Repetier speed max out at 50mm/s

Hi All!

I set out to build a CoreXY printer 2 years ago, 1 happy move to another city, new job, school for kids, rust because of storage when searching for an apartment etc. etc. etc. I finally got it together!

After some initial hurdles, it works way over my expectations, so I'm entering the improvement/refinement phase.
So that's why I'm here :-)

I had the printer set up on a cheap IKEA table, and it made a ringing racket from hell, the table makes some sort of resonance box like a guitar. Rubber feet mounted helped a bit, but microstepping made it go away totally! So that's great but the thing is that I now can't make the printer to move faster than, around 50mm/s.

The setup is ATMega2560, RAMPS, CoreXY "classic" reinforced 20mm extruded aluminium frame and NEMA17 motors (some oversized but that's another story) Bowden setup with E3D hotend (The chinesium in the cheap one broke).
Software is Marlin & Repetier, with eeprom activated (took me some time to get that the overrides were in repetier after that switch).

The, for me, curious thing is that if I fake the microsteppingin in Repetier (basically tells it to move the motor further to move a mm), the printing head maxes out.
But if I only set the maximum speed, there seems to be a very distinkt 'lock' at 50mm/s (give or take some).
I can set a lower value and that works.
I have tried only with the graphical move commands in the Repetier soft.
I also fiddled with the acceleration (and it works as expected) and the infamous jerk (if it's the derivate of acceleration why is it m/s??) but it doesn't look like they are to blame for this.

For what I have understood, as I have eeprom enabled, any changes in Marlin won't change speed settings (?)
Any ideas of what I might have missed here?
Is Repetier blocking speed when in manual control?

Cheers

Ludvig

Jerk is the derivative of acceleration in maths but not in the reprap firmware. In reprap firmware it is an instantaneous speed change that can be tolerated by the system. In other words the highest step rate that can be started in a jump from zero and the stepper motor looses no steps. I'm trying to understand the exact application myself but I understand it is used to reduce the need to accelerate and decelerate on vectors as the nozzle is moved around a path.

Edit: For completeness compare the above to jerk in the maths world is a constant change in acceleration. The standard example is a rocket burning fuel at a constant rate, generating a constant thrust would have an increasing acceleration as the mass of the rocket reduced.

Edit 2: Jerk used to be called minimum speed, which kind of helps explain how jerk is applied if you think that speeds between zero and the jerk speed are missed in the acceleration. It is a little misleading though as some moves are made with step rates between zero and the jerk speed.

Edited 2 time(s). Last edit at 09/11/2017 09:54AM by WesBrooks.

Thanks, and yes, it seems as it's the maximum speed change Between two timesteps, so it's still wrong IMO (could be say "delta mm/s") but well, everyone is doing it this way so :-)

I sifted through the Marlin firmware yesterday (is it only I who have all the files blocked in 'open' mode in the IDE and locked in place?), I found some variable about manual moving speed but changing it didn't do anything.

I also made some more tests, I guess it doesn't really matter but it's more like 40mm/s than 50mm/s...

Maybe microsteppings makes it so it can't go any faster with my setup?

I haven't used Marlin firmware for several years, but I recall that there used to be a bug that limited the speed you could use when the firmware was built for a CoreXY machine. So if you are using a very old version of Marlin, updating it might help.

Marlin and 8-bit hardware together have quite a low maximum step rate, but unless your steps/mm is very high because you are using high microstepping, I wouldn't expect you to hit that limit on a CoreXY machine at those speeds. What is your X and Y steps/mm ?

---

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].

Okay, I got my head around it and here is what I figured: (BTW, recent Marlin firmware)

Motors: 200 steps/revolution with 16 microsteps (so 3200 virtual steps)
Pulley GT2 20 teeths
Belt: 2mm / step(between 2 teeths)

So, 1 revolution equals 40mm
And my step/mm would be 3200/40 = 80 microsteps/mm

And at 50mm/s (which seems to be my maximum) that would be (1.25 rev/sec * 3200 step/rev or 50 mm/s * 80 step/mm) 4000 steps/sec

I have read that marlin on an AtMega2560 can do like 10.000 steps/s, but is that for each motor (do they add up) or all motors?
Are all recent AtMega2560 running at top speed (maybe mine is on 8Mhz or something)?

Maybe I should start over with another firmware?

Anything that sticks out?

Perhaps it's stating the obvious, but what maximum X and Y speeds do you have configured in Marlin? You may be able to check it by sending M503 and looking at the returned M203 parameters.

---

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].

@work but will check @home

I have eeprom enabled so I configure that in Repetier and anything higher than ~40-50mm/s just doesn't change anything.

For what I have understood, when eeprom is enabled, Only Repetier (thus eeprom) configuration values count.
I have changed the values in Marlin to no avail / no changes at all.

Quote
Ludvig

The, for me, curious thing is that if I fake the microsteppingin in Repetier (basically tells it to move the motor further to move a mm), the printing head maxes out.
But if I only set the maximum speed, there seems to be a very distinkt 'lock' at 50mm/s (give or take some).
I can set a lower value and that works.
I have tried only with the graphical move commands in the Repetier soft.

Ludvig

Have you tried using G1 commands with higher speeds to move the head around ? If a G1 command can move the head faster than 50 mm/s then the firmware settings are fine and it's some setting in Repetier that's limiting the speed. You should first run a M503 command like dc42 suggested to confirm that your max feedrate settings are above 50 mm/s.

I'm using 8 bit Marlin on my CoreXY with 200 step motors, 16 tooth pulleys and 32 microsteps and can move at 100+ mm/s just fine.

@dc42, I have eeprom enabled and the M503 spit out these, for me, seemingly normal values, right?

20:02:45.893 : echo: Steps per unit:
20:02:45.898 : echo: M92 X80.00 Y80.00 Z400.00 E87.04
20:02:45.902 : echo:Maximum feedrates (mm/s):
20:02:45.906 : echo: M203 X120.00 Y120.00 Z120.00 E320.00
20:02:45.910 : echo:Maximum Acceleration (mm/s2):
20:02:45.910 : echo: M201 X400 Y400 Z2000 E1000
20:02:45.918 : echo:Acceleration: S=acceleration, T=retract acceleration
20:02:45.918 : echo: M204 S100.00 T100.00
20:02:45.935 : echo:Advanced variables: S=Min feedrate (mm/s), T=Min travel feedrate (mm/s), B=minimum segment time (ms), X=maximum XY jerk (mm/s), Z=maximum Z jerk (mm/s), E=maximum E jerk (mm/s)
20:02:45.939 : echo: M205 S0.00 T0.00 B20000 X60.00 Z4.80 E80.00

@xyze tried the G1 command and it moves as slow as repetier manual command

Ehrm... my mistake here, I saw travel speed 3000 and thought motors maxed out at say 50, but funnily Repetier has mm/s in the eeprom settings but in travel speed, it's mm/minute...

Learned one or two things on the road but sorry for the inconvenience.

Cheers and thanks!