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UM2 Extruder pressure setting?

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While trying to locate the source of extruder skipping that happens often when printing light infill at speeds of 40mm/s or higher, I stuck an Allen wrench in the hole on top of the extruder to check the pressure.

The screw was basically loose in the hole, so I tightened it a turn or two until it took up slack and another turn beyond that. The white indicator is now just past the first mark of four on the extruder, which seemed to reduce the number of extruder skips slightly.

What should it be set at?

 

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According to the instruction manual of the Ultimaker 2, an increase in pressure is not recommended. The marker is regular at the upper stop. But you can try it without any Problems.

When the filament is used with the correct diameter of 2.85mm, then there is nothing to do at this point, the pressure should be optimal.

The step-motor is probably too weak to reliably transport the material at higher pressure. With a higher pressure increases the risk of digging, especially in very soft filament varieties.

Optimizations at other points usually bring more success. Some increase with a G-code entry, the engine power slightly. Then you could also slightly increase the pressure. Even filament must be easily led to the feeder without much braking factors.

Some use an alternative feeder design, but better would be a more optimal knurled wheel (MK8 drive gear) with adapted feeder housing. The Ultimaker 2 knurled wheel is not optimal.

I use an alternate step-Motor with more power and lower power requirements. It generally works better and I can set the lateral marker for the pressure between the first and second marking. Digging during the first layer, sometimes happens when the printing bed was not properly aligned. I will soon buy a better knurled wheel and construct a suitable feeder housing for it.

Markus

 

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The 'correct' position for the extruder indicator depends on when your printer was manufactured. Prior to March 1, 2014, the indicator should be in its highest position. After that, it should be in a central position.

Note that tightening the screw (moving it clockwise, as viewed from above) moves the indicator upwards.

When you talk about 'extruder skips' are you referring to the motor skipping backwards with an audible click (and a jump back of about an eighth of a turn of the motor shaft and knurled wheel), or are you simply referring to it grinding past the filament somehow, damaging it?

If its the former, then adjusting the idler tension in the extruder isn't likely to help much. Those skips occur when the motor simply can't push the filament hard enough to make it move. When that happens, the motor stalls, and jumps backwards. That is a good thing, insofar as the alternative is for the filament to stay put, and the extruder to keep turning. If that happens, then the motor will simply grind away the filament, to the point where it cannot grip it at all.

So, if you are getting the first kind of skip, then changing the level of grip on the filament won't make it better: the motor is already transferring all of it's grip into the filament, and it can't push hard enough. Reducing the tension in the extruder might allow the knurled wheel to grind past the filament, rather than gripping it, which will prevent the stalls (and the skips) but at the expense of damaged filament.

If what is happening is just that the filament is being ground away, without the motor skipping backwards, then adjusting the tension might help some, if it improves the grip on the filament, and lets more of the available torque be transferred into the filament.

Where the problem is the actual motor skipping, then the best solution is to eliminate sources of friction in the feed path (e.g., tightly curled filament, damaged Bowden tube, damaged teflon coupler, partially blocked nozzle) so that the filament can move, melt and extrude as easily as possible. If problems persist, then consider printing hotter, of at a lower volume per second (i.e., thinner layers, or slower linear head speed).

 

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"The 'correct' position for the extruder indicator depends on when your printer was manufactured. Prior to March 1, 2014, the indicator should be in its highest position. After that, it should be in a central position."

Illuminati, how do you know when your build date was? I just purchased my UM2 through Dynamism, and I'm not sure of the build date. It has the latest firmware. Thanks.

 

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The 'correct' position for the extruder indicator depends on when your printer was manufactured. Prior to March 1, 2014, the indicator should be in its highest position. After that, it should be in a central position.

 

OK, I have a Ultimaker of the early production. I am self-blame and might have to wait, wait for a possibly more reliable product.

Interrupts the flow of materials have almost always immediately visible impact on the object to be printed. Skip due to too little force, wanted or not wanted, or digging the knurled wheel in the filament, everything almost always leads to unusable results. I initially had both symptoms and many optimization experiments did not lead to a lasting improvement.

A guaranteed free nozzle, a correctly seated Bowden, a non-deformed ColdEnd, Original UM-Filament, slow printing with unusually high temperatures, no braking factors at the material feed, etc. Almost all efforts ultimately led to hardly noticeable improvements.

Only an alternative Step-Motor with a bit more power, it enables me to create nearly error-free printouts down to 0.05mm layer (now successfully tested) thickness. It is now generally less of a problem in the use of different materials.

Markus

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There's a several week backlog on orders, and they aren't staying in stock very long anywhere... so if you bought from Dynamism recently, then you have a 'new' spring in your extruder, and hence the 'correct' position is more towards the middle of the range.

 

Illuminati, how do you know when your build date was? I just purchased my UM2 through Dynamism, and I'm not sure of the build date. It has the latest firmware. Thanks.

 

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The 'correct' position for the extruder indicator depends on when your printer was manufactured. Prior to March 1, 2014, the indicator should be in its highest position. After that, it should be in a central position.

Note that tightening the screw (moving it clockwise, as viewed from above) moves the indicator upwards.

When you talk about 'extruder skips' are you referring to the motor skipping backwards with an audible click (and a jump back of about an eighth of a turn of the motor shaft and knurled wheel), or are you simply referring to it grinding past the filament somehow, damaging it?

If its the former, then adjusting the idler tension in the extruder isn't likely to help much. Those skips occur when the motor simply can't push the filament hard enough to make it move. When that happens, the motor stalls, and jumps backwards. That is a good thing, insofar as the alternative is for the filament to stay put, and the extruder to keep turning. If that happens, then the motor will simply grind away the filament, to the point where it cannot grip it at all.

So, if you are getting the first kind of skip, then changing the level of grip on the filament won't make it better: the motor is already transferring all of it's grip into the filament, and it can't push hard enough. Reducing the tension in the extruder might allow the knurled wheel to grind past the filament, rather than gripping it, which will prevent the stalls (and the skips) but at the expense of damaged filament.

If what is happening is just that the filament is being ground away, without the motor skipping backwards, then adjusting the tension might help some, if it improves the grip on the filament, and lets more of the available torque be transferred into the filament.

Where the problem is the actual motor skipping, then the best solution is to eliminate sources of friction in the feed path (e.g., tightly curled filament, damaged Bowden tube, damaged teflon coupler, partially blocked nozzle) so that the filament can move, melt and extrude as easily as possible. If problems persist, then consider printing hotter, of at a lower volume per second (i.e., thinner layers, or slower linear head speed).

 

Great Explanation. Saved me a lot of confusion! Thanks @illuminarti

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