UM2 - Controller speed 100% / Cura

[jamboy 0]

Hello together,

Just wondering what 100% speed in the um2 controller means. Is it 100% speed, like set in cura? For example set 60 in cura = 100% controller?

Also are the settings which i save in cura, are saved in the file on the sd card? For example, layer high / speed and other stuff?

Thanks for feedback.

[illuminarti 18]

Yes, the speed override in the controller is to adjust whatever speed is hard-coded into the gcode file. You don't always get the full speed that you requested anyway - for instance even if you tell Cura that you want to print at 60mm/s, it may slow down some or all of the print to meet a minimum layer time setting, so that the print has time to cool between layers. But whatever speed the gcode asks for, that speed gets adjusted by the percentage amount in the controller. So if you leave it at 100%, the speed is unchanged. If you increase the setting to 200%, it will print twice as fast.

The gcode file on the SD card is a set of specific instructions - telling the head exactly how to move, how fast, and how much to extrude as it does so, in order to build up the object that was sliced. It's just a text file. Each line describes one move of the head - where to move to, how fast, and how much plastic to extrude. All of the settings that you make in cura are therefore implicit in that set of instructions that gets written to the card. If you change the layer height, or many of the other parameters, then a totally different set of instructions will be needed to get the head to trace out the same shape, but using a different number of layers, each of which has to trace out a slightly different cross-sectional shape than for the original layer heights.

In addition however, Cura includes a brief description of the most important settings - such as speed and layer height - in comments at the start of the gcode file, and a compressed copy of the full settings that were used at the end of the file. This allows you to reload the settings from a previously sliced gcode file if you want to reuse or tweak those settings.

 

[gr5 2,172]

Illuminarti fully answered properly but just to clarify 2 things:

 

Also are the settings which i save in cura, are saved in the file on the sd card?

 

Yes - they are in the gcode file at the very end. Cura has a feature to load them back in under "file" "load profile from gcode".

 

If you increase the setting to 200%, it will print twice as fast.

 

Thus overriding your minimum layer time settings. For example if you said minimum layer time of 3 seconds and it is printing something tiny and you print at 200% it will probably print each layer in 1.5 seconds and you will get bad result. But for most things this is fine.

Also it's not necessarily twice as fast - the REQUESTED move speed is twice as fast but it takes a few milliseconds to get up to speed due to the current acceleration settings. Cura doesn't mess with acceleration settings - that's stored in Marlin and can be changed with the ulticontroller. And saved.

I usually set Cura to 100mm/sec and then I can set the % on the ulticontroller and now the % matches the speed. For example if 50% feed rate then it prints at 50mm/sec. That way the math is simple and I can decide on the print speed *after* I slice and put the card in.

 

[jamboy 0]

Hey Guys,

Now it's clear. Thanks for your feedback.

Good tip with the 100mm/sec. I will try that on my next print.

[fons 0]

Following on the tip of setting the speed in Cura always to 100mm/s :

If you set the speed at for example 60mm/s in Cura , does it show this number in the Ulticontroller interface (print speed shown when you go into the TUNE submenu from Ulticontroller)? I constantly get the same FR feed ratio as the speed indicates while printing even when I set the speed for example at 60mm/s in Cura .So the initial print speed which I set in Cura never appears in the Ulticontroller interface . Is this normal ? It isn't handy .Thanks for your reply ,

Aum.

 

[gr5 2,172]

Is this normal ? It isn't handy .

 

I agree. That's why I almost always set the speed in Cura to 100mm/sec.

The number on the UM2 (and UM original) shows the "feed rate %" which is a multiplier. Normally it is 100% at the start of every print.

 

[illuminarti 18]

Actually, to clarify my original post a bit... When generating 'UltiGcode' for the UM2, Cura doesn't include the basic settings in the preamble, nor does it write a compressed form of the settings out to the end of the gcode file, allowing them to be read back in.

Daid, please can we get both those things added back for UM2 gcode? It's hugely useful when troubleshooting folks' printing problems to be able to see all the settings that they used.

 

[swordriff 119]

Oh dear...

Is it so that when I set the speed in Cura, ie 60, then

when UM2 is set at 90, the actual speed will be 54?

No wonder it was tough to find the right settings!

..

 

[illuminarti 18]

The speed in the UM2 is in percent. So yes, if you set the speed in the slicer to 60, a 90% setting would give you a speed of 54mm/s.

Bear in mind also, that this is only a target speed. If you set a minimum layer time, Cura will reduce the speed that is coded into the gcode so as to ensure that each layer takes at least that long.

Furthermore, the head accelerates and decelerates as it moves, slowing to a maximum 'jerk speed' at sharp corners. So the average speed of each line segment is usually less than the requested speed. And, if you are printing detailed parts with lots of short segments and sharp corners, the printer may never get up to full speed at all before it has to slow down again for the next corner.

 

Oh dear...

Is it so that when I set the speed in Cura, ie 60, then

when UM2 is set at 90, the actual speed will be 54?

No wonder it was tough to find the right settings!

..