3D Printing Forum

Hi,

One of my ongoing projects, it's to make a feeder with dual mk7 gears, a bit like bondtech but much simpler and ofc cheaper.

The idea it's to make a IRobertI feeder but on the area that holds the bearing, replace it with a MK7 and add a 3-5mm needle bearing. I just got x4 bearings from a shop so I'll start to do this quite soon.

The advantages I see area
- Dual grip with a 'circle' inside area.
- I want to avoid something flat, like the normal bearing, flattening my filaments.
- I want to be fully closed, so the filament doesn't have anywhere to go.

Ofc I'll also add an area to 'oil' to help with flexible filaments, and ofc I'll use 1.75mm filament. But when finished I'll leave the step files so others can change it. It's a bi hard since IRobertI never uploaded his step files, but after trying to do the pancake I think I can do this, at least pull it to a 'basic' point where others can help.

So I'll try to use x2 needle 3id-5od mm bearings inside a mk7, that will move freely, not dual geared like bondtech. This way the basic stuff to use it would just cost 6€ each mk7 (they are cheaper on china, but I prefer my trusted reprapworld ones) and 4-5€ each bearing.

OFC I think the best solution it's to just buy the bondtech 50-60€ dual gear motor-less kit, but I want to make a cheaper more easy to mod feeder.

I think that the main advantage of the bondtech is the dual geared drive gears, what would the advantage of your MK7 with super small needle bearings instead of just a grooved bearing be?

Also, you can get cheap MK7's with 8mm hole made for planetary geared steppers, wich would allow you to use a more robust bearing.

I haven't found any grooved bearing that was trully 'round'. They are on V shape, and I want the filament to keep it's circular shape. The think it's that with a flat, or V flat bearing, the filament get's squash, but with a double mk7 the grip it's on both sides, one mirrors the movement of the filament on a bearing, and the other pushes. If done right, both would just push enough for the filament to stay grip without squashing it. At least that's my theory.

Ofc I still think bondtech solution with the double gear it's better.

Oh also I can push strongly enough, that the filament get's squashed inside the bowden, so more force would only increase the chances of breaking it, or worse, a highpreassure leak on any feeder part. I don't think that more force it's the sollution. There's a limit for print/speed and when you go over it you get other problems.

There is most definatly bearings with a semicircular groove rather than a V-groove, attached is for example the one in the UM2+ feeder.

Indeed, but that's for 3mm, if you use that for 1.75mm you get it flatten. I did some test with the um2+ feeder and I really don't like it much. But you have a point there, I wonder if scaled down bearings like that are rounded, the ones I got ain't good enough...

Neotko: http://www.ebay.com/itm/141938644240

These have 1mm radius = 2mm diameter, should be just fine for 1.75mm filament.

The UM2+ feeder might not be good for 1.75mm filament, but for 2.85mm filament, it really is good, i have had almost no problems at all with it since i first started testing one of the pre-production UM2+ units.

Well that really it's a much easier mod than doing a full feeder

Thanks men!

It only took a 2min eBay search to find them

Interesting. I have this idea for a feeder that does not use hobbed bolts but a series of driven grooved wheels on one side and grooved bearings on the other side, any idea if it would work?

I belive it would work for a certain range of filaments, flexible filaments would probably be too soft and just slip, and super stiff filaments might just snap.

Meduza wrote:I belive it would work for a certain range of filaments, flexible filaments would probably be too soft and just slip, and super stiff filaments might just snap.

Good point. I really want this for the likes of PLA, ABS and PETG, in order to allow multiple short retractions over a short length. With current designs, that would shred the plastic, but with this idea it should not really be an issue. With flexible filaments you should be able to get away with that kind of thing anyway, and the really hard stuff is probably a nightmare with regards to retraction anyway.

I should really give this a go.

Is fitting a second extruder motor to the UM2 easy to do? Has anyone written it up?

Well finally got some time to sit down and design the feeder. The important stuff it's done, now it's just a matter of extrude/bolean/adjust. Dual mk7 with a max distance for the second mk7 so it doesn't push too much. Also it's going to be quite bigger but since weight there isn't a problem Also I want this to be much more enclosed and have a proper internal filament guide, specially now that I found out how much slippery it's the black PLA-tec, it's amazing, the touch on the hand it's like rubber but it's very slippery, weird material and a bit hard to print without hairspray, but really cool.



BTW danilius a good option for something that keep pushing the filament to avoid flexibles going bananas I think (never tried it) the 0x7d feeder https://0x7d.com/2014/07/improved-ultim ... -extruder/ ofc the downside it's that has parts that will need replacement, but I wonder how much time could last printing without issues...

So far so good. Great grip and seems that will work. IRobertI let me put my greasy hands on his design and I'm adapting it for the cheapest 45€ 1.75 double drives of bondtech. This should fit perfectly on a Meduza gear to have a semi/bondtech at cheaper price.

Tomorrow I'll do some print test to start to narrow the posible errors on my re-design.

Looks good, I modified Roberts guide to give me minimal clearances for using with the flexible filaments, I also added a hole for a pipe cleaner to add oil to the filament helping to reduce the friction in the Bowden tube.
I like your hobbed spur gears are the for 1.75 or 2.85 filament? And is that to fit the existing ultimaker motor?