Help me get my prusa i3 working... PLEASE!

Jetguy posted a good explanation of the stepped bore thermal barrier and its benifits to PLA. I will grab it when I get a second. It involves using a #42 drill and going in 10mm. It is the original MBI part, before all this PTFE liner nonsence. I may squirt some PET tonight, as it has been giving me some hassles. ABS is printing like a dream.

If you need anything printed, PM me the STL and I will drop it in the mail.

 

"jetguy"
The stepped bore controls the melt pool and helps shear off the melt pool during a retract to prevent molten PLA from seizing to a cold wall in the upper portion.

Yes, E3D V6 works, does it work as well as a genuine Mk7/MK8 MakerBot OEM part?

Also, a bit of history lesson here, MakerBot MK7 has always looked suspiciously like the original UP! design and came out in that time era.
From MakerBot's own 2X and 5th gen Fiasco, whoever designed the original MK7 obviously left the company or forgot everything they ever knew about hot end design.
To me, that says they straight of copied a proven design from someone else and did so at a detail that got it "right". Face it, 3D Systems and Stratasys spent years and years making $100k machines and patented the heck out of extruder tech.
They got the finest engineers on the planet to work this stuff out. If MakerBot copied it, then it all makes sense, they copied a PROVEN design for a reason.

"jetguy" in a discussion of extruder options for my current build

Not in any way trying to knock E3D but they are just building on proven sharp thermal transition and heastinking of the thermal barrier that has been around since the first MakerBot MK7.

I'm glad to see a company understands the thermal principals and the key elements of the design we've been saying for years is the right way to build them.

So Yes, I think both the Chimera and Cyclops are an extension of the Kracken but in air cooled versions.
They appear to use the exact same thermal barrier and as Kracken.

Now I'm not running out and buying E3D ones because I can build the same thing for a lot cheaper from here http://store.quintessentialuniversalbuildingdevice.com/product.php?id_product=11
The MAGIC is, don't use the stock drive gear, modify the thermal barrier by drilling it out to match MakerBot specs, and that $34 in parts becomes a bulletproof extruder without a ton of work or money.

One you know what needs done, it's a 5 minute job.

Thermal barrier is not stepped internally. This is a simple thing to add, all other dimensions are dead on correct. This step in the bore allows PLA to expand through the thermal transition zone( aka heat break) but the step also controls melt pool on a retraction.

The fix: drill the hot side(short threaded side) with a number 42 drill bit ( index numbered drill set) for a depth of exactly 10mm. That lands the step just as the necked thin wall section switches back to threads. Again, placement and size is critical, but not even hard to do. I can do them by hand on a cordless drill using a stop collar on the drill bit. Just need that index drill set to have the exact size bit.

 

With all that being said, I think you are on the right track with the heat sinks. Going back and reading this maybe has given me a little more understanding of the E3d hot end. By using the heatsinks, with active cooling fans, it essentially creates a longer cold zone to cap the meltpool. I dont think you had mentioned if your direct drive thermal barrier was threaded or set screw mounted? When I was on my parts ordering spree for the new bot I ordered like 6 threaded thermal barrier to to try and drill. Funny, one came with a ptfe liner, the inlets and lengths were different from the two sources, so I should have some nice comparisons. I do have a set of stepped bore thermal barriers from Carl, I pulled one from my dual to install in my coreXY.

 

I figured I would break one or two, and got five. I didnt see, or it wasn't offered, but I would have got 12 for the free shipping

Dnewman ( sailfish co-author ) has been experinmenting with the E3d heaterblock, and nozzle, on the MBI threaded barrier, mounted to carl's thick aluminum bar. I have orded a few to play with.

 

I have been really in the hot end rabbit hole. Some more quoting of Jetguy.


>You guys are endlessly chasing down a nozzle problem when the jam is ALWAYS in the thermal barrier tube.
Yes.
And why it is in the thermal barrier area instead of the nozzle area?

The original poster here actually had that problem a blockage NOT in the nozzle area but much higher up in the thermal break area of the nozzle.
Here's how to find that out.
Say you have an extruder jam and you find out that you can no longer even feed filament into it manually while you know that it is preheated to the melting temp of the material (195-200C for PLA or 210-230C for ABS).
You let the nozzle and heater block cool to room temp and carefully remove the nozzle. If you are very careful and do this correctly, you'll pull out a molded filament shape like this.

Some notes about this any why it is extremely important to the discussion: This is an original QU-BD MBE9 thermal barrier tube that is a straight through bore of ~1.9mm with NO step at the heater block side.
The current Flash Forge PTFE tube creates the exact same problem.
Now, before you haul off and jump to conclusions saying all that proves is there was plastic all the way to the nozzle check this out:
The same end snapped off revealing the entire section in the nozzle was hollow!!!

Now, this next picture is the "money shot"


The location of the jam in the thermal barrier tube is shown by the allen key beside it. It is impossible to push this jam out by mechanical force in this state. The jam is ONLY about 5mm long but is solidly bonded to the thermal abrrier tube walls.
In fact, extensive testing and comparison with others in the QU-BD forums show they too experienced jams in the exact same location. Swapping a different nozzle will not clear this jam.

Again, there are some key indicators here. Air is compressable, liquid is not. If the jam was in the nozzle tip, then you would expect to find no trapped air or hollow space because the rest of the filament further up could have easily pushed down on the air pocket. Instead, we can determine that the jam happened after a retraction. The molten filament was pulled up from the nozzle area into the cooler heat break and jammed against the walls. Because this area is not hot enough to keep the filament molten, the jam prevents any further filament from feeding. The EXACT same type of jam is happening in the PTFE tubes for folks.

What is KNOWN is that the genuine MK7/MK8 thermal barrier tube system NEVER does this. The facts before us are simple. Both designs that jam use a single smooth bore system all the way to the nozzle of only about 1.9mm diameter.
The systems that do not jam are #42 size (2.3813mm) bore in the hot zone. This is easy to see what the hot zone is by examining the heater block

Common sense, if the heater block is 230C(or whatever your set temp is) then the parts directly threaded into it are the same or nearly the same temp within probably 10 degrees.

Let's examine a lineup of thermal barrier tubes.
The upper left is a genuine MK7/MK8 MakerBot OEM thermal barrier. The next one down is a QU-BD one modified by drilling with a #42 drill bit for 10mm to exactly match the MK7/8 one. The next is an all orginal untouched QU-BD with the stright 1.9mm bore. The last bottom one is the current Flash Forge with the PTFE removed. If you look closely, you can see the stepped bore in the MBI one and the modded QU-BD one whihc perfectly. The original QU-BD one jams like mad but I ket 1 of mine stock just for reference.
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JC, how are things going with your bot? I was having the same issues as you with PET, new piece of glass is what ended up fixing my problems