, but easy to renew. At some point do try the burnishing idea on the edge of a scraper. I use the stem of a carbide end mill as a burnisher---perfect for the job. The fine sharp burr really does a satisfying job of shaving off Bondo, paint, or wood.

    Denis
     
  4. Tobho Mott

    Tobho Mott Gold Banner Member

    Not trying to stir the pot, but check Ammen again. I just had a look myself just to make sure I'd seen it somewhere other than Gingery. His sand casting handbook does refer several times to using greensand cores as opposed to dry sand cores, formed simply by ramming up the cope/drag around the pattern.

    From chapter 15: "Practice, practice. When you are satisfied that you can cast the disc, move on to a simple pattern that leaves a green sand core, then a dry sand core. As to your foundry, it is a progressive thing, as you learn and get more involved you also add equipment, tools, patterns etc."

    I posted a pic of one here a while back that I referred to as a hanging core. "Huge lump hanging in space" is certainly accurate as well. :)

    Jeff
     
  5. Tops

    Tops Silver Banner Member

    [​IMG]

    That apple bowl mold was impressive Jeff, thanks for the reminder!
    Almost 100F here and I have not sanded since yesterday's application. I did break another piece off the pallet knife using it as a pick... :(
    If/when it cools off I will have to make a banding steel tool to replace that size radius in the lineup.
     
  6. Monty

    Monty Silver

    Old model maker trick. I keep a bunch of pop-sickle sticks of various sizes on hand. Use adhesive backed sand paper to make sanding sticks. You can use a disk sander to shape them however you like.....works well for getting into deep patterns that have slots for ribs. I wind up making the inverse pattern, for a rubber mold, to make a plaster mold....to make an aluminum part. It gets confusing! But the pop-sickle sticks help with smoothing the forms. The rubber doesn't stick to plaster, but it has to be smooth! So all those deep grooves must get polished somehow. I sand down to about 800 grit and then solvent smooth to polish. All to make a plaster core!

    Monty
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  7. Melterskelter

    Melterskelter Gold Banner Member

    I looked back at that post and I do not see the word core in it.

    Here is what you said: "Scammed a pic from Saturday off the school's social media... This lady's mold of a dollar store apple shaped bowl turned out the best casting of the day." unless you are referring to some other post.

    It could be that Ammen used the term core in an archaic way as well (can't find my copy right now.) and so if I misrepresented him, my sincere apologies. I do maintain that using "core" when current standard usage would be to refer to a sand mold as a "mold" will do little but cause confusion as the the American Foundry Society Glossary of Terms clearly indicates, as does the US Navy Manual, and all the contemporary foundries that offer such information online as well as Wikipedia etc, etc, etc. Is there a contemporary exception?

    Denis
     
  8. Tobho Mott

    Tobho Mott Gold Banner Member

    That's the post with the pic. I called it a hanging core a couple posts later, never realizing this was archaic usage.

    I agree completely that anyone hearing "core" with no further context would assume it meant a hard piece of sand made in a corebox.

    If you do check your book, Ammen talks about these greensand cores more extensively in chapter 7 where an example of molding a shoring washer is explained.

    Anyhow, whatever you call sand features protruding from the cope or drag, when they are narrow I also have found them easier to draw patterns from without breaking them off by packing them with my fingers before ramming up the rest of the mold so the rammer can't make them quite so tight. Ammen suggests pushing a headed nail into them to keep them from breaking off.

    Jeff
     
  9. Tops

    Tops Silver Banner Member

    I have been working the pattern with some talk and pictures over here:
    https://forums.thehomefoundry.org/i...d-for-finishing-fdm-3d-printed-patterns.2267/
    and I have tried the spot putty both as an airbrush medium and as a spot putty.
    Some other finishing methods were mentioned there too like Elmer's Glue, conventional primers, and 2-part primers like Evercoat.

    This pattern is challenging with the less than 3/4" (19mm) between the vanes that hold the sheave (pulley) for the halyard (rope) at the top of the stick (mast) it is hard to get fingers, putty, Bondo, paint down into there. I am wondering if this should have really been done as a discretely cored mold or if the patterns should have a longitudinal split as well as as the regular split at the parting line.

    I am feeling like this needs to proceed/conclude- as in it needs to get waxed, graphite-ed, parting dusted, rammed, and even cast... It it is much better shape than it was going into the flask the first time with bigger/better fillets and better surface finish. Still not a show car but that was never the intent.

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  10. Tops

    Tops Silver Banner Member

    top_o14_pour_comp.jpg

    Got to try pouring this today, much happier with the results than the first time. Between the bigger fillets/smoother pattern and a little more mindfulness ramming up the flask it will not need the remedial machining of the first one. Used some of @FishbonzWV coaching on the gating. I decided to 3D print a gating piece and wrap it around the part as the flask is small (!) s as to make it with my Petrobond. I did fiddle with the inexpensive Amazon 4" Type K thermocouple with a graphite sleeve and HF multimeter with a 'K' thermocouple input. First reading topped out at 680 C. Re-started the furnace and gave it a couple minutes. Second reading was slowing down at 720 C so I went for it. I did have a issue pouring by starting too high and pinching it off for a moment. I think I need to trade my tall lead diving weights for some flatter steel plates. From a pattern prep standpoint I'd probably skip the putty + acetone spray and use Bondo first and save the putty for small blemishes. There was one spot where the part chipped down to raw PLA+ pattern during the ramming process but I thought I'd do more harm trying to clear the chip, which was on one corner of the 'horseshoe' that goes into the mast.
    Stats:
    Total new pour 19.2oz (544g) ,720 C (1330 F) , recycled cast aluminum tooling plate 5083-ish
    New part 8.3oz (old part is 7.9oz and would be lighter with more of the 'muffin' removed)
    Gating 1.3 oz
    Basin 5.2 oz
    Ingots 4.4oz

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    The laser-burnt graphics on the handle of the 'flyswatter' thermocouple, not visible in pic. I did the Navy one after @HT1 noted that the 'Space Cowboy' only knows melt temps and not casting temps, and as a note in general to refer to the USN foundry manual:
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    This casting working out was a high point of the weekend after another boating project went south...possibly messing with a week's plans later in the summer and scrapping a bunch of work done previously.
     
    Last edited: Jun 26, 2022
  11. FishbonzWV

    FishbonzWV Silver Banner Member

    Looks really good! Nice part.
    About that runner...I don't understand the reason for the 90*. Looks like it could have been sprued on the end of the stick. Also, put a seashore on the end vs a seawall. Think about what wave does when it hits either one.
     
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  12. Tops

    Tops Silver Banner Member

    Thanks 'Bonz.
    I was concerned about being close to the flask and burning the wood hence the first 90 in the runner to put the basin and sprue more internal. I probably should get a few more pounds of Petrobond and stop worrying about having enough.
    Love the seashore/seawall analogy, don't want any breaking surf or reflection waves in my molds.
    There is a tiny well or expansion at the end of the runner, not sure if this was the right countermeasure.
    Took the parts to work for show and tell!
    :)
     
  13. Melterskelter

    Melterskelter Gold Banner Member

    Very nicely done. I agree with Bonz' comments and would have myself skipped the termination of the runner and just had a sprue ending in a short runner spanning the gates you made. But, then, you got a great part. So, what you did worked fine and what I would have done would have resulted in no better part. It would have been just a little simpler.

    With respect to weights: I see them used all the time and they do work. But, I never use weights. I lock the cope to the drag mechanically, usually with a couple of wood tabs that serves as a guide pin and also gets an additional srew to lock cope to drag. A drywall screw or GRK torx drive serves well. I usually do nothing more to reinfoce the cope sand though, if worried, I also occasionally place a couple of wood 1x2" wood bars across the top and screw them to the flask walls with drywall or (better) torx drive screws. I use this style screw over and over and over and find them to be a lot better design for cope and drag asssmbly and general construction use. GRK.JPG

    I like the secure compact package that results from locking cope to drag and using the screws and bars. One caveat: I usually drive the screws using my drill rather than impact driver as I worry the vibration from the rattling of the driver may flake off sand. When disassembly time comes, I yank the screws out with the satisfying rrrrrrrrrppppp of the driver.

    Denis
     
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  14. Billy Elmore

    Billy Elmore Silver

    The term greensand core is commonly used in most foundries that I have been in contact with. It generally suggest a protrusion in the mold area that will be encapsulated by metal. An example would be our lids use a greensand core made by retracting the handle out of the mold and not by placing a core. The sand left between the handle and the top of the lid would be referred to as greensand core. Not saying it is right or wrong...as long as I know what we are talking about you can call it whatever you like.LOL
     
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  15. Melterskelter

    Melterskelter Gold Banner Member

    So, Billy, if I understand (not at all sure) you are saying the eye in the handle is made by drawing the pattern out of the sand leaving a raised island of sand which forms the eye and the same thing could have been accomplished using a formal core placed in a core print. But forming this way as a continuation of the mold was less work and quicker? And in your foundry people refer to that island as a core?

    Denis
     
    Last edited: Jun 27, 2022
  16. Tops

    Tops Silver Banner Member

    I like that sound too!

    Wondering if @Billy Elmore could hook us up with some custom cornstick pans that say thehomefoundry.org in the kernels so our ingots can represent :) ...
     
  17. Melterskelter

    Melterskelter Gold Banner Member

    Until this post I had happily forgotten about the discussion of the definition of a core. And it also caused me to remember Tobo talking about Ammen referencing a green sand core. I did a little looking and located my copy of Ammen’s A Metalcaster’s Bible . Ammen is pretty unequivocal in his definition in Chapter 8: 8C0DB23E-6E37-4F0B-B8AC-5FC21856316C.jpeg

    And one might guess Billy is talking about something like the green sand core illustrated by Ammen
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    I guess the idea in the page 149 image is that that protruding sand core was something usually made with an added premolded conventionally made core. But in this case was formed with the drag on green sand, thus saving the core being formed in a core box and placed in a core print.

    Hopefully, there is little confusion over what we mean by “core” and “mold.”

    Denis
     
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  18. SRHacksaw

    SRHacksaw Silver

    Correct. Core means one thing. Greensand core means another. That kind of language construction is called using a modifier.

    You can define "apple" , yet be ill advised to eat a road apple.
     
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  19. Billy Elmore

    Billy Elmore Silver

    Yes sir...pretty much any place that leaves a raised area in the mold is referred to as the core...or core side vs cavity side. In our lids the handle is retracted from the top of the lid inside the pattern, leaving the cavity of the handle and making it possible to draw it from the mold. We make four at a time every six seconds...cores would not be nearly as efficient....the only drawback is mechanical failures....and they happen often but are usually just simple quick fixes.
     
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  20. Billy Elmore

    Billy Elmore Silver

    LOL...it would be easier to make them at home...especially with a 3D printer. Anyone can have them made here though, if they can afford them. We just made Guy Fieri his own custom logo skillet when he came through last week. High value stuff.... had to be walked through the whole process. It was a cool knuckle sandwich logo. I have actually thought about making some logo skillets for my family with our crest or something along those lines.
     
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