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Rostock problems on the outer regions.

Posted by mrg78 
Rostock problems on the outer regions.
August 05, 2014 06:01PM
Hi !

I have built a RepRap Rostock Delta 3D Printer, with ramps 1.4 and modified marlin fw.
Small prints, 100-120mm wide is no problem, almost perfect.
But when i print bigger things, thats when the problem starts.
If i keep the temperature at about 185-190 degrees celsius its ok in the middle, but along the sides, it's almost like the hot end is getting colder, the filament won't go through the nozzle and the extruder-motor just keeps jumping back cause it can't hold the force...
But when it goes back to the middle its fine again.
i tried increasing the temperature and when i get up to about 230 degrees, it works.
But then it like its flooded with filament and there is just too much filament coming out, also the whole thing collapses in the middle, probably cause the high temperature.

It looks like its moving slower on the outer parts, but maby its suppose to do that cause of the delta...

Have i missed a setting for this or is there something wrong in the fw, i think there is a newer version but i thought i ask here first if someone else got the same problem.

With regards
Re: Rostock problems on the outer regions.
August 05, 2014 06:52PM
The filament not going through the nozzle and the knock of the extruder is a jam. I call it the knock of death-- I hate that noise. The fact that it comes and goes when you are moving from the middle of the print bed to the outer reaches is strange, mainly because the heater and thermistor are attached at both points and they should be reading the same within plus or mins 4 degrees of your target temp at all points of the print bed. Have you checked that the thermistor is firmly attached into the heat block and that no wiring is coming loose?

When you are printing and when it moves toward the perimeters of the bed, have you looked at the temperature in repetier host and verified that it is getting colder, and falling far outside of the target temp?

Also what hotend are you using?

Edited 1 time(s). Last edit at 08/05/2014 06:54PM by Wildcard.
Re: Rostock problems on the outer regions.
August 05, 2014 07:54PM
Are you sure that your Bowden tube is not bending more at the outer edges of your build area? The increased friction in the tube from the extra bends will cause the filament to drag, and it could be mis-diagnosed as the hotend getting colder at the edges.....
Re: Rostock problems on the outer regions.
August 06, 2014 05:36AM
Thanx for answers!
"The knock of death", yeah, really hate that sound, can hear it from another room when it happens, though its usually because of to low temperature in my case.
But it doesn't looks like its dropping in temp anywhere.
I ran a print last night and looked at it this morning and noticed something, at first print i thought it was the settings that made the print smaller because it didn't think it had the space to print, but take a look at these pictures.
Left side: [www.silfhyttan.se]
Right side: [www.silfhyttan.se]
And whats most interesting, the bottom: [www.silfhyttan.se]
The lines are not straight...
But its only on the right side...
Is one of my motors slower ?

Re: Rostock problems on the outer regions.
August 06, 2014 05:44AM
I print with PLA 1.75 mm
All speeds at 15 mm/s
My hot end is home made, with aluminum cooler and aluminium heating block with a brass nozzle 0.5 mm
Kisslicer set at 0.4 extrusion width and 0.4 layer height.

Edited 1 time(s). Last edit at 08/06/2014 10:05AM by mrg78.
Re: Rostock problems on the outer regions.
August 06, 2014 10:35AM
That is a really interesting/weird effect. The bottom looks it almost moves in a sharp angle as those layers just bunch together. I've never seen that before. I too build my own all metal hotends. When I initially heard the knock I thought about the jamming that I experienced. I used vegetable oil inside the barrel and nozzle to stop the pla from sticking to the bare metal, and a fan to actively cool the exchanger, but the pattern that you show would seem to be a steps problem on one of the towers, if it is repeatable.

Edited 1 time(s). Last edit at 08/06/2014 10:37AM by Wildcard.
Re: Rostock problems on the outer regions.
August 06, 2014 05:18PM
I have a suspicion that the torque required on the outer edges of the delta is higher than when printing in the middle. Have you calibrated the stepper drivers? My stepper drivers were at .65+v. I calibrated all of them to .42v if I recall correctly. This gives me a bit over 1 amp if im not mistaken. Also are you having any mechanical binding? I print ABS at 225c-230c depending on my speeds. Currently doing about 30mm/s Going to step it up soon as the print quality has been really good so far, however I need a geared extruder for this, which I am also designing.

My Personal Blog. Build blog.

Modicum V1 sold on e-bay user jaguarking11
Re: Rostock problems on the outer regions.
August 07, 2014 06:04AM
Had the same problem at first when i had no fan att all, but with a small fan those problem with sticking disappeared.
Though i have a piece of threaded heat resistant plastic to join the cooling part and the heating part, so the heat only travels by air up to the cooling part.

Hmmm, i have not calibrated at all, just put all drivers on default at first but have turned the small screw a bit to increase the amps... do they all have to be exactly the same ?
I didn't think it had anything to do with speeds, just torque
Not sure what you mean with "mechanical binding"
The joints are rostock original in plastic but i have ordered magnets and steel balls, gonna rebuild it with magnet joints.

There is a possibility that thats the problem, to much resistance and on the far edges it moves so little that the joints can't move... maybe try loosen them a bit and use some siliconespray


Edited 1 time(s). Last edit at 08/07/2014 06:11AM by mrg78.
Re: Rostock problems on the outer regions.
August 07, 2014 09:48AM
That is a good idea. I believe jaguarking11 is meaning that there is possibly something off in the mechanical build/parts that is binding/non free motion which is resulting in the problem. Check the system for free movement. Double check the diagonal rod length to make sure that they are exact. I had binding when my diagonal rods were slightly off and that corner where they were different could not travel in a smooth circular motion. This weird print may be a sign to check that all of the mechanics of the machine are good, and allow free circular motion.
Re: Rostock problems on the outer regions.
August 07, 2014 12:51PM
You should really calibrate the stepper drivers. Mine were set to max, which under normal conditions would mean the motors could skip steps due to internal thermal shut down and overheating the steppers to 80c+. Are your stepper IC's sinked? Do you cool the ramps and the stepper drivers? I would check out this link and tune the system properly. I looked for the link on reprap wiki, but the pics seem to be gone, I have the pic from the reprap wiki on my blog build notes. Try this [engineerd3d.ddns.net] Towards the end you will see how it works. I would suggest about .35v instead of .425v that I have, my steppers run at high temp because I went overboard with the amperage, I am going to re-tune them to about .4v.

What I am saying is that the delta design lends itself to small binds in the movement, especially in the extreme, where I suspect the forces are highest, couple that with a thermally overloaded driver that is supplying too much current and possibly a small bind in the movement and you have the makings of missed steps on a single axis.

My Personal Blog. Build blog.

Modicum V1 sold on e-bay user jaguarking11
Re: Rostock problems on the outer regions.
August 07, 2014 06:22PM
I see two issues here.

Deltas tend to print bowl shaped.
Think of a cereal bowl, as you move away from the center it's flat, and moves up slowly , then as you get to the edge it goes up faster and faster.... Yours is doing that, but the other way. As you reach the edge, your head is diving down slightly. It may only be .01mm but it's enough to increase back pressure, causing your extruder to skip. This effect is visible in image 2795 in the top right corner. Further evidence of this is the diagonal line where the head performed a movement early on in the print gets more and more faded as it moves out towards the edge. That diagonal should look the same all the way across the print.

Looking closer, at where the lines bunch up on the bottom, I'm betting your joints have a bit of slop (or magnetics which can give), otherwise, you would have skipped a motor and destroyed the print entirely. Then again, it's entirely possible that it skipped and covered the evidence. Either way, your calibration is off a bit.

As for the print quality itself...
I'm betting you are using a cooling fan off to one side of the build platform. One side of your object is better cooled than the other. Not only that, but your head is experiencing large temperature fluctuations as it moves across the plate. Getting cold as it gets near the fan, kicking on the heater, and then moving away and over heating. Insulate the heat block of your hot end, or install an effector mounted fan. P.I.D. can't help with this.
Re: Rostock problems on the outer regions.
August 09, 2014 04:23AM
That is a very nice guide, will do a calibration as soon as possible. My stepper IC is sinked and i have a 80mm fan over the whole ramps-board to cool it.
The skipping steppes was an issue when i had the amps turned down and when one layer was finished and it had to move to a new location thats much further away, quickly. Then it skipped steppes but then the whole print was destroyed and it continued printing somewhere else.
Shouldn't it be more off if thats the problem, and over the whole print.
But i will certainly calibrate the steppers, thanks !
Thats interesting, i do have tried getting rid of the bowl-shape that your speaking of, but i think i have to much force (or to little) on the joints so it moves a little in Z when it starts moving... hoping the magnet joints will fix that.
Cooling, no, i have a fan mounted to the effector, 40mm fan with half blowing on the cooling part and half blowing down on the printed part.
Like this: [silfhyttan.se]
The print quality is good all around when i print smaller things.
Re: Rostock problems on the outer regions.
October 09, 2014 05:30PM
Hi !
Me again smiling smiley

I've rebuilt the whole thing with magnetjoints... but used to weak magnets so i went back to my original design in wait for stronger magnets...
I loosened the plasticjoints and now it moves really fine, even on the outer regions, have not calibrated the steppers yet though...
I am currently printing a big box, 165x150mm and 100mm high.
As i said in my first post... the speeds are slower on the outer regions, but the filament comes out at the same pace so it kinda floods, small bumps because of to much filament pushed through.
I would like the motor to run a little faster when it comes closer to the end of the print bed, but it doesnt, same pace everywhere.

Anybody have this phenomenon ?
Re: Rostock problems on the outer regions.
October 10, 2014 06:48AM
Maybe more Microsteps ?
Try RADDS. PM me for a Developper Condition if you like...

Mein Club: [hackerspace-ffm.de]
RADDS-Shield -> Commercial [max3dshop.org]
Re: Rostock problems on the outer regions.
October 17, 2014 11:26AM
I think the problem was an unlevel bed, didn't think it could do that much.
Got me an indicator clock with 2 um dial, now its leveled and the prints are much better, close to perfect!

Thanx everybody!
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