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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khara
fully equipped rock polisher
Member since September 2022
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Post by khara on Oct 5, 2023 5:43:40 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.
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Brian
fully equipped rock polisher
Member since July 2020
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Post by Brian on Oct 5, 2023 9:01:09 GMT -5
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. Thanks! I guess there really shouldn’t be too much strain on the cups themselves. Ideally, they should be moving smoothly on the sphere-in-progress. The biggest stress points would be the connections to the grinding elements, but those areas are already reinforced by the design itself. I find it amazing how strong the cubic infill can be.
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Post by Rockoonz on Oct 5, 2023 11:49:51 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.
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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 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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khara
fully equipped rock polisher
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Post by khara on Oct 6, 2023 16:10:21 GMT -5
Thanks for the info jm . It’s a good place to start anyway, with products others have had good luck with. 👍
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Post by Pat on Oct 6, 2023 16:33:53 GMT -5
For someone whose first high tech device was a mechanical pencil, 3D printing is absolute magic!!
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gunsil
spending too much on rocks
Member since January 2023
Posts: 325
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Post by gunsil on Oct 6, 2023 16:40:27 GMT -5
Fantastic engineering!!
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vwfence
has rocks in the head
Member since January 2013
Posts: 557
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Post by vwfence on Oct 8, 2023 22:20:47 GMT -5
Did you write the program for the cup
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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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callmerob
starting to spend too much on rocks
I really like a dirt road
Member since September 2019
Posts: 131
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Post by callmerob on Oct 15, 2023 13:59:34 GMT -5
Thank you for this example of great engineering problem solving. Absolutely great!
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