Bunny and Bear (BNBSX) Short Ears MK3S, extruder - added Mosquito option  

RE: Bunny and Bear (BNBSX) Short Ears MK3S, extruder - added Mosquito option

(Sorry, I still have major issues figuring out this new forum's picture functionality.

RE: Bunny and Bear (BNBSX) Short Ears MK3S, extruder - added Mosquito option

After disassembling my BNBSX to exchange the broken sensor flag thingie (thou shall not be careless when removing the sensor :-() I noticed after reassembly that my extruder motor is slightly tilted forward (can be observed when comparing the gap motor and extruder body). I didn't notice that before but also I didn't look as close before. I reassembled but still it is tilted. So far it seems that no printing issues arise from that but I'd like to know to find the cause. The extruder motor pulley is long enough to compensate for the resulting tracking misalignment so I think there is no immediate call for action. I've carefully checked that all bolts are tightened so I do not think the issue results there.

@guy-k2 do you have a clue what might be causing this? Is this intentional and I missed it during initial assembly? 

RE: Bunny and Bear (BNBSX) Short Ears MK3S, extruder - added Mosquito option

Is the filament sensor working? I ask because motor plate tilted forward suggests the sensor armature wasn't pushed out of they way as the motor plate was attached. It can get jammed if it isn't pushed out of the way with a filament. That would leave the motor plate tilted forward, but would also make the filament sensor non-functional.

RE: Bunny and Bear (BNBSX) Short Ears MK3S, extruder - added Mosquito option

Almost forgot... The motor plate and main extruder pieces have shallow interlock pins. If your print has either the holes partially block or the pins a bit large, they won't snap together easily. That is probably the most likely reason your extruder isn't fitting back together fully.

RE: Bunny and Bear (BNBSX) Short Ears MK3S, extruder - added Mosquito option

The sensor is working flawlessly, so that is not the issue. The pins might be the issue - I'll check. If the pins were the issue, wouldn't one see a gap in the extruder housing somewhere? I could not see any but will take a closer look.

RE: Bunny and Bear (BNBSX) Short Ears MK3S, extruder - added Mosquito option

It's been a while but I wanted to update on what was the issue. In fact it was no assembly issue but the part that holds the motor broke. The break would only be visible if you actually removed the IR sensor cover and pulled slightly on the motor (towards the front) - it was not visible at all if not stressed. I've reprinted the part (this time slightly hotter) as I suspect insufficient layer adhesion might have been reason to the failure.
The spot where it broke is a bit baffling as I cannot conceive why there should be stress concentration at that spot. There is nothing to put excessive force on the part there (except if the screw from the carriage was too long and pushed against the motor but I checked that - my screw does protrude a bit but even when tightened does not push against the extruder motors back).

RE: Bunny and Bear (BNBSX) Short Ears MK3S, extruder - added Mosquito option

Thanks for follow up

RE: Bunny and Bear (BNBSX) Short Ears MK3S, extruder - added Mosquito option

Posted by: @guy-k2

Just added experimental Mosquito hot end capability to the BNBSX extruder. The Mosquito compatibility kit for ht extruder hasn't been tested yet, but should let one swap back and forth between Mosquito and E3DV6 hot ends. If anyone successfully runs this with the Mosquito, please let us know.

The BNBSX extruder ( https://www.thingiverse.com/thing:3626993) is an advanced extruder for the MK3S that delivers several advantages....

over the stock MK3S R4

• Geared 1:3.5 for more consistent extrusion.
• Indirect drive isolates filament from extruder motor heat
• Corrected filament path/Bondtech alignment (as in Bear extruder)
• Lower total mass by about 80 gm
• Extreme rearward motor position reduces moment arm
• Two, swappable filament sensor systems (armature for single filament, internal lever for MMU2S)
• Internal filament sensor lever eliminates Prusa filament sensor chimney on MMU2S
• Internal filament sensor lever allows full opening of idler door
• Single screw tuning of MMU2S filament sensing
• New MK3S sensor armature design eliminates steel ball rattling
• Provisioned for LED filament sensor indicator mod
• Only one magnet needed for filament sensor
• Easy motor plate and hot end removal for service
• Separately printable hot fins for heat resistance
• Hot fins tightly encircle hot end.
• Replace heater cartridge or filament sensor without full tear down.
• E3DV6 or Mosquito hot end capable (if experimental Mosquito compatibility kit used, https://www.thingiverse.com/thing:3651160 )

The extruder should be used with its special "short ears" version of the Bear axis and the BNB Universal X-carriage. Please do not try to run this on a standard Bear axis or on a different x-carriage.

 

 

 

 

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RE: Bunny and Bear (BNBSX) Short Ears MK3S, extruder - added Mosquito option

https://www.thingiverse.com/thing:3626993

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