Re: Replicator 2 Extruder skipping

[Jetguy]

No, the gears aren't stripping, it's a stepper motor and thus the
sound you hear is called skipping steps. Basically, the motor has
magnetic poles that line up. In order to move, there there 2 phases or
2 sets of poles that line up offset to the rotor. You change coils to
move the rotor forward but if the shaft cannot turn, then you here a
click as the shaft will actually turn backwards to line up with the
previous set of poles. The "click" is the sound of the motor tryign to
move forward, not being able to,and actually spinning backwards a tiny
bit to line up with the previous "step", meanwhile slapping the
filament up and down.

In short, your nozzle is restricted for some reason and thus the
filament can't be pushed into the extruder.
Known causes:
Nozzle too close to platform on first layer
Nozzle obstructed due to burnt plastic in the nozzle too long (leaving
the head heated but not actively printing)
Filament diameter inconsistent causing more friction in a fixed pinch
drive wheel system (see MK8 upgrades on thingiverse)
Crap filament
Nozzle not at correct temperature

On Oct 31, 3:29 pm, Joey Nelson <j...@joescan.com> wrote:
> The bot was working for the last two days, but not seems to be a bit
> unhappy.
>
> This is with default medium settings, with rafts and supports selected.
>
> I don't remember hearing the clicking noise before.
>
> I'm thinking the filament pushing gears are slipping.
>
> http://youtu.be/O5QbU_-M_j0

[Joey Nelson]

I re-ran the shark from the SD, and it still prints fine. 

So there is something with the settings in the slice from MakerWare.

I don't think the nozzle is to close, when I leveled, the paper was just barely getting any friction.

The shark printed fine, so I don't think the nozzle is plugged.

The filament is a fresh roll from MakerBot, so I'd hope it was of sufficient quality.

The shark and my design are both at the default 230 C.  I'm not sure how accurate the control and readout are.

I'll do some more testing with your advice in mind.

Thanks,

[Jetguy]

Retraction or other anti-thread methods to eliminate ooze from the
nozzle when traversing from one place to the next can be problematic
for the exact same reasons. Being that you said it worked from an SD
card print but not from generated gcode from your software clearly
points at settings in the software. Makerware has a very limited
inforace for adjusting anything and thus you might be better served by
using Replicator-g.

> > >http://youtu.be/O5QbU_-M_j0- Hide quoted text -
>
> - Show quoted text -

[Jetguy]

meant to say interface. Loving the lack of an edit function.

> > > >http://youtu.be/O5QbU_-M_j0-Hide quoted text -
>
> > - Show quoted text -- Hide quoted text -

[Mark]

I've had a lot of issues with uneven flow from the extruder. I took some time Friday and reversed the drive gear to eliminate the random slippage I was gettting on the stepper motor shaft. Reversing the drive gear allows the set screw to engage the flat on the motor shaft (which is there for set screws to engage...), instead of relying on the tiny bite that M3x0.5 set screw can make an a hardened motor shaft.  Reversing the drive gear ended up being a bit more complictated than I anticipated because the local HW store didn't have M3x0.5 set screws. So I picked up a 3/16" long 6-32 set screw, drilled out the drive gear with a #34 drill, and tapped it for 6-32. I knew I needed to bore out the heatsink to allow the drive gear to fit in the reversed direction. I used a 9/16" HSS end mill for that job, which worked very good, just plunging down a bit to get the required clearance. Then I had to file off the top of the 6-32 set screw a bit to clear the plastic housing. I suppose I could have filed the housing, but decided to modify the set screw instead (it has plenty of depth for the allen wrench).  Photos are attached.

 

Anyway, this has helped a lot, although I did have a filament stop feeding yesterday when I was showing the unit at the Seattle Maker Group.  A quick push of the filament and it was off printing again.  I've tightened the plunger 1/8 turn, so maybe that will take care of that issue.

 

This issue (feeding irregularities) was discussed a bit at the Maker meeting, as apparently it is a common issue due to irregularities in the diameter and roundness of the filament, especially with lower quality filament.  One of the members highly suggested moving to a spring loaded mechanism with a bearing pressing against the filament at the drive gear, like this one on thingiverse: http://www.thingiverse.com/thing:28241  I'm going to give that a try, as that member said it totally solved all problems he had with filament feed issues.

 

Mark

[Dan Newman]

On 11 Nov 2012 , at 11:47 AM, Mark wrote:

> I've had a lot of issues with uneven flow from the extruder. I took some
> time Friday and reversed the drive gear to eliminate the random slippage I
> was gettting on the stepper motor shaft. Reversing the drive gear allows
> the set screw to engage the flat on the motor shaft (which is there for set

> screws to engage…),

With the Mk8's in the Replicator 1, it's intentional that the flat is not
used. The issue is that the flat doesn't go far enough down the shaft: if
you use the flat, then the centerline of the trough in the pinch gear doesn't
correctly line up with the filament's feed path through the drive block nor
the extruder heater core inlet. People who have done what you then did then
end up with the extruder skipping….

I dealt with this by filing the flat further down the shaft. Rocketsled
had an even better approach. Below is his response in its entirety from
2 November 2012.

Dan

> Yeah. Hitting the centerline of the drive wheel with the filament requires
> the wheel be very close to the stepper motor. The grub screw can't hit the
> flat when that spacing is as specified by MBI.

> Mechanically, there's no reason you wouldn't want to hit the flat. The
> whole reason for the shaft having a flat is, after all, to ensure that
> whatever is attached to the shaft doesn't require an "infinitely tight"
> grub to lock it down to the shaft.

> All that's required to fix this is a few washers between the face of the
> stepper and the back side of the filament feed/guide block, which would
> move the motor back slightly, which would let the drive wheel move forward
> on the shaft slightly, which would allow the grub to hit the flat and
> actually do what it's supposed to do and allow the filament to align
> properly with the center of the drive wheel.

> The Rep1 is a great machine, don't get me wrong, but there are quite a few
> areas of the design that present opportunities for improvement. This is one
> of them. Using thread locker is another.

[Mark]

On Sunday, November 11, 2012 2:26:37 PM UTC-8, dnewman wrote:

With the Mk8's in the Replicator 1, it's intentional that the flat is not
used.  The issue is that the flat doesn't go far enough down the shaft: if
you use the flat, then the centerline of the trough in the pinch gear doesn't
correctly line up with the filament's feed path through the drive block nor
the extruder heater core inlet.  People who have done what you then did then
end up with the extruder skipping….

I don't see the issue.  You just need to line up the drive gear with the filament slot.  I started a big print yesterday (half done after 14 hours...), and it hasn't skipped yet.

I dealt with this by filing the flat further down the shaft.

 

Just make sure you don't get filings into the motor bearings.

 

 Rocketsled
had an even better approach.  Below is his response in its entirety from
2 November 2012.

> All that's required to fix this is a few washers between the face of the
> stepper and the back side of the filament feed/guide block, which would
> move the motor back slightly, which would let the drive wheel move forward
> on the shaft slightly, which would allow the grub to hit the flat and
> actually do what it's supposed to do and allow the filament to align
> properly with the center of the drive wheel.

Of course this requires manually lining up the drive gear with the filament slot, as did my approach, and has the downside of moving the pressure point on the shaft further from the motor, increasing the lateral torque on the motor and bearings.  Don't know if that would lead to issues down the road.

 

Mark

 

[Guidozelf]

I've just made the Minimalistic Mk8 replacement from emmet (http://www.thingiverse.com/thing:28241) which allows for a spring loaded ball bearing to feed the filament.

I feel the spring load is essential here: look at the comments on Thingiverse ;-)

My Replicator 2 has never (not even when just unpacked) printed so beautiful and smooth as after this upgrade. It's beyond me why Makerbot hasn't done this as standard, but perhaps things aren't so bad with ABS as with PLA (my only experience is with PLA ,as I only have a Rep 2).

In order for this mod to fit, you need to modify the black plastic cover that's holding the filament tube: you need to cut out a small piece.

I used a Dremel for this, at low speed, after disassembling the 6 Hex screws and disconnecting a few wires. Easy, fast and simple proces.

I'm now printing at 0.1mm with RepG40 and MBI firmware 6.2 without any problems, no clicking, no missing plastic and smooth as a baby (is that the expression?) ;-)

I've made a few pictures, may be that helps you with the build / mod. Highly recommended!

BTW: From the second photo you can see I needed this badly: I was almost unable to print the 2 pieces needed for the mod......;-)

Cheers, Guido

Op woensdag 31 oktober 2012 20:29:14 UTC+1 schreef Joey Nelson het volgende:

[Joey Nelson]

Based on Guido's success, I also made this upgrade.  It completely fixed the problem with the motor stalling during MakerWare generated rafts.

It is very easy.  I thought about altering the design to avoid having to cut the cover plate, and still think that would be nice to make the upgrade more friendly for other Replicator 2 folks.  But it was easy to just cut out the notch with a coping saw.

Based on this I now conclude the MakerWare is not crap.  The problem is either the plunger design, the quality control of the setting the plunger, or the filament quality.  But for all these cases the Minimalistic Mk8 replacement is the fix.

[Hammerhead]

I'll confirm Dan's comments.  Had the same trouble with a slipping drive gear also.  It's beyond me why MBI wouldn't take the time to fix this issue, but my solution was to use a Dremel and create a flat at the base of the shaft.  I've included a few photos (before/after) to show where the set screw sits and how there's nothing to grab onto and what my motors look like now after the modification.

[66tbird]

nice pics and yes it's a head scratch-er why MBI didn't catch that. At least it was an easy fix. Good practice for future problems or upgrades.

[Shawn]

Turn the gear around, line it up so the teeth are in the correct
location, lock it down on the flat part. Or is there a reason not to do
this? (I noted the same issue on my Rep1 but never really had an issue
with slipping since I last check the grub screws... knock on wood.)

On 12-11-13 06:32 PM, Hammerhead wrote:
>
> I'll confirm Dan's comments. Had the same trouble with a slipping drive
> gear also. It's beyond me why MBI wouldn't take the time to fix this
> issue, but my solution was to use a Dremel and create a flat at the base
> of the shaft. I've included a few photos (before/after) to show where
> the set screw sits and how there's nothing to grab onto and what my
> motors look like now after the modification.
>
>

> <https://lh3.googleusercontent.com/-Dw5KLlg6egw/UKLzu2n5f3I/AAAAAAAAAPo/a7Ydt0NQ3Cs/s1600/DSCN4027.JPG><https://lh4.googleusercontent.com/-MDmt9oTq4Yg/UKLzz_bmDwI/AAAAAAAAAPw/4LrcgUgrP8A/s1600/DSCN4030.JPG>

>
>
>
> On Sunday, November 11, 2012 5:26:37 PM UTC-5, dnewman wrote:
>
>
> With the Mk8's in the Replicator 1, it's intentional that the flat
> is not
> used. The issue is that the flat doesn't go far enough down the
> shaft: if
> you use the flat, then the centerline of the trough in the pinch
> gear doesn't
> correctly line up with the filament's feed path through the drive
> block nor
> the extruder heater core inlet. People who have done what you then
> did then

> end up with the extruder skipping�.

>
> I dealt with this by filing the flat further down the shaft.
> Rocketsled
> had an even better approach. Below is his response in its entirety
> from
> 2 November 2012.
>
> Dan
>

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[Dan Newman]

On 13 Nov 2012 , at 6:48 PM, Shawn wrote:

> Turn the gear around, line it up so the teeth are in the correct location, lock it down on the flat part. Or is there a reason not to do this? (I noted the same issue on my Rep1 but never really had an issue with slipping since I last check the grub screws... knock on wood.)

That was the point of my post and Rocketsled's -- there is an issue with doing that as it causes
the trough of the pinch gear to no longer line up with the filament guide in the black extruder
block nor the inlet to the extruder's heater core. That because the flat doesn't extend down
far enough. You can extend the flat by grinding/filing or cause the black block to sit a little
farther away from the motor face with washers (Rocketsled's solution).

Dan

[Shawn]

When I say turn the gear around, I mean flip it over so that the grub
screw is not on the bottom, but on the top. (assuming the motor shaft is
pointing up). Or in 3D terms, rotate 180 degrees on the X or Y axis,
not the Z axis.

[Dan Newman]

On 13 Nov 2012 , at 7:11 PM, Shawn wrote:

> When I say turn the gear around, I mean flip it over so that the grub screw is not on the bottom, but on the top. (assuming the motor shaft is pointing up). Or in 3D terms, rotate 180 degrees on the X or Y axis, not the Z axis.

Ahh, I see what you meant.

So, drum roll please …… you can get a useful trough alignment when you do that? (Presumably the answer
is affirmative since presumably you wouldn't have said so otherwise.)

Thanks,
Dan

[Mark]

On Tuesday, November 13, 2012 7:30:54 PM UTC-8, dnewman wrote:

So, drum roll please ……  you can get a useful trough alignment when you do that?  (Presumably the answer
is affirmative since presumably you wouldn't have said so otherwise.)

Sure, look at the photos I posted.  The only issue with flipping the gear is you have to mill out a clearance hole in the heat sink (again, see photos I posted).

 

Mark 

 

[Steve]

In order to make the Minimalistic Mk8 replacement from emmet (http://www.thingiverse.com/thing:28241 for the Replicator 2 do you just need to print the extruderR.stl file and then add the bearings and springs. When you actually have a Replicator 2 is it obvious how the parts go together? Mine has not arrived yet so I don't quite see how it fits in.

On Monday, November 12, 2012 6:55:56 AM UTC-8, Guidozelf wrote:

[Mark]

On Tuesday, November 20, 2012 6:13:21 PM UTC-8, Steve wrote:

In order to make the Minimalistic Mk8 replacement from emmet (http://www.thingiverse.com/thing:28241 for the Replicator 2 do you just need to print the extruderR.stl file and then add the bearings and springs. When you actually have a Replicator 2 is it obvious how the parts go together? Mine has not arrived yet so I don't quite see how it fits in.

 

Yes, just the extruderR.stl, and it is pretty obvious how it goes together.  The only things you need to purchase are a spring, a M3x10 machine screw (button head works best), and a 3x8x4mm bearing or a 3x10x4 bearing.  If you look at the comments on Thingiverse, you can get part numbers for McMasters, which is probably the easiest way to go, although between the local hardware store and a hobby shop that specializes in helicopters, I was able to find what I needed locally.  I put in a 3x8x4 bearing, and that is working fine, but I have a 3x10x4 coming and I'll probably put that in just to give a bit more clearance from the arm to the filament.  I used a #31 drill to clean up the holes in the printed parts (don't clean up the hole that the bearing machine screw screws into though!).  Look at this thread to see the notch you need to cut in the top plastic cover.  I just finished installing mine this afternoon, and my prints are *so* much better!  Makerbot should incorporate this change into the R2, along with making it so the drive gear set screw engages the flat on the stepper motor.  Those changes would eliminate every problem I've had with the R2 thus far.

 

Mark

 

[Mark]

BTW, the hobby shop bearings were for an Align helicopter, part number HS1029T, which includes 4 of the 3x8x4mm bearings (693ZZ).

 

[Infinityplusplus]

Not that I want to push this design, just hate to see anyone cut the plastic on thier REP 2 that doesnt want to.

Same concept, no cutting. 

 http://www.thingiverse.com/thing:35810

[Mark McGovern]

I had the same issues crop up after about 50 hours of relatively trouble-free printing: uneven/stopped extruder flow, nasty "clicking" sound.  I reversed the drive gear per Mark's description and it is printing better than it ever has before.  I'm printing a part that will take at least 7 hours to print now.  If I don't re-post, assume this has worked.

Mark

[Andy Cohen]

YES. That is exactly what I have been thinking! MInimize ALL friction between the spool to the stepper motor. One way to do that is minimize the path from the spool to the extruder.

If Makerbot had actually hired ENGINEERS they may have though of that!

On Friday, February 1, 2013 12:10:49 PM UTC-8, Timesaint wrote:

Hi there, everyone - Rep2 owner here:

I had a similar problem; my prints would stop extruding for a while and start again, or stop completely while making that sickening clicking sound.  I adjusted my plunger, cleaned the motor and extruder, etc. - I could not get a print to last longer than 6 hrs.

Two days ago, I decided to reduce the force needed to pull the filament into the extruder by this very complex step:

I hung my filament directly above the machine.  

Problem solved; got a very clean 22hr print of the PLA big nip cube and many other short prints.  Haven't seen the problem since.

My reasoning:  Mounting the spool to the back of the unit causes the filament to turn a full 180 degrees before getting into the extruder.  In the guide tube, even though it is a fairly slick surface, this causes friction that the motor has to compensate for.  Now that the filament bends no more than 30 degrees, it requires much less pull by the motor to draw the filament in.

While I am planning on installing http://www.thingiverse.com/thing:42250 tonight, as my spring just arrived, I'm so much happier with my bot.

Good luck!

[Gary Crowell]

I've been printing for weeks with my ABS spools on top of the hood of my Replicator, with the spool on a bearing spool roller.  Absolutely zero problems, and I can change a color is less than a minute.  I do need to get a sturdier surface in place though, before I break the acrylic hood.

Gary

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