3D printable Visco fuse machine

[oldmanbeefjerky]

Hi,

 

 

I finally moved into state of australia in which i can freely buy potassium nitrate, aluminium powder, and all those other goodies without juping through too many hoops or high courier costs, though im not particularly interested in pyrotechnics as much any more, mainly since my main passions were blowing stuff up, or creating explosions otherwise, and while that was fun, certain things were beyond my reach, such as making crackers with safe compositions like BP or flash powder.

 

Anyway, recently i bought a 3D printer, a reprap prusa mendel, and you wouldnt beleive what hapenned. The months prior that i had everything planned out, all the cool things i would do with the printer, i either forgot or lost interest in those designs, or they are impractical, and now, after ive bought the printer i dont really have that great a use for it, that is to say, im stumped for ideas, or at least i was.

 

One of the reasons i gave up on trying to make shells, rockets and all those nice artistic things is because A i couldnt make shells, B, i didnt have black powder for lift charges and C, i couldnt make fuses and in australia you cant get fuses anywhere so you have to make your own.

 

Now, since i have a 3D printer, and the patients and materials for A and B, all thats left is C, i dont plan on printing fuses, what i want to do, is 3D print a relatively small visco fuse machine!

 

3D printers have a mayjor limitation in that you cant print extremely big things with them, also, plastic costs allot.

 

What im looking for, is a very minimalistic design for a small, but functional visco fuse machine, im not after cad files to directl print, but rather sketches, or ideas anyone might have, as to how to make a fuse machine that is very minimalstic.

I dont want to print the entire thing out of plastic for one thing, ide like to use metal rods, or wood for structuring, and print pretty much everything else.

 

In the end, since it will never be possible to sell visco fuse, i want to be able to produce and sell relatively cheap visco fuse machines and freely provide the designs for anyone to print their own.

 

For refference, this is the fuse machine im thinking of minimalizing, http://tutorialtub.com/userimgs/small_1316.jpg that simple design.

I want to reduce its width and height as much as possible, so can anyone help me out on this? Im just after ideas on how it can be made smaller, and more minimalistic, so it would actually be plausible to make using a 3d printer.

 

Any ideas please share, thanks.

[mike_au]

As you say, 3d printers tend to be better suited to small parts, and due to cost and speed (or lack there of) I would suggest only printing the bits that can't be made easily.

 

I believe the centre pieces on the two rotating trays have groves cut into them for the threads, those might be reasonable candidates. The trays themselves should probably sit on some sort of bearings, you could make up some flange mounts for some cheap ebay bearings. You could probably improve the gearing somewhat, perhaps making it adjust the speed of the take up spool as it runs. And maybe the take up spool itself, if you don't have access to a wood lathe. The rest really looks like it would be easier to make from metal or wood.

[NightHawkInLight]

The problem with making a visco machine smaller is that you'll run out of room for big spools of string. You don't want to have to rethread 20 spools every few minutes. Unless you can come up with a design that allows the spools to be mounted outside the machine itself you'll have that problem.

[Oinikis]

that's darn cool. my current method of making visco type fuses is cheap and does not require anything more than BP and household stuff, but bending your back for an hour for like 5 meters of fuse is not that fun at all. i think better idea would be making plans, templates, and various stuff so for making the parts you wouldn't need having 3D printer. also size is not an issue anymore. personally, i think 3D printers are in too early stage of evolution to do something usefull. but with better technology, one day we could 3D print big stuff with microscopical accuracy and even print out jet planes and stuff (well, laser cutting is some sort of 3D printing, so technicaly jet planes are 3D printed). but for now i think old fashioned methods are the best. for now. Edited May 21, 2013 by Oinikis

[Mumbles]

Probably the hardest part of a visco machine is getting the correct rotations for the draw speed and getting everything to work together. If you can figure out the correct dimensions of the gears/pullies, that would probably be the most useful. Other that those parts, a visco machine is essentially just two disks with pegs for string, a hopper containing BP, and a collection spool.

[oldmanbeefjerky]

i have a clever idea in mind to make the disks significantly smaller, allowing many more spools and allowing the disks to be closer together. I think though i might first need to try building one myself, then work on minimizing it.

Having a working one before my eyes might prove much more useful than a theoretical mental image. |

 

Question though, if i ramp up the rpm could i make it work only 4 spools?

[mike_au]

I've never actually built one, but my gut says 4 threads isn't going to cut it. I don't think RPM is as important as RPI (or RPcm since you are in the civilised world ) You would need to increase the number of turns of thread per length of fuse as you do that it becomes easier for the threads to unravel, I think its likely to just untwist and the powder will fall out.

 

I think the best approach is to forget about making it significantly smaller, make it normal sized, print the difficult bits and chop the big bits out of wood.

[Mumbles]

I agree with Mike on this one. Until you've actually built a functional, well tuned visco machine, don't worry about trying to improve it. Chances are you'll just mess it up worse.

[oldmanbeefjerky]

well looks like ive got some designing to do, one other thing i was wondering, the two rotating discs, they should spin at the same speed right?

[FlaMtnBkr]

I would think both tables should spin at the same speed assuming the same amount of thread spools.

 

The machine looks fairly simple and the hardest part will be getting the speeds right for everything. But some tweaking should be fairly easy and once set should work well. I have wanted to build one for a couple years but haven't gotten around to it.

 

One thing is to have a tracer thread that is pulled through the powder to help pull the powder into the threads. The tracer thread should not rotate with everything else so it scrapes the edge of the outlet and also pulls powder down. A device that taps the powder container could also help. I've also read that granulated powder works better than mill dust. Obviously it needs to be very fine granulation like 40 or 60 mesh and what is bigger or smaller can be reprocessed. Fine powder seems to be 'sticky' and wants to clump in the container. Also, other powder besides BP can be used to make flying fish fuse.

 

If you get things like RPM figured out and don't mind sharing let us know.

[NightHawkInLight]

The lower wheel should spin slightly faster because the threads will be spun around a larger diameter core, as it will have the first twist of string inside of it. It should also spin in the opposite direction so that the strings cross over each other rather than running parallel which would make for very weak fuse that would be lucky to even hold itself together.

 

Edit: You could possibly get around making one wheel spin faster than the other by increasing or decreasing the number of strings.

Edited May 28, 2013 by NightHawkInLight

[RobertoDuran121]

3D printng that does not sound like a good idea mostly because parts are rather large and most printers small and the 'Ink' is expensive.

[bugmenot]

3D printng that does not sound like a good idea mostly because parts are rather large and most printers small and the 'Ink' is expensive.

 

The ABS plastic is rather cheap, and one might be able to print smaller parts and assemble it into a full machine. I've seen quite a lot of people doing this.

[mikeee]

You will also want to get samples of the thread you intend to use for the fuse.

Depending on the diameter of the fuse you want to make will determine how many threads you will need to weave.

A change in the size of the thread will impact the size of the fuse and your powder feed nozzle.

[Simoski]

Ok I've just ordered a 3D printer. Max size of any component is 30cm X 30cm X 40cm. So I guess the technology has improved a bit in 4 years. Anyhow I am going to model all the components in the next few weeks and begin printing them when it arrives in 10-15 working days.

I will keep you updated with pictures/schematics etc.

What speed do you think the top spindle disk should spin at? How many rpm?

[OldMarine]

Search for Twignberry's posts on this. He posted quite a few details on his setup.

[Arthur]

The 3D printer would lend itself to making pulleys of assorted sizes so that you could have a stock of suitable pulleys/speeds for every rotating part.

 

There are numerous youtube vids of how to make visco there are some on pyrosamm's channel of real Chinese visco machines doing real production of visco -simple and very functional. www.youtube.com/watch?v=BX5zRH8z8Hc&t=407s

 

The big issue will be getting the right thread easily, and enough of it to make the process worthwhile. Cotton, PolyCotton mix and polyester threads do apparently sit differently when used.

 

Getting the lacquer right is also important. Too much and it is the primary speed determinant, too little and the thread isn't water resistant.

[Simoski]

Thanks Oldmarine, Arthur.

 

I've read part of Twignberry's posts... And think that the multiple stepper motors are overkill, surely with the right gearing we can run the entire system off a single motor ( perhaps with a PWM speed control circuit ) or even better a hand crank?

 

what do you guys think?

[Arthur]

One vid from China shows a slow driveshaft coming through a wall to drive a machine through belts(and twisted belts for reverse) and pulleys. Really functional and really cheap. Do NOT over engineer the project it just costs more!

[MrB]

I've read part of Twignberry's posts... And think that the multiple stepper motors are overkill, surely with the right gearing we can run the entire system off a single motor ( perhaps with a PWM speed control circuit ) or even better a hand crank?

 

I think hand-crank isn't really a great idea. A single stepper motor, and some stupid controller that pretty much just sets the speed it turn at, should get you very reliable rpm's where a PWM speed controller might give you variations, and you ideally want it as stable as possible.

[Arthur]

Likely a 40w shaded pole AC motor would give enough speed and power to make fuse at a sensible rate.

https://uk.rs-online.com/web/p/ac-motors/8776247/

https://uk.rs-online.com/web/p/ac-geared-motors/2483659/

https://uk.rs-online.com/web/p/ac-geared-motors/2483665/

 

or similar in your country.

[MrB]

Oh, it's probably plenty fast, and powerful. The issue i'm seeing is RPM stability. If it hunts, be it due to hysteresis (? is that the word i'm looking for? The minute band between "not fast enough, and to fast, in the speed controller.) or variations in the powerfeed doesn't really matter, to get consistent burn, you need consistent feed speeds. Since a small machine like this doesn't have the inertia och a large commercial machine, it becomes a lot more sensitive to these variations. When the rotating assembly weighs a couple of 100 grams at most, and it's feed from a 240v 50Hz nominal, it's going to react fast to small variations in the outlet, while a rotating assembly of possibly 20 kilo, plus 10-15 bobbins of string makes for a lot of inertia, keeping it quite stable in speed.

It might very slowly become a little more sensitive to variations over time as the string runs lower, if they replace all the bobbins at the time commercially, but i don't know if that is done.

The more stable the RPM, the more reliable, and more importantly, consistent burn.

[Arthur]

The "single motor many belts" method means that any speed variation affects all parts of the system equally. Another good reason for using one motor to do everything, and making select pulleys by CNC to get the speeds needed

[Simoski]

Ok

Simpler is better!

A single motor it is then. I have a 12v 8amp DC motor which will work nicely.

 

Any ideas as to how fast the two bobbin trays rotate?

0.5hz 1hz 2hz?

[Arthur]

It's not how fast they rotate but the ratio of the distance pulled by the wind up mechanism to the amount of thread cover per turn. You probably don't need to exceed a foot per minute (300mm) but the chord produced needs over 80% coverage from each set of bobbins before the lacquer is applied. So the thickness of the thread comes into the calculation too. Also you are going to use about five times the product length of thread from each bobbin so 100m of fuse could use 500m of thread from each bobbin (of say 20 bobbins. Get plenty of big bobbins of thread and get them at a good price.