Is my Rostock Max2 possessed by demons?

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awerby
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Is my Rostock Max2 possessed by demons?

Postby awerby » Thu Nov 09, 2017 3:53 pm

I got this Rostok Max2 recently, and at first it was printing pretty well. Then in the middle of a long print it shifted over and ruined the part. Since then it's been all downhill - while it seems able to print small things like the sample coin and calibration cube, on anything larger, like the stand (for what?) it prints normally for a while, then suddenly freaks out, like it's having a seizure of some sort, and crashes into the part, or veers wildly off course, and starts spitting out spaghetti. I went a few rounds with tech support - they seem to think it's a mechanical issue to do with backlash (too much) and belt tension (not enough). I'm doubting that - it's hard to believe that that would affect more than one axis at a time, as this seems to. To me, it seems that the motors are getting some kind of bad signal that's causing them to fault -
from a wire working loose somewhere and sparking? But I'm new to this thing - what do you think? I've attached a vimeo link to a video which shows the issue, about a minute in: https://vimeo.com/242127189

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thingismith
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Re: Is my Rostock Max2 possessed by demons?

Postby thingismith » Thu Nov 09, 2017 9:05 pm

Hmmm, can't say that I've had that problem before. I'm inclined to agree with the techs about the belt tension. It looks like the hotend got caught on the print (maybe the hotbed), causing the belt to slip on one of the axis, which threw off the rest of the movements. It shouldn't be that difficult to adjust the tension from the top.

I'm wondering if those old carriages might be the problem. If they're a little too snug on the bars, it could put strain on the belt and cause it to slip on the motors. See if they're tight, try loosening them a tiny bit. If it helps, I'd recommend upgrading to the cheapskate carriages.

What's your print speed? Was the hotend tilted when it "became possessed" in the video? It kind of looked like it was...if so, there's something definitely up with the carriages, maybe the arms.

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Re: Is my Rostock Max2 possessed by demons?

Postby IMBoring25 » Fri Nov 10, 2017 1:03 am

Everything that happens after it "suddenly freaks out" is because the effector is no longer where the electronics think it is. Deltas do goofy things when they don't know where in the build volume they are.

What slicer are you using? I have read something about Simplify3D making excessive numbers of segments and the Rambo doesn't have a lot of extra processing capacity. It also almost looks like the nozzle might be getting stuck to the part. What material is this and what temperature are you using?

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Re: Is my Rostock Max2 possessed by demons?

Postby geneb » Fri Nov 10, 2017 7:39 am

Your rapid speed might be too high (more than about 225mm/sec) and that'll cause the motors to skip steps.

Other things that could make the steppers skip steps are having carriages that grip the tower too tightly, or u-joint binding. You can test for the u-joint binding by taking the arm off the u-joint and then rotate it by and to see how easily it moves. There should be [i]zero[/o] resistance for the entire 360 travel around the support pin.

I really recommend that anyone that's got the old arms and carriages upgrade to the "new" injection molded carriages (no more fussy adjustments) and the ball & socket arms.

g.
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Re: Is my Rostock Max2 possessed by demons?

Postby awerby » Sat Nov 11, 2017 3:58 pm

thingismith wrote:Hmmm, can't say that I've had that problem before. I'm inclined to agree with the techs about the belt tension. It looks like the hotend got caught on the print (maybe the hotbed), causing the belt to slip on one of the axis, which threw off the rest of the movements. It shouldn't be that difficult to adjust the tension from the top.

I'm wondering if those old carriages might be the problem. If they're a little too snug on the bars, it could put strain on the belt and cause it to slip on the motors. See if they're tight, try loosening them a tiny bit. If it helps, I'd recommend upgrading to the cheapskate carriages.

What's your print speed? Was the hotend tilted when it "became possessed" in the video? It kind of looked like it was...if so, there's something definitely up with the carriages, maybe the arms.


[The tech support guy said to make the wheels more snug on the bars; when I checked, it did seem that they were rather loose, so I did that. I thought I'd see if that helped before messing with the belt tension, since the manual warned about making it too tight. I thought the "cheapskate" carriages were the ones I had - are mine even cheaper?]

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Re: Is my Rostock Max2 possessed by demons?

Postby awerby » Sat Nov 11, 2017 4:05 pm

IMBoring25 wrote:Everything that happens after it "suddenly freaks out" is because the effector is no longer where the electronics think it is. Deltas do goofy things when they don't know where in the build volume they are.

[How do the electronics keep track of the hot-end's position? I thought this was an open-loop system, where commands are issued but there's no way to tell if they were carried out. Are there some kind of encoders or accellreometers in the system someplace?]

What slicer are you using? I have read something about Simplify3D making excessive numbers of segments and the Rambo doesn't have a lot of extra processing capacity. It also almost looks like the nozzle might be getting stuck to the part. What material is this and what temperature are you using?


[I'm using the default MatterControl slicer; I'm not sure which one it is (Kiss?) It's not Simplify3d; that's the one you have to pay for, right? I'm using clear "natural" PLA, but it's not premium filament by any means - it broke in the middle of a print trial. But I don't think the hot end actually stuck to the part.]

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Re: Is my Rostock Max2 possessed by demons?

Postby awerby » Sat Nov 11, 2017 4:13 pm

geneb wrote:Your rapid speed might be too high (more than about 225mm/sec) and that'll cause the motors to skip steps.

[I was starting to suspect that as well, so I slowed it down to 85%. That (or increasing the preload on the carriages) seemed to help; at least I was able to print 50% of the Stand without having a freakout (I'll check to see if it actually finished when I get back to it.)]

Other things that could make the steppers skip steps are having carriages that grip the tower too tightly, or u-joint binding. You can test for the u-joint binding by taking the arm off the u-joint and then rotate it by and to see how easily it moves. There should be [i]zero[/o] resistance for the entire 360 travel around the support pin.

I really recommend that anyone that's got the old arms and carriages upgrade to the "new" injection molded carriages (no more fussy adjustments) and the ball & socket arms.

g.


[I did notice that even after tightening the carriages, the head was able to rattle around a bit - it didn't seem to be held very firmly at all. Would the new ball-and-socket arms fix that? Even when it was working OK, I noticed a lot of surface discrepancies in my printed parts; would that be minimized with better arms?]

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Re: Is my Rostock Max2 possessed by demons?

Postby thingismith » Sat Nov 11, 2017 4:16 pm

awerby wrote:[The tech support guy said to make the wheels more snug on the bars; when I checked, it did seem that they were rather loose, so I did that. I thought I'd see if that helped before messing with the belt tension, since the manual warned about making it too tight. I thought the "cheapskate" carriages were the ones I had - are mine even cheaper?]


The ones you have are seemecnc's original carriages. Here are the new carriages:
https://www.seemecnc.com/collections/parts-accessories/products/injection-molded-cheapskate-carriage-set
I remember using a screwdriver to use as a lever to lift the top pulleys to make it taut, just don't use too much muscle and overdo it.
Last edited by thingismith on Sun Nov 12, 2017 1:35 pm, edited 1 time in total.

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geneb
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Re: Is my Rostock Max2 possessed by demons?

Postby geneb » Sun Nov 12, 2017 9:25 am

The ball & cup arms & carriages result in a very tight motion system. You can't "stir" the hot end like you can with the original arms.

g.
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Re: Is my Rostock Max2 possessed by demons?

Postby rootboy » Thu Nov 16, 2017 2:39 am

What I would do to determine whether it is a case of the hotend hitting the print and thus causing the skipping, or the arms "skipping" causing the crash into the print, is by loading a 100mm x 100mm x 100mm cube and printing that *without* any filament loaded. Come back midway through the (air) print and pause it, and then take some measurements.

And for forty or so bucks more, you can get the Trick Laser carriages. That will probably be my next upgrade.


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