Is my Rostock Max2 possessed by demons?

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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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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.

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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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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.

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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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Re: Is my Rostock Max2 possessed by demons?

Postby Muppo » Wed Apr 11, 2018 7:26 am

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


Did you ever get your problem fixed and how did you do it? I have the same issue but it only happens with some prints, and I had my colleague take that same file and print it on his prusa mk2s with no issues.

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Re: Is my Rostock Max2 possessed by demons?

Postby rootboy » Wed Apr 11, 2018 10:15 pm

Looking at the video again, it looks like the problem started at the 40 second mark. That's when the stepper motor slipped (that's the noise you hear).

You could try upping the motor currents for X,Y & Z, just make a note of the "before" currents, and don't go crazy.

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Re: Is my Rostock Max2 possessed by demons?

Postby awerby » Mon Apr 16, 2018 5:43 pm

This printer has a lot of problems, but I'd like to get it working. How does one change the motor current? And which hot end is the most reliable? Mine has stopped spitting out plastic reliably; I think the filament must be getting hung up somehow, although it may have to do with the feed mechanism. Even when it was working, the parts were way out of spec - there's apparently some way to fix that having to do with changing the registered arm lengths - is that a matter of trial and error, or is there a formula?

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Re: Is my Rostock Max2 possessed by demons?

Postby rootboy » Mon Apr 16, 2018 9:21 pm

Go to your G Code terminal and type in "M906" (be sure to capitalize the "M") and hit enter. This will give you your current settings and they will displayed in more or less this format:

Code: Select all

M906 X1200 Y1200 Z1200 E800 I30    ; Set motor currents (mA) and motor idle factor in per cent


Be sure to save this and then you can modify the values as needed.

For reference, this is what my settings mean:

X1200 - 1200 milliamps for the X axis. Y & Z the same thing. I30 is the idle factor (30% in my case).


I'm very happy with my Prometheus hotend. I've had to burn out a clog once, but that's it. You simply take the nozzle out, hit it with a torch, wait for the smoke to clear and for it to cool off, and put it back in. Simple.


As for feeding the filament, I've never been a fan of the Rostock's "Ezstruder". It would either strip out the filament, or the stepper would lose counts and pop backwards. I replaced my NEMA 17 extruder stepper motor with a NEMA 23 (although if I had it to do over again I would use a NEMA 17 that has a gearbox on it to reduce speed and increase torque). I replaced the Ezstruder with Prusa knockoff:

https://www.ebay.com/sch/i.html?_from=R ... l&_sacat=0

You can see what I did here:

viewtopic.php?f=37&t=12208&p=106843#p106843


But before you do all of that, turn the power off on the printer and pull the hotend down to the glass and take it to the furthest point as possible from the extruder. Look at your bowden tube and see if you can take a few inches off of it. This will reduce the friction of the filament in the tube. If you mess up, well, spare tubes are cheap. :)

Now raise it up off of the glass and turn the printer on (but don't turn on either heater). Home the beast and grip the hotend and rotate the hotend in a circle. Do your arms have any play? Ideally, you won't have any. Take a video if you do have any and let us look at it.

Next, I would take the arms off of the carriages and check for slop and/or tightness in the carriage rollers.

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Re: Is my Rostock Max2 possessed by demons?

Postby rootboy » Mon Apr 16, 2018 9:54 pm

Oh, and after looking your video a few more times, it looks like the X axis "took a dive" starting the mayhem. Open up the area where your controller is and be sure that your stepper motor wires and your heater wires don't cross over the board. Route them as necessary to avoid EMI from triggering your stepper driver. It's a longshot, but it's free...

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Re: Is my Rostock Max2 possessed by demons?

Postby awerby » Tue Apr 17, 2018 1:05 am

It does seem like some kind of EMI issue; that sounds like a good plan, thanks. Is it proximity to the board the main thing that needs to be avoided, or proximity of the heater wires to the stepper wires, or having the wires cross? Would slipping a grounded braided shield over one or another wire sets help?

The jamming issues you solved with the NEMA 23 motor sound a lot like what's happening with my machine as well. If I replaced my 17 with a gearhead 17, and the stock extruder with one of the Prusa clones, what else would I have to do to the settings to make it work?

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Re: Is my Rostock Max2 possessed by demons?

Postby rootboy » Tue Apr 17, 2018 1:59 am

Mostly you want the wires exiting the area as quickly as possible. The heater wires crossing the stepper wires shouldn't be a big deal, but any crossings that you make are best done at 90 degree angles.

The sleeve idea is a good one (why didn't I think of that?), but I would buy a blank single-sided PCB (https://www.ebay.com/itm/1-2-4pcs-Singl ... sbbOjP7Kmw) and cut it to size using tin snips and solder your ground wire to it. Use painter's tape to insulate the copper side, and mount it over the stepper drivers. If you've got an empty hole available, great, use it. Otherwise wrap another wrap around the controller and the PCB to keep it in place. Or use hot-melt glue, whatever works. Attach the ground wire to the negative terminal. And if you like, you could do both the braid and the PCB. Just be sure that there are no bare wires and/or surfaces. And try to keep the PCB clear of the fuses, but that shouldn't be hard to do.

Now would be a good time to add heat sinks to the stepper drivers. If I went that way, I would consider foregoing the PCB and remove the insulation of your ground wire at intervals that match the spacing of the steppers (or just strip the entire wire and use short pieces of heat shrink tubing between the heatsinks) and press the wire between the fins. Now take a pair of pliers and crimp the fins that are on either side of the wire together and stick those suckers onto your stepper drivers. Now you get shielding and cooling. :)

If you get the gearhead motor, pay close attention to the shaft diameter, and if you have to, buy a hog gear that will fit. The new hog gear should come with a shorter set screw which should clear the "hump" where the grooved roller's pin screws into the swing arm. If not (as was in my case), unscrew the bolt holding the grooved roller and remove it. Now use a Dremel to sand a radius to allow the set screw to clear the swing arm. You will possibly have to sand into the hole for the grooved wheel bolt, but so be it. If this is the case, reinstall the grooved wheel and run the bolt in from the opposite side and tighten it down. And just to be clear, sand just the side of the swing arm that interferes with the set screw.

As for firmware adjustments, if your gearhead motor has say a 5:1 ratio, then you would multiply the extruder counts in M92 by five. This should get you close, but you will want to follow that up by disconnecting the bowden tube at the hotend, extrude enough filament to get it past the end of the bowden tube, cut the filament flush with the tube, and extrude 100mm of filament. Now measure what got extruded and adjust your settings until you get 100mm of filament when you extrude 100mm.

My step counts per mm ("E80" is the one that you will want to adjust).

Code: Select all

M92 X160 Y160 Z160 E80             ; Set steps per mm


Do us a favor, and send "M906" to your controller from the terminal and let us know what you get, please.

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Re: Is my Rostock Max2 possessed by demons?

Postby awerby » Tue Apr 17, 2018 4:29 pm

Okay, I'll do that and report back. In the meantime, I was looking at the Prometheus system you recommended. https://www.distechautomation.com/produ ... eus-system Did you get the multi-filament kit, or just the hotend? It has this note:

"The Prometheus System is compatible with 3D printers that support the following:
Dual extruder stepper drivers on the controller board
Cura slicer engine or Simplify3D
Marlin/Repetier/Smoothieware based firmware (this includes almost all desktop 3D printers)"

Does the Rostock Max2 have all that?

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Re: Is my Rostock Max2 possessed by demons?

Postby rootboy » Tue Apr 17, 2018 8:01 pm

The dual extrusion system of theirs was in development when I bought mine, so I just have the single. Do yourself a favor and reach out to owners of the dual system to get their settings, and to see how well it is working before buying one.

I'm really not sure what constitutes an extruder that *wouldn't* work, since as long as you can adjust your settings, you should be fine. I use mine with MatterControl, Repetier, and the web interface that came with the Duet. No problems.

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Re: Is my Rostock Max2 possessed by demons?

Postby awerby » Wed Apr 18, 2018 3:13 pm

I tried sending the M906 code from the terminal, but all that happened was that it generated a blank "print log". Do I have to do that while trying to print something?

I peered at the board that's stuck underneath the platform of the Rostock. Is there an easy way to get access to it to make all those modifications you were talking about? Do I have to disassemble the base of the printer, or is there a trick to this?

And yes; if anybody is using one of those Prometheus dual extrusion systems, how is it working? What settings are you using?

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Re: Is my Rostock Max2 possessed by demons?

Postby Xenocrates » Wed Apr 18, 2018 10:44 pm

So, with the Rostock max 2, you can take the LCD panel off, then pull the controller mount forward to release it, and if you have slack in the wiring, remove it.

Also, of note is that Allegro, and the majority of the SMD stepper drivers, are not designed with a usable thermal interface at the top of the driver. To improve cooling, increase the cooling fan size behind the Rambo. They have a specific pad at the bottom to sink heat to, and the Rambo has thermal vias to take the heat to the ground planes of the board.
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Re: Is my Rostock Max2 possessed by demons?

Postby rootboy » Wed Apr 18, 2018 11:53 pm

Xenocrates wrote:Also, of note is that Allegro, and the majority of the SMD stepper drivers, are not designed with a usable thermal interface at the top of the driver.


That's right, thanks for the reminder!

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Re: Is my Rostock Max2 possessed by demons?

Postby rootboy » Thu Apr 19, 2018 12:00 am

Did you try bumping up the current first?


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