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FAQ:
Q: Do you offer 24V fans and heaters?
A: I can only offer 12V electronics at this time.
Q: Is Prometheus offered fully assembled?
A: All of the Prometheus Hot End perks require assembly. Kit assembly requires basic soldering skills.
Q: Do you offer a heat sink with bowden integration?
A: Update: All Prometheus Hot Ends can be used in both standard or bowden setups. If you want to use Prometheus in a bowden setup then simply select a bowden coupler and required tubing perks along with your Prometheus Hot End perk!
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Summary
This
new hot end design allows RepRap users to experiment with all aspects
of thermoplastic extrusion. Its actively cooled all-metal
construction is very durable and can easily withstand the high
temperatures required for extruding thermoplastics like Nylon and
Polycarbonate, while its unique modular design enables the user to
customize the "melt-zone" length, “transition-zone"
length, and thermistor position according to their needs.
This
compact, reliable, and precise hot end is the all-in-one solution for
your 3D printer!
Design
Features
- Durable, actively cooled, all-metal construction for high-temperature
extrusion up to 300C.
- Modular design with
user-variable "melt-zone"
length,
"transition-zone" length,
and thermistor position for
your specific
need or experimentation.
- Precision CNC-machined parts featuring a
1-Piece
Stainless Steel Nozzle
that is
internally polished
to prevent jamming
(especially when printing PLA).
- 1-Piece
Stainless Steel
Nozzle
eliminates all leaks
and clogs caused by internal "melt-zone" junctions.
- Thermistor
is now secured by
a cap
screw for increased
reliability and aesthetic appeal. No more messy Kapton Tape wrapped
around the heater block.
- Support for an additional
“redundant”
heater block thermistor
as an optional precautionary
measure.
Compact design conserves z-height and easily
fits standard extruder
bodies.
Customizable
design makes it very easy to adjust the nozzle height for dual
extrusion setups.
- Assembled weight is only about 30g
making it ideal for high-speed
printing on Delta and
“Ultimaker-style” 3D
printers.
- Printed successfully for hundreds of hours with PLA, ABS,
Polycarbonate, and Nylon 618.
-
Number of hot end leaks, clogs, and jams experienced during testing:
0 (zero!).
*Select
your perk on the right and help make the Prometheus Hot End a
reality!
Testing
To ensure reliable precise performance the Prometheus Hot End has been tested extensively. Prometheus has printed successfully for hundreds of hours in PLA, ABS, Polycarbonate, and Nylon on several Prusa I2 printers without any leaks, clogs, or jams. All testing was done with a 16mm “melt-zone” length and 2-3mm “transition-zone” length.
I have tested the Prometheus Hot End with various high stress printing scenarios without any issues: I have printed PLA at very low extrusion rates for long periods of time; I have printed Polycarbonate at 300C above a 140C heat bed in an enclosed print chamber; I have tested rapid successive retractions and 10+ hour long prints.
I have also tested the Prometheus Hot End with the lowest quality PLA on the market. I had an old roll of neon green ESUN PLA that had been left in an uncontrolled environment throughout a very hot and humid summer in Toronto. It was wavy and swollen yet I still managed to print a decent looking Yoda head and Bhudda bust at 100 microns without any issues!
In addition to its admirable reliability, Prometheus has demonstrated great precision in the prints that it produces. I have managed to print down to 50 microns on my wobbly Prusa I2 printers! Most of my test objects were printed at 100 microns with amazing results that easily match objects I printed with my E3D hot end.
YouTube: On my YouTube Channel you can watch several videos of the Prometheus Hot End printing PLA, ABS, Polycarbonate, and Nylon 618. Below you can watch a short video of Prometheus printing a Zig-Zag Vase in Nylon 618 at 200 microns (sorry for the poor audio quality):
Flickr: On my Flickr Photostream you can view over 300 pictures of objects that Prometheus has printed. The pictures below are a few examples of objects I have printed with Prometheus.
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*Keep in mind that ALL of these objects were printed on my wobbly old Prusa I2 printers. If I can get these results on my old printers, just imagine how well Prometheus will perform on a rigid Prusa I3, Mendel 90, or Solidoodle!
Introduction
Hey Guys! My name is
Eric (user “RP Iron Man” on the RepRap forums) and I have been actively involved in the RepRap community for over a year. Before I became involved in entrepreneurial work, I worked at a staging company where I did Carpentry, Welding, CAD Design, CAM, CNC Programming, and Industrial CNC Operation. I also did significant Project Management on $8000 projects for real world clients with tight deadlines. Eventually I quite this job and started to focus on turning my RepRap hobby into a business. I took an immediate interest in hot end design as I saw the need for many improvements.
As our 3D printing community
continues to explore new boundaries, exciting high-temperature
plastics like Polycarbonate and Nylon are becoming widely available.
As a result, RepRappers are replacing their old PEEK insulated
J-Heads with new all-metal hot ends that are capable of printing at
these high-temperatures. With a plethora of new hot end designs, all-metal hot ends are
becoming the ubiquitous all-in-one solution for RepRap 3D printers
around the world.
Despite these recent
innovations, I have noticed that the new all-metal hot ends have the
same static design features of a fixed "melt-zone",
"transition-zone", and thermistor position. While these new
designs satisfy the need for reliable high-temperature extrusion,
they seem to ignore the fact that users may require different hot end
parameters for their specific needs or simply for experimentation.
It
didn't seem like anyone else had solved this problem yet so I decided
that I would take on this project. Finally, after months of
designing, three generations of prototypes, and hundreds of hours of
printing, the Prometheus Hot End was born!
Modular
Design
The
modular design of the Prometheus Hot End consists of three custom
designed and precision CNC-machined components: the Aluminium Heat
Sink, the Aluminium Heater Block, and the 1-Piece Stainless Steel
Nozzle. Every component of the Prometheus Hot End was carefully
engineered for optimum performance.
Aluminium
Heat Sink
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The
Aluminium Heat Sink is
precision CNC-machined and polished for a beautiful surface finish.
Aluminium was chosen as the material for the heat sink due to its
high thermal conductivity and high machinability. The heat sink
incorporates a standard groove mount design for compatibility with
standard extruder bodies. Fins
are turned into the heat sink to maximize cooling and symmetrical
faces are milled on each side to allow a 25mm cooling fan to be
mounted directly to the heat sink. This design feature eliminates the
plastic fan duct, decreases mass, and increases cooling efficiency.
The
heat sink is also threaded from top to bottom to allow the 1-Piece
Stainless Steel Nozzle to be threaded into the heat sink and fastened
at the bottom with an aluminium hex nut. A
PTFE tube is inserted from the top and meets
with the nozzle
in the threaded portion of the heat sink to facilitate a low friction
filament path into the nozzle.
*Note:
This PTFE tube is inserted in the “cold-zone”
of the hot end in the actively-cooled
heat sink so it is NOT
subjected to high temperatures.
Aluminium
Heater Block
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The
Aluminium Heater Block is
precision CNC-machined and polished for a beautiful surface finish.
Aluminium was also chosen
as the material for the heater
block due to its high thermal
conductivity and high machinability. The
Aluminium Heater Block is simply designed with a 5.5mm
hole for the heater, two thermistor mounting holes, an
M6 thread, and a
top-to-bottom threaded hole for the 1-Piece
Stainless Steel Nozzle. The
nozzle
is threaded through the top and secured with an aluminium hex nut.
Additional aluminium hex nuts
can be fastened against the
heater block to customize the
“melt-zone” length.
The
heater is a 12V 30W through-hole resistor heater and
the thermistor is a Semitec
100K glass bead thermistor which measures up to 300C. The heater
block features an additional thermistor hole which
is useful if you want to add
a second “redundant” thermistor for added reliability. Note that
the heater block pictured above has been slightly revised according
to the technical drawings below so both thermistor holes are sized to
fit the Semitec 100K glass
bead thermistor.
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I
have recently made some slight adjustments to the heater block in
order to improve a few details of the design. I think the most
important improvement is that
the thermistor will no longer
be secured to the heater
block by Kapton Tape.
Wrapping Kapton Tape around
the heater block is a messy, unreliable, and unattractive way to
secure the thermistor so I really wanted to do away with this
approach.
While
discussing this with a few people on the forum, Brian
(RepRap user “bstott”) suggested this method to secure the
thermistor leads. As
illustrated in the technical drawing above, a
cap
screw with a small OD washer
secures the thermistor leads
and eliminates the possibility of the thermistor falling out. This is
a significant improvement to both the reliability of the thermistor
and the aesthetic appeal of the hot end. The
M6 threaded hole also allows for a future upgrade to standard M6
threaded thermocouples. All
hot end perks will ship with this improved heater block design.
1-Piece
Stainless Steel Nozzle
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The
1-Piece
Stainless Steel Nozzle is
precision CNC-machined and
polished for a beautiful surface finish. Stainless
Steel was chosen as the material for the 1-piece nozzle due to its
low thermal conductivity, low
thermal expansion, and high
strength. This design
replaces the standard nozzle and heat break combination in most
all-metal hot end designs with a 1-piece nozzle that eliminates
all internal
"melt-zone" junctions.
Internal
"melt-zone" junctions are
the leading cause of leaks and clogs in conventional hot end designs.
Molten plastic can leak through the junction or can get stuck in the
junction, decompose, and the
charred
remains
can then flow down and clog the nozzle orifice. I
have experienced these problems even with the best hot end designs.
With my 1-piece nozzle/heat-break design I have completely eliminated
all internal “melt-zone” junctions and thus eliminated the
possibility of "melt-zone" related leaking or clogging.
With several hundred hours of
printing and not a single leak or clog, the empirical results speak
for themselves.
In
addition to the 1-piece design, I was meticulous about custom
burnishing the internal
pathway of the nozzle to avoid
the possibility of the filament jamming. Filament jamming is
the most significant problem
associated with
all-metal hot ends. While hot
end “clogging” relates to the obstruction of the nozzle orifice,
hot end “jamming” is associated with the forces involved in
filament extrusion. In order to extrude filament successfully, the
applied force of the extruder drive must be greater than the opposing
force of friction.
Friction
occurs most prominently in the “transition-zone” of the hot end
where the plastic is changing from solid, to rubbery, to liquid. The
plastic remains solid in the "cold-zone" until it is heated above its Glass
Transition Temperature (Tg) in the "transition-zone" at which point it is "rubbery" until it is heated
above its Melting Temperature (Tm) and turns to liquid in the "melt-zone". In
its “rubbery” state at temperatures between Tg and Tm, the
plastic turns soft and expands to form
a plug in the “transition-zone”.
This plug of soft rubbery plastic
is the most significant source of friction in the hot end and
is the leading cause of hot end jams.
The
standard J-Head hot end design features
a low friction PTFE
liner that extends the full
length of the “transition-zone”
and greatly reduces
the friction caused by this
plug. However,
all-metal hot ends do not have a PTFE lined “transition-zone” so
friction becomes a significant issue especially when
printing PLA. To overcome
this problem I custom
burnished
the full length of the
internal bore
of the nozzle. The burnishing
procedure polishes
the internal pathway of the
nozzle to a near mirror
finish ensuring that it is
smooth enough to eliminate
jamming.
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Customizing
the “Melt-Zone”, “Transition-Zone”, and Thermistor Position
Introducing the
"melt-zone" length, "transition-zone" length, and
thermistor position as fully customizable variables is what makes the
Prometheus Hot End truly unique. The "melt-zone" and
"transition-zone" length are two of the most significant
design features of a hot end which govern the extrusion behavior
while the position of the thermistor greatly influences the thermal
control of the "melt-zone". In conventional hot ends these
design features remain fixed and are optimized for a specific need,
which allows for very little flexibility and experimentation. The
Prometheus Hot End was designed specifically as a flexible platform
that would enable RepRap users to experiment with the effects of
different "melt-zone", "transition-zone", and
thermistor configurations on the extrusion behavior.
The Prometheus Hot End
was purposely designed so that these three parameters could be
adjusted as easily as possible. The “melt-zone” can be lengthened
simply by threading additional aluminium hex nuts against the heater
block. As a result, the position of the thermistor in the “melt-zone”
is user-customizable based on how you position the heater block and
additional hex nuts on the nozzle. The “transition-zone” is
easily set by increasing the distance between the heat sink and the
heater block.
The pictures below
illustrate various "melt-zone", "transition-zone",
and thermistor configurations that are possible with the Prometheus
Hot End.
CZ = "Cold-Zone" Length
TZ = "Transition-Zone"
Length
MZ = "Melt-Zone" Length
TP = Thermistor Position
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Advantages
of a Customizable Design
The "melt-zone"
length, “transition-zone" length, and thermistor position are
three key parameters that govern hot end performance so enabling
user-customization of these features has some important implications.
While this customizable hot end design allows for some interesting
experimentation, it also allows each user to customize the
performance of the hot end according to their specific needs.
The
“transition-zone": Enabling a customizable
“transition-zone" length allows the user to set a very short
(2mm-3mm) “transition-zone" to increase the reliability and
extrusion response of the hot end. The length of the
“transition-zone" governs the length of the soft rubbery
“transition-zone" plug which is the most significant source of
friction in the hot end and is the leading cause of hot end jams.
This plug also increases hysteresis (slower extrusion response time)
when extruding at very low flow rates. Configuring a short
“transition-zone" decreases the length of this plug and
therefore increases reliability and extrusion response of the hot
end.
The “melt-zone":
Having a user-customizable "melt-zone" is arguably the most
significant advantage of this customizable design since the
requirements for "melt-zone" length vary considerably
between applications. The length of the "melt-zone"
determines the volume of molten plastic in the hot end and therefore
is responsible for the amount of “ooze”, extrusion response,
retraction response, and maximum feed rate of the hot end. A shorter
"melt-zone" means less molten plastic in the hot end and
results in less “ooze”, faster extrusion response, and more
effective retractions at the expense of a lower maximum feed rate. A
longer "melt-zone" means more molten plastic in the hot end
and results in a higher maximum feed rate at the expense of more
“ooze”, slower extrusion response, and less effective
retractions. Consequently, a short "melt-zone" would be
ideal for printing detailed objects at lower extrusion rates, while a
longer "melt-zone" would be the better configuration for
high speed printing.
The
thermistor
position:
Customizing
the position of the thermistor in the "melt-zone"
is
also a useful feature of this flexible hot end design. The
thermistor position determines the accuracy of the temperature
reading and the thermal response of the hot end. Generally,
there are a few causes of heat loss in the "melt-zone":
heat loss due to thermal radiation of the aluminium parts, heat loss
through the “transition-zone”
to the actively cooled “cold-zone”,
heat used to melt the plastic entering the "melt-zone",
and
heat transferred to the extruded plastic at the nozzle tip. Most of
the heat is dissipated at the top of the "melt-zone"
so it is a good idea to configure the thermistor
position at the top of the
"melt-zone"
to ensure that the temperature is sustained especially at high feed
rates. However, if you are printing very detailed items at low feed
rates and you are more concerned with very accurate temperature
readings at the nozzle tip you may want to configure the thermistor
position at the bottom of the
"melt-zone".
In either case, the
entire "melt-zone"
is aluminium (highly thermally conductive) so the thermal hysteresis
within the "melt-zone"
is not much of an issue at all.
Performance
Expectations
Throughout my testing, the Prometheus Hot End has performed very
reliability and has demonstrated admirable precision in the prints
that it has produced. However, note that my testing results may not
reflect the performance of this hot end in every possible 3D printer
configuration considering the differences in each printer setup.
While I am confident
that this hot end will meet all of your expectations I would like to
remind everyone that this new design (like most all-metal hot ends)
is still considered “experimental” so at this point I cannot yet
guarantee any performance standard.
Open-Source
Design
Of
course, I could not have created the Prometheus Hot End without the
help the RepRap community. Browsing
the RepRap wiki, reading RepRap forum threads, and
discussing various hot end designs with other forum members
has
taught me so much about the intricacies of hot end engineering.
I
hope that I can help refuel innovation within RepRap by making the
technical drawings of the Prometheus Hot End available to everyone. I
am releasing the Prometheus Hot End design under the Creative
Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License
(CC BY-NC-SA 3.0). The drawings are
available here on
my Flickr Photostream so
feel free to check them out!
Recently
we have also been having some detailed discussions about the design
features of this hot end on the RepRap Fourms so if you are
interested in reading into this you can check out this thread.
Why
Indiegogo?
In
order to mass produce the Prometheus Hot End at
a reasonable price, there are
Minimum Order Quantities (MOQ)
that must be met.
I can make small orders with
my own savings but in order
to have the components mass
produced efficiently I need to
meet the MOQ of my suppliers. Soon
after this campaign begins, I am going to make
the initial Early Bird order
from my suppliers for the Prometheus Early
Bird kits
to ensure that I can have the
Early Bird
kits shipped out on time. Your
support will help me meet (and hopefully far
surpass!) the
requirements to begin mass
production. Your help
will also fund
my future
developments. I have many projects that I have on hold and your
support will help bring these future projects to life!
Perks
Once the Campaign is
complete all contributors will be listed in a thank you post on my
website for supporting this project! My website should be up in a few weeks.
This is will give you a general idea of what is included
in the Prometheus Hot End kit perks:
![]()
Both the
1.75mm and 3mm Prometheus Hot End perks ship with a 0.4mm
nozzle orifice. I hope to start testing different nozzle orifice
sizes once this campaign in complete.
Please note that the
Prometheus Hot End is currently designed for direct drive
extruders and I don't have an integrated bowden version available
yet. However, you can easily design a plastic bowden coupling adapter
to use Prometheus with your bowden extruder. Weighing just 30g, the
Prometheus Hot End is ideal for high speed printing on a bowden 3d
printer!
Help
support this project by selecting the perk
that you want. Worldwide
shipping is included in the
price of each perk and
if you select a Groove Mount Plate as
an add-on it will ship with
your Prometheus (1.75mm or 3mm) perk.
The
Prometheus Early Bird
perks are priced lower
and ship earlier
than the standard perks. If you want to get
your Prometheus Hot End early
be sure to select this perk. The
quantity
of Early Bird
perks available is
limited so don't wait!
Note
that the standard perks will be shipped in the order they are
received so be sure to order earlier to receive your perk sooner.
Once this campaign is finished the Prometheus Hot End kits will be
available at a slightly higher price on
my website. I
encourage everyone to take advantage of the discounted prices offered
in this campaign!
The payment method is PayPal, which is of course a very safe way to pay!
Timeline
April
2014 ----------
- Launch Indiegogo campaign.
- Make first order for Early Bird perks from suppliers.
May
2014 ----------
- Early Bird production in progress.
June
2014 ----------
- Campaign ends.
- Make second order for standard perks from suppliers.
- Ship all Early Bird perks.
July
2014 ----------
- Standard production in progress.
- Ship all standard perks in the order they are received.
Risks
There are always risks
associated with scaling a product from prototype to mass production.
In order to minimize these risks, I have split the production plan
into two stages: Early Bird production and standard production. The
Early Bird production run will commence soon after the campaign
begins and will be completed before the standard production starts.
In the unlikely case that there is a defect in product quality it
will be detected in the Early Bird production stage. This minimizes
the risk and allows me enough time to make corrections in the event
that something does go wrong. This precautionary measure will help
support the success of this project under any circumstances.
To
ensure that I can effectively carry out this project, I have
dedicated a lot of time to
finding reliable suppliers. I have assured the quality of all of the
products and I have selected backup suppliers as an
additional precautionary
measure. I have worked with my suppliers
for a long time and we have a very good relationship. I am confident
that the quality of the parts will be top-notch. In
addition, my suppliers have a very large manufacturing facility so
scaling up production to meet increased demand should not be an
issue.
Fulfillment
Design
engineering, prototyping, and testing are just the first few stages
of the project. The perk fulfillment is as important as any stage of
the project and requires just as much forethought. The
project timeline I listed above should give me more than enough time
to fulfill the perks. I deliberately exaggerated the shipping date in
case I encounter any delays with production. Based on my planning, I
firmly believe that I will be able to meet the dates on the
fulfillment timeline. However,
note that there is always a possibility that the perks will be
shipped later than the assigned date.
I will be sure to keep
you informed with regular updates from the start of the campaign to
perk delivery!
Other
Ways You Can Help
Even if you can't afford
to fund my project you can still help! Tell all of your 3D printer buddies about the new Prometheus Hot End and get the word out! Use
the Indiegogo share tools and do anything you can to increase
publicity. Unfortunately, I am not much of a marketing guy and I
don't have many resources for marketing this project so every little
bit of publicity will help make this project a reality.
Thank
you
so much for your support!
Happy
printing :)