Why is the speed not constant?

[MDT 0]

I normally use PrusaSlicer but due to a limitation in print bed size and some other issues I would like to give Cura a try.

 

Right of the bat it seems fine and there are a lot more settings. 

 

I do however have a major problem regarding how it moves. In prusaslicer normally the speed is constant without any jerky movements.

 

In cura everything is far from smooth. Every minor change of direction causes jerky movements. I have tried  different values in "enable acceleration control" and "enable jerk control". but nothing seems to change anything. I see the jerky movements both in cura when I press the small play button after I have sliced but also when I try on the robot.

 

Can anybody help me figure out what i'm doing wrong? 

 

*I print using an industrial robot and therefore need to convert the g-code I get from cura to "robot language" using a program called Robodk.

[nallath 1,118]

Do you have some images that show the difference? I'm not a 100% what behavior you mean.

[MDT 0]

1 hour ago, nallath said:

Do you have some images that show the difference? I'm not a 100% what behavior you mean.

Hi, I have made a small video where you can see that the speed of which the simulated extruder moves is very uneven. The link between the gcode and the robot is the program robodk which also makes a visual representation of how the robot will move. It shows the same uneven movements as in CURA. 

 

Does this make sense or do you need any other information?

 

Cura video

 

 

[nallath 1,118]

Ooh, you're talking about the simulation view.

We "faked" the animation that it shows there. It basicly moves to the next line every x time. So if yo have a lot of small movements the animation looks pretty smooth. If you have big long lines it will be very jittery.

[MDT 0]

22 hours ago, nallath said:

Ooh, you're talking about the simulation view.

We "faked" the animation that it shows there. It basicly moves to the next line every x time. So if yo have a lot of small movements the animation looks pretty smooth. If you have big long lines it will be very jittery.

Okay but it still show how the robot actually moves.. very uneven and jittery. 

[nallath 1,118]

1 hour ago, MDT said:

Okay but it still show how the robot actually moves.. very uneven and jittery. 

Those are completely unrelated. The animation in the simulation view does not take actual speed or acceleration into account.

[Mindspeed 0]

I'm asking the same on (Problem #2)

 

Yes, simulation and actual printing is differs, unfortunately I have no poof video of actual printing but in my case each round line prints separately in fact from speed point of view but those lines are actually connected!

I've played with enable/disable acceleration/jerk control excluding impact of computed speed in g-code commands but have no success with it.
How to make it print smoothly as a seamless line?

 

[GregValiant 1,141]

My understanding of speed in Cura generated Gcode is that a line like "G1 F4500 X2 Y 22 E222.12345" simply tells the printer where to go (including the E) and at what speed.  If acceleration and Jerk are enabled, then the firmware handles the further calculations of Accel, Decel, and applies the Jerk setting.  It times the steps to be sent to each motor so that they all arrive at the same time.  If the extrusion is short, then dependent on the Accel setting, the print head will not be able to reach the speed.  It will spend half the move accelerating and half decelerating.

[3D_Roboter 0]

wich robot you use?