Mk7 vs Mk8 Nozzle

[Scott Goldthwaite]

I read a post (https://groups.google.com/d/msg/makerbot/7gt6YOTdDCw/oYT5H3ykejQJ) from Jay where he recommnds using Mk7 nozzle on the Rep 2.  What's the difference between these 2 nozzles?

 

[Jetguy]

The bigger question, where are you going to find a MK7 nozzle?

Only the older bots had them, they were only made by MakerBot and are out of production.

Jay is referring to aftermarket nozzles and nothing wrong with that, I just caution you guys on getting confused with naming conventions.

 

In other words, sure, a link to those aftermarket nozzles may call them MK7s and they might be based on the released CAD design. However, with many f these small parts, design VS manufacturing is a totally different subject. To machine something that small, we use drill bits and tools to approximate the shape. Tiny variations in how it's machined and final finishing steps are likely to vary quite a bit. Not entirely diiferent than 2 folks printing out the same STL from thingiverse. The blueprint was the same, but the users may have chosen entirely different settings and so on.

 

So let's be clear, Jay is saying those nozzles worked great and that fine and they may be called MK7. But, the real MK7 (this is a MakerBot forum) was only sold with Mk7 exteuders back in T-O-M days and early original wooden Replicators.

 

To answer your question, we honestly have no idea what is different geometry or finish wise. They aren't real MK7s in the sense of being manufactured by or for MakerBot, it just means in general they follow the MK7 design and even that is a rough assumption. It could be they have some extra machining or smoothing step inside. Without sophisticated measuring equipment, we are highly unlikely to know unless the manufacturer (good luck on that) tells us.

 

Again, nothing wrong with linking a nozzle that works, I'm just trying to clarify and educate us on the total situation since I see that that saying MK7 nozzles are better could be take the wrong way. And, the devil is in the microscopic details in the nozzle so MK7 from one place might be a miracle of function and might be the nightmare of function from another company.

[Jay]

Jetguy is right...I'm being slack with my naming conventions...sorry.

What I should say...is the nozzle's I purchased were "MK7" clones or compatible or, for car guys, "Tribute Editions"....basically....we don't know to what standard they were made....

I do know that since I switched to these 'generic' nozzle I've had no clogs that required the removal of the nozzle to clear. I have a 1.5mm long T-handle hex key beside the machine. Any time I get to a point where it won't feed...I back out the filament...insert the hex key...and using it like the plunger on a syringe...squirt the clot out. Sometimes the clot is from crappy filament (learning there), or from too high a temp cooking the PLA (learning there) or from bad .stl geometry (some prints just won't print)...

For example...if you look at the posts I printed Nylon, PET, PLA, and Sandstone PLA yesterday...I'd done that before with my OEM nozzle and it would clog hard any time I switched material AND switched temperatures...especially your 'filled' filaments such as laywood or laystone....or because you switched to Nylon and at the higher printing temp any PLA left in the system burned and stuck...NOW...just unload filament, use the plunger, and keep printing...

Do I have an idea why? I think so....Someone (Dan?) pointed out that one of the differences in the 7 vs. 8 is there is a small ledge between the top and bottom of the nozzle. For some reason I think they said it was to keep the filament aligned as it reached the 'melt cup' and it was to form a slight 'pressure' in that cup....at least that's what I took away from the conversation. I'm betting the 'ledge' or 'rim' was left off the Chinese copies. There is a whole scientific discussion about this earlier this year (my eye's glazed over from reading it)...and that was put out by Jetguy (our resident rocket...er...Jet Scientist) :)

Anyway...from now on I'll just call them MK7/8 clone nozzles...

Sorry if I messed anyone up with my choice of wording...

Cheers!!

Jay

[Steve Johnstone]

Hi Jay, do you have a link for the Mk7 clones as I would mind trying them.

Thanks, Steve

[Jay]

Here's a perfect example from just last night...when I got done playing all day yesterday...I did a full 2 minute purge (I think I read somewhere that MBI suggests a 4 minute purge)...then I printed this 7 hour garden frog when I went to bed....As you can see there's TONS of burnt filament that comes out when you wildly shift temperatures and materials. This is true in industrial extrusions also...If I had been using the OEM nozzle it would have clogged. Which means good time spent toothpicking-guitar stringing-propane torching...Now it's not a big problem...

Cheers!!

Jay

[Jay]

Steve,

On Ebay...all chinese suppliers..there's 1 or 2 guys who sell them in 10 piece bundles for $30...they're all listed as "MK8" compatible now...but I bet they're the same nozzle that a few months ago were "MK7" compatible...

Carl also sends nozzles with his T-heater blocks...I'm fairly sure they're clones too...might want to ask him where he gets his in the EU...

Jay

[Steve Johnstone]

LOL Jay... do you print anything small... that's one big frog!

[Jay]

Actually Jetguy and myself have had a discussion off forum about larger and larger prints. To me, that's one of the directions that I feel need to be pursued to make 3D a mature product. Same argument can be made for a printer that can only make smaller but highly defined prints. Technology as it is makes this mutually exclusive (kind of) for now. 

I just like big models too..which would you rather show off? A small but detailed Mr Jaws or a 6 foot long submarine? :)

Oh....and working on a 4 foot tall copy of Big Ben with working clock and chimes now...but it'll be after Christmas before I can really dig into that... :)

Jay

[Jay]

When we can print something like this....we'll really be cooking with gas...all plastic (Acetal/Delrin) Gypsum slurry pump. Used to make sheetrock filler material...and it's not much bigger than the available build areas we can currently make...

Housing

Interior rotor/stator for slurry mixing

Cheers!

Jay

[Ken Hecker]

I'm up for that.  Should only take about 40 hours.  Can we use 10% Infill?  Need David's 3in1 upgrade for that.  :)

Actually if you're not an impatient person, long prints are great (if you can trust the printer to keep going).  Pretty much the first things I printed were two 3" right angle pipe elbows (couldn't find them at the hardware store in that size).  Must have taken 20 hours each.  After three months I finally installed the thing (printed a test of nylon yesterday).  Works like a charm.  Now I know how much in the way of fumes I was pumping into this place.  The ABS exhaust alone is really stinking up outside the greehouse window.  Never did smell it inside.  Probably the ceiling fan.

Ken

[David Clunie]

Could this be rather from outside inclusion rather than inside inclusion?  The reason I ask I noticed the other day while printing with a very dirty "outside" nozzle a piece of black carbon fall away from the brass nozzle into the print also fly away pieces that get caught by the nozzle on the side burn up and then fall off (or are cause up a bit by a 2nd print head not exactly alligned)and then when the nozzle reaches them again it just "includes" them in hot molten plastic.

Just a thought as I saw it first hand but yours seems a bit more "frequent" that the above scenario can account for.

-david c.

[Joseph Chiu]

When I purge between filament types, I usually try to "wiggle/bump" the filament at the tip back and forth a few time, and also do a series of shooooooove / pause / shooooooove / pause.  Then followed by at least a minute of load filament - two minutes is even better.  As long as I maintain that routine, I get a pretty good switch-out and no problems.  I think that process of pausing and bumping helps to grab whatever remnants that are left that doesn't easily get picked up by constantly flowing filament.

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[Dan Newman]

On 26/11/2013, 5:06 PM, Joseph Chiu wrote:
> When I purge between filament types, I usually try to "wiggle/bump" the
> filament at the tip back and forth a few time, and also do a series of
> shooooooove / pause / shooooooove / pause. Then followed by at least a
> minute of load filament - two minutes is even better. As long as I
> maintain that routine, I get a pretty good switch-out and no problems. I
> think that process of pausing and bumping helps to grab whatever remnants
> that are left that doesn't easily get picked up by constantly flowing
> filament.

+1, especially the shove/pause/shove/repeat. I can have the new filament
appear to be extruding just fine with no discoloration from the previous filament.
But then if I simply stop the extruder, wait a second or so, then restart it,
and there's some more discoloration coming out. But that's life with molten
plastic flows.

Dan

[AdanA]

I'll typically load new filament, let it feed a few secomds, then completely unload. The end of the filament will come away surrounded by a glob of residue. I clip that off, reload, repeat.

For some transitions (gray to black, say) I'll do this just a couple of times. For others (black to pretty much anything, for example) I'll do it as many as ten times. Then I let it feed another minute or so.

Note this is all ABS-ABS color swapping, but I imagine the principles are similar when swapping between materials.