New dual drive wheel extruder!
During the last couple of months I have developed a new type of extruder that takes away many of the problems related to today’s extruders. Common problems are under extrusion due to slipping on the filament, filament grinding etc. To overcome the slipping problem it is common to increase the tension of the spring loaded bearing to create more friction between the filament and the drive wheel, but this also leads to deformation of the filament which gives problems with increased friction between the filament and the Bowden tube or the filament path in the nozzle.
Extensive engineering work has been done to find a solution to this problem and I am now happy to say that there is a solution, the Bondtech dual drive extruder. The design are based upon having two set of drive wheels that grip the filament on both sides, the secondary drive wheel is driven by the first by gears placed on the drive wheel. By using a 5:1 planetary gearbox there is plenty of pushing force available and at the same time very high accuracy. Retract speeds up to 60 mm/s are also possible but depends on the type of motor, voltage and stepper controller.
The new product has undergone extensive testing during the last months and the results are very positive. @Eclsnowman has been very helpful in the development discussing different ideas and designs, and he has also been doing some extensive testing of the extruder, a big thanks to you Eric!
In a couple of weeks I will be able to provide kits of the metal parts and also professional 3D printed SLS parts. The design is also possible for you to 3D print yourself.
The project is an Open Source project under the CreativeCommons license and you will find the information on Youmagine
How does this deal with varying diameters of filament? DM filament, for example is 1.75mm with little variation. Other vendors filament is often 1.6mm. I’ve seen bulges in some filament as large as 2mm but still worked just fine on the spring driven extruders because they were able to account for the variation.
Does this one just simply jam, or is there some sort of mechanic which allows you to adjust it?
Hi @ThantiK , there are two setscrews on the side that adjust the distance between the drive wheels, it allows for adjustment of about 0.4 mm that our tests have proven to be ok with varying filament diameters. @Thomas_T_Sorensen the price is not finalized yet since I am waiting for qutations from suppliers.
The need for this can’t be unstated. The time I’ve wasted playing with the extruder tension & hobbed bolt on our Prusa i3s is insane. We’ll be purchasing this kit the minute it comes available. Thank you, sincerely!
I can attest to the quality and performance of this extruder. I have been chomping at the bit to be able to talk about it, but Martin being the professional engineer that he is was always coming up with better and better improvements to be tested. But now that Printerbot has released a similar type of idea the cat is out the bag.
Soon I will upload one of the extruder in use on my HercuLien printer at high speeds. But today is my birthday, so I will be relaxing with the family.
The advantages I see with Martin’s design are:
1.) The housing is already very close to being injection molding ready.
2.) The adjustment ability of the secondary drive allows for fine tuning the pinch settings applied to the filament.
3.) The Planetary Nema 17 has so much force I think you could extruder the darn filament through the hot end cold. I was able to lift 40lbs of water in a jug at high extrusion speed and there was no signs of slippage or loss of speed.
3.) There are windows in the side to allow for viewing both hobs and cleaning the hobs (but I have never had to yet).
4.) The method that the front cover is retained allows for easy servicing (again I have never had to maintain anything yet).
5.) And the bowden tube retention method allows the tube to pass right up to the hobs which makes it ideal for filament that has a tenancy to buckle like nylons and ninja flex.
@ThantiK I have tried some pretty crappy filament with this extruder. Stuff that varies from 1.6 up to 1.9 on the same spool. I think due to the dual drive and the hobb profile Martin has chosen that since it engages on both sides the filament just bits in harder, or less hard with the variation. But I just set a medium tension a month ago and did not have to touch it since across multiple spools.
I printed at 200mm/s with a $15 spool of abs and the print quality looked exceptional. All of my prints recently have been this this extruder. If you look back at some of my posts I think people would agree the extrusion consistency at these high speeds is impressive.
My goal is absolute simplicity and dead simple design. I’ll leave the power, speed, adjustability and all that complexity and added cost to other designs with different needs.
We are hoping the complete instructions to our dual gear head extruder reads like this:
I have seen something similar by @Shauki a few weeks ago. but the more people who have the same idea means there will be iteration on it and improvement. i am excited to see who can make it work the best. incremental improvements between designs are what will keep OSHW growing.
@Brook_Drumm I think both Printerbot and Martin have great designs. I feel that great minds think alike. Filament stripping and jams are one of the last major hurdles for our hobby. I print many very large objects for work. There is nothing more frustrating than running a 28hr print that fails in the final stretch, or has a stutter mid print that it recovers from… But now there is poor layer bonding in the middle of the printed object.
I think Brook (Printerbot) and Martin would be well served to team up. This advancement will be great for the community at large.
I moved away from a metal gearboxed motor because they add a lot of weight, more than 50% heavier than the bare motor would have been. I’ve got a dual extruder that only weighs a little more than a single extruder with a metal gear box motor.
Hi @Jeff_DeMaagd If I understand you correctly this 5 mm is for having enough room for the gear cutting hub without interfering with the hobbed teeths. Maybe there could be a better way of machining it.
@Jeff_DeMaagd the current iteration I am testing used off the shelf hardened gears. Martin is working on making the hobb section and the gears in one piece. This will allow the footprint to be condensed.
Also nothing is keeping this style of design from using the standard 40mm nema 17 in place of the planetary. Just move some mounting holes and change the main hobb/gear to 5mm ID. But for bowden the planetary really is amazing. After using them, I would never dream of going back.
I’ll get this out asap to be sure all benefit… Gears first with printed clamshell design. Then injection molded at a great price… Did I mention I own an injection molding machine? Did I mention we are making our own molds? Finally, I can move fast and save the customer money with injection molding!
