COVID supplies - .stl patterns

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awake

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Some of you live in places where the pandemic has largely been beaten back, so these files may not be of interest to you. Others of us are facing an ongoing challenge, so I am posting these files in case they will be of use.

My wife asked me to work these up to replicate commercial products that she had seen or borrowed. The "hook" is supposed to allow pressing buttons and pulling on door handles. To be honest, I am not sure that I would find these useful, but she and some of her friends have been interested. The version shown in the picture below proved to be a bit too weak - it tended to break when yanking on a car door handle, for example - so I tweaked the design to add strength. I printed the final version of this hook, which I've included .stl file below, in PETG using .2mm layer height, 5 perimeters, 4 layers top and bottom, 25% infill, and it seems to be strong enough for the intended use.

The "strap" is intended to allow a more comfortable and adjustable option for securing the elastic on face masks - rather than hooking the elastic around one's ears, this strap allows hooking the elastic around whichever "T-hook" provides the best fit and comfort. This design needs some flexibility - maybe it would work with PETG (??), but I'd think it might be a bit too stiff for comfort. Instead I designed it to print with flexible filament. The grey one in the picture below was printed using TPU-85, which turned out to be too flexible; the blue ones were printed with TPU-95, which seems to be just right.

Incidentally, I printed these straps on my home-made 3d printer with a Bowden-type extruder. Supposedly you can't print flexible filament using a Bowden-type extruder ... but in fact, you can, if you do the following: 1) use the right temperature (hot enough that minimal pressure is needed to squeeze out the molten filament); 2) increase the force on the extruder follower; 3) print slow - as slow as 15mm/s; and most important of all, set up the extruder such that the filament path is fully enclosed at every possible point, so that there is nowhere for the filament to "squish" out.
 

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goldstar31

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Andy,
Seriously I wonder just how helpful having these interesting gadgets will be.
We- that is us Limey bastards are being told tom regularly and continuously washing our hands with good old soap and water or if this is impossible, to use alcohol gel.

Being a Geordie- that is a Scotsman with his brains kicked in, I take a regular intake of malt whisky- just i case the rest don't work.
Hic!!!!!

Norman
 

SmithDoor

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The Covid-19 is not going away.
Myself I been tested and do not have Covid-19
But I do have one family member that has Covid-19.

Dave
 

ddmckee54

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Awake:

In your 3rd comment about printing flexible filament on a Bowden tube type extruder, what do you mean by "fully enclosed at every possible point"? I've got one Bowden tube type printer, and I don't know of any points on it between the extruder drive gear and the nozzle that aren't fully enclosed. I've never tried printing a flexible filament on it. For the simple reason that like you said, everybody says don't do it because it won't work.

Don
 

goldstar31

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The Covid-19 is not going away.
Myself I been tested and do not have Covid-19
But I do have one family member that has Covid-19.

Dave
dave

I hope that all goes well- for you and your family.


No tests for me! NB I have Chinese and HongKong connections and was really ill at the Chinese New Year.
Take Care


Norman
 

lohring

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My dental office uses similar ear savers as well as Prusa face shields that I printed. I also printed some face masks, but for now we
need to use officially approved (but uncomfortable) N 95 masks. Of course we also requested help from the Emperor. He sent his most trusted general and most faithful troops. May the floss be with you.

Lohring Miller

Star Wars.jpgThe empire strikes back..jpg
 

SmithDoor

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My dental office uses similar ear savers as well as Prusa face shields that I printed. I also printed some face masks, but for now we
need to use officially approved (but uncomfortable) N 95 masks. Of course we also requested help from the Emperor. He sent his most trusted general and most faithful troops. May the floss be with you.

Lohring Miller

View attachment 118066View attachment 118067
I like the storm trooper look.

Dave
 

awake

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Andy,
Seriously I wonder just how helpful having these interesting gadgets will be.
We- that is us Limey bastards are being told tom regularly and continuously washing our hands with good old soap and water or if this is impossible, to use alcohol gel.

Being a Geordie- that is a Scotsman with his brains kicked in, I take a regular intake of malt whisky- just i case the rest don't work.
Hic!!!!!

Norman
Norman, I am doubtful about the value of the "hook," but my wife likes it, so ... :)

On the strap, I do think it will make wearing a mask more secure and comfortable. Masks are required at the university where I teach, so anything that makes that easier will be useful.
 

awake

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Awake:

In your 3rd comment about printing flexible filament on a Bowden tube type extruder, what do you mean by "fully enclosed at every possible point"? I've got one Bowden tube type printer, and I don't know of any points on it between the extruder drive gear and the nozzle that aren't fully enclosed. I've never tried printing a flexible filament on it. For the simple reason that like you said, everybody says don't do it because it won't work.

Don
Hi Don,

Yeah, that was not very clear - I was thinking that when I wrote it! Here are a couple of pictures - not the best, but I hope they will help to explain what I mean.

First, note that I have a short piece of PTFE coming in from the bottom (the intake side) as well as the tube that goes out the top to the hot end:

IMG_8215.JPG

But that is just to allow the important part. Here's the closeup:

IMG_8213.JPG

Notice how the extruder is made with a "cone" at the top and bottom, which in turn supports the PTFE tube coming through right up to the gear and roller. In fact, the tubing has been trimmed so that it is a triangular shape at the bottom, and modified triangular shape at the top, allowing the tube to very nearly touch the gear and roller. I'm not honestly sure how important it is to have the tubing right up there at the bottom (input side), but definitely must be at the top (output side).

Without having the path constrained right up to the gear and roller, it is easy for the flexible filament to "squirt" sideways rather than proceeding up the Bowden tube. And once that begins to happen, it just keeps squirting out of the extruder instead of pushing on through the hot end.

Even with it constrained as shown above, I won't say it is impossible for that to happen - if you tried to print too fast or not sufficiently hot, the back pressure will increase, and the filament is so flexible that it will find a way to squeeze through even a small crack rather than going on up the Bowden tube.

Here are the key parameters that I am using on my machine, which seem to be working well:

* Max printing speed of 15mm/s - supposedly you can go as high as 25 or 30mm/s, but I've had the best results just taking my time.

* 250°C - this is the upper end of the range for the filament I am using, and of course this is a temperature which requires an all-metal hot end.

* No retraction - forgot to say that part before; this does mean there will be a fair bit of "strings" to clean up, but flex filament does not respond well to the rapid movement of retraction and return.

* 70°C heated bed - you might be able to print on a non-heated bed - ? I've not tried, so can't say.

* Blue painter's tape with glue stick - I almost forgot this part, and it is really important ... not to get the filament to stick, but to get it to release. TPU sticks like crazy, so if you don't have something to help it release, it may become a permanent part of your bed plate! Don't just use the tape; the glue is essential for creating a thin "release" layer, and is easy to wash off when the print is removed from the bed. Or at least, that has been my experience ...

* 1.4 Extrusion multiplier - I've read that flex filament requires "over extruding," and that has proved correct in my experience, though of course I'm sure it depends in part on the filament and perhaps also the machine.

* High pressure on the extruder roller - I find that I have to tighten the pressure adjustment considerably to reliably move the flex filament.

* As above, as fully constrained a filament path as possible.

In case it is helpful, I've also attached the .stl files of the extruder shown in the picture. The basic principle is based on the extruder that I started out with, a simple design that was readily available on eBay at the time I built my printer. I did a quick search, and found this "Creality Upgrade," which is somewhat similar: Upgrade Aluminum Extruder Drive Feed Kit For Creality Ender 3D Printer CR-10S US | eBay

I hope it goes without saying, but I have no connection with the product or the seller in the link above - just using it for illustration. One difference between the one I started with and the one above is that the latter has a couple of "bulges" or "humps" a bit akin to the "cones" in my custom design. Maybe this one, or one like it, would work if modified to take the PTFE tubing right up to the gear and roller. The one I started with lacked those "bulges" or "humps" or whatever you want to call them, so when I tried to position the PTFE tubing right up at the gear and roller, it was not supported on the sides, allowing the filament to push it out of position as it squirted out.

I'm afraid this description is not making any sense at all ... don't hesitate to ask questions as needed, and I will try to clarify!
 

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ddmckee54

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My Bowden tube extruder drive is a Chinese clone of the Creality upgrade you listed. I do know that the threads on the fitting that the Bowden tube fits into are TINY, maybe M5 or M6. No way they could be bored to allow a 4mm PTFE tube pass thru them.

My Wanhao D6 clone is a direct drive extruder, that would probably be the best printer to use, IF I ever decide that I want to try printing a flexible filament. Though I don't know if the PTFE liner in the heat break would survive, 250°C is getting awfully close to the melting point of Teflon isn't it?

Don
 

awake

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Ah, now that you say that, I remember that I had the same issue. As best I can remember, that is what first led me to print an extruder - I needed to increase the depth of the "lip" and "lever" to accommodate a 10mm fitting rather than the little M5 or whatever it is. That let me use a fitting that allows the PTFE tubing to continue through the fitting. So I made the first version essentially just like the original, but deeper ... but that's when I realized that the PTFE tubing really needed support up as close to the gear & roller as possible so that it can't wiggle sideways. So I worked on adding in the "cone" to support it as far up as I could get. As best I remember, I printed 4 or 5 versions before I finally tweaked it just right - but it takes very little plastic, so printed quickly. I am pretty sure I printed these out of PETG, but I would think PLA would work as well.

All that said, I would assume a direct-drive would be the better choice - certainly that's what "they" all seem to say. I have thought about working up a direct drive for my printer, just to see, but never have felt enough need to put in the time required to make the change.

However, I agree that I would not want to try printing this hot with a PTFE lined hot end. I don't recall what the upper limit is supposed to be, but I'm 99% sure that 250° is well over the limit. However, an all-metal hot-end is $10 on eBay, if you don't mind an import clone. That's all I've ever used, with good results on every filament I've tried. Well, good results at least as far as the hot end is concerned. I've concluded there is no way to get good results in nylon or POM (Delrin) without an enclosure. Yet another thing I have never gotten around to ...
 

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