Do you want an ice ball maker like those sold online, but don't have $800+ to spend? Then make your own!
Don't know what an ice ball maker is, or how it works? Then check out the last page of this Instructable for a video of it in action.
You'll need access to a machine shop, and specifically a CNC machine. TechShop provides all the equipment you need for a monthy fee. I made it at TechShop, and you can too.
Ice ball makers work by melting a large block of ice into the proper shape. It accomplishes this by having two large blocks of aluminum (aluminum has high heat conductivity and capacity), each with a hemisphere carved into a side, slide together to form a single continuous chamber on the inside. What's left is a perfect sphere.
Don't know what an ice ball maker is, or how it works? Then check out the last page of this Instructable for a video of it in action.
You'll need access to a machine shop, and specifically a CNC machine. TechShop provides all the equipment you need for a monthy fee. I made it at TechShop, and you can too.
Ice ball makers work by melting a large block of ice into the proper shape. It accomplishes this by having two large blocks of aluminum (aluminum has high heat conductivity and capacity), each with a hemisphere carved into a side, slide together to form a single continuous chamber on the inside. What's left is a perfect sphere.
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Signing UpStep 1: Materials and Equipment
The basic material is two large blocks of aluminum. You'll need to pick a size based on the size of the ice ball you want.
You'll need blocks that are in total at least 10 times the volume of your sphere. This is so the aluminum properly melts away the rest of the block. My ice ball maker produces 70 mm diameter ice balls, and the aluminum blocks are each 125x125x75 mm. That's a 13-to-1 ratio, and works pretty well.
You'll also need stainless steel rod. These serve as the bottom vertical guide shafts. I used 3/8" SS rod.
Last, you'll need plastic rod of a larger diameter. This piece slides over the stainless steel rod. I used 3/4" teflon rod, but teflon turns out to be hard to machine. I hear that Delrin machines well.
The only extra material is whatever you think will make the final product easy to use. I added rubber feet and a cabinet knob for lifting the top.
For equipment, you'll need a CNC mill and a lathe, and basic tooling. The inner hemispheres will be cut with a ball end mill, and you'll want as large a diameter here as possible. I used a 1" ball end, but smaller diameters will work as well. You'll also need a tap and die set.
You'll need blocks that are in total at least 10 times the volume of your sphere. This is so the aluminum properly melts away the rest of the block. My ice ball maker produces 70 mm diameter ice balls, and the aluminum blocks are each 125x125x75 mm. That's a 13-to-1 ratio, and works pretty well.
You'll also need stainless steel rod. These serve as the bottom vertical guide shafts. I used 3/8" SS rod.
Last, you'll need plastic rod of a larger diameter. This piece slides over the stainless steel rod. I used 3/4" teflon rod, but teflon turns out to be hard to machine. I hear that Delrin machines well.
The only extra material is whatever you think will make the final product easy to use. I added rubber feet and a cabinet knob for lifting the top.
For equipment, you'll need a CNC mill and a lathe, and basic tooling. The inner hemispheres will be cut with a ball end mill, and you'll want as large a diameter here as possible. I used a 1" ball end, but smaller diameters will work as well. You'll also need a tap and die set.
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I do not have access to any machining equipment and even if I did, I am not a machinist...would you consider making one for me? I would of course pay you for the material, machine time and your time.
Thanks again,
Marko in Mass
Question : What size piece of clear ice do you need to use in the unit? Does the size of the clear block of ice matter...assuming it is big enough to fill the sphere...and does the shape of the clear block make any difference.
I found a small mini-version of the on-line model and when I use mine, sometime I get flat spots on the ball...and I think it might be because I am using irregular shapes of clear ice...pieces just broken off a larger pc of clear ice.
Thanks again and great instructional video.
Marko
I would love to make one of these for ice formed whiskey glasses, say four at a time, or perhaps shotglasses in quantity. Shape then freeze until the party. Have to make grips/indents so it doesn't become too slippery.
Perfect for pool parties - and very little to clean up, at least for those of us who drain our glasses.
One thing to watch out for when refreezing--because there is still a film of water on the surface, you will tend to get marks corresponding to the container you put them in. So it looks a bit imperfect, though after 30 seconds in the glass the marks will melt away.
One thing to watch out for when refreezing--because there is still a film of water on the surface, you will tend to get marks corresponding to the container you put them in. So it looks a bit imperfect, though after 30 seconds in the glass the marks will melt away.
Regards
Edmund
Great stuff. You wrote that aluminum has high heat conductivity and capacity. I was considering milling this in Steel. Do you think steel is just wrong for this?
Many thanks.
The other big problem, as you might expect, is corrosion. Even without anodization, aluminum doesn't corrode in any significant way in the presence of water. Steel will of course rust if you have no protection on it.
Steel is also harder to work with, and isn't necessarily cheaper when you take the heat capacity into account.
You could use stainless of course, but that's far more expensive, even harder to machine, and only fixes the corrosion problem.
The only other material that I would really consider is copper, and that would be a situation where cost isn't the dominant factor. It's impossible to beat aluminum in bang-for-the-buck terms.
The short answer is that you need enough thermal mass to melt through all the ice, and 10:1 is about the right amount.
Long answer:
To melt ice, you need to get through what's called the latent heat of fusion. For ice/water, this is 334 joules/gram. The density of ice is 0.917 g/cm^3, so this comes to 306 J/cm^3
This heat comes from the aluminum (in the short term). Aluminum has a heat capacity of 0.9 J/K-g, so at a density of 2.7 g/cm^3 we have 2.43 J/K-cm^3. Room temperature is 25 C, and we can only go down to 0 C before it stops being able to melt ice. Therefore, the aluminum can supply 61 J/cm^3 of heat energy to melt the ice.
306 J/cm^3/61 J/cm^3 is just about a 5:1 ratio. But that's a bare minimum: the ice ball maker works very slowly when it gets close to 0 C, and the ice will start at a temperature <0 C (depending on how cold the freezer is), and there are some extra holes and such that take away some capacity. So in practice we need a little extra leeway, and 10:1 makes for a nice round number.
If I make another I may try out using round stock. It's actually pretty hard to make a perfectly square block, even on a good mill!
Thanks for the support!
I managed to do the first 4 sides without much trouble but the final 2 sides were more difficult. I ended up fiddling around with an L-block (is there some better name for that?) to get a side perpendicular to both axes, but I'm sure there's a better way.
One small problem is that the CNC machine is only available in 4-hour increments. Although with an optimized process I probably could have finished a full block in that time, with me learning as I went it took much longer than that. Given this, and the fact that I needed the blocks to be square in the end anyway, I decided to make that the first step in the process.
If I do it again, I'll probably look into doing the squaring, planing, hemisphere boring, and drilling all in one pass.
A doubt: the holes in the photo of step 5 seems out of phase. It is to say that joining the hemispheres, the holes don't match. Does you changed them?
Although I didn't incorporate the hole drilling into the program, I was able to use the Tormach for both the hole drilling and tapping. I did this separately from the hemisphere cutting, but that is not a big deal--the hemispheres could be a couple thous off and no one would notice. But each pair of holes did need to be the correct distance apart and so I did those in one step.
If I do make another, I'll see if I can incorporate the drilling into the program. I was using peck drilling since the holes were so deep and there was a lot of volume to remove, and it became quite tedious (and error-prone) after a while.
You're right that there isn't a huge amount of Z travel on the Tormach, but it was sufficient for my purposes, even with my 2" height gauge.
Thanks for the advice on the spotting drill. It seems that there is some debate as to whether center drills are appropriate for this application or not, but in any case spotting drills are a good choice here.
I saw the pieces simply rotating around a vertical axis, the holes do not match, but I realized now that as they are perfectly symmetrical, you also have to rotate them horizontally.
http://www.instructables.com/id/How-to-make-crystal-clear-blocks-of-ice/
I've since made a "quad" unit that can freeze 4 blocks at once, each the correct size for use with the ice ball maker.
just wondering cause it has a better heat conductivity than aluminum