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Filament grinding driving me crazy


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Posted · Filament grinding driving me crazy

Hello everybody,

I've been printing for 2 years with my UMO perfectly. I now think I can say I know my machine. Unclogged it several time, upgraded with heated bed, dual extrusion, so I know the basic troubbleshooting.

For 3 months now I can't print anything correctly at 0.2mm and need to print under 40mm/s at 0.1 mm layer height (while I was used to print at 80mm/s) and don't manage to understand where does it come from. I have filament grinding always wasting my prints and never know if a one hour print will be succesfull (I was used to happily print 40hours print with no problems).

If I print big flat objects, the first layer infill is like wavy (the underextrusion come and goes like waves ). If I help by just slightly pushing the filament I have no problem anymore. I checked the spring of the feeder.

My guess is that a stack of slight problems (aging ultimaker) makes a big one.

I checked:


  • the bowden tube and teflon coupler
  • hotend is new
  • Peek isolator is new


Here are the things I tried:

As the problems started after printing a lot of things with Colorfabb XT, I thought maybe some XT remains in the hotend when switching to pla and partialy clogged it. So I changed the hotend (twice even). I read here that some people had ther teflon part damaged by the 250°C needed for XT. So I checked it and there is no friction.

I checked the toothed filament pusher (sorry, can' remember the name) and realized it was much less sharp than the second extruder one (that doen't work so often) so inverted them, no change.

The small injected weel that press the filament seems quite used, could it be that ? (it happened to me in the past that this wheel slide on the bearing and stay blocked)

The injected plastic lever that press the wheel on the filament seems to not press anymore. Is it a known issue for old UMO ? If I press it by hand or with a small clamp I have less grinding but it will still happen after less than 30 mn.

I tried several different filament (most of mines are colorfabb and as I bought a pack are one year old, always kept in a box, but no air tight storage). Even a knew one and always some grinding (I'd say less grinding with XT).

By hand the filament comes out from the hotend (so if my temperature sensor is wrong, it is not completly dead),

One other guess is that my bowden tube has a double curvature (from a travel in my car) that increase the friction. I'm waiting for a new one.

I cant' see if I should change everything once for all (complete hot end, bowden...) or if there is a way to solve the problem.

Any help appreciated.

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    Posted · Filament grinding driving me crazy

    Do you have the same problem when using the second extruder (eg; use the second extruder as your 'main' nozzle?)

    This could help with narrowing down where the problem is.

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    Posted · Filament grinding driving me crazy
    So I changed the hotend (twice even)

    Including the nozzle? That was my first guess.

    After reading everything I'm thinking "feeder". The feeder should be able to push about 10 pounds (what country are you in - please update your location settings in your profile).

    when sliding filament through bowden by hand with everything cold and off - how much of that 10 pounds budget does it use? Probably not much.

    Test your feeder. Take a 2 foot length of filament and put it in the feeder, attach it to a bucket sitting on a scale on the floor. Use bungee cords and a vice-grip to connect the filament to the bucket. Start turning the feeder by hand. How much does the weight on the scale change? You should be able to do around 5kg or 10 pounds. if you can only do 2 pounds then we know the problem is the feeder.

    Here is a photo explaining how to do it - same procedure for UMO or UM2 - same approximate strength in the feeder for UMO or UM2:



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    Posted · Filament grinding driving me crazy

    Thanks for your answers. They helped me to finaly find wher was the problem that now is settled. Was not easy though:

    I decided to test the lifting power of the feeder: The faulty feeder couldn't lift 3kg while the second one was lifting 4kg easily and started grinding at 5kg.


    So I started to look at the differences between the two, and while adjusting the "pressure" screw I realized that on the faulty one I could screw it much deeper than the other one. So I dismantled the injected plastic parts for both of them and saw that the middle part was cut into two by the screw that


    I must have screw too much one day. Now way to guess it as the part is fixed between the two other ones, the lack of stifness is not obvious either.

    I'm still testing but it seems I found back my reliable wonderfull Ultimaker that I was missing so much. And it forced me to check everything, replace some parts taht where getting old, so I guess I can trust it now for some time.



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