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Nice! I’ve seen those hubs during my research, it’s a quite clever solution that allows for adjusting for tolerances. But I agree it would be better to tweak the design to not have that screw in the end grain to allow for a more solid structure.
However, it is not easy to make these with the injection machine, as there are undercuts.
Not sure I see the undercuts? Is it because of the hole in the center of that peg?
Myself, I’m looking at two types of joinery now which I’ve tested on small scale using the lasercutter (one is based on the great work of Robert Clark). Seems to work well but I’m a bit concerned with how tolerances might affect the assembling on a larger scale.
Oh but I’m certainly open to offer help and share my findings if there are questions regarding the mathematics or 3D modeling of it. I’ve read that an issue with diy outdoor geodesic domes is sealing them properly from wind and water.
Buckminster fuller has made some amazing stuff, especially knowing he didn’t have access to computers to do the math and calculations. Pretty insane.
This is super interesting stuff, great work with a lot of potential!
Coincidentally I’m currently researching geodesic structures for a client. The project will probably be made out of cnc-machined plywood but my research might be of help for figuring out the hubs of the structures. Some of those geodesic structures can be made out of just 2 pieces, similar to the system you’ve made.
In that case here’s also the 3D model of the flute after demoulding. Perhaps he can have a look at the shape of the flute as well. I made some adjustments along the way to the diameter and length of the recorder to fit my production process. I think, in comparison to the industry standard, the body should be a tiny bit longer and the diameter a bit bigger.
One improvement I can already suggest for is for the mold of the body part. In the current design the core can still move sideways in one direction, since It’s not constraint. So the mold needs to get something that prevents it from doing this. During the molding I solved it by putting first a clamp there that covers the 3 parts of the mold, to make sure it doesn’t miss align.
Here are the .STEP files of the molds. Let me know if you can open these.
best is to have the original CAD files (Fusion360,Solid Works).
Not sure if that’s the best in this case. I drew it in Rhino, which is a non-history CAD-software unlike Solidworks or Fusion. I find this the easiest/quickest to work in and allows for a more iterative 3D modelling process but it has also its obvious downsides. I’ll try preparing it as a STEP and a STL file, so it can be opened in most CAD software.
Coincidentally I’ve also been playing around with straws recently (not as impressive though): https://youtu.be/L5VtpPch23I
What a coincidence! Yeah what I ended up doing was to just use scissors and cut 4 straws at the same time in smaller pieces for the injection machine. For the manual way I used an old bread-mold and melt the straws in there in the oven to one blob and then used a spatula to scoop the molten plastic into the molds. Then I would put the mold back into oven, to make sure the plastic wasn’t solidifying before I clamp the molds together.
Using just a standard oven is actually a very great and low-tech way to get started with recycling plastic without having to build any machines, I was pleasantly surprised by that.
Any reason you didn’t turn the tapered core on a lathe?
@andyn Good question! Yes, for 2 reasons:
A: I didn’t know we had a chuck for holding square stock for our lathe. Afterwards I found out we do have it.
B: I don’t have the skills to do this manually on the lathe to get the correct angle for tapering. (nor do I know if it is possible on our lathe)
I did end up polishing the cores to make it easier to take out. And with the injection machine this went quite ok but with the manual casting it seemed to stick to the core (even while using different anti-stick liquids). It could be related to the fact that I was cooling the mold down with water when using the injection machine, whereas the manual way I just let it sit and cool down. What do you think?
I think I can share the files. However, I’d like to emphasize that these can greatly be improved for being used in a proper production setup. So I don’t encourage people from blindly spending money or effort on having the molds produced before they realize what they up to. Perhaps it’s more useful if I provide some kind of image on the mold to explain design decisions? What do you think?
We have a 2440×1220 cnc-machine which is mostly being used for milling wood but I’ve been milling aluminium on it with a good finish. The image below has also been machined on the same cnc. The difference here was that I was milling with a ballnose bit and that seems to require some more experimentation for getting a superb finish. I think it has to do with the fact that you are dealing with different speeds depending on which side of the ballnose you are milling when milling a 3D object. The closer you get to the center of the bit, the slower the speed because the diameter decreases.
And some more visuals of the mold design of the recorder.
Since I ran out of time and had to deliver the flute to the fluteplayer/maker I didn’t manage to make proper pictures of the flute fully assembled which is a bit unfortunate. But perhaps I manage to make another one soon when I find the time. In the meantime here is the final video that came out of the project:
After the manual testing I handed over the mold to Martin so he could tweak it and try it out on the injection machine. There were a few challenges which had to be overcome (filling the injection machine with straws/hollow cylinders is cumbersome) but in the end he made it work. What we noticed was that the injection machine tended to blend the colors of the straws more together turning it into a pink-ish color in comparison to the nice colors of original straw with the manual technique. On the other hand, it seemed like the injection machine gave a nicer finish on the inside of the flute and it seemed like it was easier to get the core out. See the attached picture, the one on the left is made using the injection machine. The other two were made using the oven.
For the front part of the flute I had to make a 4-part mold. This was quite a bit of a brainteaser. To make things not more complex I decided to cut the opening which creates the sound afterwards by hand. Then the sound could be tweaked manually and tuned (same reason why I left the holes out of the body part). The same goes for the block that gets inserted into the front piece and guides the airstream in the right direction. That part I just created separately by filling up a tube with molten plastic and then turning it to the correct diameter. I was a bit skeptical as to whether I would manage to make the flute actually make sound but after doing a lot of research I managed to get it too work. The tweaking of the holes and its diameters and the insert I left up to the guy that would be playing the flute, since he’s a flute maker and knew more about that than I do.
However, what did end up working was filling both halves of the molds with molten plastic and then laying the core in between them and sandwiching that together. It’s quite time sensitive since I wanted to keep the core cold to prevent the plastic from sticking to it. But at the same time this makes sure the plastic starts hardening quickly. It was super satisfying to get this piece coming out the way it was intended. And the texture looks just awesome. One tricky thing was to get the core out. Even though it was tapered it required still a bit of fiddling before it would come out. The best way was to actually keep the plastic part in the mold and use the gaps I provided to put a flathead screwdriver in between to pry it open. That was a nice idea I took from @andyn ‘s adjustment to that peg mold.
I got a few mixed results by trying out different techniques: First I wanted to completely fill the two sides of the mold with molten plastic and try to push the core in while the plastic is hot. After 2 attempts with different melting techniques I concluded that this wasn’t going to work. The viscosity of the plastic was just too high and the plastic would harden whenever I tried pushing the core in. I also had the problem that I constantly had to take the mold out of the oven to fill it with more straws since they take so much space for so little material. On the picture below you can see a failed attempt with the mold not completely being filled when I pushed the core in.
Because of the time limit I decided it would be wise to look into 2 ways of producing the flute. One would be the manual approach, as I did with the test-mold I made. And the other would be using the injection machine that @martingautron has been building. So I started working on the mold and doing research on how to produce it. It’s actually quite interesting to learn about how a recorder is made but it also provided some extra challenges in producing it. So I decided to first make the body part. I modeled and produced a 3 part mold and started testing with that in the manual way.
Since there wasn’t much time before the release of the campaign I decided to get a bit more hands-on experience with melting plastic so I first made a quick mold out of aluminium using the cnc and melted some plastic in the oven (it’s an oven for non-food experiments we have at our coworkingspace). I squeezed the mold together manually and this worked way better than I expected it would and that gave me more confidence on the feasibility of this project.
What does the mold look like? What are you trying to make?
I got this spam message.
Also: I tried uploading a picture without a message but get an error saying I need to have a message as well. When I then try to upload the image again and type the message above I get an error saying I’m moving too fast? Let’s see if it works now.
I think it’s an interesting experiment. Sure, a straight beam is more versatile afterwards but for specific purposes, which are bit hard to think of right now because we’re not used to producing things this way, this could be a useful manufacturing technique. It’s a different way of thinking. I believe that instead of adjusting the final product to fit the production technique (in this case straight beams and joining at an angle afterwards) this might open up more possibilities of adjusting your production technique to make the final product.
To get an idea of how much pressing is needed I guess you could design the mold in such a way that it’s visible when the mold is full. Tiny holes in the mold that show the plastic has run through the mold for instance? But I guess then you still need to respond fast. Can you control the speed of the hydraulic press?
Or an adjustable end-switch that moves along with the press so that the hydraulic press turns off when you’ve injected a certain amount of plastic? One could then calculate in advance how much plastic is needed to fill the mold and work form that.
Very interesting! I can imagine this makes it way easier to put a lot of pressure. But I guess this also means you reduce the speed of injection a lot? Would be interesting to have a “normal” injection machine next to your concept and compare the advantages & disadvantages in relation to each other.
I would think this acts more as a combo of an extruder and an injection machine. Good for putting lots of pressure and being able to properly fill up the mold. But less good in terms of production speed. That’s just my theory though.
I don’t have my own machine but work a lot with the cnc-machine (shopbot 122x244cm) in our co-workingspace or machines from clients. I mill mainly wood materials (objects/furniture for interiors which I draw out in CAD) but have been cutting some metals and plastics as well for prototypes. For the toolpath creating I use either a diy gcode generator inside rhino/grasshopper or Fusion for 3D milling. I tend to often stick to single-flute milling bits as they are a good all-round option for lots of materials and there’s enough room for material to be cleared. I don’t use any coolant for cutting metals like aluminium, brass or copper.
This is an interesting topic! At our local self-sustaining makerspace, which is a non-profit organization and has no employees or owners, we work with a do-ocracy: the one who takes initiative decides. https://communitywiki.org/wiki/DoOcracy
You can read more on how the organization works here: https://bitraf.no/wiki/Hvordan_Bitraf_fungerer:en
Not sure if/how that would relate to what you’re trying to set up here but thought it might give some food for thought. It has its advantages as well as disadvantages but I guess every structure has.
Great project! Would it makes sense to have some detachable weights on the wheel of the bike to turn it more into a flywheel when in shredder-mode?
Good stuff! Let me know if I can help out, I got quite a bit of experience with cnc-machines. (that is, using them and designing parts and drawings for them. Not building.)
Based on the results shown above I figured you found out that there’s a lot of inspiration to be gained from the wood-working/furniture making industry regarding this. Search for cnc-produced or lasercut products and you’ll gain more inspiration than you wish for.
That said, I could be interested in buying sheets of recycled plastic if they’d be available, to offer to my clients or to just try and make some products out of them. Preferably solid pieces, not flexible sheets.