Hello,

When the print head is moving on a straight line, it goes fast, and when it goes in to an arc, it goes slow.

I'm wondering whether the speed is limited by the microcontroller, or by the USB connection.
Is there any way to find out?

Kind regards,
Fallout

Arcs generally are actually lots of little line segments, The serial speed and the line protocol reprap uses are its bottle neck. (also timing issues with usb to serial)

If the reprap used a block transfer protocol vs line by line it would help a lot. (people where looking at this some time back... I don’t know what happened)

But since ramps is on the way out, replaced by 32bit controllers that use virtual serial ports at usb2 speeds, I doubt anyone will fix it.

Nb there is also the arc command in firmware, ie it send one arc command vs lots of lines. You could experiment with turning this on in your slicer.
Since there are no arcs in STL, the slicer attempts to guess which line segments it can replace with arcs.

The slow down is a result of your acceleration/jerk settings. The printhead doesn't have enough time on those short straights to get to full speed.
IMHO it's not related to USB or CPU bottleneck.
-Olaf

Quote
o_lampe
The slow down is a result of your acceleration/jerk settings. The printhead doesn't have enough time on those short straights to get to full speed.
IMHO it's not related to USB or CPU bottleneck.
-Olaf

IMO it could be either, depending on how smooth the curve is and its radius. If you have an SD card reader attached to your printer, try printing from that instead of USB, to take the USB data rate out of the equation.

If the printing is jerky on curves as well as slow, then it's almost certainly USB-related.

Edited 1 time(s). Last edit at 01/06/2016 04:49AM by dc42.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

We will not know, until we get more infos about the printer...
-Olaf