Welcome to the SeeMeCNC Community

Hey,

I have a Rostock V2 that I built with taller extrusions, and on the innital movement after homing if the extruder is not moving to X0, Y0 on on the build plate, the initial movement is jerky.
I made a video of how it behaves, the first part is when moving to X0, Y0, where it moves smoothly, and the second part is moving to X0, Y90.
[youtube]http://www.youtube.com/watch?v=tC6koEjmEOg[/youtube]

I used a higher speed because its easier to see the jerky movement, but normally I don't run it that fast. It does this with Repetier Host and Mattercontrol, so I don't think its anything with the host software.

Has anyone else encountered this?

Yeah they do that, it's a firmware issue.

I suspect there is lock contention in the buffer that's used to expand the long move to delta segments can't hold the entire move broken down. It's really only an issue on very long moves, and seems to be exacerbated by the speed of the move. Basically there is a very small buffer in the firmware used for motion planning and as that buffer drains it slows down the move, because it has to plan conservatively. On a delta individual moves become collections of small moves, and I suspect the buffer starves because of insufficient CPU cycles on the thread outside the interrupt that sends the pulses to the controllers.

It should not be something you see while printing or effects printing.

I haven't had any issues with it behaving like this in printing, so I don't consider it a big deal.

Firmware is what I had thought too, but I hadn't seen any posts about this before so I was wondering if it was normal.

Thanks for the reply!