Stuttering printer

I have a strange issue with my printer. The printer head stutters when executing difficult moves.

Here is a movie
[dl.dropboxusercontent.com]

A difficult move is a fast curved motion or a lot of very fast short movements. It almost seems that the processor cannot keep up and therefore stops the printing head for a short period of time.

The printer is rather obscure printer (ProDesk3D). It currently runs on Marlin 1.1.0-RC6 - 24 April 2016 which I modified myself. Printing by USB or SD card doesn't have any influence on this issue. The microprocessor is a Atmega2560.

Is there anything I can do about this? It is messing up my prints

Edited 5 time(s). Last edit at 09/04/2016 09:39AM by JanJans.

My guess is you have a Graphical LCD Panel on that machine. Those burn up a lot of CPU cycles. If you do have a Graphical LCD Panel, you can go into unltralcd.h and change this line:
~~~~
#define LCD_UPDATE_INTERVAL 500
~~~~
Your LCD Panel will become a bit more sluggish and not respond as quickly to your commands. But the good news is it will be able to spend those extra CPU cycles keeping the printer moving at a nice speed.
You can also go into Configuration_adv.h and change:
~~~~
#define BLOCK_BUFFER_SIZE 32
~~~~
This will make the planner buffer twice as deep. If there are spare CPU cycles available, they can be used to plan future work for the printer to do.

Thanks for your response Roxy.

Your right. I have a Graphical LCD Panel on the machine.

I modified the firmware by editing the two values. This was a big improvement. However, the stuttering occasionally still occurred.
I had to set the LCD_UPDATE_INTERVAL to 1500. That seemed to be high enough. The printer is now working perfectly. I didn't try 1000.
This large value does decreases the usefulness of the screen. However, print quality comes first.

Thank you so much for your help.

Edited 4 time(s). Last edit at 09/05/2016 10:36AM by JanJans.