Belt Jumping or something similar?

[milp]

Hi there,

Yesterday my Rostock max v2 'crashed'. The hot end jammed up at a corner of my print warping upwards and it ended up breaking off a delta arm from the X axis and unhinging the other.

Since it was a rather 'clean' breaking point, I was able to cleanly solder the broken piece back in place with my soldering iron and some ABS Filament at 230°C

Did a full height calibration and thought i was ready to print a new delta arm.

http://reprap.org/wiki/File:10-11-12_RO ... EMECNC.zip (The printable version)

Every time the hot end arrives at a certain point after printing maybe 5-8 layers, one of the axis carriages starts to jump with no appearant reason. It is as if one of the belts has worn off at a certain point and starts jumping, but i inspected all the belts, they seem fine and i also retightened them.

What else is there that could cause this behavior if it's not the belts? I also tried positioning the hot end in a similar area and pushing the cheapskate carriers with my hands with the motors fixed by Repetier Host (it does that when in idle for some reason). The belts won't jump.

Pressing against the moving carriages during the times the "jumping" occurs will not provoke it to jump more, it's as if it only happens on its own. Only if i apply excessive force it causes the belt to jump slightly, but that feels and sounds completely different to the jumping. (I know that might be a tad unorthodox, but i'm really out of ideas here)

[Earthbound]

Is one (or more) of the cheapskates hitting the base plate? The arm model might be too long to print. The RMV2 in stock form is not actually capable of the 11" diameter build area that is advertised.

[milp]

No, at the point where the jumping occurs or any time before that during printing the cheapskates are not touching the baseplate. That is the case if i take that delta arm and rotate it by 90 degrees so it is aligned with the Z axis tower, then exactly that happens. Is it possible that in this direction (90° to the Z axis tower) the build diameter is slightly bigger?

After the jumping occured though, the position will be so far off that the nozzle will eventually hit the heatbed.

How much is it for the RMV2 then actually? That's kinda disappointing to read.

Edit:

It might be worth mentioning that the point where it starts to jump is a few layers into the print, near the end of the print rod pointing towards the Y axis, from there on it moves further towards the end of the rod pointing towards the X axis and usually jumps a few more times with a loud "tock" sound, similar to the one belt jumping makes but much deeper and with more intensity.

I'm having a really hard time trying to give an accurate description of this behavior, i hope someone understands this

[Earthbound]

The basis of stating that the buildable area diameter has to be less than 280mm is this: delta arm length is 269mm. When head is closest to a tower, arm is vertical. Call that a reach of 0. When head is farthest from same tower, the reach would be 269mm if the arm could go horizontal, which it can't. The geometry might result in a greater allowed travel at right angles to a tower, but my head isn't prepared to run those numbers. If you define the build area as a circle, it is somewhere in the 260's.

I really think that loud tock sound may be the skate striking the base. Because of the radiused edges/corners of the arm model you are trying to print, the maximum length of the part will be several layers up off the glass.

You can air/ghost print the model to check travel limits. No need to waste filament. I would try it centered on the bed and 90 degrees to the Z tower (9 to 3 o'clock).

[milp]

Ghost printing is a great idea!

It always seems to happen at the same position, its approximately this:

http://i.imgur.com/PF8lD3Y.jpg

Notice that none of the Cheapskates is even close to the bottom plate.

However when dry printing i noticed that it happens more and at earlier point when i increase the speed above 200% (was previously printing at 100%) and it does not happen at all at 50%.

I'm still confused as to what caused this weird behavior, seeing how everything points towards the belt jumping a few teeth at times, yet all the teeth are intact and the belts are freshly tensioned.

Should i just increase belt tension to assure accuracy at 100% speed?

Edit:

by the way, in terms of 28cm build radius, it even manages to print a skirt around the 28cm long rod:

http://i.imgur.com/Z2aBPld.jpg

[KAS]

I can only print that far out by slowing down the print. It's possible you're loosing steps that far out.


Removing my dampers helped as-well. Do you have those on by chance?

[milp]

I can only print that far out by slowing down the print. It's possible you're loosing steps that far out.


Removing my dampers helped as-well. Do you have those on by chance?

Yeah i have no problem slowing down, i was just wondering if its normal. I'm aiming to print 0.025mm layer parts and halving the speed will make days if not weeks of difference in printing time

What exactly are dampers in 3d printer terms?

Is there a way to tell mattercontrol to slow it down in terms of gcode generation when the hotend comes closer to the edge? Something like a "center speed multiplier" that gradually lessens as the hotend moves away from the center.

[KAS]

Nema 17 dampers, chances are you dont have them. http://astrosyn.com/section.php/44/1/vibration_dampers

I don't believe MatterControl has that option.

This is pretty much all you get with MatterSlice. While perimeter speed will slow it down on the very edge, it wont help with the next layer in.

Perimeters - _mm/s: Sets the default movement speed while printing perimeters.
Small Perimeters -_mm/s or %: Used for small perimeters (usually holes). This can be set explicitly or as a percentage of the Perimeters’s speed.
External Perimeters: The speed to print the visible outside edges. This can be set explicitly or as a percentage of the Perimeter’s speed.
Infill: The speed to print infill.

[milp]

Oh ok, thanks.

While we're at it, where can i get the STL files for the rostock max v2 delta rods? The ones i printed are turning out very hard to fit.

[Earthbound]

Oh ok, thanks.

While we're at it, where can i get the STL files for the rostock max v2 delta rods? The ones i printed are turning out very hard to fit.

I don't understand what you are trying to find. The STL's you are asking about are at the link you included in your first post of this thread, right?

[milp]

Oh ok, thanks.

While we're at it, where can i get the STL files for the rostock max v2 delta rods? The ones i printed are turning out very hard to fit.

I don't understand what you are trying to find. The STL's you are asking about are at the link you included in your first post of this thread, right?

Those are for some older version of the Rostock Max, they don't fit the v2, the U Shaped ends are way too short. I was thinking of printing the rods pointing upwards to ensure accuracy.