I seriously question the reasoning behind typical extruder designs.
All you need to make a much better extruder is
drill press
sheet of aluminum
hacksaw
ceramic rods
teflon tubing
I’ve been using it for months and there are no problems at all.
the transition point from hot to cold is shorter than any extruder on the market (so there’s no clogging, because there’s not hot material for 2+ inches)
there’s no fan blowing right over hot metal and working your heating element (so you save a ton of energy and the extruder heats up many times faster)
it’s easier for the pid loop and it maintains temperature better because the element doesn’t need to work as much
So I question why do all extruder designs us the same non thermally sound design? Why not thermally isolate the transition point from everything using proper materials rather than just try to cool it with a fan?
@Andrew_Hodel I am actually struggling with my cheap hotend design and curious about what you have now Do you have more pictures of your setup ? I can’t see the whole assy.
The common wisdom is that a simple hot end is fine for low temperature plastics, but high temperature ones (like nylon and polycarbonate) need active cooling. What is the highest temperature you have printed at with your hotend?
That looks considerably bulkier than a J-head. Too bad the genuine ones are out of production.
The E3D type design has a very thin cross section of stainless steel, which has a lower conductivity than other readily available metals. You can’t have PTFE in the hot zone if you want to go higher than 250˚C. I’ve used E3D v6 up to 410˚C.
Looks like you just have a Teflon tube going into the heater block?
That design is old. As old as RepRaps can get. Teflon may not melt at high temps, but it will soften and deform. Previously PEEK was used to keep the shape, and is still used in Jhead hotends.
You can’t just think about thermal isolation, you need to think about longevity, material properties, thermal conduction, and nozzle pressure.
@Eric_Davies 250C for 5+ hours, multiple times and no change in the durability of the teflon, as you can see the teflon is supported by a higher aluminum block which acts as a strain relief.
@Jeff_DeMaagd It’s much less bulky on the Z axis. On the X axis you can just move the exterior plates closer to the center and match a J-head for X axis usage. This particular setup was designed to fit multiple extruders and in that case it’s far more space efficient that contemporary designs.
@Stephanie_A the extruder has a teflon tube going into a heater block which is isolated by ceramic rods.
As already mentioned by @Maxim_Melcher every hotend has teflon inside of it which is experiencing the same printing temperatures. Here there is actually less heat on the full length of the teflon and there are no spaced chambers for backed up semi-melted filament to get stuck.
As well, it is supported at the top about 1cm above the transition point as a strain relief, so the hot part of the teflon gets no mechanical stress.
Here’s the Millcrum code which can generate the GCODE for your CNC or Waterjet to cut 1, or an entire 4x8 sheet if you prefer - http://pastebin.ca/3568267
Other people bashing me, why not just spend a day and make one then test if for yourself… you’ll see.
@Jeff_DeMaagd Here, do this and you have the dimensions of a jhead with less Z usage, as I mentioned the one in the photo is for multiple hotends.
It is not that difficult, but when you have a length of shaft where the whole thing is hot and a fan is blowing on it you are wasting energy and you have a longer distance of heated material which means less extrusion accuracy and more chance for a clog.
Enjoy it, but thermal coefficients and material ratings don’t lie. It’s a better design.
PTFE tube lined hot ends aren’t very good. Two big downsides:
They’re an insulator between your heat source and melting plastic. That cuts your top printing speed (in volume flow terms) by a large amount compared to an all-metal design, on the order of 50% top print speed reduction depending on the design.
They’re a major maintenance consumable if you print hotter than ~240C or so. It’s a “time at temp” decay process – the PTFE lasts for many months at 230C, maybe a few weeks at 260C, or a few hours at 280C. Once the PTFE starts to appreciably pyrolyze, it loses the non-stick properties that make it useful in hot ends. Basically limits you to PLA and ABS and some modern alternate blends specifically formulated for PTFE-lined hot ends. You can’t print high-temp materials for extended periods: the tube fails too fast. That doesn’t matter to everybody, but it’s a big deal to some people.
@SirGeekALot I agree with you, it would get across even better if it had a half naked woman in the viewport.
Although I don’t know if people would read the reasons then, and I’m not really trying to get a point across or sell anything here… I’m just saying, hey!
I’d actually prefer if someone who has the patience to deal with marketing would turn it into “hot shit”. At least it would save a few man hours of people cleaning hot ends that are poorly engineered and get people to realize they are wasting their money.
@Ryan_Carlyle A PTFE liner insulating the plastic will reduce the efficiency with which heat is transferred to the plastic, but a long hot zone (like in a Volcano hot end) should get you that volumetric speed back, right? It will be a more gradual heating (and @Andrew_Hodel 's claim of the shortest thermal transition is nonsense because even if the transition zone is short on the outside, the PTFE insulation makes it longer on the inside), but you can get the same overall rate of thermal transfer to the filament that way.
@Maxim_Melcher What layer height was that? Feedrate doesn’t mean anything to the hot end, it’s FLOW rate that you’re limiting with the PTFE liner. Multiply [layer height * extrusion width * feedrate] to estimate volumetric flow rate. A PTFE-lined hot end will have a lower top volumetric flow rate compared to an all-metal hot end with similar geometry (eg melt zone length). That’s basic physics, you can’t get around it. PTFE has ~1/400th of the thermal conductivity of brass.
