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For a long time we’ve wanted to do something that takes care of dual extrusion in a neat and simple package. So we started out with some design objectives:
- Simple and easy to use, mount, and maintain
- Modular, upgradable, and compatible with the v6 ecosystem
- Lightweight and compact
- More cost effective than mounting two E3D-v6 HotEnds side by sides
- Must be a high performance, all-metal, polymer pushing machine
What we actually came up with were two totally new HotEnd products: the Chimera and Cyclops
Lets start out with the simpler of the two; Chimera. A Chimera is a mythical beast composed of parts from different creatures. In this case Chimera is composed of parts from both the E3D-v6 HotEnd and the Kraken, along with an air-cooled heatsink that it shares with Cyclops.
Chimera benefits from all the performance advances and reliability tweaks made to the v6 HotEnds. Chimera uses the same interchangeable nozzles as v6 and is therefore compatible with all E3D nozzles from the v6 ecosystem. We’re also using v6 heater blocks which means easy to set up and maintain clamped thermistors, along with fast heat up times from the clamped heater cartridge.
We’ve applied our specially developed heatbreak internal finishing system from v6 to the Kraken heatbreaks which are also used in Chimera (we’ve actually been doing this for a while on all Kraken breaks now), which, coupled with the nozzle geometry from v6, makes for an incredibly reliable all metal printing setup.
Chimera uses our new milled heatsink which accepts two heatbreaks and cools them with a single 30mm fan. We’re also using the same embedded Bowden couplers from Kraken and v6 to hold in the PTFE tubing that runs right down into the heatbreaks. This makes for an incredibly compact little heatsink with an on-carriage footprint of 30mm x 18mm.
There was no way we were going to use groove mount for this setup, and because we are CNC milling these parts we had some nice flexibility in how we arrange the mounting setup. Simple and easy is best - Chimera mounts with 3 M3 female mounting holes on the top face for attaching to carriages and end effectors that are in the same plane as the bed such as Deltas and Mendel type bots.
We’re also seeing more and more machines with vertically spaced X-Rods like the Prusa i3 machines, so it made sense to include mounting holes on the back side of the heatsink so the hotend can just mount flat against the carriage. The aim here was to make mounting design brain dead simple so that everyone can easily create an effective mount for this new style of HotEnd.
One of the most important features of Chimera is how easy it is to level the two nozzles. The heatbreaks are smooth instead of threaded and slide easily into carefully toleranced holes in the heatsink, where they are secured with set screws. This means that each nozzle can slide up and down a millimeter independently which makes levelling your nozzles with respect to the bed extremely simple, even if your printed parts are a touch off.
Chimera makes a fantastic “mount it and go” setup for dual extrusion using tried and tested v6 and Kraken technology in a cost effective and compact setup. We’re really excited to see what people can do with multiple materials in a single print, soluble and break away supports, as well as multiple colours.
Next lets take a closer look at Cyclops. In Greek mythology the Cyclopes were a race of one-eyed giants who were famed for their ability to build impressive structures. This is of particular relevance to our Cyclops product, which although not a giant in size has a single output nozzle and is certainly capable of building some impressive structures!
During our experiments with colour mixing we noticed that it was, in fact, possible to switch from one solid colour to another. The mixer disengaged extremely quickly with a very low amount of purging and colour bleeding if the internal channels for the molten polymer were correctly arranged. Although we’re still working on getting colour mixing nailed, we saw a lot of potential utility in being able to switch from one solid colour to another rapidly through a single nozzle.
We’ve spent a lot of time carefully tweaking the internal channel geometry of Cyclops to provide really snappy colour switches, while also keeping the amount of pressure needed to force the viscous molten polymer through the channels manageably low. Because this was so hard to tweak and tune we still consider this product to be in the testing phase and are happy to receive any feedback you might have!
Cyclops uses the exact same heatsink as Chimera, which means you get the same small footprint, easy mounting and air cooling. It also means that a Chimera can be converted into a Cyclops and vice-versa. It’s also a pretty rapid changeover so it’s perfectly feasible to have and use both. We offer a “Legendary Kit” which will include all the modular parts you need to create Cyclops and Chimera, allowing you to chop and change to suit your needs.
Cyclops uses its own 0.4mm nozzles as well as heatbreaks with spanner flats so they can be tightened into the block. It of course also has a weird and wonderful block with a labyrinth of small channels through which the molten polymer flows, meets, and eventually ends up exiting the nozzle.
We ran into a few tricky problems with this block. The first was the nozzle: Using a v6 nozzle was off the cards - the fluid dynamics just didn’t work out. Initially we were going to orbitally mill a nozzle into the block as a one piece affair, but eventually we managed to come up with these little nozzles which we’re really happy with.
Sealing was also a real concern. The Cyclops block has 5 holes in it, and some of our prototypes had 6, and we need plastic to only ever come out of one of those holes. The nozzle hole and heabreak hole are taken care of with careful tolerancing and providing the ability to tighten up both the heatbreaks and nozzle using tiny little spanner flats while hot so they seal as the HotEnd cools just like in v6.
We’re then left with the two holes that exist because sadly we are not yet able to drill around corners and needed drill access. Just screwing grub screws into the holes, even with a lot of torque still leaks. Normal industry standard sealing systems like tapered threads, O-Rings, and sealing compounds do not apply to 2mm holes that run at 300°C. Instead we’re press fitting tiny hardened steel ball bearings into the channels while hot using a grub screw to drive the ball into the hole and then retain it. This works perfectly and we’re really happy with it.
We’re also really really pleased with performance, colour switches happen FAST. A small purge of 30mm^3 clears out the previous colour and brings in the next one. We’re using Cura for slicing which is simple to configure for dual extrusion and has really intelligent dual extrusion path planning. Because there is only one nozzle idle nozzle ooze is eliminated and no ooze shield is needed. We’ve been tackling some really challenging dual extrusion prints with great results.[gallery ids="100,101,102"]
With all the above said, there are some caveats to the use of Cyclops. Both filaments absolutely must be present in the heatbreaks before extrusion starts, otherwise there is nothing to block off the empty heatbreak and molten polymer can flow up and out of the open hole. This is not a fun occurance. This also means that during printing the idle extruder must only be allowed to retract by around 2-3mm, not the more standard 10mm or so or the same issue presents. Additionally the pressure required to extrude is a little higher than a standard hotend - we’ve been testing with direct drive airtripper extruders with acceptable results, but we really recommend the use of a geared bowden extruder such as RichRaps geared bowden extruders to ensure that the system always has enough force available. Cyclops only has a single block which melts and holds both materials. This obviously excludes the use of 2 materials with drastically different processing temperatures. We’ve not done extensive enough testing with different materials to make assertions about performance, but we expect that with appropriate purging and on-the-fly temperature changes it should be possible to print polymers with somewhat different processing temperatures in a single print.