Leaky Extruder on Replicator 2

[Bill]

I did submit this to MBI support, but, I thought I'd check with the group to get thoughts.  Being that I didn't build the Rep2, I haven't taken it apart yet, and I don't even know what I'll see since I didn't build it.  

Anyway, it seems like the Kapton tape that wraps the extruder block is saturated with plastic, and the nozzle itself seems to be properly tight.  

Thoughts?  Cross-threaded nozzle during (their) assembly?

What to do?

Pic attached.

Bill

[Jetguy]

Insanely simple.

 

First understand how it's assembled by looking at Mk7/8 instructions. Both the nozzle and the thermal barrier stainless threded tube screw into the heater blcok. If they don't touch and seat internally to each other (the nozzle and the tube), then they will ALWAYS leak.

 

Basically, you could bottom out the nozzle against the block, but still fail to ensure the threaded tube is tight against the nozzle inside the block. Because the motor mount block is also threaded and tightened with a nut, you need to loosen the nut so the tube can be turned while keeping the heater block in a certain orientation to the entire asembly.

 

Now for the PITA part. Because you already have  this leak and have PLA in the threads, everything must be at the melting point or higher of PLA in order to move anything and fix this.

 

Best of luck. http://www.makerbot.com/support/replicator/troubleshooting/nozzle-swap/ 

[Bill]

Ah.  I see said the blind man, etc.

Thank for the link and the advice.  Unfortunately for me...I discovered this 3 hours into what's probably a 10 hour build.  Ugh.  

I'll keep my eye on it for the rest of this build and then tear it down.  

How important is that white ceramic tape? It looks pretty trashed.

Bill

[Jetguy]

In theory, on a Replicator 2, it might be a bigger deal because of the
secondary cooling flow from the PLA cooling blower. You must cool the
print to get each layer solid before the next layer is printed---hence
the need for the additional cooling fan. The problem is, it then blows
directly on the heater block too. This would keep the heater on more
if not constantly and stress the electronics and power supply more
than normal. Being the heater is only rated at 40 watts and in my
measurements, less than that, the above statement may not be a big
deal but just stating it for completeness and full disclosure of how
the system is affected. I don't think the cooling will be so bad that
the heater cannot maintain temp, but at higher temps, that may be
true. That tiny layer of cermaic tape and the kapton actually are
effective in the case of direct airflow from hitting the heater block.
Personally, I wouldn't run long without it, but you are unlikely to
outright damage anything by attempting to print without it. Heck, it
might work fine, but again, just trying to share the reason why it's
there and how it might affect the system

[whpthomas]

The second fan on the Replicator 2 is ducted, and doesn't appear to blow on the hearing element at all, just around the tip of the nozzle. I guess a bit of air will be cooing the element - bit as you point our it is insulated, most of it just streams across the build plate towards the y stepper motor. The heat sink fan does have a gap where air flow can stream down onto the element, but there are horizontal fins blocking it so only a small amount would be getting through. Not sure how much active cooling of the element itself is actually going on - but the block attached to the heat sink is cool to touch.

[Jetguy]

Yes, that the entire point, the block the heatsink is attached to must
stay cool and even more important is the stainless, hollow, threaded
tube the filament is going into MUST remain below the metling point of
PLA as close as possible to the nozzle. If that tube heats up and
begins to make the PLA soft, then the filament princh wheel system can
reverse soft PLA back into that pinch and stop extruding since it's a
fixed distance between the delrin plunger and the knurled wheel.
Reversal happens a lot during printing to prevent the nozzle dripping
which again too, is worse if there is more length of heated soft
filament in the extruder system. Ideally, the only part we want hot is
the nozzle tip. Unfortunately, without specialized manufacturing (even
more so than we have now) and custom heated nozzles, along with even
more active cooling or specialized materials, it's dificult to create
that perfect temperature gradient, between the nozzle tip, while still
mechanically supporting the filament path, let alone holding the
nozzle against the downward pressure and then the side loads from
printing.

For the above reasons, you can see why upgrading to one of the many
printed filament drives that use a spring and ball bearing as a roller
are effective in fighting changing diamter or hardness of the filament
VS the fixed pinch system that comes stock. The stock system simply
has no tollerance for changes.

Further, based on the explanation above, many folks have looked into
modifying the cooling system to better cool the filament in the pinch
drive area by removing the heatsink altogether which lets even more
airflow downwards. This follows my suggest goals of colling all
filament path as much as humanly possible above the heater block--
hence again, the need for the insulation to prevent the heat from
rising.

So yes, far more complicated than may first appear. Looks are
deceiving.

[whpthomas]

Interesting you should say this, I just upgraded my heat sink fan to a much quieter and more powerful ball bearing fan - still rated at 24v, but with a greater air flow and less blower noise. My printer seems to be printing WHITE PLA much better than before - which is the one colour I have had the most problems with print failures with.

[Jetguy]

Link to ceramic tape from another source http://ultimachine.com/content/ceramic-insulation-tape
Kapton tape
http://ultimachine.com/category/catalog/electronic-boards-and-kits/electronic-components/miscellaneous-electronics?page=1

Always good to know alternate sources.

[Bill]

I'm a big lover of aircraft (I was going to say Fan), however, having one on my desktop is a tough nut to swallow.  I'm definitely interested in a quieter fan so it doesn't sound like a jet taking off all day. 

What fan did you use/suggest?

Bill

[whpthomas]

Bill: my Rep 2 is still a bit noisy, there is still the blower and of course the stepper motors singing, but I still think the heatsink fan was the loudest. I just went into a local electronics store, enquired about getting a 24v ball bearing fan 40 x 40 x 10 mm. They didn't have any in stock, but were able to order one for me. It has a lower RPM but higher CFM rating so is quieter. All the writing on it - logo wise is in Chinese, so I can't tell you what brand it is, bu I am sure you could pick something like this up on ebay or maybe from Digikey if you live in the US. 

[Bill]

I pulled out the card I've been using to level my R2 and called the number on the front.  Jason answered quickly, listened to my issue, asked me to email him a pic along with the description.  I said I already did.  He pulled up the info and said he'd get back to me by COB.  He did.  He said that they'll ship me a replacement nozzle/heater block/tube/cross bar assembly around Monday. 

I'd say that's pretty decent service.  It would be nice if they were quicker on the emails, but, they're working on it.  I have to swap in the new assembly, but, that's really no big deal.

Just thought I'd pass on the experience.  Besides the wait, MBI has been pretty good to me.

Bill

[Gary Crowell]

Here are three Orion fans to choose from.  I used the 6CFM one; dunno if either of the others would be better or worse.  All are about $10.  The stock numbers are Digi-Key.

OD4010-24LB .. 1053-1211-ND .. 4200 RPM .. 5.0 CFM
OD4010-24MB .. 1053-1212-ND .. 4800 RPM .. 6.0 CFM

OD4010-24HB .. 1053-1208-ND .. 6000 RPM .. 7.0 CFM 

Note that the mounting holes on these are not countersunk to fit the socket head screws.  You'll either need different screws, or countersink the holes yourself.  I drilled out the holes, very carefully, with a step drill on a drill press.  The results were perfect, but it would be easy to mess up.  Details here: http://www.thingiverse.com/thing:33779  and here: http://www.thingiverse.com/image:199296

Gary

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Gary A. Crowell Sr., P.E., CID+

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