Mixing up K-Bond Sand (Similar to Petrobond)

Discussion in 'Sand Casting' started by Melterskelter, Jun 9, 2021.

  1. Tops

    Tops Silver Banner Member

    I worked on the K-Bond project a little more...
    1. Detoured to make a star pattern aka 'boat jewelry' and then decided to make 2 and put them on a match plate so I could play more indoors with CAD/CAM stuff (4 F/- 15 C today outside, getting colder tomorrow...30 F / -1C in the garage where I was painting/melting/casting, molds rammed indoors.)
    2. Converted my first three ever wooden flasks to use the match plate (extra pins and holes). Patterns are as-printed PLA .16mm layer height with 1 coat spray lacquer. Used the riser and runner from the first part to be a trap for the 2-up match plate.
    3. Tried ramming it up with my green sand too, only to discover that it still has low green strength even after the last mulling.
    4. Rammed it up in P-Bond and K-Bond, cast, results below. Melt went well but I miscalculated aluminum, had just enough for the job but would rather get an ingot at the end. Not a fan of the red flecks from the P-Bond sand left on the parts.

    Thinking I need to mull longer or add more clay to the K-Bond. Does that look/sound right? Or more polar agent? Seems I had a similar situation with green sand once where is got the 'sticky' look.
    As far as smoke goes they were about the same. I remember the P-Bond being on fire but not the K-Bond. Ended up opening the garage door and dragging them outside.

    tops_kbond1_matchplate1.jpg
    tops_kbond1_smoke1.jpg
    tops_kbond1_stats.jpg
    tops_kbond1_textture1.jpg

    PS Stats from the pour. My basins were much larger in real life than what I fudged into CAD...
    Description ........ Grams .... Ounces
    Parts (2 stars)......... 91 .... 3.2
    sprue and cup........113.... 4.0
    gates and risers........48.... 1.7
    total ..................... 252.... 8.9
    calculated .............. 174 .... 6.1
    shortfall..................-78 g .... -2.7oz
     
    Last edited: Jan 30, 2023
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  2. Melterskelter

    Melterskelter Gold Banner Member

    Those castings look really good.

    Do you think the risers were needed? You might try one set without. That would save you some metal. You might not, on the other hand, want to mess with success.

    Denis
     
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  3. Chazza

    Chazza Silver

    Nice castings.

    I deal with thin aluminium all the time and I think your runners are adequate enough to act as risers,

    Cheers Charlie
     
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  4. Tops

    Tops Silver Banner Member

    Thanks Charlie, thanks Denis.

    On the P-Bond one it does look like the 2 risers above the parts collapsed a little like 1/32" or .8mm. Since they are 3/4" or 19mm high and diameter... they are quite a bit too large. The main biscuit is .1875" / 4.5mm thick and the star 'towers' another .25" / 3.2mm above that. It does not look too bad to de-gate; I will use the 'good' bandsaw at work that cuts our plate aluminum.

    Any thoughts about the surface finish? It would be nice to be able to 'spec' smooth or textured and get parts to come out the preferred way intentionally.
     
  5. Melterskelter

    Melterskelter Gold Banner Member

    As to riser collapse, just for arguments sake, did the riser collapse because it fed the casting or did it collapse because it is a chunky casting itself?

    As to finish, all I know is casting cooler results in a generally shinier surface. Adjustments for very fine sand grain is probably not practical for most of us. Making sure there is not too much parting compound can help.

    Denis
     
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  6. Tops

    Tops Silver Banner Member

    Hard to say. I redid the match plate with smaller risers and a little more access to de-gate. I don't have an immediate use for the pieces, so I have not tried them again. I still feel weak when it comes to gating and I feel that my solutions are relatively clumsy and work more by accident rather than forethought. I appreciate all the tips I get here!

    I added a little more Bentone to my K-Bond (going from 6.5 to 7%) but it still feels a bit oily compared to my outsourced P-Bond. Not sure if I need more and/or a better polar agent than denatured alcohol and/or if I messed up with the low dollar synthetic 2 cycle oil selection.
     
  7. Melterskelter

    Melterskelter Gold Banner Member

    FWIW: I think it should feel a bit oily. I’d just use it and see if it works OK. I would very much doubt that expensive oil would offer any benefit other than slight smoke production differences. I know next time I’ll just buy whatever 2-cycle oil. I also really prefer glycerin over lighter alcohols as it evaporates less.

    Denis
     
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  8. BattyZ

    BattyZ Silver Banner Member

    A few questions after making up 150lbs of kbond. Really like how it molds but mine has absolutely no green strength. Ram a molding box full and will fall out as soon as I lift the box. I let it rest overnight and was better but still falling out.

    I used glycerin (glycerol) as recommended over methanol. Vegetable glycerin off the jungle website.

    Vegetable Glycerin - 250mL (8.45 oz.) - Pure USP Food and Pharmaceutical Grade - Non GMO - Vegan - Sustainable Palm Derived - Humectant, Crafts, DIY, Hypoallergenic Moisturizer, Extracts https://a.co/d/1u7UDqZ

    Mixed in @ 3.2 fl oz per hundred weight. Used the premium smokeless Lucas 2 stroke and bentone from Mach. (Thanks Mach!)

    Concerned that the polar agent is not doing it's job... should I get something different or try adding more? How much is too much or is that not a thing?

    Thanks!

    20230329_205730.jpg
     
  9. Melterskelter

    Melterskelter Gold Banner Member

    What formula did you use. Where did you get your bentone? Somehow your recipe is off.

    Denis
     
  10. BattyZ

    BattyZ Silver Banner Member

    Recipe from the original post of this thread.

    Bentone from user Mach.

    I agree though. I think recipe is off too.

    Might try small batch adding more glycerin and see what I get.
     
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  11. Tops

    Tops Silver Banner Member

    Sounds like a good move. My formula spreadsheet indicates 4oz (by weight by hundredweight pounds). Unless you already corrected for density 1.25 g/cm^3 and are using 3.25 fl oz to get 4oz weight. I love maths when I am not at work ;)

    Edit: see below link to Tom Cobett's latest post or scroll to #56:
    - using only Propylene Carbonate OR Methanol 95%/Water 5% as polar/catalyst (no other alcohols, probable cause of my issues as I used a mixed alcohol)
    - alternates for rejuvenating mixed K-Bond
    - alternate use for glycerin


    https://forums.thehomefoundry.org/i...d-similar-to-petrobond.1759/page-3#post-49971
     
    Last edited: Apr 1, 2023
  12. Tobho Mott

    Tobho Mott Gold Banner Member

    I made a small batch last year using a 2# sample of vg-plus, veg glycerin, synthetic 2 stroke oil, and AFS 130 green diamond sand, following the recipe from earlier in this thread. First test castings turned out ok, but not quite as good as my petrobond, but the sand molded fine. I figured some more time in the muller might improve it. After running what I had used back through the muller and storing it all in a bucket for a month or so, I noticed it felt like it had really dried up and didn't seem very sticky anymore at all. So you're not the only one having some issues with your K-bond, BattyZ. Some of you may remember that when I got all my petrobond, it had sat untouched in its original bags for 2 decades and needed only to be fluffed back up in the muller with no additives to work great. But the K-bond left to sit just felt like almost dry sand

    I was going to wait to post about my K-bond problems until I'd had a chance to at least try mulling and using it again to see if that helps, but I've been putting that on hold and just using my petrobond ever since. Getting back to that is gonna have to wait til later this spring I think, but it's on my to-do list. Meanwhile, I'll be following along to see how you fix yours. Good luck! I have been thinking maybe I made a mistake weighing out the glycerin. Also am thinking about going back to the 30W non detergent oil and/or alcohol for future batches.

    PS. Is anyone else having trouble accessing Ray B.'s website? I just went to double check his copy of the recipe but the link I have seems to be broken. :(

    https://www.foundry.ray-vin.com/k-bond/k-bond.htm

    Jeff
     
  13. Melterskelter

    Melterskelter Gold Banner Member

    The formula I posted works. I think trying a couple small batches to sort it out is a great idea. Any polar agent should work with the main difference in one vs another being evaporation rate. Needing to replenish the polar agent is expected. I added some back every time I mulled. A little goes a long way, though. I’m sure you are frustrated. Keep on pitchin.

    Denis
     
  14. Smoking Shoe

    Smoking Shoe Silver

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  15. Tops

    Tops Silver Banner Member

    Sponsored by Ray-Vin.Com...
    Ingredents:
    100 lbs. sand - 100 mesh or finer - US Silica F110
    6 lbs. Organo-bentone - Bentone 34 or VG-69
    3 lbs. Polybutane (2 US Quarts) Indopol L-100 BP Petroleum or Chevron OLOA
    0.2 lbs. (3.2oz or 91grams) Isopropyl alcohol - any pharmacy
    - or -
    0.2 lbs. (3.2oz or 91grams) Methanol (dry gas) - Auto Parts Store
    - or -
    0.2 lbs. (3.2oz or 91grams) Propylene Carbonate - Lab-Pro, Inc.

    So the Ray-Vin recipe (via Denis post #1) is slightly less Bentone and polar agent 6 and .2 parts per 100 versus the Cobett recipe (via Rocco post #16) at 6-7 and .25 parts per 100.
     
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  16. Tom Cobett

    Tom Cobett Silver

    Glycerin is not a very polar compound. I recommended that it be used instead of smokeless 2-stroke oil as the liquid part of the K-BOND binder system. That way, you get absolutely no smoke after pouring. It should NOT be used as the Polar Additive.

    Here are a few important tips.

    1. Use a fine sand. Typically, we use 110 to 130 Grain Fineness Number. (GFN) It can be silica sand or something man-made like Green Diamond.
    2. Use an Organo Bentone. DO NOT USE BENTONITE! Bentonite will not swell in the presence of anything except water. However, it you treat the Bentonite with Polyethylene Glycol Mono Oleate 400 molecular weight (PEGMO 400) you can make it swell in the presence of oils. You would need to add 50% PEGMO 400 by weight of the Bentonite. PEGMO 400 is a common surfactant used in industrial coatings. OK. Forget I told you this. It is just WAY easier to buy a good quality Organo Bentone.
    3. Originally, we used INDOPOL Amorphous Polybutene as the liquid part of K-BOND. It was clear that this would be difficult to buy in small quantities. That's why we recommended that you use a smokeless (synthetic) 2-stroke oil. The main ingredient in these smokeless oils is Amorphous Polybutene! Any regular motor will work BUT will smoke like a burning television. Use only smokeless oils, OR, you can actually use GLYCERIN (Glycerol) as the liquid portion of the mix.
    4. You need a polar compound to cause the full gelling of the bentone. Absolutely the best choice is Propylene Carbonate. It has a high boiling point and will not evaporate on its own. The second-best polar compound is a mixture of Methanol and 5% water. DO NOT USE ANY OTHER ALCOHOL. Isopropyl or denatured Ethanol will not work very well. The third-best choice for a polar additive is just plain old WATER.
    If your K-BOND seems to lack green strength, you need to add a small addition of the Polar Compound. Water works really well (in small amounts) but it will generally evaporate overnight unless you keep the K-BOND in a plastic bag or a bucket with a tight- fitting lid.
    5. If you just want to buy a 50 lb. bucket of prepared K-BOND Sand, you can purchase it from the student chapter of the American Foundry Society at Kent State University in Ohio. Contact professor Trent True if you want a price. ttrue@kent.edu
    6. If all else fails, you can always reach me at tcobett@tcobettandassociates.com OR call me at (260) 341-2258.
     
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  17. Melterskelter

    Melterskelter Gold Banner Member

    Tom, Well, I guess I am/was confused. Here is a portion of a letter you wrote to me on 6/15/21

    “You can add glycerol to any Petrobond or K-Bond that seems lifeless. It
    should rejuvenate the sand because it allows the oil to swell the clay
    platelets more effectively. ANY POLAR ADDITIVE WILL DO THIS. Glycerol,
    Ethanol, Methanol, Acetone, even water will work. Glycerol has the highest
    boiling point of all of these. It does not have to be replenished that
    often. It has the side benefit of giving very good lubricity to the sand. It
    is totally non-toxic and non-dermatitic.”

    Perhaps a primary distinction between adding for rejuvenation vs primary use as a polar agent is needed here and I must have missed that based on the above note from you. I apologize to anyone I unwittingly mislead. It has been a couple years, but as I recall I did mix up batches of K-bond using glycerol as the only polar agent and I used it for a series of pours making aluminum parts and was happy with it. I have some ingredients still. When I return to the foundry next week from sunny Arizona, I’ll try it just to see what happens.

    I am so glad you have returned to the forum after an, in my opinion, too long an absence.

    Denis
     
  18. BattyZ

    BattyZ Silver Banner Member

    Sounds like I had a bad case of the cantreads...at least I have a smoking gun for issues. Well a lot less smokey gun since I used lucas smokeless in my k bond!

    Thanks for the information. It just sounds like YEARS of trying wrapped up very nicely.

    Might have to give the student chapter a ring. Perfect premixed sand might be my ticket as the current casts are for-profit ones.

    Thanks for chiming in!
     
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  19. BattyZ

    BattyZ Silver Banner Member

    A gallon of glycerin and 16 oz of propylene carbonate are on their way. Going to make a new batch as well as try to add some actual polar additive to the already-made sand.

    Also reached out to the student chapter of AFS about premade.
     
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  20. Melterskelter

    Melterskelter Gold Banner Member

    Where did you get your propylene carbonate? The reason I ask is that I bought some from Clay Planet a month or so ago. But they told me they were going to stop carrying it. (They did say they would be able to special order it in the future.). If there is another source it would be good to know as they are the only US retailer of propylene carbonate I have been able to locate.

    Denis
     

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