Mounting Plate for 2 to 1 Mixing Extruder for Geeetech Prusa I3 by DougInAZ

Last crawled date: 3 years ago

Update 12/8/17 It looks like this mix/dual extruder could be adapted to a radial fan in the same way I am modifying the 2 in 1 out switch extruder Thing I made. If you have an interest in helping to develop this, let me know and I'll make a duct and transition piece that you can print and evaluate with a 30 (or 40) mm axial fan. If it looks promising, then I'll make the mounting parts for the fan and the transition piece for a radial fan.
Update 1/24/2007
I added some info about my experience with the Cyclops Clone 2to1/Mix extruder near the bottom of this section.
UPDATE 4/23/16
I added a plate that allows you to attach a 40 mm fan to the 30 mm fan mounting holes on the Geeetech single extruder bracket that I use with the mix extruder plate. Use 3 mm cap screws to mount the plate to the bracket and 3mm screws or sheet metal screws that cut threads into the bottom holes of the plate. Use a little heat on the screws to prevent cracking the plate as you cut the threads into the hole.
This mounting plate allows you to attach a 2 to 1 mixing/switching extruder to a single extruder mounting bracket attached to the X carriage of a Geeetech I3 printer. In addition there is a spacer, two of which may be needed, depending on how you mount the extruder, to ensure the hot end is lower than the X axis carriage plate.
I mounted all the hardware with M3 screws. The thickness of the mounting plate was sized to make use of some 8mm M3 button head screws I had on hand. You can adjust it to meet your needs. I mounted the bracket upside down and used longer M3 screws in the lower band of the upper linear bearing to attach the bracket, rather than M4 screws as intended. I'm not sure that's the best solution to get the hot end below the carriage without loosing any more Z axis capacity than necessary.
The photos show one shot of the mix extruder and two of the extruder with one of the original hot ends that were furnished with the MK8 extruder. There was a defect in the mixing block (see PLA oozing out of the heater cavity) so I reverted to a single extruder using the parts furnished with the mixing extruder. You can buy extra throats for the block so you can quickly switch from a mix/switch situation to a dual extruder with two hot ends. Dealing with the switch with the firmware may not be so easy. Look for the parts on Aliexpress and eBay. The single extruder bracket is available from Geeetech also.
The mounting bracket has hole spacing for a 30 mm fan. I hung a 40 mm fan on it temporarily.
In order to use this effectively, it looks like different firmware will be required. It appears that Repetier firmware has capability to handle mixing extruders . Maybe you can define extra virtual extruders to use when switching to a dual hot end configuration.
update 1/24/17 notes about mix extruder
I switched to Repetier FW on the printer and defined a dozen mix ratios in virtual extruders within Repetier Host.
It does work to combine two filaments in the ratio you select, but it does not truly mix the two filaments. The extruded filament shows the two filament colors prominent on the edge of the extruded thread, and a fair amount of mixing in the center of the thread. This results in an object that has a different color depending upon which side of the filament thread you are viewing, i.e. if you print a cube, one side will favor filament A and the other will favor filament B. It's an interesting effect, but not a true mixer.
There can be a significant problem with filament melting too far back in the throats of the extruder block. This can cause a flow stoppage, especially if you use a low flow on one extruder. Geeetech limits the flow ratio to something like 96/4 on the M201 printer, and I can see why. I wouldn't recommend even trying a 100/0 ratio until you have it well proven. I believe the problem I saw is due to the poor design of the clone throats; the heat break area is not thin enough, and the upper block has to handle more heat than the original Cyclops part probably does.
I attached a 30 mm fan to the block. Get a good quality fan, you need a lot of cooling (if you are using a clone with poor heat breaks). I also added small aluminum heat sinks to every bit of the upper block that I could. That helped a lot, but was not as reliable as I hoped for at high flow difference between the two sides.
I finally insulated the extruder block with thin cardboard on all 6 sides. I used cereal box type paper. That made a significant difference in the ability of the heater controller to hold the temperature of extruder. The main effect though, I believe, is that since the heater can run at a lower duty cycle with insulation on the extruder block, there is less heat flowing into the upper block, and the filament is staying below the melt point farther down the throats of the extruder block, and it probably now works as well as it can. Again, probably not a consideration on the original E3D part.
The same problem is evident if you switch to two extruder blocks and try to use it as a dual extruder machine. There is a new 2 to 1 switching extruder from a Chinese supplier that looks like it will work as a true switcher and will avoid the problems with two streams of fluid filament by retracting the unused filament back into the cool zone when the tool is switched to the other extruder.