Ceramic shell / Lost wax slurry mixer machine?

Discussion in 'Foundry tools and flasks' started by Zapins, Jan 11, 2019.

  1. Zapins

    Zapins Silver

    After fighting my new larger batch of 10 gallons of slurry to resuspend it every few hours for each coat I have started to think about making a slurry mixer, just for when I am home and actively coating shells. Long term I don't mind the slurry sedimenting out for a few months when I'm not using it but it is a pain to resuspend it and waste 30-50 mins mixing it twice a day every day for a week. Not so much of an issue when you are messing around with 1-3 gallons, but 10+ gals is a bit unpleasant.

    I haven't seen too many designs for slurry mixers on the google. It seems most of them have a motor suspended over the mix and either have a gear reducer down into the slurry or a pulley system for torque. The part I'm wondering about is the propeller in the slurry itself. I didn't see a lot of examples, but outbackfoundries had a simple prop on the end of his shaft. It was pretty small. But that makes me wonder if it can adequately keep all the particles suspended if a relatively small area is being churned by the prop? I would have imagined something more like a bar going across the entire floor would work better or be necessary to do the job? Any ideas? Has anyone looked into this before and figured out what the prop/stirring part needs to look like?
  2. DavidF

    DavidF Administrator Staff Member Banner Member

    The commercial ones I've seen rotate the drum itself and there is a fixed bar that goes into the drum for the mixer. What's on the fixed bar?? No idea..
  3. Petee716

    Petee716 Silver Banner Member

    Attached Files:

  4. Melterskelter

    Melterskelter Silver Banner Member

    The video o the page linked by Petee is interesting. I was surprised to see that they drove the mixers at a constantly varying speed referred to in their blurb as "Sinus Speed" which I take to mean the RPMs graphed out is a sine wave.

    My mind goes to a fixed, shortened to 1/2 height 30 gallon barrel, a trailer wheel bearing (like I used in my muller) to suspend the paddles/rotor and a large sprocket running driven by a cogged rubber belt (impervious to grit) and a used 1/2 HP gear reduction motor. Sounds like a fun and worthy project. the way you have your MIG welding humming now, you will be done in no time. Nice that the paddles do not have to actually be so close fitting as to actually scrape the sides.

  5. Jason

    Jason Silver Banner Member

    I seem to remember Barry just using a 1/2" drill with a long paddle. Don't over complicate this one zap. There is a reason we use this premixed slurry and left the old school mixing in the dust.
  6. FishbonzWV

    FishbonzWV Copper Banner Member

    Make life easy, get a 12v trolling motor and stick it in the drum.
    Adjustable depth setting, variable speed control, point in any direction to get proper mixing.
    Craigs List, Ebay, want ads for used ones.
    Jason likes this.
  7. Zapins

    Zapins Silver

    I stumbled upon Daniel Rotblatt on alloyavenue's old thread and found that he had made a slurry mixer. I have copied his website's post and linked to his site. This looks like a promising method to mix smaller amounts of slurry than building a whole huge system to rotate the drum. I might give this a try in the future.

    http://rotblattsculpture.com/Foundry Pages/slurrymixer.html

    A slurry mixer is used in the ceramic shell process to prevent the slurry from settling and hardening. Industrial mixers have a tank that contains 30 to 50 gallons of slurry and cost several thousand dollars. On a busy month I might cast a couple of sculptures - hardly enough to justify the upkeep of an industrial unit. I did use the Shellspen system, and found it to work quite well, but the lifespan of shellspen once it is mixed is only about two months. After this time the slurry starts to settle and neeeds to be mixed before each dip. I decided to build a small slurry mixer for 5 gallon batches.

    I was able to get a 1/20 hp, 300 rpm inline gear motor and a timer online from Surplus Center. A motor shaft arbor allowed me to mount a chuck onto the motor. I made a propeller from some 16 guage stainless sheet and welded it to a 1/2" stainless steel shaft. The rest of the assembly is welded from angle iron. The tank in just a 5 gallon homer bucket. The white one you see in the pictures is just screwed to the base to hold a second bucket with the slurry which is placed into it. The whole mixer cost me under $75.

    Update: The mixer worked fine for about a year, but then the timer broke. One of the nylon teeth inside broke off and I went and purchased a good electronic timer from Grainger (a Paragon EJW percentage timer, Grainger #6XZ66, about $110). More then doubled the cost of the mixer, but I was tired of coming in and finding the slurry settled and hard. Then the little motor I got stripped a gear, so for another $75 I got a nice 250 rpm, 1/10 hp Bodine motor on ebay (new about $300) - worth it just because it's sooooo quiet! Much beefier, metal gears, etc. As of this writting, there are some still available by the seller. I also purchased a small 4" cast aluminum propeller from McMaster Carr - #3502K122 - for $15. It was too small so I enlarged the propeller with wax sheet and sand-cast a larger one-maybe 7" diameter. It works great. The first one I did was bronze (it's what I was casting that day), and seemed to create an electrolytic reaction with the steel setscrews. Got huge domes of rust/silica over the screws and the bronze started to disappear - the crystal structure of the blades really shows! I've just cast an aluminum one and replaced the setscrews with stainless ones. We'll see how that works. I also plan to make a fiberglass slurry tub that is more conical in shape. It's a pain dipping larger work in a 5 gal homer pail! The upshot: I've now spent around $275 on the mixer, not to mention a bit of work. Worth it? To me, yes...but i love making tools! Besides, as I said above, there is nothing on the market this size.

    Here is a picture of the mixer. The assembly with the timer, motor, and switches can be slid up and down by loosening the two handles on the left. The white bucket is screwed onto the wood base. A second bucket, with the slurry in it, fits inside the white bucket. The lid has a hole cut in it for the shaft with two flaps made from duct tape to help keep the moisture in.[​IMG] [​IMG] [​IMG]
    This is a detail of the motor/timer assembly. You can see the motor shaft arbor and chuck attached to the motor.
    A detail of the motor/timer assembly from the other side. The motor is attached to a plate that is hinged so the angle of the shaft can be changed. I did this because I wasn't sure what angle would be best for mixing the slurry.
    This is a view showing the propellor. The two welds on the right side of the prop are for balancing it. You can also see that the white bucket is screwed into the board with a couple of drywall screws and some washers. Another bucket with the sllurry fits into this one and can be removed and stored when not in use. [​IMG]
  8. DavidF

    DavidF Administrator Staff Member Banner Member

    If you do decide to go this route I have a mixing propeller for you but you will need a 3/4 hp motor and some gear reduction to go with it..
  9. Jason

    Jason Silver Banner Member

  10. Joe Avins

    Joe Avins Lead

    That sounds... awkward.
    Now you're just being nasty.

    (OK, I'll slink back into my hole now.)
  11. Jason

    Jason Silver Banner Member

    Joe you have slinked about as low as you can slunk.:p

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