What are normal Marlin feedrate and acceleration numbers?

I am having trouble keeping my Z motors in sync. After trying to eliminate all friction and binding by upgrading to lm8uu's, flexible couplings, well lubed z leadscrew, etc, i don't think friction or binding is the issue anymore...

I am starting to wonder if my max z feedrate, acceleration or jerk figures are too high or if there is some other setting that needs adjusting. Here is what i currently have things set to....

#define DEFAULT_AXIS_STEPS_PER_UNIT {62.9921, 62.9921, 2267.716, 593.13}

#define DEFAULT_MAX_FEEDRATE {500, 500, 5, 45} // (mm/sec)
#define DEFAULT_MAX_ACCELERATION {900,900,100,10000}

#define DEFAULT_ACCELERATION 3000 // X, Y, Z and E max acceleration in mm/s^2 for printing moves
#define DEFAULT_RETRACT_ACCELERATION 3000 // X, Y, Z and E max acceleration in mm/s^2 for r retracts

#define DEFAULT_MINIMUMFEEDRATE 0.0 // minimum feedrate
#define DEFAULT_MINTRAVELFEEDRATE 0.0

#define DEFAULT_MINSEGMENTTIME 20000 // Obsolete delete this
#define DEFAULT_XYJERK 20.0 // (mm/sec)
#define DEFAULT_ZJERK 0.4 // (mm/sec)

Do those values look resonable? Should i decrease my z feedrate and acceleration numbers? Z jerk? If so what to?

I think my stepper motors might be slightly underpowered, so i probably need numbers that are on the conservative side.

Also, what is the difference between DEFAULT_MAX_ACCELERATION, DEFAULT_ACCELERATION, and DEFAULT_RETRACT_ACCELERATION?

Thanks!

The only thing I see wrong is.

> #define DEFAULT_MAX_FEEDRATE {500, 500,
> 5, 45} // (mm/sec)
> #define DEFAULT_MAX_ACCELERATION
> {9000,9000,100,10000}

Also I have a few machine that I have the Z jerk even higher and it does not cause any issues (default is 0.4 and I run at 4.0)

I would think your issue is either needing the Z to enabled all the time.
#define DISABLE_Z false

or you have the drivers turned up to high and they go into protection mode for a split second on every z move which looks like skipped steps. If the drivers are too warm to touch you most likely need to turn them down a little to avoid over heating.

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Are you saying i should increase my X & Y acceleration to 9000?

I had decreased the X & Y acceleration it because i was missing steps in both directions... I posted the wrong numbers before though... i actually have X & Y acceleration decreased even further to 450 because even at 900 i was still missing steps. So it's actually like this...
#define DEFAULT_MAX_ACCELERATION {900,900,100,10000}

My motors are always enabled (i actually don't even have that pin connected in my homemade pololu electronics since that pin is pulled low to enable the drivers directly on the carrier board), so that's not the issue since they are always enabled no matter what.

My current is turned up fairly high, but i have really large heatsinks on the drivers and they don't get very warm to the touch, so i don't think my drivers are temporarily shutting down either.

No I am not recommending to turn up the acceleration just pointing out that they were not the actual defaults. The defaults are really 9000.

I don't have any other ideas sorry.

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a) put the Z jerk to 0. This won't help much but it will help.

b) reduce the XY jerk to 7-10 and you might be able to have a larger than 900mm/s acceleration. Also, your default acceleration value should be lower or equal to the max acceleration values for XY. (ie: 900)

I have no idea why there is only one value for default acceleration and 4 values for max acceleration....

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***Edit: I guess i should specify that i have a Prusa iteration 2 running lm8uu's, and pololu electronics since different RepRap machines would probably need different values

Sublime Wrote:
-------------------------------------------------------
> No I am not recommending to turn up the
> acceleration just pointing out that they were not
> the actual defaults. The defaults are really
> 9000.

I think im not necessarily looking for the "defaults" since those just come in a stock configuration.h file, but I am more interested in the actual working values that people are using on their machines.

Wasn't the Marlin firmware originally made for the Ultimaker printer which has a much lighter hot end since it uses a Bowden cable. So i thought i read somewhere that the "default" values in the firmware are for an Ultimaker which would have a lot less mass to move around in the X and Y directions thus could use much higher acceleration figures like the default ones.

Are you using 9000 on your RepRap? If not what are you using?

Andrew Diehl Wrote:
-------------------------------------------------------
> a) put the Z jerk to 0. This won't help much but
> it will help.
>
> b) reduce the XY jerk to 7-10 and you might be
> able to have a larger than 900mm/s acceleration.
> Also, your default acceleration value should be
> lower or equal to the max acceleration values for
> XY. (ie: 900)
>
> I have no idea why there is only one value for
> default acceleration and 4 values for max
> acceleration....

Thanks Andrew, I will give those things a try this weekend when i get some time to run some tests with different values

Yeah the default acceleration having one value and max acceleration having four was what was confusing me also.

Edited 2 time(s). Last edit at 05/03/2012 03:37AM by daufhammer.

I run all my machines with the acceleration at 9000. 1 Prusa with bronze bushings and a couple of Tantillus' which have bowden cables.

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FFF Settings Calculator	Gcode post processors	Geometric Object Deposition Tool Blog
Tantillus.org	Mini Printable Lathe	How NOT to install a Pololu driver

I found that I had to keep the speeds down really low with the acceleration at the default 9000, otherwise my motors would skip steps frequently. I currently have the X&Y acceleration set to 500, which allows me to set the top speed much higher in Slic3r without any skipped steps.

Thanks for the feedback... I just tried decreasing my max z feedrate to 2 mm/s along with making the DEFAULT_ACCELERATION and DEFAULT_RETRACT_ACCELERATION match my max accleration settions of 450 in the X and Y directions. I also decreased the ZJERK to 0 and decreased XYJERK to 10.... You can see all my current settings below...

#define DEFAULT_MAX_FEEDRATE {500, 500, 2, 45} // (mm/sec)
#define DEFAULT_MAX_ACCELERATION {450,450,100,10000}

#define DEFAULT_ACCELERATION 450 // X, Y, Z and E max acceleration in mm/s^2 for printing moves
#define DEFAULT_RETRACT_ACCELERATION 450 // X, Y, Z and E max acceleration in mm/s^2 for r retracts

#define DEFAULT_MINIMUMFEEDRATE 0.0 // minimum feedrate
#define DEFAULT_MINTRAVELFEEDRATE 0.0

#define DEFAULT_MINSEGMENTTIME 20000 // Obsolete delete this
#define DEFAULT_XYJERK 10.0 // (mm/sec)
#define DEFAULT_ZJERK 0 // (mm/sec)

After making these changes i am no longer missing any Z steps which was my problem (or X and Y for that matter).... Im thinking the reason i have to make my setting lower than say your's Sublime is that I bought non standard motors from a local surplus motor supplier, there isn't a data sheet available for them, but i think they probably have a little less than ideal torque (although they are pretty large and feel very strong).