Hi. Just getting back into Lost Wax Casting with a Kerr spin casting centrifuge after a 20-some-odd year hiatus. I bought a used Kerr centrifuge in good shape and bolted it to my work table inside an old washtub with the sides heightened courtesy of a ring of thin plate metal. It’s high enough that a blowout should be caught by the inner walls now, but here’s the rub: when I test-spinned the centrifuge the table does an initial wobble from the sudden spin. Q: WILL THAT WOBBLE AFFECT THE CASTING IN ANY WAY? Or should I worry? I can fix the wobble somewhat but I don’t think I can completely put a stop to it. Thanks in advance for any helpful advice.
Can you bolt it down?
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Trying to get the wobble down to a minimum will increase the efficiency of your centrifuge and your castings. Less wobble equals more focused force pushing the molten metal into your flask. Also, wobbling will lead to more wear on the internal parts of your machine, which leads to premature repairs.
I was going to write everything that you need to do, but I found this great PDF that Rio Grande put out how to set up and use a centrifugal casting machine. The one thing that I would add is when I set up my machine I bolted it to a very sturdy table, but my set up worked much better when I bolted the table to the wall as well.
In addition to bolting everything securely, pay particular attention to balancing the arm before every casting. That’s a very important thing to do that often gets skipped.
You’re going to love getting back into casting after a long break. Have fun!!
Jeff
Gluing a bubble level to the arm close to the shaft can help to minimize or eliminate balance issues.
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No, I can’t bolt it to the floor. It’s set up in a big farm shed with a dirt floor. Best I can do is level the floor and table as best i can. I’d have to move a LOT of farm equipment and old machinery to get the table over to the wall to bolt it in place there. Ugh.
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Wow. That PDF is terrific. THANK YOU for the input! Now I just have to figure out the securing process… And yes, I’m having fun getting back into this. Right now I’m having to pay someone else to do all the actual casting, so it’s time to do it myself.
Nice! Thanks for that. I’ve got a couple of those lying around the place.
Got another question for you. The Kerr machine I picked up is a smaller one, designed for dental use. I’m wondering if I can get a replacement for the elbow/cradle portion of the arm that’s a little longer so I can get a bigger flask in there? I see that it can be removed, but looking for a replacement on the InterWebTubes gets to be a ridiculous rabbit hole of web pages that have nothing to do with this. I did find a Kerr service site with lots of model and part numbers but no way of ordering specific items.
Replacing the arm is a good question for a company that sells Kerr centrifugal casters. The issue as far as I know is that the length of the arm and the power of the internal spring are coordinated together. A larger arm which also uses larger flasks, requires a more powerful spring.
I recently reached out to my main contact at Rio Grande for another Orchid member. He said that Rio Grande has a live chat function that is monitored closely. You could post that question to Rio’s chat function. Or call them and ask to speak to a technical support person.
My instinct is that whatever casting arm that you have is what you have to live with for that particular casting machine, but that’s gut instinct and could be incorrect.
Jeff
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The wobble will take energy away from that needed to inject melted metal into the mold. Add as much mass to the table as you can to make it harder for the table to wobble and lower it as much as you can to reduce the movement. Maybe cut off the legs and attach the table to a pile of cement blocks. Just my $.02. Good luck…Rob
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How about a couple buckets filled with concrete that are attached to the table? Maybe something like that could be fashioned to create a mass that is offsets the wobble.
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Hi,
i was also thinking about cement…but more along the lines of pouring a little slab…would that “self-level”…?…could level the wood frame for it…would that work?
then bolt the table down onto the slab…?
julie
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Another thing that I forgot to mention is that if the arm is wobbling, it’s possible for the flask to either fly out completely or move so the flask metal entrance hole is misaligned with the crucible exit hole making metal fly all over the place.
That can also happen if the cradle holding the flask isn’t the right size for the flask.
For safety with a wobbly machine, I’ll often wire the flask into the arm before winding it up. (The machine can break your arm or wrist if it goes off with your arm in there! Wire the flask onto the cradle before you wind it up!) It takes practice to wire the flask onto the cradle quickly without burning yourself. I usually have everything ready to go, with the wire precut and my pliers & gloves there where I need them before I take the flask out of the kiln.
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Thank you again. I’ll go talk to Rio Grande, see if there’s a work-around. As it is, the only flask I can get in there is the small 2.5 inch flask, and I’d like to get at least a 3 inch. I’ve got a couple of larger jewelry pieces that won’t fit in that tiny thing.
I googled what I think is your casting machine. A Kerr 2.5" flask dental casting machine. Here’s two thoughts.
If you’re only trying to add 1/2 inch bigger flask, you could alter this arm with a bit of steel, an angle grinder, hack saw and an arc welder. It doesn’t look that complicated for someone who knows how to weld. I could be wrong, but I’m pretty sure that a slightly bigger flask isn’t going to throw off your ability to balance the arm. Again, this is just a guess!
Yesterday, I also googled a replacement arm for this casting machine and I found some bigger arms that I think will fit it. Unfortunately, today I can’t find them. (I’m on another computer this morning). But I think you can buy a bigger arm to fit your casting machine. Rio Grande or similar can answer that question. The negative to that scenario is they were all expensive. $350ish.
Remember that if you change anything, you’ll have to check that everything still fits.
In answer to your first question about securing the table. Here’s an old Orchid thread asking the same question.
Keep us posted!
Jeff