Man, these parts are pretty! I forgot how nice pla prints.
Great job! What is the model you are using? Iâd like to see how my bowden setup compares. I should be able to use higher acceleration number for the same result, since I donât have the weight of the motor to deal with. Iâll have to check to see what I have accel and jerk set to now, I remember tweaking them to match some random web page suggestion⌠
Here is a direct comparison. 50, 75, 100mm/s.
I want to keep testing but Marlin 2.0 isnât playing nice right now. I have been at it for a while.
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75calibration_cube.gcode (84.6 KB)
100calibration_cube.gcode (84.6 KB)
calibration_cube.gcode (84.5 KB)
Got my frame put together. I would up using MDF. Ryan said it would work - and itâs much cheaper. I put the bottom on and it seems pretty ridged. Ryan you are a great engineer. You could teach Ikea a thing or to. It was a joy to assemble . Got a ways to go but so far so good.
Hey Ryan, I wanted to add your âV1â sticker at the too but itâs a tad big. Would any of your other stickers fit? Also That would be a cool name for your printer I think âThe V1â has a nice ring to it.
Iâm having issues typing on my phone today . I was trying to say I wanted to add the sticker to the too of the printer.
TOP! Dang phone.
I need a little help, On my Y and X axis I had assumed the 608 bearing in the BOM ware for the belts oposite the motor end, -They Donât seem to fit there. Help please, I must be missing something. Thanks
W.r.t. jerk. I donât think I agree with what it does.
What I understand is that it is the speed where acceleration âshort cutsâ and doesnât limit speeds.
So if jerk is 10mm/s, max speed is 100mm/s and Accel is 1000mm/s/s. Going in a straight line, from stop through the line to stop, the speed would go from zero, immediately to 10mm/s (the jerk), then follow the acceleration to 100mm/s. Then at a computer point, it will decelerate at 1000mm/s/s, until it reaches 10mm/s second. At the exact end of the line, and it will stop immediately.
If you take a 90degree turn, I think it treats it just like that, completely stopping in X and completely starting in Y. With the numbers above, it will slow down to 10mm/s and take the turn at that speed. That is a big impact on the printer though, because it has to apply enough force to stop the carriage from 10mm/s in X to zero, instantly, and go from nothing to 10mm/s in Y, in the same instant.
I think max speed is meant to limit things like too many steps/second or an extruder that canât possibly hear fast enough. Acceleration is more the critical piece, because itâs going to be very sensitive to mass and rigidity.
If they didnât use jerk, or the jerk was 0.0, the math for acceleration would mean that the printer would go very slow any time it stopped, started or took a turn. The reason there is jerk is because any impact under 1mm/s is bacisally no big deal, right? So why bother slowing down from 1 to 0 in this smooth, acceleration? Itâs an optimization, really.
I would try to tune like this:
- Set the jerk to zero or very close to zero.
- Set the max speed to huge.
- Make the model small enough that you arenât getting under extrusion problems. You wonât reach max speed.
- Adjust the acceleration until you get an acceptably low amount of ringing. Keep this Accel. You might want try this twice, once for perfect and once for ok.
- adjust the jerk up, a little at a time, until you notice some problems in a corner. Back it down a little.
- Adjust the model to be bigger, and reduce the max speed until you can print a big side without extruder, belt, stepper problems. You can probably determine a good print speed and travel speed separately in this step.
This way, the acceleration should keep things smooth in even the worst situations. The jerk will be optimizing as much as possible, without affecting your prints, and you wonât ever exceed your top speed for extrusions and steps.
They are the pulleys in the original MP3DP. In the new MP3DP V2 there are actual idler pulleys. Which parts did you print? If you did the original parts then the pulley should fit between the two bosses embossed around the hole.
I printed the new version . I had a couple idler pulleys and they worked. What threw me off was the new bill of materials doesnât show the pulleys.its cool though Iâm about ready to fire the printer up. Thanks.
I have it in the notes about the idlers, mine died real fast lube them up. Bill hasnât had an issue so I am on the hunt for better pulleys.
Heffe, I have been looking to the motion equations in marlin and canât find them. I am still tweaking settings but with the equations I really feel like I am poking around in the dark, the notes in the firmware are far to vague. I printed some parts yesterday and they had ringing even with the slower accelerations. Maybe even worse.
Try setting the jerk really small. Like 1mm/s.
I have tried 2 and 4, I will go lower but the dam LCD doesnât work right on the mini for some reason with Marlin 2 all the other boards are fineâŚHours trying to fix it.
Progress, I think. Here is a better test showing the issues I saw in the real print.
75mm/s accel 1500mm/s/s test part is smooth to 5° STL conversion.
Jerk x=4 Y=2 still
Showing horrible bulges at 5 degree increments heavier on the left which was ramping into x axis parallel so super shallow Y moves.
[attachment file=51502]
Jerk both 2⌠both sides bad, needs to go higher! You can see the emboss ghosting differences.
[attachment file=51503]
Jerk both 4 @ 75mm/s and 50mm/s
[attachment file=51504]
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Let me guess at whatâs going on. I think those are being printed as line segments, so with lower jerk, it is be trying to reduce the speed at each point. The higher jerk is making it take the curve at a smoother speed. I really wish there was a way to display what speed it would actually take thereâŚ
I think youâve made a better test print, in just worried it wonât translate well to another radius part. It looks like this artifact isnât ringing at all though, right? Itâs just over and then under extruding. The filament flow isnât dynamic enough to match the dynamics of the x/y motion.
I wonder what it would do with an arc.
Very interesting though.
You can hear it in the big round corners too low of a jerk and it sounds obviously wrong. Still havenât found the equations. Not sure this was a big deal or notâŚ
Finally found the equations, seems obvious nowâŚMarlin/src/module/planner, duh. 4 planner files and some in the 2 stepper files Jerk is mostly in planner.cpp and the trapezoid is in planner.h (starts at entry speed).
How I am reading it. It calculates the speed trapezoid (basic straight line) starting at whatever jerk is set to as the minimum speed (entry speed), this sets both ends of the ramp up and ramp down. Smooth velocity is checked to see if the change in velocity is higher then the jerk to trigger accel or not (curves).