jm
having dreams about rocks
Member since October 2015
Posts: 56
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Post by jm on Feb 12, 2024 1:17:43 GMT -5
Very nice!
I've used a 3d printer to make grinding and polishing cups for my sphere machine, but never thought of building the entire sphere machine with it.
Looking forward to see how it works on rocks.
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jm
having dreams about rocks
Member since October 2015
Posts: 56
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Post by jm on Nov 7, 2023 20:16:37 GMT -5
UPDATE: In case anyone is wondering how this machine has held up... This sphere machine is over 4 years old now and has made well over 200 spheres, ranging in size from 1.5" to 5". It's still running strong on (mostly) original equipment. I did replace one of the drills about a year ago, but it wasn't because of a motor issue. The chuck was worn out from when I first got it and the grinding cup kept slipping in it. I tried replacing the chuck but no matter what I tried I couldn't get it off the drill. At that point I decided it was easier to just replace the whole drill with a spare one I had laying around. Other than that, it's been running strong. I may build a new sphere machine at some point to handle bigger spheres, since I think a 6" sphere would be the max this one could handle. These smaller drills just wouldn't have the horsepower to spin grinding cups for anything bigger. That's a project for later, though.
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jm
having dreams about rocks
Member since October 2015
Posts: 56
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Post by jm on Nov 3, 2023 2:06:20 GMT -5
I've been there more than once... the machine is running smooth, the sphere has good random rotation, everything looks good, so I step away for a couple minutes and come back to a sphere that's stuck in one spot with the grinding cups cutting circles into it. That can be very aggravating.
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jm
having dreams about rocks
Member since October 2015
Posts: 56
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Post by jm on Oct 10, 2023 23:41:04 GMT -5
Did you write the program for the cup Yes, I designed the cups myself using Fusion 360. Well, mostly myself. I'm no stranger to computers and CAD design is not unknown to me, but I still had to get my kids to show me how to do a couple of the trickier components:) They've been using Fusion 360 in school and have more hands on experience with it than I do. After that I used Cura to convert the CAD drawing into a format that the 3d printer could use, then printed them out.
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jm
having dreams about rocks
Member since October 2015
Posts: 56
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Post by jm on Oct 6, 2023 1:51:53 GMT -5
FYI when searching aliexpress I was looking for more diamond segments and found more sold per segment and with an option of 200 and 400 grit. I have never made spheres but have been considering options for surfacing large pieces as an excuse to build my own CNC router type design, and wondering if the finer grits would be useful at all. The higher grit segments would probably work ok for finishing larger pieces, but I should warn you that there seems to be a fair amount of size variation in the segments I've bought. They were supposed to be 40x10x7 mm, but the smallest dimension can vary by a mm or more. Depending on which orientation you used them in, though, this might not be an issue at all. Have you considered using diamond polishing pads instead of hard diamond segments for the higher grits? In my experience, the hard segments work great for rough grinding but the polishing pads give a much better finish.
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jm
having dreams about rocks
Member since October 2015
Posts: 56
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Post by jm on Oct 6, 2023 1:40:53 GMT -5
Really cool. What kind of 3D printer do you have? This is something I’ve wanted for years now (a decade maybe?). Have done some sporadic research over the years but never pulled the trigger and then the technology just keeps changing. I'm using an Ender 3 that I picked up a few years ago. At the time it was one of the better printers that you could get for under $300. I haven't kept up on the latest developments, though, so there may be better ones in the same price range now. The Ender 3 works fine for everything I use it for. My kids probably get more use out of it than I do, they print everything from little articulated animals to quad copter parts.
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jm
having dreams about rocks
Member since October 2015
Posts: 56
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Post by jm on Oct 4, 2023 23:19:41 GMT -5
Here's a quick video I made to show how I go from cubes to semi rounded preforms. The cube I'm starting with here is about 3/4" square. It takes about 2 minutes to round it off. It's quite a bit faster when I have both hands free, instead of using one hand to hold the camera. This video made me very anxious. Do you still have all of your fingers? Yup, still have all my fingers, at least most of the important ones Continuous rim diamond blades like that don't cut skin like a toothed blade would. I can literally hold my finger on the edge of the blade when it's running without getting cut. Fingernails, on the other hand, get chewed off extremely quickly by diamond blades. More than once I've sawed a notch in the end of my fingernail (but at least they grow back)
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jm
having dreams about rocks
Member since October 2015
Posts: 56
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Post by jm on Oct 4, 2023 22:18:28 GMT -5
I thought I'd give an update on my 3d printed grinding cups. They've worked so well that I printed out a bunch more, from 120mm down to 30mm. The grinding segments are removable, so I can swap them between different sizes as needed. So far I've had no problems at all with the plastic breaking. I've finished over 90 spheres with these, so I think they're holding up pretty well. I did have a couple of the machine screws pop off the back of the diamond segments, but that's probably due to my poor brazing skills. What kind of filament are you using for those? Are you able to use PLA, or do you need to use something like PETG or ABS for strength? I'm using PLA, using a wall thickness of 0.8mm, top/bottom thickness of 1.0mm, and cubic subdivision infill of 20%. So far it seems to work fine. Even if I made some bigger grinding cups that would be under more strain, I'm thinking that I could just increase the wall thickness and infill % to make them stronger. I'm sure other types of filament would work fine too, I just use PLA because it's cheaper and I have a lot of it.
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jm
having dreams about rocks
Member since October 2015
Posts: 56
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Post by jm on Oct 4, 2023 14:04:06 GMT -5
Just curious, does Strawberry Hill basalt have any distinguishing characteristics that set it apart from regular black or grey basalt? IMG_2637 by mrk525, on Flickr Wow! I like the contrast in that. Does that come from the Strawberry Hill area on the Oregon coast?
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jm
having dreams about rocks
Member since October 2015
Posts: 56
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Post by jm on Oct 4, 2023 2:03:59 GMT -5
I thought I'd give an update on my 3d printed grinding cups. They've worked so well that I printed out a bunch more, from 120mm down to 30mm. The grinding segments are removable, so I can swap them between different sizes as needed. So far I've had no problems at all with the plastic breaking. I've finished over 90 spheres with these, so I think they're holding up pretty well. I did have a couple of the machine screws pop off the back of the diamond segments, but that's probably due to my poor brazing skills.
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jm
having dreams about rocks
Member since October 2015
Posts: 56
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Post by jm on Oct 4, 2023 1:50:20 GMT -5
I have been making preforms lately. ASMOF I have some Strawberry Hill basalt cutting right now that will be a sphere when it grows up. Just curious, does Strawberry Hill basalt have any distinguishing characteristics that set it apart from regular black or grey basalt?
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jm
having dreams about rocks
Member since October 2015
Posts: 56
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Post by jm on Oct 4, 2023 1:46:41 GMT -5
Really like the petrified wood, obsidian, and especially the thundereggs.👍 How small of spheres have you done? Anything along the lines of beads? The smallest spheres I've made on my sphere machine are those thunderegg ones in the pictures above. They're about 1.5 inches across. I made some grinding cups to make even smaller ones, but I haven't actually done that yet. That being said, a while back I build a marble mill and made a bunch of beads. The smallest I made were these quartz ones that are about 0.45 inches across. The mill would probably be able to handle beads from about 1" down to about 1/4". I can't see it working well for anything smaller than that. The thread that shows my marble mill is here.
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jm
having dreams about rocks
Member since October 2015
Posts: 56
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Post by jm on Oct 3, 2023 1:45:41 GMT -5
I finished another batch of spheres last spring and then got busy with summer activities and completely forgot to post any pictures of them. I started off with about 100 preforms, but some of them had problems during grinding so I only ended up with about 90 finished spheres. The pile has been shrinking because I've been giving some away to family, so I thought I better get some pictures on here before even more of them go away. Here's what's left. These are all obsidian from Glass Buttes, OR. Pardon the photography, I didn't realize until after I got them on here that most of my garage (including the fridge) shows up in the reflections on some of them. These are various granites, conglomerations, and some... umm... other rocks, from Montana, Wyoming, Oregon, and Washington. Some petrified wood. The big ones are from Washington, the small one is from Arizona. Here are some agates from Washington, Montana, and Utah. I don't know what these are, but I like them. And last but not least, some Richardson Ranch thundereggs. Hope you enjoy!
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jm
having dreams about rocks
Member since October 2015
Posts: 56
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Post by jm on Jul 17, 2023 14:16:49 GMT -5
For my machine, I vary the rpm depending on the size of the cups I'm using. I run them as fast as I can without throwing slurry outside the catch basin. I use an old oil changing pan for a catch basin and turn up the speed until the drops of slurry are hitting the side of the pan without going over the top. The machine could handle higher rpms, I just don't want to deal with the extra mess.
I have seperate speed controllers on each motor so I can dial the rpm to exactly what I want. My theory is that higher rpm (within reason) will cut down on the grinding/polishing time and allow me to make more spheres.
I've never checked the specific rpm, but for larger cups (in the 4" range) it's probably in the 75-100 rpm range. For smaller cups (1-2") it's probably double or triple that.
I also slow the rpm's down when I'm doing the initial grind on a rough preform to keep it from popping out. I'm still guessing here, but on a rough preform the rpm is probably under 50.
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jm
having dreams about rocks
Member since October 2015
Posts: 56
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Post by jm on Jan 12, 2023 1:18:47 GMT -5
Can you please explain the wiring harness for your machine like which power supply you bought and what the term is for the water drippy thing lol... I'm making one similar and I have 3 cordless drills that I am converting to DC units. Should the drills be the same model? And are you using bungee cords for keeping the drills pushing on the ball? I have more questions but these are top for now 😀 Here's a rough wiring diagram. The power supply I used has 3 separate DC outputs. Each DC output goes into a speed controller, which then goes into the drill. Here's some links to a power supply and speed controller. These aren't the exact ones I used, but they are very similar. Power supply
Speed controller
I don't know what the term for the water drip thing is, other than calling it a water supply. I used the same model for all 3 drills. It's probably not necessary that they be the same, but I went that route so that I could be reasonably sure that they are all turning about the same rpm. I'm using a loop of bungee material to hold all the drills together, but anything stretchy should work. Here's a video of my machine running.
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jm
having dreams about rocks
Member since October 2015
Posts: 56
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Post by jm on Jan 5, 2023 0:01:14 GMT -5
Instead of paint , i use colored magic markers to define the flat spots . they also dry fast . right or wrong they work for me That's a great idea. I'll have to give that a try.
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jm
having dreams about rocks
Member since October 2015
Posts: 56
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Post by jm on Jan 2, 2023 14:05:26 GMT -5
Hey, that is not the way I do it. Nice work. Glad you figured out your process. Sorry, what I meant to say was "This is the way I do it, so therefore it is the "correct" (or " proper") way to do it!"
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jm
having dreams about rocks
Member since October 2015
Posts: 56
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Post by jm on Jan 2, 2023 14:01:14 GMT -5
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jm
having dreams about rocks
Member since October 2015
Posts: 56
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Post by jm on Jan 2, 2023 13:58:19 GMT -5
Way cool! Thanks for sharing the videos. I have not seen anyone coat the rough like that. I was like- where'd THAT rock come from? What, you haven't heard about the vein of bright orange obsidian at Glass Buttes? Normally I don't paint the entire preform like that but it sure makes the grinding process easier to see on video. Usually when the initial grind is about 3/4 done I'll pull the preform out and slap some bright colored paint on the remaining flat spots. That way when I'm doing the last stages of the grind I don't have to keep stopping the machine to check if all the flat spots are gone. I just keep it going until I don't see any more paint spots. I was using spray paint until recently my wife gave me some of her acrylic craft paint to try and now I'm sold on it. The acrylic paint is dry enough to handle in 15 minutes or so and it sticks to the rock really well. That's much better than waiting for hours for spray paint to dry ( although I discovered that any kind of paint dries much faster if you put the rock in a food dehydrator and crank the temperature up to 150 degrees F).
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jm
having dreams about rocks
Member since October 2015
Posts: 56
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Post by jm on Jan 2, 2023 13:42:36 GMT -5
I notice on the first grind video you have a hand on one of the heads periodically, is that to keep the random motion going on the ball, or to ensure it doesn't pop out? Mostly I keep a hand on one of the drills to keep the random motion going by pushing it a bit to one side or the other. There's enough side to side slop in my setup that I can't always count on it having random rotation all by itself, so I need to babysit it. I have a speed controller for each motor and I've found that if I turn the speed way down during the first part of the grind when there's still lots of corners on the preform then I don't have any problems with the preform popping out. Once the corners get knocked down I can start turning the speed up to make the rest of the process faster.
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