Bunny Science Extruder Motor Gearbox

by BunnyScience Apr 11, 2019
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Anyone test out an LDO-42STH25-1004AC short body ?

any assembly videos or step by step guides anyone know of?

No step by step guide was created for this relatively simple project. However, look through the photos and you will find many of the steps illustrated and important details annotated.

That looks like a really nice design! Thanks for sharing it and also thanks for including STEP files! If you have designed this in Fusion 360, would it be too much to ask if you would also share the source file? I have a slightly different belt and different bearings lying around and making them fit would be a bit more comfortable with the original source file. :)

would this fit on a bear extruder? it seems like it could, but I can't tell for sure

Yes. That was the first extruder it ran

While you are at it, grab yourself one of the OMC 1.8 degree short body motors.
It drops the motor mass AND has enough torque to do the job. At $16, it is also a great bargain.

STEPPERONLINE Nema 17 Bipolar Stepper Motor 0.7A 13Ncm (18.4oz.in) 17HS10-0704S

Comments deleted.

so the firmware change is to default esteps * by 3.5?

No. My firmware is only required if you are using 0.9 degree motor. It also changes microstepping, otherwise the EINSY can't keep up with step rate for 0.9 AND gearing. That would require stepping at 7x normal rate - too fast for EINSY. So, with 0.9 motor, my firmware halves the microstepping.

If using 1.8 degree motor, no firmware change is needed. Just set and store e-steps via G-codes

M92 E980

Do you have a Twitter or email? I wanted to ask you a question?

I meant 980.... it seems to be over extruder pretty seriously.

Comments deleted.

If you set e-steps 980, it should not be extruding any more than a direct connected motor with normal e-steps.
Something would need to be messing with the gear ratio to make that kind of change if e-steps are correctly set.

What is your normal e-steps on your printer?

Normal firmware, right?

Just checking that you are not running my 0.9 degree support firmware, but failed to commend out setting of E to 0.9 degree.
That would double extrusion rate.

Your motor pulley is 16T, right?

Yes 16t pulley, Sams belt, stock gear etc. just like you listed. If you’re sure about those Esteps then I know it’s somewhere else.

Thank you for the fast reply. Stock MK3s FW, stock motor. Just the bunny in between! It could be slipping or something. But I thought this would be the first thing to check.

Little help please. The belt 140 2gt 6. Is the 140 total length or tooth count?

L=140mm, W=6mm, 70 Teeth in Closed Loop

Hey if I’m using the stock extruder motor on the MK3 are the E-Steps still 930?

You mean 980.

The stock motor is a 1.8 degree stepper, just like the specified short body unit,
1.8 degree, STEPPERONLINE Nema 17 Bipolar Stepper Motor 0.7A 13Ncm (18.4oz.in) 17HS10-0704S.

Hence, the e-steps would be the same for both 1.8 degree steppers with the 1:3.5 ratio

Set and store e-steps
M92 E980

Which belt drive would you reccomend for a mk3s with mmus2. This one or the mk3s specific one? This design looks more compact.

Depends on whether you envision it as a long term geared solution with less moment arm vs an easy test setup. This gearbox is OK for a quick test of whether gearing helps your print quality. If it does make a difference, I would move on to one of the more integrated solutions.

Our current best extruder setup is the BNBSX short ears MK3S, but that is a much more extensive rebuild than simply bolting on this gearbox or the simple MK3S geared extruder solution.

Will this or any of your gearbox extruders work with the MK3s model that allows the use of the Mosquito hotend?

This gearbox will work. It replaced the NEMA 17 motor. However, our other BNB geared extruders (not this gearbox) will not directly accept the mosquito hot end. It may be possible with a groove mount adapter, but I don't know if you would also need a spacer. https://www.printedsolid.com/products/groove-mount-coupling-with-tapped-holes-for-slice-engineering-mosquito-hotend

[EDIT - Bunnies checked clearances on the BNB Short Ears MK3 and BNBSX Short Ears MK3S. Both left and right paws were squished flat.

No - not enough clearance. It would require a modified version of the extruders to fit the Mosquito hot end. Mosquito is wider than the existing air plenum.

Bunnies now have an option for Mosquito on the BNBSX Short Ears MK3S extruder.


Mosquito Compatibility Kit for BNB MK3S & MK3 Extruders

I really like this, but when I bought M3 brass inserts ages ago, I got ones that are only 4mm in diameter. I can easily insert them into the holes without even any heat, and pull them out just as easily. Would it be possible to get a version with slightly smaller brass insert holes?

Added a varient with 3.3 mm diameter holes for brass inserts. Openings are chamfered larger for easier centering, but the main diameter is reduced to 3.3 mm.

Thank you ever so much! I'll print it right away.

Do you know if this will work with the Moons MS17HD2P4100 on an MK3?

Yes, it will work with any of the full body size NEMA 17's that work with the MK3 WITHOUT the gearbox.
That includes the Moons' 1.8 degree MS17HD2P4100.

The limitation is with short body motors.

Increased depth of recess for motor pivot bolt to better clear extruder body for taller bolt heads.

Per vertigo235's build experience...

Brass insert version hole diameters reduced to 4.2 mm. Better a little too tight, than too loose for the inserts. I have retained hole bevel near 5 mm to help center brass during initial insertion.

Top, flat thickened 1.5 mm to keep motor mount slot farther from wall. This is OK as there is still adequate clearance upward on printer.

vertigo235 has created a jig for cutting and grinding shaft. https://www.thingiverse.com/thing:3555188

Bunny Science Gearbox Shaft Jig