Extruder motor will not push filament on replicator dual extrusion.

[David Jasiewicz]

For some reason my step stepstruders started to have the problem of not having enough power to push filament.  I know this sounds weird, but both extruders went from working fine to not working at the same time.  Also, I have never had this problem before on either extruder.

The filament goes in as expected, but when it tries to push it though the nozzles, the motors loose steps.  It is not stripping the filament and it is gripping properly.  This problem occurs when I use the load filament function too.  I just get a feed-skip-feed-skip a couple times a second.  The nozzles are clean and not clogged.

The print will go to completion, but as you can see in the photos, only a fraction of the plastic actually comes out.  During the whole print, you can hear the faint clicking of the motors slipping steps.  The drive wheel is not slipping on the shaft.  This faint clicking tells me that the motors are not receiving enough voltage/current to drive the filament.  Both stepstruders are acting exactly the same.  This is telling me there is a problem with the controls somewhere.

I wanted to try and narrow down the problem more. I removed all the washers and tried to load the filament. As expected, the teeth could not grab it. I increased washers one at a time until it started to extrude. Now it is back to the motor skipping steps. There is a one washer difference between not feeding and skipping steps. The motors do not have enough power to actually strip the filament. Either way I need to push it by hand to make it extrude. This is the same on both extruders. I removed the fan and heatsink, to confirm that the motor is not turning.

I am really getting stumped as to why the motors just quit pushing the filament. I have bumped the extruders all the way up to 230C for PLA to make sure the resistance is very low on the nozzles. I can easily push the filiment through by hand if I completely remove the motors. In fact, it only takes slightly more force by hand only then if does to help the motors feed it.

I removed the extruder motor and put it on the filament load function and was able to stall the motor by holding the gear between my finger and thumb with a moderate force. I don't know if this is normal.

I am using Makerware 2.1.0.61 and firmware 7.2 

Any suggestions your be a huge help.

Thanks,

 `Jaz

[DHeadrick]

You already posted this same problem here:
https://groups.google.com/forum/?fromgroups=#!topic/makerbot/jJUJfjKXsbU

It isn't good etiquette to post the same thing more than once.  Plus you dilute your answers between 2 discussions making it harder to find all the information.

That being said... I don't have any advice.  Sorry.

[David Jasiewicz]

I guess I have a different problem.  I can't find my previous post.

[David Jasiewicz]

Here is one more photo.  On the right is what should be printing.  On the left is what I am getting.

On Wednesday, May 22, 2013 2:07:29 PM UTC-7, David Jasiewicz wrote:

[David Jasiewicz]

So I have eliminated "most" of the skipping by printing ABS at 260C and reducing the print speed to 40mm/s.  I will keep trying other options.

On Wednesday, May 22, 2013 2:07:29 PM UTC-7, David Jasiewicz wrote:

[David Jasiewicz]

So I have some results.  It appears my temperature controller is failing.  I keep cranking up the temperature and maxed it out at 260 and I am still getting some skipping, but it is almost usable.  As the print goes on, it gets worse.  I can only for PLA, because it will not get hot enough for ABS.  Has anyone dealt with fixing this issue?

Thanks. 

On Wednesday, May 22, 2013 2:07:29 PM UTC-7, David Jasiewicz wrote:

[Dan Newman]

On 22 May 2013 , at 10:16 PM, David Jasiewicz wrote:

> So I have some results. It appears my temperature controller is failing.
> I keep cranking up the temperature and maxed it out at 260 and I am still
> getting some skipping, but it is almost usable. As the print goes on, it
> gets worse. I can only for PLA, because it will not get hot enough for
> ABS. Has anyone dealt with fixing this issue?

The thermocouples on the Replicator 1 are loosely attached to the
heater block. Emmett recently mentioned that there's a 40C difference
between the measurements of his two heaters. (Presumably difference in
what they say for the ambient temperature.)

I've seen pictures of peoples Rep 1 heater blocks where you can see
the thermocouple a good 1 to 2 mm away from the heater block: the
heat they are picking up is radiated heat and that conducted through
the retaining screw.

Look at yours. The thermocouples have a bit of Kapton tape to provide
electrical insulation. They are then affixed by being held under the
head of a small bolt screwed into the heater block. Make sure that
the end of each thermocouple is under the bolt head and that the
bolt head is holding that end against the heater block with no gap.
Do not tighten too much as you do not want the end of the thermocouple
to puncture through the Kapton tape and short to the heater block.
(The short will give bad readings.)

Or, it could be that the kapton tape has been punctured and the end of
the thermocouple *is* making electrical contact with the heater block.
That can induce a current into the thermocouple and cause it to read
the wrong temperature.

Dan

[David Jasiewicz]

Thanks. I will have to check for a short. That would make more
since. I would guess it is not a lack of contact with the block, as I
would expect a short to give a low reading, not a high reading.

[Dan Newman]

On 23 May 2013 , at 2:33 AM, David Jasiewicz wrote:

> Thanks. I will have to check for a short. That would make more
> since. I would guess it is not a lack of contact with the block, as I
> would expect a short to give a low reading, not a high reading.

thermocouples generate a small microcurrent which is proportional
to the temperature. When they are in electrical contact with something
at a different, higher potential, that contact will add to the measured
current in the thermocouple. That then throws the reading off. And,
the difference in potential does not need to be much -- with t/c's we're
measuring very small currents. And the extruder tends to build up
a slight static charge -- all that plastic moving through it and the
head moving around back and forth over another plane at a potentially
different potential.

Dan