Posted 13 February 2018 - 03:37 AM
In any case, I saw you were going for a ball bearing which is nice, but I found a lazy susan bearing to be fine as well. Dirt cheap and easy to install. Did you consider that? Have a look here: https://www.aliexpre...2841516387.html
Posted 13 February 2018 - 08:23 AM
I've been off the forum for a year due to an overseas posting but I'm heading back soon.
I've made countless generations of designs, can't say I've perfected it but I have found a lot of pitfalls.
Judging by your build volume I'm guessing you have a CR-10. You should be able to get muuuuch better than what you are getting, takes a bit of practice to optimise settings but there are guides all over youtube. I would recommend PLA, it is infinitely easier to print and get great results. You should be able to print that 15 groove die flawlessly. Added benefits are higher strength, wear resistance, rigidity and flame resistance, at the cost of a little brittleness. No chemical incompatibilities found for standard comps, just don't get it too hot.
The ball bearing will be fine, deep groove ball bearings are not meant for axial load but if they are small like this case the only issue is a little wiggle. I chose lazy susans because the through bore is bigger (19mm) this allows you to put gears and pulleys below more easily.
Make sure manual wind is on the collector, it is the most likely to bind. If you have the crank on the spools, the pulley might slip on the collector
Die Sizing, angle, ratios thread counts
Pretty sure its hiding in my previous posts, if not, I'll try dig up notes
Would strongly recommend making it removable. Its a PITA threading the die, a lot more so if you cant get fingers/tools in
Make sure you can adjust the width between tracer threads. This will allow you to adjust the flow of powder into the first die. Needs to change as you move between BP and Chlorate based comps.
My Alu extrusion MKI machine, while not a 'capstan' did use a direct drive winch that kept a constant feed rate. The collector spool deliberately was underpowered and stalled to simply take up slack
Posted 14 February 2018 - 03:24 AM
@Sleipner nice idea with the lazy susan thing, if only I'd thought of that earlier.
I'm gonna run with the ball bearings for now..
@Twignberry, thanks mate, I'll definitely be asking you more questions and as for the die/funnel... yes definitely removable
Posted 14 February 2018 - 06:47 PM
I looked up your work on the visco machine, impressive work! Shares a lot of ideas with the design I'm going for. I've opted for i2c controlled steppers to allow for as many moving parts as one could ever want (modular design with as many plates one wants feeding thread, paper etc). Also, with one of those extra steppers I'm working on a controlled powder dispenser mechanism that gives a more deterministic amount of powder.
Posted 15 February 2018 - 08:54 AM
Yeah, sure I will share what I have eventually, not ready for prime time yet though. If you're in a hurry and you need a machine design now, don't wait for me. From looking at Twignberry's design I think it will satisfy most people. My design goals are 1) for me to have fun building the machine , 2) not minimise machine production cost, just reasonable, see point (1), 3) flexible, modular, extendable, hence a build around i2c which comes at a slight cost increase. A build around typical 3D printer components (like twignberry's) is great cost-wise and sufficient in the vast majority of cases, but in my design I forfeit those positives buying me somewhat greater flexibility of having many more actuators that can give me more layers, controlled powder delivery, direct drive pulling the fuse at constant speed, controlled receiver roll etc. I can also hang various sensors off the i2c to measure various things. Did someone say over engineered? oh well, for me building the machine is almost as fun as using it.
Two thread layer visco fuse is the first proof of concept goal maybe with a controlled NC-coating step, but my main goal is various forms of time fuse (three layers of thread with tar (or perhaps beeswax) in the outer two layers, or paper reinforced visco). I'm looking for input on what kind of paper one could put in a middle layer, and where to source strips of that in sufficent lengths( >500m per roll). I'm also looking for good sources of cheap hemp thread (0.5mm and 1mm diameter). The time fuse I've reverse engineered had an inner layer of 10 x 1mm, then two tarred layers of 7 x 0.5mm. Will need a lot of cheap hemp to make any length of time fuse I saw in "The Agora" forum a group buy for hemp, but I understand it was some time ago, and shipping to Oz would kill the good price.
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Posted 20 February 2018 - 11:28 AM
@Sleipner, great! Sharing is caring.
Its sounds well over engineered mate yours will be vastly more configurable than mine. I wish I could help you with ideas for the time fuse but you're ahead of the game on that one.
My goal is to build a cheap, simple machine, where most parts are 3d printed or widely available and the resultant fuse will be waterproof, will not blow out in the wind, have a constant furn rate, look professional and be suitable for sale.
Here my first major component printed... the top spindle base plate
What do you think?
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Posted 20 February 2018 - 01:54 PM
I don't have good access to a workshop where I am at the moment, so by necessity I'll be working mostly with 3d printed and off-the-shelf parts as well. But I am trading some $$$ for configurability as to me that's what makes it fun I added some equations to the gallery and pointed to them in Swimmer's parallel thread that can help with designing speed ratios etc. Will be adding to those in the next coming days as well to make it easier to apply.
Edited by Sleipner, 20 February 2018 - 01:55 PM.
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Posted 20 February 2018 - 07:45 PM
Sleipner, Lloyd recently parted with a Bickford time fuse machine and could probably offer some good tips on materials and processes for that area of adventure.
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Posted 21 February 2018 - 06:02 PM
A member asked me about time fuse production, which I've done "a bit of" (some 20K ft of it for a commercial company).
My fuse machine led two 'tracer' threads of fine cotton thread down through the powder die, in order to ensure that powder was also carried into the die. My die produced (about) a 1/16" inch-diameter core (because that's what the 'spec' was on the fuse), but the core could reasonably be as much as 1/8" in diameter.
Just past the powder die, ten threads of jute twine (single-ply) were wrapped around the powder core. Then, about a foot 'lower' on the machine, eight threads of the same jute were counter-wound (opposite direction) around the first wraps. At that point the 'raw' fuse is stable, but still not 'fixed'..
After the counter-wind, the pre-wrapped *but not-yet 'fixed'* fuse is passed through a set of compaction rollers (at HIGH pressure) to ensure that the fuse is 1) properly compacted, so the powder burns at a regular rate, and 2) so the unbound fuse is of the correct diameter for the 'finishing' operations.
Then the un-bound fuse (now compacted) entered a hot tar bath. While still hot,. a 'stripper die' removed excess tar, then a first 'wind' of finishing material was applied. In my case, it was fabric tape (because I was making a particular, specified, type of fuse). The material could have been paper (like common visco, but was fabric tape, because of the specifications.
Over that was a 'counter-wind' of the same fabric. Again, like visco, it could have been another counter-wind of a few threads to 'lock' the paper wrappings. That was followed by a quick dip in PVA-based adhesive and dye to fix the wraps and color the fuse appropriately for the contract.
It then passed through 48' of heated drying column (in 4 passes) to dry the PVA, and was wound on a take-up spool to be later measured and cut in 'standard' lengths for delivery to the client.
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Posted 21 February 2018 - 06:43 PM
Thanks @ Lloyd I appreciate your effort describing the machine in detail.
About the tar, was that a particular blend you made yourself (to be just the right amount of sticky/flexible), or was it some stock standard type typically used for other purposes?
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