G Code Print Speed Slower Then Requested Print Speed

[burgs04 1]

Dialing in speed settings for my printer and noticed that the speed shown in the g code file is only giving me 60% of the requested print speed.

 

So if the speed settings are set to 200 mm/s.  I slice and save the file.  Open the g code file and the speeds will only be 120mm/s.

 

Anyone have any ideas?

 

 

Also how do I change the Z axis speed?  It's at 3mm/s at the moment.

Edited August 20, 2021 by burgs04

[obewan 37]

16 hours ago, burgs04 said:

Also how do I change the Z axis speed?  It's at 3mm/s at the moment.

This is set by the Z hop speed

[GregValiant 1,251]

A couple of things here.  The print speed is governed in part by the minimum layer time.  Cura will make adjustments to try and hit the minimum time if your print speed causes a layer to finish too quickly.  It's a cooling thing.  You will run into that a lot when you use Spiralize (vase mode).

 

Consider:  Your print speed is 60mm/sec and your minimum layer time is 10 seconds.  You have a layer that indeed takes 10 seconds at 60mm/sec.  If you raise your print speed to 2000mm/sec but leave the minimum layer time at 10 seconds, that layer will still print at 60mm/sec.

 

As Obewan says, the "Z-Hop Speed" (found in the Cura Speed settings) pretty much governs the Z speed BUT the maximum that Cura will allow you to enter in Z-Hop Speed is "machine_max_feedrate_z" which may be set in your printer definition file.  You can change machine_max_feedrate_z in the "Printer Settings" (which needs to be loaded from the MarketPlace) which has a box for "Maximum Speed Z".  You can set Maximum Speed Z to whatever you want.

 

The real limit to Z speed is in your firmware in M203.  No matter what you enter in Cura, when it gets to the printer the numbers in M203 will be the upper limit for each axis.  You should enter the M203 numbers into Cura.  There is no way that Cura can query the printer to pull those values.

[burgs04 1]

@GregValiant I have minimum layer time set to 0 as this was an issue not long ago when printing in vase mode.  I had to disable print recovery and set minimum layer time to 0 to get vase mode to work correctly.  Minimum layer time is still set to 0.

 

I can't think of anything that would affect the entered print speed vs g-code print speed.

 

No matter what speed I set its always exactly reduced by 40% (or 60% of set speed).

 

If I enter 500 mm/s I get 300.

If I enter 100 I get 60.

If I enter 224 I get 134.4

 

The only time it deviates from the 60% is if the set speed is really low.  Sub 50 mm/s.

 

Is this a bug or is there something else that's reducing the speed?

 

 

Also.  Downloaded "Printer Settings" last night.  I will play around with that and report back.

Edited August 19, 2021 by burgs04

[GregValiant 1,251]

Use "File | Save Project" and post a 3mf here.

What printer?

What operating system?

What version of Cura?

 

I haven't heard of a "60% rule" before.  I'm not saying it isn't a bug but if it is one this is the first time I can recall it coming up.  Maybe one of the developers like @nallath or moderator @gr5 has seen something like it before now.

[burgs04 1]

Well...... I'm an idiot......

 

So the 60% I was seeing in the g-code was actually the requested speed (500 mm/s) x 60 (seconds) = 30000 mm/m.

[GregValiant 1,251]

Welcome to the club.