Print speed vs. misaligned layers

[Hansen]

Hi all

I got my Rostock assembled a few days ago, and the prints are starting to look good. However, I've noticed some layer alignment issues. The layers are not exactly on top of each other, but they are "shifting" slightly around producing a rather rouch surface on the sides of the print. I lubricated the arms and checked the belt tension, which I think are all OK.

I am wondering if I'm actually printing too fast, as I think I see an improvement, when I slow down the prints. Of all the print speed settings I had the top one set to 110 mm/s. That is pretty high, right?

Also, what is your travel speed setting?

BR
Hansen

[lordbinky]

You identified the most common issues already.

You can take the belts and arms off and re-check the cheapskates. (sucks after you get everything tensioned just right)

You can check the hotend and make sure it doesn't have any play in it in reference to the effector.

You can lower the jerk setting and reduce the movements that have inertia issues.

Lowering travel speed could be helpful as well if that is the source of missed steps too.

It's trial and error until you can identify the issue though, and for the sake of your sanity just change one variable at a time.

[Hansen]

You identified the most common issues already.

You can take the belts and arms off and re-check the cheapskates. (sucks after you get everything tensioned just right)

You can check the hotend and make sure it doesn't have any play in it in reference to the effector.

You can lower the jerk setting and reduce the movements that have inertia issues.

Lowering travel speed could be helpful as well if that is the source of missed steps too.

It's trial and error until you can identify the issue though, and for the sake of your sanity just change one variable at a time.

Hi LordBinky

Now that you mention it... what is that "jerk setting"? I believe it is configurable on the printer itself only, right? But... what is it exactly?

BR
Hansen

[Polygonhell]

Mathematically Jerk is the second derivative of velocity. However the way it's used in printer firmwares, it is the allowed instantaneous change in velocity.
Each axis has mass that has to be accelerated to the requested speed, when a move starts, it starts at the jerk speed then accelerates at the acceleration until It hits the requested speed, at the end it decelerates to the jerk speed then stops dead.
If it's too high, the mass overpowers the steppers and you loose steps.

[lordbinky]

As further proof why 'jerk' is so hard to define exactly, it seems Smoothieware implemented it's 'jerk' setting based on this method. http://onehossshay.wordpress.com/2011/0 ... algorithm/

It's abuse of nomenclature like this that cause hair loss, broken electronics, and in extreme cases wishes to unmentionable beings for retribution against the offender.