NSTT Extruder

by Paciente8159 Feb 6, 2017
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Hi, there is some possibility that you make a version with the 688 for the hotend with Jhead mount. Thk

can give the dimension of the spring. search for mk8 spring and doesn't have much luck, end up bought some spring that is too big, use for heatbed

I believe the spring is:
-Wire thickness: 1.2mm
-Outer diameter: 7.5mm
-Inner diameter: 5mm
-Height: 20mm
-9 laps

You can try and cut a bit of your spring with a plier.

Nice design !
But unfortunatly I'm not getting it worked to have a constant pressure on the filament -> seems to skip several times
Linked a picture below the good one is the conventional extruder the bad one this NSTT

Several things can cause this. Check this:
-Is the idler arm "jumping" or the extruder making a cracking sound?
-See if the MK8 hobbed gear screw is not lose or hitting the extruder body or the hobbed gear is not turning free on the M5 screw.
-Try to put more pressure in the arm spring and the idler bearing can turn freely.
-Check if the small gear is not skipping. The flat side should prevent this but if it is too lose on the motor axis this can happen.

If I have a jammed/entangled filament spool my NSTT can easily lift the spool of the ground up in the air and it will only fail after chewing the filament it self.

you are right the small gear is turning freely it just rubed off and deformed

Make sure to watch the assembly video before you assume the B.O.M is correct. Purchased some M5x40 cilinder head screws because the hexagon head you actually need was not specified.

High after all that the me I manage to test the extruder, but it seem that the small gear got a lot of play on the stepper, also my stepper I can't get it to far down in order to lock it where the shaft get round, could you make please make me a small gear with "D" all the way and a bit smaller in the end

Humm...probably the tolerances on your printer must be a little off.
The play on the shaft is not that critical. The away the extruder works you should not be affected by it.
I'll sen't you a PM with the customized gear, later this evening and you can try it out.

thanks will wait everything else come one just fine will wait to test the custom gear

Is there any reason for this gap in the idler? Wouldn't it make a stronger part if there was no gap? Please see the attached image:


On your page you have written...

To built this is necessary:
option a-625ZZ bearings (needs 1xM5 washer)
option b-688ZZ or F688ZZ bearings (no need for washers)


5 - Assemble the filament idler. If using body+idler option B insert the 625 bearing in the idler.

Is one of these a mistake? Is option b for the 625ZZ or the 688ZZ bearings?

Bad choice of letters by me. :-).
Regarding the extruder geared axis you have option A and B that are bearing dependent only (not printed version dependent).
The printed versions only change regarding the idler axis.
And the video is outdated.

Thanks for your response, although I'm still having a hard time understanding which parts to print.

Is the STL file named "NSTT_idler_B.stl" is for the 688ZZ bearing?

I'm really sorry but reading your instructions I've been unable to understand which parts to print.

Am I right in thinking that the newest version uses 688ZZ bearings instead of 625ZZ?

If this is correct, and I want to use 688ZZ bearings, which body and idler should I print. Looking at the files, from what I can see, to use 688ZZ bearings I need to print NSTT_body_A.stl and NSTT_idler_B.stl. Is this correct?

Ahhh, I just read this: "1x extra 625z if using idler+body B". So the Body B and Idler B are for 625z bearings, and the Body A and Idler A are for 688zz bearings?

Looking at the STL files though, I think you might have given Idler A and Idler B the wrong names.

I'm really confused! :)

Actually, looking at comments below, I can see that for Option B - the 688zz bearings, you need to print body A and Idler A. But for option A, the 625ZZ bearing, you need to print Body B and Idler B.

The updated video is out. Not a very good video but it should help. ;-)

I've updated the instructions.
You can use 688z ou 625z bearings in the geared shaft/axis regardless of the printed version.
The printed version is only different on the idler support shaft/axis. In one version the idler fits on a printed shaft, and on the other it requeries an extra 625z bearing to use the stepper motor shaft/axis as it's own (shaft/axis).

Hope it helps. I really got get some time to make the assembly video but many things to do...sorry :-P

Comments deleted.

Hi, I've watched your video twice and read the instructions several times but I'm finding it difficult to understand which parts to print and which bearings to buy. The thing that's got me most confused is this:

On your page you have written...

To built this is necessary:

option a-625ZZ bearings (needs 1xM5 washer)
option b-688ZZ or F688ZZ bearings (no need for washers)


5 - Assemble the filament idler. If using body+idler option B insert the 625 bearing in the idler.

Is one of these a mistake? Is option b for the 625ZZ or the 688ZZ bearings?

What would be the ideal material to print gear's? from what i see i actually need 3 625zz bearings 1 for the idler body , 1 that go next to big gear , and 1 for the final piece that close the extruder , also i might be mistaken you are writing somne m3 washers dont you mean m5 washer?

As far as material for the gears something resistant and low friction would be best (nylon I guess) but plain PLA is working fine for me. The M3 washers (actually only one is needed) is for the 623 idler bearing.

Thanks for your reply, so from material then you missing m5 washer, and propably 1 more bearing, unless the video is outdated/Instruction

How to choose A or B,Thanks

Print body A + idler A (no extra bearing needed) or body B + idler B (if using the 625 bearing and the stepper shaft has the idler shaft as well)
About the spacers you need to print both A+B according to the type of bearing your using (625 or 688).

Its an excelent work!! just what i was looking for! can you share the .skp files?

Not planing on releasing the .skp files for now. Sorry. :-/

Has anyone else had the problem with the body being very weak around the mk8 gear? specifically the area around the bearing that is on the opposite end of the big-gear. I'm very well satisfied with the extruder otherwise but i'm printing my 3rd body now as the previous two cracked in exactly the same spot :(

Another user has reported some concerns about the resistance of this area.
Mine was printed in plain PLA but it's rock solid, no problems whatsoever.
I'll try to review the extruder design to reinforce a couple of point during this week.

Nice to know, I printed mine in PLA as well, first crack i experienced was expected since i had underextrusion-problems with my previous extruder. Thanks for your work!

FYI the redesign mostly is done. I'm the print-test-adjust cycle phase. Probably will update the stl files this weekend. ;-)

Looking forward to trying it out :))

Awesome job keeping this extruder updated.

Can I still use the 623, 625 and 608 bearings with the new revision? Also, think you could give a bit more insight on how to assemble it?

The initial version used 623 and 625 bearings. The new revision added some spacers\adapters for the 688 bearings. The new spacers+bearings can be used in the old version of the body too. I'll do an update video as soon as possible.

Sorry, got things a bit mixed up in my comment. What I wanted to know is if I can still use the 625 bearings I have instead of the 688 ones, I'm having troubles finding those locally.

Sorry for the late reply.
Yes you can (assembly option c). The outer dimension is the same. The only difference is that you need to use washers instead of the spacers.
My advice is to print your own washers with better specs and smaller outer radius instead of using common washers.

Didn't see the reply until now, but I couldn't hold the hype and ventured to print and figure it myself short after my last question. It works beautifully, thank you for sharing such a well thought design.

Glad you liked it. Did you went for option c (625)? If so did you used regular washers? If so keep an eye in the filament idler. If it jumps or makes a crack sound every revolution the the washer might be out of alignment. The 688 or F688 are better overall solutions.

Yes, I'm using 625 bearings, in fact I completely ditched the washers and it's working flawlessly. Maybe our MK8 gears are slightly different in dimensions. The idler axis broke on first use but since the upper shield is holding it in place perfectly it's still doing its job just as if it didn't break, no play whatsoever. Exactly as you said, the small gear became loose little after assembly, no problem there, but then after about 180~200 printing hours the big gear's bolt slot got a bit loose and backslash became a problem so I fixed the bolt head to it with some super glue and a bit of silicone to fill the sides and added a tiny bit of lube to the gear's dents to reduce friction stress and help slow down the gears from wearing out, I still printed another pair to have spares for when the first ones reach retirement age.

It's been printing for about 150 hours straight after those tiny hotfixes and it's performing amazingly well, I don't see it needing maintenance anytime soon. I think it's worth mentioning that I like to push my printer, I'm running a standard of 120mm/s to 150mm/s with accelerations and jerk of 1400 and 18, in case you're worried about how much it holds under stress.

Thanks for the input. The rigidity of the axis idler was one of my concerns. The first version of the extruder had a couple of 625 bearings that used the stepper shaft has the idler axial support but I changed it to require less bearings and make it more light-weight. I'll review that part and i'll try to reinforce it, or eventually revert it back to use bearings (or include both options).
Has for the gears if you are using PLA has I am you can try reprint them slightly bigger and annealing them in the oven. Other wise the only solution is to use a different material.

What mount is your extruder setup sitting on in the first picture? I circled it in this picture so you can see what I am asking about:

I made a Lack table enclosure and my extruder is ont he table above my printer so I need a mount to hold it in place. Right now it is just zip-tied down.

Also, I just got the NSTT extruder working tonight and it is great so far. I was having binding issues with my old extruder setup and this one seems to be working great!

Thanks for your hard work and for sharing your designs.

That was a sort of a quick-n-dirty design I made to mount it on my P3Steel frame. This was made to temporary but it became permanent. This allows me to quickly snap it and remove it from the frame or fix it permanently with a M4 screw+washer+nut. I did not post this frame but if you need it I can make it available. What is your frame thickness?

Thank you for the other but I found one that works. Mine mounts on top of a Lack table so the design would be different because it does not attach to the frame. The extruder is working great! One thing I did notice was that the small gear was moving on the shaft of the motor due to the extra space my mount created. I simply put some washers behind the gear so it could not slide and it is perfect now.

Beware of the issue of the small gear. That must be cause be the tolerances on your printer.
I strongly advise not to put any washers on the stepper shaft or they will be grinding against your stepper. Even if it slides on your stepper shaft the gears are self locking so after matching the big gear should keep the small gear aligned. With the NSTT assembled configure the printer firmware and perform the Triffid Hunter's guide on how to fine calibrate your steps and reprint the gear to see if it helped.

How is this with flexible filament? Thanks!

To be honest I never tried it. I think it will do fine but only after experimenting I can be sure. If you try it and if any problems arise please contact me and post a video of the problem so I can address the issue.

Nice design!

  1. Do you have a filament guide suitable for 1.75mm filament? Can you provide one.
  2. How do you mount this as a direct drive extruder with hotend attached?


1.The printable filament guide is designed to accommodate the Teflon tube usually used for 1.75mm filament.
2.The difference between the bowden and the direct drive is the tube is much shorter. The tube should be the exact size from the top of the filament guide to the bottom of you hot end (in the case of the E3D is the start of the all metal tube section).
Do these steps:

  • Insert a teflon tube on your hot end.
  • Align the bottom of the filament guide part with the top of the hotend and cut the tube slightly above the point were the filament guide starts to get thinner (the idler/hobbed gear slots)
  • Insert the filament guide in the teflon tube and check if the bottom of the filament guide part touches the top of the hotend.
  • If it doesn't cut a bit of the tube and check. Repeat this process until they are in contact.
  • Insert the assemble part (filament guide + hotend with the tube inside/joining both) in the body and lock them in place.

I haven't tried this assembly in direct drive but it should work fine. This (unless you use a lighter stepper) will not make a lightweight axis so you might have to slower you printing speeds.

Thanks for your detail explanation. Appreciate very much :-).

Is this the same dimensions as a Titan extruder? I am trying to use it on a drive carriage that supports only titan extruder

I don't believe it is. It's not that far way but not the same size.
I don't have the Titan's exact dimensions but I've read somewhere on the www that the it is 60,5mmx46,7mmx25,4mm (HxWxD), excluding the big gear.
The NSTT is...well...not so tiny lol. It is 56,4mmx57,5mmx32,3mm also excluding the big gear.

Comments deleted.

I have been eyeballing the E3D Titan for some time but really wanted a more DIY solution. Personally, I think this is one of the coolest things I have seen on Thingiverse since I built the UM2 2020 Clone. Bravo.

Awesome! I have been thinking about a solution like this for my two machines. Thank you so much for sharing. What do you think of using a grooved idler bearing in combination with a knurled UM2 filament drive gear? I have these on hand and would like to use them but in the end I will probable just purchase everything from the BOM.

The UM2 fits no problem I believe just by suppressing one or two whashers. The problem might be the grooved filament idler.
What bearing do you have. I can take a look at that.

I just measured the bearing, it's 13mm x 4mm with a 4mm center hole.

So you have a 604UU bearing.
Several problems arise with this hardware that make it impossible to work without some heavy redesigning of the body, idler and guide.
The major issues are due with the offset in the filament alignment of about +2mm and specially the size of the screw that hold the idler bearing in place (would have to be an M4 screw) and the bearing itself, colliding with the rest.
If you had a 603VV or a 623UU bearing that would probably achievable (I think) by making some minor modifications to the filament guide peace.


Hey I found something that actually housed 2 of those tiny 623z bearings! It was an idler pulley I wasn't using. I'm also going to print an adapter to use my 688 bearings with the 5mm shaft. I may not have to order much after all.

Yes, after thinking about it this morning, I realized that the biggest issue is the required shaft size. Unfortunately the other bearings I have on hand are 688zz. I will just purchase the correct materials from the BOM. Thank you for taking a look.

Any chance of a STEP or IGES file of this?

I'm fully aware I can do that and have done, but it makes it very difficult to work with, where having a STEP or IGES from the source makes it a lot easier. I'm not sure what CAD package you're using, but most good ones should be able to export to STEP or IGES.

I used Sketchup to draw this. There's no direct export to CAD from there. I can try and use a plugin someone made in 2012 but I don't know how that will work out.

Ah that'd explain the link, re-reading my response, sorry for coming over a bit dickish. I'll sit down in FreeCAD and design it up.

As a note, you may also want to look at hole tolerances, and add 0.2-0.4mm to them so bolts just drop in, you are, after all, using nut traps, so there's no need for the holes to be tight. I also found the filament guide way too tight until I took some sandpaper and a drill to it to widen holes and make it fit, again, drop the external dimensions by about 0.2mm and increase the hole size by 0.2-0.4mm as it's only when I fettled it the bowden tube fitted correctly.

You extruder is looking fine. :-)
Yes you are right I could make the holes wider and it would be a lot more easier to insert the screws but prefer this way to prevents any loosening from the stepper vibration since i'm not using locking nuts. I'm just that paranoid ;-P
Has for the bowden tube after printing I used a 4mm drill and drilled it in reverse. It was fast and kept the teflon tube nice and tight inside.

Here's another advice. If the extruder makes a cracking sounds check if the idler is jumping. Is so the M5 washers are offset from center and is touching the idler every turn. I found that in mine once. The washer hole is a bit wide so getting it to be exactly centered required some trial and error. If this happens you can try and print some better M5 washer with a slightly smaller outside diameter.
Hope you enjoy the extruder. For me the extra torque for the bowden setup worked wonders.

Put it all together and I'm having issues with the filament slipping out of the tracks of the mk8. The idler doesn't stay in place either so the filament gets stuck under the bearing.

I remembered another dirty temporary fix if you haven't printed the correct body part.
On the top of the extruder where the filament is feed grind the plastic a little bit with a file tool so the filament to clear the path to the hobbed gear a filament and super-glue (or hot-glue) a M3 washer has ring guide to prevent the filament skipping.

Hey I switched back to my old one and reprinted the updated body.

Just wanted to let you know I've hook it all back together and man, this is one of the best extruder I've used!

You did an awesome design with this one. Will be looking forward to other stuff you cone up with

Did you print the main body with the 09-02-2017 update?
Is the 623z centered with the MK8 hobbed gear?

Edit: Actually it was my bad. I uploaded the wrong STL.
The correct body part is now available (rev170209).
You can try to make it work temporarily by adding more tension to the idler spring but to fix this permanently you will have to reprint the body.

Sorry about that.

The bom is missing the 623z that you use

Do you have any details on where to find/ how to make the hobbed bolt?

Ooh thanks, I thought it was a hobbed bolt. My bad but thanks for the fast reply. Really looking forward to printing this out!

I'll try to put out a video on how to assemble the extruder soon.
I like my NSTT alot. The extra torque allowed me to amp down my extrusion stepper (it's a little on the weak side) and it now runs alot cooler without any any stalling. The extra resolution is also very very good. The infills on my parts are alot more consistent.

Also note that the extrude/stepper mount base can easily be redesigned to fit a Nema 14 stepper motor just by changing the motor holes.
I'll probably add that option to the project in the near future.

I' currently in the the final testing fase of a Z-probe-"probe-less"-holder/mount for the E3D hotend that uses the tip of the E3D as the probe itself, to replace my custom differential optical Z-probe :-P. I'm trying to make my printer as maintenance-free as possible.
As soon as that is done I'll do the video.

That's awesome, I'll start following you to check out that probe. Anything that reduces fiddling time is definitely a big plus for me.

I'm ordering the parts I need today and as soon as it's together I'll post the pictures. I used .1 layer height and the parts turned out beautifully!

Only downside is that I was too lazy to switch out the colors so it's magenta

Assembly instruction video is out.
I've updated the info on the sizes of the screws needed too. I used M3x10mm and not M3x12mm screws.