Re: A Very Different Extruder February 16, 2022 08:16PM |
Registered: 3 years ago Posts: 92 |
By inside out, do you mean using an outrunner motor, or something different? I look forward to seeing it. I just finished constructing my outrunner idea that I wrote about several posts back. Check it out! [reprap.org]Quote
MarksAlot
I've been working on a similar idea, kind of inside-out. Just have to machine a few more parts.
Thanks for the heads-up, I hadn't seen that video yet. Brilliantly simple way to measure extrusion force. That integrated nozzle/heatbreak design does look great for eliminating the possibility of leaks between the heatbreak and nozzle, but I think the patent will ensure that regular threaded nozzles remain the standard.Quote
rq3
Thomas Sanladerer of YouTube fame just did a segment on the new E3D hot end, including measurements of just how much force it takes to squeeze molten plastic out of a nozzle. It's not as much as I thought, and the Schnekenstruder has a mechanical advantage of about 21:1.
Re: A Very Different Extruder February 16, 2022 10:51PM |
Registered: 10 years ago Posts: 6 |
Re: A Very Different Extruder February 16, 2022 11:13PM |
Registered: 10 years ago Posts: 6 |
Re: A Very Different Extruder February 17, 2022 11:32AM |
Registered: 4 years ago Posts: 285 |
Quote
dekutree64
By inside out, do you mean using an outrunner motor, or something different? I look forward to seeing it. I just finished constructing my outrunner idea that I wrote about several posts back. Check it out! [reprap.org]Quote
MarksAlot
I've been working on a similar idea, kind of inside-out. Just have to machine a few more parts.
Thanks for the heads-up, I hadn't seen that video yet. Brilliantly simple way to measure extrusion force. That integrated nozzle/heatbreak design does look great for eliminating the possibility of leaks between the heatbreak and nozzle, but I think the patent will ensure that regular threaded nozzles remain the standard.Quote
rq3
Thomas Sanladerer of YouTube fame just did a segment on the new E3D hot end, including measurements of just how much force it takes to squeeze molten plastic out of a nozzle. It's not as much as I thought, and the Schnekenstruder has a mechanical advantage of about 21:1.
What exactly do you mean by 21:1 mechanical advantage? I thought it would be a leadscrew type calculation. In the case of mine with 288 steps per mm, that gives a lead of 400/288 = 1.39mm per revolution, so 1Nm torque should give 2pi/.00139 = 4520N linear force. According to the Sanladerer video it only takes about 1kg to extrude, so that's only 2.2mNm. And the NEMA 11 is rated for 15mNm, so it probably is indeed enough, especially since you don't need microstepping.
Re: A Very Different Extruder February 17, 2022 11:40AM |
Registered: 4 years ago Posts: 285 |
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MarksAlot
How do you go about getting sufficient grip should the filament change diameter?
Re: A Very Different Extruder February 17, 2022 12:21PM |
Registered: 10 years ago Posts: 6 |
Re: A Very Different Extruder February 19, 2022 03:08PM |
Registered: 4 years ago Posts: 285 |
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dekutree64
Ah, I'm glad I didn't bother with magnets yet then. I recommend using coarse thread screws if you're screwing into plastic. Fewer turns to take them in and out, and at least in my experience machine threads in plastic tend to wear out more quickly.
I have unloaded mine once, and with some gentle turning back and forth by hand I was able to get the lumpy end of the filament through the rollers without having to unscrew the mount. Probably would be better to do it while the filament is still warm so it puts less pressure on the rollers, but it will take some experimentation to find the right time window when it's soft but not sticky. Another option would be to retract part way and then reach in with some nippers and cut the filament between the rollers and heatsink. Then purge the remnant through the nozzle when loading the next filament.
My two-post mount is very nice in terms of usability, since it gives such a clear view and finger access. The long screws support the upward pressure from extrusion just fine, but a three-post mount or full cylinder like yours may be better for high lateral acceleration, to better resist whiplash in all directions. You only really need finger access from one side since it's so easy to turn, but loading and unloading is twice as fast when you can use both hands to spin it.
I look forward to the results with your NEMA 11. My guess is that it will be a bit underpowered. The NEMA 14 seems just right, with enough headroom that you can run cool without worrying about missing steps. Though with an aluminum carrier, a heat-tolerant mounting surface, and no bowden adapter epoxied to it like mine, the stepper should be fine running a little hot.
I still want to try the outrunner design I posted before as well, especially now that we know the anti-torque device is unnecessary. But I won't have a place to put the bowden adapter, so I may have to do it on my other printer. The design is a little mechanically iffy since it puts the extrusion force pulling upward on the roller screws, and pulling upward on the rotor so the shaft retainer clip will have to be shimmed just right so there's no wiggle room. But it should be about as lightweight as you can get.
Re: A Very Different Extruder February 19, 2022 06:50PM |
Registered: 3 years ago Posts: 92 |
Oh, so having the filament pass through the inside hole of the bearings? Interesting indeed! It would be nice if you could get bearings without the edges chamfered, so the edge could function as a blade. But in my experience only the 2mm and smaller sizes have a sharp edge on the inner race. I just checked my 4x8x2 and 5x8x2 bearings and both have very slightly rounded edges, which slide smoothly against PLA filament even when tilted to scrape the edge against it. But with 3 of them positioned to intrude into the 1.75mm diameter just a bit so the filament is bent slightly from one bearing to the next, it will probably grip well enough. But variation in filament diameter or changing to stiffer or more flexible filaments may cause trouble.Quote
MarksAlot
I'm looking at something a little closer to a Uhing rolling ring drive,
I've done miniature versions of the Uhing on 1/8" piano wire as a linear actuator. Somewhat more than 20 lbs of thrust.
I'll have to support filament a little better if I can get it to work.
Re: A Very Different Extruder February 21, 2022 02:28PM |
Registered: 4 years ago Posts: 285 |
Quote
MarksAlot
I'm looking at something a little closer to a Uhing rolling ring drive,
I've done miniature versions of the Uhing on 1/8" piano wire as a linear actuator. Somewhat more than 20 lbs of thrust.
I'll have to support filament a little better if I can get it to work.
Re: A Very Different Extruder February 21, 2022 09:02PM |
Registered: 4 years ago Posts: 285 |
Quote
MarksAlot
To me, an ideal extruder would measure both diameter and travel, calculate volume dispensed, and use that to close the servo dispense loop.
Thermwood does similar with their pellet extruders.
They do a pressure condtrol loop with the screw, the melt then flows through a gear pump to meter/measure the flow into the nozzle, and nozzle velocity follows melt volume dispensed.
We could do similar. A strain gage for pressure control, and a filament encoder+diameter gage right at the cold end entrance. I know all have been done seperately, but not sure volume metering+ pressure control+ nozzle velocity following + predictive/adaptive/lookahead has been rolled together outside high end pro-level printers.
Re: A Very Different Extruder April 03, 2022 05:00PM |
Registered: 5 years ago Posts: 44 |
Re: A Very Different Extruder April 04, 2022 09:25AM |
Registered: 4 years ago Posts: 285 |
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oliof
@rq3 would a hollow shaft stepper like the OMC 17HS13-1504H be an option? ID of the shaft is 4mm, I'm thinking of a PTFE tube insert (OD 4mm/ID 2mm) to constrain the filament better ...
Re: A Very Different Extruder April 04, 2022 05:22PM |
Registered: 5 years ago Posts: 44 |
Re: A Very Different Extruder August 22, 2022 10:26PM |
Registered: 6 years ago Posts: 36 |
Re: A Very Different Extruder August 27, 2022 05:34PM |
Registered: 4 years ago Posts: 285 |
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OutcastZeroOne
very cool to see how this design has progressed. Hope to see it continue to compact down, and hopefully not get stolen by anyone. Keep up the great work
Re: A Very Different Extruder August 27, 2022 06:02PM |
Admin Registered: 16 years ago Posts: 13,889 |
Re: A Very Different Extruder August 27, 2022 08:38PM |
Registered: 4 years ago Posts: 285 |
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VDX
... we've made the same here in Germany (or EU) IP-range -- filed a patent and abandoned it shortly after, so no other party can "block" our open-source development with a similar claim
Re: A Very Different Extruder September 27, 2023 06:01AM |
Registered: 7 years ago Posts: 15 |