Makelangelo with RAMPS board wirks fine but moves jerky only on fine detail

[Pablo]

Dear all,
I am running Makelangelo 7.242 with Mega and Ramps 1.4 board and latest firmware.
Works fine – but has problems with small details. Here is a video:

For the very small circles in my example video here the pen is being jerked around and sometimes so badly that even steps are lost. Examples at 0:12 and 0:31. The big circles are fine.
Machine width is 1650 mm. I can lower acceleration and draw speed to glacial but the small circles are still being jerked as can be seen in the video. This is extreme when trying to plot stipple images. The pen never comes back home then. The really weird thing is: Big circles OK!

Any ideas for a fix? Is my RAMPS board broken? Help would be much appreciated!

Greetings from Cologne,

Pablo

[Dan]

Probably your minimum segment time and your acceleration need to be balanced.

Minimum segment time is adjusted with M205 B*** where *** is 25000 by default. larger means slowing earlier. it’s like… braking earlier in stop-and-go traffic. The commands to the robot are the cars in front. if they have not started, the robot will come to an abrupt – brief – stop while waiting for the commands. also try a lower acceleration. this is a subject we are discussing right now in the Discord channel, trying to optimize for speed and quality.

[Pablo]

Thanks! I found this line in configure.h, line 245:
#define MIN_SEGMENT_TIME_US (25000)
I increased to 27000 and further to 50000 and I see no change.
I can decrease the accelleration and draw speed in the Java app all I want but the last bit of the small circles is somehow done at full speed. Here is another video:

Am I tinkering at the right place in configure.h? Out of ideas for now – thinking about maybe honking at the traffic jam?

[Author]

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