So while I plan out my personal printer (Basically incorporating all the changes I have made to my MAX + a little more ) I am designing and building a basic filament extruder. A member of my family is a polymer chemist and is looking into the feasibility of certain plastics as 3D printer filament. I have compiled a basic parts list, none of the materials like the framing wood and 3D printed parts are included, as well as parts that I already have.
I think you will have trouble getting consistent performance with an auger bit, as the genuine articles have a varied lead over the length of the screw, and/or varied minor diameters, then again, it may be nothing. I also feel that a single heater may be insufficient and sub optimal. I would prefer to have them designed so as to have control over the temp at multiple areas along the extruder, even if it raises costs. But then, the retrofit would not be too hard to do. I would also prefer to use a taper bearing, although it's overkill and would raise costs. But then, I've worked with enough equipment where a few dollars here or there would have made it much better, so I tend to say screw it and give each sub-assembly 20% or 20$ of room to go for not bare minimum parts, whichever is more. Which does mean that my designs are rather over engineered and more expensive than they need to be. But most of them don't break (At least not in ways I could have expected while designing them)
Machines:
Rostock Max V2, Duet .8.5, PT100 enabled E3D V6 and volcano, Raymond style enclosure
Automation Technology 60W laser cutter/engraver
1m X-carve router
also feel that a single heater may be insufficient and sub optimal. I would prefer to have them designed so as to have control over the temp at multiple areas along the extruder, even if it raises costs
The plastic would be pulverized, and I had thought it would only really need to be heated at the very end, please correct me if I am wrong. Also why would you prefer a taper bearing?
Edit: Ill post a quick mechanical drawing tonight to show what I'm talking about.
It only needs to be heated at the very end, but if you only have the end heated, you may not get good heat transfer to the middle of the barrel, which may be part of why some feed screws increase the minor diameter at the end. This could result in half melted feedstock making it to the nozzle, which would eventually melt, but would likely cause hiccups in feeding it in. A second heater halfway down the barrel to bring the temperature up closer to melt point before you get to where you need it would not be too bad on price and control overhead.
As for the taper bearing, there is both rotational force from spinning the thing, and the push from feeding plastic, especially if it jams. Almost certainly overkill, and I haven't done any sort of calculations as to the forces involved. But as a gut reaction I favor it.
Machines:
Rostock Max V2, Duet .8.5, PT100 enabled E3D V6 and volcano, Raymond style enclosure
Automation Technology 60W laser cutter/engraver
1m X-carve router
I'm excited to watch this project unfold. I've been thinking about making a filament extruder lately. I could also use a 3mm extruder with a 1.75mm nozzle Seems like the Ultimaker (and other) samples pile up and could be put to better use.
Xenocrates: What about running 2 heaters off of the same PID control module (see above image. sorry for poor quality, this was drawn in about 30 seconds. I will be putting CAD files up soon)? Is there any reason the one in the middle of the barrel would have to be at a different temperature?
And on the subject of bearings I did a little research and the force exerted from the feeding of the plastic is not that much, and I believe I will give it a shot with the axial bearings first. I figure that I will take the gamble on it because I feel it has a high chance of working and could keep costs down. Also I would only be extruding a few meters of plastic at a time, as this is for a research project where limited quantities are available.
Personally, I would run three heater bands on it, to make it easy. Main heater connected to the PID module on it's own. Two others in series with each other (and parallel to the main heater), with a smaller gap between the middle heater and the main one as compared to the middle and the end heater. That way your temperature comes up sharply at the end, you don't need any resistors to dial down the heat on the one that isn't at the end of the barrel.
The reasoning behind wanting the rest of the barrel at a different temperature is partially for the sake of not having it go molten before it hits the end of the barrel, as liquids are somewhat harder (Although far from impossible) to move with a screw. It would also reduce the chances of having anything get overheated and having problems from the materials decompose at temperature (Such as how PLA and PETG can form crystalized drop things.)
Machines:
Rostock Max V2, Duet .8.5, PT100 enabled E3D V6 and volcano, Raymond style enclosure
Automation Technology 60W laser cutter/engraver
1m X-carve router
Xenocrates wrote:Personally, I would run three heater bands on it, to make it easy. Main heater connected to the PID module on it's own. Two others in series with each other (and parallel to the main heater), with a smaller gap between the middle heater and the main one as compared to the middle and the end heater. That way your temperature comes up sharply at the end, you don't need any resistors to dial down the heat on the one that isn't at the end of the barrel.
Any way you could sketch a quick diagram? I think I see what you mean just not quite sure. The explanation makes sense.
You weren't too clear about which diagram you wanted, so I drew both a physical (Showing approximate placement), and an electrical, showing wiring placement. Note that the numbering is consistent.
Of course, there is no real reason to wire H2 before H3, it might even make more sense to wire H3 before H2, so as to reduce the amount of wire near the barrel. depends on you.
Machines:
Rostock Max V2, Duet .8.5, PT100 enabled E3D V6 and volcano, Raymond style enclosure
Automation Technology 60W laser cutter/engraver
1m X-carve router
Xenocrates wrote:You weren't too clear about which diagram you wanted, so I drew both a physical (Showing approximate placement), and an electrical, showing wiring placement. Note that the numbering is consistent.
20160406_202714.jpg
Of course, there is no real reason to wire H2 before H3, it might even make more sense to wire H3 before H2, so as to reduce the amount of wire near the barrel. depends on you.
My apologies, the mechanical was what I had questions about. That makes a lot of sense. I will update this thread with CAD files by the end of this week to clarify some things.
Update! got most of the parts, I'm just waiting on the heaters, insulator tape, and bearings now! Pics soon! (Also CAD file is coming along, still not ready to share yet)
And now it fits in the aluminum tube I bought. It is very snug and will stay in with no need for a set screw (I will be installing one just in case however).
[img]http://i.imgur.com/mNog4Mi.jpg[/img]
I have moved on to machining a heater block of sorts. This block will house the two heaters closest to the nozzle (they need a minimum 1.00 in OD o clamp around the pipe, hence the need for the bulky heater block). In addition the large bulge in the center will be where the thermocouple is inserted. This big heater block should also keep temps relatively stable because of the additional thermal mass. I will be using JB weld to attach it to the long, smaller tube that the nozzle goes into. It's not ideal but this setup should work just fine. I will post more pics when I finish machining it, the block still has a little bit to go.
) I am designing and building a basic filament extruder. A member of my family is a polymer chemist and is looking into the feasibility of certain plastics as 3D printer filament. I have compiled a basic parts list, none of the materials like the framing wood and 3D printed parts are included, as well as parts that I already have.
Seems like the Ultimaker (and other) samples pile up and could be put to better use. 
