lowest acceptable acceleration settings?
May 29, 2013 11:52AM
Hey all!,

I wanted to find out what is the lowest accepable acceleration settings that people have worked with? I am using 1000 right now but when printing very small sections of prints at 50mm I worry the accuracy is not there because of all the vibration going on.

Any thoughts and advice on this?

Thanks!
Re: lowest acceptable acceleration settings?
May 29, 2013 12:17PM
read here:

[en.wikipedia.org]

as for firmware,I would focus on jerk speeds, as this is the minimum start speed, and every time a direction change happens this will come into play. higher jerk speeds allow smoother operation around corners and circles.

as for acceleration in general, you want to ramp up speed as fast as it is safe to do so, but there are limits of how high acceleration can go especially with angles of greater than 45deg.

if you angle a mendel infill at 45deg, then the infill speed can be 1.4 times the max speed of 1 motor, because 2 motors are working at max speed and the distance diagonally is 1.4 that of a straight line.

anyway. read up on acceleration and determine the best question to ask. thanks hope this is a little bit helpful.
Re: lowest acceptable acceleration settings?
May 29, 2013 12:24PM
1000 means that you are saying it is ok for the extruder to go from 0 to 1000 mm/sec in one second. That is pretty quick. Maybe try something in the 100-300 range. I have been using 30 for perimeter and 60 for infills just to be sure, but expect to raise that with more testing.

Edited 1 time(s). Last edit at 05/29/2013 12:35PM by rsilvers.


[www.matter-replicator.com]
Re: lowest acceptable acceleration settings?
May 29, 2013 12:41PM
I think on marlin the stock setting is 10000, they should change it because i did not learn until recently messing with the firmware that it was so high, and thats why my prints were so poor at first. try setting it at 100 then go up and see what happens.
Re: lowest acceptable acceleration settings?
May 29, 2013 01:05PM
Maybe thats what it is... I set the jerk to 0 when I initially set the machine up and now i'm working at speeds 10x faster. Maybe I need to return it to default settings.
Re: lowest acceptable acceleration settings?
May 29, 2013 07:04PM
I use 500 acceleration in my printrbot. It improves the look significantly when I print at 70mm/s.
Re: lowest acceptable acceleration settings?
May 29, 2013 11:45PM
ThanhTran Wrote:
-------------------------------------------------------
> I use 500 acceleration in my printrbot. It
> improves the look significantly when I print at
> 70mm/s.

Did you over-ride the firmware limits? I am speed testing my Printrbot and the normal firmware is capped at 60. I over-rode them and tried a print at 120 and - no chance - the steppers skipped like crazy. I am working on a Bowden conversion today to see what happens when I lighten up the head.

Edited 1 time(s). Last edit at 05/30/2013 08:07AM by rsilvers.


[www.matter-replicator.com]
Re: lowest acceptable acceleration settings?
May 30, 2013 12:04AM
thats funny because the printrbot claims 150mm/s
Re: lowest acceptable acceleration settings?
May 30, 2013 12:39AM
Here are my Marlin firmware settings...
(My machine is in my sig)
Will slowing down help with print quality?

Feedrate (mm/sec)
X: 600
Y: 600
Z: 3
E: 200

Accel
X: 2,000
Y: 2,000
Z: 10,000
E: 10,000

Jerk
X/Y: 100
Z: 10,000
E: 10,000


--------------------------------------------------------
Custom all metal CoreXY
- Duet 2 Wifi w/ PanelDue 7i
- 330mm x 360mm x 500mm
- 750w Silicon heater

Custom Mendel90
(Backup printer - Old reliable!) - Sold
Re: lowest acceptable acceleration settings?
May 30, 2013 05:36AM
Quote

Accel
Z: 10,000

10'000 mm/s² on a threaded rod driven axis? Never ever. Think about this heavy rods you have to accelerate, too.

I guess it works only because you either move slow enough to allow instant acceleration or don't care about step losses. 200 mm/s² would be pretty good without step losses, IMHO.


Generation 7 Electronics Teacup Firmware RepRap DIY
     
Re: lowest acceptable acceleration settings?
May 30, 2013 07:33AM
Tbh i dont see much info on how acceleration settings work?

What happens if you set the slicer to move faster than the acceleration allows? Does it just cap the accellerations? Is it clever about that or will it just not follow the given track. Doesnt being clever in this case require knowing about turns sufficiently far into the future?

Also, slic3r doesnt have any per-direction settings? I feel my Y- axis wobbles a lot more than X, because the bed is just standing on three screws and those have a range of motion? Tbh i dont have the nuts underneath the screws right now, but i dont see how that'd stop the motion much. (See the image)

Btw my max accel(unchanged from defaults afaik) `M201 X2500 Y2500 Z50 E2500`.
Attachments:
open | download - damped_osc.jpg (135.2 KB)
Re: lowest acceptable acceleration settings?
May 30, 2013 08:13AM
Slicers don't have anything to do with acceleration. They just emit g-code that says where to go and at what speed. The firmware will cap the speed to its limits and decides how fast to accelerate to that speed. On short moves it may never reach the target speed.

In the firmware you can have different speeds and accelerations for each axis. If X and Y are different you will get features printed differently depending how they are oriented so I keep them the same.

I mount my beds rigidly and have Z axis nut traps open at the bottom so the nozzle can't hit the bed with force more than the weight of the X axis.

With soft limits enabled in the firmware hitting bed is not really an issue. The axes will flex a little before any damage is done.


[www.hydraraptor.blogspot.com]
Re: lowest acceptable acceleration settings?
May 30, 2013 11:47AM
Thanks for the info on how it works. I think the options in `slic3r --help |grep acceleration` basically overrides settings the firmware uses.(I was confused thinking it was slic3r determining the acceleration)

Oh, so on your machines the bed is more rigidly placed.. Hmm my machine has springs with screws going through it. Looking at the wiki page about the bed of the newer reprappro they changed it quite a bit, now it has a much shorter screws and trapped nuts.

The z-axis i have also has trapped nuts with springs and plenty of potential z-motion. So the springs on the bed arent really needed, only for bed leveling calibration..
Re: lowest acceptable acceleration settings?
May 30, 2013 07:04PM
I'm not sure what the original firmware you mention is. I download Marlin, modify it, and put it onto a Sanguino which controls my printRbot.
I use a Chinese 4 axis TB6560 stepper driver board with 16v power supply to drive all the motors. Currently I run at 70mm/s. I think it can run faster because I've manually push up the speed by 130%, and it didn't have any missing steps. The reason I use this set up is because I converted my CNC machine to a 3d printer before I built the printRBot. My stepper driver & Sanguino setup: [plus.google.com]

I also want to set up a Bowden extruder on my setup. I tried once with 3mm filament and it didn't work well. I'm building a 1.75mm extruder so hopefully it's better. I also need a lighter extruder because the extruder and motor combination makes the bed leveling not possible. When the extruder and motor are in the middle of the bed, the extruder head is about 0.1mm closer to the bed than when the extruder and motor are on either of the sides.

Thanks
-Thanh


rsilvers Wrote:
-------------------------------------------------------
> ThanhTran Wrote:
> --------------------------------------------------
> -----
> > I use 500 acceleration in my printrbot. It
> > improves the look significantly when I print at
> > 70mm/s.
>
> Did you over-ride the firmware limits? I am speed
> testing my Printrbot and the normal firmware is
> capped at 60. I over-rode them and tried a print
> at 120 and - no chance - the steppers skipped like
> crazy. I am working on a Bowden conversion today
> to see what happens when I lighten up the head.

Edited 1 time(s). Last edit at 05/30/2013 07:08PM by ThanhTran.
Re: lowest acceptable acceleration settings?
May 31, 2013 01:52AM
This is the Bowden setup I created:

[www.thingiverse.com]


[www.matter-replicator.com]
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