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3:1 Geared Bowden Extruder

by FerociousDiablo, published

3:1 Geared Bowden Extruder by FerociousDiablo Sep 22, 2017

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If you have made this thing and find it is useful and or has improved your prints, please consider leaving a tip. Thanks!

Also please consider using my Amazon (<-click here!) link when you buy things from Amazon.co.uk. It costs me a lot in filament to design and perfect these things. All support is very much appreciated!

Here is a design I have been working on for a 3:1 geared bowden extruder capable of pushing flexible filament such as TPU.

I printed everything with 25% tetrahedral infill in cura. 4 top/bottom/wall shells. 0.2mm layer height. Some of the fittings are a bit tight and some parts may need some cleaning after printing. Use supports everywhere 10% lines in cura as they are quite easy to remove and help with some parts.

1: Attach the gearbox part to the bowden motor mount (I use: https://www.thingiverse.com/thing:2369063) attached to your frame using either 4xM3x10MM bolts or other suitable bolts.
2: Fit bearings into main body and top cover, they should push all the way in with a little persuasion.
3: Fit M5 bolt into spur gear and push all the way in. Slide one of the washers on after the spur gear.
4: Push M5 bolt with spur gear attached into bearing in main body from rear.
5: Fit Mk7 extruder gear to M5 bolt and line up with filament holes in main body, it can help to mark where this lines up with the holes and file a flat spot for the grub screw but this is not essential.
6: Assemble arm, put M3 nut into hole in handle and thread 20-25mm M3 bolt in to it from the other side. Put other M3 nut into hex hole on adjuster cog and bolt onto the 20-25mm bolt. Push larger bearing onto the stub at the other end of the arm and then push the stub on arm retainer into the top of the bearing.
7: Attach arm bushing to main body with M3x10mm Bolt from rear. You may need to clean this part up a bit so it fits nicely into the hole on the arm. Slide assembled arm onto the bushing once attached and insert spring between the adjuster and hole on the main body.
8: Fit top cover to main body using 4xM3x10mm bolts. Put M5 washer on M5 bolt on top of bearing in top cover then bolt M5 nylock nut onto M5 bolt. Do not overtighten. The bolt should be able to turn freely with no pressure on the arm.
9: Fit assembled extruder to gearbox using 4xM3x10mm bolts, paying attention to the orientation of the push on gear for the stepper motor. It will only run one way. Attach the pneumatic couplings to main body. You may need to use a spanner as they are a tight fit at first.
10: Calibrate extruder steps per mm. Mine is 316.66 for PLA and 327.59 for TPU.

Leave any comments and suggestions in comments section please :)

Required parts:
13x M3x10mm Cap head bolts - 3mm Socket Cap Bolts (20 Pack) M3 x 10mm A2 Grade Stainless Steel Socket Cap Allen Key Head Bolt / Screws Free Uk Delivery.
1x M3x20 to 25mm Cap head bolt - 3mm Socket Cap Nut & Bolt (4 Pack) 4 Stainless Steel M3 x 20mm Allen Key Socket Head Bolts (Fully Threaded), 4 Nyloc Nuts & 8 Flat Washers. Free Uk Delivery.
2x M3 nuts - M3 Full Nut (50 Pack) 3mm A2 Stainless Steel Hex Hexagon Nuts Free UK Delivery
1x M5x45mm bolt - Pack of 10 DIN 933 A2 STAINLESS STEEL HEX BOLTS – M5 x 45
1x M5 nylock nut - Bolt Base 5mm A2 Stainless Steel Nylon Insert Nyloc Nylock Lock Nuts M5 X 0.8mm Pitch - 25
2x M5 washers
1x Stock Anet A8 extruder spring. (about 8.5mm diameter and 20mm long) - Amazingdeal 10pcs 3D Printer Extruder Strong Nickelplated Spring for Ultimaker Makerbot
1x Mk7 extruder gear. 13mm tall, 12mm OD, 10.6mm ID, 5mm bore - 2x 3D Printer MK7 Drive Gear Extruder Pulley (5mm shaft/bore) - For 1.75mm filament Reprap Makerbot
2x PC4-M6 pneumatic couplings - BIQU PC4-M10 Male Straight Pneumatic PEFE Tube Push E3D-V6 Fitting Connector for Bowden Extruder 3D Printer (Pack of 10pcs)
1x 608 bearing (I used 608-ZZ) - 8 Pack 608 2RS Bearings Skateboard Bearings Longboard Bearings for Toy, Double Shielded (Black)
2x 625 bearings (I used 625-2RS) - 10Pcs 625ZZ Metal Shields Shielded Deep Groove Ball Bearings 5x16x5mm

https://www.youtube.com/watch?v=BB9uH5Oiohk

Check out this 3D printer support group for help with your settings or anything else printing related: https://www.facebook.com/groups/1843740479205162/

Disclaimer: The links are amazon affiliate links which means I get a small percentage if you use them. It does not increase the price you pay

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I'm having a hard time trying to get mine to extrude properly. I re calibrated my steps in the firmware and reversed the rotation of the stepper and no matter what value per step I try it only gives me 15mm when I ask for 50mm. Any idea what I might be doing wrong here? This has been a fun project. I even thought about trying to print the 5 mm bolt but it didn't work out.

It depends what firmware you are running, but you need to save to the eeprom and reload. Turning it off and on again may help too.

Funny you should mention printing the bolt as that was my original intention but couldn't make one strong enough at the time. I wanted to print a flat part in it and a non threaded section and even have the files for it somewhere

will my stock anet extruder gear do the job ,
its 11mm o/d 11mm high and 5mm bore,
cheers

Some have managed to make that work, so it may

Got to say I love this mod. It works great so far. Like most I have to have the tensioner almost as tight as it will go but it is working. Curious how long the small gears will hold up but I printed extras just in case.
Thanks for a great Thing!

Thankyou for the support!

I have been using the same small gear since I released this and it is still going strong :)

Hi I'm about to print this, but wondered what was the difference between the 2 main body parts?

Only the size of the holes for the pneumatic couplings. One is m5 and the original is m6

I was using the original Anet filament gear until my MK7 gears arrived. Swapped over to the MK7 gear, and now no matter how tight I make the spring, it won't consistently grip the filament. Got any ideas what could be going wrong?

Was your printed in PLA or ABS ?

PLA all the way :)

Hi!
That seem as a very good extruder design but I made it with abs and I have a heavy under extrusion problem. to explain:
My mk7 gear is not here so I decided to use my original Anet A2 gear (I think it is an MK8). Thing is that the extruder does not have enough grip to the filament even when I pretensioned the spring almost to full setting. I have calibrated the extruder steps and it was as I though 3x more than the original from 95 to 285. Mind you I calibrate the steps without having the filament being pushed to the hot end so not have to compensate for filament slippage. That way I don't understand why you have different calibration settings for different material, that's doesn't seem right except if the design does have filament slippage because of the grip. 100mm of extruding just gives me exactly 100mm filament push but without having pushing it to the hot end, and by having so much under extrusion compare to my original extruder I do think there is quite a lot of slippage

The MK8 gear is not wide enough to use in this design which is why I specify the dimension of the extruder gear in the details.

I have also found that the spring has to be quite tight, although not fully tight. I am going to work on a different arm for it when I have time

Comments deleted.

thanks for the reply! I will wait for the mk7 gear to arrive and I will post the results

Printed it, but I think my settings were a bit off on my printer cause the holes for the screws are too big to actually thread the screws in, and have them catch into the material. I’ll try printing again with different settings, so no fault there

I did manage to print for a good 10 mins with it though, seems like a great unit while it worked, but had to switch back so I can print a bunch of spares of the small 12 tooth gears out of the strongest material I had on hand. Carbon fibre ABS. Seems with the other materials I used, including nylon, that the gear can’t handle the 730 steps/100mm that I needed to set up for. after while, the D becomes round, and won’t do anything but freewheel on the shaft.....granted 730 for esteps is practically insane, but stock I actually had at 238.39, which is nuts as well. I fear if I predrill for a grub screw, it would damage the profile, and in turn damage the other gear as well, due to the herringbone shape. I will attempt to remix the gear with a collar, which will accomodate for extra face strength as well as provide a space for a grub screw.........might take me a little while to figure that out, but I think there would be enough space there if I reuse the grub screws from the stock extruder drive gear

I am in the process of building these for my Geeetech M201 that I've converted to a dual extruder. Even with my driver voltages cranked all the way up the motors will still skip steps at times. I am hoping that the 3:1 ratio will solve this however as Horizon604 has pointed out, the small gear is of concern. I will have to look through some of my left over sample packs from when I had a monthly subscription for exotic filaments and hope I have a super strong material I can print them with.

I like your idea of beefing up the collar part too which I may go ahead and do too.
I had to mirror a whole set since Im using it on both hotends. If anyone would like those just reply and I'll post them up.

I went ahead and extended the collar. Here it is. I have not tried it yet as I am still printing the initial parts.

I tried the extended collar and found that even though I make it solid the collar broke off when trying to fit the gear on the stepper drive. I'm going to go with the original design and see how it goes.

The holes would be too big if you used less than 4 walls I think. :)

Good idea with the collar / grub though for the stepper gear. Although I think when you fix the walls it will be a bit more grippy on the axle

I'm trying right now with a .3 nozzle and 7 perimeter

that did the trick on both parts.....everyone this is the solution if you have problems with the holes and gears :)

Fantastic!! Thanks for updating the post

Hi. I have printed everything in PLA but can't seem to get it to work properly. I have to manually put force onto the filament or the handle so that the gear can grap and extrude with enough force. I just changed over to a MK7 gear since I was using the original A8 Gear before, but this also didn't help.
Right now I have one of my hex wrenches jammed in between the casing and the adjustment nut to enlargen the force with which the filament gets pushed into the gear.
Did you do any other adjustments to your gear or have an idea what could cause my problem?
Otherwise this looks like a really awesome design, thanks for sharing and hopefully I'll get it to work nicely soon.

Oh...I'm using it with a Prometheus HotEnd V2.

It sounds like the extruder gear you have is the smaller type? The one I use is 12mm diameter on the outside.

I did nothing to the parts once printed apart from clean up the supports / brim. Sorry thats not much help :(

Thanks for the quick reply :). My gear is actually 12mm in diameter too. It barely fit and I really had to tighten the little screw so that the gear wouldn't get stuck on one side.
I'll see what else I can do about this.
What kind of Hotend are you using?

Is the extruder gear actually turning or is the motor not turning (skipping steps) when it is not feeding correctly. You may have to up your voltage a tad.

No worries, it is very strange :(

I am using a E3D V6 clone on my A8

Looks fantastic! I'm always a bit cautious when buying hardware, do these look like the right gears? https://www.amazon.com/Witbot-Stainless-Steel-Extruder-Printer/dp/B01KJONSRS

Yes they are the same dimensions as the one I am using :)

Hi. Excellent! Can I use flexible filament with this? Thank you!

Yes, I have used with TPU and had no issues. It worked really well. Remember to calibrate extruder steps :)

hello, why a mk7 gear and not a mk8?

MK7 seems to grip the filament better in this application.

Love it... Thanks. About to print it tonight in abs...

did you have any problems printing this in abs ? did you have to rescale (increase the scale to 101%) ?

Great! Please post a 'make' when completed and let me know if you run into any problems. There shouldn't be any but I have only printed it in PLA so far.

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