Common problems

Wobble – Non-smooth printing perimeters

We know that the problem of wobble is very annoying. Both for how it reduces the prints and because it is not always easy to find the cause.
There are many causes and I probably won’t be able to describe them all.

What we know for sure is that in most cases it comes from a mechanical malfunction of the Z axis, as it runs on the threaded rod.

wobble

Mechanical Issues

Now let’s deal with the most common causes that lead us to have the characteristic striped prints.
The wobble, or even oscillation has 2 main mechanical causes that cause it.

Wobble given by: Z-Axis Issues

When we enter the microcosm of Z-axis control we realize how many variables Wobble can cause, here we will list only the most probable.

wobble

  • Let’s make sure that the rod runs smoothly without having points of greater strength.
  • Let’s also make sure that the rod doesn’t twist, and let’s make sure that it’s perfectly parallel to the printer.
  • If the leadscrew is harnessed in 3 points, then it hold at the 2 ends with the brass screw that runs over it, we must verify that this is perfectly in line, otherwise we should free one end. (Opposite of step motor).
  • There may also be games on the Z axis, let’s make sure with manual touch and looking carefully at the leadscrew that there are none.
  • There may also be an imperfection in the connection between the brass guides and the threaded bars, on this you can print the appropriate “anti wobble”, found on thingiverse.
  • Let’s check that the pulley mounted on the Z axis is perfectly fixed.
  • There may also be an imperfection in the connection between the brass guides and the threaded bars, on this you can print the appropriate “anti wobble”, found on thingiverse.
  • We must then verify that the firmware reports the correct number of micro-steps of our motors. And that the motors (and their drivers) do not overheat too much during printing…
    Overheating of motors can lead to step losses, and step loss of the z-axis translates into more filament deposited in the same layer and therefore a possible excrescence.
  • We check the Vref (working voltage) of the motors, if too low it can cause the loss of steps, with the relative problems described above. LOOK GUIDE HERE

Wobble given by: Bed stability issues

The printing bed not perfectly fixed can give problems similar to wobble, and we can exchange them, especially if of small entity. When our bed has a minimum of play on the wheels/axles that move it, it can cause many problems. A movement of a tenth of a millimeter to the wheel can turn into 2/3 mm on one side of the plate. The constant movement of the plate back and forth can lead to constant lines on the model, normally close to each other. So first make sure you don’t have any games in the movement of the platter.

wobble

We can find some wobble even if the screws that anchor the platter to the printer are not very tight, in this case the inertia causes small movements of the platter that give rise to oscillation phenomena in the press, try to tighten the  platter!

The not perfect rigidity of the frame can result in wobble phenomena, especially with very fast acclerations and decelerations of the extruder.

Wobble given by: Extruder stability issues

Also extruder running on X axis if suffer any unwanted movement, maybe gave by ovalized wheel could end up giving some wobble, maybe on just 1 face this time.

Wobble given by: Slicer

It has been proven that wobble can also be given only by the slicer. From how the slicer elaborates and realizes the design, from the acceleration and deceleration of the nozzle and other, apparently insignificant, parameters. My first advice is: before going crazy, oiling, gluing and thoroughly examining your printer, which perhaps until then has always printed perfectly, try to change slicers, if the problem will occur then start to worry.

Wobble given by: Bad filament.

Always before starting to dismantle the printer you must bear in mind that a filament of poor quality, which does not meet the tight tolerances that the 3d printing requires can give this kind of problem, the 5% / 10% difference in the diameter of the wire result in a difference of even 0.05 mm, and differences on a wall that should be smooth you notice!
In more serious cases, the difference in diameter will also slow down the normal flow of the filament.

Wobble: Uncommon case

There is yet another rare, very rare case in which a wobble phenomenon could occur not due to mechanical problems, and therefore we mention it briefly.
If the printer for different problems (read PID regulation) can not keep the temperature constant but drops and raises 5-15 degrees, if we are already using a temperature close to the low / high limit of the filament this can really create waves.
These “waves” can modify the extrusion of the filament until they affect the good printing of the model walls. But I want to point out that this is a rare if not very rare possibility.

 

Wobble: how to decrese till you can solve

If you can’t get to the bottom of your wobble problem in any way, and maybe in the meantime you want to print anyway with the highest possible quality. The first and least intuitive operation to do if we find ourselves with this defect is the control of the amount of extruded filament. If our extruder lets out more filament than necessary this can accumulate on the object and form real lines on our object. However, it is not always easy to understand the nature of the error. And in any case it is always a good idea to check the amount of extruded filament, you can follow this simple guide and adjust the flow of the extruder at best.

To attenuate (not solve) the wobble problem, you can directly reduce the flow rate by 5-10 % using the slicing program. By doing this, the scarcity of material will cause the “waves” to decrease. Remember, however, that this is a pagliative for some printing and the problem will still have to be solved with maintenance operations.

[GUIDE] Adjust the amount of extruded filament


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