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Designs that do not fit in other categories. Previously named "New RepStraps and Post Mendel"
1) Resins
* Polyester resins
These are cheap, very commonly available resins. They are, when not mixed with fillers, clear and have the consistency of syrup, the viscosity depending on the Styrene monomer solvent content it has. The resin sold in shops usually comes with a dual component catalyzer, generally Benzoylperoxide or MEKPeroxide. This catalyzer is of no use for our UV-catalyzed mix. The
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spota
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Plastic Extruder Working Group
What do you need for using UV-curing resins?
In this thread I will list a number of materials you will need to make use of UV-curing reins. I have decided to post this information here in the forum for now, as it seems the place where it's guaranteed not to be deleted and I can always link to in the future when asked these questions, as well as being able to receive comments from people engaging
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spota
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Plastic Extruder Working Group
Zach asked me on the builder's blog what the shelf-life of these resins was.
That's quite an important issue as nobody wants resins to harden in your gear overnight or even worse, while you are printing.
I have found out that on my standard, high reactivity resins (composed of high amounts of any of the new catalyzers, between 4-5 weight% of new catalyzers along with 4-5w% Benzophenone (BP) and
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spota
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Polymer Working Group
Maybe I'm funny that way but Walter jon Williams is one of my all time favourites.
"Aristoi" is a great book about self-replicating machines set in space opera setting.
But I'm a complete fan of hard sci-fi, such like Kim Stanley robinsons Red, Green, Blue Mars, and anything of that type
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spota
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General
I made some tests with pressure pots a while ago and I can confirm that the repeatability of these devices is very tricky to achieve.
But if you want to use that simple and cheap device for testing UV-resin extrusion, you can go ahead. The Polyester resin is OK with polyethylene plstic this pump syringe seems to be made of. There are some plastics that do not respond well to PE resins. These are
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spota
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Polymer Working Group
It has more of a honey like viscosity, yes.
Probably acrylic resins could be made less viscous. But those resins remains to be tested yet as I have only tried out Polyester for now.
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spota
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Polymer Working Group
Ah, if you could get me plans for a syringe based RepRap I'd rush in and start buying and building myself one. I am confident enough on the resins I found to start printing some very neat stuff as soon as I have a robot for it. Maybe you could tell me what are the modules I can start with and that will support your newly designed syringe head. I will probably not have finished the building before
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spota
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Polymer Working Group
Well, I know the products needed for visible (blue light) radiation curing and they are all very expesive, sadly.
This application, for now, is out of our reach, unless I manage to get fulltime in a research-lab with all the means necessary to find out some cheap chemical that would do this. This means if I win the lottery or some philanthropist to pay for my bills
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spota
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Polymer Working Group
I think Viktor has answered there quite exhaustively.
I would add that I have no idea what an optical robot with precision mirror parts means as a development challenge, and if it's manageable, what the price tag would be.
I would rather carry an optical fiber with a lens at the end on a cartesian robot arm, which would make things easier to implement.
Also, I wager the UV laser needed for these
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spota
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Polymer Working Group
aka47 Wrote:
-------------------------------------------------------
> Clever stuff
>
> I had originally suggested LED's because I was envisaging a ring of leds around the deposition type nozzel/needle.
> The tool head can then Deposit, Deposit & Cure or Cure only and can be selective about which areas get cured and for how long.
>
> Whilst a syringe is an option, providi
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spota
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Polymer Working Group
Good ideas!
If you don't mind, I will copy this to the other thread about the UV RepRap
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spota
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Polymer Working Group
Ok, Viktor. I'll PM you for your address.
Maybe we can figure out how to get you some samples. Your equipment would be areal boost for the advancement of this device!
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spota
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Polymer Working Group
Hey Viktor.
I read your post and you are right to point out this shrinkage issue.
I have also concerns about the need of drying. This means that the water content of the paste has to be evaporated? Evaporation is quite a difficult technique to master in a even way. You can never be sure the paste dries out evenly on the surfaces and in the interior of volumes. This may cause cracks and objects wi
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spota
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Polymer Working Group
I have lately devised a couple of resins that cure very well with UV light (see builders blog: on Monday, February 11, 2008)
The price of a kg of this resin would be around 10 to 13
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spota
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Polymer Working Group
Actually I'm seriously considering building a cartesian robot right now.
I have almost all I need and the issues that I have to solve now are more of a construction of the robot with efficient UV lamps type.
I will open a thread with my inputs on UV lamps. Maybe there are some ideas out there that will help me out.
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spota
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Polymer Working Group
Yeah, formaldehyde is thought to be nasty...
I would try Acetaldehyde, the next heavier aldehyde:
you can buy it online here
I would expect the latter to be less reactive than Formaldehyde though, so don't guarantee it will work. Does anybody have a cost estimate of this plastic, all reactives included?
It's also a little unclear to me how this stuff would be dispensed. Any thoughts?
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spota
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Polymer Working Group
Continuing tests on the recently discovered photoinitiator mixes:
I made a series of tests I figured to see which of both mixes fares better.
Don't forget, Benzil+Benzophenone is the cheap mix, Isobutybenzoinesther+Benzophenone is the expensive one. The layer thickness is 1mm in every test. No mentionable shrinkage will occur in any test.
Test A) 5 minutes of UVC irradiation, followed by 2 minu
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spota
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Polymer Working Group
Thanks Viktor!
I really think this will open the door for really accurate printing applications.
As a reference, when I speak of UVC, it's 254nm. UVB is 365nm.
maybe I should mail you or post the corresponding spectra of these photoinitiators, so that you see what UV sources would be valid.
A very usefull link on UV leds
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spota
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Polymer Working Group
Double whammy bingo success!!!!!
You know those chemicals I have recieved? Well from the four, two have excellent curing behavour! They react with UVB light and in combination with Benzophenone and combines UVC and UVB irradiation I get fantastic curing at depths of +/- 1mm below 10 minutes of irradiation!!
Here is the cheapest of both, called Benzil:
This one needs combined UVC/UVB irradiatio
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spota
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Polymer Working Group
Actually near UV photoinitiators are the most expensive ones.
I have just received a couple of chemicals that are less expensive and that I will test and hope to see some results in those wavelengths. But I'm not sure yet they will work well enough.
I have found some leds that emit in th enear UV bands too. They come with colimating lenses and I guess it's probably cheaper and easier to build th
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spota
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Polymer Working Group
The cheapest types of photoinitiators work well with what is called germicidal UV fluorescent lamps. This is the cheapest combination I have found by now.
There are some Leds I hav found lately that would fit into some photoinitiator spectra, but they have quite a low intensity (watt/cm
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spota
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Polymer Working Group
@ Jay: Yes, even for the UV-C type radiation which doesn't penetrate deep into the skin, and generally speaking, UV radiation is not good for you. The hyperbolic reflector is thought to direct the rays towards the printed resin parts only, but there still will be stray radiation escaping the apparatus. The best way to shield the thing, short from having the RepRap in a closed room, is to build a
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spota
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Polymer Working Group
Actually, th etime is more than enough. Stopping UV irradiation stops the curing process.
Curing time is currently below 10 minutes and can be adjusted to greater values if needed. I have spotted a lamp and am designing a hyperbolic reflector that will reduce this time to below 3 minutes and improve curing depth.
I'm currently also working on accelerating the curing process to below 1 minute irr
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spota
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Polymer Working Group
Although lately I have mostly been busy mixing heat triggered curing resins (Furfuryl Alcohol and such) I have made some very important progress on the UV curing resins as well.
I was toying around mixing different kind of resins and seeing how those compounds improved the polymer properties. The two big problems I had remaining on the researched mixes I discovered were 1) surface wrinkling due
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spota
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Polymer Working Group
Sorry, I tried to post something in this thread before but somehow my firefox shunted and all my post was lost!
I see now that most of what I wanted to say has peen already said, so yes. PU is great if you manage to dispense it fast enough. Polyester hardens slower and epoxy is also an alternative. Maybe using some sort of helicoidal mixer head would solve the problem of syringe clogging. you c
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spota
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Plastic Extruder Working Group
I'm not really sure but the fact is that it doesn't really need to block UVs as standard glass does that pretty well.
Nevertheless there are plastics, or better said additives that make a transparent plastic become UV filtering. You will just have to ask for it if you want to have that characteristic, but chances are that they will make you pay $$ for an otherwise quite cheap to achieve UV blocki
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spota
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Polymer Working Group
Better shield with any type of opaque material, kind like a box and put a lid on top. make it a glass lid or if you need continuous monitoring, insert a webcam in the box.
That would be the easiest way. Or else, just start the job and leave the room while it's working.
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spota
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Polymer Working Group
My wager is that nylon will be problematic to print.
As Viktor says, the stuff you get when mixing the adipic acid with a diamine, for example, releases molecules of water that need to be carried away or they interfere in the properties of the end polymer.
I would rather look into Polyurethanes: polyols and diisocyanates can produce very hard and tough polymers. They can also be bough as bi-comp
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spota
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Plastic Extruder Working Group